miércoles, 13 de junio de 2012

Astronomy: Galaxies NGC 4342, NGC 4291

Hi My Friends: A VUELO DE UN QUINDE EL BLOG., New results based on the two objects shown here are challenging the prevailing ideas as to how supermassive black holes grow in the centers of galaxies. NGC 4342 and NGC 4291, the two galaxies in the study, are nearby in cosmic terms at distances of 75 million and 85 million light years respectively. In these composite images, X-rays from NASA's Chandra X-ray Observatory are colored blue, while infrared data from the 2MASS project are seen in red.
 NGC 4342 and NGC 4291:
Black Hole Growth Found to be Out of Synch
 http://chandra.harvard.edu/photo/2012/ngc4342/

  • Two black holes are challenging the prevailing idea of how giant black holes grow in the cores of galaxies.

  • These black holes are found in the centers of two relatively nearby galaxies: NGC 4342 and NGC 4291.

  • New Chandra data suggest that the growth of these black holes is tied to the envelopes of dark matter around the galaxies, not their bulges.

New results based on the two objects shown here are challenging the prevailing ideas as to how supermassive black holes grow in the centers of galaxies. NGC 4342 and NGC 4291, the two galaxies in the study, are nearby in cosmic terms at distances of 75 million and 85 million light years respectively. In these composite images, X-rays from NASA's Chandra X-ray Observatory are colored blue, while infrared data from the 2MASS project are seen in red.
Astronomers had known from previous observations that these galaxies host black holes with unusually large masses compared to the mass contained in the central bulge of stars. To study the dark matter envelopes contained in each galaxy, Chandra was used to examine their hot gas content, which was found to be widespread in both objects.
By analyzing the distribution of the hot gas, researchers were able to test whether the galaxies had "lost weight" through stars being pulled away during a tidal encounter with another galaxy. Estimates of the pressure of the hot gas, which must balance the gravitational pull of all the matter in the galaxy, showed that massive envelopes of dark matter must exist around each galaxy. Since this tidal stripping would have severely depleted the dark matter, which is more loosely tied to the galaxies than the stars, this process is unlikely to have occurred in either galaxy.
The new results using NGC 4342 and NGC 4291 challenge the long-held idea that black holes at the centers of galaxies always grow in tandem with the bulges of stars that surround them. Rather this study suggests that the two supermassive black holes and their evolution are tied more closely to the amount and distribution of dark matter in each galaxy. In this picture the weights of the black hole and the dark matter envelope in these two galaxies are "normal" and the galaxies are underweight because they formed unusually slowly.
Fast Facts for NGC 4342:
Credit  X-ray: NASA/CXC/SAO/A.Bogdan et al; Infrared: 2MASS/UMass/IPAC-Caltech/NASA/NSF
Scale  6 arcmin across.
Category  Black Holes
Coordinates (J2000)  RA 12h 23m 39.02s | Dec +07° 03' 14.17"
Constellation  Virgo
Observation Dates  11 Feb 2005 and 17 Feb 2011
Observation Time  31 hours 15 min (1 day 7 hours 15 min)
Obs. IDs  4687, 12955
Color Code  X-ray (Blue); Infrared (Red)
Instrument  ACIS
References Bogdan, A et al. 2012, ApJ (accepted); arXiv:1203.1641
Distance Estimate  About 75 million light years
Release Date  June 11, 2012
Fast Facts for NGC 4291:
Credit  X-ray: NASA/CXC/SAO/A.Bogdan et al; Infrared: 2MASS/UMass/IPAC-Caltech/NASA/NSF
Scale  8.4 arcmin across.
Category  Black Holes
Coordinates (J2000)  RA 12h 20m 17.70s | Dec +75° 22' 15.47"
Constellation  Draco
Observation Dates  11 Dec 2010
Observation Time  8 hours 22 min
Obs. IDs  11778
Color Code  X-ray (Blue); Infrared (Red)
Instrument  ACIS
References Bogdan, A et al. 2012, ApJ (accepted); arXiv:1203.1641
Distance Estimate  About 85 million light years
Release Date  June 11, 2012


Astronomers had known from previous observations that these galaxies host black holes with unusually large masses compared to the mass contained in the central bulge of stars. To study the dark matter envelopes contained in each galaxy, Chandra was used to examine their hot gas content, which was found to be widespread in both objects.

By analyzing the distribution of the hot gas, researchers were able to test whether the galaxies had "lost weight" through stars being pulled away during a tidal encounter with another galaxy. Estimates of the pressure of the hot gas, which must balance the gravitational pull of all the matter in the galaxy, showed that massive envelopes of dark matter must exist around each galaxy. Since this tidal stripping would have severely depleted the dark matter, which is more loosely tied to the galaxies than the stars, this process is unlikely to have occurred in either galaxy.

The new results using NGC 4342 and NGC 4291 challenge the long-held idea that black holes at the centers of galaxies always grow in tandem with the bulges of stars that surround them. Rather this study suggests that the two supermassive black holes and their evolution are tied more closely to the amount and distribution of dark matter in each galaxy. In this picture the weights of the black hole and the dark matter envelope in these two galaxies are "normal" and the galaxies are underweight because they formed unusually slowly.

Credits: X-ray: NASA/CXC/SAO/A.Bogdan et al; Infrared: 2MASS/UMass/IPAC-Caltech/NASA/NSF

› Read more/access all images
› Chandra's Flickr photoset
 NASA
 Guillermo GOnzalo Sánchez Achutegui
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