A spectacular cosmic collision between the spiral galaxies NGC 2207 and IC 2163 has been caught in a composite image generated by NASA’s Chandra X-ray Observatory, Spitzer and Hubble Space Telescopes.
X-ray data from Chandra have revealed that NGC 2207 (left) and IC 2163, currently in the process of colliding with one another, have produced one of the most bountiful collections of super bright X-ray lights called ultraluminous X-ray sources. Image credit: X-ray – NASA / CXC / SAO / S.Mineo et al; optical – NASA / STScI; infrared: NASA / JPL-Caltech.
This pair of spiral galaxies is located in the constellation of Canis Major, about 130 million-light years away.
The larger and more massive galaxy is cataloged as NGC 2207, and the smaller one is IC 2163.
Strong tidal forces from the former have distorted the shape of the latter, flinging out stars and gas into long streamers stretching out a hundred thousand light-years toward the right-hand edge of the image.
Computer simulations indicate that IC 2163 is swinging past NGC 2207 in a counterclockwise direction, having made its closest approach 40 million years ago.
However, IC 2163 does not have sufficient energy to escape from the gravitational pull of NGC 2207, and is destined to be pulled back and swing past the larger galaxy again in the future.
The NGC 2207 – IC 2163 pair has hosted three supernova explosions in the past 15 years and has produced one of the most bountiful collections of special objects, known as ultraluminous X-ray sources (ULXs).
A new composite image of this galaxy pair contains Chandra data in pink, Hubble optical light data in red, green, and blue, and infrared data from Spitzer in red. It contains about five times more observing time than previous efforts to study ULXs in the pair.
Writing in the Astrophysical Journal (arXiv.org preprint), a team of astronomers says there is a total of 28 ULXs between the galaxies, seven of which were not detected previously because of X-ray variability.
Colliding galaxies like NGC 2207 – IC 2163 are well known to contain intense star formation. Shock waves form during the collision, leading to the collapse of clouds of gas and the formation of star clusters.
The stars associated with the ULXs are very young and may only be about 10 million years old.
Moreover, analysis shows that stars of various masses are forming in the pair at a rate equivalent to form 24 stars the mass of our Sun per year.
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S. Mineo et al. 2014. A Comprehensive X-Ray and Multiwavelength Study of the Colliding Galaxy Pair NGC 2207/IC 2163. ApJ 797, 91; doi: 10.1088/0004-637X/797/2/91
