Baryonic Masses and Properties of Gaseous Satellite Galaxies

TL;DR

This study presents a census of 127 gas-bearing dwarf satellites around 56 nearby late-type hosts within 30 Mpc using HI data from WALLABY, MHONGOOSE, and ALFALFA, deriving baryonic masses ($ ext{log}(M_{ m HI}/M_\odot)=5.7-9.7$, $ ext{log}(M_*/M_\odot)=5.6-10.0$) and analyzing environmental effects on gas content. By injecting model dwarfs into host cubes, the authors quantify HI sensitivities (e.g., $ ext{log} M_{ m HI,lim} ightarrow 7.1$ for WALLABY and $ ightarrow 5.5$ for MHONGOOSE at 10 Mpc) and construct a robust, cross-survey satellite sample with careful host-halo modeling via SMHM relations. They find a low abundance of gaseous satellites that increases with host mass, with significant gas depletion in satellites of MW-like halos, and they show consistency with MW/M31 and deep optical surveys in terms of star-forming satellite counts and quenched fractions. The results support an effective environmental quenching framework driven by gas stripping processes and provide a baseline for interpreting satellite populations across environments, informing future HI surveys and simulations.

Abstract

We present a sample of 127 gas-bearing dwarf galaxies around 56 late-type host galaxies within 30 Mpc using 21-cm HI data from the WALLABY, MHONGOOSE, and ALFALFA surveys. We characterize the environment of each dwarf galaxy based on its host galaxy halo and derive optical properties using the DESI Legacy Surveys for 110. The gaseous satellites span $\log (M_{\rm HI}/M_{\odot}) = 5.7-9.7$ and $\log (M_{\star}/M_{\odot}) = 5.6-10.0$, with a median velocity line-width of $W_{50}=37$ km/s, comparable to the Local Group gaseous dwarf galaxies. We assess the HI mass sensitivity of the data by injecting model dwarf galaxies and find $M_{\rm HI,lim} = 10^{6.7} M_{\odot}$ for WALLABY and $M_{\rm HI,lim} = 10^{5.4} M_{\odot}$ for MHONGOOSE at 10 Mpc. With this sensitivity, our sample shows lower average gas-to-stellar mass ratios ($M_{\rm HI}/M_{\star}$) than literature dwarf galaxy samples. The abundance of gaseous satellites per host is low and increases with host mass: $0-2$ for isolated dwarf galaxy hosts and $0-5$ for Milky Way-mass spiral hosts. These numbers are consistent with the Milky Way, M31, and star-forming satellite abundances from recent deep optical surveys. The inferred quenched fractions and gas-depleted satellites indicate that environmental quenching is effective in Milky Way-mass hosts, likely driven by gas stripping processes.

Figures (14)

• Figure 1: Summary of the nearby H i-bearing host galaxies in this study. Data points show the distances versus halo masses of the host galaxies (Table \ref{['table:hosts']}), and in parentheses the host count from the survey: WALLABY pilot (stars; westmeier_wallaby_2022murugeshan_wallaby_2024), MHONGOOSE (pentagons; de_blok_mhongoose_2024), and ALFALFA from zhu_census_2023 (small circles; H i data from haynes_arecibo_2018). Colors show the fractional halo coverage ($R_{\rm cover}/R_{200}$; see Section \ref{['subsec:host_sample']}). We excluded three MHONGOOSE hosts with the lowest projected halo coverages ($R_{\rm cover}/R_{200}<0.7$; see the red crosses), which are intermediate-mass spirals with no gaseous satellites in their covered inner halos (NGC 625, NGC 7793, and NGC 5068).
• Figure 2: The H i sensitivity limits across different surveys. For WALLABY and MHONGOOSE, the scatter points show the 25%, 50%, and 90% detectability thresholds from the dwarf injection tests (Appendix \ref{['subsubsec:injection_in_sensitivity_test']}). The lines (shaded regions) show the sensitivity in equation \ref{['eqn:mhi_sensitivity_compre']} at the best-fit SNRs at $W_{50}=25$ ($15-35$) km/s. For ALFALFA, we report the same information from the empirical sensitivity estimations in haynes_arecibo_2011; see Section \ref{['subsubsec:injection_in_sensitivity_test']} for details. The right-hand y-axis converts sensitivities to completeness levels relative to the gas-rich dwarf galaxies in the Local Group (LG; putman_gas_2021), showing the percentile of LG galaxies more massive than the corresponding $M_{\rm H\,\textsc{i}}$ value on the left.
• Figure 3: The spatial (projected distance, $d_{\rm proj}$) and kinematic (line-of-sight velocity, $\Delta V_{\rm los}$) separations between the gaseous dwarf galaxies and their host galaxies. Left-hand panel: $d_{\rm proj}$ and $\Delta V_{\rm los}$ are in physical units as listed in Table \ref{['table:sats']}; different symbols distinguish the H i data sources used in this work (Section \ref{['sec:data']}). Right-hand panel: same as the left, but the separations are scaled by the host $R_{200}$ and $V_{\rm esc}$ (Section \ref{['subsec:host_sample']}). We show the point-mass escape velocity curves in blue, where the dashed lines denote our satellite-unbound classification (equation \ref{['eqn:grav_bound_observable']}; taking $R_{V}, R_{d}=1$) and shaded regions show a range under projection effects; see Section \ref{['subsec:method_sat_environment']}. Filled symbols in both panels highlight the "close" satellite candidates within host projected $R_{200}$.
• Figure 4: The H i mass ($M_{\rm H\,\textsc{i}}$) versus velocity line-width ($W_{50}$) distribution for the gaseous dwarf sample (Table \ref{['table:sats']}). Scatter points in the central panels represent individual H i-emitting dwarf galaxies; histograms in the corner panels show the marginal distribution. Left panel: colored symbols distinguish the H i surveys used in this work (Section \ref{['sec:data']}). Colored shadings in the central and right-hand ($M_{\rm H\,\textsc{i}}$ marginal) panels present the H i mass sensitivities of the three subsamples; see § \ref{['subsec:sat_hi_properties']}. Right panel: similar to the left, here showing our gaseous dwarf sample (circles; combining three surveys) and the Local Group gaseous dwarf population (light red diamond symbols; putman_gas_2021) in the central panel. Close satellites within the host galaxies' projected $R_{200}$ are shown with filled symbols as in Figure \ref{['fig:sat_kinematic_distribution']}, or shaded histograms in the marginal panels.
• Figure 5: The H i versus stellar mass distribution of the gaseous dwarf sample (Table \ref{['table:sats']}), showing survey H i sensitivities (left) and dwarf galaxy environment, in the same style as Figure \ref{['fig:sat_HI_mass_width']}). Left panel: colored symbols indicate the three H i surveys, with average H i sensitivities shaded as in Figure \ref{['fig:sat_HI_mass_width']}. Error bars show the binned means and standard deviations of $\log M_{\rm H\,\textsc{i}}$ at $\log M_{\star}/M_{\odot}=[6.75, 7.75, 8.75]$ for the full sample (gray dashed lines; also shown in the right panel) and the deep subsample above median sensitivity (orange dashed-dotted lines); see § \ref{['subsec:sat_gas_star_properties']}. Right panel: shadings indicate the position-velocity separation from the host (§ \ref{['subsec:method_sat_environment']}): dark gray for satellite candidates within $R_{200}$, light gray for objects outside $R_{200}$ but bound, and open symbols for unbound nearby galaxies. The Local Group gas-rich population ($M_{\rm H\,\textsc{i}}$ from putman_gas_2021; $M_{\star}$ from pace_local_2024) are shown in light red for comparison.