Sloshing in its cD halo: MUSE kinematics of the central galaxy NGC 3311

Abstract

Early-type galaxies show a strong size evolution with redshift. This evolution is explained by fast "in-situ" star formation at high-$z$ followed by a late mass assembly mostly driven by minor mergers that deposit stars primarily in the outer halo. We aim to identify structural components of the Hydra I cD galaxy NGC 3311 to investigate the connection between the central galaxy and the surrounding stellar halo. We map the line-of-sight velocity distribution (LOSVD) using MUSE pointings covering NGC 3311 out to $25$ kpc. Combining photometric and spectroscopic data, we model the LOSVD maps using a finite mixture distribution, including four non-concentric, nearly isothermal spheroids, with different line-of-sight systemic velocities $V$, velocity dispersions $\sigma$, and higher order Gauss-Hermite moments $h_3$ and $h_4$. The comparison of the correlations between $h_3$ and $h_4$ with $V/\sigma$ with simulations indicates that NGC 3311 assembled mainly through dry mergers. The $\sigma$ profile rises to $\simeq 400$ km s${}^{\text{-}1}$ at 20 kpc indicating that stars there were stripped from progenitors orbiting in the cluster core. The finite mixture distribution modeling supports three inner components related to the central galaxy and a fourth component with large effective radius ($51$ kpc) and velocity dispersion ($327$ km s${}^{\text{-1}}$) consistent with a cD envelope. We find that the cD envelope is offset from the center of NGC 3311 both spatially (8.6 kpc) and in velocity ($\Delta V=204$ kms${}^{-1}$), but coincide with the cluster core X-ray isophotes and the mean velocity of galaxies. Also, the envelope contributes to the broad wings of the LOSVD measured by large $h_4$ within 10 kpc. The cD envelope of NGC 3311 is dynamically associated with the cluster core, which in Hydra I is in addition displaced from the cluster center, presumably due to a recent subcluster merger.

20 pages, 19 figures, accepted for publication on A&A

References in corpus (25)

• Five-Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Cosmological Interpretation
• The hierarchical formation of the brightest cluster galaxies
• Improving the full spectrum fitting method: accurate convolution with Gauss-Hermite functions
• The SAURON project -- IX. A kinematic classification for early-type galaxies
• The Importance of Mergers for the Origin of Intracluster Stars in Cosmological Simulations of Galaxy Clusters
• Kinematic properties of early-type galaxy haloes using planetary nebulae
• The Burrell Schmidt Deep Virgo Survey: Tidal Debris, Galaxy Halos, and Diffuse Intracluster Light in the Virgo Cluster
• The Formation and Evolution of Intracluster Light
• The SAMI Galaxy Survey: Revisiting Galaxy Classification Through High-Order Stellar Kinematics
• Intracluster light and the extended stellar envelopes of cD galaxies: An analytical description
• Brightest Cluster Galaxies at the Present Epoch
• The Carnegie-Irvine Galaxy Survey. III. The Three-Component Structure of Nearby Elliptical Galaxies
• Dearth of dark matter or massive dark halo? Mass-shape-anisotropy degeneracies revealed by NMAGIC dynamical models of the elliptical galaxy NGC 3379
• Velocity Bias from the Small Scale Clustering of SDSS-III BOSS Galaxies
• The stellar accretion origin of stellar population gradients in massive galaxies at large radii
• The MASSIVE Survey - V. Spatially-Resolved Stellar Angular Momentum, Velocity Dispersion, and Higher Moments of the 41 Most Massive Local Early-Type Galaxies
• Small scatter and nearly-isothermal mass profiles to four half-light radii from two-dimensional stellar dynamics of early-type galaxies
• The Cluster Velocity Dispersion of the Abell 2199 cD Halo of NGC 6166
• The early-type dwarf galaxy population of the Hydra I cluster
• The Kinematics of Intracluster Planetary Nebulae and the On-Going Subcluster Merger in the Coma Cluster Core
• The MASSIVE Survey - VIII. Stellar Velocity Dispersion Profiles and Environmental Dependence of Early-Type Galaxies
• The information content of stellar halos: Stellar population gradients and accretion histories in early-type Illustris galaxies
• Radial kinematics of brightest cluster galaxies
• The Rising Stellar Velocity Dispersion of M87 from Integrated Starlight
• A 3D view of the Hydra I galaxy cluster core - I. Kinematic substructures

Cited by in corpus (3)

• The Fornax Deep Survey with VST. VIII. Connecting the accretion history with the cluster density
• The Fornax3D project: Tracing the assembly history of the cluster from the kinematic and line-strength maps
• The first detection of ultra-diffuse galaxies in the Hydra I cluster from VEGAS survey