ELVES. III. Environmental Quenching by Milky Way–mass Hosts

Abstract

Isolated dwarf galaxies usually exhibit robust star formation but satellite dwarf galaxies are often devoid of young stars, even in Milky Way–mass groups. Dwarf galaxies thus offer an important laboratory of the environmental processes that cease star formation. We explore the balance of quiescent and star-forming galaxies (quenched fractions) for a sample of ∼400 satellite galaxies around 30 Local Volume hosts from the Exploration of Local VolumE Satellites (ELVES) Survey. We present quenched fractions as a function of satellite stellar mass, projected radius, and host halo mass, to conclude that overall, the quenched fractions are similar to the Milky Way, dropping below 50% at satellite M * ≈ 108 M ⊙. We may see hints that quenching is less efficient at larger radii. Through comparison with the semianalytic modeling code SatGen, we are also able to infer average quenching times as a function of satellite mass in host halo-mass bins. There is a gradual increase in quenching time with satellite stellar mass rather than the abrupt change from rapid to slow quenching that has been inferred for the Milky Way. We also generally infer longer average quenching times than recent hydrodynamical simulations. Our results are consistent with models that suggest a wide range of quenching times are possible via ram pressure stripping, depending on the clumpiness of the circumgalactic medium, the orbits of the satellites, and the degree of earlier preprocessing.

Beyond Ultra-diffuse Galaxies. II. Environmental Quenching of Mass–Size Outliers among the Satellites of Milky Way Analogs

“…The average difference in quenched fractions between the two radial bins is ∼0.1 for UDGs and ∼0.2 for UPGs. This trend agrees with the findings in Greene et al (2023) and for normal satellites in the ELVES survey. From the bottom panels of Figure 5, we find that UDGs (UPGs) hosted by redder hosts also have a higher quenched fraction.…”

“…Using the FIRE-2 simulation, Samuel et al (2022) also showed that the quenched fraction increases as the distance to the host decreases, and hosts with higher CGM mass have more quenched satellites. Such trends are also found in observations (e.g., Greene et al 2023;. In Figure 4, by comparing UDGs and UPGs at two radial bins, we find a very similar trend that satellites that are closer to the host are more quiescent.…”

“…As a sanity check, we select UPGs in the ELVES sample and calculate the quenched fraction, shown as the brown line in the left panel of Figure 6. Out of the 313 ELVES satellites that have secure distances around hosts that are mapped out to R > 200 kpc, there are 27 UPGs (see Greene et al 2023). Despite the number of UPGs in ELVES being small, the quenched fraction of ELVES UPGs agrees with that of our UPG sample (green line) quite well.…”

“…Overall, the SAGA quenched fraction is lower than that of ELVES and the MW. As suggested by Carlsten et al (2022a), the difference in both luminosity function and quenching could be naturally explained if the SAGA sample is preferentially missing ∼1-1.5 satellites per host, and quiescent galaxies are fainter than star-forming ones at a fixed stellar mass (see also Font et al 2022;Greene et al 2023).…”

“…In particular, dwarf galaxies and their star formation history are sensitive to the environments where they reside. Nearly all isolated dwarf galaxies in the field are starforming (Geha et al 2012), but satellite dwarf galaxies in the Local Group and Local Volume hosted by Milky Way (MW)mass galaxies are much more quiescent in star formation, with a near-unity quenched fraction at M å  10 8 M e (e.g., Grcevich & Putman 2009;Spekkens et al 2014;Wetzel et al 2015b;Baxter et al 2021;Mao et al 2021;Putman et al 2021;Carlsten et al 2022a;Greene et al 2023;Karunakaran et al 2022). Such a contrast indicates that environment plays an important role in regulating star formation in dwarf galaxies.…”