Chandra, Spitzer and VLT Find Large Galaxy Cluster From Very Early Universe

A composite image reveals a thing of utter beauty! The Chandra X-Ray Telescope, the Spitzer and the Very Large Telescope (VLT) have stitched together an image of a large Galaxy cluster that dates back right to the Early Universe, when galaxy formation was just starting to happen. The composite image is given below.

Image 1: The El Gordo Galaxy - the composite image. Blue represents the X-Rays, while the red and orange represent infrared and optical. (Courtesy: NASA/CXC/JPL/ESO)

Enter the Fat Man

Named El Gordo, Spanish for ‘fat man’, this structure appears bloated in X-Ray and infrared images. The most interesting structure is the core, which is extremely bright in X-Rays. Chandra has mapped the central part and has come up with two distinct tail-like structures, indicating that two previously large structures have merged to form the El Gordo.

The object is located in the constellation Pheonix, but this is a very difficult constellation to spot, being both very faint and extremely southerly. El Gordo is located 7.17 billion light years from Earth, which is way further than the well-known Bullet Cluster that lies about 4 billion light years away.

Stitching together to form an image

The following two images are the ones obtained by Spitzer and VLT (Image 2) and by Chandra (Image 3).

Image 2: The El Gordo in Optical and Infrared frequencies. The data has been obtained from Spitzer (IR) and VLT (Optical). (Courtesy: Optical - ESO/VLT; IR - NASA/JPL)
Image 3: The El Gordo in X-Ray. Data obtained by the Chandra X-Ray Telescope. Notice the two distinct tails and the very X-Ray hot core. (Courtesy: NASA/CXC/Rutgers/J.Hughes et al)

The composite image (Image 1) is made by combining data from the Chandra X-Ray Telescope, which gives the X-Ray data, the Spitzer telescope, which provides the infra-red (i.e. thermal) data and the Very Large Telescope (VLT), which maps the optical frequencies. The infrared and X-Rays are false coloured, with the X-Rays being represented by blue and the infrared by orange and red. The El Gordo’s central region is blue in the X-Ray, indicating that some violent X-Ray generating processes are afoot.

Dark Matter ripping out hot gases

El Gordo also shows signatures of gas which have been dispersed by dark matter, not unlike the Bullet cluster. Dark matter has not been stopped by collision, due to feeble interactions with the mass outside, but the hot gas has been. Dark matter has then ripped apart the hot gas and this forms the halo, which is incandescent in both Optical and X-ray frequencies, and presumably even in Radio. In fact, the X-Ray emitting hot gas, forming the halo-like structure around El Gordo, account for more than 90% of the visible mass of the galaxy cluster as compared to just about 1-3% contribution from actual stars. The number of stars is, however, massive – there are about 4 quadrillion (a million billion) of them!

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Debjyoti Bardhan

Is a science geek, currently pursuing some sort of a degree (called a PhD) in Physics at TIFR, Mumbai. An enthusiastic but useless amateur photographer, his most favourite activity is simply lazing around. He is interested in all things interesting and scientific.