The Assembly of the Virgo Cluster, Traced by its Galaxy Halos

Abstract

Kinematic studies have produced accurate measurements of the total dark matter mass and mean dark matter density within the optical extent of galaxies, for large samples of objects. Here we consider theoretical predictions for the latter quantity, ${\bar{\rho }}_{dm}$, measured within the isophotal radius $R_{23.5}$, for isolated halos with universal density profiles. Through a combination of empirical scaling relations, we show that ${\bar{\rho }}_{dm}$ is expected to depend weakly on halo mass and strongly on redshift. When galaxy halos fall into larger groups or clusters they become tidally stripped, reducing their total dark matter mass, but this process is expected to preserve central density until an object is close to disruption. We confirm this with collisonless simulations of cluster formation, finding that subhalos have values of ${\bar{\rho }}_{dm}$ close to the analytic predictions. This suggests that ${\bar{\rho }}_{dm}$ may be a useful indicator of infall redshift onto the cluster. We test this hypothesis with data from the SHIVir survey, which covers a reasonable fraction of the Virgo cluster. We find that galaxies with high ${\bar{\rho }}_{dm}$ do indeed trace the densest regions of the cluster, with a few notable exceptions. Samples selected by environment have higher densities at a significance of 3.5-4$\sigma$, while samples selected by density are more clustered at 3-3.5$\sigma$ significance. We conclude that halo density can be a powerful tracer of the assembly history of clusters and their member galaxies.

17 pages, 18 figures; accepted for publication in MNRAS

References in corpus (14)

• Overview of the SDSS-IV MaNGA Survey: Mapping Nearby Galaxies at Apache Point Observatory
• The redshift dependence of the structure of massive LCDM halos
• The SAMI Galaxy Survey: instrument specification and target selection
• A universal model for halo concentrations
• Galaxy Groups within 3500 km s${}^{-1}$
• The GALEX Ultraviolet Virgo Cluster Survey (GUViCS). IV: The role of the cluster environment on galaxy evolution
• The origin of HI-deficiency in galaxies on the outskirts of the Virgo cluster. I. How far can galaxies bounce out of clusters?
• The Different Environmental Dependencies of Star-formation for Giant and Dwarf Galaxies
• The Near-IR Luminosity Function and Bimodal Surface Brightness Distribution of Virgo Cluster Galaxies
• The phase-space structure of tidally stripped halos
• The Spectroscopy and H-band Imaging of Virgo cluster galaxies (SHIVir) Survey: Scaling Relations and the Stellar-to-Total Mass Relation
• The Next Generation Virgo Cluster Survey. IX. Estimating the Efficiency of Galaxy Formation on the Lowest-Mass Scales
• The Unusually High Halo Concentration of the Fossil Group NGC 6482: Evidence for Weak Adiabatic Contraction
• The Mass Growth and Stellar Ages of Galaxies: Observations versus Simulations

Cited by in corpus (2)

• Leavers and remainers: Galaxies split by group-exit
• Properties of Globular Clusters in Galaxy Clusters: Sensitivity from the Formation and Evolution of Globular Clusters