2002A Gemini North Classical Program Abstracts

Abstracts for all successful 2002A classical programs are given below.

GN-2002A-C-1

Title: A Search for Circumstellar Disks in the TW Hydrae Association}

Abstract: Using a speckle noise suppressing dual imaging polarimetry technique, we propose to search for new circumstellar disks around stars in the TW Hydrae association (d~50pc). This high dynamic range imaging technique achieves a sensitivity significantly closer to the photon noise limit for polarized light by contrasting two Point Spread Functions (PSFs) recorded simultaneously, but with one having an orthogonal polarization relative to the other. The observations will provide measurements of the scale height, viewing inclination, size, morphology, and dust content in the newly detected disks, and will provide meaningful constraints on the dust content in the case of a null detection. The high dynamic range adaptive optics observations proposed here would also be sensitive to the detection of faint companions around this interesting sample of young, nearby stars.

GN-2002A-C-2

Title: An Adaptive Optics Search for Young Jovian-Mass Planets

Abstract: We propose to conduct an imaging survey for Jovian-mass planets around young solar-type stars using Gemini AO. By choosing pre-main sequence stars, we significantly enhance our sensitivity to very low masses. Analysis of real AO data demonstrate the feasibility of detecting Jupiter-mass companions at sub-arcsecond separations.

GN-2002A-C-3

Title: AO studies of high-z radio source hosts with bright natural guide stars

Abstract: We propose targeted studies of a sample of distant radio sources that have bright (m<14) foreground stars within the isoplanatic patch (~20"). This sample of radio galaxies can be observed with the new generation of adaptive optics instruments on 8-10 meter class telescopes with 50 milliarcsecond resolution and Strehl ratios of up to 0.5 or better. With the AO systems now available it will be possible to obtain two-dimensional surface brightness profiles and color gradients of the most distant and reddest galaxies. Spatially resolved infrared polarimetry will probe the dust content of these objects and its evolution with redshift. Dust scattering models of HzRGs predict that the fuzz around QSRs will show detectable polarization - this will test the orientation scheme for dust scattering in high redshift radio sources. The vast improvement in capability provided by AO with natural guide stars provides a crucial tool to advance studies of high-z radio galaxies.

GN-2002A-C-4

Title: Brown Dwarf Meteorology

Abstract: We have embarked on an international collaboration involving several telescopes in Hawaii, Arizona, France and the Canary Islands. We plan to monitor the brightness variations of a sample of 14 L dwarfs over a 4 day period using I,J,K and L photometry as well as IR spectroscopy. Mauna Kea telescopes will play a leading role in this collaboration. The proposed observations will provide information of the properties of the clouds, such as patchiness and vertical distribution. The Gemini North NIRI observations will be used to monitor the L-band brightness of four L dwarfs.

GN-2002A-C-5

Title: NIR Spectroscopy and Optical Photometry of faint Centaurs

Abstract: This program seeks to characterize the physical surface properties of fainter Centaurs, obtaining their spectra and comparing them with the surface spectra of other outer solar system bodies we have obtained. Recent spectroscopic studies yield evidence for spectral diversity in both KBOs and Centaurs. However, Centaurs are nearer and generally brighter than KBOs and are therefore more accessible to spectroscopic observations. If the Centaurs' origin is the Kuiper belt, as suspected, then their study will shed light on the nature of KBOs as well. We plan also to image the even fainter Centaurs not accessible to spectroscopy in the J, H and K bands using NIRI to obtain their NIR colors. Only the Gemini telescope with NIRI can obtain NIR spectra and photometry of bodies so faint during the time we request, allowing us to achieve adequate S/N with the resolution required to discern spectral solid-state features. Identification of the ices and organic components in their surface materials, when compared with the satellites and comet nuclei and interpreted with information about their dynamical history, will help piece together the chemical evolution of the outer solar system. We request UH 2.2m optical observing time concurrent with our Gemini NIR spectroscopy time in order to decouple optical absorption features with the NIR spectral absorption features we observe, and hopefully distinguish variations in brightness owing to projected surface area and rotation from actual surface spectral features.

Last update January 15, 2002; Phil Puxley