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تسجيل مستخدم جديدStrangulation in Galaxy Groups
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We use a cosmological chemodynamical simulation to study how the group environment impacts the star formation properties of disk galaxies. The simulated group has a total mass of M~8x10^12 Msun and a total X-ray luminosity of L_X~10^41 erg s^-1. Our simulation suggests that ram pressure is not sufficient in this group to remove the cold disk gas from a V_rot~150 km s^-1 galaxy. However, the majority of the hot gas in the galaxy is stripped over a timescale of approximately 1 Gyr. Since the cooling of the hot gas component provides a source for new cold gas, the stripping of the hot component effectively cuts off the supply of cold gas. This in turn leads to a quenching of star formation. The galaxy maintains the disk component after the cold gas is consumed, which may lead to a galaxy similar to an S0. Our self-consistent simulation suggests that this strangulation mechanism works even in low mass groups, providing an explanation for the lower star formation rates in group galaxies relative to galaxies in the field.
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Galaxy clusters have long been theorised to quench the star-formation of their members. This study uses integral-field unit observations from the $K$-band Multi-Object Spectrograph (KMOS) - Cluster Lensing And Supernova survey with Hubble (CLASH) sur
vey (K-CLASH) to search for evidence of quenching in massive galaxy clusters at redshifts $0.3<z<0.6$. We first construct mass-matched samples of exclusively star-forming cluster and field galaxies, then investigate the spatial extent of their H$alpha$ emission and study their interstellar medium conditions using emission line ratios. The average ratio of H$alpha$ half-light radius to optical half-light radius ($r_{rm{e},rm{H}alpha}/r_{rm{e},R_c}$) for all galaxies is $1.14pm0.06$, showing that star formation is taking place throughout stellar discs at these redshifts. However, on average, cluster galaxies have a smaller $r_{rm{e},rm{H}alpha}/r_{rm{e},R_c}$ ratio than field galaxies: $langle r_{rm{e},rm{H}alpha}/r_{rm{e},R_c}rangle = 0.96pm0.09$ compared to $1.22pm0.08$ (smaller at a 98% credibility level). These values are uncorrected for the wavelength difference between H$alpha$ emission and $R_c$-band stellar light, but implementing such a correction only reinforces our results. We also show that whilst the cluster and field samples follow indistinguishable mass-metallicity (MZ) relations, the residuals around the MZ relation of cluster members correlate with cluster-centric distance; galaxies residing closer to the cluster centre tend to have enhanced metallicities (significant at the 2.6$sigma$ level). Finally, in contrast to previous studies, we find no significant differences in electron number density between the cluster and field galaxies. We use simple chemical evolution models to conclude that the effects of disc strangulation and ram-pressure stripping can quantitatively explain our observations.
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