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Post Info TOPIC: Messier 87
Blobrana


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RE: Messier 87
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Title: Jet Launching Structure Resolved Near the Supermassive Black Hole in M87
Authors: Sheperd S. Doeleman, Vincent L. Fish, David E. Schenck, Christopher Beaudoin, Ray Blundell, Geoffrey C. Bower, Avery E. Broderick, Richard Chamberlin, Robert Freund, Per Friberg, Mark A. Gurwell, Paul T. P. Ho, Mareki Honma, Makoto Inoue, Thomas P. Krichbaum, James Lamb, Abraham Loeb, Colin Lonsdale, Daniel P. Marrone, James M. Moran, Tomoaki Oyama, Richard Plambeck, Rurik A. Primiani, Alan E. E. Rogers, Daniel L. Smythe, Jason SooHoo, Peter Strittmatter, Remo P. J. Tilanus, Michael Titus, Jonathan Weintroub, Melvyn Wright, Ken H. Young, Lucy M. Ziurys

Approximately 10% of active galactic nuclei exhibit relativistic jets, which are powered by accretion of matter onto super massive black holes. While the measured width profiles of such jets on large scales agree with theories of magnetic collimation, predicted structure on accretion disk scales at the jet launch point has not been detected. We report radio interferometry observations at 1.3mm wavelength of the elliptical galaxy M87 that spatially resolve the base of the jet in this source. The derived size of 5.5 ± 0.4 Schwarzschild radii is significantly smaller than the innermost edge of a retrograde accretion disk, suggesting that the M87 jet is powered by an accretion disk in a prograde orbit around a spinning black hole.

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Blobrana


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Title: Interpretation of the flares of M87 at TeV energies in the cloud-jet interaction scenario
Authors: Maxim V. Barkov, Valenti Bosch-Ramon, Felix A. Aharonian

Active galactic nuclei with misaligned jets have been recently established as a class of high-energy gamma-ray sources. M87, a nearby representative of this class, shows fast TeV variability on timescales less than one day. We present calculations performed in the framework of the scenario in which gamma-ray flares in non-blazar active galactic nuclei are produced by a red giant or a gas cloud interacting with the jet. We show that both the light curve and energy spectrum of the spectacular April 2010 flare can be reproduced by this model, assuming that a relatively massive cloud of approx 1.e29 g penetrates into the jet at few tens of Schwarzschild radii from the super-massive black hole.

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Blobrana


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HST-1
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Title: The kinematic of HST-1 in the jet of M87
Authors: M. Giroletti, K. Hada, G. Giovannini, C. Casadio, M. Beilicke, A. Cesarini, C. C. Cheung, A. Doi, H. Krawczynski, M. Kino, N. P. Lee, H. Nagai

Aims: We aim to constrain the structural variations within the HST-1 region downstream of the radio jet of M87, in general as well as in connection to the episodes of activity at very high energy (VHE).
Methods: We analysed and compared 26 VLBI observations of the M87 jet, obtained between 2006 and 2011 with the Very Long Baseline Array (VLBA) at 1.7 GHz and the European VLBI Network (EVN) at 5 GHz.
Results: HST-1 is detected at all epochs; we model-fitted its complex structure with two or more components, the two outermost of which display a significant proper motion with a superluminal velocity around ~4c. The motion of a third feature that is detected upstream is more difficult to characterise. The overall position angle of HST-1 has changed during the time of our observations from -65deg to -90deg, while the structure has moved by over 80 mas downstream. Our results on the component evolution suggest that structural changes at the upstream edge of HST-1 can be related to the VHE events.

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Blobrana


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Posts: 131433
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RE: Messier 87
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Title: The size of the jet launching region in M87
Authors: Jason Dexter, Jonathan C. McKinney, Eric Agol

Abstract: The supermassive black hole candidate at the center of M87 drives an ultra-relativistic jet visible on kiloparsec scales, and its large mass and relative proximity allow for event horizon scale imaging with very long baseline interferometry at millimeter wavelengths (mm-VLBI). Recently, relativistic magneto-hydrodynamic (MHD) simulations of black hole accretion flows have proven capable of launching magnetically-dominated jets. We construct time-dependent disc/jet models of the innermost portion of the M87 nucleus by performing relativistic radiative transfer calculations from one such simulation. We identify two types of models, jet-dominated or disc/jet, that can explain the spectral properties of M87, and use them to make predictions for current and future mm-VLBI observations. The Gaussian source size for the favored sky orientation and inclination from observations of the large-scale jet is 33-44 microarcseconds (~4-6 Schwarzschild radii) on current mm-VLBI telescopes, very similar to existing observations of Sgr A*. The black hole shadow, direct evidence of an event horizon, should be visible in future measurements using baselines between Hawaii and Mexico. Both models exhibit variability at millimeter wavelengths with factor of ~2 amplitudes on year timescales. For the low inclination of M87, the counter-jet dominates the event horizon scale millimeter wavelength emission from the jet-forming region.

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Blobrana


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Posts: 131433
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M87 black hole
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Astronomers led by Karl Gebhardt of The University of Texas at Austin have measured the most massive known black hole in our cosmic neighborhood by combining data from a giant telescope in Hawai'i and a smaller telescope in Texas.
The result is an ironclad mass of 6.6 billion suns for the black hole in the giant elliptical galaxy M87. This enormous mass is the largest ever measured for a black hole using a direct technique. Given its massive size, M87 is the best candidate for future studies to "see" a black hole for the first time, rather than relying on indirect evidence of their existence as astronomers have for decades.
The results will be presented in a news conference today at the 217th meeting of the American Astronomical Society in Seattle. Two papers detailing the results will be published soon in The Astrophysical Journal.
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Blobrana


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Posts: 131433
Date:
RE: Messier 87
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Galactic Super-volcano in Action

m87_w1.jpg
Credit      X-ray (NASA/CXC/KIPAC/N. Werner et al); Radio (NRAO/AUI/NSF/W. Cotton) Volcano image: Omar Ragnarsson

This image shows the eruption of a galactic "super-volcano" in the massive galaxy M87, as witnessed by NASA's Chandra X-ray Observatory and NSF's Very Large Array (VLA). At a distance of about 50 million light years, M87 is relatively close to Earth and lies at the centre of the Virgo cluster, which contains thousands of galaxies.
The cluster surrounding M87 is filled with hot gas glowing in X-ray light (shown in blue) that is detected by Chandra. As this gas cools, it can fall toward the galaxy's centre where it should continue to cool even faster and form new stars.

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Blobrana


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A team of astronomy researchers at Florida Institute of Technology and Rochester Institute of Technology in the United States and University of Sussex in the United Kingdom, find that the supermassive black hole (SMBH) at the centre of the most massive local galaxy (M87) is not where it was expected. Their research, conducted using the Hubble Space Telescope (HST), concludes that the SMBH in M87 is displaced from the galaxy centre. The most likely cause for this SMBH to be off centre is a previous merger between two older, less massive, SMBHs. The iconic M87 jet may have pushed the SMBH away from the galaxy centre, say researchers. The research is being presented today at the 216th meeting of the American Astronomical Society in Miami. It will also be published in The Astrophysical Journal Letters
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Blobrana


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By analysing images of M87 taken with the Hubble Space Telescope's Advanced Camera for Surveys, we have found that the supermassive black hole (SMBH) in M87 is displaced from the centre of the galaxy's light distribution by 6.8 ±0.8 pc (22 ±3 light-years). The displacement is along a position angle of 307 ±17 degrees, consistent with the direction opposite the jet. This suggests that the active SMBH in M87 does not currently reside at the galaxy's centre of mass, but is displaced in the counter-jet direction.
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Blobrana


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Title: A Displaced Supermassive Black Hole in M87
Authors: D. Batcheldor, A. Robinson, D. J. Axon, E. S. Perlman, D. Merritt

Isophotal analysis of M87, using data from the Advanced Camera for Surveys, reveals a projected displacement of 6.8 ±0.8 pc (~ 0.1 arcsec) between the nuclear point source (presumed to be the location of the supermassive black hole, SMBH) and the photo-centre of the galaxy. The displacement is along a position angle of 307 ±17 degrees and is consistent with the jet axis. This suggests the active SMBH in M87 does not currently reside at the galaxy centre of mass, but is displaced in the counter-jet direction. Possible explanations for the displacement include orbital motion of an SMBH binary, gravitational perturbations due to massive objects (e.g., globular clusters), acceleration by an asymmetric or intrinsically one-sided jet, and gravitational recoil resulting from the coalescence of an SMBH binary. The displacement direction favours the latter two mechanisms. However, jet asymmetry is only viable, at the observed accretion rate, for a jet age of >0.1 Gyr and if the galaxy restoring force is negligible. This could be the case in the low density core of M87. A moderate recoil ~1 Myr ago might explain the disturbed nature of the nuclear gas disk, could be aligned with the jet axis, and can produce the observed offset. Alternatively, the displacement could be due to residual oscillations resulting from a large recoil that occurred in the aftermath of a major merger any time in the last 10 Gyr.

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Blobrana


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Posts: 131433
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M87
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Title: Discovery of CIV Emission Filaments in M87
Authors: W.B. Sparks, J.E. Pringle, M. Donahue, R. Carswell, M. Voit, M. Cracraft, R.G. Martin

Gas at intermediate temperature between the hot X-ray emitting coronal gas in galaxies at the centers of galaxy clusters, and the much cooler optical line emitting filaments, yields information on transport processes and plausible scenarios for the relationship between X-ray cool cores and other galactic phenomena such as mergers or the onset of an active galactic nucleus. Hitherto, detection of intermediate temperature gas has proven elusive. Here, we present FUV imaging of the "low excitation" emission filaments of M87 and show strong evidence for the presence of CIV 1549 A emission which arises in gas at temperature ~10^5K co-located with Halpha+[NII] emission from cooler ~10^4K gas. We infer that the hot and cool phases are in thermal communication, and show that quantitatively the emission strength is consistent with thermal conduction, which in turn may account for many of the observed characteristics of cool core galaxy clusters.

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