Galaxy Clusters - Perseus e Virgo Cluster
Credit: NASA/CXC/Stanford/I.Zhuravleva et al
These two Chandra images of galaxy clusters - known as Perseus and Virgo - have provided direct evidence that turbulence is helping to prevent stars from forming. These new results could answer a long-standing question about how these galaxy clusters keep their enormous reservoirs of hot gas from cooling down to form stars, as discussed in our latest press release [link to PR].
Galaxy clusters are the largest objects in the Universe held together
by gravity. They contain hundreds or thousands of individual galaxies
that are immersed in gas with temperatures of millions of degrees. This
hot gas, which is the heftiest component of the galaxy clusters aside
from dark matter, glows brightly in X-ray light.
Over time in the centers of clusters, this gas should cool enough so
that stars form at prodigious rates. This, however, is not what
astronomers have observed in many galaxy clusters.
A team of researchers have found evidence that the heat is generated
by turbulent motions, which they identified from signatures in the Chandra data. Previously, other scientists have shown the key role of supermassive black holes
in the centers of large galaxies in the middle of galaxy clusters.
These black holes pump vast quantities of energy into the volumes around
them through powerful jets of energetic particles. Chandra and other
X-ray telescopes have detected giant cavities created in the hot cluster
gas by the jets.
The latest research provides insight into just how energy can be
transferred from the cavities to the surrounding gas. The interaction of
the cavities with the gas may be generating turbulence, or chaotic
motion similar to that on a bumpy airplane ride, which then dissipates
to keep the gas hot for billions of years.
The scientists targeted Perseus and Virgo because they are both
extremely large and relatively bright, thus providing an opportunity to
see details that would be very difficult to detect in other clusters.
The evidence for turbulence can be seen most clearly in the ripple-like
structures in the Chandra image of Perseus. When combined with careful
analysis of the data with theoretical models, this new result provides
the clearest evidence to date that turbulence is the mechanism that
prevents the hot gas in these clusters from cooling.
The paper describing these results is available online.
These results appeared online in the journal Nature on October 26,
2014. The authors were Irina Zhuravleva (Stanford University), Eugene
Churazov (Max Planck Institute for Astrophysics), Alexander
Schekochinhin (University of Oxford), Steve Allen (Stanford), Patricia
Arevalo (Pontificia Universidad Catolica de Chile), Andy Fabian
(University of Cambridge), William Forman (Harvard-Smithsonian Center
for Astrophysics), Jeremy Sanders (Max Planck Institute for
Extraterrestrial Physics), Aurora Simionescu (JAXA), Rasheed Sunayev
(Max Planck Institute for Astrophysics), Alexey Vikhlinin
(Harvard-Smithsonian Center for Astrophysics), and Norbert Werner
(Stanford).
NASA's Marshall Space Flight Center in Huntsville, Alabama, manages
the Chandra program for NASA's Science Mission Directorate in
Washington, DC. The Smithsonian Astrophysical Observatory in Cambridge,
Massachusetts, controls Chandra's science and flight operations.
Fast Facts for Perseus Cluster:
Release: Date October 27, 2014
Scale: Image is 20 arcmin across (about 1.5 million light years).
Category: Groups & Clusters of Galaxies
Coordinates (J2000): RA 03h 19m 47.60s | Dec +41° 30' 37.00"
Constellation: Perseus
Observation Dates: 25 pointings between Sep 1999 and Dec 2009
Observation Time: 416 hours 32 min (17 days 8 hours 32 min)
Obs. IDs: 502, 503, 1513, 3209, 3404, 4289, 4946-4953, 6139, 6145, 6146, 11713-11716, 12025, 12033, 12036, 12037
Instrument: ACIS
Also Known As: Abell 426
References: Zhuravleva, I. et al, 2014, Nature (in press); arXiv:1410.6485
Color Code: X-ray: Purple X-ray
Distance Estimate: About 250 million light years
Fast Facts for Virgo Cluster:
Release Date: October 27, 2014
Scale: Image is 22 arcmin across (about 320,000 light years).
Category: Groups & Clusters of Galaxies
Coordinates (J2000): RA 12h 30m 49.40s | Dec +12° 23' 28.00"
Constellation: Virgo
Observation Dates: 2 pointings in Jul 2002, and 7 between Jan and Nov 2005
Observation Time: 159 hours (6 days 15 hours)
Obs. IDs: 2707, 3717, 5826-5828, 6186, 7210-7212
Instrument: ACIS
References: Zhuravleva, I. et al, 2014, Nature (in press); arXiv:1410.6485
Color Code: X-ray: Purple
Distance Estimate: About 55 million light years
Source: NASA’s Chandra X-ray Observatory
