Thursday October 25th, 2012

On the Anomalous Silicate Absorption Feature of the Prototypical Seyfert 2 Galaxy NGC 1068

Melanie Koehler, Aigen Li (University of Missouri)
(Submitted on 24 Oct 2012)

The first detection of the silicate absorption feature in AGNs was made at 9.7 micrometer for the prototypical Seyfert 2 galaxy NGC 1068 over 30 years ago, indicating the presence of a large column of silicate dust in the line-of-sight to the nucleus. It is now well recognized that type 2 AGNs exhibit prominent silicate absorption bands, while the silicate bands of type 1 AGNs appear in emission. More recently, using the Mid-Infrared Interferometric Instrument on the Very Large Telescope Interferometer, Jaffe et al. (2004) by the first time spatially resolved the parsec-sized dust torus around NGC 1068 and found that the 10 micrometer silicate absorption feature of the innermost hot component exhibits an anomalous profile differing from that of the interstellar medium and that of common olivine-type silicate dust. While they ascribed the anomalous absorption profile to gehlenite (Ca_2Al_2SiO_7, a calcium aluminum silicate species), we propose a physical dust model and argue that, although the presence of gehlenite is not ruled out, the anomalous absorption feature mainly arises from silicon carbide.

Comments: 5 pages, 3 figures, published in MNRAS Letters
Subjects: Cosmology and Extragalactic Astrophysics (astro-ph.CO); Galaxy Astrophysics (astro-ph.GA)
Journal reference: MNRAS, 406, L6-L10 (2010)
Cite as: arXiv:1210.6562 [astro-ph.CO]
(or arXiv:1210.6562v1 [astro-ph.CO] for this version)

The SDSS-III Baryon Oscillation Spectroscopic Survey: The Quasar Luminosity Function from Data Release Nine

Nicholas P. Ross, Ian D. McGreer, Martin White, Gordon T. Richards, Adam D. Myers, Nathalie Palanque-Delabrouille, Michael A. Strauss, Scott F. Anderson, Yue Shen, W. N. Brandt, Christophe Yeche, Molly E. C. Swanson, Eric Aubourg, Stephen Bailey, Dmitry Bizyaev, Jo Bovy, Howard Brewington, J. Brinkmann, Colin DeGraf, Tiziana Di Matteo, Garrett Ebelke, Xiaohui Fan, Jian Ge, Elena Malanushenko, Viktor Malanushenko, Rachel Mandelbaum, Claudia Maraston, Demitri Muna, Daniel Oravetz, Kaike Pan, Isabelle Paris, Patrick Petitjean, Kevin Schawinski, David J. Schlegel, Donald P. Schneider, John D. Silverman, Audrey Simmons, Stephanie Snedden, Alina Streblyanska, Nao Suzuki,David H. Weinberg, Donald York
(Submitted on 23 Oct 2012)

We present a new measurement of the optical Quasar Luminosity Function (QLF), using data from the Sloan Digital Sky Survey-III: Baryon Oscillation Spectroscopic Survey (SDSS-III: BOSS). From the SDSS-III Data Release Nine (DR9), we select a uniform sample of 22,301 i<=21.8 quasars over an area of 2236 sq. deg with confirmed spectroscopic redshifts between 2.2<z<3.5, filling in a key part of the luminosity-redshift plane for optical quasar studies. We derive the completeness of the survey through simulated quasar photometry, and check this completeness estimate using a sample of quasars selected by their photometric variability within the BOSS footprint. We investigate the level of systematics associated with our quasar sample using the simulations, in the process generating color-redshift relations and a new quasar k-correction. We probe the faint end of the QLF to M_i(z=2.2) = -24.5 and see a clear break in the QLF at all redshifts up to z=3.5. We find that a log-linear relation (in log[Phi*] – M*) for a luminosity and density evolution (LEDE) model adequately describes our data within the range 2.2<z<3.5; across this interval the break luminosity increases by a factor of ~2.3 while Phi* declines by a factor of ~6. At z<2.2 our data is reasonably well fit by a pure luminosity evolution (PLE) model. We see only a weak signature of "AGN downsizing", in line with recent studies of the hard X-ray luminosity function. We compare our measured QLF to a number of theoretical models and find that models making a variety of assumptions about quasar triggering and halo occupation can fit our data over a wide range of redshifts and luminosities.

Comments: 28 pages, 19 figures, 9 tables. Submitted to The ApJ. All the necessary data and code used herein will be made publicly available at this http URL
Subjects: Cosmology and Extragalactic Astrophysics (astro-ph.CO)
Cite as: arXiv:1210.6389 [astro-ph.CO]
(or arXiv:1210.6389v1 [astro-ph.CO] for this version)
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