Simulations of Deep Optical and Near Infrared Extragalactic Counts

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Session 67 -- Galaxy Clusters and the Extragalactic Distance Scale
Oral presentation, Thursday, 10:30-12:00, Zellerbach Auditorium Room

[67.05] Simulations of Deep Optical and Near Infrared Extragalactic Counts

Carol Lonsdale, A. Chokshi (IPAC), P. Mazzei, G. De Zotti (Padova)

Monte-Carlo simulations of three dimensional galaxy distributions are performed to study the photometric properties of evolving galaxy populations in the optical and near infrared bands to high redshifts. Galaxies are spatially distributed in a range of cluster to field environments. Details of individual galaxy properties, including luminosities, morphologies, disk-to-bulge ratios, and size distributions are simulated to match local observed galaxy properties. Galaxies have evolving spectral energy distributions that include both stellar emission and internal dust absorption and re-emission. The simulations result in two dimensional galaxy distributions on the sky that can be compared to the observed deep images in the blue and near-infrared bands. In this paper, the first of a series, we present our baseline model in which galaxy numbers are conserved, and in which no explicit ``starburst'' population is included. We find that our baseline models, with a formation redshift, z$_f$, of 1000, and $H_o$=50, are able to reproduce the observed blue counts to $b_j=$22, independent of the value of $\Omega_o$, and also to provide a satisfactory fit to the observed blue band redshift distributions, but for neither value of $\Omega_o$ do we achieve an acceptable fit to the fainter blue counts. In the K-band, we fit the number counts to the limit of the present day surveys only for an $\Omega_o=0$ cosmology. We investigate the effect on the model fits of varying $H_o$, z$_f$, and the local luminosity function. Reducing $z_f$ to $\simeq$ 5 in a low $\Omega_o$ universe improves the fit to the faintest photometric blue data without any need to invoke a new population of galaxies, substantial merging, or a significant starburst galaxy population. For an $\Omega_o$=1 universe, however, reducing $z_f$ is less successful at fitting the blue band counts, and has little effect at all at K. Varying the parameters of the local luminosity function can also have a significant effect. In particular the steep low end slope of the local luminosity function of Franceschini et al. allows an acceptable fit to the $b_j\leq 25$ counts for $\Omega_o=1$, but is incompatible with $\Omega_o=0$.

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