Deep H-band Galaxy Counts and Half-light Radii from HST/NICMOS Parallel Observations

Abstract

We present deep galaxy counts and half-light radii from F160W ($\hat{I}{»}_c=1.6\hat{I}¼$) images obtained with NICMOS on HST. Nearly 9 arcmin${}^2$ have been imaged with camera 3, with $3\ddot{I}ƒ$ depths ranging from H = 24.3 to 25.5 in a 0.6${}^{\prime \prime }$ diameter aperture. The slope of the counts fainter than H~$=20$ is 0.31, and the integrated surface density to H$\le 24.75$ is $4\times 10^5$ galaxies per square degree. The half-light radii of the galaxies declines steeply with apparent magnitude. At H~$=24$ we are limited by both the delivered FWHM and the detection threshold of the images.

8 pages. Accepted for publication in ApJ Letters