Connelly Publishes in <em>Astrophysical Journal</em> - Hamilton College
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Natalia Connelly
Natalia Connelly

Connelly Publishes in Astrophysical Journal

By Vige Barrie
Posted August 16, 2009
Tags Astronomy Faculty Physics
Assistant Professor of Physics Natalia Connelly published an article in the Astrophysical Journal titled "An Evolutionary Paradigm for Dusty Active Galaxies at Low Redshift." With co-authors from the University of Pennsylvania, Cornell and Caltech, Connelly considered a number of mid-infrared spectra of active galaxies obtained with the Spitzer Space Telescope.

These ultra-luminous infrared galaxies are among some of the brightest astronomical objects. They are almost always mergers of two galaxies and typically have a vigorous starburst and/or galactic nucleus activity. Their exact evolution remains unclear.

The authors applied two novel statistical techniques to the spectral sample: a Bayesian-based calculation of the degree to which a pair of galaxy spectra is similar or different; and a network-type diagram to visualize the resulting connections between galaxies. In researching the connections between galaxies the researchers found what they believe to be a fundamental evolutionary plane for these types of galaxies, showing three distinct phases. The first one lasts from the initial encounter of two galaxies to about the end of the merger. After this, some galaxies enter a phase where their starburst activity declines, while that of the galactic nucleus increases. This stage sometimes ends in the creation of a quasar. Other galaxies go through a different path, with a less prominent starburst decline almost never resulting in a quasar.

This research has opened a rich field of study. At Hamilton, an undergraduate, Will Eagan '11, spent the summer researching how the method could be extended to a sample of distant (high-redshift) galaxies, as well as how to rigorously analyze the network diagrams from the perspective of graph theory.


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