II- A hydrodynamical CLONE of the Virgo cluster to confront observed and synthetic galaxy population twins in a dense environment

Abstract

Galaxy clusters offer powerful laboratories for studying galaxy evolution in dense environments. In this context, the CLONE, Constrained LOcal and Nesting Environment, project provides a zoom-in hydrodynamical simulation of the Virgo cluster, including AGN and supernovae feedback, with a resolution down to 350 pc, designed to mirror Virgo's observed properties. Previous work showed that this replica and Virgo share the same history, mass and luminosity distributions including the central M87. This study examines several observational relations extending to lower stellar masses than previous synthetic-population studies: star formation density, (specific) star formation rate, metallicity and quenched fraction of galaxies as a function of stellar mass and cluster-centric distance. The aim is to assess how simulated and observed trends compare. Despite slightly low metallicity and high, but then enough, quenched fraction, simulated galaxies reproduce key observational trends even without averaging or accounting for observational uncertainties, aside from the consideration of projection effects: At fixed stellar mass, cluster galaxies form fewer stars than field counterparts. Most galaxies are quenched but for those of intermediate mass or isolated. Low-mass galaxies are highly quenched implying a sharp metallicity drop, and low metallicity does not imply youth. Quenching occurs earlier for the most massive and the smallest galaxies than for those of intermediate mass at least until they enter the cluster. Quenched galaxies have undergone dark matter stripping. Gas depletion drives quenching, especially in low-mass galaxies and the farther from the cluster center they are. Overall, the synthetic population reproduces jointly multiple observational trends, making it a valuable tool to probe processes from jellyfish galaxies to cluster-core gas dynamics. [Shorten]

Figures (14)

• Figure 1: Star formation density by bin of r-band magnitude (top) and stellar mass (bottom). The observed star formation density shown as the solid orange line is from a volume complete down to a mass limit of 10$^{8}$ M$_\odot$ sample of SDSS galaxies biased towards field ones. The simulated star formation density shown as filled (open) black circles is obtained considering all the galaxies within a $\sim$12 Mpc radius sphere centered on the cluster (between 6 and 12 Mpc from the cluster center). The dashed orange lines (black error bars) in the top panel stand for the uncertainties of the observational (simulated) star formation density obtained with bootstrap resampling. The good agreement between the observed and synthetic relations tends to highlight the fact that galaxies in the cluster are more likely to be quenched, those of intermediate stellar mass (10$^{10}$-10$^{11}$ M$_\odot$) being somewhat spared.
• Figure 2: Galaxy SFR as a function of their stellar mass within a SDSS complete down to a mass limit of 10$^8$ M$_\odot$ biased toward field galaxies (yellow three dots-dashed line) as well as within the virial radius of the simulated cluster (inside, red), within $\sim$6 Mpc but beyond the virial radius (outskirt, blue) and within [6,12] Mpc (suburb, black). Transparent areas stand for the 16th and 84th percentiles. Solid orange lines are averages obtained splitting star forming and passive galaxies in a larger SDSS galaxy sample 2013MNRAS.428.3306W. The separation between the two regimes or quenched limit is shown as dashed (orange) lines in all cases. Top: Whole synthetic population represented as open and filled black circles if star forming or quenched respectively. Middle: The light yellow lines stand for synthetic populations from other simulations 2024MNRAS.528.4891G, from a higher-$z$ sample of environment-agnostic galaxies called MaNGA 2019MNRAS.482.1557S, and from a low-$z$ sample of environment-agnostic galaxies 2019ApJS..244...24L. Bottom: The green solid line, green open and blue open diamonds stand for galaxies observed within the Virgo cluster from 2023AA...669A..73B2024AA...683A.149E2022AA...657A...9C respectively with those from VESTIGE biased toward inner core and ram-pressure affected galaxies. Most simulated galaxies are quenched, meaning that the cluster rich environment affects galaxy star formation out to large radii.
• Figure 3: Stellar-to-halo mass relation for galaxies inside the cluster (red), in its outskirt (blue) and in its suburb (black). See Fig. \ref{['fig:stellarssfr']} for definitions. The relation is also given for Horizon-AGN 2016MNRAS.463.3948D, for simulated late type galaxies 2017ApJ...843...74O and for four different surveys with yellow and orange lines: galaxy clusters (three-dots dashed), COSMOS (dashed), CFHTLenS (dot-dashed line) and SHIVir (dotted) 2018AstL...44....8K2012ApJ...744..159L2015MNRAS.447..298H2017ApJ...843...74O. The agreement between the cluster survey and the simulated galaxies within the cluster is remarkable: galaxies within the cluster have a higher stellar mass than galaxies in the field given their total mass because they have been stripped of their dark matter content upon entering in the rich cluster environment.
• Figure 4: Fraction of quenched galaxies per bin of galaxy stellar mass (left and right) and galaxy dark matter halo mass (middle). All the galaxies within a $\sim$12 Mpc radius sphere centered on the cluster are considered (violet). Left and middle: Galaxies are split into galaxies inside the cluster (red), in its outskirt (blue) and in its suburb (black). See Fig. \ref{['fig:stellarssfr']} for definitions. Solid lines are obtained considering real galaxy distances to the cluster center while dashed lines are derived using projected galaxy distances to the cluster center. Note that this projection is limited by the size of the zoom-in region. It thus constitutes only a low limit to the effect that exists in observations, all the more that the main filament linking the Virgo cluster to the cosmic web is quasi-aligned with the line of sight. Left: Filled circles and their error bars are quenched fractions and their standard deviations derived for galaxies within observed and simulated clusters and galaxy populations. 2012MNRAS.424..232W stands for the sample the closest to our cluster case as they consider observed galaxies in clusters with mass between 10$^{14.5}$ and 10$^{15}$ M$_\odot$ (large orange circles), then comes galaxies from the GOGREEN cluster surveys at redshift greater than 1 2023MNRAS.518.4782K, and finally galaxies from UltraVISTA DR1 and 3D-HST surveys 2016ApJ...827L..25M. Smaller filled circles stands for synthetic galaxy populations from simulations and semi-analytical modeling 2023MNRAS.518.4782K2025MNRAS.537.1849S2024AA...687A..68D. Right: Galaxies are split according to their degree of isolation. Central galaxies are thus in dark blue while their satellites are in light blue, yellow, orange and red. To summarize, the closest to the cluster core, the highest the probability to be quenched. The more isolated, the lowest the probability to be quenched. There exists an intermediate mass bin where galaxies are less likely to be quenched.
• Figure 5: Ratio of the gas mass to the stellar mass as a function of the stellar mass of the galaxies. Simulated galaxies are split into galaxies inside the cluster (red), in its outskirt (blue) and in its suburb (black). See Fig. \ref{['fig:stellarssfr']} for definitions. Dotted black lines delimit the regions that include galaxies poor in gas to those normal/rich in gas in the Virgo cluster according to 2021JKAS...54...17M. In addition, orange diamonds show the galaxies they select from their sample that are not impacted to those grandly impacted by ram-pressure stripping from top left to bottom right in the diagram. Open and filled black circles stand for our star forming and quenched galaxies respectively. The size of the circles is proportional to the isolation of the galaxy, the less isolated the galaxy is the larger the circle is. Interestingly, at fixed stellar mass, galaxies in the suburb are on average gas poorer than those in the outskirt that are themselves gas poorer than those inside the cluster suggesting that low-mass galaxies are indeed pre-processed via gas depletion before entering the cluster.