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Post Info TOPIC: Messier 87
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RE: Messier 87
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Giant Galaxy is Still Growing

New observations with ESO's Very Large Telescope have revealed that the giant elliptical galaxy Messier 87 has swallowed an entire medium-sized galaxy over the last billion years. For the first time a team of astronomers has been able to track the motions of 300 glowing planetary nebulae to find clear evidence of this event and also found evidence of excess light coming from the remains of the totally disrupted victim.
Astronomers expect that galaxies grow by swallowing smaller galaxies. But the evidence is usually not easy to see - just as the remains of the water thrown from a glass into a pond will quickly merge with the pond water, the stars in the infalling galaxy merge in with the very similar stars of the bigger galaxy leaving no trace.
But now a team of astronomers led by PhD student Alessia Longobardi at the Max-Planck-Institut für extraterrestrische Physik, Garching, Germany has applied a clever observational trick to clearly show that the nearby giant elliptical galaxy Messier 87 merged with a smaller spiral galaxy in the last billion years.
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Blobrana


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Title: Understanding the light curves of the HST-1 knot in M87 with internal relativistic shock waves along its jet
Author: Y. Coronado, O. López-Corona, S. Mendoza

Knots or blobs observed in astrophysical jets are commonly interpreted as shock waves moving along them. Long time observations of the HST-1 knot inside the jet of the galaxy M87 have produced detailed multi-wavelength light curves. In this article, we model these light curves using the semi-analytical approach developed by Mendoza et al. (2009). This model was developed to account for the light curves of working surfaces moving along relativistic jets. These working surfaces are generated by periodic oscillations of the injected flow velocity and mass ejection rates at the base of the jet. Using genetic algorithms to fit the parameters of the model, we are able to explain the outbursts observed in the light curves of the HST-1 knot with an accuracy greater than a 2 sigma statistical confidence level.

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Blobrana


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Title: The Event Horizon of M87
Author: Avery E. Broderick (1,2), Ramesh Narayan (3), John Kormendy (4,5,6), Eric S. Perlman (7), Marcia J. Rieke (8), Sheperd S. Doeleman (3,9) ((1) Perimeter Institute for Theoretical Physics, (2) University of Waterloo, (3) Harvard-Smithsonian Center for Astrophysics, (4) University of Texas at Austin, (5) Max-Planck-Institut fur Extraterrestrische Physik, (6) Universitats-Sternwarte, (7) Department of Physics and Space Sciences, (8) Steward Observatory, (9) MIT Haystack Observatory)

The 6 billion solar mass supermassive black hole at the center of the giant elliptical galaxy M87 powers a relativistic jet. Observations at millimetre wavelengths with the Event Horizon Telescope have localised the emission from the base of this jet to angular scales comparable to the putative black hole horizon. The jet might be powered directly by an accretion disk or by electromagnetic extraction of the rotational energy of the black hole. However, even the latter mechanism requires a confining thick accretion disk to maintain the required magnetic flux near the black hole. Therefore, regardless of the jet mechanism, the observed jet power in M87 implies a certain minimum mass accretion rate. If the central compact object in M87 were not a black hole but had a surface, this accretion would result in considerable thermal near-infrared and optical emission from the surface. Current flux limits on the nucleus of M87 strongly constrain any such surface emission. This rules out the presence of a surface and thereby provides indirect evidence for an event horizon.

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Blobrana


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HVGC-1
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Entire Star Cluster Thrown Out of its Galaxy

The galaxy known as M87 has a fastball that would be the envy of any baseball pitcher. It has thrown an entire star cluster toward us at more than two million miles per hour. The newly discovered cluster, which astronomers named HVGC-1, is now on a fast journey to nowhere. Its fate: to drift through the void between the galaxies for all time.
"Astronomers have found runaway stars before, but this is the first time we've found a runaway star cluster," says Nelson Caldwell of the Harvard-Smithsonian Center for Astrophysics. Caldwell is lead author on the study, which will be published in The Astrophysical Journal Letters and is available online.
The "HVGC" in HVGC-1 stands for hypervelocity globular cluster. Globular clusters are relics of the early universe. These groupings usually contain thousands of stars crammed into a ball a few dozen light-years across. The Milky Way galaxy is home to about 150 globular clusters. The giant elliptical galaxy M87, in contrast, holds thousands.
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Blobrana


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NGC 4486
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Messier 87 (also M87, Virgo A, NGC 4486, MCG 2-32-105 and PGC 41361) is a magnitude +9.6 elliptical galaxy located 53.5 ±1.63 million light-years away in the constellation Virgo.

The galaxy was discovered by French astronomer Charles Messier using a 10 cm (4 inch) refracting telescope on the 18th March 1781.
The galaxy was independently discovered by William Herschel on the 8th April 1784.

Right Ascension 12h 30m 49.4s, Declination +12° 23 28.0"

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Blobrana


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Messier 87
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Title: Greenland Telescope (GLT) Project: "A Direct Confirmation of Black Hole with Submillimeter VLBI"
Author: M. Nakamura, J.-C. Algaba, K. Asada, B. Chen, M.-T. Chen, J. Han, P.H.P. Ho, S.-N. Hsieh, T. Huang, M. Inoue, P. Koch, C.-Y. Kuo, P. Martin-Cocher, S. Matsushíta, Z. Meyer-Zhao, H. Nishioka, G. Nystom, N. Pradel, H.-Y. Pu, P. Raffin, H.-Y. Shen, C.-Y. Tseng, the Greenland Telescope Project Team

The GLT project is deploying a new submillimeter (submm) VLBI station in Greenland. Our primary scientific goal is to image a shadow of the supermassive black hole (SMBH) of six billion solar masses in M87 at the center of the Virgo cluster of galaxies. The expected SMBH shadow size of 40-50 µ as requires superbly high angular resolution, suggesting that the submm VLBI would be the only way to obtain the shadow image. The Summit station in Greenland enables us to establish baselines longer than 9,000 km with ALMA in Chile and SMA in Hawaii as well as providing a unique u--v coverage for imaging M87. Our VLBI network will achieve a superior angular resolution of about 20 µ as at 350 GHz, corresponding to ~2.5 times of the Schwarzschild radius of the supermassive black hole in M87. We have been monitoring the atmospheric opacity at 230 GHz since August. 2011; we have confirmed the value on site during the winter season is comparable to the ALMA site thanks to high altitude of 3,200 m and low temperature of -50° C. We will report current status and future plan of the GLT project towards our expected first light on 2015--2016.

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Blobrana


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Hubble Takes Movies of Space Slinky

More than thirteen years of observations from NASA's Hubble Space Telescope have allowed astronomers to assemble time-lapse movies of a 5,000-light-year-long jet of superheated gas being ejected from a supermassive black hole in the center of the giant elliptical galaxy M87.
The movies promise to give astronomers a better understanding of how active black holes shape galaxy evolution. While matter drawn completely into a black hole cannot escape its enormous gravitational pull, most infalling material drawn toward it first joins an orbiting region known as an accretion disk encircling the black hole. Magnetic fields surrounding the black hole are thought to entrain some of this ionized gas, ejecting it as very high-velocity jets.
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Blobrana


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Searching for the True Colours of M87's Globular Clusters

Do all globular clusters within a galaxy share a common history? Multiple histories could indicate that different processes drive a galaxy's fundamental development at different times. Juan Carlos Forte (Consejo Nacional de Investigaciones Científicas y Técnicas, Argentina) and colleagues used the Gemini Multi-Object Spectrograph (GMOS) to study over 500 globular clusters in the galaxy M87. Their observations indeed point to such complexity, revealing multiple episodes of star formation.
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Title: Multicolour-metallicity Relations from Globular Clusters in NGC 4486 (M87)
Authors: Juan C. Forte, Favio R. Faifer, E. Irene Vega, Lilia P. Bassino, Analia V. Smith Castelli, Sergio A. Cellone, Douglas Geisler

We present Gemini griz photometry for 521 globular cluster (GC) candidates in a 5.5 x 5.5 arcmin field centered 3.8 arcmin to the south and 0.9 arcmin to the west of the center of the giant elliptical galaxy NGC 4486. All these objects have previously published (C-T1) photometry. We also present new (C-T1) photometry for 338 globulars, within 1.7 arcmin in galactocentric radius, which have (g-z) colours in the photometric system adopted by the Virgo Cluster Survey of the Advanced Camera for Surveys of the Hubble Space Telescope. These photometric data are used to define a self-consistent multicolour grid (avoiding polynomial fits) and preliminary calibrated in terms of two chemical abundance scales. The resulting multicolour colour-chemical abundance relations are used to test GC chemical abundance distributions. This is accomplished by modelling the ten GC colour histograms that can be defined in terms of the Cgriz bands. Our results suggest that the best fit to the GC observed colour histograms is consistent with a genuinely bimodal chemical abundance distribution NGC(Z). On the other side, each (blue and red) GC subpopulation follows a distinct colour-colour relation.

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Title: VERITAS Observations of M 87 in 2011/2012
Authors: M.Beilicke, the VERITAS Collaboration

The giant radio galaxy M 87 is located at a distance of 16.7 Mpc and harbours a super-massive black hole (6 billion solar masses) in its center. M 87 is one of just three radio galaxies known to emit TeV gamma-rays. The structure of its relativistic plasma jet, which is not pointing towards our line of sight, is spatially resolved in X-ray (Chandra), optical and radio (VLA/VLBA) observations. The mechanism and location of the TeV emitting region is one of the least understood aspects of AGN. In spring 2008 and 2010, the three TeV observatories VERITAS, MAGIC and H.E.S.S. detected two major TeV flares in coordinated observations. Simultaneous high-resolution observations at other wavelengths - radio (2008) and X-rays (2008/2010) - gave evidence that one of the TeV flares was related to an event in the core region; however, no common/repeated patterns could be identified so far. VERITAS continued to monitor M 87 in 2011/2012. The results of these observations are presented.

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