We present new deep spectroscopic observations of 0.05--0.5 L_* galaxies in one cluster (cl1232.5-1250) drawn from the ESO Distant Cluster Survey (EDisCS) sample, at z = 0.54. The new data extend the spectroscopy already available for this cluster by about 1 magnitude. The cluster has a large fraction of passive galaxies and exhibits a well defined and relatively tight colour-magnitude relation. Among spectroscopic members, only six galaxies are classified as `post-starburst' (k+a). For another EDisCS cluster at similar redshift and with as deep spectroscopy, no member is found to have a k+a spectrum. The low measured numbers of post-starburst systems appear to be inadequate to explain the observed increase of faint red galaxies at lower redshift, even when accounting for the infall of new galaxies onto the cluster. Post-starburst galaxies represent a possible channel to move galaxies from the blue star-forming cloud to the red-sequence, but the available data suggest this is not the dominant channel in galaxy clusters. If the galaxies at the faint end of the red-sequence in nearby clusters originate from the blue galaxies observed in distant galaxy clusters, the transformation must have occurred primarily through physical processes that do not lead to a post-starburst phase. In addition, our data exclude a large population of k+a galaxies at faint magnitudes, as found in the Coma cluster.
Building the red sequence through gas-rich major mergers
了解红色序列是如何构建的细节是星系演化中的一个关键问题。富气合并与干合并、大合并与小合并或星系合并与气体吸积的相对作用是什么?在Wild et al. 2009中,我们将流体动力学模拟与观测结果进行了比较,以显示富含气体的主要合并如何导致具有强烈的星暴后光谱特征的星系,这是一个很容易在真实宇宙中使用光谱识别的星系群。使用光谱从VVDS深调查z~0.7,和主成分分析技术,以提供足够高的SNR的指标,我们发现,40%的红序列的质量流量可以通过一个强大的后星爆阶段,从而通过丰富的气体主要合并。下一代星系红移巡天提供的更深层次的样本将使我们能够观察到导致恒星形成停止和红色序列形成的主要物理过程。
Mass and metal ejection efficiency in disk galaxies driven by young stellar clusters of nuclear starburst
我们目前的结果从模型驱动的能量注入核星爆的星系风。星暴的总能量由年轻的中心星团提供,部分银河星际介质作为银河风的一部分被推出(在某些情况下,银河风包含新一代恒星产生的金属的重要部分)。我们已经进行了绝热和辐射的三维N体/光滑粒子流体动力学模拟银河风使用GADGET-2代码。数值模型涵盖了大范围的恒星暴(从$\sim10^2$到$\sim10^7$ M $_\odot$)和星系气体质量(从$\sim6\times10^6$到$\sim10^{11}$ M $_\odot$)。集中的中央星暴区是星系中产生质量和金属损失的有效引擎,也是驱动星系中金属重新分布的有效引擎。
Starburst galaxies at the peak of cosmic star formation are among the most extreme starforming engines in the universe, producing stars over ~100 Myr. The star formation rates of these galaxies, which exceed 100 $M_\odot$ per year, require large reservoirs of cold molecular gas to be delivered to their cores, despite strong feedback from stars or active galactic nuclei. Starburst galaxies are therefore ideal targets to unravel the critical interplay between this feedback and the growth of a galaxy. The methylidyne cation, CH$^+$, is a most useful molecule for such studies because it cannot for…
We compare observed far infra-red/sub-millimetre (FIR/sub-mm) galaxy spectral energy distributions (SEDs) of massive galaxies ($M_{\star}\gtrsim10^{10}$ $h^{-1}$M$_{\odot}$) derived through a stacking analysis with predictions from a new model of galaxy formation. The FIR SEDs of the model galaxies are calculated using a self-consistent model for the absorption and re-emission of radiation by interstellar dust based on radiative transfer calculations and global energy balance arguments. Galaxies are selected based on their position on the specific star formation rate (sSFR) - stellar mass ($M_…
This work uses multiscale environments and structures of galaxies in the Sloan Digital Sky Survey as consistency checks of the evolution from starburst to quiescence at redshift $z < 0.2$. The environmental indicators include fixed aperture mass overdensities ($δ_{x\mathrm{Mpc}}$, $x \in \{0.5, 1, 2, 4, 8\}\,h^{-1}$Mpc), $k$-nearest neighbor distances, the tidal parameter, halo mass ($M_h$), and satellite/central classification. The residuals of specific star formation rates ($Δ\,\mathrm{SSFR}$) is used to select starbursts ($Δ\,\mathrm{SSFR} > 0.6\,$dex, $N \approx 8,\,600$). Quenched post-st…
We use higher-redshift gamma-ray burst (GRB), HII starburst galaxy (HIIG), and quasar angular size (QSO-AS) measurements to constrain six spatially flat and non-flat cosmological models. These three sets of cosmological constraints are mutually consistent. Cosmological constraints from a joint analysis of these data sets are largely consistent with currently-accelerating cosmological expansion as well as with cosmological constraints derived from a combined analysis of Hubble parameter ($H(z)$) and baryon acoustic oscillation (BAO, with Planck-determined baryonic matter density) measurements. …