scholarly journals BAT AGN Spectroscopic Survey – XVII. The parsec-scale jet properties of the ultrahard X-ray-selected local AGNs

2019 ◽  
Vol 488 (3) ◽  
pp. 4317-4328 ◽  
Author(s):  
Junhyun Baek ◽  
Aeree Chung ◽  
Kevin Schawinski ◽  
Kyuseok Oh ◽  
O Ivy Wong ◽  
...  
Keyword(s):  
Galactic Nuclei ◽  
Archival Data ◽  
Imaging Data ◽  
X Ray ◽  
Tidal Interactions ◽  
Long Baseline ◽  
Hydrogen Column Density ◽  
Wide Range ◽  
Burst Alert Telescope ◽  
Gas Supply

ABSTRACT We have performed a very long baseline interferometry (VLBI) survey of local (z < 0.05) ultrahard X-ray (14–195 keV) selected active galactic nuclei (AGNs) from the Swift Burst Alert Telescope (BAT) using KVN, KaVA, and VLBA. We first executed fringe surveys of 142 BAT-detected AGNs at 15 or 22 GHz. Based on the result from the fringe surveys and archival data, we find 10/279 nearby AGN (∼4 per cent) VLBI have 22 GHz flux above 30 mJy. This implies that the X-ray AGNs with a bright nuclear jet are not common. Among these 10 radio-bright AGNs, we obtained 22 GHz VLBI imaging data of our own for four targets and reprocessed archival data for six targets. We find that, although our 10 AGNs observed with VLBI span a wide range of pc-scale morphological types, they lie on a tight linear relation between accretion luminosity and nuclear jet luminosity. Our result suggests that a powerful nuclear radio jet correlates with the accretion disc luminosity. We also probed the Fundamental Plane of black hole activity at VLBI scales (e.g. few milliarcsecond). The jet luminosity and size distribution among our sample roughly fit into the proposed AGN evolutionary scenario, finding powerful jets after the blow-out phase based on the Eddington ratio (λEdd)–hydrogen column density (NH) relation. In addition, we find some hints of gas inflow or galaxy–galaxy merger in the majority of our sample. This implies that gas supply via tidal interactions in galactic scale may help the central AGN to launch a powerful parsec-scale jet.

scholarly journals Event Horizon Telescope observations of the jet launching and collimation in Centaurus A

2021 ◽  
Author(s):  
Michael Janssen ◽  
Heino Falcke ◽  
Matthias Kadler ◽  
Eduardo Ros ◽  
Maciek Wielgus ◽  
...  
Keyword(s):  
Black Holes ◽  
Event Horizon ◽  
Galactic Nuclei ◽  
Galactic Centre ◽  
Radio Jets ◽  
Long Baseline ◽  
Wide Range ◽  
Terahertz Frequencies ◽  
Source Structure ◽  
Centaurus A

AbstractVery-long-baseline interferometry (VLBI) observations of active galactic nuclei at millimetre wavelengths have the power to reveal the launching and initial collimation region of extragalactic radio jets, down to 10–100 gravitational radii (rg ≡ GM/c2) scales in nearby sources1. Centaurus A is the closest radio-loud source to Earth2. It bridges the gap in mass and accretion rate between the supermassive black holes (SMBHs) in Messier 87 and our Galactic Centre. A large southern declination of −43° has, however, prevented VLBI imaging of Centaurus A below a wavelength of 1 cm thus far. Here we show the millimetre VLBI image of the source, which we obtained with the Event Horizon Telescope at 228 GHz. Compared with previous observations3, we image the jet of Centaurus A at a tenfold higher frequency and sixteen times sharper resolution and thereby probe sub-lightday structures. We reveal a highly collimated, asymmetrically edge-brightened jet as well as the fainter counterjet. We find that the source structure of Centaurus A resembles the jet in Messier 87 on ~500 rg scales remarkably well. Furthermore, we identify the location of Centaurus A’s SMBH with respect to its resolved jet core at a wavelength of 1.3 mm and conclude that the source’s event horizon shadow4 should be visible at terahertz frequencies. This location further supports the universal scale invariance of black holes over a wide range of masses5,6.

Large-Amplitude X-Ray Outbursts from Galactic Nuclei: A Systematic Survey using [ITAL]ROSAT[/ITAL] Archival Data

2002 ◽  
Vol 124 (3) ◽  
pp. 1308-1321 ◽  
Author(s):  
J. L. Donley ◽  
W. N. Brandt ◽  
Michael Eracleous ◽  
Th. Boller
Keyword(s):  
Large Amplitude ◽  
Galactic Nuclei ◽  
Archival Data ◽  
X Ray ◽  
Systematic Survey

scholarly journals Quasars as standard candles II

2019 ◽  
Vol 631 ◽  
pp. A120 ◽  
Author(s):  
F. Salvestrini ◽  
G. Risaliti ◽  
S. Bisogni ◽  
E. Lusso ◽  
C. Vignali
Keyword(s):  
Active Galactic Nuclei ◽  
Rest Frame ◽  
Galactic Nuclei ◽  
Observational Cosmology ◽  
X Ray ◽  
Uv Emission ◽  
Wide Range ◽  
Photon Index ◽  
Lower Redshift

A tight non-linear relation between the X-ray and the optical-ultraviolet (UV) emission has been observed in active galactic nuclei (AGN) over a wide range of redshift and several orders of magnitude in luminosity, suggesting the existence of an ubiquitous physical mechanism regulating the energy transfer between the accretion disc and the X-ray emitting corona. Recently, our group developed a method to use this relation in observational cosmology, turning quasars into standardizable candles. This work mainly seeks to investigate the potential evolution of this correction at high redshifts. We thus studied the LX − LUV relation for a sample of quasars in the redshift range 4 <  z <  7, adopting the selection criteria proposed in our previous work regarding their spectral properties. The resulting sample consists of 53 type 1 (unobscured) quasars, observed either with Chandra or XMM-Newton, for which we performed a full spectral analysis, determining the rest-frame 2 keV flux density, as well as more general X-ray properties such as the estimate of photon index, and the soft (0.5–2 keV) and hard (2–10 keV) unabsorbed luminosities. We find that the relation shows no evidence for evolution with redshift. The intrinsic dispersion of the LX–LUV for a sample free of systematics/contaminants is of the order of 0.22 dex, which is consistent with previous estimates from our group on quasars at lower redshift.

scholarly journals Are Compton-thin AGNs Globally Compton Thin?

2021 ◽  
Vol 922 (1) ◽  
pp. 85
Author(s):  
P. Tzanavaris ◽  
T. Yaqoob ◽  
S. LaMassa ◽  
A. Ptak ◽  
M. Yukita
Keyword(s):  
Emission Line ◽  
Active Galactic Nuclei ◽  
Column Density ◽  
Line Emission ◽  
Galactic Nuclei ◽  
Line Of Sight ◽  
X Ray ◽  
Hydrogen Column Density ◽  
Model Configuration

Abstract We select eight nearby active galactic nuclei (AGNs) which, based on previous work, appear to be Compton-thin in the line of sight. We model with mytorus their broadband X-ray spectra from 20 individual observations with Suzaku, accounting self-consistently for Fe Kα line emission, as well as direct and scattered continuum from matter with finite column density and solar Fe abundance. Our model configuration allows us to measure the global, out of the line of sight, equivalent hydrogen column density separately from that in the line of sight. For 5 out of 20 observations (in 3 AGNs) we find that the global column density is in fact ≳1.5 × 1024 cm−2, consistent with the distant scattering matter being Compton-thick. For a fourth AGN, two out of five observations are also consistent with being Compton-thick, although with large errors. Some of these AGNs have been reported to host relativistically broadened Fe Kα emission. Based on our modeling, the Fe Kα emission line is not resolved in all but two Suzaku observations, and the data can be fitted well with models that only include a narrow Fe Kα emission line.

Magnetic Fields in the Relativistic Jets of Active Galactic Nuclei

2018 ◽  
Vol 14 (S342) ◽  
pp. 189-196
Author(s):  
Denise C. Gabuzda
Keyword(s):  
Active Galactic Nuclei ◽  
Very Long Baseline Interferometry ◽  
Galactic Nuclei ◽  
Outward Current ◽  
Relativistic Jets ◽  
Local Effects ◽  
Very Large Array ◽  
Long Baseline ◽  
Wide Range ◽  
Jet Axis

AbstractAn abundance of information about the magnetic (B) fields of relativistic AGN jets has been obtained through radio polarization observations made on a wide range of scales, from the parsec scales probed by Very Long Baseline Interferometry to the kiloparsec scales probed by instruments such as the the Jansky Very Large Array and e-MERLIN. The observed radio emission is synchrotron radiation, for which the linear polarization angles in optically thin regions is orthogonal to the local synchrotron B fields. The characteristic B field structures observed for these jets on parsec scales are described. A key question is whether B field structures observed in particular AGN jets come about primarily due to “global” effects such as the intrinsic B field of the jet itself, which is expected to be helical, or local phenomena such as shocks, shear and bending of the jets. Observational criteria that can be used to try to distinguish between various possible origins for observed B field structures are described. There is now considerable evidence that the relativistic jets of AGNs do indeed carry helical B fields, with the observed polarization also sometimes appreciably influenced by local effects. Patterns seen in the helical B field components, indicated for example by Faraday rotation observations, provide unique information about the processes involved in the generation of these helical B fields. The collected observations on parsec and kiloparsec scales provide weighty evidence that an important role is played by the action of a cosmic “battery” that acts to generate an inward current along the jet axis and an outward current in a more extended region surrounding the jet.

scholarly journals Mapping the active Universe with eROSITA

2013 ◽  
Vol 9 (S304) ◽  
pp. 421-421
Author(s):  
Mara Salvato
Keyword(s):  
Black Holes ◽  
Large Scale ◽  
Gamma Ray ◽  
Galactic Nuclei ◽  
Binary Black Holes ◽  
X Ray ◽  
Wide Range ◽  
The Galaxy ◽  
Deep Survey ◽  
The Universe

AbstracteROSITA (extended Röntgen Survey with an Imaging Telescope Array) is the core instrument on the Russian Spektrum-Röntgen-Gamma (SRG) mission which is current scheduled for launch in Q4 2014. eROSITA will perform a deep survey of the entire X-ray sky. In the soft band (0.5–2 keV), it will be about 30 times more sensitive than ROSAT, while in the hard band (2–8 keV) it will provide the first ever true imaging survey of the sky. The design driving science is the detection of large samples of galaxy clusters up to redshifts z ~ 1, in order to study the large scale structure in the Universe and test cosmological models including Dark Energy. In addition, eROSITA is expected to yield a sample of about 3 million active galactic nuclei, which is bound to revolutionize our view of the evolution of supermassive black holes and their impact on the process of structure formation in the Universe. The survey will also provide new insights into a wide range of astrophysical phenomena, including isolated Neutron Stars and Black Holes, X-ray binaries, active stars and diffuse emission within the Galaxy, as well as more exotic ones such as gamma-ray bursts, tidal disruption of stars in galactic nuclei and binary black holes. In this talk I presented the main characteristics of the mission and focus on the scientific drivers for extragalactic all-sky surveys of AGN. All what was presented at the Symposium (plots, simulations, expected numbers of various kind of sources –QSO, obscured and CT AGN– their properties and evolution with redshift) can be found in the official eROSITA Science Book (Merloni et al., 2012).

scholarly journals Testing warm Comptonization models for the origin of the soft X-ray excess in AGNs

2018 ◽  
Vol 611 ◽  
pp. A59 ◽  
Author(s):  
P.-O. Petrucci ◽  
F. Ursini ◽  
A. De Rosa ◽  
S. Bianchi ◽  
M. Cappi ◽  
...  
Keyword(s):  
Active Galactic Nuclei ◽  
Large Fraction ◽  
Galactic Nuclei ◽  
High Energy ◽  
Archival Data ◽  
X Rays ◽  
X Ray ◽  
Accretion Flow ◽  
High Energy Tail ◽  
Intrinsic Emission

The X-ray spectra of many active galactic nuclei (AGNs) show a soft X-ray excess below 1–2 keV on top of the extrapolated high-energy power law. The origin of this component is uncertain. It could be a signature of relativistically blurred, ionized reflection or the high-energy tail of thermal Comptonization in a warm (kT ~ 1 keV), optically thick (τ ≃ 10–20) corona producing the optical/UV to soft X-ray emission. The purpose of the present paper is to test the warm corona model on a statistically significant sample of unabsorbed, radio-quiet AGNs with XMM-Newton archival data, providing simultaneous optical/UV and X-ray coverage. The sample has 22 objects and 100 observations. We use two thermal Comptonization components to fit the broadband spectra, one for the warm corona emission and one for the high-energy continuum. In the optical/UV, we also include the reddening, the small blue bump, and the Galactic extinction. In the X-rays, we include a warm absorber and a neutral reflection. The model gives a good fit (reduced χ2 < 1.5) to more than 90% of the sample. We find the temperature of the warm corona to be uniformly distributed in the 0.1–1 keV range, while the optical depth is in the range ~10–40. These values are consistent with a warm corona covering a large fraction of a quasi-passive accretion disk, i.e., that mostly reprocesses the warm corona emission. The disk intrinsic emission represents no more than 20% of the disk total emission. According to this interpretation, most of the accretion power would be released in the upper layers of the accretion flow.

Relativistic astrophysics and cosmology

2019 ◽  
pp. 244-291
Author(s):  
Malcolm S. Longair
Keyword(s):  
Active Galactic Nuclei ◽  
Galactic Nuclei ◽  
High Energy ◽  
Active Galaxies ◽  
Relativistic Astrophysics ◽  
Radio Sources ◽  
X Ray ◽  
Binary Black Hole ◽  
Wide Range ◽  
New Challenges

Although relativistic astrophysics began in the 1930s with study of supernovae and neutron stars, it was only three decades later that the discovery of extragalactic radio sources, quasars and pulsars marked the emergence of special and general relativity as essential tools of the high energy astrophysicist. X-ray and γ-ray astronomy provided many new insights, culminating in the discovery of γ-ray bursts at cosmological distances in 1997. Supermassive black holes in active galactic nuclei provided major new challenges for theorists and observers alike, revealing many remarkable relativistic phenomena, such as superluminal motions observed in some of the most active galaxies. Einstein’s prediction of gravitational waves of 1916 was substantiated exactly 100 years later with their discovery in coalescing binary black hole systems by the LIGO project. These remarkable discoveries, mostly in the non-optical wavebands, brought a wide range of physicists into the astronomical and cosmological communities.

scholarly journals Variability in Active Galactic Nuclei

1993 ◽  
Vol 134 ◽  
pp. 245-547
Author(s):  
M. Matsuoka
Keyword(s):  
Active Galactic Nuclei ◽  
Time Scales ◽  
Galactic Nuclei ◽  
Wide Band ◽  
Seyfert Galaxies ◽  
Time Variability ◽  
X Ray ◽  
Central Engine ◽  
Nearby Region ◽  
Wide Range

AbstractAGN (Active Galactic Nuclei) have their profound time variability over a wide range of time scales. Although many results of AGN variability have been provided from wide band wavelength observations, I would like to concentrate the recent problems concerning a nearby region of their central engine based on the X-ray observations which are most efficient to investigate this region. In this paper we will investigate mainly the result of Seyfert galaxies which would be generalized to other AGN.

scholarly journals Relativistic Fe Kα line in the composite X-ray spectra of radio-loud active galactic nuclei

2019 ◽  
Vol 488 (3) ◽  
pp. 4378-4388
Author(s):  
Jingwei Hu ◽  
Zhu Liu ◽  
Chichuan Jin ◽  
Weimin Yuan
Keyword(s):  
Black Hole ◽  
Active Galactic Nuclei ◽  
Precise Measurement ◽  
Galactic Nuclei ◽  
Relativistic Effects ◽  
Line Profiles ◽  
X Ray ◽  
Wide Range ◽  
Average Spin ◽  
Spectral Profiles

ABSTRACT While a broad Fe Kα emission line is generally found in the X-ray spectra of radio quiet (RQ) active galactic nuclei (AGNs), this feature, commonly thought to be broadened by the relativistic effects near the central black hole, appears to be rare in their radio loud (RL) counterparts. In this paper, we carry out a detailed study of the ensemble property of the X-ray spectra, focusing on the Fe line, of 97 RL AGNs by applying the spectral stacking method to the spectra obtained with XMM–Newton. For comparison, the same analysis is also performed for 193 RQ AGNs. Both a narrow and a broad component of the Fe Kα line are detected at high significance in the stacked spectra of both samples. The broad lines can be well fitted with relativistically broadened line profiles. Our results suggest that, as in their RQ counterparts, a relativistic Fe line component is commonly present in RL AGNs, though it may not be detected unambiguously in individual objects with spectra of relatively low signal to noise. We try to constrain the average spin of the black holes for both the RL and RQ AGN samples by modelling their composite Fe line spectral profiles with relativistic disc line models. For the RL sample, the average spin is loosely constrained and a wide range is allowed except for very fast spins (&lt;0.78, 90 per cent confidence), while for the RQ sample, it is constrained to be low or moderate (&lt;0.24). We conclude that the more precise measurement of the black hole spins in RL AGNs has to await for the advent of future high-throughput X-ray telescopes.

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