Program: GS-2008B-Q-86
Title: | The evolution of luminous obscured quasars: Bright 24 micron sources |
PI: | Susan Ridgway |
Co-I(s): | Mark Lacy, Anna Sajina, Craig Harrison, Lisa Storrie-Lombardi, Duncan Farrah |
Abstract
We are currently undertaking a spectroscopic survey of luminous AGN and
quasars selected in the mid-infrared from Spitzer shallow
surveys. Mid-infrared selection is much less biased with respect to
obscuration than optical and X-ray techniques, and hence enables the
discovery of obscured quasars as well as normal, unobscured ones. Our
survey therefore provides an unique opportunity to construct luminosity
functions for both obscured and unobscured quasars selected in the same
way and covering similar redshifts and luminosities. Our 4m class
spectroscopic observations have so far have yielded about 150
redshifts, but our luminosity functions are lacking lower luminosity
objects at high redshift and high luminosity objects at low redshift.
We have been granted 3 nights of classical time at Gemini S to find lower
luminosity z > 1 obscured quasars by targeting objects with faint 24 micron fluxes.
We have been granted two nights at SOAR with the Goodman Spectrograph, which should allow
us to target about half the available bright 24 micron objects.
We are therefore requesting poor weather Gemini S GMOS time to obtain redshifts for
another 15 bright 24 micron objects. Obtaining sufficient numbers of these thinly spread, brighter
24 micron sources is vital to filling
out this missing portion of the luminosity/redshift plane, and will allow
us to disentangle any luminosity dependence of the obscured quasar
fraction from its evolution with redshift. This will allow us to test
models of the obscured quasar population, in particular at the highest
redshifts and luminosities where we are seeing a previously
undiscovered population of obscured objects.
Publications using this program's data
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[data]
[ADS] The Spitzer Mid-infrared Active Galactic Nucleus Survey. I. Optical and Near-infrared Spectroscopy of Obscured Candidates and Normal Active Galactic Nuclei Selected in the Mid-infrared