Near‐Infrared Faint Galaxies in the Subaru Deep Field: Comparing the Theory with Observations for Galaxy Counts, Colors, and Size Distributions to K ∼ 24.5

Abstract

Galaxy counts in the K band, ( J-K) colors, and apparent size distributions of faint galaxies in the Subaru Deep Field (SDF) down to K ~ 24.5 were studied in detail. Special attention has been paid to take into account various selection effects, including the cosmological dimming of surface brightness, to avoid any systematic bias that may be the origin of controversy in previously published results. We also tried to be very careful about systematic model uncertainties; we present a comprehensive survey of these systematic uncertainties and dependence on various parameters, and we have shown that the dominant factors to determine galaxy counts in this band are cosmology and number evolution. We found that the pure luminosity evolution (PLE) model is very consistent with all the SDF data down to K ~ 22.5, without any evidence for number or size evolution in a low-density, Λ-dominated flat universe, which is now favored by various cosmological observations. On the other hand, a number evolution of galaxies with η ~ 2, when invoked as the luminosity conserving mergers as ##IMG## [http://ej.iop.org/icons/Entities/phi.gif] {phi} * ##IMG## [http://ej.iop.org/icons/Entities/vprop.gif] {vprop} (1 + z ) η and L * ##IMG## [http://ej.iop.org/icons/Entities/vprop.gif] {vprop} (1 + z ) -η for all types of galaxies, is necessary to explain the data in the Einstein-de Sitter universe. If the popular Λ-dominated universe is taken for granted, our result then gives a strong constraint on the number evolution of giant elliptical or early-type galaxies to z ~ 1-2 that must be met by any models in the hierarchically clustering universe, since such galaxies are the dominant population in this magnitude range ( K ##IMG## [http://ej.iop.org/icons/Entities/lesssim.gif] {lesssim} 22.5). A number evolution with η ~ 1 is already difficult to reconcile with the data in this universe. On the other hand, number evolution of late-type galaxies and/or dwarf galaxies, which has been suggested by previous studies of optical galaxies, is allowed from the data. In the fainter magnitude range of K ##IMG## [http://ej.iop.org/icons/Entities/gtrsim.gif] {gtrsim} 22.5, we found a slight excess of observed counts over the prediction of the PLE model when elliptical galaxies are treated as a single population. We suggest that this discrepancy reflects some number evolution of dwarf galaxies and/or the distinct populations of giant and dwarf elliptical galaxies which have been known for local elliptical galaxies.