Stellar mass versus velocity dispersion as tracers of the lensing signal around bulge-dominated galaxies

Abstract

We present the results of a weak gravitational lensing analysis to determine whether the stellar mass or else the velocity dispersion is more closely related to the amplitude of the lensing signal around galaxies, hence to the projected distribution of dark matter. The lensing signal on smaller scales than the virial radius corresponds most closely to the lensing velocity dispersion in the case of a singular isothermal profile, but is also sensitive on larger scales to the clustering of the haloes. We have selected over 4000 lens galaxies at a redshift z < 0.2 with concentrated (or bulge-dominated) surface brightness profiles from the ∼300 square degree overlap between the Red-sequence Cluster Survey 2 (RCS2) and the data release 7 (DR7) of the Sloan Digital Sky Survey (SDSS). We consider both the spectroscopic velocity dispersion and a model velocity dispersion (a combination of the stellar mass, the size, and the Sérsic index of a galaxy). Comparing the model and spectroscopic velocity dispersion we find that they correlate well for galaxies with concentrated brightness profiles. We find that the stellar mass and the spectroscopic velocity dispersion trace the amplitude of the lensing signal on small scales equally well. The model velocity dispersion, however, does significantly worse. A possible explanation is that the halo properties that determine the small-scale lensing signal -mainly the total mass -also depend on the structural parameters of galaxies, such as the effective radius and Sérsic index, but we lack data for a definitive conclusion.

Stellar Velocity Dispersion: Linking Quiescent Galaxies to Their Dark Matter Halos

“…van Uitert et al (2013) investigate the relation between stellar mass and stellar velocity dispersion of galaxies and their dark matter halo mass as traced by weak gravitational lensing. They show that at small separations stellar mass and velocity dispersion both account for the lensing signal equally well.…”

The Velocity Dispersion Function of Very Massive Galaxy Clusters: Abell 2029 and Coma

“…This dispersion may be proportional to the dispersion of the DM halo and thus it may be a fundamental observable for studying the DM halo distribution (see Zahid et al 2016). The velocity dispersion is a reasonable halo mass proxy for early-type galaxies dominated by random motions (Wake et al 2012;van Uitert et al 2013;Bogdán & Goulding 2015;Zahid et al 2016). For late-type galaxies, the circular velocity is important for characterizing the disk (Sheth et al 2003).…”

“…Central velocity dispersion may be a more fundamental tracer of the DM halo (Wake et al 2012;van Uitert et al 2013;Bogdán & Goulding 2015;Zahid et al 2016). The central velocity dispersion reflects the stellar kinematics governed by the central gravitational potential well.…”

RCSLenS: testing gravitational physics through the cross-correlation of weak lensing and large-scale structure

“…The RCS2 team have presented a series of investigations of galaxy-galaxy lensing using these data, probing the occupation and shapes of dark matter halos (van Uitert et al 2011, Cacciato et al 2014) and the connection to galaxy luminosity, stellar mass and velocity dispersion (van Uitert et al 2013(van Uitert et al , 2015. We focus instead on cosmological applications of this dataset.…”