NASA Announces Black Holes Found to be "Green"

Press Release From: NASA HQ
Posted: Monday, April 17, 2006


Astronomers using NASA's Chandra X-ray Observatory will hold a media teleconference at 1 p.m. EDT Monday, April 24, to announce a fundamental discovery about black holes.

Reporters must call the Chandra Press Office at (617) 496-7998 or email by 11 a.m. April 24 for participation information. Images and graphics supporting the briefing will be posted online at the start of the briefing at:

Audio of the event will be streamed live on the Web at:

Briefing participants:

  • Steven Allen, assistant professor, Stanford University, Palo Alto, Calif.
  • Christopher Reynolds, associate professor, University of Maryland, College Park
  • Kimberly Weaver, astrophysicist, Goddard Space Flight Center, Greenbelt, Md.

A video file about the discovery will air on NASA TV on April 24. NASA TV is carried on an MPEG-2 digital signal accessed via satellite AMC-6, at 72 degrees west longitude, transponder 17C, 4040 MHz, vertical polarization. It's available in Alaska and Hawaii on AMC-7 at 137 degrees west longitude, transponder 18C, at 4060 MHz, horizontal polarization.

For information about NASA and agency programs, visit:

Astrophysics, abstract

From: Steven Allen [view email]
Date: Fri, 24 Feb 2006 22:01:52 GMT   (564kb)
The relation between accretion rate and jet power in X-ray luminous elliptical galaxies Authors: S.W. Allen (KIPAC, Stanford), R.J.H. Dunn, A.C. Fabian (IoA, Cambridge), G.B. Taylor (UNM), C.S. Reynolds (UMD)
Comments: Submitted for publication in MNRAS (Jan 2006). 10 pages, 5 figures
Using Chandra X-ray observations of 9 nearby, X-ray luminous ellipticals with good optical velocity dispersion measurements, we show that a tight correlation exists between the Bondi accretion rates calculated from the X-ray data and estimated black hole masses, and the power emerging from these systems in relativistic jets. The jet powers, inferred from the energies and timescales required to inflate the cavities observed in the surrounding X-ray emitting gas, can be related to the accretion rates by a power law model. A significant fraction (2.4^{+1.0}_{-0.7} per cent, for P_jet=10^{43} erg/s) of the energy associated with the rest mass of material entering the accretion radius emerges in the jets. Our results have significant implications for studies of accretion, jet formation and galaxy formation. The tight correlation between P_Bondi and P_jet suggests that the Bondi formulae provide a reasonable description of the accretion process, despite the likely presence of magnetic pressure and angular momentum in the accreting gas, and that the accretion flows are approximately stable over timescales of a few million years. Our results show that the black hole engines at the hearts of large elliptical galaxies and groups feed back sufficient energy to stem cooling and star formation, leading naturally to the observed exponential cut off at the bright end of the galaxy luminosity function.
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