Structure of visible and dark matter components in spiral galaxies at redshifts z = 0.5-0.9

Abstract

We have constructed self-consistent light and mass distribution models for four disk galaxies at redshifts z = 0.48, 0.58, 0.81 and 0.88, using the HST archive WFPC2 observations (HDF-S, MDS, Groth Strip survey) and rotation curves measured by Vogt et al. (1996) and Rigopoulou et al. (2002). The models consist of three components: a bulge, a disk and a dark matter halo. Similarly to the sample studied in Paper I (Tamm & Tenjes 2003), light distribution of the galaxies in the outer parts is clearly steeper than a simple exponential disk. After applying k-corrections, calculated mass-to-light ratios for galactic disks within the maximum disk assumption are M/LB = 0.9, 7.4, 4.3 and 1.4, respectively. Together with the galaxies from Paper I, the mean 〈M/L B〉 = 2.5 at 〈z〉 ≃ 0.9, indicating no significant evolution of M/LB with redshift. Central densities of dark matter halos for an isothermal model are 0.008, 0.035, 0.013, and 0.022 in units M ⊙/pc3, respectively. Together with the galaxies from Paper I, the DM central density of the four galaxies at mean readshift 〈z〉 ≃ 0.9 is ρ(0) = (0.012-0.028) M⊙/pc 3, also showing no significant evolution with redshift. We have also constructed mass distribution models without assuming flat rotation curves and without a dark matter component. Due to the limited extent of the observed rotation, the models without a dark halo nearly fit the observations. In this case, mass-to-light ratios for the galactic disks are 1.8, 9.7, 12. and 1.9, respectively. © ESO 2005.