Surface photometry and structure of high redshift disk galaxies in the HDF-S NICMOS field

Abstract

Aims.We report on a photometric study of a sample of 22 disk galaxies in the Hubble Deep Field South NICMOS parallel field. The redshift range of the galaxies is z=0.5{-}2.6.Methods.We use deep NICMOS J and H band and STIS open mode images, taken as part of the HDF-S project, to construct rest-frame B-profiles and (U-V) color profiles of the galaxies. Before fitting isophotes, images are deconvolved with PSF. Derived surface brightness profiles are approximated by Sérsic luminosity distribution.Results.Significantly large population of disks cannot be represented by an exponential disk, but this can be well done by Sérsic law, if n<1. This might be the same phenomenon which has earlier been referred to as truncation of disks. Parameter n does not vary significantly with redshift. Galactic sizes decrease with redshift as r_e(z)/r_e(0) = 1-0.26z. The rest frame (U-V) color shows a clear decrease at z≈2, concordantly with the understanding of more intense star formation at earlier epochs. Color gradients Δ(U-V)/Δ r are small and roughly constant at z<2. At z>2, dominantly positive gradients appear, possibly indicating centrally concentrated star-formation. On the basis of (U-V) color and chemical evolution models, the disks observed at z∼ 2.5 have formed between z=3.5{-}7. Scale radii r_e of the galaxies correlate with the scale surface brightnesses μ_e for the sample. None of the studied parameters shows clear dependence on absolute B luminosity for the galaxies.