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Post Info TOPIC: Messier 84


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Hubble Sees a Fascinating Core

This elliptical galaxy was discovered in March 1781 and lies about 60 million light-years away from Earth in the constellation of Virgo (The Virgin). The galaxy is part of the very heavily populated center of the Virgo Cluster, a cluster which consists of more than 1,000 galaxies.
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Messier 84 (also M84, NGC 4374 and PGC 40455) is a magnitude +10.1 elliptical or lenticular galaxy located 60 3 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 17th April 1784.

Right Ascension 12h 25m 03.7s, Declination +12 53 13"

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Title: The Supermassive Black Hole in M84 Revisited
Authors: Jonelle L. Walsh (1), Aaron J. Barth (1), Marc Sarzi (2) ((1) University of California, Irvine, (2) University of Hertfordshire)

The mass of the central black hole in the giant elliptical galaxy M84 has previously been measured by two groups using the same observations of emission-line gas with the Space Telescope Imaging Spectrograph (STIS) on the Hubble Space Telescope, giving strongly discrepant results: Bower et al. (1998) found M_BH = (1.5^{+1.1}_{-0.6}) x 10^9 M_sun, while Maciejewski & Binney (2001) estimated M_BH = 4 x 10^8 M_sun. In order to resolve this discrepancy, we have performed new measurements of the gas kinematics in M84 from the same archival data, and carried out comprehensive gas-dynamical modelling for the emission-line disk within ~70 pc from the nucleus. In comparison with the two previous studies of M84, our analysis includes a more complete treatment of the propagation of emission-line profiles through the telescope and STIS optics, as well as inclusion of the effects of an intrinsic velocity dispersion in the emission-line disk. We find that an intrinsic velocity dispersion is needed in order to match the observed line widths, and we calculate gas-dynamical models both with and without a correction for asymmetric drift. Including the effect of asymmetric drift improves the model fit to the observed velocity field. Our best-fitting model with asymmetric drift gives M_BH = (8.5^{+0.9}_{-0.8}) x 10^8 M_sun (68% confidence). This is a factor of ~2 smaller than the mass often adopted in studies of the M_BH - sigma and M_BH - L relationships. Our result provides a firmer basis for the inclusion of M84 in the correlations between black hole mass and host galaxy properties.

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Messier 84
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Title: In-depth Chandra study of the AGN feedback in Virgo elliptical galaxy M84
Authors: A. Finoguenov, M. Ruszkowski, C. Jones, M. Brueggen, A. Vikhlinin, E. Mandel

Using deep Chandra observations of M84 we study the energetics of the interaction between the black hole and the interstellar medium of this early-type galaxy. We perform a detailed two dimensional reconstruction of the properties of the X-ray emitting gas using a constrained Voronoi tessellation method, identifying the mean trends and carrying out the fluctuation analysis of the thermodynamical properties of the hot ISM. In addition to the PV work associated with the bubble expansion, we identify and measure the wave energy associated with the mildly supersonic bubble expansion. We show that, depending on the age of the cavity and the associated wave, the waves can have a substantial contribution to the total energy release from the AGN. The energy dissipated in the waves tends to be concentrated near the centre of M84 and in the direction perpendicular to the bubble outflow, possibly due to the interference of the waves generated by the expansion of northern and southern bubbles. We also find direct evidence for the escape of radio plasma from the ISM of the host galaxy into the intergalactic medium.

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