NICMOS PHOTOMETRIC CALIBRATION PROGRAM (M. Rieke)

PRIMARY GOALS:

1 - Relative flux references accurate to 1.5% for standard photometry

2 - Color transformations between groundbased and NICMOS systems

3 - Relative absolute wavelength & spectrophotometric references for Grisms

4 - Polarization standards

Relative Photometric Calibration

EXISTING GROUND-BASED STANDARD STAR LISTS ARE INADEQUATE

* Dirth of suitable observations to rule out low-level NIR variability for most stars.

* Large numbers of well-measured stars are not available in J,H,K

Strategy:

Select & measure stars for flux references, color transformations and interpolation across opaque atmospheric windows. We are using solar analogs as the main flux references to bridge the gaps in atmospheric transmissivity.

* Dispersion in NIR colors is very small in G-stars

* Minimun number of strong spectral features in NIR

* Solar spectrum available throughout range of NICMOS sensitivity

Target Selections:

1) SOLAR ANALOGS: From HST Guide Star Photometric Survey (Lasker & Sturch)

a) 0.55 < B-V < 0.72 Screen for solar analogues

b) 10.5 < Kest < 12.3 (emperical relation used for Kest)

c) E(B-V) < 0.05 (Minimal extinction, Burnstein & Heiles reddening maps)

Prioritize selection based upon HST Guide Star Availability/Suitability Windows

2) M-DWARFS: w/o H[[alpha]] (non-variable) with V-K <= 8 for color transformations. (VRIJHK observations being made and will be checked for IRAS fluxes)

3) Several WHITE DWARFS used as on-orbit HST calibrators for other SIs added. (HZ44, Feige 66, and G191B2B have already been observed at least once)

Procedure:

Cross-calibrate using Elias et al. (1982, AJ, 87, 1029) list.

Observe prioritized targets on at least 5 nights (screen for variables at 1.5% level)

Northern Hemisphere: NICMOS2 array on Mt. Lemmon 60" & Kitt Peak 90"

Southen Hemisphere: NICMOS3 array on Las Campanas 40"

NICMOS Standard Star List


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