Monday, October 1, 2012
Astronomy Tea Talk
The Reddest Quasars: A Transitional Phase in Quasar/Galaxy Co-Evolution
Eilat Glikman, Yale
We have identified a large population of dust-reddened quasars by matching radio sources detected in the FIRST survey to the 2MASS near-infrared catalog (F2M) and selecting sources with red optical-to-near-infrared colors. We followed up our candidates with optical and/or near-infrared spectroscopy and have identified ~120 dust-reddened quasars, defined as having at least one broad emission line in and a reddening of E(B-V) \gtr 0. 1. The sample spans a wide redshift range, 0. 1 \lt z \lt 3 and reaches a reddening, E(B-V) = 1.5. When corrected for extinction, red quasars are the most luminous objects at every redshift and their fraction increases with luminosity. The properties of red quasars suggest that they are revealing an evolutionary phase where the heavily obscured quasar is emerging from its dusty environment prior to becoming a "normal" blue quasar. We compute the fraction of quasars that are in this red phase and determine that its duration is ~20% as long as the unobscured quasars phase: a few million years. I will also report on an expansion of this sample to fainter flux limits with UKIDSS, where we discover reddened quasars at z \gtr 2. And I will present future work on these object to better understand their role in the co-evolution of quasars and galaxies.