Seminars and Colloquia

Shallower slope in Baryonic Tully-Fisher relation with parameters derived from 3D kinematic modelling and robust mass modellingAstrophysics Seminar

by Prerana Biswas (Indian Institute of Astrophysics)

Asia/Kolkata
Auditorium

Auditorium

Description

Abstract

The Baryonic Tully-Fisher relation (BTFR) is one of the most important relations in astrophysics, it correlates the baryonic mass and the rotation velocity of galaxies and has extensive use in distance estimation, in the determination of the value of the Hubble constant, in studying local galaxy flows, in examining the galaxy formation models etc. Different measures of rotation velocities have been used over the past decades to establish this relation. Initially, the widths of the HI spectra measured in single-dish observations were mostly used as a proxy of the rotation velocity and they were corrected mostly with the optical inclinations. Later and most recent works on this mainly involve rotation velocity measured from the 2D-kinematically modelled data , i.e., kinematic modelling done on a 2-dimensional velocity field. However, 2D modelling is affected by the beam smearing and projection effect. But, 3D modelling, i.e., the kinematic modelling done on a 3-dimensional data cube, is not affected by it and provides us a more accurate description of the kinematics of the galaxies. There can be significant differences between rotation velocity and kinematic inclination between 2D and 3D modelling. Besides that, most of the previous results of this work involve a very heterogeneous data set and different techniques for measuring the velocity as well as the mass of the galaxies. In our study, with the homogenous data products of 18 galaxies from GARCIA (GMRT ARChIve Atomic gas survey) and CALIFA ( Calar Alto Legacy Integral Field Area survey), we revisit this relation. In this regard, we first built the 3D kinematic modelling to get the accurate measurement of the rotation velocity and the kinematic inclination and then built a process of robust mass modelling for the accurate description of the mass. Our process of mass modelling involves 3D modelled rotation curve, Multi-Gaussian Expansion method (MGE) and JeansAnisotropic Modelling (JAM) to derive stellar kinematics and finding out the contribution of gas directly from the 3D-modelled surface density, i.e., without assuming any profile beforehand through our own developed method. For the modelling of the rotation curve, we used Markov Chain Monte Carlo (MCMC) optimization method and unlike most of the previous studies, our choice of priors are fully motivated by the previous observations and does not assume any scaling relations . With the results from the 3D kinematical modelling and the robust mass modelling, we revisit the BTFR and our study shows a shallower slope in BTFR in comparison to the previous results. However, currently, our sample size is moderate, but, with the upcoming uniformly analysed data products of the GARCIA survey, it can be stated with more confidence.