Hubble Space Telescope Medium Deep Survey. II. Deconvolution of Wide Field Camera field galaxy images in the 13^h+43° field

We present isophotal profiles of six faint field galaxies from some of the first deep images taken for the Hubble Space Telescope (HST) Medium Deep Survey (MDS). These have redshifts in the range z=0.126-0.401. The images were taken with the Wide Field Camera (WFC) in "parallel mode" and deconvolved with the Lucy method using as the point-spread function nearby stars in the image stack. The WFC deconvolutions have a dynamic range of 16-20 dB (4-5 mag) and an effective resolution ≲0″.2 (FWHM). The multiorbit HST images allow us to trace the morphology, light profiles, and color gradients of faint field galaxies down to V≃22-23 mag at sub-kpc resolution, since the redshift range covered is z=0.1-0.4. The goals of the MDS are to study the sub-kpc scale morphology, light profiles, and color gradients for a larger sample of faint field galaxies down to V≃23 mag, and to trace the fraction of early to late-type galaxies as function of cosmic time. In this paper we study the brighter MDS galaxies in the 13^h+43° MDS field in detail, and investigate to what extent model fits with pure exponential disks or a^1/4 bulges are justified at V≲22 mag. Four of the six field galaxies have light profiles that indicate (small) inner bulges following r^1/4 laws down to 0″.2 resolution, plus a dominant surrounding exponential disk with little or no color gradients. Two occur in a group at z=0.401, two are barred spiral galaxies at z=0.179 and z=0.302, and two are rather subluminous (and edge-on) disk galaxies at z=0.126 and z=0.179. Our deep MDS images can detect galaxies down to V, I≲25-26 mag, and demonstrate the impressive potential of HST - even with its pre-refurbished optics - to resolve morphological details in galaxies at cosmologically significant distances (V≲23 mag). Since the median redshift of these galaxies is ≲0.4, the HST resolution allows us to study sub-kpc size scales at the galaxy, which cannot be done with stable images over wide fields from the best ground-based sites.