FromQuarkstoQuasars

NGC 1232 and the Cosmic Pileup that Birthed a Multimillion Degree Cloud

Jaime TrosperFebruary 9th 2014
Image Credit: X-ray: NASA/CXC/Huntingdon Institute for X-ray Astronomy/G. Garmire; Optical: ESO/VLT
Image Credit: X-ray: NASA/CXC/Huntingdon Institute for X-ray Astronomy/G. Garmire; Optical: ESO/VLT

Recently, the Chandra X-ray Observatory detected a huge cloud of multimillion-degree gas located in a galaxy more than 60 million light-years from Earth. In typical celestial fashion, the cloud was spawned after a collision between a large galaxy, dubbed NGC 1232, and its much smaller dwarf neighbor. Assuming the conclusion is spot on, this giant cloud will be the first example of a cosmic collision that was found solely using its x-ray emission — ultimately helping to shed light on the role mergers play in galaxy evolution.

The attached images show the crime scene at wavelengths in the x-ray portion of the electromagnetic spectrum (seen in purple) and in optical light. Looking near the bright central region, we can see the colossal comet-like shock wave (caused by a similar mechanism to a sonic boom here on Earth) that was responsible for the inception of the hot gas cloud where the temperatures in the cooler portion hang around 6 million degrees. (The hottest areas can exceed multimillion degree temperatures) The motion of the smaller galaxy itself is responsible for the structure of the cloud, which hogs up a substantial portion of the face of the larger spiral galaxy when studying its x-ray emission.

Looking near the galactic center, we can see the result of this celestial shock wave, as it most likely ignited star-forming activity, creating several very energetic, massive, young stars. The stars in question are huge sources of x-ray emission, as stellar winds rip through the region. Supernovae shock waves are also a source of x-ray emissions. Therefore, their contributions can not be ignored.

Astronomers are currently unsure of the overall mass of the cloud, as we can only infer so much using a 2-dimensional image, but the overall mass should hinge on the the concentration of gas in the structure. Assuming the gas is distributed in a thin, pancake-like shape, it may have more mass than approximately 40 thousand suns, but if the material is distributed in a larger, spherical cone, it could contain the mass of more than 3 million suns (making it substantially more massive than a typical stellar-mass black hole)!

Over the course of the next several hundreds of millions of years (as the collision remains ongoing), the cloud will remain a heavy source of x-ray emission. Through studying the evolution of the cloud, astronomers will gain precious insight into the galactic collision process, perhaps allowing us to determine with accuracy how often these celestial mergers occur. (This is particularly important seeing as how our galaxy is scheduled to undergo a similar collision in about four billion years time, when the Andromeda galaxy, the Milky Way’s largest spiral neighbor, merges with our own).

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