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Subaru Seminars are
usually held in Room 104 of the Hilo Base Facility, adjacent
to the main lobby. Everyone is welcome to attend. If you would like to
give a seminar, please contact Subaru seminar organizers
(Thayne Currie, Tae-Soo Pyo, Nagayoshi Ohashi)
by email : sseminar_at_subaru.naoj.org (please change"_at" to @).
June 15, Thursday, 11am in 104A
"Gas Content of Quasar Host Galaxies "
Jinyi Shangguan (Kavli Institute for Astronomy and Astrophysics at Peking University)
The interstellar medium content is crucial to understand the physics of AGNs and the co-evolution between supermassive black holes and their host galaxies. However, direct gas measurements are time consuming, and not without their own limitations and uncertainties. We advocate the alternative strategy of using dust as an efficient and effective indirect probe of the total (atomic and molecular) gas content of AGNs. I will introduce a detailed study of the infrared spectral energy distributions of bright, low-redshift (z lt 0.5) quasars selected from the Palomar-Green sample, using complete (1 to 500 micron) data obtained from 2MASS, WISE, Spitzer (IRS spectra) and Herschel. With a newly developed Bayesian Markov Chain Monte Carlo fitting method, we quantitatively decompose various overlapping contributions to the integrated spectral energy distribution, including starlight from the host, hot dust from the central engine and torus, and cooler dust emanating from larger scales in the host galaxy. This procedure yields a robust total dust mass, which we use to infer the total gas mass, using a dust-to-gas ratio estimated from the host galaxy stellar mass. Most quasar host galaxies have gas fractions similar to those of massive, star-forming galaxies, although a minority seem genuinely deficient in gas, resembling early-type galaxies. I will discuss the reliability of our gas estimates and the implication of our results for AGN feedback.