Open AccessEffects of the UV background radiation on galaxy formation
Author(s) -
Nagashima Masahiro,
Gouda Naoteru,
Sugiura Norimasa
Publication year - 1999
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1046/j.1365-8711.1999.02438.x
Subject(s) - physics , astrophysics , galaxy , background radiation , astronomy , redshift , dwarf galaxy , star formation , galaxy formation and evolution , stars , radiation , optics
We investigate the effects of the UV background radiation on galaxy formation by using the semi‐analytic model including the photoionization process. The semi‐analytic model is based on Cole et al. and we use almost the same parameters as their `fiducial' model. We find that the UV background mainly affects the formation of dwarf galaxies when J ‐21 ≡ 1 (J ≳ J ‐21 × 10 ‐21 erg cm ‐2 s ‐1 sr ‐1 Hz ‐1 , J is the intensity of the UV background). Because of the suppression of star formation, the number density of small objects corresponding to dwarf galaxies decreases compared with the case of no UV radiation when the UV background exists until the present epoch. On the contrary, the UV radiation hardly affects massive galaxies. This is because the massive galaxies are formed by mergers of small galaxies, which are formed at high redshift when the effect of the UV background is negligible. This strongly suggests that it is important to consider the merging histories of the galaxies. On the other hand, when the UV background vanishes at a low redshift (z ∼ 2), the number density of small objects is hardly changed but the colour becomes bluer, compared with the case of no UV radiation, because stars are newly formed after the UV background vanishes. Moreover, we show the redshift evolutions of the luminosity functions and the colour distributions of galaxies. Because the effect of the UV background is strong at low redshift, we can discriminate between the types of evolution of the UV background by observing the evolution of the luminosity function and the colour distributions, if the UV intensity is sufficiently strong ( J −21 1).