Abell 2597
Credit: X-ray: NASA/CXC/Michigan State Univ/G.Voit et al;
Optical: NASA/STScI & DSS; H-alpha: Carnegie Obs./Magellan/W.Baade Telescope
This galaxy cluster comes from a sample of over 200 that were studied to determine how giant black holes at their centers affect the growth and evolution of their host galaxy, as reported in our latest press release. This study revealed that an unusual form of cosmic precipitation enables a feedback loop of cooling and heating, stifling star formation in the middle of these galaxy clusters.
Abell 2597, shown here, is a galaxy cluster located about one billion light years from Earth. This image contains X-rays
from NASA's Chandra X-ray Observatory (blue), optical data from the
Hubble Space Telescope and the Digitized Sky Survey (yellow) and
emission from hydrogen atoms (red) from the Walter Baade Telescope in
Chile.
According to this new study, the regulation of the largest black hole
and their host galaxies works as follows: in some galaxies, such as NGC
2597, hot gas is able to quickly cool through radiation and energy
loss, in a process called precipitation. The clouds of cool gas that
result then fall into the central supermassive black hole, producing
jets that heat the gas and prevent further cooling.
The researchers used Chandra
data to estimate how long it should take for the gas to cool at
different distances from the black holes in the study. Using that
information, they were able to accurately predict the "weather" around
each of the black holes.
They found that the precipitation feedback loop driven by energy
produced by the black hole jets prevents the showers of cold clouds from
getting too strong. The Chandra data indicate that the regulation of
this precipitation has been going on for the last 7 billion years or
more.
While a rain of cool clouds appears to play a key role in regulating
the growth of some galaxies, the researchers have found other galaxies
where the cosmic precipitation had shut off. The intense heat in these
central galaxies, possibly from colliding with another galaxy cluster,
likely "dried up" the precipitation around the black hole.
Evidence was also found, in a few galaxy clusters, that strong bursts
of outflows from regions near the black hole may have temporarily shut
down precipitation, but the heating is not strong enough to result in
conduction. In these cases, further cooling of gas should occur and
active precipitation should resume in a few hundred million years.
A pre-print of the Nature study by Mark Voit (Michigan State
University), Megan Donahue (Michigan State), Greg Bryan (Columbia
University), and Michael McDonald (Massachusetts Institute of
Technology) is available online; the study builds on work by Voit and
Donahue that was published in the January 20th, 2015 issue of The
Astrophysical Journal Letters and is available online.
NASA's Marshall Space Flight Center in Huntsville, Alabama, manages
the Chandra program for NASA's Science Mission Directorate in
Washington. The Smithsonian Astrophysical Observatory in Cambridge,
Massachusetts, controls Chandra's science and flight operations.
Scale: Image is 2 arcmin on a side (about 600,000 light years)
Category: Groups & Clusters of Galaxies
Coordinates (J2000): RA 23h 25m 19.6s | Dec -12° 07' 27.4"
Constellation: Aquarius
Observation Date: 28 Jul 2000, 01 and 04 May 2006
Observation Time: 42 hours 7 min (1 day 18 hours 7 min).
Obs. ID: 922, 6934, 7329
Instrument: ACIS
References: Voit, G. et al, 2015, Nature (accepted); Voit, G. et al, 2015, ApJL, 799; arXiv:1409.1601
Color Code: X-ray (Blue); Optical (Yellow); H-alpha (Red)
Distance Estimate: About 1 billion light years
Source: NASA’s Chandra X-ray Observatory
