Our aim is to understand the role of the environment in the quenching of star formation of galaxies located in the infall cluster region of Abell 85 (A85). This is achieved by studying the post-starburst galaxy population as tracer of recent quenching. By measuring the equivalent width (EW) of the [OII] and Hdelta spectral lines, we classify the galaxies in three groups: passive (PAS), emission line (EL), and post-starburst (PSB) galaxies. The PSB galaxy population represents about 4.5% of the full sample. Dwarf galaxies (Mr > -18.0) account for about 70 - 80% of PSBs, which indicates that most of the galaxies undergoing recent quenching are low-mass objects. Independently of the environment, PSB galaxies are disk-like objects with g - r colour between the blue ELs and the red PAS ones. The PSB and EL galaxies in low-density environments show similar luminosities and local galaxy densities. The dynamics and local galaxy density of the PSB population in high density environments are shared with PAS galaxies. However, PSB galaxies inside A85 are at shorter clustercentric radius than PAS and EL ones. The value of the EW(Hdelta) is larger for those PSBs closer to the cluster centre. We propose two different physical mechanisms producing PSB galaxies depending on the environment. In low density environments, gas-rich minor mergers or accretions could produce the PSB galaxies. For high density environments like A85, PSBs would be produced by the removal of the gas reservoirs of EL galaxies by ram-pressure stripping when they pass near to the cluster centre.
Environmental effects are crucial to the understanding of the evolution of galaxies in dense environments, such as galaxy clusters. Using the large field-of-view of SITELLE, the unique imaging fourier transform spectrograph at CFHT, we are able to obtain 2D spectral information for a large and complete sample of cluster galaxies out to the infall region. We describe a pipeline developed to identify emission line galaxies (ELGs) from the datacube using cross-correlation techniques. We present results based on the spatial offsets between the emission-line regions and stellar continua in ELGs fro…
We study complete sample of spiral galaxies brighter than M$_{\mathrm{B}} \sim$-18.4 in three Abell clusters: A85 ($z=\,$0.055), A496 ($z=\,$0.033) and A2670 ($z=\,$0.076). This work is based on a large volume limited, blind Hi-survey (21cm, NRAO-VLA), on optical imaging (CFHT) and on the search for dynamical substructures. Our goal is to explore the effects of local environment on the HI gas properties and this, in turn, on the star formation activity and quenching of individual galaxies. We report significant differences among the HI properties of these clusters and we discuss the role playe…
A group of merging galaxies falling onto Abell 2142
Observatoire de Paris（巴黎天文台）；Sorbonne Université（索邦大学）；Université PSL（巴黎文理研究大学）；CNRS（法国国家科学研究中心）；Astronomisches Rechen-Institut, Zentrum für Astronomie der Universität Heidelberg（海德堡大学天体物理计算研究所）；Sternberg Astronomical Institute, Moscow M.V. Lomonosov State University（莫斯科国立罗蒙诺索夫大学斯佩尔斯基天体物理研究所）；Collège de France（法兰西学院）
We quantify the relative importance of environmental quenching versus pre-processing in $z\sim1$ clusters by analysing the infalling galaxy population in the outskirts of 15 galaxy clusters at $0.8<z<1.4$ drawn from the GOGREEN and GCLASS surveys. We find significant differences between the infalling galaxies and a control sample; in particular, an excess of massive quiescent galaxies in the infalling region. These massive infalling galaxies likely reside in larger dark matter haloes than similar-mass control galaxies because they have twice as many satellite galaxies. Furthermore, these satel…
In this work, we combine the semi-analytic model of galaxy formation and evolution SAG with the $102$ relaxed simulated galaxy clusters from The Three Hundred project, and we study the link between the quenching of star formation (SF) and the physical processes that galaxies experience through their dynamical history in and around clusters. We classify galaxies in four populations based on their orbital history: recent and ancient infallers, and backsplash and neighbouring galaxies. We find that $\sim 85$ per cent of the current population of quenched galaxies located inside the clusters are a…
We study the star formation histories (SFHs) and mass-weighted ages of 331 UVJ-selected quiescent galaxies in 11 galaxy clusters and in the field at 1<z<1.5 from the Gemini Observations of Galaxies in Rich Early ENvironments (GOGREEN) survey. We determine the SFHs of individual galaxies by simultaneously fitting rest-frame optical spectroscopy and broadband photometry to stellar population models. We confirm that the SFHs are consistent with more massive galaxies having on average earlier formation times. Comparing galaxies found in massive clusters with those in the field, we find galaxies wi…
Recent progress in constraining the massive accretions (>1:10) experienced by the Milky Way (MW) and the Andromeda galaxy (M31) offers an opportunity to understand the dwarf galaxy population of the Local Group. Using zoom-in dark matter-only simulations of MW-mass haloes and concentrating on subhaloes that are thought to be capable of hosting dwarf galaxies, we demonstrate that the infall of a massive progenitor is accompanied with the accretion and destruction of a large number of subhaloes. Massive accreted progenitors do not increase the total number of infalling subhaloes onto a MW-mass h…
Observations of the low-mass satellites in the Local Group have shown high fractions of gas-poor, quiescent galaxies relative to isolated dwarfs, implying that the host halo environment plays an important role in the quenching of dwarf galaxies. In this work, we present measurements of the quenched fractions and quenching timescales of dwarf satellite galaxies in the DC Justice League suite of 4 high-resolution cosmological zoom-in simulations of Milky Way-mass halos. We show that these simulations accurately reproduce the satellite luminosity functions of observed nearby galaxies, as well as …
Anisotropic infall in the outskirts of OmegaWINGS galaxy clusters
我们在$0.04 < z < 0.08$研究了星系团外围环境对星系淬灭的影响。我们使用了一个子样本的14个WINGS和OmegaWINGS星系团，这些星系团通过丝状体与其他星系团/星系团相连，并根据它们是否位于丝状体方向，分别研究了位于这些星系团外围两个区域的星系。我们还使用星系团和星系场中的星系样本作为比较。连接星系群/星系团的丝状结构是在六度场星系红移巡天数据第三版中发现的。我们发现一小部分的被动星系之间的集群和字段的中间的集群的郊区。我们发现的证据更有效的淬火的方向的细丝。我们还分析了丰富的后星爆星系的郊区的集群集中我们的研究在两个极端的星系集，根据他们的相空间位置：backsplash和真正的infallers。我们发现，高达$\sim70\%$的星爆后星系在灯丝的方向可能是后溅，而这个数字下降到$\sim40\%$在各向同性的下落区域。这一小部分星系的存在是第一次落入星系团中，最近已经熄灭，支持了一种情况，即大量的丝状星系很久以前就已经熄灭了。
Hector Galaxy Survey: Falling in Between - Infalling Galaxies in the Midst of the Abell 3667 Merger
Macquarie University（麦考瑞大学）；Korea Astronomy and Space Science Institute (KASI)（韩国天文学与空间科学研究所）；Sydney Institute for Astronomy (SIfA), School of Physics, The University of Sydney（悉尼大学物理学院天文研究所）；University of Queensland（昆士兰大学）；University of New South Wales（新南威尔士大学）；Australian National University（澳大利亚国立大学）；Yonsei University（延世大学）；Swinburne University of Technology（斯威本科技大学）
We model satellite quenching at $z \sim 1$ by combining $14$ massive ($10^{13.8} < M_{\mathrm{halo}}/\mathrm{M}_{\odot} < 10^{15}$) clusters at $0.8 < z < 1.3$ from the GOGREEN and GCLASS surveys with accretion histories of $56$ redshift-matched analogs from the IllustrisTNG simulation. Our fiducial model, which is parameterized by the satellite quenching timescale ($τ_{\rm quench}$), accounts for quenching in our simulated satellite population both at the time of infall by using the observed coeval field quenched fraction and after infall by tuning $τ_{\rm quench}$ to reproduce the observed s…
We analyse the connection between the star formation quenching of galaxies and their location in theoutskirts of clusters in the redshift range $z=[0,2]$ by estimating the fraction of red galaxies. More specifically, we focus on galaxies that infall isotropically from those that are infalling alongside filaments. We use a sample of galaxies obtained from the semi-analytic model of galaxy formation SAG applied to the MultiDark simulation. {\textsc{mdpl2}}. In agreement with observational results, we find that the infall regions show levels of star formation that are intermediate between those o…
Satellite quenching and morphological transformation of galaxies in groups and clusters
Department of Physics and Astronomy, McMaster University（麦克马斯特大学物理与天文学系）；NAT-Universidade Cidade de São Paulo（圣保罗城市大学）；School of Physics and Astronomy, University of Nottingham（诺丁汉大学物理与天文学院）
SRG/eROSITA PV observations revealed the A3391/95 cluster system and the Northern Clump (MCXC J0621.7-5242 galaxy cluster) are aligning along a cosmic filament in soft X-rays, similarly to what has been seen in simulations before. We aim to understand the dynamical state of the Northern Clump as it enters the atmosphere ($3\times R_{200}$) of A3391. We analyzed joint eROSITA, XMM-Newton, and Chandra observations to probe the morphological, thermal, and chemical properties of the Northern Clump from its center out to a radius of 988 kpc ($R_{200}$). We utilized the ASKAP/EMU radio data, DECam o…
Ultra-diffuse and Ultra-compact Galaxies in the Frontier Fields Cluster Abell 2744
我们报道了哈勃前沿场计划在大质量星系团Abell 2744（z=0.308）中发现的大量超弥散星系团（UDG）。由于这个星系团的质量是Coma的5倍，我们的观测使我们能够将0.7 dex扩展到van der Burg等人2016年报告的UDG丰度和星系团质量之间关系的高质量端。使用与van der Burg et al. 2016相同的选择标准，A2744估计有2133 +/- 613个UDG，是Coma的10倍。正如Lee & Jang 2016所指出的，A2744包含许多未解析的致密天体，这些作者主要将其确定为球状星团。然而，这些天体的光度与超紧凑矮星系（UCD）更一致。UCD和UDG的丰度与集群质量成幂律关系，具有相似的指数，尽管UDG和UCD在集群内的径向分布非常不同。UCD的径向面密度分布向星团中心急剧上升，而UDG的面密度分布基本平坦。总之，这些观察结果暗示了一种情况，即A2744中的一些UCD可能曾经与下落的UDG有关。当UDG落入并溶解时，它们留下了未结合的超紧凑矮星的残余物。
Quenching and ram pressure stripping of simulated Milky Way satellite galaxies
我们提出了一套30个宇宙学变焦模拟银河系类宿主星系的本星系群的卫星星系的恒星形成的淬火的预测。御夫座的模拟解决卫星到银河系的经典矮球状星系的光度。我们发现强烈的质量依赖和距离依赖的淬火信号，超过600千秒差距的矮系统只有强烈淬火低于恒星质量的$10^7$ M $_\odot$。冲压压力剥离似乎是占主导地位的淬火机制和50%的淬火系统停止恒星形成内1 Gyr的第一次下降。我们表明，在宿主星系的$R_{200}$半径的系统是由两个人口：（一）第一个落入人口已进入主机晕在过去的几个Gyrs和（ii）人口返回“backsplash”系统，有一个更广泛的互动与主机。后溅星系如果没有通过红移为零的方式返回到宿主星系，则表现出类似于$R_{200}$内部星系的猝灭特性，并且与其他外部系统不同。模拟淬火与恒星质量的趋势有一定的张力与观测，但我们的模拟能够再现淬火时间的范围内，从解决本群矮星系的恒星星族测量。
We study the dynamics of Abell 370 (A370), a highly massive Hubble Frontier Fields galaxy cluster, using self-consistent three-dimensional N-body/hydrodynamical simulations. Our simulations are constrained by X-ray, optical spectroscopic and gravitational lensing, and Sunyaev-Zel'dovich (SZ) effect observations. Analyzing archival Chandra observations of A370 and comparing the X-ray morphology to the latest gravitational lensing mass reconstruction, we find offsets of ~30 kpc and ~100 kpc between the two X-ray surface brightness peaks and their nearest mass surface density peaks, suggesting th…
A key unknown of the Milky Way (MW) satellites is their orbital history, and, in particular, the time they were accreted onto the MW system since it marks the point where they experience a multitude of environmental processes. We present a new methodology for determining infall times, namely using a neural network (NN) algorithm. The NN is trained on MW-analogues in the EAGLE hydrodynamical simulation to predict if a dwarf galaxy is at first infall or a backsplash galaxy and to infer its infall time. The resulting NN predicts with 85\% accuracy if a galaxy currently outside the virial radius i…
The Megaparsec-scale Gas-sloshing Spiral in the Remnant Cool Core Cluster Abell 1763
本文对红移z = 0.231的大质量星系团Abell 1763进行了多波长研究。对19.6 ks钱德拉存档观测的图像分析显示，在团内介质（ICM）中，团簇范围内的螺旋状表面亮度增强。虽然这样的螺旋被理解为形成具有晃动强冷芯（SCC）的簇，但包括螺旋顶点的气体具有中等熵（$\sim$ 110 keV cm $^{2}$）和冷却时间（$\sim$ 6.8 Gyr），表明在整个螺旋形成过程中发生芯破裂。两个由系统中第二和第三等级的星系主导的子星系团沿着一条平行于主星系团ICM的伸长轴的线。这两个子系统似乎都是沿着先前发现的星系团间的灯丝下降的，并且都被认为是负责启动破坏性核心晃动的扰动者的候选者。动力学分析表明，正在发生的相对径向速度为$\sim$ 1800 km s $^{-1}$。Abell 1763星系团中最明亮的星系团具有高的视向速度（v $_{pec}$ $\sim$ 650 km s $^{-1}$），并拥有一个强大的（P $_{1.4}$ $\sim$ 10 $^{26}$ W Hz $^{-1}$）弯曲双叶射电源，可能是由合并中诱导的相对大体积ICM流形成的。SCC破坏的集群合并模型调用低碰撞参量作为核心转换所需的条件。与此相反，在阿贝尔1763年发生的高角动量事件表明，离轴合并在建立非冷核心集群人口比以前假设的发挥更大的作用。
Circumgalactic medium depletion drives satellite quenching in IllustrisTNG
European Southern Observatory（欧洲南方天文台）；Kavli Institute for Cosmology, University of Cambridge（剑桥大学卡弗里宇宙学研究所）；Cavendish Laboratory, University of Cambridge（剑桥大学卡文迪许实验室）；Astronomisches Rechen Institut, Zentrum für Astronomie der Universität Heidelberg（海德堡大学天体物理计算研究所）；Fakultät für Physik, Ludwig-Maximilians-Universität München（慕尼黑大学物理学院）；College of Natural and Mathematical Sciences, University of Dodoma（多多马大学自然与数理科学学院）；School of Physics and Astronomy, University of Birmingham（伯明翰大学物理与天文学院）
The star formation and gas content of satellite galaxies around the Milky Way (MW) and Andromeda (M31) are depleted relative to more isolated galaxies in the Local Group (LG) at fixed stellar mass. We explore the environmental regulation of gas content and quenching of star formation in $z=0$ galaxies at $M*=10^{5-10}\rm{M}_{\odot}$ around 14 MW-mass hosts from the FIRE-2 simulations. Lower-mass satellites ($M*\lesssim10^7\rm{M}_{\odot}$) are mostly quiescent and higher-mass satellites ($M*\gtrsim10^8\rm{M}_{\odot}$) are mostly star-forming, with intermediate-mass satellites ($M*\approx10^{7-8…
We examine Suzaku, XMM-Newton, and Chandra observations of the Abell 2029/2033 system to investigate the nature of a bridge of X-ray emission joining the two galaxy clusters. By modelling the contributions from the outskirts of the two clusters, and excluding the emission from the southern infalling group and the background group LOS9, we find a significant excess of X-ray emission between the two clusters at the level of 6.5-7.0$σ$, depending on the choice of model, that cannot be explained by the overlap of the clusters. This excess component to the surface brightness is consistent with bein…
We use the Auriga simulations to probe different satellite quenching mechanisms operating at different mass scales ($10^5 M_\odot \lesssim M_\star \lesssim 10^{11} M_\odot$) in Milky Way-like hosts. Our goal is to understand the origin of the satellite colour distribution and star-forming properties in both observations and simulations. We find that the satellite populations in the Auriga simulations, which was originally designed to model Milky Way-like host galaxies, resemble the populations in the Exploration of Local VolumE Satellites (ELVES) Survey and the Satellites Around Galactic Analo…
A Radio Relic and a Search for the Central Black Hole in the Abell 2261 Brightest Cluster Galaxy
我们目前的VLA图像和HST/STIS光谱的Abell 2261中最亮的星团星系（BCG）的中心内的源。获得这些观测结果是为了检验其超大扁平核心反映了其超大质量黑洞的喷射的假设。研究人员对嵌入核心的四个最明亮的“结”中的三个进行了光谱分析，以测试其中一个是否代表了与一个位移的大质量黑洞相连的恒星。这三个节点与BCG的径向速度偏移dV < ~150 km/s。纽结2和3的运动学、颜色和恒星质量与坠落的低质量星系或更大的剥离星系团成员一致。然而，纽结1的恒星速度色散存在很大的误差，这意味着我们不能排除它拥有一个大质量黑洞的假设。A2261-BCG有一个紧凑的，遗留的无线电源，从光学核心的中心偏移了6.5 kpc（投影），但没有活动的无线电核心，可以将银河系中心的黑洞精确定位到4800万年前的10 GHz通量极限<3.6 uJy. Its spectrum and morphology are suggestive of an active galactic nucleus that switched off >，平均分配条件下的磁场为15 uG。这些观测结果仍然与核黑洞已经从其核心喷射出来的假设相一致，但是定位超大质量黑洞或证明A2261-BCG缺乏一个黑洞的关键任务仍然有待完成。
Many disc galaxies in clusters have been found with bulges of similar age or younger than their surrounding discs, at odds with field galaxies of similar morphology and their expected inside-out formation. We use the EAGLE simulations to test potential origins for this difference in field and cluster galaxies. We find, in agreement with observations, that on average disc-dominated field galaxies in the simulations have older inner regions, while similar galaxies in groups and clusters have similarly aged or younger inner regions. This environmental difference is a result of outside-in quenchin…
A rare opportunity to distinguish internal and environmental effects on galaxy evolution is afforded by "Supergroups", systems which are rich and massive but include several comparably rich substructures, surrounded by filaments. We present here a multiwavelength photometric and spectroscopic study of the galaxy population in the Supergroup Abell 1882 at $z$=0.139, combining new data from the MMT and Hectospec with archival results from the Galaxy And Mass Assembly (GAMA) survey, the Sloan Digital Sky Survey (SDSS), NED, the Gemini Multi-Object Spectrograph (GMOS) and Galaxy Evolution Explorer…
We study the impact of local environment on the transformation of spiral galaxies in three nearby ($z < 0.08$) Abell clusters: A85/A496/A2670. These systems were observed in HI with the Very Large Array, covering a volume extending beyond the virial radius and detecting 10, 58, 38 galaxies, respectively. High fractions (0.40--0.86) of bright spirals [log$(M_{*}/M_{\odot})=9-10$] are not detected in HI. We provide further evidence of environmental effects consisting in significant fractions (0.10--0.33) of abnormal objects and a number of red (passive) spirals, suggesting an ongoing process of …
