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.

scholarly journals The ecology of the galactic centre: Nuclear stellar clusters and supermassive black holes

2019 ◽  
Vol 14 (S351) ◽  
pp. 80-83 ◽  
Author(s):  
Melvyn B. Davies ◽  
Abbas Askar ◽  
Ross P. Church
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Large Fraction ◽  
Galactic Nuclei ◽  
Supermassive Black Holes ◽  
Galactic Centre ◽  
Stellar Clusters ◽  
Stellar Cluster ◽  
Supermassive Black Hole ◽  
Multiple Clusters

AbstractSupermassive black holes are found in most galactic nuclei. A large fraction of these nuclei also contain a nuclear stellar cluster surrounding the black hole. Here we consider the idea that the nuclear stellar cluster formed first and that the supermassive black hole grew later. In particular we consider the merger of three stellar clusters to form a nuclear stellar cluster, where some of these clusters contain a single intermediate-mass black hole (IMBH). In the cases where multiple clusters contain IMBHs, we discuss whether the black holes are likely to merge and whether such mergers are likely to result in the ejection of the merged black hole from the nuclear stellar cluster. In some cases, no supermassive black hole will form as any merger product is not retained. This is a natural pathway to explain those galactic nuclei that contain a nuclear stellar cluster but apparently lack a supermassive black hole; M33 being a nearby example. Alternatively, if an IMBH merger product is retained within the nuclear stellar cluster, it may subsequently grow, e.g. via the tidal disruption of stars, to form a supermassive black hole.

scholarly journals Proper motion in lensed radio jets at redshift 3: A possible dual super-massive black hole system in the early Universe

2019 ◽  
Vol 630 ◽  
pp. A108 ◽  
Author(s):  
C. Spingola ◽  
J. P. McKean ◽  
D. Massari ◽  
L. V. E. Koopmans
Keyword(s):  
Active Galactic Nuclei ◽  
Early Universe ◽  
Gravitational Lensing ◽  
Proper Motion ◽  
Galactic Nuclei ◽  
Massive Black Hole ◽  
Radio Jets ◽  
Long Baseline ◽  
Multi Wavelength ◽  
Low Probability

In this paper, we exploit the gravitational lensing effect to detect proper motion in the highly magnified gravitationally lensed source MG B2016+112. We find positional shifts up to 6 mas in the lensed images by comparing two Very Long Baseline Interferometric (VLBI) radio observations at 1.7 GHz that are separated by 14.359 years, and provide an astrometric accuracy of the order of tens of μas. From lens modelling, we exclude a shift in the lensing galaxy as the cause of the positional change of the lensed images, and we assign it to the background source. The source consists of four sub-components separated by ∼175 pc, with proper motion of the order of tens μas yr−1 for the two components at highest magnification (μ ∼ 350) and of the order of a few mas yr−1 for the two components at lower magnification (μ ∼ 2). We propose single active galactic nuclei (AGN) and dual AGN scenarios to explain the source plane. Although, the latter interpretation is supported by the archival multi-wavelength properties of the object. In this case, MG B2016+112 would represent the highest redshift dual radio-loud AGN system discovered thus far, and would support the merger interpretation for such systems. Also, given the low probability (∼10−5) of detecting a dual AGN system that is also gravitationally lensed, if confirmed, this would suggest that such dual AGN systems must be more abundant in the early Universe than currently thought.

scholarly journals Resolving accretion flows in nearby active galactic nuclei with the Event Horizon Telescope

2019 ◽  
Vol 490 (4) ◽  
pp. 4606-4621
Author(s):  
Bidisha Bandyopadhyay ◽  
Fu-Guo Xie ◽  
Neil M Nagar ◽  
Dominik R G Schleicher ◽  
Venkatessh Ramakrishnan ◽  
...  
Keyword(s):  
Active Galactic Nuclei ◽  
Event Horizon ◽  
Spectral Energy Distribution ◽  
Galactic Nuclei ◽  
Integration Time ◽  
Spectral Energy ◽  
Model Parameters ◽  
Jet Formation ◽  
Accretion Flows ◽  
Long Baseline

ABSTRACT The Event Horizon Telescope (EHT), now with its first ever image of the photon ring around the supermassive black hole of M87, provides a unique opportunity to probe the physics of supermassive black holes through Very Long Baseline Interferometry (VLBI), such as the existence of the event horizon, the accretion processes as well as jet formation in low-luminosity AGNs (LLAGNs). We build a theoretical model that includes an advection dominated accretion flow (ADAF) with emission from thermal and non-thermal electrons in the flow and a simple radio jet outflow. The predicted spectral energy distribution (SED) of this model is compared to sub-arcsec resolution observations to get the best estimates of the model parameters. The model-predicted radial emission profiles at different frequency bands are used to predict whether the inflow can be resolved by the EHT or with telescopes such as the Global 3-mm VLBI array (GMVA). In this work the model is initially tested with high-resolution SED data of M87 and then applied to our sample of five galaxies (Cen A, M84, NGC 4594, NGC 3998, and NGC 4278). The model then allows us to predict if one can detect and resolve the inflow for any of these galaxies using the EHT or GMVA within an 8 h integration time.

scholarly journals Recoiling Black Holes: Electromagnetic Signatures, Candidates, and Astrophysical Implications

2012 ◽  
Vol 2012 ◽  
pp. 1-8 ◽  
Author(s):  
S. Komossa
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Active Galactic Nuclei ◽  
Galactic Nuclei ◽  
Host Galaxies ◽  
Wide Range ◽  
Galaxy Cores ◽  
Galaxy Assembly ◽  
Anisotropic Emission

Supermassive black holes (SMBHs) may not always reside right at the centers of their host galaxies. This is a prediction of numerical relativity simulations, which imply that the newly formed single SMBH, after binary coalescence in a galaxy merger, can receive kick velocities up to several 1000 km/s due to anisotropic emission of gravitational waves. Long-lived oscillations of the SMBHs in galaxy cores, and in rare cases even SMBH ejections from their host galaxies, are the consequence. Observationally, accreting recoiling SMBHs would appear as quasars spatially and/or kinematically offset from their host galaxies. The presence of the “kicks” has a wide range of astrophysical implications which only now are beginning to be explored, including consequences for black hole and galaxy assembly at the epoch of structure formation, black hole feeding, and unified models of active galactic nuclei (AGN). Here, we review the observational signatures of recoiling SMBHs and the properties of the first candidates which have emerged, including follow-up studies of the candidate recoiling SMBH of SDSSJ092712.65+294344.0.

The Biggest Eyes in the Sky: The EHT

2020 ◽  
pp. 177-202
Author(s):  
John W. Moffat
Keyword(s):  
Black Holes ◽  
Event Horizon ◽  
Accretion Disks ◽  
Bright Light ◽  
Supermassive Black Holes ◽  
Western Hemisphere ◽  
Sagittarius A ◽  
Long Baseline ◽  
The Galaxy ◽  
International Event

The international Event Horizon Telescope (EHT) project aims to observe the supermassive black holes at the centers of galaxies, such as Sagittarius A* at the center of the Milky Way and the more distant M87* in the galaxy M87. Using Very-Long-Baseline Interferometry, the project can observe the shadows of the supermassive black holes that block the bright light emitted by their accretion disks. The EHT ties together radio telescopes ranging across the western hemisphere of Earth to create, in effect, a planet-size telescope. The EHT will determine the size of the shadow, which can be compared to the predictions of general relativity and modified gravity theories. The EHT will also observe the physics of the accretion disks surrounding supermassive black holes. These observations can potentially determine whether a black hole event horizon exists.

scholarly journals Event horizon scale emission models for Sagittarius A*

2013 ◽  
Vol 9 (S303) ◽  
pp. 298-302
Author(s):  
J. Dexter
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Event Horizon ◽  
Near Infrared ◽  
Sagittarius A ◽  
Long Baseline ◽  
Black Hole Accretion ◽  
Emission Models ◽  
Infrared Interferometry ◽  
Sgr A

AbstractVery long baseline interferometry observations at millimeter wavelengths have detected source structure in Sgr A* on event horizon scales. Near-infrared interferometry will achieve similar resolution in the next few years. These experiments provide an unprecedented opportunity to explore strong gravity around black holes, but interpreting the data requires physical modeling. I discuss the calculation of images, spectra, and light curves from relativistic MHD simulations of black hole accretion. The models provide an excellent description of current observations, and predict that we may be on the verge of detecting a black hole shadow, which would constitute the first direct evidence for the existence of black holes.

scholarly journals Global alignments of parsec-scale AGN radio jets and their polarization planes

2020 ◽  
Vol 635 ◽  
pp. A102 ◽  
Author(s):  
D. Blinov ◽  
C. Casadio ◽  
N. Mandarakas ◽  
E. Angelakis
Keyword(s):  
Active Galactic Nuclei ◽  
Large Scale ◽  
Very Long Baseline Interferometry ◽  
Parallel Transport ◽  
Polarization Plane ◽  
Galactic Nuclei ◽  
Radio Jets ◽  
Long Baseline ◽  
Flux Density Distribution ◽  
First Time

Context. A number of works have reported that the polarization plane of extragalactic sources as well as the structural axes of radio sources are aligned on the large scale. However, both the claims and their interpretation remain controversial. Aims. For the first time, we explore the alignment of parsec-scale jets. Additionally, we use archival polarimetric data at different wavelengths in order to compare the relative orientations of the jets and the polarization planes of their emission. Methods. Using the flux density distribution in very long baseline interferometry radio maps from the Astrogeo database, we determine the parsec-scale jet orientation for the largest sample of active galactic nuclei to date. Employing the method of parallel transport and a sample statistics characterizing the jet orientation dispersion among neighbors, we test whether the identified jets are significantly aligned. Results. We show that the parsec-scale jets in our sample do not demonstrate any significant global alignments. Moreover, the jet direction is found to be weakly correlated with the direction of the polarization plane at different frequencies.

scholarly journals Determination of magnetic field strength on the event horizon of supermassive black holes in active galactic nuclei

2020 ◽  
Vol 495 (1) ◽  
pp. 614-620
Author(s):  
M Yu Piotrovich ◽  
A G Mikhailov ◽  
S D Buliga ◽  
T M Natsvlishvili
Keyword(s):  
Magnetic Field ◽  
Black Holes ◽  
Field Strength ◽  
Active Galactic Nuclei ◽  
Magnetic Field Strength ◽  
Event Horizon ◽  
Galactic Nuclei ◽  
Supermassive Black Holes ◽  
Mean Values ◽  
The Magnetic Field

ABSTRACT We estimated the magnetic field strength at the event horizon for a sample of supermassive black holes (SMBHs) in active galactic nuclei (AGNs). Our estimates were made using the values of the inclination angles of the accretion disc to the line of sight, which we obtained previously from spectropolarimetric observations in the visible spectrum. We also used published values of full width at half-maximum of spectral line Hβ from broad-line region, masses of SMBHs, and luminosity of AGNs at 5100 $\mathring{\rm A}$. In addition, we used the literature data on the spins of SMBHs obtained from their X-ray spectra. Our estimates showed that the magnetic field strength at the event horizon of the majority of SMBHs in AGNs range from several to tens of kG and have mean values of about 104 G. At the same time, for individual objects, the fields are significantly larger – of the order of hundreds kG or even 1 MG.

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).

Sign in / Sign up

Export Citation Format

Share Document