论文标题
跨环境的星系进化，如中央和卫星星系的年龄，恒星金属性和[alpha/fe]
Galaxy evolution across environments as probed by the ages, stellar metallicities and [alpha/Fe] of central and satellite galaxies
论文作者
论文摘要
我们探讨了当今星系的恒星形成和金属富集历史如何受到SDSS DR7的恒星种群参数估计和组环境表征的影响。我们比较了卫星和中央星系的恒星年龄，恒星金属和元素丰度比[alpha/fe]，这是其恒星和宿主组晕圈质量的函数，可控制当前的恒星形成速率和输入时期。我们确认下面的log（MSTAR/MSUN）= 10.5卫星比同等质量的中央星系较老，金属富毛。相反，我们没有检测到其[alpha/fe]的任何差异：这主要取决于恒星质量，而不是群体层次结构或宿主晕质量。我们还发现，在10^{10.5}以下的恒星质量的卫星和中心的中位年龄和金属性的差异很大程度上是由于卫星中无源星系的较高部分以及作为光晕质量的功能。我们认为，低质量的观察到的趋势以“延迟 - 重度”的方式揭示了卫星特异性环境效应的作用。当考虑到不同的静态分数，年龄较小的剩余过量，金属性和[alpha/fe]的卫星出现时，与同等大量的中央星系相比，以旧恒星种群为主的卫星，居住在光晕中，居住在光环中。这种过多的年龄，金属性和[alpha/fe]与古老的输入者有关，即已在5个以上的Gyr上积聚到当前光环上的卫星。该结果表明，环境在恒星形成的早期星系中的作用在接近宇宙密度峰的星系中。
We explore how the star formation and metal enrichment histories of present-day galaxies have been affected by environment combining stellar population parameter estimates and group environment characterization for SDSS DR7. We compare stellar ages, stellar metallicities and element abundance ratios [alpha/Fe] of satellite and central galaxies, as a function of their stellar and host group halo mass, controlling for the current star formation rate and for the infall epoch. We confirm that below log(Mstar/Msun)=10.5 satellites are older and metal-richer than equally-massive central galaxies. On the contrary, we do not detect any difference in their [alpha/Fe]: this depends primarily on stellar mass and not on group hierarchy nor host halo mass. We also find that the differences in the median age and metallicity of satellites and centrals at stellar mass below 10^{10.5}Msun are largely due to the higher fraction of passive galaxies among satellites and as a function of halo mass. We argue that the observed trends at low masses reveal the action of satellite-specific environmental effects in a `delayed-then-rapid' fashion. When accounting for the varying quiescent fraction, small residual excess in age, metallicity and [alpha/Fe] emerge for satellites dominated by old stellar populations and residing in halos more massive than 10^{14}Msun, compared to equally-massive central galaxies. This excess in age, metallicity and [alpha/Fe] pertain to ancient infallers, i.e. satellites that have accreted onto the current halo more than 5 Gyr ago. This result points to the action of environment in the early phases of star formation in galaxies located close to cosmic density peaks.
