paper

Effects of Ram-Pressure from Intracluster Medium on the Star Formation Rate of Disk Galaxies in Clusters of Galaxies

arXiv:astro-ph/9812378 · doi:10.1086/307139

Abstract

Using a simple model of molecular cloud evolution, we have quantitatively estimated the change of star formation rate (SFR) of a disk galaxy falling radially into the potential well of a cluster of galaxies. The SFR is affected by the ram-pressure from the intracluster medium (ICM). As the galaxy approaches the cluster center, the SFR increases to twice the initial value, at most, in a cluster with high gas density and deep potential well, or with a central pressure of because the ram-pressure compresses the molecular gas of the galaxy. However, this increase does not affect the color of the galaxy significantly. Further into the central region of the cluster ( Mpc from the center), the SFR of the disk component drops rapidly due to the effect of ram-pressure stripping. This makes the color of the galaxy redder and makes the disk dark. These effects may explain the observed color, morphology distribution and evolution of galaxies in high-redshift clusters. By contrast, in a cluster with low gas density and shallow potential well, or the central pressure of , the SFR of a radially infalling galaxy changes less significantly, because neither ram-pressure compression nor stripping is effective. Therefore, the color of galaxies in poor clusters is as blue as that of field galaxies, if other environmental effects such as galaxy-galaxy interaction are not effective. The predictions of the model are compared with observations.

19 pages, 9 figures, to appear in ApJ

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