We present the results of a new spectroscopic survey for dusty intervening absorption systems, particularly damped Ly$α$ absorbers (DLAs), towards reddened quasars. The candidate quasars are selected from mid-infrared photometry from the Wide-field Infrared Survey Explorer combined with optical and near-infrared photometry. Out of 1073 candidates, we secure low-resolution spectra for 108 using the Nordic Optical Telescope on La Palma, Spain. Based on the spectra, we are able to classify 100 of the 108 targets as quasars. A large fraction (50 %) is observed to have broad absorption lines (BALs). Moreover, we find 6 quasars with strange breaks in their spectra, which are not consistent with regular dust reddening. Using template fitting we infer the amount of reddening along each line of sight ranging from A(V)$\approx$0.1 mag to 1.2 mag (assuming an SMC extinction curve). In four cases, the reddening is consistent with dust exhibiting the 2175Å feature caused by an intervening absorber, and for two of these, a MgII absorption system is observed at the best-fit absorption redshift. In the rest of the cases, the reddening is most likely intrinsic to the quasar. We observe no evidence for dusty DLAs in this survey. However, the large fraction of BAL quasars hampers the detection of absorption systems. Out of the 50 non-BAL quasars only 28 have sufficiently high redshift to detect Ly$α$ in absorption.
To study environmental effects on the circumgalactic medium (CGM), we use the samples of redMaPPer galaxy clusters, background quasars and cluster galaxies from the SDSS. With ~82 000 quasar spectra, we detect 197 MgII absorbers in and around the clusters. The detection rate per quasar is 2.7$\pm$0.7 times higher inside the clusters than outside the clusters, indicating that MgII absorbers are relatively abundant in clusters. However, when considering the galaxy number density, the absorber-to-galaxy ratio is rather low inside the clusters. If we assume that MgII absorbers are mainly contribut…
A complete census of dusty star-forming galaxies (DSFGs) at early epochs is necessary to constrain the obscured contribution to the cosmic star formation rate density (CSFRD), however DSFGs beyond $z \sim 4$ are both rare and hard to identify from photometric data alone due to degeneracies in submillimeter photometry with redshift. Here, we present a pilot study obtaining follow-up Atacama Large Millimeter Array (ALMA) $2\,$mm observations of a complete sample of 39 $850\,\rmμm$-bright dusty galaxies in the SSA22 field. Empirical modeling suggests $2\,$mm imaging of existing samples of DSFGs s…
On the equivalent width of the Fe K$α$ line produced by a dusty absorber in active galactic nuclei
被遮蔽的活动星系核提供了一个研究围绕中心引擎的物质的机会。吸收体上的几何和物理约束可以从再处理的活动星系核辐射中推导出来。特别地，遮蔽气体可以再处理核X射线发射，产生窄的Fe K $α$线和康普顿反射峰。近年来，X射线从模糊环面反射的模型已经被计算出来;然而，尽管反射气体可能是尘埃，模型还没有考虑到尘埃对预测光谱的影响。我们研究这个问题，通过分析两组模型，有和没有灰尘的存在下，使用一维光电离代码多云。对一系列柱密度（$22 <{\rm log}[N_H(\rm cm^{-2})]< 24.5$）和氢密度（$6 <{\rm log}[n_H(\rm cm^{-3})]< 8$）进行计算。计算结果表明，尘埃的存在下，可以提高的Fe K $α$等效宽度（EW）在反射光谱的因素高达$\approx$ 8康普顿厚（CT）的气体和一个典型的ISM粒度分布。EW相对于反射连续谱的增强是由于由尘埃颗粒的各向异性散射行为引起的反射连续谱强度的降低。这种效应将是最相关的反射，从遥远的，主要是中性气体，是一个可能的解释活动星系核，显示出强大的Fe K $α$ EW和一个相对较弱的反射连续。我们的研究结果表明，它是一个重要的是要考虑到灰尘，而建模的X射线反射光谱，推断CT柱密度从观测到的Fe K $α$ EW可能并不总是有效的。需要多维度模型来充分探索影响的程度。
We present here a detailed analysis of an unusual absorption line system in the quasar SDSS J122826.79+100532.2. The absorption lines in the system have a common redshifted velocity structure starting from $v\sim0$ and extending to $\sim1,000\ \mathrm{km~s}^{-1}$, and are clearly detected in hydrogen Balmer series up to H$ι$, in metastable neutral helium triplet, and in optical lines of excited states of single ionized iron. We estimated that the absorber has a density $n_{\mathrm{H}}\approx10^{8.4}\ \mathrm{cm}^{-3}$ and an ionization parameter $U\approx10^{-1.2}$, thereupon located it at $r_…
How do active galactic nuclei with low optical luminosities produce powerful radio emission? Recent studies of active galactic nuclei with moderate radio and low optical luminosities (Fanaroff & Riley class I, FR I) searching for broad nuclear emission lines in polarized light, as predicted by some active galactic nucleus unification models, have found heterogeneous results. These models typically consist of a central engine surrounded by a torus of discrete dusty clouds. These clouds would absorb and scatter optical emission, blocking broad nuclear emission lines, and reradiate in mid-infrare…
As the possible progenitors of passive galaxies at z=2-3, dusty star-forming galaxies (DSFGs) at z>4 provide a unique perspective to study the formation, assembly, and early quenching of massive galaxies in the early Universe. The extreme obscuration in optical-IR makes (sub)mm spectral scans the most universal and unbiased way to confirm/exclude the high-z nature of candidate dusty star-forming galaxies. We present here the status of the NIKA2 Cosmological Legacy Survey (N2CLS), which is the deepest wide-area single-dish survey in the millimeter searching for high-z DSFGs. We also introduce a…
The Spitzer Space Telescope Survey of the Orion A & B Molecular Clouds - Part I: A Census of Dusty Young Stellar Objects and a Study of their Mid-IR Variability
We report a NOrthern Extended Millimeter Array (NOEMA) and Atacama Large Millimeter/submillimeter Array (ALMA) search for redshifted CO emission from the galaxies associated with seven high-metallicity ([M/H] $\geq -1.03$) damped Lyman-$α$ absorbers (DLAs) at $z\approx1.64-2.51$. Our observations yielded one new detection of CO(3-2) emission from a galaxy at $z=2.4604$ using NOEMA, associated with the $z=2.4628$ DLA towards QSO B0201+365. Including previous searches, our search results in detection rates of CO emission of $\approx56^{+38}_{-24}$ % and $\approx11^{+26}_{-9}$ %, respectively, in…
The Diversity of Metal-Enrichment and Abundance Patterns at High Redshift: A Magellan Survey of Gas-rich Galaxies Traced by Damped Lyman-alpha Absorbers at z~5
本研究通过 Magellan 巡天分析10个 z≈4.2–5.0 的 DLA 元素丰度，揭示高红移金属丰度的显著离散、C/α元素增丰及 Pop III 贡献，并证实早期富金属多尘埃系统的存在。
Wide, deep, blind continuum surveys at submillimetre/millimetre (submm/mm) wavelengths are required to provide a full inventory of the dusty, distant Universe. However, conducting such surveys to the necessary depth, with sub-arcsec angular resolution, is prohibitively time-consuming, even for the most advanced submm/mm telescopes. Here, we report the most recent results from the ALMACAL project, which exploits the 'free' calibration data from the Atacama Large Millimetre/submillimetre Array (ALMA) to map the lines of sight towards and beyond the ALMA calibrators. ALMACAL has now covered 1,001…
A deep MeerKAT view of associated HI absorption in radio AGNs at intermediate redshift: Role of absorber geometry and conditions of the gas
ASTRON, the Netherlands Institute for Radio Astronomy（荷兰射电天文研究所）；Kapteyn Astronomical Institute, University of Groningen（格罗宁根大学卡普坦天文研究所）；Department of Physics and Astronomy, University of Sheffield（谢菲尔德大学物理与天文学系）；Joint ALMA Observatory（ALMA联合研究所）；Joint Institute for VLBI ERIC（甚长基线干涉测量欧洲研究基础设施联合研究所）
Some luminous and ultraluminous infrared galaxies (LIRGs and ULIRGs) host extremely compact and dusty nuclei. The intense infrared radiation arising from warm dust in these sources is prone to excite vibrational levels of molecules such as HCN. This results in emission from the rotational transitions of vibrationally excited HCN (HCN-vib), with the brightest emission found in compact obscured nuclei (CONs). We aim to establish how common CONs are in the local Universe, and whether their prevalence depends on the luminosity or other properties of the host galaxy. We have conducted an Atacama La…
Information on the structure around active galactic nuclei (AGN) has long been derived from measuring lags in their varying light output at different wavelengths. In principle, infrared data would reach to larger radii, potentially even probing reprocessed radiation in any surrounding dusty torus. In practice, this has proved challenging because high quality data are required to detect such variability, and the observations must stretch over a long period to probe the likely month-scale lags in variability. In addition, large numbers of sources would need to be observed to start searching for …
Gravitationally Lensed Quasar SDSS J1442+4055: Redshifts of Lensing Galaxies, Time Delay, Microlensing Variability, and Intervening Metal System at z ~ 2
We study the origin of the anomalous deep absorption in a spectrum of the SDSS J110511.15+530806.5 distant quasar (z=1.929) obtained by the Sloan Digital Sky Survey in Data Release 7 of the optical catalog. We aim to estimate the velocity of absorbing material, and we show that this material considerably affects our measurements of the black hole (BH) mass in massive quasars with the use of common virial mass estimators. The spectral shape of the quasar was modeled assuming that the accretion disk emission is influenced by a hot corona, warm skin, and absorbing material located close to the nu…
An ASKAP survey for HI absorption towards dust-obscured quasars
类星体被吸积的气体和尘埃遮蔽，或者被尘埃干扰的星系遮蔽，会导致活动星系核（AGN）在光学选择的巡天中被遗漏。无线电观测可以克服这种尘埃偏见。特别是，无线电调查寻找HI吸收通知我们如何AGN可以影响到冷的中性气体介质内的主星系，或通过观察到的视线气体运动学的干预星系的人口。本文介绍了利用澳大利亚SKA探路者（ASKAP）试运行阵列在$0.4 < z < 1$对34个遮蔽类星体进行HI吸收线测量的结果。我们检测到三个HI吸收线，其中一个系统以前未知。通过对两个源的光学跟踪，我们发现在所有的探测中HI气体都与活动星系核有关，因此这些活动星系核被其宿主星系内的物质所遮蔽。我们的大多数样本都是紧凑的，此外，要么是千兆赫兹峰值频谱（GPS），或陡峭的频谱（CSS）源，都被认为是年轻的或最近重新触发的无线电活动星系核。我们的样本的无线电频谱能量分布分类同意星系演化模型中，模糊AGN最近才变得活跃。我们相关联的HI检测率的GPS和紧凑的SS源相匹配的其他调查对这些来源。我们还发现了浅的和不对称的HI吸收特征，这与以前的研究结果一致，即致密射电星系中的冷中性介质通常受到活动星系核的运动学扰动。
