Creating Pancakes using Galaxy Collisions—Violent Origins of Disk Galaxies Probed by Radio Telescopes

Observations of colliding galaxies using ALMA and other radio telescopes have revealed that collisions between galaxies are likely to result in a galaxy with a gaseous disk structure. This is an important result, which gives us a clue about how disk galaxies like our own Milky Way form.

An international research group led by Junko Ueda, a JSPS (Japan Society for the Promotion of Science) postdoctoral fellow, investigated the distribution of molecular gas in 37 galaxies which are at the final stage of collisions between galaxies. They used data collected by radio telescopes from around the world, including ALMA. The group found that among the 30 colliding galaxies whose molecular gas was detected, 24 galaxies had molecular gas disks that were rotating. Furthermore, it turned out that a half of these rotating molecular disks were larger than the central concentration of stars. If the gas disks eventually form stars, these remnants of galaxy collisions are likely to evolve into a new galaxy that have both stellar and gas disks.

Figure
Distributions of gas in merging galaxies observed by radio telescopes. Contours indicate the radio intensity emitted from CO gas. The color shows the motion of gas. The red color indicates gas is moving away from us while the blue color is coming closer to us. The gradation from red to blue means that gas is rotating in a disk-like manner around the center of the galaxy.
Credit: ALMA (ESO/NAOJ/NRAO)/SMA/CARMA/IRAM/J. Ueda et al./Wilson et al./Hunt et al./Jütte et al.

These observation results were published in The Astrophysical Journal Supplement (August 2014) as Ueda et al. “COLD MOLECULAR GAS IN MERGER REMNANTS. I. FORMATION OF MOLECULAR GAS DISKS.”

For details, see Press Release: Creating Pancakes using Galaxy Collisions—Violent Origins of Disk Galaxies Probed by Radio Telescopes.

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