Research of Jeremy Sanders

I am based at the Max Planck Institute for Extraterrestrial Physics (MPE), working in the High Energy Astrophysics Group. I was a postdoctoral researcher working in the X-ray Group at the Institute of Astronomy, University of Cambridge, UK.

My work is mainly on the topic of clusters of galaxies. Galaxy clusters are the largest objects in the universe which are held together by gravity. They consist of hundreds to thousands of galaxies (each of which contains many billions of stars), moving through a very hot diffuse gas or plasma. This gas is known as the intracluster medium (ICM) and has a temperature of 10s of millions of degrees C. The hot gas emits X-rays which we can observe from observatories orbiting the Earth such as Chandra and XMM-Newton.

Some of the interesting scientific questions I am trying to address involve the interaction of the central supermassive black holes which lie in cluster cores with the surrounding intracluster medium. The intracluster medium in the cores of galaxy clusters should be cooling soon as it is emitting a lot of energy from X-rays. The problems I am working on include, How much gas is cooling in clusters?, Do the black holes stop the cooling of the ICM?, If they do, how do they stop cooling? To answer these questions I look at the nearest, brightest galaxy clusters in detail. Here is some information on recent research.

The Perseus cluster

The Perseus cluster (pictured) is the brightest cluster of galaxies in the sky when viewed in X-rays. This makes it an ideal target to study the interaction of supermassive black holes with galaxy clusters, as you get a lot of X-ray light from a cluster to analyse.

Image of the Perseus cluster core Filtered image of Perseus showing
fluctutations/sound waves

(Left) False colour picture of the Perseus cluster, Abell 426. The colours mainly show temperature variation. The green structure around the centre of the image is actually a shadow of a galaxy which lies between us and Perseus. (Right) A filtered image of Perseus, removing the smooth variation, showing the small scale fluctuations. The image shows a number of ripple-like structures around the core of the cluster.

The bright dot at the centre of the images is the central supermassive black hole. Above and below that you can see round darker regions in the left image which are bubbles of energetic particles emitted by the black hole. These radio bubbles (you can see the bubbles in radio emission) push away the X-ray emitting gas, leaving you with holes in the image. The two similar features further from the centre are so-called fossil bubbles, which are believe to be old radio bubbles which have detached themselves from the black hole and floated outwards in the cluster. There are similar features seen in long observations.

The right image shows the small-scale variations seen in the cluster. These ripple like features correspond to density variations in the hot gas. We therefore think the are very low frequency sound waves generated by the black hole as it blows the radio bubbles. These may be some of the lowest notes in the Universe! For more details see this press release.

Astronomy picture of the day

Links to some work I have been involved with that has appeared on Astronomy Picture of the Day.

  1. 22nd August 2008, Active Galaxy NGC 1275
  2. 8th December 2005, X-rays from the Perseus cluster core
  3. 12th September 2003, A Note on the Perseus Cluster
  4. 28th March 2002, Centaurus Galaxy Cluster in X-Rays
  5. 22nd February 2001, 3C294: Distant X-Ray Galaxy Cluster
  6. 8th December 2000, Abell 1795: A Galaxy Cluster's Cooling Flow
  7. 31st October 2000, The Perseus Cluster's X-Ray Skull
  8. 15th June 2000, X-rays From The Perseus Cluster Core

Press releases and Chandra photo albums

Links to the press releases for some of the work I have been involved with

  1. Coma Cluster: Clues to the Growth of the Colossus in Coma
  2. Hubble sees magnetic monster in erupting galaxy
  3. Perseus cluster: Chandra proves black hole influence is far reaching
  4. Chandra "Hears" a Supermassive Black Hole in Perseus
  5. Chandra catches cannibal galaxy in the act
  6. Chandra Finds Most Distant X-ray Galaxy Cluster
  7. Centaurus Cluster of Galaxies: Vast Hot Gas Plume May Be A Passing Attraction
  8. Abell 1795: A Cooling Flow In Galaxy Cluster Abell 1795

Other articles in the press

  1. Booming sound waves heat up galaxy cluster (New Scientist)
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