The H.E.S.S. (High Energy Stereoscopic System) telescopes observed Coma for ~8hr in a search for gamma-ray emission at energies >1TeV. The large 3.5deg FWHM field of view of H.E.S.S. is ideal for viewing a range of targets at various sizes including the Coma cluster core, the radio-relic (1253+275) and merger/infall (NGC 4839) regions to the southwest, and features greater than deg away. No evidence for point-like nor extended TeV gamma-ray emission was found and upper limits to the TeV flux F(E) for E>1, >5, and >10TeV were set for the Coma core and other regions. Converting these limits to an energy flux E^2F(E) the lowest or most constraining is the E>5TeV upper limit for the Coma core (0.2deg radius) at ~8Crab flux units or ~10^{-13}ph cm^{-2} s^{-1}. The upper limits for the Coma core were compared with a prediction for the gamma-ray emission from proton--proton interactions, the level of which ultimately scales with the mass of the Coma cluster. A direct constraint using our most stringent limit for E>5 TeV, on the total energy content in non-thermal protons with injection energy spectrum proportional to E^{-2.1} and spatial distribution following the thermal gas in the cluster, is found to be ~0.2 times the thermal energy, or ~10^{62}erg. The E>5 TeV gamma-ray threshold in this case corresponds to cosmic-ray proton energies >50TeV. Our upper limits rule out the most optimistic theoretical models for gamma ray emission from clusters and complement radio observations which constrain the cosmic ray content in clusters at significantly lower proton energies, subject to assumptions on the magnetic field strength.
The Velocity Dispersion Function of Very Massive Galaxy Clusters: Abell 2029 and Coma
基于对星系团Abell 2029和后发座星系团的广泛红移观测,我们测量了整个星系团成员星系的光度函数和恒星质量函数。最重要的是,我们测量的速度色散函数(VDFs)的静态成员。MMT/Hectospec红移调查的星系在A2029确定982光谱成员,838名成员,我们得出的中心速度色散的光谱。后发座是唯一一个被调查得如此密集的星团。A2029和Coma的LF、SMF和VDF基本相同。簇的SMF与模拟一致。静止星系的A2029和后发星系的速度色散比场星系的速度色散有一个明显更陡的斜率$\lesssim 100$ km s $^{-1}$。在速度色散$\gtrsim 250$ km s $^{-1}$时,星系团VDFs也超过了磁场。星系团VDF和场VDF之间的差异是对模拟和宇宙结构形成的潜在重要测试。
Unbiased and precise mass calibration of galaxy clusters is crucial to fully exploit galaxy clusters as cosmological probes. Stacking of weak lensing signal allows us to measure observable-mass relations down to less massive halos halos without extrapolation. We propose a Bayesian inference method to constrain the intrinsic scatter of the mass proxy in stacked analyses. The scatter of the stacked data is rescaled with respect to the individual scatter based on the number of binned clusters. We apply this method to the galaxy clusters detected with the AMICO (Adaptive Matched Identifier of Clus…
Keck/LRIS Spectroscopic Confirmation of Coma Cluster Dwarf Galaxy Membership Assignments
Keck/LRIS多目标光谱仪对后发座星系团核心区的140个最低和最高表面亮度的暗(19 < R < 22)矮星系候选者进行了测量。这些光谱被用来测量红移,并建立这些微弱的矮种群的成员资格。低表面亮度样本的主要目标是测试我们使用形态和表面亮度标准区分后发座星系团成员和背景星系的能力,使用高分辨率HST/ACS图像。候选人被评为预期成员,不确定,或预期的背景。从93个光谱中识别出51个矮星系成员和20个背景星系。我们的形态成员估计成功率为100%的对象,预计将成为成员和优于90%的星系预计将在背景中。我们确认,低表面亮度是一个很好的指标集群成员。高表面亮度星系几乎总是背景与混乱所产生的情况下,只有罕见的紧凑的椭圆星系。在中等表面亮度下出现更多问题的情况。这些星系中的许多都被赋予了不确定的成员评级,并且这些星系被发现是成员的时间约为一半。包括颜色信息将改进成员资格确定,但是对于在仅使用表面亮度和形态标准时已经被错误识别的一些相同对象将失败。具有B-V色的紧凑椭圆星系,特别是红色序列红向0.2等,需要光谱跟踪。在47个高表面亮度的样本中,有19个物体的红移使它们位于后发座星系团中。红移测量和使用间接手段建立集群成员进行了讨论。
Learning the Universe: Constrained simulations of the Coma galaxy cluster -- I. Radial X-ray and Compton-y signatures
Max Planck Institut für Astrophysik(马克斯·普朗克天体物理研究所);Department of Physics, University of Oxford(牛津大学物理系);Department of Astronomy, Columbia University(哥伦比亚大学天文学系)
We present a detailed census of galaxies in and around PC217.96+32.3, a spectroscopically confirmed Coma analog at z=3.78. Diverse galaxy types identified in the field include Lya emitters (LAEs), massive star-forming galaxies, and ultra-massive galaxies (log (Mstar/Msun)>= 11) which may have already halted their star formation. The sky distribution of the star-forming galaxies suggests the presence of a significant overdensity (delta_g=8+/-2), which is spatially offset from the previously confirmed members by 3-4 Mpc to the west. Candidate quiescent and post-starburst galaxies are also found …
High significance detection at 4.8 GHz of the radio halo in the Coma galaxy cluster with the Sardinia Radio Telescope
INAF-Osservatorio Astronomico di Cagliari(意大利国家天体物理研究所卡利亚里天文台);Dipartimento di Fisica e Astronomia, Università di Bologna(博洛尼亚大学物理与天文学系);INAF, Istituto di Radio Astronomia(意大利国家天体物理研究所射电天文研究所)
Very deep spectroscopy of the Coma cluster line of sight: exploring new territories
环境效应对星系团有重要的影响,但在非常微弱的星等(R>21)的研究几乎完全基于成像。我们在这里提出了一个非常深的光谱调查星系的视线后发座,根据红移获得的VLT/VIMOS的715个星系在前所未有的星等范围21<R<23(绝对星等-14至-12)。我们确认了Adami等人(2005年a)在昏迷中发现的亚结构,并发现了三个新的亚结构。我们在Coma后面检测到许多组:z~0.5的大型结构,SDSS长城,以及z~0.054的大型且非常年轻的结构。这些结构解释了Gavazzi等人(2009)最近弱透镜分析得出的质量图。矮星系的轨道可能是各向异性的和径向的,并且可能起源于径向落入星系团的场星系。后发座矮星系的光谱特征表明,红色或吸收线星系具有较大的恒星质量,比蓝色或发射线星系更古老。R <22 galaxies show less prominent absorption lines than R>22星系。对于场星系来说,这种趋势就不那么明显了,这表明部分暗淡的后发星系可能是在NGC 4911星系团坠落后从场星系中注入的。我们列出了五个超紧凑矮星系候选者。我们还在全球范围内证实了我们以前的星系光度函数的光谱结果,并发现矮星系遵循类似于明亮星系绘制的红色序列。后发座中有大量的矮星系,它们是沿着暗条落入星系团的部分场星系。
We demonstrate a novel technique for calibrating the energy scale of the XMM EPIC-pn detector, which allows us to measure bulk flows in the intracluster medium (ICM) of the Perseus and Coma clusters. The procedure uses the instrumental lines present in all observations, in particular, Cu-Ka. By studying their spatial and temporal variations, in addition to incorporating calibration observations, we refined the absolute energy scale to better than 150 km/s at the Fe-K line, a large improvement over the nominal accuracy of 550 km/s. We then mapped the bulk motions over much of the central 1200 a…
The evolution of dwarf galaxies in the Coma supercluster
利用SDSS DR 7在500平方度区域的分光光度数据,研究后发座超星系团(z=0.023)中矮星系(~M*+2<M_z<M*+4)的演化。我们发现,在后发座超星系团中,红矮星主要集中在后发座和阿贝尔1367星系团的致密核心,以及嵌入连接它们的灯丝中的星系群中。然而,在后发座星系团和Abell 1367星系团的陷落区发现了后星爆(k+A)矮星,偶尔也在沿暗条嵌入的星系群中发现,这表明深势阱附近普遍存在的强速度场可能与导致矮星系后星爆阶段的机制密切相关。此外,后发座星系团中一些k+A矮星的蓝色,在其维里半径内发现,这表明这些星系中的恒星形成在过去的500 Myr中非常迅速地熄灭了。超星系团中60%以上的红矮星系的H_δ吸收角为0-3角,这表明在这些星系中有一个不可忽略的部分发生了一个主要的恒星形成事件,在最后一个Gyr内结束,使它们能够移动到红色序列。后发座超星系团中的蓝矮星系在EW(H_α)-EW(H_δ)平面上呈双峰分布,其中一个星系团在H_α中有很高的发射,在H_δ中也有一些发射。在EW(H_α)-EW(H_δ)平面上,蓝矮星和红矮星的一个子群重合,在H_δ上表现出吸收,在H_α上表现出相对较低的发射。我们认为,后者人口的很大一部分是被动矮星系的祖先,大量发现在低红移丰富的集群,如后发座的核心。
The Cosmic Web is a complex network of filaments, walls and voids that represent the largest structures in the Universe. In this network, which is the direct result of structure formation, galaxy clusters occupy central positions as the nodes, connected through the filaments. In this work, we investigate the position in the Cosmic Web of one of the most known and best studied clusters of galaxies, the Coma cluster. We make use of the Sloan Digital Sky Survey Data Release 7 (SDSS DR7) Main Galaxy Sample and of the Discrete Persistent Structure Extractor (DisPerSE) to detect large scale filament…
We take a close look at the galaxies in the Coma Supercluster and assess the role of the environment (in the form of cluster, group and supercluster filament) in their evolution, in particular examining the role of groups. We characterise the groups according to intrinsic properties such as richness and halo mass, as well as their position in the supercluster and proximity to the two rich clusters, Abell 1656 (Coma) and Abell 1367. We devise a new way of characterising the local environment using a kernel density estimator. We find that apart from the dominant effects of the galaxy mass, the e…
本研究使用斯隆数字巡天(SDSS DR 8)第八次数据发布的r波段图像,研究最近的富星系团环境之一后发座星系团中透镜状(S 0)星系中的条形。我们开发的技术,酒吧检测,并评估其成功时,适用于SDSS图像数据。为了检测和消除酒吧,我们执行2D鼓包+磁盘+酒吧光分解的星系图像与GALFIT。使用人工星系图像的样本,我们确定最微弱的幅度,在该酒吧可以成功地测量在SDSS的深度和分辨率。我们进行详细的分解83个S 0星系后发座,64个来自中央样本,19个来自集群郊区样本。对于中心样本,S 0 bar分数为72^{+5}_{-6}%。该值明显高于用椭圆拟合法检测条形图的48^{+6}_{-6}%。在一个固定的光度,禁止S 0的(G-R)颜色比unbarred S 0的0.02马格。酒吧的频率和强度增加对微弱的光度。无论是中央金属丰度,也没有恒星年龄分布有显着差异之间的酒吧和unbarred S 0。有一个增加的酒吧分数向集群核心,但这是在一个低的显着性水平。酒吧最多有一个弱的相关性与集群中心半径。
In 1933, Fritz Zwicky's famous investigations of the mass of the Coma cluster led him to infer the existence of dark matter \cite{1933AcHPh...6..110Z}. His fundamental discoveries have proven to be foundational to modern cosmology; as we now know such dark matter makes up 85\% of the matter and 25\% of the mass-energy content in the universe. Galaxy clusters like Coma are massive, complex systems of dark matter in addition to hot ionized gas and thousands of galaxies, and serve as excellent probes of the dark matter distribution. However, empirical studies show that the total mass of such syst…
We present the current state of models for the $z\sim3$ carbon monoxide (CO) line-intensity signal targeted by the CO Mapping Array Project (COMAP) Pathfinder in the context of its early science results. Our fiducial model, relating dark matter halo properties to CO luminosities, informs parameter priors with empirical models of the galaxy-halo connection and previous CO(1-0) observations. The Pathfinder early science data spanning wavenumbers $k=0.051$-$0.62\,$Mpc$^{-1}$ represent the first direct 3D constraint on the clustering component of the CO(1-0) power spectrum. Our 95% upper limit on …
Constraints on the Intracluster Dust Emission in the Coma Cluster of Galaxies
我们利用斯皮策多波段成像光度计对后发座星系团内尘埃的红外辐射进行了研究。我们的观测产生了有史以来最深的星系团的中红外和远红外图像。在这三个波段中的每一个波段中,我们都没有探测到中心多余分量的特征,这与红外空间天文台(ISO)先前的探测报告相反。我们仍然发现70和160微米之间的亮度比显示出中心过量的边缘符号,与ISO结果定性一致。我们的分析表明,过量的比例更可能是由于微弱的红外源躺在起伏的卷云前景。我们的观测结果表明,在24、70和160微米处,在距离星系团中心100 kpc的范围内,过量辐射的2 σ上限分别为5 x 10^-3 MJy/sr、6 x 10^-2 MJy/sr和7 x 10^-2 MJy/sr。这些值与其他星系团中发现的值一致,表明与星际介质相比,星团中心附近的尘埃不足3个数量级以上。