The role of gas stripping in the quenching of satellite galaxies using SHARK v2.0

TL;DR

This study uses SHARK v2.0, a forward-modelled semi-analytic framework, to dissect satellite quenching in group and cluster environments by calibrating hot-halo and cold-gas stripping against SDSS measurements. By constructing realistic SDSS-like mock observations and matching the spectroscopic selection, the authors show that gradual stripping prescriptions with α_hot = α_cold = 500 best reproduce observed quenched fractions for low- and intermediate-mass satellites, while high-mass quenching remains AGN-dominated. Quenching timescales exceed ~2 Gyr and are longer in groups than clusters, supporting starvation as the dominant mechanism for most satellites, with environmental effects being more efficient in clusters. The work demonstrates the value of forward modelling and PPS-informed infall times to constrain environmental processes and highlights the need to consider measurement biases when comparing simulations to surveys.

Abstract

Observational studies have made substantial progress in characterizing quenching as a function of stellar mass and environment, but they are often limited in their ability to constrain quenching timescales and to determine the dominant environmental process responsible for the shutting down of star formation. To address this, we combine recent Sloan Digital Sky Survey (SDSS) observations with the SHARK v2.0 semi-analytic model to study the quenching of satellite galaxies in groups and clusters. We generate mock SDSS-like observations to calibrate the hot halo and cold interstellar medium (ISM) gas stripping prescriptions against observed satellite quenched fractions, finding that the previously adopted stripping prescriptions in SHARK v2.0 are too aggressive and overestimate the quenched fraction of satellite galaxies. Reducing the efficiency of both hot and cold gas stripping yields excellent agreement with observations for low- and intermediate-mass satellite galaxies. We use the calibrated model to investigate quenching timescales and find that satellites quench more quickly in clusters compared to groups, with timescales that generally decrease with increasing stellar mass. The long (>2 Gyr) timescales we measure favour hot halo gas removal as the dominant driver of satellite quenching.

Figures (8)

• Figure 1: Distribution of hot halo gas stripping radii (top panel) and cold ISM gas stripping radii (bottom panel) normalized by the virial radius of the galaxy at infall for satellites with $9 < \log_{10}(M_{\star}/\mathrm{M}_{\odot}) < 9.5$ falling into clusters. Different colours correspond to Shark runs with different $\alpha_{\mathrm{hot}}\,$ and $\alpha_{\mathrm{cold}}\,$ parameters, as shown in the legend. Note the top and bottom panels have different limits on the x-axis, and the y-axis is truncated to more clearly show the differences between different $\alpha_{\mathrm{hot}}\,$ and $\alpha_{\mathrm{cold}}\,$ runs.
• Figure 2: Top: $g-r$ colour magnitude diagram of SDSS galaxies, coloured by the fraction of galaxies within each cell with SDSS spectroscopy. The contours show the $20, 40, 60,$ and $80$th percentiles of the SDSS spectroscopic sample. Bottom: the $g-r$ colour magnitude diagram of SHARK light-cone galaxies before matching to the SDSS, coloured by the number of galaxies in each cell. The contours show the $20, 40, 60,$ and $80$th percentiles after the spectroscopic selection defined in Section \ref{['sdss-spectro']} (i.e. the Shark$_{\mathrm{spec}}\,$ sample).
• Figure 3: Redshift distribution of SDSS galaxies with spectroscopy (dark blue) and Shark galaxies (in light blue) after our CMD selection explained in Section \ref{['sdss-spectro']}.
• Figure 4: Projected phase space (PPS) distribution of our Shark satellite galaxies, used to estimate infall time in Figure \ref{['fig:QF_P19']}. The 7 different zones correspond to the infall times from Pasquali2019 and adopted by Oxland2024. Zone 7, which has a high interloper fraction in observations, is excluded from our analysis.
• Figure 5: QF of galaxies as a function of time since infall (measured from PPS, see Section \ref{['pps']}), where the QF is weighted by $1/V_{\mathrm{max}}$. The leftmost panel corresponds to low-mass galaxies, while the middle and rightmost panels contain intermediate- and high-mass galaxies, respectively. The top panel contains galaxies in groups, while the bottom shows galaxies in clusters. Different markers and shades of blue correspond Shark runs with different values of $\alpha_{\mathrm{hot}}\,$ and $\alpha_{\mathrm{cold}}\,$ as shown in the legend. The red stars show the observational results of Oxland2024. The error bars correspond to the 68 per cent confidence intervals estimated from the beta distribution Cameron2011. The single points artificially placed at $T_{\mathrm{inf,\:P19}\:}$ = 1.5 Gyr are the field galaxies, and have uncertainties smaller than the marker size. Finally, the black dashed line represents the point at which 50 per cent of galaxies in a given class are quenched. We only show bins with more than 10 galaxies, and exclude galaxies in zone 7 (which have infall times $\lesssim 2.8$ Gyr; see Figure \ref{['fig:pps']}) due to low numbers and a high interloper fraction in observations