Nuclear Activity is more prevalent in Star-Forming Galaxies
D. J. Rosario, P. Santini, D. Lutz, H. Netzer, F. E. Bauer, S. Berta, B. Magnelli, P. Popesso, D. Alexander, W. N. Brandt, R. Genzel, R. Maiolino, J. R. Mullane… 展开作者
D. J. Rosario, P. Santini, D. Lutz, H. Netzer, F. E. Bauer, S. Berta, B. Magnelli, P. Popesso, D. Alexander, W. N. Brandt, R. Genzel, R. Maiolino, J. R. Mullaney, R. Nordon, A. Saintonge, L. Tacconi, S. Wuyts
We explore the question of whether low and moderate luminosity Active Galactic Nuclei (AGNs) are preferentially found in galaxies that are undergoing a transition from active star formation to quiescence. This notion has been suggested by studies of the UV-to-optical colors of AGN hosts, which find them to be common among galaxies in the so-called "Green Valley", a region of galaxy color space believed to be composed mostly of galaxies undergoing star-formation quenching. Combining the deepest current X-ray and Herschel. PACS far-infrared (FIR) observations of the two Chandra Deep Fields (CDFs) with redshifts, stellar masses and rest-frame photometry derived from the extensive and uniform multi-wavelength data in these fields, we compare the rest-frame U-V color distributions and SFR distributions of AGNs and carefully constructed samples of inactive control galaxies. The UV-to-optical colors of AGNs are consistent with equally massive inactive galaxies at redshifts out to z~2, but we show that such colors are poor tracers of star formation. While the FIR distributions of both star-forming AGNs and star-forming inactive galaxies are statistically similar, we show that AGNs are preferentially found in star-forming host galaxies, or, in other words, AGNs are less likely to be found in weakly star-forming or quenched galaxies. We postulate that, among X-ray selected AGNs of low and moderate accretion luminosities, the supply of cold gas primarily determines the accretion rate distribution of the nuclear black holes.
Evidence for Widespread AGN Activity among Massive Quiescent Galaxies at z ~ 2
利用4 Ms Chandra Deep Field-South（CDF-S）巡天的X射线数据，对123个质量完备（M * > 5e 10 Msun）的恒星形成星系和静止星系（1.5 < z < 2.5）样本中活动星系核（AGN）的存在进行了定量研究。41+/-7%的星系被X射线直接探测到，22+/-5%的星系在静止坐标系0.5-8 keV的光度下与活动星系核一致（L_0.5- 8 keV> 3e 42 ergs/s）。后一部分是类似的恒星形成和静止的星系，并不依赖于星系的恒星质量，这表明可能发光AGN是由外部效应，如合并触发。我们检测到显着的平均X射线信号在堆叠的图像为单独未检测到的恒星形成和静止的星系，与恒星形成的光谱一致，只有和/或低光度AGN在这两种情况下。比较恒星形成率推断从2-10千电子伏的光度那些从静止帧红外+紫外线发射，我们发现的X射线过剩的低光度活动星系核的指示证据。在静止的星系中，这一过量表明，其中多达70-100%的星系含有低光度或高光度的活动星系核，而在恒星形成星系中相应的比例较低（43-65%）。活动星系核在大质量静止z ~ 2星系中的普遍存在为活动星系核在星系演化过程中阻碍恒星形成的重要性提供了观测支持。
In the redshift interval of $2<z<3$, the physical conditions of the inter-stellar medium (ISM) in star-forming galaxies are likely to be different from those in the local Universe because of lower gaseous metallicities, higher gas fractions, and higher star formation activities. In fact, observations suggest that higher electron densities, higher ionization parameters, and harder UV radiation fields are common. In this paper, based on the spectra of H$α$-selected star-forming galaxies at $z=2.5$ taken with Multi-Object Spectrometer for InfraRed Exploration (MOSFIRE) on Keck-1 telescope, we mea…
Motivated by the apparently conflicting results reported in the literature on the effect of environment on nuclear activity, we have carried out a new analysis by comparing the fraction of galaxies hosting active galactic nuclei (AGNs) in the most overdense regions (rich galaxy clusters) and the most underdense ones (voids) in the local universe. Exploiting the classical BPT diagnostics, we have extracted volume limited samples of star forming and AGN galaxies. We find that, at variance with star-forming galaxies, AGN galaxies have similar distributions of specific star formation rates and of …
Cluster mergers may play a fundamental role in the formation and evolution of cluster galaxies. Stroe et al. (2014) revealed unexpected over-densities of candidate H$α$ emitters near the ~1 Mpc-wide shock fronts of the massive (~2x10$^{15}$M$_{\odot}$) "Sausage" merging cluster, CIZA J2242.8+5301. We used Keck/DEIMOS and WHT/AF2 to confirm 83 H$α$ emitters in and around the merging cluster. We find that cluster star-forming galaxies in the hottest X-ray gas and/or in the cluster sub-cores (away from the shock fronts) show high [SII]6716/[SII]6761 and high [SII]6716/H$α$, implying very low elec…
New insight into the relation between star formation activity and dust content in galaxies
我们从SDSS DR 6中收集了3258个低红移星系的样本，并补充了GALEX，2 MASS和IRAS在远紫外和红外波段的光度观测。我们使用一个最近的，简单的，但物理动机的模型来解释所观察到的光谱能量分布的星系在这个样本中的物理参数描述的恒星形成历史和尘埃含量的统计约束。对1658个具有最高S/N观测值的星系的子样本的关注使我们能够最清楚地研究星系的各种物理性质之间的强相关性。我们发现，典型的尘埃质量的恒星形成与恒星形成率（SFR）的显着相关。我们还发现尘埃与恒星的质量比、尘埃质量与恒星形成率的比值以及弥漫的星际介质贡献的尘埃光度分数都与特定的SFR密切相关。与最近的化学和尘埃演化的星系模型的比较表明，这些相关性可能会出现，至少部分，从一个进化序列。当星系形成恒星时，它们的ISM变得富含尘埃，而气体供应的下降使比SFR降低。有趣的是，一个年轻的、活跃的恒星形成星系，其尘埃与气体的比例很低，可能仍然是高度尘埃，因为它含有大量的星际气体。这可能是重要的解释年轻的，富含气体的恒星形成星系在高红移的红外辐射。我们的研究提供了一个有用的本地参考未来的统计研究的恒星形成和尘埃的星系在高红移的性质。
Co-evolution of AGN and Star-forming Galaxies in the Australia Telescope Large Area Survey
ATLAS（Australia Telescope Large Area Survey）是一项广泛的深射电观测，其特点是采用综合多波长方法。ATLAS正在创建一个大型的射电选择星系数据集，用于研究恒星形成和活动星系的演化和相互关系。虽然这个项目还远未完成，但我们已经开始回答其中的一些问题，并在此过程中偶然发现了三个惊喜：* FRI/FRII无线电响亮的活动星系核嵌入螺旋星系，* 无线电明亮的活动星系核在红外线下意外地微弱，可能是在高红移 * 红外发光射电宁静活动星系核上，这是射电-红外比这些和其他观测表明，活动星系核的活动和恒星的形成在高红移时变得越来越相互依赖。
Recent observations of AGN activity in massive galaxies (log Mstar / Msun > 10.4) show that: 1) at z < 1, AGN-hosting galaxies do not show enhanced merger signatures compared to normal galaxies, 2) also at z < 1, most AGNs are hosted by quiescent galaxies; and 3) at z > 1, percentage of AGNs in star forming galaxies increases and becomes comparable to AGN percentage in quiescent galaxies at z ~ 2. How can major mergers explain AGN activity in massive quiescent galaxies which have no merger features and no star formation to indicate recent galaxy merger? By matching merger events in a cosmologi…
We measure the location and evolutionary vectors of 69 Herschel-detected broad-line active galactic nuclei (BLAGNs) in the M_BH-M_* plane. BLAGNs are selected from the COSMOS and CDF-S fields, and span the redshift range 0.2< z<2.1. Black-hole masses are calculated using archival spectroscopy and single-epoch virial mass estimators, and galaxy total stellar masses are calculated by fitting the spectral energy distribution (subtracting the BLAGN component). The mass-growth rates of both the black hole and galaxy are calculated using Chandra/XMM-Newton X-ray and Herschel far-infrared data, relia…
We present the detection of four far-infrared fine-structure oxygen lines, as well as strong upper limits for the CO(2-1) and [N II] 205 um lines, in 3C 368, a well-studied radio-loud galaxy at z = 1.131. These new oxygen lines, taken in conjunction with previously observed neon and carbon fine-structure lines, suggest a powerful active galactic nucleus (AGN), accompanied by vigorous and extended star formation. A starburst dominated by O8 stars, with an age of ~6.5 Myr, provides a good fit to the fine-structure line data. This estimated age of the starburst makes it nearly concurrent with the…
The growth of galaxy clusters is energetic and may trigger and/or quench star formation and black hole activity. The ENISALA project is a collection of multiwavelength observations aimed at understanding how large-scale structure drives galaxy and black hole evolution. Here, we introduce optical spectroscopy of over 800 H$α$ emission-line galaxies, selected in 14 z~0.15-0.31 galaxy clusters, spanning a range of masses and dynamical states. We investigate the nature of the emission lines in relation to the host galaxy properties, its location within the cluster, and the properties of the parent…
The mechanisms that bring galaxies to strongly reduce their star formation activity (star-formation quenching) is still poorly understood. To better study galaxy evolution, we propose a classification based on the maps of the ionised hydrogen distribution, traced by kpc-resolved, equivalent width of H$α$ maps, and the nuclear activity of the galaxies using information from the BPT diagnostic diagrams. Using these tools, we group a sample of 238 galaxies from the CALIFA survey in six quenching stages (QS): objects dominated by recent star formation; systems that present a quiescent-nuclear-ring…
The neutral atomic hydrogen (HI) mass function (HIMF) describes the distribution of the HI content of galaxies at any epoch; its evolution provides an important probe of models of galaxy formation and evolution. Here, we report Giant Metrewave Radio Telescope HI 21cm spectroscopy of blue star-forming galaxies at $z\approx0.20-0.42$ in the Extended Groth Strip, which has allowed us to determine the scaling relation between the average HI mass ($\rm{M_{HI}}$) and the absolute B-band magnitude ($\rm{M_B}$) of such galaxies at $z \approx 0.35$, by stacking the HI 21cm emission signals of galaxy su…
Galaxy pairs in the Sloan Digital Sky Survey - IX: Merger-induced AGN activity as traced by the Wide-field Infrared Survey Explorer
星系之间的相互作用预计会导致气体流入，可能引发核活动。由于流入的物质可以掩盖相互作用星系的中心区域，以前的光学研究的一个潜在的限制是，被掩盖的活动星系核（AGN）可以错过在合并序列的各个阶段。我们提出了第一个大的中红外研究活动星系核合并和星系对，以量化的相互作用所引发的模糊活动星系核的发病率。样本由斯隆数字巡天（Sloan Digital Sky Survey）绘制的星系对和合并后的星系组成，这些星系对和宽视场红外天空探测器（WISE）的探测结果相匹配。我们发现，在对活动星系核的分数，相对于质量，红移和环境匹配的控制样本，增加作为一个功能，减少预计分离。这种增强是最引人注目的合并后的样本，在那里我们发现一个因素的10-20过剩的活动星系核部分相比，控制。虽然这种趋势是在定性协议的基础上的光学活动星系核选择的结果，中红外选择活动星系核过剩增加更显着地在合并后比光学活动星系核。我们的研究结果表明，积极占主导地位的光学遮蔽活动星系核变得更加普遍，在最先进的合并，与理论预测一致。
We present ALMA observations of the 870$μ$m continuum and CO(4-3) line emission in the core of the galaxy cluster ClJ1449+0856 at z=2, a NIR-selected, X-ray detected system in the mass range of typical progenitors of today's massive clusters. The 870$μ$m map reveals six F$_{870μm}$ > 0.5 mJy sources spread over an area of 0.07 arcmin$^2$, giving an overdensity of a factor ~10 (6) with respect to blank field counts down to F$_{870μm}$ > 1 (0.5) mJy. On the other hand, deep CO(4-3) follow-up confirms membership of three of these sources, but suggests that the remaining three, including the brigh…
