Cottrell College Science Awards - 2014
Quasar/Galaxy Co-Evolution Caught in the Act: Understanding the Physics of Feedback
Supermassive black holes (SMBHs) are millions to billions of times more massive than our sun. It is now generally believed that SMBHs, some of them spinning at half the speed of light, reside at the center of most galaxies.
But the precise relationship between the growth of these matter-eating, space-and-time crunching monsters and the growth of their host galaxies remains a major cosmological puzzle. Eilat Glikman, assistant professor of physics at Middlebury College, is exploring this phenomenon.
She is interested in quasars and their role in the formation and evolution of galaxies. “Quasar” is short for “quasi-stellar radio source.” They are incredibly bright geysers of matter and energy observable only in far-distant galaxies. Glikman couldn’t have picked a better era to study them.
Before the 1990 launch of the Hubble Space Telescope, many believed quasars were isolated star-like objects. But data returned from the Hubble revealed they reside at the center of galaxies. Thus, most astronomers now operate on the assumption that SMBHs and quasars are different aspects of the same beating galactic heart.
Glikman intends to analyze data from more than 120 “dust-reddened quasars.” These are the most luminous objects in the universe, even when adjusted for redshift (a function of speed moving away from the observer, not to be confused with “dust-reddened,” which is due to light shining through cosmic dust). They are found in galaxies that are actively merging and whose black holes are growing at very high rates.
Or rather, were merging and growing – dust-reddened quasars are found only among some of the oldest galaxies we can observe, their light is reaching us from billions of years in the past.
Glikman notes, “The properties of red quasars suggest that they are revealing a transitional phase where the heavily obscured quasar is emerging from its dusty environment prior to becoming a ‘normal’ blue quasar.” She theorizes that this phase may last only a few million years.
In an attempt to understand how the energy output of quasar/SMBHs couples to galaxies, she will analyze high-resolution images of the host galaxies and measure star formation rates. She hopes spectroscopy and X-ray observations will allow her to track energy outflows and measure how black holes absorb nearby stellar gasses.