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2001A Program Abstracts |
Abstracts for all successful 2001A classical and queue programs are given below.
Title: Typical AGN host galaxies at the epoch of galaxy formation
Abstract: We propose to use the ultra-high resolution offered by Gemini to image the host galaxies of typical, L* luminosity, AGN at z~2. Our aim is to search for evolution in the luminosity and morphology of the host galaxies. In particular, we wish to answer the following question: is there a direct relation between AGN and star formation? That is, are the host galaxies of typical high redshift AGN also the hosts of massive starbursts? L* AGN are too faint to be used as AO guide stars. Our approach is unique in that we have selected our targets from the 2dF QSO Redshift Survey (2QZ), the only survey large enough to provide sufficient numbers of ~L* AGN which have nearby bright stars suitable for AO use. This approach offers the crucial advantage of avoiding the redshift-luminosity degeneracy that would otherwise compromise the search for evolutionary effects.
Title: Mid-infrared spectra of Parkes Quasars
Abstract: The mid-infrared (MIR) wavelength region is crucial to understanding the dominant emission processes in radio-loud quasars. The MIR spectra of Parkes Quasars is expected to be dominated by either non-thermal synchrotron emission (which is seen at optical wavelengths), or thermal emission from hot dust. We are requesting half a night's observations with OSCIR to obtain MIR spectroscopy of 6 flat-spectrum radio quasars, as part of our on-going study of the Parkes Half-Jansky Flat-spectrum Sample. We wish to use these spectra to determine the nature of the MIR continuum, primarily by examining the spectral slope and comparing with non-thermal and thermal predictions, and also by examining emission lines, should these be visible above the continuum.
Title: The Extended Star Formation Histories of the M81 Group dwarf Ellipticals F8D1 and BK 5N
Abstract: We propose to use NIRI to image in the J and K bands the dwarf elliptical (dE) galaxies F8D1 and BK 5N. These dwarfs are members of the M81 group, one of the nearest groups beyond the Local Group. Our HST/WFPC2 study (in the V and I bands; Caldwell et al., 1998, AJ, 115, 535) has revealed the presence of significant numbers of stars above the tip of the red giant branch in both galaxies, an indication of the presence of an intermediate-age (~2 < age < ~10 Gyr) population. Near-IR band photometry is required, however, to determine bolometric magnitudes for these upper-AGB stars, and thus provide improved estimates of their ages. Our results will provide information on the extended epochs of star formation in these dwarf ellipticals which will be directly comparable to existing information for Local Group dEs, such as the dwarf spheroidal companions to the Galaxy and to M31. In this way we will add to the understanding of the factors, including environment, that govern the star formation history in these allegedly simple galaxies.
Title: Mass Segregation in the Globular Cluster M4 (NGC 6121)
Abstract: We propose to use NIRI to image the globular cluster M4 at two radial locations in order to investigate the effects of mass segregation in this cluster. The first location is at the radius where mass segregation effects are likely to be strongest while the second (inner) field not only provides a comparison for the first, but will also allow us to tie these observations to existing HST data. Observations of background regions are also required to remove the field star contribution. Our results will constrain the dynamical evolution of the cluster and the rate of evaporation into the accreted halo of the lowest mass stars formed in the Galaxy's initial burst of star formation.
Title: Imaging the stellar hosts of microJansky radio sources
Abstract: Among the most controversial problems in studies of the evolution of galaxies are the effects of dust obscuration on the selection and interpretation of star-forming galaxies at intermediate redshifts. The UV light from such galaxies is dominated by the least-obscured star-forming regions, while increasingly longer wavelengths (Halpha/far-IR/radio) are dominated by increasingly more obscured components. It is therefore not surprising that recent far-IR and sub-mm surveys have revealed that the most vigorous sites of star formation are obscured by dust. This poses very serious problems to in any attempt to infer the history of star formation from observations made at UV or optical wavelengths. To address this problem we propose to use high angular resolution K-band NIRI imaging of radio-selected star-forming galaxies to carry out the first-ever study of the mass assembly rate in obscured galaxies with high star-formation rates at intermediate redshifts. This study is of fundamental importance as it is likely that many, and perhaps all, large galaxies will have passed through this phase during some stage of their formation.
Title: The Faintest Parkes Flat Spectrum Sources
Abstract: We wish to detect the powerful radio source PKS 2047+098 in the near-IR with NIRI. For many years so, we have been trying to identify the 323 sources in the Parkes Half Jansky Flat Radio Spectrum sample. Using deep optical and near-IR imaging, we've now detected all but two of the sources. PKS 2047+098 is one of those two. It is an extremely powerful radio source with an inverted radio spectrum and a compact VLBI core. Despite that, it is not detected to B=25.4, R=23 and H=19.7. PKS2047+098 is probably either a z>5 quasar or a z>3 radio galaxy: anything else would have already been detected. If it is a galaxy, it will be the first high redshift radio galaxy with such an inverted radio spectrum and may tell us a lot about jet/cloud interactions and the alignment effect. Determining whether it is a quasar will allow us to use our complete radio selected quasar survey to probe the turn-down of the bright quasar luminosity function above redshift four.
Title: 10 Micron Imaging of X-Ray Sources in a Deep Chandra Field
Abstract: Deep Chandra observations have revealed the X-ray sources that make up most of the X-ray background. This is a tremendous advance, but in order to interpret what this means in the broader picture of the formation and evolution of AGN and galaxies, we must follow-up the X-ray background sources at other wavelengths. We have already undertaken deep optical and near-infrared imaging of one deep Chandra field. Here we propose to use OSCIR on Gemini to obtain 10 micron images of the optical counterparts for the K K< 19 sources in that field. Our goal is to test the hypotheses that the Chandra sources are either highly obscured AGN or AGN associated with strong starbursts. 10 microns is sufficiently far in wavelength that the infrared excess associated with an obscured AGN or starburst will be detectable in these objects.
Title: Dust in Halo and Galactic Bulge Planetary Nebulae
Abstract: The dust grain compositions in Planetary Nebulae as traced by mid-IR spectroscopy have revealed dramatic differences between the C/O chemical balance of Galactic bulge and local disk PNe. This suggests different progenitor populations and may indicate a link between halo (type IV) and bulge PNe. This is perhaps one of the first indications that the physical properties of different PN populations reflect the variations in galactic environments, a result which is particularly important in view of the widespread use of the PN luminosity function as an extragalactic distance indicator, independent of Hubble type. One of the most surprising results from the small sample of objects that we have measured towards the Galactic bulge is the detection of silicate emission from M 2-29, one of the most metal poor PNe known. We propose to use the sensitivity of OSCIR on Gemini to extend our initial results on the C/O chemical balance of galactic bulge PNe to a sample of 20 bulge members, and the accessible halo PNe detected by IRAS. This will enable us to probe dust formation at the tip of the AGB in metal-poor environments and compare it to the local disk.
Title: The star formation history of the bulge
Abstract: This is a joint Chile-Argentina proposal to obtain sharp J, H and K-band images of two selected fields in the Milky Way bulge in order to constrain 1) the old stellar population of the Galaxy, 2) the faint end of the mass and luminosity functions, and 3) the evolution of the star formation rate in the bulge. We aim for photometry of point sources down to K=24 with sigma_K ~ 5%, which combined with existing deep HST optical images, will make the deepest views of the Galactic bulge: - the deepest color-magnitude diagrams, - the deepest luminosity functions, and - the sharpest images. Combining the IR photometry with the HST data we will determine not only the age (and possible age range) of this component of the Galaxy, but also its mass function down to 0.05 M_sun, essential to understand the possible MACHO population towards the bulge.
Title: The stellar masses of compact galaxies in the HDF-N and flanking fields
Abstract: Recent studies of field galaxies to z ~ 1 indicate that a population of small blue galaxies with small masses are responsible for the largest changes in the luminosity function and star formation rate density in the interval 0 < z < 1 (e.g., Lilly et al. 1998, Guzman et al. 1997, 1998, Phillips et al. 1998, Mallen-Ornelas et al. 1999). However, it has been questioned whether these small blue galaxies have an underlying old stellar population, and whether there may be a bias in their dynamical mass measurements. To address this question, we propose to conduct near IR observations (to K~21.2) of compact galaxies in the HDF-N flanking fields, with measured velocity widths by Phillips et al. (1997) and Guzman et al. (1997). K-band photometry will be used to infer the stellar masses of distant galaxies, and determine whether these galaxies are young and have small stellar masses, or if instead we are observing only a recent bright burst in a more massive galaxy with an old stellar population.
Title: Homogeneity of Cluster Elliptical Galaxies at z~1
Abstract: We propose to use GEMINI+NIRI to obtain deep JK imaging in the central regions of 2 z~1 galaxy clusters, taken from the Red-sequence Cluster Survey. These data will be used to constrain the homogeneity in the integrated optical-IR colours of the cluster ellipticals, within each cluster and among the different clusters. These data will be combined with already existing optical photometry and with higher redshift photometry (to construct the optical-NIR colour evolution vector) and used to constrain the predictions of popular simple stellar population (SSP) models, particularly in the NIR. Quantitative morphology will allow us to segregate the elliptical population and to study their size distributions. This proposal is part of a larger program between Chilean and Canadian astronomers in the framework of the RCS collaboration. Here we are proposing for the observations of 2 clusters of a total sample of 5 (observations for 3 will be asked to the Canadian TAC).
Title: A deep L-band field: stars and QSO hosts at redshift ~ 5
Abstract: We propose to obtain a very deep L-band field with NIRI on Gemini, targetting the lensed quasar BRI 0952-0115, at z=4.43. By making it possible to probe the redshifted optical region close to the H_alpha emission line, the data will complement our VLT B,R,I observations and the public HST/NICMOS H-band images, allowing both to measure the clustering of proto-galaxies at this redshift and to estimate their SFR. The QSO is lensed, as is its host galaxy. By deconvolving the images, we will be able to study in detail a QSO host galaxy at redshift close to 5, to observe its stellar light (present proposal) as well as the ionized gas light (our B-band observations). Lensing will also boost the signal from any companion to the QSO, allowing us to go even deeper. Finally, we are following the photometric variations of the QSO at the ESO 3.5m NTT in order to measure its time delay and consequently H0. Identifying all massive objects up to z=4.43 is therefore another important goal of the present program.
Title: Imaging of Low Redshift QSO Damped Lyman-alpha Absorption Line Systems
Abstract: We propose to obtain deep K' images of a sample of the lowest known redshift (z<=0.5) damped Lyman alpha (DLA) quasar absorption line systems to establish whether low-surface brightness galaxies or dwarf galaxies give rise to the absorption. These images will be some of the deepest and highest resolution images ever obtained of any damped Lyman-alpha absorber. With this data set we will (1) probe fainter than previous searches, constraining whether low-surface brightness galaxies can give rise to DLAs, (2) probe closer to the quasar looking for previously undetected small compact galaxies, (3) study the near-IR morphologies of candidate absorbers, and (4) in cases where an absorber has been tentatively identified at optical wavelengths, add the near-IR photometry to better constrain the galaxy type and redshift of the candidate absorber. This proposal is a continuation of an observing program begun during the Gemini QuickStart Service period. Preliminary analysis of data obtained during the QuickStart of the field surrounding Q2251+1120 reveals a faint (K~20) object close to the quasar line of sight. If this object is at the redshift of the absorber then this object would have an absolute magnitude similar to a faint dwarf galaxy or the bulge of a low-surface brightness galaxy. This project will illustrate the potential for Gemini to reach faint limiting surface brightnesses and to probe close, in projection, to the quasar for candidate absorbers.
Title: Evolutionary Diagnostics of Local Group Dwarf Galaxies in the Infra-Red I.
Abstract: A complete model of galaxy evolution must fit not only giant galaxies, but also dwarfs. For example, in hierarchical merging models of galaxy formation, dwarf-like objects form first; present-day dwarf populations should include remnants of the first phases of galaxy formation. Dwarf galaxies similarly test the importance of key astrophysical processes, such as starbursts and gas outflows. These features, as well as possible evolutionary links between nearby dwarfs and large populations of faint blue galaxies seen at lookback times of 3-5Gyr, have led to well-focused explorations of stellar populations and evolutionary histories of nearby dwarfs. Now, in the era of excellent IR detectors on 8m class telescopes. it has become possible for studies of faint resolved stellar populations to begin in earnest in the infrared. This will bring significant advances in our understanding of the properties of the older stellar populations and how they form in the nearby Universe as we can look into the regime where they emit most of their luminosity. This proposal requests use of Gemini North to investigate nearby dwarf irregulars with unusual evolutionary histories by photometering evolved stellar populations with ages of 0.5-10Gyr in the IR, which will provide a valuable complement on the same spatial scale as our (optical) HST images for the same galaxies.
Title: CO abundances in T-type (CH4-dominated) dwarfs
Abstract: T-type or "methane" dwarfs are brown dwarfs whose photospheres are sufficiently cool that almost all carbon is incorporated in methane rather than in carbon monoxide. In chemical equilibrium the fraction of carbon in CH4 would be virtually 100 percent in the photospheres of objects as cool as the prototypical T dwarf, Gliese 229B. However, M-band spectra of Gl 229B, show a much larger (although inaccurately known) abundance of CO than predicted for chemical equilibrium. The reason for this difference is unknown, but it is suspected that upwelling of gas from deeper hotter layers, where CO is more abundant, is responsible for the enhanced CO abundance. We propose to obtain L and M band spectra of four additional T-type dwarfs covering a range of effective temperatures, including three which are not companions, to begin to explore whether overabundances of CO and corresponding reductions of CH4 are a common phenomenon. The results will begin to reveal similarities, differences, and patterns in T dwarf atmospheric structure, activity, and evolution and could also have important implications for abundances in giant planets and their stellar primaries.
Title: The nature of galaxies in the HDF-N
Abstract: We propose to image the Hubble Deep Field North (HDF-N) to identify high redshift galaxy candidates, to search for extremely red objects (EROs), and to secure photometric redshifts at magnitudes fainter than spectroscopic limits permit (K <~22). We will image the HDF with NIRI in the K'-band down to a 5-sigma limiting magnitude of K=23.5. The 2'x2' field-of-view of the f/6 camera in NIRI allows us to observe most of the HDF-N (60%) in K' at sub-arcsec angular resolutions (0.45arcsec routinely), an observation that has not been done before. Under the best image quality conditions (0.3arcsec FWHM), we will be able to measure structural parameters (intensity profiles, metric radii, and incidence of bars) and compare them to the optical. Together these data will allow us to address the following questions. 1) What is the density of high redshift galaxies and EROs in the HDF-N? 2) How different are the morphologies of the HDF-N galaxies in the near-infrared compared to the optical. A great asset of the proposed observations is the addition of the deep K'-band images to the full complement of the UBVI HST images and ground based spectroscopic redshifts. Imaging galaxies at 2.2microns, where most of the contribution to the light originates from older stellar populations, will allow us to study the distribution of the dynamical mass. This is an important difference to the optical which samples light dominated by short-lived massive stars which evolve on much shorter time-scales than the dynamical time scales of galaxies. Combining the optical and near-infrared observations will allow us to construct a coherent picture of the nature of galaxies out to z~2.
Title: Testing stellar interiors & atmospheres at [Fe/H]=+0.4: Observations of faint main sequence stars in NGC 6791
Abstract: The populous open cluster NGC 6791 is approximately 8 Gyr old, yet substantially richer in heavy elements than the Sun ([Fe/H]=+0.4). These rare properties make NGC 6791 a critical local template population for chemical enrichment studies and for the spectral and photometric dating of galactic bulges and elliptical galaxies. While NGC 6791 has enjoyed considerable attention, its distance (m-M=13.4, 4.8 kpc) has precluded observations of main sequence stars below 0.7 solar masses. With a few hours of observations with Gemini/NIRI we can measure the main sequence in NGC 6791 down to 0.2 solar mass stars in the colors which are most sensitive to cool main sequence stars and least sensitive to the line-of-sight absorption (Av=0.66). Comparison of the proposed observations with stellar models will allow us to increase the precision in the cluster Helium abundance by a factor of two and measure for the first time the colors of low mass metal-rich stars. We will also probe the dynamical state and IMF of this key cluster.
Title: Adaptive optics survey for young Jovian -mass planets
Abstract: We propose to conduct an imaging survey for Jovian-mass planets around young solar-type stars in nearby star-forming regions.
Title: Adaptive optics survey of M stars closer than 5 pc
Abstract: Adaptive optics will be used for a search for new companions, possibly sub-stellar mass objects, around nearby stars. Our observations will complement observations of Jean-Luc Beuzit. Partial observations have already been made at the CFHT in July 98 with Hokupa'a, and since November 98 with Pue'o. By combining exposures as deep as 30-min we were able to obtain images with a dynamic range of $10^6$. This will enable us to detect companions as faint as $m_J = 21$ at a distance of only 10 AU from a 5 pc M stars. According to Burrows et al. (1997), this is the brightness of a 5 Gyear old gaseous planet with only 7 Jupiter masses. First observations have been taken last year and these observations are needed to discriminate companions from background stars, taking profit of the fast proper motion of the central star.
Title: Search and Follow-up of Ultracool Binary Systems
Abstract: We propose to search for binaries among ultracool dwarfs (spectral type later than M7). The scientific goals are the following: (1) to cover a wide range of separations in order to check the tantalizing results obtained by Mart\'\i n et al. (2000), which indicate that very low-mass mass binaries could have a different distribution of orbital periods than solar-type binaries; (2) to prepare a sample of ultracool short period binaries for which dynamical masses can be derived with the future Keck interferometer; (3) to derive fundamental parameters (effective temperatures, gravities, and projected rotational velocity). We will combine optical spectra with near-infrared spectra to make a state-of-the-art analysis of the atmospheres of ultracool dwarfs.
Title: Disks Around Stars
Abstract: Stars form from dusty accretion disks which dissipate on timescales of 10 million years or less. Some main sequence stars retain dust disks probably replenished by collisional grinding among unseen parent bodies in extrasolar Kuiper Belts. We propose to study selected nearby stars in search of replenished circumstellar dust structures.
Title: The IMF of the Arches cluster
Abstract: The Arches cluster near the Galactic Center is known to be the most massive and densest young stellar cluster in the Galaxy. It contains at least 1e4 Msun in stars, with a half-light radius of 0.2pc, and approximately 160 O-stars. Its position near the Galactic Center, relative youth, and compact nature make it ideal for studying the IMF in a region with extraordinary environmental parameters in regards to star formation. i.e. large tidal shear, high turbulent gas velocities in molecular clouds, high (perhaps) metallicity, and a strong magnetic field. The measured IMF is tied for the flattest ever measured for a young Galactic cluster in that mass range. We propose to repeat this measurement using AO imaging with QUIRC and Hokupa'a.
Title: The Eccentricity of Charon's Orbit
Abstract: We propose to use Hokupa'a to obtain high resolution images of the Pluto-Charon system with the goal being to measure and either confirm or refute the non-zero eccentricity indicated by HST observations made when the orbit was viewed more edge-on.
Title: The 'Baade Experiment' on dwarf galaxies in the Virgo cluster
Abstract: There is the remarkable possibility that Population II stars can be resolved in the Virgo Cluster from observations at Mauna Kea. Stars at the tip of the red giant branch have $M_K=-6$. At $(m-M)_{virgo}=31$ these stars will appear at $K\sim25$. Stars at this magnitude in uncrowded fields should be detectable with Hokupa'a on Gemini Telescope with integrations of 2.5 hours. The capability to detect Pop~II stars in the Virgo Cluster will ultimately give a precision distance to the cluster and allow a quantitative determination of the faintest galaxy constituents of the cluster. The present observations have the more modest goal of testing the feasibility of such measurements.
Title: Typical AGN host galaxies at the epoch of galaxy formation
Abstract: We propose to use the ultra-high resolution offered by Gemini to image the host galaxies of typical, L* luminosity, AGN at z~2. Our aim is to search for evolution in the luminosity and morphology of the host galaxies. In particular, we wish to answer the following question: is there a direct relation between AGN and star formation? That is, are the host galaxies of typical high redshift AGN also the hosts of massive starbursts? L* AGN are too faint to be used as AO guide stars. Our approach is unique in that we have selected our targets from the 2dF QSO Redshift Survey (2QZ), the only survey large enough to provide sufficient numbers of ~L* AGN which have nearby bright stars suitable for AO use. This approach offers the crucial advantage of avoiding the redshift-luminosity degeneracy that would otherwise compromise the search for evolutionary effects.
Title: Dust formation by recent supernovae
Abstract: We propose to use OSCIR in its direct imaging mode to carry out the first mid-IR survey for thermal dust emission from recent extragalactic SNe, in order to directly test for the first time the widespread assumption that supernovae are major sources of dust in the Universe. We aim to observe about 20 nearby SNe that have been discovered during the past three years (from a target list of more than 40 suitable candidates). Deep images will be obtained using the broad 10-um filter, since a variety of evidence has shown that this is the optimum wavelength to search for the dust that is predicted to form within 1-3 years of outburst. For sources that are sufficiently above the 10-um detection threshold, images with the 8.8- and 18-um filters will also be obtained, to enable dust colour temperatures and characteristic emitting masses to be estimated.
Title: Imaging Superwind Shells in Proto-Planetary Nebulae at 7.9 to 18.2 microns
Abstract: In a NIR polarimetry survey at UKIRT we have detected extended circumstellar envelopes (CSEs) around 15 Proto-planetary Nebulae (PPNe). All CSEs show evidence for axisymmetric outflow suggesting that this is a common trait of PPNe which originates earlier in the superwind phase that terminates the AGB. This final enhanced mass outflow phase is very poorly understood at the moment. We propose to directly image these superwind shells in 4 MIR filters with OSCIR, which on GEMINI provides a pixel scale allowing direct comparison with our UKIRT NIR data. By combining the MIR imaging with our NIR polarimetry, we will produce detailed models of the CSEs of PPNe and of mass loss on the AGB. This is an updated resubmission of Quick Start proposal 13 which was allocated time in SRB3, but can no longer be observed in 00B.
Title: Cosmology with High-Redshift Type Ia Supernovae
Abstract: We now have the opportunity to obtain a Hubble diagram of Type Ia supernovae (SNeIa) that will be of longlasting value as a record of the expansion history of the universe. This record, based on SNeIa used as calibrated standard candles, directly constrains the cosmological parameters. NIRI on Gemini is capable of providing crucial near-IR data (rest-frame V band) for the highest redshift supernovae. Combined with coordinated optical observations at other observatories, in particular HST, these will provide powerful constraints on SNIa evolution and abnormal dust within or between galaxies. Accurate measurement of these high redshift SNe will dramatically shrink the major-axis of the error ellipse in the Omega_M--Lambda plane, decoupling the measurements of Omega_M and Omega_Lambda. This will provide the first check on the CMB measurements of a spatially flat universe, and unambiguously determine whether the universe contains vacuum energy. The Hubble diagram in this redshift range is the only currently feasible way to begin constraining the physics of the ``dark energy'' that is accelerating the universe's expansion.
Title: The Galactic Environments of Gamma-Ray Bursts
Abstract: Understanding of GRBs has improved greatly since the first detection of afterglows in other wavebands. However, the nature of the progenitors of these most powerful of explosions, remains an enigma. Vital clues may be obtained from studies of the GRB host galaxies, in particular from the position of the GRB in relation to the different stellar populations present. Most of the known host galaxies are compact and faint, so deep, high-resolution imaging is required. We have an ongoing program of deep HST STIS imaging of a sample of host galaxies aimed at ascertaining their morphologies. Here request complementary deep Gemini QUIRC imaging of a subset of our HST targets, to aid classification of the host galaxies, and in particular to distinguish the positions of the GRBs in relation to regions of old and young stellar populations.
Title: Gemini NIRI imaging of optically faint Chandra sources
Abstract: We are conducting a deep survey with Chandra and XMM to resolve and study the sources which produce the cosmic X-ray background. Confirming the discovery of the GTO surveys, we find that approximately 50% of the hard X-ray sources are associated with the nuclei of bright early-type galaxies. These are almost certainly hosting hidden AGN, in some cases with quasar luminosities. Potentially the most interesting, however, are the elusive 10% of X-ray sources which have no optical ID to very faint magnitudes R=26. The hard X-ray spectra and high X-ray to optical ratios suggest highly reddened AGN. The optical non-detection of even a host galaxy can be explained if these reside in high redshift (z>1) elliptical galaxies, analogous to those seen locally. We propose deep J, H, K-band imaging, sufficient to detect (and resolve) these host galaxies to z=2, with colours providing the first reliable redshift estimates for these remarkable faint sources.
Title: The dust-enshrouded formation of massive elliptical galaxies
Abstract: We propose deep NIRI K-band imaging of the 12 brightest sub-mm sources ($S_{850} >8$mJy) detected in our major SCUBA/JCMT surveys. These sub-mm sources have inferred dust-enshrouded star-formation rates $>1000$ solar masses/yr, as required for the formation of the most massive elliptical galaxies in $\simeq1$ Gyr, and are sufficiently numerous to potentially account for the formation of all present-day massive ($>4L^{\star}$) ellipticals. Determining their nature/redshifts is now of fundamental importance for understanding galaxy/structure formation. Finding unambiguous IDs for these sources requires high-accuracy positions (from IRAM PdB or VLA follow-up already underway) combined with very deep infrared imaging. Our one existing deep (6 hrs with UKIRT) K-band identification has K=21-22, and a complex IR morphology reminscent of radio galaxies at z=3-4, offering a first clue that the high-z formation epoch inferred for radio galaxies may apply to massive spheroids in general. Deep NIRI observations represent a crucial step towards settling this issue.
Title: Sub-mm EROs, photometric redshifts, and the cluster gravitational lens A2218
Abstract: We propose to use NIRI to undertake a high-resolution J/K survey of the core of the massive cluster lens A2218, which has recently been imaged in BVRI with HST, and which we have now surveyed to mJy depths using SCUBA at 850 and 450 microns. We will combine the Gemini observations with the HST data to produce accurate photometric redshift estimates for background galaxies seen through the cluster lens. We are especially interested in detailed study of the galaxies associated with the SCUBA sources. Existing data show these can be detected at the limit of 4m IR imaging as heavily extinguished EROs (Extremely Red Objects). Photometric methods are the only realistic route to obtaining redshifts in these cases, requiring good S/N infrared data. High-resolution NIRI imaging, plus gravitational magnification, offers an exciting opportunity to probe the detailed structure of these poorly-understood objects. Finally, we will detect many gravitationally-lensed arcs seen through the cluster, whose redshifts can be estimated geometrically. This comparison will be the first independent test of photometric estimates at flux levels 10 times fainter than has been possible using classical spectroscopy, and will confirm the reliability of this technique for future use in very wide-field surveys of large scale structure with WFCAM/VISTA/etc.
Title: Globular Clusters as Probes of Elliptical Galaxy Formation
Abstract: We propose to obtain deep K-band images using NIRI of the rich globular cluster populations around two luminous Virgo ellipticals which have extensive optical photometry from WFPC2. One of the galaxies has a classic bimodal colour distribution in V-I, indicative of at least two distinct phases of cluster formation, whilst the other apparently has a singly peaked distribution. Both galaxies have similar luminosities and inhabit similar environments. We will use optical-IR two-colour diagrams to investigate why these two galaxies appear to have such different formation histories. Specifically we will investigate whether a cosmic conspiracy of younger ages and higher metallicities combines to produce the unimodal peak in the V-I colour distribution of NGC4365, and whether the red peak clusters in NGC4649 have a mean age close to that of the underlying spheroid - as predicted by models in which the blue peak clusters are accreted from neighbouring dwarf galaxies.
Title: Evolutionary Diagnostics of Local Group Dwarf Galaxies in the Infra-Red
Abstract: A complete model of galaxy evolution must fit not only giant galaxies, but also dwarfs. For example, in hierarchical merging models of galaxy formation, dwarf-like objects form first; present-day dwarf populations should include remnants of the first phases of galaxy formation. Dwarf galaxies similarly test the importance of key astrophysical processes, such as starbursts and gas outflows. These features, as well as possible evolutionary links between nearby dwarfs and large populations of faint blue galaxies seen at lookback times of 3-5Gyr, have led to well-focused explorations of stellar populations and evolutionary histories of nearby dwarfs. Now, in the era of excellent IR detectors on 8m class telescopes. it has become possible for studies of faint resolved stellar populations to begin in earnest in the infrared. This will bring significant advances in our understanding of the properties of the older stellar populations and how they form in the nearby Universe as we can look into the regime where they emit most of their luminosity. This proposal requests use of Gemini North to investigate nearby dwarf irregulars with unusual evolutionary histories by photometering evolved stellar populations with ages of 0.5-10Gyr in the IR, which will provide a valuable complement on the same spatial scale as our (optical) HST images for the same galaxies.
Title: The dust-enshrouded formation of massive elliptical galaxies
Abstract: We propose deep NIRI K-band imaging of the 12 brightest sub-mm sources ($S_{850} >8$mJy) detected in our major SCUBA/JCMT surveys. These sub-mm sources have inferred dust-enshrouded star-formation rates $>1000$ solar masses/yr, as required for the formation of the most massive elliptical galaxies in $\simeq1$ Gyr, and are sufficiently numerous to potentially account for the formation of all present-day massive ($>4L^{\star}$) ellipticals. Determining their nature/redshifts is now of fundamental importance for understanding galaxy/structure formation. Finding unambiguous IDs for these sources requires high-accuracy positions (from IRAM PdB or VLA follow-up already underway) combined with very deep infrared imaging. Our one existing deep (6 hrs with UKIRT) K-band identification has K=21-22, and a complex IR morphology reminscent of radio galaxies at z=3-4, offering a first clue that the high-z formation epoch inferred for radio galaxies may apply to massive spheroids in general. Deep NIRI observations represent a crucial step towards settling this issue.
Title: Young Methane Brown Dwarfs in Rho Ophiuchi
Abstract: We wish to obtain deep NIRI images towards the star formation region rho Ophiuchi using narrow band methane (CH4) 1.58um and 1.69um H band filters to search for CH4 brown dwarfs (T-dwarfs). Since methane is present only in very cool photosphere/atmospheres (Teff below 1300K), only methane T-dwarfs will show large brightness differences of up to 2 magnitudes over such a small wavelength range. These data will allow us to i) probe into the molecular cloud core and search for young T-dwarfs of age 10^6 to 10^7 years with masses in the range 3-5MJup and ii) detect of any (unobscured) object with strong CH4 absorption out to150pc.
Title: The evolution of high-redshift quasar host galaxies
Abstract: It is now apparent that most nearby massive spheroids harbour a black hole of proportionate mass. Consequently, black-hole and spheroid formation/growth are recognised as intimately-related processes, with the evolution of quasar host galaxies as a function of redshift now seen as a key measurement in observational cosmology. Using NICMOS on HST we have recently discovered that the masses of quasar hosts are essentially unchanged out to z=2. This result is beginning to conflict with the predictions of CDM-based hierarchical models of galaxy formation. If this trend continues to still higher redshift, then it is clear that current CDM-based models can be rejected. We therefore propose to use NIRI on Gemini to extend our study of quasar hosts out to z=4. This project exploits the capabilities of Gemini+NIRI to the full, as we require both excellent image quality and the ability (impossible with NICMOS) to detect low-surface brightness emission at K.
Title: Imaging the evolving dust cloud from WR140
Abstract: We propose tracking by multi-colour, high-resolution infrared imaging the dust cloud due to be emitted asymmetrically by the Wolf-Rayet system WR140 in 2001.2. We wish to measure the expansion and proper motion of the cloud and relate this to the colliding-wind structure (known from radio and X-ray studies) believed to provide conditions required for condensation and study the temperature and density gradients in the dust cloud to determine the properties of the dust. We seek images in three narrow-band filters at one epoch in Semester 2001A and will apply for 1-2 such observation in each of the next four semesters.
Title: Very Cool White Dwarf Stars: Constraints to the Chemical Evolution Models and Theories of Non-Ideal Gases
Abstract: We propose to use the NIRI on the Gemini to obtain near-infrared spectra of a selected sample of cool WDs to reveal for the first time the 1 -- 2.5 micron spectral properties of these stellar remnants. Our sample comprises four very cool (Teff 2500 -- 5000 K) WDs; one of them suspected to be binary systems. Such a comprehensive study has not been possible before due to relatively faint magnitudes of these objects (i.e., V 23 -- 19 vs K 18 -- 15). NIRI spectra will allow us to detect molecular H bands in the spectra of these objects and thus obtain definitive evidences on the presence of H in their atmospheres. These observations will place better constraints on the chemical evolution and provide support to recent theoretical calculations that predict that very cool low mass (He-core) WDs should have H-pure atmospheres. In addition these data will provide new constrains to the opacity in the near-infrared wavelengths and to the physics of non-ideal gases. We expect these observations will greatly contribute to improve our current knowledge of these objects, in particular the current chemical evolution models and the physics processes of non-ideal gases.
Title: The star formation history of the bulge
Abstract: This is a joint Argentina-Chile proposal to obtain sharp J, H and K-band images of two selected fields in the Milky Way bulge in order to constrain 1) the old stellar population of the Galaxy, 2) the faint end of the mass and luminosity functions, and 3) the evolution of the star formation rate in the bulge. We aim for photometry of point sources down to K=24 with sigma_K ~ 5%, which combined with existing deep HST optical images, will make the deepest views of the Galactic bulge: - the deepest color-magnitude diagrams, - the deepest luminosity functions, and - the sharpest images. Combining the IR photometry with the HST data we will determine not only the age (and possible age range) of this component of the Galaxy, but also its mass function down to 0.05 M_sun, essential to understand the possible MACHO population towards the bulge.
Title: GAMMA-RAY BURSTS AS A COSMIC WINDOW FOR STAR FORMATION AND GALAXY EVOLUTION
Abstract: Present knowledge indicates that gamma-ray bursts are linked with massive stars and will become invaluable probes of the early universe and galaxy formation. In the future, it will be possible to use gamma-ray bursts for two purposes: 1) to probe the history of star formation in the Universe by the rate of occurence of gamma-ray bursts, and 2) for the study of galaxy evolution in all lookback times by determining the nature of the galaxy hosts. Because gamma-rays are not attenuated by intervening dust and gas, the selection of the cosmic sites of massive star formation by this method is less affected by the biases associated with optical-uv surveys (e.g. UV-dropout technique). As a first step of this program, we propose deep optical and infrared imaging of gamma-ray sites with sky positions accurate to 1 arcsec to: 1) detect a putative population of reddened (R-K >= 4) galaxies at high redshifts, and 2) detect very massive stars (population III) formed at z >= 5.
Title: The Stellar and Interstellar Environment of Soft Gamma-Ray Repeaters
Abstract: After 20 years, the recurrent gamma-ray bursters (a.k.a. Soft Gamma-Ray Repeaters, SGRs) still represent a puzzle in high-energy astrophysics. Although X-ray pulsations associated SGRs to rotating neutron stars, the lack of deep optical/IR observations is a limit to their complete understanding. Tracking back to the properties of the neutron stars' progenitors would also be an important breakthroug. This came recently with the discovery that two, possibly three, repeaters are in SNRs and associated to clusters of young massive stars in dense molecular clouds. Thus, our goal is twofold, i.e., to unveil the nature of these SGRs and to study the properties of the putative parent clusters. To this aim, we need to perform high-resolution broadband (J, H, Ks, and L'). In addition, we want to study the interactions between the parent clusters, expanding SNRs and suspected neutron stars, with the local ISM through narrowband imaging in Br Gamma (2.16 $\mu$m) and H2 (2.12 $\mu$m).
Title: NIRI Spectra of the Molecular Hydrogen Outflow Associated with the VLA 1623 Proto-star in the Rho Oph Embedded Cluster
Abstract: We propose to obtain NIRI KHJ grism spectra of the molecular hydrogen outflow associated with the VLA 1623 proto-star, one of the youngest (10^5 yrs) and active object in the Rho Oph embedded cluster. We have selected four slit positions that will allow us to observer both the diffuse (jet-like emissions) and compact (knotty or HH-like structures) present in this outflow. Many H_2 and [Fe II] lines between 1 -- 2.5 microns will provide physical and kinematical information on the impact zone where hot atomic and molecular gas in the stellar jet meets the much cooler molecular gas in the surrounding cloud and forms the large scale 12^CO outflow. In particular, these spectra will allow us to derive electron densities and temperatures along the outflow. Relative line strengths will provide constraints to the different mechanisms of line formation. Several [Fe II] lines arising from a common upper level will provide accurate measurements of the extinction to the individual condensations forming the flow. We also expect to be able to constrain the velocity field of the HH knots (approaching and receding material) using radial velocities derived from the NIRI moderate resolution (R 700 -- 1000) spectral line measurements. Typical HH-knots/jets velocities range from 50 to 500 km/sec. These data will place better constraints on physical mechanisms for jet formation and for the interaction of jet material with the ambient cloud, in particular on the impact or transition zone where the stellar jet interacts with the surrounding cloud.
Title: Tidal Dwarf Galaxy Candidates in Stephan's Quintet
Abstract: We propose to image in J and Kprime the star-formation regions of Stephan's quintet, a small group of galaxies at at distance of 80 Mpc. Most of its gaseous material is not concentrated around the bright galaxies of the group but in the intragroup medium instead, suggesting that collisions among the group members may have taken place. A number of HII regions and tidal dwarf candidates have been identified by us around two of the brightest galaxies of the group (see Fig. 1). Our main goal is to resolve the several components of each region, to obtain their stellar masses and to date the bursts of star formation through analysis of B,R,J,K imaging.
Title: The Stellar Content of the Giant HII Region W51
Abstract: We propose to continue our survey of giant HII region, aimed to trace the spiral structure of our Galaxy and to study the nature of massive star formation. The method, based on spectroscopic paralaxes of newly born OB stars have proved to be much more accurate than previous ones. Ou recent results revealled clusters containing ZAMS OB stars and massive objects still in phase of matter accretion. Many of the brightest cluster members require large aperture telescopes like Gemini for spectral classification in the K-band.
Title: Near IR imaging of the nuclear region of NGC 5044
Abstract: We propose to obtain NIRI images of the luminous E galaxy NGC5044 at the J, H and Ks bands, in order to map the central dust disk, and to obtain high spatial resolution light profiles of the galaxy's core. Besides presenting strong H(alpha) and luminous X-ray emission, this galaxy presents chaotic gas kinematics and a significant offset between the systematic velocities of gas and stars, indicating that it might be a recent merger. Here we propose to take advantage of the high spatial resolution attained by NIRI for a detailed study of the stellar population gradients and formation scenario of this early-type galaxy. The data will also allow us to obtain infrared colors and map the dust distribution down to very small radii.
Title: The environment of the QSO PDS 456
Abstract: PDS 456 (Torres et al. 1997) is the most luminous QSO in the local Universe (z=0.184) and is brighter than 3C 273 at optical wavelenghts, beeing its radio-quiet analogue. The aim of the proposed observations is to identify the morphology and the environment of the host galaxy of PDS 455, verify the existence and nature of its close (< 4 arcsec) companions discovered at LNA. The infrared colors of the host galaxy may help to constrain the stellar population of the host galaxy and from the colors of the companions we will be able to detect evidence of recent star formation, obtaining mass and ages for the starbursts.
Title: The nature of the continuum and stellar population of distant
Abstract: We propose to investigate the nature of the continuum and stellar population of the radio galaxy 4C40.36, at z=2.265, as a first step in the study of the hosts of high redshift (z larger than 2) radio galaxies (HZRGs). These redshifts correspond to look-back times of 80-90% of the Hubble time, at approximately the epoch of galaxy formation, and to the peak of the Quasar activity. Recent findings indicate that the formation of supermassive blackholes are strongly linked to the formation of massive galactic bulges. This link can be investigated via the study of the stellar population of HZRGs, which are Quasars with a hidden nuclear source in the unified scenario, and thougth to be the progenitors of the giant elliptical galaxies. A characteristic additional feature of these galaxies is an excess in the near-UV spectral region, coming from extended regions aligned with the radio axis -- the so-called alignment effetc. Our goals are: (1) to investigate the origin of the alignment effect and (2) date the stellar population of HZRGs, using spectral synthesis techniques proved successful in our previous work on nearby Seyfert 2 galaxies. We t hus propose to obtain near-infrared long-slit spectra of the above galaxy using NIRI grisms in the J, H and K-bands, which, at z=2.265, will cover the rest-frame near-UV and optical regions of the spectra.
Title: Near-Infrared Observations of the most compact HII galaxies
Abstract: We propose to image a sample of four nearby, most compact, low luminosity star-forming dwarf galaxies in the near infrared. Among these low luminosity, extremely compact HII galaxies we expect to find the most metal poor galaxies in the local universe. If this is the case, these objects would represent nearby examples of 'primeval galaxies'. We wish to test this hypothesis by searching for a low surface brightness underlying older population which, if existent, should be distinguishable with high S/N imaging in the infrared. We also expect to identify the elementary component of the starburst region,the so-called 'Super Stellar Clusters'. The identification and description of these Clusters may reveal important physical mechanism of massive star formation in galaxies. Population synthesis models will be used to put some constraints on the ages, star formation histories, and the stellar populations of any component underlying the burst population and of any possible stellar clusters within the starburst, if these turn out to be resolved by the superb image quality delivered by GEMINI.
Title: THE HOST GALAXIES OF DARK GAMMA-RAY BURSTS
Abstract: Present knowledge indicates that most gamma-ray bursts are linked to the collapse of massive stars. Because gamma-rays are not attenuated by intervening dust and gas, the selection of the cosmic sites of massive star formation by this method is less affected by the biases associated with optical-uv surveys (e.g. UV-dropout technique). To study the history of star formation in the universe and galaxy evolution at all lookback times, we propose as a first step deep optical and infrared imaging of the cosmic sites where gamma-ray afterglows were localized with sub-arcsec error boxes by other groups, in either optical, infrared, radio, or X-rays (e.g. Chandra). The immediate purpose of this program is twofold: 1) the detection of a putative population of reddened (R-K >= 4) galaxies at high redshifts, and 2) the detection of very massive stars (population III) formed at z >= 5.
Title: Typical AGN host galaxies at the epoch of galaxy formation
Abstract: We propose to use the ultra-high resolution offered by Gemini to image the host galaxies of typical, L* luminosity, AGN at z~2. Our aim is to search for evolution in the luminosity and morphology of the host galaxies. In particular, we wish to answer the following question: is there a direct relation between AGN and star formation? That is, are the host galaxies of typical high redshift AGN also the hosts of massive starbursts? L* AGN are too faint to be used as AO guide stars. Our approach is unique in that we have selected our targets from the 2dF QSO Redshift Survey (2QZ), the only survey large enough to provide sufficient numbers of ~L* AGN which have nearby bright stars suitable for AO use. This approach offers the crucial advantage of avoiding the redshift-luminosity degeneracy that would otherwise compromise the search for evolutionary effects.
Title: Mid-Infrared Observations of Bright SCUBA Sources in MSX Infrared-Dark Clouds
Abstract: We propose to use OSCIR to observe several of the bright, compact sources identified in our SCUBA maps that also exhibit 8 µm emission in the MSX images. The angular resolution of 0.4" that OSCIR provides at N-band should reveal whether they consist of single bright objects, clusters of fainter objects, or extended emission from warm dust. The OSCIR images should reveal the structures of 8 µm MSX sources in sufficient detail to allow physical interpretation.
Title: The early evolution of very young starburst regions-I. NGC 2363
Abstract: The formation of massive superstar clusters (SSCs) is poorly understood, since they evolve quickly from the anonymity of dense cold giant molecular clouds, through hidden dust embedded proto-clusters, into powerfull starbursts. This metamorphosis, which takes place over only a few Myr, has a profound impact on the surrounding interstellar matter. We propose to use Gemini (with NIRI and OSCIR) to probe the stellar content and environment of a prototypical young SSCs, NGC 2363.
Title: Mapping the Dust and UIR emission in Planetary Nebulae
Abstract: While people assume that the dust in planetary nebulae represents remnants of circumstellar dust envelopes ejected during the preceding AGB phase, there has been no good mapping of the dust distribution in planetary nebulae. Recent ISO observations suggest that the aromatic hydrocarbon band (AHB) emission features are formed during the proto-planetary nebulae phase. We propose to map NGC 7027 and BD+303639 at 10.8, 11.7, 12.5 and 20.8 microns to compare the distributions of the dust continuum and the AHB features to the ionized gas component.
Title: Imaging the Circumstellar Environments of Prolific Wolf-Rayet Dust Makers with OSCIR
Abstract: We propose to use the high angular resolution and sensitivity of OSCIR/Gemini to resolve and map, for the first time, the coolest regions of dust envelopes around three known prolific dust-making, population I Wolf-Rayet stars. The high resolution, multi-color images will help us (a) to understand the physics of dust survival in apparently hostile, hot-star environments; (b) to verify and fine-tune models of dust formation; and (c) to reveal the recent ($t ^< _\sim 10^2$ yrs) history of mass loss.
Title: The early evolution of very young starburst regions-I. NGC 2363
Abstract: The formation of massive superstar clusters (SSCs) is poorly understood, since they evolve quickly from the anonymity of dense cold giant molecular clouds, through hidden dust embedded proto-clusters, into powerfull starbursts. This metamorphosis, which takes place over only a few Myr, has a profound impact on the surrounding interstellar matter. We propose to use Gemini (with NIRI and OSCIR) to probe the stellar content and environment of a prototypical young SSCs, NGC 2363.
Title: Disk galaxy stellar mass assembly history
Abstract: Once a field disk galaxy falls into a cluster, star formation ceases and the disk becomes a fossil record representing the state of evolution of the field population of disk galaxies at the epoch of infall. We propose to use K-band imaging together with existing HST optical imaging of clusters at s=0.43, z=0.55, and z=0.83 to estimate the stellar mass in the population of disk galaxies at these epochs. If disks formed recently then there ought to be a dramatic difference in the distribution of mass in disks of a given size, since the stars formed between z=0.43 and 0.83 represent a large percentage of the total whereas if most of the star formation action is at higher redshifts, then the disk mass distributions ought to be similar.
Title: Deep NIRI imaging of SCUBA cluster fields
Abstract: We propose to use NIRI to image five clusters where SCUBA observations have revealed bright sub-mm sources. Previous studies indicate a correlation between these sources and faint red (K~22, I-K~ 6) galaxies. NIRI's field of view is comparable to SCUBA's, and the resolution and depth obtainable with Gemini/NIRI should allow us to identify the near-IR galaxies associated with the sub-mm emission. Targets for future spectroscopy can then be selected in order to pin down their redshift distribution.
Title: The impact of the youngest Super Star-Clusters on the insterstellar medium in He 2-10
Abstract: He 2-10 is a galaxy that displays the complete phenomenology of Super Star-Clusters, from the dust-embedded formation to the visible stage. We propose to derive with similar spatial resolution both the stellar parameters of the complete population of SSC (visible and obscured) and the distribution of the interstellar medium to confirm the nature of the embedded sources and understand their impact on the ISM. This will allow more accurate predictions of the spectrum of starbursts during their first evolutionary stages.
Title: Stellar and gas morphology around highest redshift QSOs
Abstract: We propose deep NIR imaging of QSOs in the redshift range 4.6 to 5.2 whose redshifted [O II] line emission lies in the passband of NIRI narrow band filters. A combination of K' and narrow-band images will map the stellar continuum and line emission from the QSO host galaxies and also provide candidates for associated galaxies in the QSO environment. This project makes use of the light gathering power, image quality and wide field of Gemini and NIRI. It will provide new evidence on the galaxy populations at very high redshift, and the triggering of the earliest QSOs.
Title: Deep IR Imaging of Red Galaxies at Redshifts z>1
Abstract: We are undertaking an H and K-band survey of nearly one square degree at a depth that reaches passively evolving L* galaxies up z=2. Our sample contains hundreds of "Extremely Red Objects" (EROs): galaxies that are redder than z=1 ellipticals in I-H. The relatively blue optical colors and extremely strong clustering of these objects is an enigma which we propose to address with deep J and K-band Gemini NIRI imaging.
Title: The massive stellar content of the Galactic Centre clusters
Abstract: We will obtain narrow-band imaging of three Galactic Centre clusters with NIRI, to discover their massive stellar populations, which are expected to be substantial at high metallicity. These data will provide a test for future massive star searches in reddened extra-galactic environments. Additional L-band specroscopy will allow us to reliably constrain stellar properties of HeI emission line sources in each cluster via detailed non-LTE analysis, necessary for us to determine their contribution to the Lyman ionizing flux of the central region.
Title: Metallicities of star-forming galaxies at redshifts 0.5 to 1.0
Abstract: We are undertaking a program of optical/NIR emission-line spectroscopy of 0.5 < z < 1.0 star-forming CFRS galaxies to measure their ISM metallicities. Preliminary results, based on the optical lines, suggest high metallicities, at variance with the conventional idea that these objects are brightened dwarfs. However, near-IR observations of Halpha, [NII] and [SII] are required to (a) break the low versus high metallity-degeneracy in the optical; (b) discriminate between low metallicity objects and AGN; (c) correct for reddening.
Title: Comparing the Stellar and Gas Phase Metallicities in Nearby Dwarf Irregular Galaxies
Abstract: We propose to measure the strength of 2.3 micron CO absorption in bright red giant branch stars in three nearby isolated dwarf irregular galaxies (SagDIG, Sex A, and Leo A). These data will be used to estimate mean global (i.e. [M/H]) stellar metallicities for these galaxies, which also have gas phase metallicities determined from HII regions. We will compare stellar and gas phase metallicities, and thereby gain insight into the origin and evolution of gas in these systems. If the gas phase metallicity, which is based on species such as oxygen that are formed mainly in SN II, is significantly different from the global metallicity, which will be derived here, then this implies a chemical enrichment history that has been sporadic, whereas if the gas and stellar metallicities are similar then a slow enrichment history is implied. The results from this study will also provide a means of calibrating the global metallicities of more distant systems, where individual stars can not be resolved. Finally, the data will also be used to investigate the star-forming histories of these systems during intermediate epochs using the AGB content.
Title: NIRI Imaging and Spectroscopy of faint SCUBA sources
Abstract: The deep SCUBA surveys by ourselves and others have significantly changed our understanding of the early universe, revealing a population of very luminous obscured objects at high redshifts that emit a substantial fraction of the bolometric energy output of the Universe. We here propose using NIRI to obtain deep NIRI images to seek identifications for 6 unidentified sources and deep NIRI spectra to determine the redshifts of a prototypical secure but very red identification. These observations will lead us to a much improved understanding of the role of these objects in the formation and early evolution of galaxies.
Title: U.S.G.P. Mini-Queue Observations with Hokupa'a
Abstract: The observations described in this proposal are to be carried out as part of the USGP-run ``mini-queue'' program for Hokupa'a and for OSCIR. USGP staff will make the observations. Title: The Host Galaxies of Very High Redshift Quasars (R. J. Brunner et al. Abstract: Understanding the formation and evolution of both galaxies and quasars are among the premier goals of extragalactic research. The current expectation is that the evolutionary histories of these two classes of objects are somehow intimately related; that is the (proto-)galaxy interactions that arise during hierarchical structure formation first created and then fueled the quasars. All of the empirical evidence supporting this belief, however, is for quasar systems at low redshift ($z < 0.5$) where we may be seeing special end-cases due to the evolved nature of the host galaxy. At the higher redshifts corresponding to the time when quasars were most abundant ($z \sim 2$), there have been no conclusive measurements. {\em Yet this is the regime where the most compelling physical commonalities between quasars and their host galaxies arise}. We, therefore, propose to remedy this situation by obtaining adaptive optics $H$-band observations using the Gemini North telescope with the Hokupa'a/QUIRC camera of two intrinsically luminous, high redshift quasars ($z \sim 2$) to both identify the morphologies of the proto-galaxies fueling the quasar and to also quantify their evolution with redshift by comparison to published, low redshift results. With this exploratory survey ({\bf which can currently only be done with Gemini Adaptive Optics}), we will be able to, for the first time, uncover quasar host galaxies at the peak of the quasar era. Title: The Nuclei of M32$\pm$1 with Hokupa'a (T. Lauer et al.) Abstract: Broad-band J and K images will be obtained of the nuclei of the three Local Group galaxies M31, M32, and M33. The resolution of these images should match that of HST optical images, and will be used to characterize stellar populations of these nuclei on $r<0.2$pc scales. Stellar collisions are expected to play a role in modifying the population in all three systems; the NIR images may identify evolved stars of intermediate ages. In addition, for M31 the nature of the extremely compact blue cusp of stars that surrounds the central massive black hole will be explored. In M33 a test between a model of the nucleus as a dusty, recent starburst versus an older population modified by stellar collisions will be performed. In all three galaxies, $K$ versus $J-K$ CMDs of resolved stars will characterize the metallicity distribution of the galaxies' central stellar populations. Title: Imaging the final flash shell around V605 Aql (K. Hinkle et al.) Abstract: Post-AGB stars can undergo a final episode of helium shell burning after the star has ejected a planetary nebula and has started on the white dwarf track. Starting in 1996 Sakurai's star has been observed to undergo a final helium shell flash. The same series of events occurred in V605\,Aql 81 years ago. Both stars were observed to eject a shell of gas first seen as a pseudo-photosphere and then as a thick dust envelope. The shells are expanding at $\sim$100\,km\,s$^{-1}$ and in the case of V605\,Aql the shell now appears about 1{\arcsec} across. We propose to image the V605\,Aql dust shell with Hokupa'a/QUIRC. These images will be used to discriminate between bipolar and lumpy models of the circumstellar shell. Since the precursor to the final flash was a white dwarf, as opposed to an AGB star with a complex structure and complex circumstellar environment, the observations will provide a test of the origins of structure in circumstellar shells and planetary nebulae. Title: Adaptive optics imaging of a gravitational lens galaxy (J. N. Winn et al) Abstract: We request 2 hours with Gemini North and QUIRC/Hokupa'a for AO imaging of a newly discovered gravitational lens candidate, in order to find and characterize the lensing galaxy. The galaxy will lie between two brighter QSO images that are separated by only $1\farcs5$, so high-resolution imaging is essential. An accurate determination of the lens galaxy's position, magnitude and morphology will allow interesting astrophysical information to be obtained from the system, such as the $M/L$ ratio of the galaxy, and the relation between the time delay and $H_0$.
Title: Origins of Disks \& Protoplanetesimals Using Silicate Mineralogy
Abstract: The analysis of the carbonaceous materials and silicate mineralogy of pre-main sequence Herbig Ae/Be (HAEBE) stars to main sequence $\beta$-Pic systems probes the chemical and physical conditions in these potentially planet-forming environments, the condensation of dust from the gas-disk, and the aggregation and accretion of these solids into planetesimals and comets. We propose to obtain low resolution OSCIR spectra of the 9.3~\micron \ crystalline pyroxene and 11.2~\micron \ crystalline olivine features in HAEBE and $\beta$-Pic debris disk systems. The OSCIR spectra are required to model how the grain mineralogy and size distributions vary spatially from the inner disk to the outer disk/envelope. We will synthesize dust emission spectra using grain-scattering and radiative transfer models of optically thick disks and optically thin dusty disk atmospheres. Our extensive observational and analytical modeling efforts will characterize the connections between silicate mineralogy and the origins and evolution of disks and protoplanetesimals.
Title: U.S.G.P. Mini-Queue Observations with OSCIR
Abstract: The observations described in this proposal are to be carried out as part of the USGP-run ``mini-queue'' program for Hokupa'a and for OSCIR. USGP staff will make the observations. Title: The very young star clusters of NGC 3690 (D. Devost et al.) Abstract: We propose to study the characteristics of star-forming regions observed in the luminous starburst galaxy NGC 3690. HST/FOC UV images and ground based optical and NIR data revealed many knots of star-formation. We propose to observe one field with OSCIR Q18 $\mu$m filter to uncover buried star forming regions of a younger age. We believe that these young regions exist but have been missed by UV-optical studies where dust extinction is high. An 8 $\mu$m image will then help us make a crude estimate of the nature and the age of these regions. Spectroscopic follow-up with SIRTF is planned with GTO time in order to better characterize the stellar populations identified. All these observations will give us an unprecedented view of the properties of a star-forming region at high resolution. This project is part of an ongoing program to understand galaxy evolution. Title: Identification and Characteristics of Massive Protostars: W51 IRS2 (J. P. Simpson et al.) Abstract: We propose to image the dense stellar cluster and Ultra Compact H II region (UCHR) W51 IRS2/W51d with NIRI and OSCIR on Gemini. It is already known that there are several very red sources in the cluster within the central 1.5$''$ plus an outflow source with maser emission; some or all of these are likely to be protostars or young stellar objects. Because of the very young age of the cluster and UCHR, there are almost certainly additional protostars/YSOs that will be detectable if the spatial resolution is sufficiently high. We will determine the spectral energy distributions for each of the sources from the 1.65 to 20 \micron\ fluxes from photometry and thus the source luminosities and identify which sources have winds that produce shocked H$_2$ emission. The long-term purpose (additional high resolution spectroscopy of the identified protostars will also be needed) is to determine the importance of outflows versus winds at early evolutionary stages of massive stars. Title: Resolving the starburst in Arp 220 with min-infrared spectral mapping (C. Dudley et al.) Abstract: The new availability of the Gemini North telescope together with the reliable and sensitive OSCIR spectrograph offers the exciting possibility of resolving the issue of {\em What Powers Ultraluminous Galaxies}. Resolution of this question is important for understanding the building processes of spheroids and the role of mergers in the evolution of galaxies as a whole, but the issue has remained both elusive and controversial despite the best work of ISO. Spatially resolved mid-infrared spectroscopy has the potential to address this question for a small number of nearby ULIRGs. Early efforts in this regard were hampered by low detector sensitivity and poor telescope performance, but such studies should now be feasible. We propose to demonstrate this feasibility by mapping the closest ultraluminous infrared galaxy Arp 220 in the wavelength range 9.74--13.4 $\mu$m with a spectral resolving power of 82 and spatial resolving power of 0.4 arcsec. This wavelength range covers both the 11.3--12.7 PAH complex as well a continuum both within and without the 9.7 micron silicate feature. These data will be able to spatially separate extended star formation regions from the self-absorbed centrally powered compact nuclei in Arp 220 or conversely to show that these two components are spatially coincident. Five hours of moderate seeing and photometric mini-queue time are required to complete and calibrate these observations. Title: Ultradense HII Regions in He2-10 (P. S. Conti et al.) Abstract: We will use Gemini to observe the newly discovered ``ultradense HII regions'' in the starburst galaxy He 2-10 at mid-IR wavelengths. These giant, dense HII regions harbor the youngest massive star clusters yet observed. First identified as optically thick free-free radio sources, these ultra-young clusters are are still embedded in their birth material and are completely opaque at optical and near-infrared regimes. They can be observed only at mid-IR to radio wavelengths. Observations at 10 and 18 microns with OSCIR on Gemini will allow us to investigate the physical conditions under which massive star clusters form by directly detecting emission from the warm dust and ionized gas associated with these clusters at high spatial resolution. These observations will also enable us to determine what fraction of the total IR flux from He 2-10 is due to the enshrouded clusters.
Title: QSO Host Galaxies: The Link to Nuclear Properties
Abstract: Studies of the emission-line spectra of QSOs and other AGN find that many of the observable properties (line strengths, widths, and profile parameters) are correlated. One proposed explanation of this sequence is that an object's position along it is determined by the fraction of Eddington luminosity at which it is radiating. Recent observations of QSO host galaxies, together with the supposition that there is a good correlation between the mass of the galactic spheroid and the mass of the accreting black hole, support this idea. Putting these pieces together leads to a fairly simple picture linking all kinds of active galaxies into a set of relationships with a small number of controlling physical parameters. This project is to provide a much more definitive test of this idea by obtaining high spatial resolution images of a complete sample of well-studied low-redshift QSOs. Additional uses of the data will be to explore the host galaxies themselves, in order to determine the types and luminosities of galaxies in which QSOs form and to detect indications of morphological or environmental peculiarities that might affect their fueling.
Title: A High-Resolution Mid-Infrared Study of Circumstellar Disks Around Massive Stars
Abstract: The formation of stars is a critical and fundamental topic in astronomy. However, not much is known about how high mass stars (O and B types) form. Evidence that massive stars may form via accretion in a similar way as low-mass stars comes from maser emission observations. Recently methanol masers have been plausibly argued to delineate circumstellar disks around massive stars. Advances in mid-infrared astronomy now allow direct detection and observation of massive stars in their earliest stages of life. In exploratory observations at CTIO, we have resolved three circumstellar disks around high mass stars exhibiting methanol maser emission. This is the first direct evidence that massive stars from via accretion and have circumstellar disks. We propose to use Gemini and OSCIR to perform a high-resolution survey of 9 circumstellar disk candidates. These observation will allow us to directly detect and resolve these circumstellar disks and determine their detailed physical proper! ties for the first time.
Title: High-Resolution Mid-IR Imaging of Seyfert Nuclei; Testing the Evolutionary Hypothesis
Abstract: In classical 'unified theories' of Seyfert (Sy) active galactic nuclei (AGN), the classification as a type 1 or 2 AGN is dependant solely on the observed line of sight to the AGN. A key feature of unified schemes is the existence of a geometrically and optically thick molecular torus surrounding the central engine. For Sy 1 AGN a direct view of the central engine is made whereas the torus obscures the central engine for Sy 2 AGN. Recent surveys have raised questions as to whether the viewing angle is the sole defining characteristic of Sy classification. These surveys reveal the level of star formation typically displayed in a Sy 2 host galaxy is greater than Sy 1 hosts consistent with the theories of Heckman et al. (1989) who suggested the Sy host galaxy evolves, changing the classification of the AGN from type 2 to 1. A key test for such theories is provided by the observation of circumnuclear star formation. High resolution mid-IR imaging of the nuclear regions of a sample of Sy 1 and 2 host galaxies will provide a definitive test of Heckman's theories of Sy evolution.
Title: Mid-infrared imaging of M87
Abstract: As part of our ongoing investigation of M87, the nearest and brightest giant elliptical galaxy, we propose to conduct mid-IR imaging observations with OSCIR on Gemini. This will be the first time any elliptical galaxy {\it or} active galactic nucleus (AGN) has been imaged in the mid-IR at sub-arcsecond resolution. Ground based and HST observations in the optical-near-IR show many features in M87 which are common to many bright ellipticals and AGN: a jet, nuclear and large-scale dust, and an active accretion disk. We have three goals in this proposal. (1) To measure the morphology of the jet in the mid-IR and measure the shape of its IR spectrum. This will allow us to test the first model ever built for the 3-D energetic structure of any jet, a model which is critical to understanding the many differences being observed in deep HST and Chandra observations of this and other jets. (2) To measure the thermal emission from dust lanes (seen in HST images) on scales of tens to hundreds of parsecs and place further constraints on their physics. (3) To observe and resolve thermal emission from the dust in the torus, which is predicted by unified schemes, and hinted at by HST images. This will be the first direct measurement of this quantity, which is critical to unified schemes. Given its brightness and proximity, M87 is the only object for which these measurements can currently be made.
Title: Deep Mid-IR Imaging of an Evolutionary Sequence of Debris Disks
Abstract: We propose deep 10 and 18 $\mu$m imaging on a carefully selected sample of Vega-like sources which we believe fit into an evolutionary sequence. Using the H-R diagram we have selected 15 Vega-like sources with debris disks which we believe are divided into three classes: stars moving onto the zero-age main-sequence (ZAMS), stars {\it on} the ZAMS, and stars moving off the ZAMS. Our proposed mid-IR observations will allow us to characterize these disks for the first time and probe the differences in the structure of debris disks at different evolutionary stages. In addition to testing our evolutionary hypothesis the characterization of each of these disks will greatly impact our understanding of disk composition, as well as our understanding of planetesimal and planet formation in these disks. Characterizing circumstellar disks in the thermal-IR is exactly what Gemini was built to do. The proposed observations are designed to exploit all of Gemini's strengths, and our team has extensive experience using OSCIR for this exact project. We request a total of 3 nights to complete the 2001A portion of this program.
Title: Cosmology with High-Redshift Type Ia Supernovae
Abstract: The current Type Ia supernova Hubble diagram and CMB observations argue for a flat universe with some form of ``dark energy'' accelerating its expansion. Studies of distant supernovae can probe the expansion history of the universe through our current dark-energy-dominated era back to a matter-dominated era, making them one of the best current methods to study the amount and nature of such dark energy. The CTIO 4-m telescope will reach back in time to find supernovae when the universe was still matter-dominated, extending our understanding of the expansion of the universe and possible evolution of supernovae over time (for which we will use several different tests). The WIYN-SYN telescope will allow us to photometrically follow-up a selection of these supernovae to measure the brightness of these standard candles as a function of redshift. The Gemini NIRI will allow us to obtain crucial data for the very highest-redshift ($z \gtrsim 1$) supernova whose rest-frame V-band will have been redshifted to our J-band.
Title: Direct Comparison of Optical and Infrared Searches for High-Redshift Galaxies: How Much of the Young Universe has been Obscured by Dust?
Abstract: The leading uncertainty in our knowledge of star formation in the young universe is the amount of luminosity that is absorbed (and then re-reradiated) by dust grains. We will use NIRI in a narrowband imaging search for high-redshift emission-line galaxies ([OIII]5007 at z=3.3-3.4 and H$\alpha$ at z=2.2-2.3). The wide areal coverage of optically-studied fields will allow the first direct quantitative comparison of this successful search method with the Lyman break method, which uses optical photometry to measure the far-UV rest-frame continuum of $z \ge 3$ galaxies. Because of its large number of pixels, NIRI is the only instrument in the world currently fast enough to do this project (Keck would be a factor of 10 slower). We suspect that the Lyman break method is missing at least half of all high-z galaxies, because their far-UV continuum is reddened by dust. If so, our search of previously studied LBG fields in only 2 nights will determine this. We will detect at least 16-20 galaxies at $z \sim 3.3$, the majority of which were previously missed.
Title: The Extended Star Formation Histories of M81 Group Dwarf Elliptical Galaxies
Abstract: We propose to use NIRI J and K band observations to survey five M81 group dwarf elliptical (dE) galaxies for upper asymptotic giant branch (AGB) stars. Such stars are an indicator of the presence of intermediate-age (2 $\lesssim$ age $\lesssim$ 10 Gyr) populations. Our HST/WFPC2 study (in the V and I bands; Caldwell et al., 1998, AJ, 115, 535) has revealed the presence of significant numbers of upper-AGB stars in two M81 group dEs, and we wish to establish if this is a common occurrence by studying other dE members of this group. Near-IR band photometry is required to determine bolometric magnitudes, and therefore age estimates, for any upper-AGB stars found. Our results will provide information on the extended epochs of star formation (if any) in these dwarf ellipticals and will be directly comparable to existing information for Local Group dEs, such as the dwarf companions to the Galaxy and to M31. In this way we will add to the understanding of the factors, which include environment, that govern the star formation history of these galaxies.
Title: The nature of sub-mm luminous galaxies: optically faint radio sources and a $z=3$ protocluster region.
Abstract: The recent discovery of a population of submm-luminous sources has unveiled a new window on galaxy formation and evolution in the early universe. However, the nature of the sub-mm sources and their relation to extragalactic populations on the whole is currently a matter of heated debate. We propose to undertake a NIRI near-IR observation of the $z=3.09$ SSA22a protocluster region, known to be a hotbed of dust obscured, sub-mm luminous activity. We also propose near-IR observations of the optically faint radio sources in the HDF VLA field, with emphasis on those radio sources with sub-mm detections. Such observations will:\\ $\bullet$ enable the identification of optically invisible ($I>25$) sub-mm and radio sources;\\ $\bullet$ allow comparison of the rest-frame optical to sub-mm/radio luminosity;\\ $\bullet$ permit photometric redshift estimates for these sources, to be compared with that measured through the sub-mm/radio index.
Title: Elemental Abundances and Star Formation History at z=5.8
Abstract: High redshift quasars can provide unique insights into the first star formation epoch in the early universe. If the gas near quasars is related to the interstellar matter of the host galaxy, quasars can be used as tracers of the star formation and chemical enrichment history of the host environments. Recent studies of quasars at moderately high redshift (z$\simeq$3-4) show solar and even supersolar metallicities in the line emitting gas. These results require a rapid and efficient phase of star formation in the early universe. The quasar SDSSp\,J104433.04-012502.2, with the currently known highest redshift (z\,=\,5.80), allows us to study the chemical enrichment by stars at a time when the universe itself was less than 1 Gyr old. We propose NIRI-Gemini-North observations of this object to measure its various rest-frame UV emission lines. The results will be compared to model calculations and quasars at lower redshift to estimate the chemical enrichment of the gas and derive an age for the corresponding stellar population.
Title: A Near Infrared Investigation of Optically Obscured Galactic Giant H~II Regions
Abstract: We propose to continue our survey of giant HII regions at $JHK$. Our eventual goals are to characterize their stellar content, investigate the nature of massive star formation, and to use the derived infrared spectral types to determine distances and as probes of Galactic structure. The infrared photometry will be used to identify massive star and young stellar object candidates for follow--up spectroscopy (on 4m and 8m class telescopes). Our program and other recent near infrared observations are producing examples of clusters of newly born massive stars. This mode of star formation is virtually unexplored in the Galaxy due to obscuration by dust toward star forming regions. In addition, to the best of our knowledge, our present observations and those by Hanson et al. (1997) form the largest known sample of massive young stellar objects (YSO). We have already identified O stars and massive YSOs in a number of GHII regions and will continue our succesful survey in other GHII regions using 4m imaging for new clusters and 4m spectroscopy for clusters for which we already have imaging data. Further, we will use Gemini to go farther down the main sequence spectroscopically in W31 producing a more accurate mass, age, and luminosity for this rich young cluster.
Title: Constraining the Lifetimes of Circumstellar Disks:L band Observations of NGC 2362
Abstract: We propose to obtain deep JHKL$^\prime$ imaging of 100 stars in the young stellar cluster NGC 2362 using NIRI on Gemini North. We have shown that the combination of JHKL imaging photometry is capable of detecting essentially all of the circumstellar disks around young stars. Our proposed Gemini observations are critical for our overall program to determine the frequency and lifetimes of circumstellar disks in young stellar clusters, the preferred sites of star formation in our Galaxy. NGC 2362 is key to this program since it has an age of 5 Myrs. From our previous observations, this age is roughly equal to the timescale over which circumstellar disks are estimated to dissipate. The main goals of these proposed observations are to determine if the circumstellar disk fraction of all stars in NGC 2362, down to the hydrogen burning limit, is significantly reduced, as expected from its age and to test if the lifetimes of circumstellar disks are a function of stellar mass.
Title: Detecting the onset of methane in L dwarfs
Abstract: The late L dwarfs and early T dwarfs remain the most poorly characterized objects in the substellar sequence. The most profound physical change at this class boundary is the change in carbon chemistry from CO- to \ch -dominated as temperature decreases. Direct observations of this changeover are very limited. We have recently identified the 3.3 \um\ \nuthree\ band of \ch\ in an L5 and and L7.5 dwarf (Noll et al.~2000), the warmest objects in which \ch\ has been detected. Also in the last year, several T dwarfs with weak near-IR bands (Leggett et al.~2000) have begun to fill in the gap between objects with strong near-IR methane like Gl~229B (Oppenheimer et al.~1998), and the L dwarfs which show no near-IR methane. However, the large uncertainties in effective temperatures of objects near the L/T transition remains unresolved. We propose to observe the much (100x) stronger \nuthree\ fundamental band of \ch\ at 3.3 \um\ in four late L dwarfs ranging from L5 to L8. Observations of this band will allow us to determine effective temperatures and establish the smoothness and completeness of the existing brown dwarf inventory at the L/T boundary.
Title: Black Holes in Brightest Cluster Galaxies
Abstract: The largest galaxies, and especially brightest cluster galaxies (BCGs), offer special insight into formation and evolution because they represent the extremes of these processes. Black holes are now believed to be essential components of galaxies, and their evolutionary states appear to be intimately linked to those of their hosts. By studying black holes in BCGs, we will push theoretical predictions for formation of both black holes and their hosts. We will measure central stellar kinematics in a sample of nearby brightest cluster galaxies using the IR CO bandhead. These IR observations are superior to any that are possible with the Hubble Space Telescope, because the surface brightnesses are too low for HST, and because of the good seeing of Gemini at K-band. The measured black hole masses will extend the black-hole/sigma correlation to its extreme end, testing black hole formation models. In addition, by combining these data with extensive kinematic coverage at McDonald Observatory, we will measure the stellar orbital distribution throughout the galaxies. This information directly probes the galaxies' evolutionary processes. Furthermore, these observations serve as a first step in opening up a potentially huge avenue in black hole research: once adaptive optics are available with IR spectrographs, many galaxies that cannot now be observed with HST will readily be feasible.
Title: Deep K and L$^{\prime}$ images of the youngest nearby cluster
Abstract: High resolution, deep near--infrared observations enabled by the new generation of instruments on 8--10m class telescopes (as well as NICMOS on HST) of embedded young clusters have provided the first complete census of objects over the full range of masses within cluster--forming molecular cloud cores. Utilizing NIRI on Gemini--North, we propose to survey the densest parts of the nearest remnant of a giant molecular cloud: the L1688 dark cloud in Ophiuchus, the last gasp of star formation within the Sco--Cen OB Association, known to have formed both high and low mass stars. The embedded cluster associated with L1688 is unique in: (1) its proximity to Earth (145 pc); and (2) its extreme youth (as evidenced by its high proportion of optically--invisible protostars). The high angular resolution of NIRI+Gemini (0.116'' pixel$^{-1}$) and its superior sensitivity ($\rm{K_s < 21.0^m}$ and $\rm{L^{\prime} < 17.0^m}$), combined with extant observations at shorter wavelengths with NICMOS, will provide the most sensitive survey of a cluster of protostars to date, as well as the first complete census (M$ \ge $20$\rm{M_{Jupiter}}$) of a protostellar cluster viewed through the entire depth of the cloud ($\rm{A_V < 75^m}$). Because most stars in the galactic disk are thought to arise in such clusters (which evolve into unbound associations), understanding their structures, multiplicity, and substellar mass functions will place fundamental constraints on the dominant mode of star formation in the Milky Way, and provide insight into the initial conditions that may have prevailed during the formation of our solar system.
Title: The Stellar Density Around Massive Young Stars: A Test of Collisional Models of High Mass Star Formation
Abstract: We propose deep ($21.4$, $21.2$, $21$~mag. in $JHK$) observations of the NGC 6334 I molecular core. This core contains two young massive stars surrounded by a cluster of lower mass stars. With the exceptional sensitivity of Gemini, we can detect low mass stars in the vicinity of the two deeply embedded high mass (proto)stars, and obtain the first measurement of the stellar density within 0.02 pc of these massive stars. From this data, we will infer the rate of stellar collisions in a region of very recent massive star formation and test whether massive stars may form through the collision and coalescence of lower mass stars.
Title: Confirming and Characterizing Young Lyman-$\alpha$ Galaxies at $z=4.5$
Abstract: Our knowledge of galaxies at $z \ga 3$ depends heavily on their rest-frame UV properties. This is especially true for \lya\ emitting galaxies, which will preferentially include the youngest and most chemically primitive objects. Redshifts of these sources are based on a single line, which is identified as \lya\ with circumstantial evidence (line asymmetry and a continuum break) (Stern \& Spinrad 1999). Their other properties are inferred from $1500$\AA\ continuum emission, which is insensitive to older stellar populations. We will remedy this situation with near-infrared (K band) spectroscopy and imaging of confirmed $z\approx 4.5$ galaxies from our Large Area Lyman Alpha (LALA) survey. Our NIRI observations will allow us to confirm and characterize these early galaxies in four important ways:\\ (1) The \lya\ redshift will be confirmed by detection of the \oii\ line.\\ (2) The \oii\ line will yield star formation rate (SFR) estimates. Comparing these to \lya\ and UV continuum SFR measurements will cross-calibrate SFR indicators normally used at different redshifts, and will test for dust absorption in our \lya\ sources.\\ (3) K band photometry can be compared to existing R, I, and z' data to look for light from ``old'' ($> 10^8$ years) stellar populations. Our NIRI spectra will also observe the $4000$\AA\ break, providing another test for old stars and lifting the degeneracy between dust and age in broadband colors. Old stars, if present, would have to have formed at $z \ga 6$.\\ (4) Rest optical light morphologies can be compared to the expectations from monolithic collapse and hierarchical formation scenarios, and can also directly compare newly-formed galaxies with their present day counterparts.
Title: Confirming and Characterizing Young Lyman-$\alpha$ Galaxies at $z=4.5$
Abstract: Our knowledge of galaxies at $z \ga 3$ depends heavily on their rest-frame UV properties. This is especially true for \lya\ emitting galaxies, which will preferentially include the youngest and most chemically primitive objects. Redshifts of these sources are based on a single line, which is identified as \lya\ with circumstantial evidence (line asymmetry and a continuum break) (Stern \& Spinrad 1999). Their other properties are inferred from $1500$\AA\ continuum emission, which is insensitive to older stellar populations. We will remedy this situation with near-infrared (K band) spectroscopy and imaging of confirmed $z\approx 4.5$ galaxies from our Large Area Lyman Alpha (LALA) survey. Our NIRI observations will allow us to confirm and characterize these early galaxies in four important ways:\\ (1) The \lya\ redshift will be confirmed by detection of the \oii\ line.\\ (2) The \oii\ line will yield star formation rate (SFR) estimates. Comparing these to \lya\ and UV continuum SFR measurements will cross-calibrate SFR indicators normally used at different redshifts, and will test for dust absorption in our \lya\ sources.\\ (3) K band photometry can be compared to existing R, I, and z' data to look for light from ``old'' ($> 10^8$ years) stellar populations. Our NIRI spectra will also observe the $4000$\AA\ break, providing another test for old stars and lifting the degeneracy between dust and age in broadband colors. Old stars, if present, would have to have formed at $z \ga 6$.\\ (4) Rest optical light morphologies can be compared to the expectations from monolithic collapse and hierarchical formation scenarios, and can also directly compare newly-formed galaxies with their present day counterparts.
Title: Stellar Populations in Two Massive Galaxies at ${\bf z\simgt1.5}$
Abstract: The oldest and most massive galaxies at high redshift provide stringent constraints on the earliest epoch of galaxy formation, and thereby the age of the Universe and the fundamental cosmological parameters. The host galaxies of radio sources are the only $z>1.5$ galaxies known to contain old stellar populations as indicated by their red optical--infrared colors. Indeed, deep optical spectra of two $z\sim1.5$ weak radio sources (LBDS 53W069 and 53W091) with $R-K\simgt5.5$ are remarkably similar to those of low-$z$ ellipticals like M~32, and population synthesis modelling of their UV spectra suggests ages of $\sim$~3.5~Gyr for these galaxies. The existence of such old objects at early epochs implies a high formation redshift for massive galaxies, and rules out $\Omega_0 = 1,\ \Lambda_0 = 0$ cosmologies for $H_0 \ge 40~\hnotunit$. At present, the ages of these objects are constrained only by their UV spectra: by $z\sim1$ the more familiar spectral features (such as the 4000\AA\ break) have moved into the near--infrared. Here, we propose to obtain NIRI low-resolution spectra of two $z>1$ radio galaxies (LBDS~53W091 at $z=1.55$ and 3C~239 at $z=1.78$) that are believed to contain intermediate age stellar populations. By obtaining rest--frame optical spectra we will be able to detect at least the well--calibrated age-indicator, the 4000\AA\ break, and possibly the $G$--band ($\sim$4300\AA). The near-IR spectra in combination with existing data will place a much tighter constraint on the ages of both galaxies, and will allow us to compare the stellar contents and ages of two radio galaxies of very different radio power with greater precision than previously possible.
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Last update December 20, 2000; Phil Puxley