Groups & Clusters of Galaxies

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.

The spiral galaxy ESO 137-001 looks like a dandelion caught in a breeze in this new composite image from the Hubble Space Telescope and the Chandra X-ray Observatory.

The galaxy is zooming toward the upper right of this image, in between other galaxies in the Norma cluster located over 200 million light-years away. The road is harsh: intergalactic gas in the Norma cluster is sparse, but so hot at 180 million degrees Fahrenheit that it glows in X-rays detected by Chandra (blue).

Astronomers have used NASA's Chandra X-ray Observatory and a suite of other telescopes to reveal one of the most powerful black holes known. The black hole has created enormous structures in the hot gas surrounding it and prevented trillions of stars from forming.

A team of astronomers has discovered enormous arms of hot gas in the Coma cluster of galaxies by using NASA's Chandra X-ray Observatory and ESA's XMM-Newton. These features, which span at least half a million light years, provide insight into how the Coma cluster has grown through mergers of smaller groups and clusters of galaxies to become one of the largest structures in the Universe held together by gravity.

A new composite image, with Chandra data in pink and optical data from the Sloan Digital Sky Survey appearing in white and blue, features these spectacular arms. In this image, the Chandra data have been processed so extra detail can be seen.

We are very pleased to welcome a guest blogger, Julie Hlavacek-Larrondo, who led the work described in our latest press release. Julie was raised in Montreal, Canada, and in 2007 completed a Bachelor’s degree in physics at the University of Montreal. Julie then obtained a Master’s degree in astrophysics. In 2012, she completed a PhD at the University of Cambridge. She is currently an Einstein Fellow at Stanford University.

It was during my Master degree at the University of Montreal that I realized just how fascinating black holes are.

I remember stumbling upon a press release from Chandra in 2007. The Chandra space telescope revealed an image of a jet, powered by a supermassive black hole, blasting through its neighboring galaxy. What's so fascinating? Supermassive black holes are tiny objects, about a billion times smaller than the galaxy it resides in, yet, it can create jets that extend well beyond the size of the galaxy! How can something so small be so powerful?

The black hole at the center of this galaxy is part of a survey of 18 of the biggest black holes in the universe. This large elliptical galaxy is in the center of the galaxy cluster PKS 0745-19, which is located about 1.3 billion light years from Earth. X-ray data from NASA's Chandra X-ray Observatory are shown in purple and optical data from the Hubble Space Telescope are in yellow.