AAS 201st Meeting, January, 2003
Session 55. Instrumental Calibration and Data Analysis Techniques
Poster, Tuesday, January 7, 2003, 9:20am-6:30pm, Exhibit Hall AB

## [55.05] Photometric and astrometric analysis of Gemini Galactic Center observations using StarFinder'' and blind deconvolution packages.

G. Pugliese, J. Christou, R. Koehler (Center for Adaptive Optics), J. Drummond (Air Force Research Laboratory)

We present a study of photometric and astrometric measurements from adaptive optics (AO) observations of a very crowded field. We compare three different techniques to extract the point spread function (PSF) from the field. We primarily investigate the ability of the StarFinder package to generate both the photometric and astrometric measurements and PSFs. These results are compared with those obtained using blind deconvolution techniques.

Techniques which extract the PSF from the AO observations of very crowded fields are important because there are no isolated stars which can be used for PSF calibration necessary for the photometric and astrometric analysis of the field. A reference star measurement will not always produce a satisfactory calibration PSF. Therefore alternative methods have to be used to extract the PSF from the data itself.

We measured the photometry and astrometry of four 4.8\prime\prime isoplanatic sub-fields from the Gemini/Hokupa'a observations of the Galactic Center. Both StarFinder and blind deconvolution extract the numerical PSF directly from the data. The parametric blind deconvolution extracts an analytic PSF. The photometry and astrometry were obtained from StarFinder using both numerical PSFs and also measured from the blind deconvolution results. The results from these analyses are compared. The performance of these algorithms depends upon the quality of the AO compensation.

We also generated a synthetic field of this region to test the accuracy of each technique and to investigate the performance of each algorithm to recover the relative photometry. We find that StarFinder results show a systematic offset for magnitude differences greater than ~ 4.

This work has been supported by the National Science Foundation Science and Technology Center for Adaptive Optics, managed by the University of California at Santa Cruz under cooperative agreement No. AST - 9876783.