We report on continued, $\sim$15 year-long, broad Balmer emission lines in three metal-poor dwarf emission-line galaxies selected from Sloan Digital Sky Survey spectroscopy. The persistent luminosity of the broad Balmer emission indicates the galaxies are active galactic nuclei (AGNs) with virial black hole masses of $\sim 10^{6.7}{-10^{7.0}\ M_{\odot}}$. The lack of observed hard X-ray emission and the possibility that the Balmer emission could be due to a long-lived stellar transient motivated additional follow-up spectroscopy. We also identify a previously-unreported blueshifted narrow absorption line in the broad H$α$ feature in one of the AGNs, indicating an AGN-driven outflow with hydrogen column densities of order $10^{17}$ cm$^{-2}$. We also extract light curves from the Catalina Real-Time Transient Survey and the Zwicky Transient Facility. We detect probable AGN-like variability in three galaxies, further supporting the AGN scenario. This also suggests the AGNs are not strongly obscured. This sample of galaxies are among the most metal-poor which host an AGN ($Z=0.05 - 0.16\ Z_\odot$). We speculate they may be analogues to seed black holes which formed in unevolved galaxies at high redshift. Given the rarity of metal-poor AGNs and small sample size available, we investigate prospects for their identification in future spectroscopic and photometric surveys.
Balmer absorption is a rare phenomenon in active galactic nuclei (AGNs). So far, only seven Balmer-absorption AGNs have been reported in literature. We here report the identification of SDSS\,J112611.63+425246 as a new Balmer-absorption AGN through our spectral analysis, and study the kinematics of its narrow emission-line region (NLR). We model the continuum by a linear combination of a starlight component, a powerlaw from the central AGN and the emission from the FeII complex. After the subtraction of the modeled continuum, each emission/absorption line is profiled by a sum of multi Gaussian…
We selected an active galactic nuclei (AGN) sample ($0 < z \le 0.35$) from Sloan Digital Sky Survey Data Release 7, and measured the broad- (${\rm Hα^{b}/Hβ^{b}}$) and narrow-line Balmer decrements (${\rm Hα^{n}/Hβ^{n}}$) of 554 selected AGNs. We found that the distributions of Balmer decrements can be fitted by a Gaussian function and give the best estimates of ${\rm Hα^{b}/Hβ^{b}} = 3.16$ with a standard deviation 0.07 dex, and ${\rm Hα^{n}/Hβ^{n}} = 4.37$ with a standard deviation 0.10 dex. We inspected the distributions of ${\rm Hα^{b}/Hβ^{b}}$ and ${\rm Hα^{n}/Hβ^{n}}$ in the Baldwin$-$Ph…
Here we investigate the H$β$ and Mg II spectral line parameters used for the black hole mass (M$_{\rm BH}$) estimation for a sample of Type 1 Active Galactic Nuclei (AGN) spectra selected from the Sloan Digital Sky Survey (SDSS) database. We have analyzed and compared the virialization of the H$β$ and Mg II emission lines, and found that the H$β$ line is more confident virial estimator than Mg II. We have investigated the influence of the Balmer continuum emission to the M$_{\rm BH}$ estimation from the UV parameters, and found that the Balmer continuum emission can contribute to the overestim…
We detected a very strong X-ray decline in the galaxy IRAS23226-3843 within the XMM-Newton slew survey in 2017. Subsequently, we carried out multi-band follow-up studies to investigate this fading galaxy in more detail. We took deep follow-up Swift, XMM-Newton, and NuSTAR observations in combination with optical SALT spectra of IRAS23226-3843 in 2017. In addition, we reinspected optical, UV, and X-ray data that were taken in the past. IRAS23226-3843 decreased in X-rays by a factor of more than 30 with respect to ROSAT and Swift data taken 10 to 27 years before. The broadband XMM-Newton/NuSTAR …
The Broad Line Region of Active Galactic Nuclei is characterized by broad Balmer emission lines in their optical spectra. The broad Balmer emission lines are found to be asymmetric, some blue sided and others red sided in their asymmetry. One of the components behind the asymmetry is thought to be an accretion disk wind. We probe the accretion disk wind using the broad balmer emission line profiles. This asymmetry of the broad balma emission line profiles is measured in velocity space after a measurement of the line shift at percentiles from 0, in increaments of 10, up to 90. In addition, the …
Cosmic Dawn Center (DAWN)（宇宙黎明中心）；Niels Bohr Institute, University of Copenhagen（哥本哈根大学尼尔斯·玻尔研究所）；Institute of Astronomy, University of Cambridge（剑桥大学天文研究所）；University of Oxford（牛津大学）
In this manuscript, an interesting blue Active Galactic Nuclei (AGN) SDSS J154751.94+025550 (=SDSS J1547) is reported with very different line profiles of broad Balmer emission lines: double-peaked broad H$β$ but single-peaked broad H$α$. SDSS J1547 is the first AGN with detailed discussions on very different line profiles of the broad Balmer emission lines, besides the simply mentioned different broad lines in the candidate for a binary black hole (BBH) system in SDSS J0159+0105. The very different line profiles of the broad Balmer emission lines can be well explained by different physical co…
The Extreme Rarity and Physical Properties of Low-redshift AGNs with Balmer Absorption
The Kavli Institute for Astronomy and Astrophysics, Peking University（北京大学科维理天文与天体物理研究所）；Department of Astronomy, School of Physics, Peking University（北京大学物理学院天文学系）；Max Planck Institute for extraterrestrial Physics（马克斯·普朗克地外物理研究所）
In this letter, we report positive correlations between broad line width and broad line flux for the broad balmer lines of the long-term observed AGN PG 1613+658. Rather than the expected negative correlations under the widely accepted virialization assumption for AGN BLRs, the positive correlations indicate much different BLR structures of PG 1613+658 from the commonly considered BLR structures which are dominated by the equilibrium between radiation pressure and gas pressure. Therefore, accretion disk origin is preferred for the observed broad single-peaked optical balmer lines of PG 1613+65…
In the manuscript, the simple but interesting results are reported on the upper limits of NLRs sizes of a small sample of 38 low redshift ($z<0.1$) AGN with double-peaked broad emission lines (double-peaked BLAGN), in order to check whether the NLRs sizes in type-1 AGN and type-2 AGN obey the similar empirical dependence on \o3~ luminosity. In order to correct the inclination effects on projected NLRs sizes of type-1 AGN, the accretion disk origin is commonly applied to describe the double-peaked broad H$α$ leading to the determined inclination angles of central disk-like BLRs of the 38 double…
We investigate the intrinsic Baldwin effect (Beff) of the broad H$α$ and H$β$ emission lines for six Type 1 active galactic nuclei (AGNs) with different broad line characteristics: two Seyfert 1 (NGC 4151 and NGC 5548), two AGNs with double-peaked broad line profiles (3C 390.3 and Arp 102B), one narrow line Seyfert 1 (Ark 564), and one high-luminosity quasar with highly red asymmetric broad line profiles (E1821+643). We found that a significant intrinsic Beff was present in all Type 1 AGNs in our sample. Moreover, we do not see strong difference in intrinsic Beff slopes in different types of A…
Most massive galaxies contain a supermassive black hole (SMBH) at their center. When galaxies merge, their SMBHs sink to the center of the new galaxy where they are thought to eventually merge. During this process an SMBH binary is formed. The presence of two sets of broad emission lines in the optical spectrum of an active galactic nucleus (AGN) has been interpreted as evidence for two broad line regions (BLR), one surrounding each SMBH in a binary. We modeled the broad Balmer emission lines in SDSS spectra of 373 extreme variability AGNs using one broad and several narrow Gaussian components…
ATLAS. II. Extremely High Incidence of Balmer Line Absorption with Predominant Blueshifts in LRDs: Statistical Insights through Comparison with Type 1 AGNs
Institute for Cosmic Ray Research, The University of Tokyo（东京大学宇宙射线研究所）；Department of Physics, Graduate School of Science, The University of Tokyo（东京大学理学研究科物理系）；National Astronomical Observatory of Japan（日本国立天文台）；Astronomical Science Program, Graduate Institute for Advanced Studies, SOKENDAI（SOKENDAI高级研究院天文学科学项目）；Kavli Institute for the Physics and Mathematics of the Universe (WPI), The University of Tokyo（东京大学 Kavli宇宙物理数学研究所（WPI））
In this manuscript, we proposed an interesting method to test the dual supermassive black hole model for AGN with double-peaked narrow \oiii lines (double-peaked narrow emitters), through their broad optical Balmer line properties. Under the dual supermassive black hole model for double-peaked narrow emitters, we could expect statistically smaller virial black hole masses estimated by observed broad Balmer line properties than true black hole masses (total masses of central two black holes). Then, we compare the virial black hole masses between a sample of 37 double-peaked narrow emitters with…
An (in)complete NIRSpec census of Balmer absorption in Type 1 AGN -- radiation-driven outflows in little red dots, quasars and variable stars
University of Cambridge（剑桥大学）；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）；University College London（伦敦大学学院）
We present a spectroscopic study with the derivation of the physical properties of 37 Balmer break galaxies, which have the necessary lines to locate them in star-forming-AGN diagnostic diagrams. These galaxies span a redshift range from 0.045 to 0.93 and are somewhat less massive than similar samples of previous works. The studied sample has multiwavelength photometric data coverage from the ultraviolet to MIR Spitzer bands. We investigate the connection between star formation and AGN activity via optical, mass-excitation (MEx) and MIR diagnostic diagrams. Through optical diagrams, 31 (84%) s…
We present results from spectroscopic observations of AT 2018hyz, a transient discovered by the ASAS-SN survey at an absolute magnitude of $M_V\sim -20.2$ mag, in the nucleus of a quiescent galaxy with strong Balmer absorption lines. AT 2018hyz shows a blue spectral continuum and broad emission lines, consistent with previous TDE candidates. High cadence follow-up spectra show broad Balmer lines and He I in early spectra, with He II making an appearance after $\sim70-100$ days. The Balmer lines evolve from a smooth broad profile, through a boxy, asymmetric double-peaked phase consistent with a…
Origins of the UV continuum and Balmer emission lines in Little Red Dots: observational validation of dense gas envelope models enshrouding the AGN
Dunlap Institute for Astronomy and Astrophysics（邓普天文学与天体物理研究所）；Kavli Institute for Astronomy and Astrophysics, Peking University（北京大学柯夫利天文学与天体物理研究所）；David A. Dunlap Department of Astronomy and Astrophysics, University of Toronto（多伦多大学大卫·A·邓普普天文学与天体物理学系）；NRC Herzberg（国家研究委员会赫茨伯格研究所）
We report the discovery that the known `changing look' AGN Mrk 1018 has changed spectral type for a second time. New VLT-MUSE data taken in 2015 as part of the Close AGN Reference Survey (CARS) shows that the AGN has returned to its original Seyfert 1.9 classification. The CARS sample is selected to contain only bright type 1 AGN, but Mrk 1018's broad emission lines and continuum, typical of type 1 AGN, have almost entirely disappeared. We use spectral fitting of the MUSE spectrum and previously available spectra to determine the drop in broad line flux and the Balmer decrement. We find that t…
Space Telescope Science Institute（太空望远镜科学研究所）；Penn State University（宾夕法尼亚州立大学）；Vanderbilt University（范德堡大学）；Fisk University（菲斯克大学）；Tel Aviv University（特拉维夫大学）
Understanding the radiative and physical structures of inner region of a few 100 pc of AGNs is important to constrain the causes of their activities. Although the X-ray emission from the Comptonization region/corona and the accretion disc regulates the broad line emission regions and torus structures, the exact mutual dependency is not understood well. We performed correlation studies for X-ray, mid-infrared, and different components of Balmer emission lines for the selected sample of AGNs. Almost 10 different parameters and their inter-dependencies were explored in order to understand the und…
New reverberation mapping (RM) measurements, combined with accurate luminosities and line ratios, provide strong constraints on the location of the line emitting gas in the broad line region (BLR) of active galactic nuclei (AGN). In this paper I present new calculations of radiation pressure and magnetic pressure confined clouds and apply them to a ``generic AGN'' and to NGC 5548. The new calculations are in good agreement with the observed lags of all broad emission lines, and with the luminosities of La, Civ 1549, Ovi 1035 and Heii 1640. They are also in reasonable agreement with the luminos…
Here we discuss the physical conditions in the emission line regions (ELR) of active galactic nuclei (AGN), with the special emphasize on the unresolved problems, e.g. the stratification of the Broad Line Region (BLR) or the failure of the photoionization to explain the strong observed optical Fe II emission. We use here different line fluxes in order to probe the properties of the ELR, such as the hydrogen Balmer lines (Ha to He), the helium lines from two subsequent ionization levels (He II 4686 and He I 5876) and the strongest Fe II lines in the wavelength interval 4400-5400 Å. We found tha…
Mrk926 is known to be a highly variable AGN with very broad line profiles. We studied the continuum and line profile variations of this object with high temporal resolution in order to determine its broad-line region structure and to derive its BH mass. We carried out a high-cadence spectroscopic variability campaign of Mrk926 with the 10m HET telescope, aided by photometric V-band data taken at the Wise Observatory, over a period of about five months. We extracted spectroscopic continuum and line light curves, and computed CCFs as well as velocity-resolved CCFs with respect to the combined co…
We use the Balmer decrements of the broad-line regions (BLRs) and narrow-line regions (NLRs) of active galactic nuclei (AGNs) as reddening indicators to investigate the location of the dust for four samples of AGNs with reliable estimates of the NLR contribution to the Balmer lines. Intercomparison of the NLR and BLR Balmer decrements indicates that the reddening of the NLR sets a lower limit to the reddening of the BLR. Almost no objects have high NLR reddening but low BLR reddening. The reddening of the BLR is often substantially greater than the reddening of the NLR. The BLR reddening is co…
Little Red Dots on FIRE: Exploring the formation and observational signatures of ultra-compact early galaxies
University of Connecticut（康涅狄格大学）；University of Manchester（曼彻斯特大学）；University of Hull（赫尔大学）；J.P. Morgan Securities（摩根大通证券）；Northwestern University（西北大学）；NASA-Goddard Space Flight Center（美国宇航局戈达德太空飞行中心）；University of Zurich（苏黎世大学）
The importance of some atom hydrogen collisions in AGN has been investigated. The results are useful for better estimate of the hydrogen Balmer lines uxes, which usage for effective temperature diagnostics in astrophysical plasma is limited by errors from the line formation models. The data could be also useful for modeling cooler and denser parts of AGN BLR clouds, as well as for the investigation of Rydberg states of hydrogen and for the study of their in uence during the cosmological recombination epoch. The results of the present work suggest that the investigated processes are of interest…
Balmer Absorption Series and Broad Metal Lines in Two Luminous Little Red Dots
Princeton University（普林斯顿大学）；Cosmic Dawn Center (DAWN), Copenhagen, Denmark（哥本哈根宇宙黎明中心（DAWN））；Max-Planck-Institut für Astronomie（马克斯·普朗克天文学研究所）；Swinburne University of Technology（斯威本科技大学）；The Pennsylvania State University（宾夕法尼亚州立大学）
Active Galactic Nuclei (AGN) are extremely powerful cosmic objects, driven by accretion of hot gas upon super-massive black holes. The zoo of AGN classes are divided into two major groups, with Type-1 AGN displaying broad Balmer emission lines and Type-2 narrow ones. For a long time it was believed that a Type-2 AGN is a Type-1 AGN viewed through a dusty kiloparsec-size torus, but an emerging body of observations suggests more than just the viewing angle matters. Here we report significant differences in supernova counts and classes in the first study to date of supernovae near Type-1 and Type…
Sparks: The Magellan/FIRE survey from starburst to post-starburst
Kavli Institute for Particle Astrophysics & Cosmology, Stanford University（斯坦福大学卡弗里粒子天体物理与宇宙学研究所）；Center for Decoding the Universe, Stanford University（斯坦福大学解码宇宙中心）；Department of Astrophysical Sciences, Princeton University（普林斯顿大学天体物理科学系）；Department of Astronomy and Astrophysics, University of California Santa Cruz（加州大学圣克鲁兹分校天文与天体物理系）；Kavli Institute for the Physics and Mathematics of the Universe (Kavli IPMU)（宇宙物理与数学卡弗里研究所）；Division of Science, National Astronomical Observatory of Japan（日本国立天文台科学部）；Department of Physics and Astronomy, University of California, Riverside（加州大学河滨分校物理与天文系）；Max-Planck-Institut für extraterrestrische Physik（马克斯·普朗克地外物理研究所）
A supermassive black hole (SMBH) ejected from the potential well of its host galaxy via gravitational wave recoil carries important information about the mass ratio and spin alignment of the pre-merger SMBH binary. Such a recoiling SMBH may be detectable as an active galactic nucleus (AGN) broad line region offset by up to 10\,kpc from a disturbed host galaxy. We describe a novel methodology using forward modeling with \texttt{The Tractor} to search for such offset AGN in a sample of 5493 optically variable AGN detected with the Zwicky Transient Facility (ZTF). We present the discovery of 9 AG…
OQ~208: A New Fe~II Changing-look Active Galactic Nucleus and Implications for the Nature of the Changing-look Phenomenon
National Astronomical Observatories, Chinese Academy of Sciences（中国科学院国家天文台）；Department of Astronomy, University of California, Berkeley（加州大学伯克利分校天文学系）；School of Astronomy and Space Science, University of Chinese Academy of Sciences（中国科学院大学天文与空间科学学院）；Guangxi Key Laboratory for Relativistic Astrophysics, School of Physical Science and Technology, Guangxi University（广西大学物理科学与技术学院相对论天体物理重点实验室）
Sparks II: Panchromatic SED modeling and galaxy physical properties across the starburst to post-starburst sequence
Kavli Institute for Particle Astrophysics & Cosmology, Stanford University（斯坦福大学卡弗里粒子天体物理与宇宙学研究所）；Center for Decoding the Universe, Stanford University（斯坦福大学解码宇宙中心）；Department of Astrophysical Sciences, Princeton University（普林斯顿大学天体物理科学系）；Department of Astronomy and Astrophysics, University of California Santa Cruz（加州大学圣克鲁兹分校天文与天体物理系）；Kavli Institute for the Physics and Mathematics of the Universe (Kavli IPMU)（宇宙物理与数学卡弗里研究所）；Division of Science, National Astronomical Observatory of Japan（日本国立天文台科学部）；Max-Planck-Institut für extraterrestrische Physik（马克斯·普朗克地外物理学研究所）
We propose a new method for estimating the mass of a supermassive black hole, applicable to obscured AGNs. This method estimates the black hole mass using the width of the narrow core of the neutral FeKa emission line in X-rays and the distance of its emitting region from the black hole based on the isotropic luminosity indicator via the luminosity scaling relation. We collect the line width data of the neutral FeKa line core for seven type-1 AGNs and seven type-2 AGNs obtained by the Chandra HETGS. Assuming the virial relation between the locations and the velocity widths of the neutral FeKa …
Quasi-periodic X-ray eruptions (QPEs) are a recently discovered phenomenon, the nature of which remains unclear. Based on their discovery in active galactic nuclei (AGN), explanations related to an AGN accretion disk, or potentially stellar tidal disruption event (TDE), were put forward. Following the report of QPEs in apparently passive galaxies, alternatives including highly unequal mass compact object binaries have been proposed to explain their properties. We perform a systematic study of the five known QPE host galaxies with the aim of providing new insights into their nature. We analyse …
We calculated the polarization degree of hydrogen Balmer broad emission lines from a number of active galactic nuclei (AGNs) with determined virial factors. The objects were selected from the sample presented by Decarli et al.(2008). In our calculations, we used the model of the flattened disc-like structure of the broad-line emission region (BLR). In this model, the expression for the virial factor makes it possible to determine the inclination angle for the flattened BLR, which in turn yields the polarization degree of the broad emission lines. As a result, we obtained the direct relation be…
One of the proposed explanations for the broad, double-peaked Balmer emission lines observed in the spectra of some active galactic nuclei (AGNs) is that they are associated with sub-parsec supermassive black hole (SMBH) binaries. Here, we test the binary broad-line region hypothesis through several decades of monitoring of the velocity structure of double-peaked H-alpha emission lines in 13 low-redshift, mostly radio-loud AGNs. This is a much larger set of objects compared to an earlier test by Eracleous et al. (1997) and we use much longer time series for the three objects studied in that pa…
In the manuscript, the blue quasar SDSS J105816.19+544310.2 (=SDSS J1058+5443) at redshift 0.479 is reported as so-far the best candidate of true type-2 quasar with disappearance of central BLRs. There are so-far no definite conclusions on the very existence of true type-2 AGN, mainly due to detected optical broad emission lines in high quality spectra of some previously classified candidates of true type-2 AGN. Here, not similar as previous reported candidates for true type-2 AGN among narrow emission-line galaxies with weak AGN activities but strong stellar lights, the definite blue quasar S…
Many classes of active galactic nuclei (AGN) have been observed and recorded since the discovery of Seyfert galaxies. In this paper, we examine the sample of luminous galaxies in the Baryon Oscillation Spectroscopic Survey (BOSS). We find a potentially new observational class of AGN, one with strong and broad MgII $2799$Å line emission, but very weak emission in other normal indicators of AGN activity, such as the broad line H$α$, H$β$, and the near-ultraviolet AGN continuum, leading to an extreme ratio of broad H$α$/MgII flux relative to normal quasars. Meanwhile, these objects' narrow-line f…
Soft X-ray emission (0.5--2.0 keV) plays a pivotal role in regulating the optical and UV emission in the AGNs. We collected a sample of 1811 AGNs from the SDSS database and obtained various parameters of Balmer lines, optical continuum, MgII line \& UV continuum and studied their dependencies on soft X-ray luminosity. Based on the linear regression analysis, we found that FWHM$_{\text{MgII}}$ $\propto$ FWHM$_{\text{H}β}^{0.554}$ suggesting that UV emission is arising from a region relatively outside the broad line region (BLR) associated to the H$β$ emission and found a strong correlation betw…
Optical spectropolarimetry of extreme H$α$ line profiles in seven active galactic nuclei
Université de Strasbourg, CNRS, Observatoire astronomique de Strasbourg（斯特拉斯堡大学）；Institut d’Astrophysique et de Géophysique, Université de Liège（列日大学天体物理学与地球物理学研究所）；Department of Astronomy and Astrophysics, University of California at Santa Cruz（加州大学圣克鲁斯分校天文学与天体物理系）
The X-Ray Dot: Exotic Dust or a Late-Stage Little Red Dot?
Max-Planck-Institut für Astronomie（马克斯·普朗克天文学研究所）；Center for Astrophysics, Harvard & Smithsonian（哈佛与史密森尼天体物理中心）；Department of Astrophysical Sciences, Princeton University（普林斯顿大学天体物理学系）；Leiden Observatory, Leiden University（莱顿大学莱顿天文台）；Department of Physics, University of Oxford（牛津大学物理系）
We present a sample of 33 Balmer Break Galaxies (BBGs) selected as HST/F160W dropouts in the deepest CANDELS/GOODS fields ($H\gtrsim27.3$~mag) but relatively bright in {\it Spitzer}/IRAC ($[3.6],[4.5]<24.5$~mag), implying red colors (median and quartiles: $\langle H-[3.6]\rangle=3.1^{3.4}_{2.8}$\,mag). Half of these BBGs are newly identified sources. Our BBGs are massive ($\langle \log(\rm{M}/\rm{M}_\odot)\rangle=10.8$) high redshift ($\langle z\rangle=4.8$) dusty ($\langle \rm{A(V)}\rangle=2.0$~mag) galaxies. The SEDs of half of our sample indicate that they are star-forming galaxies with typ…
