我们从Goto的E+A星系目录中挑选出35个最亮的星系，这些星系是从Sloan Digital Sky Survey Data Release 5中选出的。E+As的光谱特征是具有强的Balmer吸收线，而很少有[Oii]或H_α发射线。在这项工作中，我们研究了恒星星族的样本星系的光谱拟合ULySS，这是一个强大的全谱拟合方法。我们分别用单星族（一个恒星星族-一个SSP）和三星族（3个SSP）模型拟合每个样本。通过1-人口拟合，我们得到的SSP等效年龄和金属丰度对应的“亮度加权”的平均值。通过3-总体拟合，将组分按年龄分为3组（老恒星星族-OSP、中龄恒星星族-ISP和年轻恒星星族-YSP），得到了OSP、ISP和YSP的最佳年龄、金属丰度和质量分数和质量分数。在拟合过程中，Pegase.HR/Elodie 3.1和Vazdekis/Miles均用作两个独立的总体模型。两个模型的结果基本一致：对于所有样本星系，YSP（< 1Gyr）对光的贡献都很大。然而，质量的主要贡献者是OSP。我们还重建平滑的恒星形成历史（SFHS），给出恒星形成率（SFR）与演化年龄。此外，我们还对E+A样本和随机选取的34个椭圆星系进行了2-population（2 SSP）模型拟合。我们得到的E+A样本和椭圆星系的老组件的等效年龄。相比之下，E+As的老成分在统计上比椭圆星系的老成分年轻得多。从恒星星族年龄的角度来看，这可能为从E+As到早期类型（E/S 0 s）的进化联系提供了证据。
英文摘要：
We pick out the 35 brightest galaxies from Goto's E+A galaxies catalogue which are selected from the Sloan Digital Sky Survey Data Release 5. The spectra of E+As are prominently characterized by the strong Balmer absorption lines but little [Oii] or H_alpha emission lines. In this work we study the stellar populations of the sample galaxies by fitting their spectra using ULySS, which is a robust full spectrum fitting method. We fit each of the sample with 1-population (a single stellar population-a SSP) and 3-population (3 SSPs) models, separately. By 1-population fits, we obtain SSP-equivalent ages and metallicities which correspond to the `luminosity-weighted' averages. By 3-population fits, we divide components into three groups in age (old stellar population-OSP, intermediate-age stellar population-ISP, and young stellar population-YSP), and then get the optimal age, metallicity and population fractions in both mass and light for OSP, ISP and YSP. During the fits, both Pegase.HR/Elodie3.1 and Vazdekis/Miles are used as two independent population models. The two models result in generally consistent conclusions as follows: for all the sample galaxies, YSPs (< 1Gyr) make important contributions to the light. However, the dominant contributors to mass are OSPs. We also reconstruct the smoothing star formation histories (SFHs) by giving star formation rate (SFR) versus evolutionary age. In addition, we fit the E+A sample and 34 randomly selected elliptical galaxies with 2-population (2 SSPs) model. We obtain the equivalent age of old components for each of the E+A sample and elliptical galaxies. By comparison, the old components of E+As are statistically much younger than those of ellipticals. From the standpoint of the stellar population age, this probably provides an evidence for the proposed evolutionary link from E+As to early-types (E/S0s).
The properties of Brightest Cluster Galaxies in the SDSS DR6 adaptive matched filter cluster catalogue
我们研究了基于自适应匹配滤波器技术（AMF，Szabo等人，2010年）。我们的样本包括超过14300个星系的红移范围为0.1-0.3。我们测试的目录显示，它包括著名的BCGs在于SDSS足迹。我们的特征BCGs的r-波段光度和光学颜色，以及它们的红移趋势。特别是，我们定义和研究的蓝色BCGs的分数，即那些可能会错过基于颜色的聚类调查和目录。较富裕的集群往往有更明亮的BCG，但不那么占主导地位，比穷人的系统。我们的BCG中有4-9%的BCG在g-r色上至少比红序列在它们给定的红移上蓝0.3等。对于丰度高于50的簇，这样的分数降低到1-6%，其中3%的BCGs低于红色序列0.5等。初步的形态学研究表明，在较低的丰度蓝色部分的增加可能有一个不可忽视的贡献，从螺旋星系。我们表明，基于g-r红色序列或基于颜色u-r >2.2的切割的颜色选择可能导致错过大多数这样的蓝色BCGs。我们还将颜色分析扩展到紫外线范围，将我们的产品目录与Galex GR 4和GR 5的公开数据进行交叉匹配。我们显示了一个明确的相关性从光学红色序列的偏移量和紫外线过量。最后，我们将我们的目录与ACCEPT聚类样本（Cavagnolo等人，2009），并发现蓝色BCGs倾向于在低熵和短冷却时间的集群中。也就是说，蓝光可能是由于最近的恒星形成与冷却流提供的气体有关。（节略）
Determining the positions of halo centres in large-scale structure surveys is crucial for many cosmological studies. A common assumption is that halo centres correspond to the location of their brightest member galaxies. In this paper, we study the dynamics of brightest galaxies with respect to other halo members in the Sloan Digital Sky Survey DR7. Specifically, we look at the line-of-sight velocity and spatial offsets between brightest galaxies and their neighbours. We compare those to detailed mock catalogues, constructed from high-resolution, dark-matter-only $N$-body simulations, in which…
The CASSOWARY spectroscopy survey: A new sample of gravitationally lensed galaxies in SDSS
明亮的引力透镜星系为我们提供了高红移星系的最详细的图像。然而，由于极少数的超亮z~2透镜系统已证实的红移，大多数详细的光谱研究已被限制在他们的范围。为了增加可用于详细跟踪的明亮透镜星系的数量，我们在斯隆数字巡天（SDSS）中开展了一项光谱活动，目标是宽分离（>3角秒）星系-星系透镜候选者。在我们CASSOWARY调查的早期努力的基础上，我们针对SDSS中的候选星系-星系透镜系统的大样本，使用完善的搜索算法识别位于明亮的红色星系周围的蓝色弧状结构。在本文中，我们提出了一个新的红移目录包含25个透镜源SDSS通过光谱的候选星系星系透镜系统的后续确认。在这个新的样本中包括两个已知的z~2最亮的星系（r=19.6和19.7），一个z=1.43的低金属丰度（12 + log（O/H）~8.0）的极端星云线发射星系，以及许多可能进行详细跟踪的系统。源红移跨度为0.9<z<2.5（中位红移为1.9），它们的光学星等范围为19.6<r <22.3. We present a brief source-by-source discussion of the spectroscopic properties extracted from our confirmatory spectra and discuss some initial science results. With mo…
The relative growth of Optical and Radio Quasars in SDSS
我们将SDSS DR 3类星体样品与FIRST和Vestergaard等人的黑洞（BH）质量样品进行交叉关联，比较了光学类星体和射电类星体的平均吸积历史。我们发现显著的统计证据表明，在z > 2时，射电类星体相对于光学类星体具有更高的平均爱丁顿比λ，而在z 2时，情况显然相反< 1. At z >，射电类星体的质量恰好小于光学类星体;然而，随着红移的减小，射电类星体出现在相对于光学类星体质量越来越大的黑洞中。这两个趋势意味着射电源并不仅仅是光学类星体的随机子样本。从我们的数据来看，射电活动与BH质量和/或吸积率之间没有明显的相关性，这表明BH的其他属性，可能是自旋，作为射电活动的驱动因素。我们已经检查了我们的主要结果不依赖于任何明显的偏见。我们进行了详细的模拟合理的吸积历史的光学和射电类星体，发现射电类星体增长的几个因素，最多，因为z ~ 4。活动射电类星体的预测质量函数和观测到的射电类星体的光学光度函数之间的比较，意味着一个显着较低的概率较低的质量黑洞是无线电大声在所有的时代，在协议中所观察到的本地宇宙。
We test the history of structure formation from redshift 1 to today by matching galaxies from VIPERS and SDSS with dark matter haloes in the MultiDark SMDPL N-body simulation. We first show that the standard subhalo abundance matching (SHAM) recipe implemented with MultiDark characterizes the clustering of galaxies well both at redshift 0 for SDSS and at redshift 1 for VIPERS. This is an important validation of the SHAM model at high redshift. We then remap the simulation timesteps to test alternative growth histories and infer the growth index $γ=0.6\pm0.3$. This analysis demonstrates the pow…
Using the Oxford Short Wavelength Integral Field specTrograph (SWIFT), we trace radial variations of initial mass function (IMF) sensitive absorption features of three galaxies in the Coma cluster. We obtain resolved spectroscopy of the central 5kpc for the two central brightest-cluster galaxies (BCGs) NGC4889, NGC4874, and the BCG in the south-west group NGC4839, as well as unresolved data for NGC4873 as a low-$σ_*$ control. We present radial measurements of the IMF-sensitive features sodium NaI$_{\rm{SDSS}}$, calcium triplet CaT and iron-hydride FeH0.99, along with the magnesium MgI0.88 and …
Using group catalogs from the SDSS DR7, we attempt to measure galactic conformity in the local universe. We measure the quenched fraction of neighbor galaxies around isolated primary galaxies, dividing the isolated sample into star-forming and quiescent objects. We restrict our measurements to scales $>1$ Mpc to probe the correlations between the formation histories of distinct halos. Over the stellar mass range $10^{9.7} \le M_\ast/M_\odot \le 10^{10.9}$, we find minimal statistical evidence for conformity. We further compare these data to predictions of the halo age-matching model, in which …
Photometric Redshifts and Systematic Variations in the SEDs of Luminous Red Galaxies from the SDSS DR7
利用贝叶斯模板拟合方法构造了一组光谱能量分布（SED）模板，用于估算亮红星系（LRGs）的光度红移。通过检查几个公开可用的SED集的颜色属性在0<z<0.5的红移范围内，并将它们与SDSS DR 7数据进行比较，我们发现，只有一些研究的SED近似匹配的颜色的LRG数据在整个红移范围内，但不是在定量水平所需的精确光度红移。我们产生新的SED叠加模型SED的复合恒星星族与爆发模型，允许两个组件被红的灰尘，以匹配的数据在五个不同的红移箱。我们选择了一组代表LRG数据在颜色空间中的五个红移箱，从而定义了我们的新的SED模板集光度红移估计。我们用新的模板集和我们的贝叶斯模板拟合光度红移代码（PhotoZ）得到的结果几乎是无偏的，σ（Δz）=0.027（包括离群值），和一小部分灾难性离群值（|z光-z光谱|/（1+z_spec）>0.15）。我们发现，最佳描述最亮星系（-24.5<M_R<-22.7）的模板确实在z=0.1到z=0.5之间变化，与恒星星族的老化一致。此外，我们发现，最佳描述z<0.1的星系的模板作为星系绝对星等的函数存在很大差异，这表明亮度较低的星系的恒星形成活动增加。我们的研究结果的基础上测光的SDSS LRG和我们的SED模板拟合的平均SDSS LRG光谱在不同的光度和红移箱的比较支持。
We analyze spatially resolved and co-added SDSS-IV MaNGA spectra with signal-to-noise ~100 from 2200 passive central galaxies (z~0.05) to understand how central galaxy assembly depends on stellar mass (M*) and halo mass (Mh). We control for systematic errors in Mh by employing a new group catalog from Tinker (2020a,b) and the widely-used Yang et al. (2007) catalog. At fixed M*, the strength of several stellar absorption features varies systematically with Mh. Completely model-free, this is one of the first indications that the stellar populations of centrals with identical M* are affected by t…
We adapt the L-Galaxies semi-analytic model to follow the star-formation histories (SFH) of galaxies -- by which we mean a record of the formation time and metallicities of the stars that are present in each galaxy at a given time. We use these to construct stellar spectra in post-processing, which offers large efficiency savings and allows user-defined spectral bands and dust models to be applied to data stored in the Millennium data repository. We contrast model SFHs from the Millennium Simulation with observed ones from the VESPA algorithm as applied to the SDSS-7 catalogue. The overall agr…
Upcoming galaxy surveys and 21-cm experiments targeting high redshifts $z\gtrsim 6$ are highly complementary probes of galaxy formation and reionization. However, in order to expedite the large volume simulations relevant for 21-cm observations, many models of galaxies within reionization codes are entirely subgrid and/or rely on halo abundances only. In this work, we explore the extent to which resolving and modeling individual galaxy formation histories affects predictions both for the galaxy populations detectable by upcoming surveys and the signatures of reionization accessible to upcoming…
The clustering of dark matter halos depends on the assembly history of halos at fixed halo mass; a phenomenon referred to as \textit{halo assembly bias}. Halo assembly bias is readily observed in cosmological simulations of dark matter. However, it is difficult to detect it in observations. The identification of galaxy or cluster properties correlated with the formation time of the halo at fixed halo mass and the ability to select galaxy clusters free from projection effects are the two most significant hurdles in the observational detection of halo assembly bias. The latter, in particular, ca…
The Sloan Digital Sky Survey pipeline photometry underestimates the brightnesses of the most luminous galaxies. This is mainly because (i) the SDSS overestimates the sky background and (ii) single or two-component Sersic-based models better fit the surface brightness profile of galaxies, especially at high luminosities, than does the de Vaucouleurs model used by the SDSS pipeline. We use the PyMorph photometric reductions to isolate effect (ii) and show that it is the same in the full sample as in small group environments, and for satellites in the most massive clusters as well. None of these …
Using the DIANOGA hydrodynamical zoom-in simulation set of galaxy clusters, we analyze the dynamics traced by stars belonging to the Brightest Cluster Galaxies (BCGs) and their surrounding diffuse component, forming the intracluster light (ICL), and compare it to the dynamics traced by dark matter and galaxies identified in the simulations. We compute scaling relations between the BCG and cluster velocity dispersions and their corresponding masses (i.e. $M_\mathrm{BCG}^{\star}$- $σ_\mathrm{BCG}^{\star}$, $M_{200}$- $σ_{200}$, $M_\mathrm{BCG}^{\star}$- $M_{200}$, $σ_\mathrm{BCG}^{\star}$- $σ_{2…
The Star Formation and Nuclear Accretion Histories of Normal Galaxies in the AGES Survey
我们结合了来自重叠的9.3平方度NOAO深宽视场巡天（NDWFS），AGN和星系演化巡天（AGES）以及XBootes巡天的IR，光学和X射线数据，以测量6146个正常星系的X射线演化，作为绝对光学光度，红移和光谱类型的函数，在很大程度上未探索的红移范围0.1 < z < 0.5。因为只有最近或最亮的星系在X射线中被单独检测到，我们使用叠加分析来确定样本的平均属性。我们的研究结果表明，光谱晚型星系的X射线辐射主要是由恒星形成，而从早型星系的主要是由热气体和活动星系核发射的组合。我们发现，平均恒星形成和超大质量黑洞吸积速率密度的演化类似于（1+z）^[3]，这与在明亮的、可单独探测的星暴星系和活动星系核样本中发现的趋势一致。我们的工作也证实了许多以前的叠加分析微弱的源人口的结果，改进的统计。
We report the first constraints on the growth rate of the universe, $f(z)σ_8(z)$, with intrinsic alignments (IAs) of galaxies. We measure the galaxy density-intrinsic ellipticity cross-correlation and intrinsic ellipticity autocorrelation functions over $0.16 < z < 0.7$ from luminous red galaxies (LRGs) and LOWZ and CMASS galaxy samples in the Sloan Digital Sky Survey (SDSS) and SDSS-III BOSS survey. We detect clear anisotropic signals of IA due to redshift-space distortions. By combining measured IA statistics with the conventional galaxy clustering statistics, we obtain tighter constraints o…
We present constraints on the timescale of star formation variability and the correlation between star formation and host halo accretion histories of star-forming (SF) central galaxies from the scatter of the stellar-to-halo mass relation (SHMR). SF galaxies are found to have a tight relationship between their star formation rates and stellar masses on the so-called "star-forming sequence" (SFS), which characterizes their SF histories and $M_*$ growths. Meanwhile, observed SHMR constraints connect $M_*$ growth to halo accretion history. Combining these observed trends with a cosmological $N$-b…
Using the data set of The Three Hundred project, i.e. a suite of 324 hydrodynamical resimulations of cluster-sized haloes, we study galaxy cluster mergers and their effect on colour and luminosity changes of their brightest cluster galaxies (BCG). We track the main progenitor of each halo at z=0 and search for merger situations based on its mass accretion history, defining mergers as very rapid increases in the halo mass. Based upon the evolution of the dynamical state of the cluster we define a pre- and post-merger phase. We create a list of all these events and statistically study their mass…
Unveiling the (in)consistencies among the galaxy stellar mass function, star formation histories, satellite abundances and intracluster light from a semi-empirical perspective
We identify a sample of 1959 massive clusters of galaxies in the redshift range of 0.7<z<1.0 from the survey data of Sloan Digital Sky Survey (SDSS) and Wide-field Infrared Survey Explorer (WISE). These clusters are recognized as the overdensity regions around the SDSS luminous red galaxies, having a richness greater than 15 or an equivalent mass M_{500} \ge 2.5*10^{14}M_{\odot}. Among them, 1505 clusters are identified for the first time, which significantly enlarge the number of high-redshift clusters of z>0.75. By comparing them with clusters at lower redshifts, we confirm that richer clust…
The stellar mass assembly of brightest cluster galaxies (BCGs) is still debated. We have observed in CO with the IRAM-30m two star forming BCGs belonging to SpARCS clusters, 3C 244.1 ($z=0.4$) and SDSS J161112.65+550823.5 ($z=0.9$), and compared their molecular gas and star formation properties with those of a compilation of $\sim100$ distant cluster galaxies, including nine additional distant BCGs at ${z\sim0.4-3.5}$. We have set robust upper limits of $M_{{\rm H}_2}<1.0\times10^{10}~M_\odot$ and $<2.8\times10^{10}~M_\odot$ to their molecular gas content, respectively, as well as to the molec…
We test whether halo age and galaxy age are correlated at fixed halo and galaxy mass. The formation histories, and thus ages, of dark matter halos correlate with their large-scale density $ρ$, an effect known as assembly bias. We test whether this correlation extends to galaxies by measuring the dependence of galaxy stellar age on $ρ$. To clarify the comparison between theory and observation, and to remove the strong environmental effects on satellites, we use galaxy group catalogs to identify central galaxies and measure their quenched fraction, $f_Q$, as a function of large-scale environment…
