Mason Professor Looks at the Ins and Outs of Galaxies

Posted: April 16, 2008 at 1:00 am, Last Updated: November 30, -0001 at 12:00 am

By Tara Laskowski

Shobita Satyapal
Shobita Satyapal

Shobita Satyapal wants to know how galaxies form and evolve. In her field, she says there is a “sea of questions” surrounding galaxies — so much is uncertain or unknown.

However, the associate professor of physics and astronomy made a breakthrough in one area recently and surprised the science world by discovering a different property in certain types of galaxies.

Most galaxies have bulges at their centers and discs surrounding them. It is believed that galaxies with bulges have a huge black hole at their center, and that the mass of the black hole is proportional to the mass of the bulge.

Then there are the rogue galaxies without a bulge. Satyapal is especially interested in these “skinny” galaxies. These galaxies, because they have no bulge, were assumed not to have a black hole at their center.

“Before, we thought that the black hole and the bulge surrounding it were formed together or were somehow related,” Satyapal says. “But then we began to wonder if even the bulge-less galaxies had black holes at their centers, and we just weren’t able to see them.”

Thin galaxies, Satyapal explains, typically have a lot of gas and dust and surrounding their nuclear regions, making it very difficult to see through to the center with optical telescopes.

Satyapal used the Spitzer Space telescope to “look” at these galaxies in the infrared, which penetrates through the gas and dust and allows one to see into the galaxy’s center. This was a novel method — and the results were surprising. She found that eight of the 33 flat galaxies she looked at had active black holes at their center.

“This shows we just aren’t looking at these galaxies in the right way,” says Satyapal. “This will have an impact on theories of galaxy formation and evolution.”

Satyapal’s results imply that galaxy bulges are not necessary for black hole growth. She believes that “dark matter” — a substance that no one in the science world yet understands — plays a significant role in the growth and evolution of galaxies.

The results of her study will be published in the April 20 issue of the Astrophysical Journal. She will also be featured this month on the television program “Around Space.”

Satyapal has a BS in physics from Bryn Mawr College and a PhD in physics and astronomy from the University of Rochester. After postdoctoral work at the National Air and Space Museum and Goddard Space Flight Center, she was employed by the Space Telescope Science Institute and was an instrument scientist for the James Webb Space Telescope, due to launch in 2013. Satyapal received a NASA Presidential Early Career Award in 1998 and joined the Mason faculty in 2001.

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