Superthin Galaxies Contain Large Amounts of Dark Matter
Examples of blue (EON 32.766 6.667, top) and red (EON 149.150 20.646, bottom) superthin galaxies. The horizontal bar in each panel demonstrates the scale in arcseconds and kpc at the distance of the galaxies.
The thinnest disk galaxies have been studied a long time because of their unusual appearance. Why are they so thin? It is unclear what preserves the disks in this state. These rare galaxies are a mystery.
An international group of astrophysicists, including Halmos College physics faculty Stefan Kautsch, Ph.D., recently published an article on the spectral observations of 138 superthin galaxies (STGs). Using the Dual Imaging Spectrograph on the 3.5m telescope at the Apache Point Observatory located in the Sacramento Mountains in Sunspot, New Mexico, the research group focused on spectroscopic observations of STGs and how those may help explain the resistance of STGs against morphological transformations and disk thickening.
“We discovered that the thinnest spiral galaxies, the so called superthins, contain very big amounts of Dark Matter. It is like this unknown material squeezes the stellar galactic disks in those galaxies into their superthin state,” Kautsch said.
The researchers found that most of the STGs reviewed were dark matter dominated. Their rotational velocity and dark halo mass correlates with galactic color. The blue STGs also have less compact dark halos than the red STGs, whereas the galaxies in both color groups have their halo-to-disk scales ratios under two.
Their results are published in The Astrophysical Journal, published by the American Astronomical Society.