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The values in these tables are based on results from the FLAMINGOS-2 Integration Time Calculator and from the early commissioning runs. They assume 70-percentile (IQ70, ~average) image quality for all categories, photometric conditions (CC50), and an airmass of less than 1.2 for the sensitivites presented here. Water vapor has little impact on the near-IR imaging sensitivity, or on spectroscopic sensitivity in the middles of the J, H, and K windows, but does significantly effect the edges of the JHK windows where absorption by telluric water vapor is strong. The estimates also use the measured telescope, camera, and detector performances. Note that some sky conditions vary outside of those stated above. For example, OH emission, although scaled by airmass, can intrinsically vary by over a factor of two from night to night and over much shorter timescales - which can alter S/N and sensitivity by +/- sqrt2 in the J, H, and K bands. Thus observers should use both the table and the ITC with some caution and conservatism.
Regarding readout noise, note that JHKs imaging used CDS readout.
|FLAMINGOS-2 IMAGING SENSITIVITY (S/N=5 IN 1 HOUR, N.I. OVERHEADS)|
|Filter||Center wavelength (µm)||(mag)||Individual Exposure Time (sec)|
|Y||1.02||22.2 (in J)||300
- For imaging, the ITC calculates the S/N in an aperture that maximizes S/N, given the predicted image quality for the observing conditions and wavelength requested. The sensitivity values in the table below use this optimum ITC aperture. For accurate photometry much larger apertures usually must be used, and sensitivities are reduced, typically by a factor of 2 or more.
- Approximate total throughput values in the imaging table are as measured for the entire system, including the telescope, instrument, and detector.
|FLAMINGOS-2 SPECTROSCOPIC SENSITIVITY FOR POINT SOURCES (S/N=5 IN 1 HOUR, N.I. OVERHEADS)|
|Grism||Filter||slit width (arcsec)||(mag)|
| JH (1200)
|HK (1200)||HK||0.36||20.5 (Ks)
Photometric Zero points
The zero points for the photometric MKO system were obtained using 88 independent data points from standard stars observations made during the three commissioning runs of May through July 2013.
Y = 25.12 - 0.01*k + 0.50*(Y-J) ± 0.03
J = 25.21 - 0.02*k + 0.87*(J-H) ± 0.05
H = 25.42 - 0.01*k + 0.73*(J-H) ± 0.05
Ks= 24.64 - 0.05*k - 0.27*(H-Ks) ± 0.06
(where k is the extinction coefficient.)