Groups & Clusters of Galaxies

Astronomers have used NASA's Chandra X-ray Observatory to show that multiple eruptions from a supermassive black hole over 50 million years have rearranged the cosmic landscape at the center of a group of galaxies.

Scientists discovered this history of black hole eruptions by studying NGC 5813, a group of galaxies about 105 million light years from Earth. These Chandra observations are the longest ever obtained of a galaxy group, lasting for just over a week. The Chandra data are shown in this new composite image where the X-rays from Chandra (purple) have been combined with visible light data (red, green and blue).

This panel of images represents a study of 72 colliding galaxy clusters conducted by a team of astronomers using NASA's Chandra X-ray Observatory and Hubble Space Telescope. The research sets new limits on how dark matter - the mysterious substance that makes up most of the matter in the Universe - interacts with itself, as reported in the press release. This information could help scientists narrow down the possibilities of what dark matter may be.

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.

A newly discovered galaxy cluster is the most massive one ever detected with an age of 800 million years or younger. Using data from NASA's Chandra X-ray Observatory, astronomers have accurately determined the mass and other properties of this cluster, as described in our latest press release. This is an important step in understanding how galaxy clusters, the largest structures in the Universe held together by gravity, have evolved over time.

Irina Zhuravleva

We are pleased to welcome Irina Zhuravleva as a guest blogger today. Irina is the first author of a new paper describing a crucial role of gas turbulence in interaction between supermassive black holes and hot gas in galaxy clusters, the subject of our latest press release. Irina studied theoretical astrophysics in the department of mathematics and mechanics at Saint Petersburg State University in Russia, followed by a PhD in astrophysics at Max Planck Institute for Astrophysics in Germany. After that she moved to San Francisco area as a postdoctoral researcher at KIPAC, Stanford University.

Chaotic, turbulent flows are commonly encountered in everyday life: swirling eddies of milk poured into coffee, flickering flames of a campfire, external flows over cars and ships, white froth from breaking waves in the ocean, quaint patterns of clouds in the sky and pyroclastic flow in a volcanic eruption.

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.

We are delighted to welcome Esra Bulbul as a guest blogger. Esra led the new study reporting evidence for a mysterious X-ray signal in galaxy clusters, leading to our latest press release. She earned her master’s degree in physics from the Middle East Technical University in the capital city, Ankara, in Turkey in 2006. Four years later she graduated with a PhD in physics from the University of Alabama in Huntsville / NASA Marshall Space Flight Center. After receiving her Ph.D. she moved to the Harvard-Smithsonian Center for Astrophysics as a Smithsonian Astrophysical Fellow working jointly at the NASA Goddard Space Flight Center as a visiting scientist. She is now back at the Harvard-Smithsonian Center for Astrophysics and enjoys living in the greater Boston area.

When I started my first postdoc at the Harvard-Smithsonian Center for Astrophysics, I already knew that one alternative way to improve the sensitivity of current instruments like Chandra and XMM-Newton is to “stack” large numbers of observations of galaxy clusters, meaning that we layer one observation on top of another.

The great advantage of stacking observations is not only an increased signal-to-noise ratio (that is, the amount of useful signal compared to background noise), but also the diminished effects of detector and background features. The X-ray background emission and instrumental noise are the main obstacles in the analysis of faint objects, such as galaxy clusters.

A new study of the Perseus galaxy cluster, shown in this image, using NASA's Chandra X-ray Observatory and 73 other clusters with ESA's XMM-Newton has revealed a mysterious X-ray signal in the data. This signal is represented in the circled data points in the inset, which is a plot of X-ray intensity as a function of X-ray energy. The signal is also seen in over 70 other galaxy clusters using XMM-Newton. This unidentified X-ray emission line - that is, a spike of intensity at a very specific energy, in this case centered on about 3.56 kiloelectron volts (keV) - requires further investigation to confirm both the signal's existence and nature as described in the latest Chandra press release.

This is a composite image of X-rays from Chandra and optical data from Hubble of the galaxy cluster ACT-CL J0102-4915, located about 7 billion light years from Earth. This cluster has been nicknamed "El Gordo" (or, "the fat one" in Spanish) because of its gigantic mass.