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3C186: Precocious Galaxy Cluster Identified by Chandra

  • A new Chandra observation of 3C186 reveals a very distant galaxy cluster with a quasar and a "cooling core" at its center.

  • Cooling cores are regions bright in X-ray emission where gas is cooling.

  • In 3C186, the temperature drops from about 80 million degrees on the outskirts to 30 million degrees in its core.

  • Finding a system like this at such a great distance – 8 billion light years – is unusual and could provide insight into the triggering of quasars and the growth of galaxy clusters.

NASA's Chandra X-ray Observatory has observed an unusual galaxy cluster that contains a bright core of relatively cool gas surrounding a quasar called 3C 186. This is the most distant such object yet observed, and could provide insight into the triggering of quasars and the growth of galaxy clusters.

This composite image of the cluster surrounding 3C 186 includes a new, deep image from Chandra (blue) showing emission from gas surrounding the point-like quasar near the center of the cluster. Chandra X-ray spectra show that the temperature of the gas drops from 80 million degrees on the outskirts of the cluster down to 30 million in the core. This drop in temperature occurs because intense X-ray emission from the gas cools it. Optical data from the Gemini telescope in yellow show the stars and galaxies in the field of view.

What makes this particular galaxy cluster and its strong cooling core interesting is its age. 3C 186 is about 8 billion light years away from Earth, making it the most distant known galaxy cluster to contain a prominent cooling core. Because of its large distance the cluster is being seen when the Universe is relatively young, at less than half its current age.

Previous observations have revealed large numbers of clusters with strong cooling cores at smaller distances from the Earth, less than about 6 billion light years. Far fewer, however, have been found at larger distances between 6 and 8 billion light years. Considering its young age this "precocious" galaxy cluster around 3C 186 appears to be surprisingly well formed.

One explanation why fewer cooling cores are seen at larger distances is that these younger clusters experience higher rates of merging with other clusters or galaxies. These mergers would destroy the cooling cores. When coupled with the fact that it takes cooling cores a long time to form, this would make them rare in the earlier stages of the Universe.

Since this cluster was only found serendipitously through a Chandra survey of a small sample of radio sources, it is possible that many more similar objects exist at large distances. If these are discovered, it may revise our understanding of how galaxy clusters developed during this period of the Universe's history.

This galaxy cluster is also the most distant ever seen to contain a quasar. Only one other galaxy cluster containing a bright quasar has had a detailed study of its X-ray emitting gas, and this is located much closer to the Earth than 3C 186. In principle, the cooling gas near 3C 186 can provide enough fuel to support the growth of the supermassive black hole, the power source for the quasar.

This object also provides an interesting chance to study the effects of a quasar within a galaxy cluster environment. The energy generated by the black hole can be released into the cluster not just via mechanical power in a jet, but also by radiation from the bright quasar. This might result in a powerful wind that heats the surrounding gas and prevents further cooling.

The cluster is likely to be an ancestor of well-known nearby clusters such as Perseus and MS 0735.6+7421, where jets powered by the central black hole are boring out cavities in the cluster gas. It is much more distant and younger than these other two clusters and the radio source associated with 3C 186 is smaller and younger than in Perseus and MS 0735.6+7421.

The paper describing these results is published in the October 10th issue of the Astrophysical Journal. The list of authors is Aneta Siemiginowska, Douglas Burke and Thomas Aldcroft from the Harvard Smithsonian Center for Astrophysics, Diana Worrall from the University of Bristol, UK, Steve Allen from the Kavli Institute for Particle Astrophysics and Cosmology at Stanford University, Jill Bechtold from the University of Arizona, and Tracy Clarke and Teddy Cheung from the Naval Research Laboratory.

Fast Facts for 3C186:
Credit  X-ray: NASA/CXC/SAO/A.Siemiginowska et al, Optical: AURA/Gemini Obs.
Release Date  October 26, 2010
Scale  Image is 4.6 by 3.4 arcmin (10.7 by 7.9 million light years).
Category  Groups & Clusters of Galaxies
Coordinates (J2000)  RA 07h 44m 17.4s | Dec +37° 53´ 17.1"
Constellation  Lynx
Observation Date  4 pointings between Dec 3-8, 2007
Observation Time  55 hours (2 days 7 hours 33 min)
Obs. ID  9407-9408, 9774-9775
Instrument  ACIS
References Siemiginowska, A, et al, 2010, ApJ 722:102-111
Color Code  X-ray (Blue), Optical (Red, Green)
Distance Estimate  About 8 billion light years
distance arrow
Visitor Comments (7)

It truly is a wondrous view, and an awesome insight! But what truly amazes me is the fact that what we/or I are actually looking at is the past. So in a small way we have found a way to travel back in time!!! Am I just an idiot?

Posted by Christopher B. Marrero on Thursday, 10.13.11 @ 05:41am

My congratulations to Riccardo Giacconi. Complimenti.

Posted by Pietro C on Thursday, 11.18.10 @ 14:56pm

Thanks i like Albert Einstein interesting study the universe's history. Excellent page.

Posted by marlenecpena on Friday, 11.12.10 @ 22:29pm

Greatly appreciate your efforts in de-mystifying such complex and distant objects for us - the common man. Thank you

Posted by AK Sharma on Tuesday, 11.2.10 @ 00:59am

Amazing View and a very good work done by NASA.
I really love your great work.

Posted by zahid on Wednesday, 10.27.10 @ 02:59am

Could you briefly explain how a "cool core cluster" forms or provide a link to a non-technical explanation? perhaps, I do not understand how intense X-ray emissions cool a collection of gas.

Posted by Navneeth on Wednesday, 10.27.10 @ 02:42am

That is one powerful Quasar. A most interesting article and photo. Thanks
This makes me want to find some books on the subject of Quasars.
Marvin L. S.

Posted by Marvin on Tuesday, 10.26.10 @ 20:36pm

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