The SAMI Galaxy Survey: Toward a Unified Dynamical Scaling Relation for Galaxies of All Types
L. Cortese, L. M. R. Fogarty, I. -T. Ho, K. Bekki, J. Bland-Hawthorn, M. Colless, W. Couch, S. M. Croom, K. Glazebrook, J. Mould, N. Scott, R. Sharp, C. Tonini, J. T. Allen, J. Bloom, J. J. Bryant, M. Cluver, R. L. Davies, M. J. Drinkwater, M. Goodwin, A. Green, L. J. Kewley, I. S. Kostantopoulos, J. S. Lawrence, S. Mahajan, A. M. Medling, M. Owers, S. N. Richards, S. M. Sweet, O. I. Wong
November 2014Abstract
We take advantage of the first data from the Sydney-AAO Multi-object Integral field Galaxy Survey to investigate the relation between the kinematics of gas and stars, and stellar mass in a comprehensive sample of nearby galaxies. We find that all 235 objects in our sample, regardless of their morphology, lie on a tight relation linking stellar mass (M ) to internal velocity quantified by the S parameter, which combines the contribution of both dispersion (σ) and rotational velocity (V ) to the dynamical support of a galaxy (S=sqrt0.5 V_rot+σ ). Our results are independent of the baryonic component from which σ and V are estimated, as the S of stars and gas agree remarkably well. This represents a significant improvement compared to the canonical M versus V and M versus σ relations. Not only is no sample pruning necessary, but also stellar and gas kinematics can be used simultaneously, as the effect of asymmetric drift is taken into account once V and σ are combined. Our findings illustrate how the combination of dispersion and rotational velocities for both gas and stars can provide us with a single dynamical scaling relation valid for galaxies of all morphologies across at least the stellar mass range 8.5 <log (M /M ) < 11. Such relation appears to be more general and at least as tight as any other dynamical scaling relation, representing a unique tool for investigating the link between galaxy kinematics and baryonic content, and a less biased comparison with theoretical models.
Publication
Astrophysical Journal Letters