报告题目:The Activation of Galactic Nuclei and Their Accretion Rates are Linked to Both Star Formation and Bulge-types of Their Host

报  告  人:Dr. Hassen Yesuf (KIAA)

报告时间:Friday, June 14, 2019, 02:00pm

报告地点:蒙民伟科技南楼S727

报告摘要:I will present our work in which we use bulge-type classifications of representative galaxies from the Sloan Digital Sky Survey by Gadotti (2009) to classify galaxies into real bulges and pseudobulges using a machine learning algorithm. We use structural and stellar population predictors that can be measured easily without image decomposition into bulge, bar and disc as done in the training sample. We find that multiple parameters such as the central mass density within 1 kpc, the concentration index, and Sersic index result in accurate bulge classification when combined together. We classify about 45,000 massive galaxies (> 10^10 solar mass) below 0.07 redshift into real bulges or pseudobulges with 93% accuracy. We then show that about 75 - 90% of AGNs are hosted by galaxies with real bulges. The pseudobulge fraction significantly decreases with AGN line ratio signatures as the ratios change from indicating pure star formation (~55%), to composite of star formation and AGN (~20%), and to AGN-dominated galaxies (~5%). Using the dust-corrected [O III] luminosity as an AGN accretion indicator, we find that AGNs in host galaxies with real bulges have lower [O III] luminosity per black hole mass (Eddington ratios) than AGNs in pseudobulges. But real bulges have a wide range of AGN and star formation activity. For both bulge types, the specific black hole accretion rates are significantly correlated with both specific star formation rates and bulge types. Real bulges have lower specific accretion rate but higher AGN fraction than pseudobulges do at similar specific star formation rates.