Astronomy Colloquium 2022 Fall Semester

* Date

Nov 24

* Speaker

오슬희(ANU/연세대학교)

* Title

Kinematics of galaxy bulges, disks, and ionised gas from 3D spectroscopy

* Abstract

Galaxies show a wide range of kinematic properties according to galaxy types. We aim to quantitatively understand the intrinsic distribution of bulge and disk kinematics, and how two components describe the overall distribution of stellar kinematics of galaxies. The spatially-resolved rotation velocity and the velocity dispersion of bulge and disk components have been simultaneously estimated for the SAMI 3D spectroscopy data using the penalised pixel fitting method. Kinematic scaling relations demonstrate that the galaxy stellar mass scales with kinematics for both bulge and disk components of all galaxy types, which suggests kinematics of two components are less dependent on galaxy populations and largely determined by the mass. We quantitatively show that the bulge and disk components are kinematically distinct: the two components show scaling relations with similar slopes, but different intercepts; the spin parameter λR indicates bulges (disks) are pressure(rotation)-dominated systems. Our findings suggest that the relative contributions of bulge and disk components explain, at least to first order, the complex kinematic behaviour of galaxies according to galaxy type. On the other hand, kinematics of ionised gas are significantly impacted by power sources (e.g. star formation, AGN, and old stars), unlike stellar kinematics. For star-forming galaxies, the stellar velocity dispersion tends to be larger than the gas velocity dispersion, suggesting that stars are, in general, dynamically hotter than the ionised gas (asymmetric drift). However, AGN show gas velocity dispersions comparable to stellar ones, implying their gas kinematics have been dynamically heated by AGN activities (e.g. outflows).