Article
Astronomy & Astrophysics
Juan A. Fernandez-Ontiveros, Teo Munoz-Darias
Summary: The luminosity-excitation diagram (LED) based on mid-infrared nebular line fluxes reveals accretion states in active galactic nuclei (AGN). Soft state and hard state mainly appear in low-luminosity AGN, characterized by disc-dominated nuclei and nuclei with negligible disc contributions, respectively.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
E. Lopez-Navas, P. Sanchez-Saez, P. Arevalo, S. Bernal, M. J. Graham, L. Hernandez-Garcia, D. Homan, M. Krumpe, G. Lamer, P. Lira, M. L. Martinez-Aldama, A. Merloni, S. Rios, M. Salvato, D. Stern, D. Tubin-Arenas
Summary: In this study, second epoch optical spectra for 30 changing-look (CL) candidates were presented. These candidates were found by searching for Type-1 optical variability in a sample of active galactic nuclei (AGNs) spectroscopically classified as Type 2. Through the use of a random-forest-based light-curve classifier and spectroscopic follow-up, 50% of the candidates were confirmed as turning-on CLs. The study also included a multiwavelength variability analysis to improve the selection method and understand the nature of not-confirmed CL candidates.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
Vivek Kumar Jha, Ravi Joshi, Hum Chand, Xue-Bing Wu, Luis C. Ho, Shantanu Rastogi, Qinchun Ma
Summary: In this study, we estimate the accretion disc sizes for a sample of 19 active galactic nuclei (AGNs) using optical light curves from the Zwicky Transient Facility survey. The findings suggest that the g-r band lags are shorter than the g-i band lags as expected from disc-reprocessing arguments. Furthermore, the interband lags for most sources are larger than the sizes predicted by the standard Shakura Sunyaev (SS) analytical model. We also observe a weak correlation between disc sizes and physical parameters such as luminosity and supermassive black hole (SMBH) mass.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
V. A. Fawcett, D. M. Alexander, D. J. Rosario, L. Klindt, E. Lusso, L. K. Morabito, G. Calistro Rivera
Summary: We have found fundamental differences in the radio properties of red quasars when compared to typical blue quasars. Dust reddening can fully explain the observed colours for the majority of the red quasars, and there are no significant differences in the accretion properties between red and blue quasars. The radio emission is more closely connected to circumnuclear/ISM opacity.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
Daniel Kynoch, Hermine Landt, Maryam Dehghanian, Martin J. Ward, Gary J. Ferland
Summary: This study presents the first detailed investigation into the variability of the near-infrared coronal lines in AGN. It is found that the coronal lines in AGN are generally broader and blueshifted compared to low-ionization forbidden lines. The variability primarily occurs in the broad wings of the coronal line profiles, while the cores show negligible changes. This suggests the presence of at least two coronal line regions in AGN.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
D. A. Starkey, Jiamu Huang, Keith Horne, Douglas N. C. Lin
Summary: We propose a solution to the problem of accretion disc sizes in active galactic nuclei being larger when measured by reverberation mapping than predicted by theory, which involves a steep rim or rippled structures irradiated by the central lamp-post.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
E. Lopez-Navas, P. Arevalo, S. Bernal, Matthew J. Graham, L. Hernandez-Garcia, P. Lira, P. Sanchez-Saez
Summary: This study explores different variability features to distinguish between obscured Type 2 AGNs and variable Type 1s. By analyzing the Zwicky Transient Facility light curves of 15000 AGNs, it is found that weak Type 1s exhibit larger variances than Type 2s. Approximately 11% of Type 2 sources show evidence for optical variations when limiting the variability features.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
C. Martin Gaskell, Kayla Bartel, Julia N. Deffner, Iris Xia
Summary: The study found that anomalous responses of the BLR are very common and likely occur in every object. The anomalies can begin on a timescale only slightly longer than the light-crossing time and last for a duration of the order of the characteristic timescale of variability of the optical continuum. Anomalies are larger when NGC 5548 is in a low state, but otherwise show no correlation with continuum variability.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
Amy L. Rankine, James H. Matthews, Paul C. Hewett, Manda Banerji, Leah K. Morabito, Gordon T. Richards
Summary: By investigating the low-frequency radio and ultraviolet properties of a sample of around 10,500 quasars, it was found that the radio detection rate increases with blueshift while the radio-loud fraction decreases. The radio-quiet population shows a range of He II equivalent widths, while the radio-loud population mostly exhibits strong He II. The presence of similar ultraviolet properties but differing radio properties among quasars suggests that radio and ultraviolet emission may be tracing activity occurring on different time-scales.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
X. Xiang, D. R. Ballantyne, S. Bianchi, A. De Rosa, G. Matt, R. Middei, P-o Petrucci, A. Rozanska, F. Ursini
Summary: The X-ray spectra of active galactic nuclei (AGNs) often exhibit an excess of emission at energies less than or similar to 2 keV, known as the 'soft excess'. This excess emission could be originated from ionized relativistic reflection from the inner accretion disk or Comptonization of thermal emission in a warm corona. The reXcor model combines these two effects, providing predictions for various soft excess shapes and sizes.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
Mehdy Lefkir, Elias Kammoun, Didier Barret, Peter Boorman, Gabriele Matzeu, Jon M. Miller, Emanuele Nardini, Abderahmen Zoghbi
Summary: In this study, the X-ray properties of the highly variable AGN NGC 7582 are explored using XMM-Newton and NuSTAR archival observations. The results show long-term variability between observations and short-term variability within two observations, which has not been studied before. The best model for the X-ray properties of NGC 7582 is found to be a fully covering clumpy absorber, with obscuring clouds consistent with comet-like or spherical clouds with a non-uniform density profile.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
N. Chang, F. G. Xie, X. Liu, L. C. Ho, A-J Dong, Z. H. Han, X. Wang
Summary: The study re-analyzed a sample of Seyfert galaxies and found similarities in the X-ray origin of radio-quiet and radio-loud Seyferts, with all sources exhibiting a similar correlation slope. When considering luminosities in radio and X-rays, radio morphology and Seyfert classification played a role in the correlations observed.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
Kastytis Zubovas, Andrew King
Summary: The study creates tighter constraints on the formation and growth mechanisms of early black holes. It shows that chaotic accretion leads to slower growth with lower radiative efficiency, while aligned accretion results in higher spin and radiative efficiency thus slowing down growth. The density of extreme quasars suggests that only a small fraction of seed black holes need favorable conditions to produce observed extreme quasars.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
Kastytis Zubovas, Andrew King
Summary: The study suggests that even the most extreme black hole known as Poniua'ena can grow from a seed black hole via chaotic accretion, with accretion events needing to be almost continuous and individually uncorrelated. However, if a portion of accretion events occur in the same direction, the black hole's growth rate slows down significantly.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
Jiachen Jiang, Luigi C. Gallo, Dirk Grupe, Michael L. Parker
Summary: The study presents a spectral analysis of XMM-Newton observations of UGC 11763, indicating three spectral models that can explain the X-ray variability of the galaxy. Future high-resolution X-ray missions will help to further test these models on UGC 11763.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
A. C. Fabian, G. J. Ferland, J. S. Sanders, B. R. McNamara, C. Pinto, S. A. Walker
Summary: The cooling rate of hot gas in the centers of cool cores in galaxy clusters is very low, but using an intrinsic absorption model, hidden cooling flows with mass cooling rates ranging from 10 to 500 M-circle dot yr(-1) are found in different clusters, with the absorbed emission detected in the far-infrared band. The total mass of cooled gas implied is much larger than the observed molecular masses.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
P. Alimohamadi, G. J. Ferland
Summary: The partition function, U, is crucial for understanding the physical state of astrophysical systems in thermodynamic equilibrium. This article discusses the numerical value and calculations of the partition function, highlighting its divergence at high temperatures and the uncertainties involved, especially in high-density plasmas.
PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF THE PACIFIC
(2022)
Article
Astronomy & Astrophysics
Priyanka Chakraborty, Gary J. Ferland, Marios Chatzikos, Andrew C. Fabian, Stefano Bianchi, Francisco Guzman, Yuanyuan Su
Summary: This paper discusses the impact of optical depth effects such as photoelectric absorption and electron scattering on soft X-ray spectra, as well as the enhancement of soft X-ray line intensities in a photoionized environment through continuum pumping. The suppression/enhancement is quantified using a line modification factor. The study also applies the theory to fitting the spectrum of V1223 Sgr and explains the excess flux for certain lines that couldn't be explained by an absorbed cooling-flow model.
ASTROPHYSICAL JOURNAL
(2022)
Article
Astronomy & Astrophysics
N. Arakawa, A. C. Fabian, G. J. Ferland, W. Ishibashi
Summary: Radiation pressure-driven outflows from luminous accreting supermassive black holes are crucial for active galactic nucleus (AGN) feedback. This study uses radiation simulations and a cloudy code to reveal the outflow region, investigate the impact of AGN and dust properties, and explore the boundary with absorption clouds.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
Daniel Kynoch, Hermine Landt, Maryam Dehghanian, Martin J. Ward, Gary J. Ferland
Summary: This study presents the first detailed investigation into the variability of the near-infrared coronal lines in AGN. It is found that the coronal lines in AGN are generally broader and blueshifted compared to low-ionization forbidden lines. The variability primarily occurs in the broad wings of the coronal line profiles, while the cores show negligible changes. This suggests the presence of at least two coronal line regions in AGN.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
C. R. O'Dell, G. J. Ferland, J. E. Mendez-Delgado
Summary: Examination of emission lines in high-resolution optical spectra of the Orion Nebula confirms that the red wing of the main ionization front emission line is caused by backscattering in the Photon Dominated Region. The scattered light component has a weak wavelength dependence, possibly from interstellar medium particles or foreground particles in the Orion Nebula Cluster. An anomalous line-broadening component, known for over 60 years, is characterized in unprecedented detail, and it could be due to turbulence or Alfven waves in ionized gas with equal and constant magnetic and thermal energies.
ASTRONOMICAL JOURNAL
(2023)
Article
Astronomy & Astrophysics
Pu Du, Jian-Min Wang
Summary: There is evidence of regular substructures, such as spiral arms, in broad-line regions (BLRs) of active galactic nuclei (AGNs), which are consistent with self-gravitating regions of accretion disks. This study investigates the loosely wound spiral arms excited by gravitational instabilities and their observational characteristics in disk-like BLRs. The results show that these spiral arms can explain various phenomena observed, including asymmetries in emission-line profiles, complex subfeatures in velocity-delay maps, and short timescales of asymmetry changes in emission-line profiles.
ASTRONOMY & ASTROPHYSICS
(2023)
Article
Astronomy & Astrophysics
Pu Du, Shuo Zhai, Jian-Min Wang
Summary: Reverberation mapping (RM) is widely used to study the physics of broad-line regions (BLRs) in active galactic nuclei (AGNs). This paper investigates the influence of BLR densities on RM behaviors using a locally optimally emitting cloud model. The results reveal that rarefied BLRs may exhibit anomalous responses, different BLR densities can affect the correlations between time lags and equivalent widths of emission lines, and variations in BLR densities can explain changes in time lags in individual objects for different years.
ASTROPHYSICAL JOURNAL
(2023)
Article
Astronomy & Astrophysics
Yan-Rong Li, Jian-Min Wang
Summary: Spectroastrometry is a method of measuring astrometry of sources based on wavelength/velocity variations. It can be used to study the broad-line regions (BLRs) of active galactic nuclei (AGNs), providing a new diagnostic tool for mapping BLR kinematics and geometry. This study presents a mathematical formalism for spectroastrometric reverberation mapping (RM) and demonstrates its potential in resolving BLR properties. A Bayesian framework is developed to analyze spectroastrometric data and infer the central black hole mass and angular-size distance of the BLR.
ASTROPHYSICAL JOURNAL
(2023)
Article
Astronomy & Astrophysics
Tom Rose, B. R. McNamara, F. Combes, A. C. Edge, A. C. Fabian, M. Gaspari, H. Russell, P. Salome, G. Tremblay, G. Ferland
Summary: Galaxies often contain large amounts of molecular gas that influence their evolution. This gas can lead to star formation or fuel active galactic nucleus (AGN) activity and produce strong feedback. By using absorption against radio cores, ALMA has found molecular gas in brightest cluster galaxies moving towards their galaxy's core at high velocities. This paper compares the molecular emission and absorption in these galaxies to determine the location of the absorbing gas and finds two types of absorbers: those aligned with a fraction of the emitting molecular clouds and those close to the AGN in the accretion process. The paper also presents ALMA observations of molecular emission in S555, Abell 2390, RXC J1350.3+0940, and RXC J1603.6+1553, with the latter three having molecular gas masses greater than 10^10 solar masses.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
Y. Homayouni, Gisella De Rosa, Rachel Plesha, Gerard A. Kriss, Aaron J. Barth, Edward M. Cackett, Keith Horne, Erin A. Kara, Hermine Landt, Nahum Arav, Benjamin D. Boizelle, Misty C. Bentz, Thomas G. Brink, Michael S. Brotherton, Doron Chelouche, Elena Dalla Bonta, Maryam Dehghanian, Pu Du, Gary J. Ferland, Laura Ferrarese, Carina Fian, Alexei V. Filippenko, Travis Fischer, Ryan J. Foley, Jonathan Gelbord, Michael R. Goad, Diego H. Gonzalez Buitrago, Varoujan Gorjian, Catherine J. Grier, Patrick B. Hall, Juan V. Hernandez Santisteban, Chen Hu, Dragana Ilic, Michael D. Joner, Jelle Kaastra, Shai Kaspi, Christopher S. Kochanek, Kirk T. Korista, Andjelka B. Kovacevic, Daniel Kynoch, Yan-Rong Li, Ian M. McHardy, Jacob N. McLane, Missagh Mehdipour, Jake A. Miller, Jake Mitchell, John Montano, Hagai Netzer, Christos Panagiotou, Ethan Partington, Richard W. Pogge, Luka C. Popovic, Daniel Proga, Daniele Rogantini, Thaisa Storchi-Bergmann, David Sanmartim, Matthew R. Siebert, Tommaso Treu, Marianne Vestergaard, Jian-Min Wang, Martin J. Ward, Tim Waters, Peter R. Williams, Fatima Zaidouni, Ying Zu
Summary: Reverberation mapping measurements were conducted on the ultraviolet broad emission lines of Mrk 817, an active galactic nucleus, using the Cosmic Origins Spectrograph on the Hubble Space Telescope. Correlated variations between the continuum and emission-line light curves were found, and delayed responses to continuum variations were measured for various emission lines. Velocity-resolved lags were also measured for the Ly alpha and C IV emission lines.
ASTROPHYSICAL JOURNAL
(2023)
Article
Astronomy & Astrophysics
Yu-Yang Songsheng, Jian-Min Wang
Summary: Pairs of supermassive black holes (SMBHs) at different stages are the natural result of galaxy mergers in the hierarchical framework of galaxy formation and evolution. Recent advancements in spatial resolutions have provided new opportunities to identify close binaries of SMBHs (CB-SMBHs) with sub-parsec separations through spectroastrometry (SA) observations. The distinctive structures of the differential phase curves of CB-SMBHs with two independent broad-line regions (BLRs) can help in their identification and eventually resolve them as sources of nanohertz gravitational waves.
ASTROPHYSICAL JOURNAL
(2023)
Article
Astronomy & Astrophysics
A. C. Fabian, J. S. Sanders, G. J. Ferland, B. R. McNamara, C. Pinto, S. A. Walker
Summary: We have discovered Hidden Cooling Flows (HCFs) in the spectra of three clusters of galaxies using the XMM Reflection Grating Spectrometer. We extended our search to a wider sample of objects and found HCFs in six clusters and two elliptical galaxies. The cooling rates vary from 5-40 M-? yr(-1) for normal clusters, over 1000 M-? yr(-1) for extreme clusters, and 1-2 M-? yr(-1) for elliptical galaxies. The implications of these findings for the composition of galaxies' innermost parts are discussed, and further observations are anticipated.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
Viraja C. Khatu, Sarah C. Gallagher, Keith Horne, Edward M. Cackett, Chen Hu, Pu Du, Jian-Min Wang, Wei-Hao Bian, Jin-Ming Bai, Yong-Jie Chen, Patrick Hall, Bo-Wei Jiang, Sha-Sha Li, Yan-Rong Li, Sofia Pasquini, Yu-Yang Songsheng, Chan Wang, Ming Xiao, Zhe Yu
Summary: Measuring broad emission-line widths in AGNs is challenging due to flux variability, especially in low signal-to-noise ratio, narrow profiles, and low spectral resolution. We analyzed the emission-line measurements of Mrk 142 obtained from two telescopes and found disparities in the measured broad-line widths. By fixing the narrow-line flux ratios, we improved the measurement accuracy of the broad-line widths in the lower-resolution spectra.
PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF THE PACIFIC
(2023)