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

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 ∼ 10 −2 cm −3 keV 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 ( ∼ < 1 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 ∼ 10 −3 cm −3 keV, 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.

Dissipative phenomena in extended-body interactions

“…of the orbital motions has to be explored. Therefore, we prefer to follow the method proposed by Fujita (1998) and Fujita & Nagashima (1999), from whom we take the model of star formation to be integrated by extensive calculations of orbital motions and synthetic CMDs of the stellar content of the dwarf galaxy. In brief, stars are known to form in gas clouds (either atomic or molecular) whose mass distribution is uncertain but believed to span at least a factor ∼10 6 in mass (Elmegreen & Efremov 1997).…”

Galaxy evolution in merging clusters: The passive core of the “Train Wreck” cluster of galaxies, A 520

“…Their effects are expected to be akin to the effects that virialised clusters have on their constituent galaxies, although both ram pressure stripping and tidal interaction can be significantly strengthened in merging clusters due to the usually very high velocities involved, the structured ICM and the clumpy gravitational potential (Tonnesen et al 2007;Tonnesen & Bryan 2008;Kapferer et al 2008). There is still an ongoing debate as to whether the onset of environmental effects, which ultimately quenches star formation, is accompanied by initial, short lived star burst (Vollmer et al 2001;Bekki & Couch 2003;Fujita & Nagashima 1999;Poggianti et al 2008;Henderson & Bekki 2016). One additional physical mechanism acting on galaxies in merging clusters is the shock waves propagating through the ICM (Roediger et al 2014).…”

Local Environmental Dependence of Galaxy Properties in a Volume-Limited Sample of Main Galaxies

“…Many authors have investigated correlations between environment and galaxy properties, such as ones between environment and morphology (e.g., Postman & Geller 1984;Dressler et al 1997;Hashimoto & Oemler 1999;Fasano et al 2000;Tran et al 2001;Goto et al 2003;Helsdon & Ponman 2003;Treu et al 2003), ones between environment and star formation rate (e.g., Hashimoto et al 1998;Lewis et al 2002;G´omez et al 2003;Balogh et al 2004a;Tanaka et al 2004;Kelm, Focardi & Sorrentino 2005), and ones between environment and colour (e.g., Tanaka et al 2004;Balogh et al 2004b;Hogg et al 2004). In order to explain these correlations, various physical mechanisms have been proposed, including rampressure stripping (Gunn & Gott 1972;Kent 1981;Fujita & Nagashima 1999;Quilis, Moore & Bower 2000); galaxy harassment (Moore et al 1996(Moore et al , 1999; cluster tidal forces (Byrd &Valtonen 1990;Valluri 1993;Gnedin 2003); and interaction/merging of galaxies (Icke 1985;Lavery & Henry 1988;Mamon 1992;Bekki 1998).…”