The SAMI Galaxy Survey: Mass as the Driver of the Kinematic Morphology–Density Relation in Clusters

Abstract

We examine the kinematic morphology of early-type galaxies (ETGs) in eight galaxy clusters in the Sydney-AAO Multi-object Integral-field spectrograph Galaxy Survey. The clusters cover a mass range ofand we measure spatially resolved stellar kinematics for 315 member galaxies with stellar masses11.7 within 1 R 200 of the cluster centers. We calculate the spin parameter, λ R , and use this to classify the kinematic morphology of the galaxies as fast or slow rotators (SRs). The total fraction of SRs in the ETG population is F SR = 0.14 ± 0.02 and does not depend on host cluster mass. Across the eight clusters, the fraction of SRs increases with increasing local overdensity. We also find that the slow-rotator fraction increases at small clustercentric radii (R cl < 0.3 R 200 ), and note that there is also an increase in the slow-rotator fraction at R cl ∼ 0.6 R 200 . The SRs at these larger radii reside in the cluster substructure. We find that the strongest increase in the slow-rotator fraction occurs with increasing stellar mass. After accounting for the strong correlation with stellar mass, we find no significant relationship between spin parameter and local overdensity in the cluster environment. We conclude that the primary driver for the kinematic morphology-density relationship in galaxy clusters is the changing distribution of galaxy stellar mass with the local environment. The presence of SRs in the substructure suggests that the cluster kinematic morphology-density relationship is a result of mass segregation of slow-rotating galaxies forming in groups that later merge with clusters and sink to the cluster center via dynamical friction.

The 13th Data Release of the Sloan Digital Sky Survey: First Spectroscopic Data from the SDSS-IV Survey Mapping Nearby Galaxies at Apache Point Observatory

“…The Early Data Release (Allen et al 2015) provided data for 107 galaxies, while the first major data release (Green et al 2017) includes 772 galaxies. Science results from the SAMI survey so far include characterizing the galactic winds or extended diffuse ionizing gas in edge-on disk galaxies (Ho et al 2016), mapping the quenching of star formation proceeding from the outside in in dense environments (Schaefer et al 2017), and identifying stellar mass as the main variable affecting the fraction of ETGs that are slow rotators (Brough et al 2017).…”

Kinematics of simulated galaxies II: Probing the stellar kinematics of galaxies out to large radii

“…Earlier studies found a strong correlation between the stellar mass of a galaxy and its central kinematics. According to these studies the fraction of slow rotators increases significantly with stellar mass (Brough et al 2017;Jimmy et al 2013;Veale et al 2017). In order to extend this to the halo kinematics, we study the relation between the profile shape and stellar mass.…”

SDSS-IV MaNGA: Uncovering the Angular Momentum Content of Central and Satellite Early-type Galaxies

“…When the mass distributions are carefully matched, the difference in  l out is not significant, with an Anderson-Darling test returning a probability = P 33% that the two distributions match. In a companion paper , we further compare the fast-and slow-rotator fractions as a function of local overdensity to compare with the recent literature (e.g., Cappellari 2016; Brough et al 2017;Veale et al 2017a). …”

“…We have long understood that rotational support s V (with V the maximum radial velocity and σ the stellar velocity dispersion) is a function of internal galaxy properties, with lower-mass ellipticals and S0s (earlytype galaxies) having more rotation than the most massive elliptical galaxies (e.g., Binney 1978;Davies et al 1983;Bender et al 1989;Franx & Illingworth 1990;Kormendy & Bender 1996). IFS studies have definitively shown that *L early-type galaxies typically have some net rotation , while the most massive elliptical galaxies tend to have little to no net rotation (e.g., Emsellem et al 2011;Houghton et al 2013;Raskutti et al 2014;Scott et al 2014;Brough et al 2017;Oliva-Altamirano et al 2017;Veale et al 2017aVeale et al , 2017b.…”