H i properties of satellite galaxies around local volume hosts

Abstract

We present neutral atomic hydrogen (H i) observations using the Robert C. Byrd Green Bank Telescope (GBT) along the lines of sight to 49 confirmed or possible dwarf satellite galaxies around eight Local Volume systems (M104, M51, NGC 1023, NGC 1156, NGC 2903, NGC 4258, NGC 4565, NGC 4631). We detect the H i reservoirs of two candidates (dw0934+2204 and dw1238−1122) and find them to be background sources relative to their nearest foreground host systems. The remaining 47 satellite candidates are not detected in H i, and we place stringent 5σ upper limits on their H i mass. We note that some (15/47) of our non-detections stem from satellites being occluded by their putative host’s H i emission. In addition to these new observations, we compile literature estimates on the H i mass for an additional 17 satellites. We compare the H i properties of these satellites to those within the Local Group, finding broad agreement between them. Crucially, these observations probe a ‘transition’ region between −10 ≳ MV ≳ −14 where we see a mixture of gas-rich and gas-poor satellites. While there are many gas-poor satellites within this region, some are gas-rich and this suggests that the transition towards predominantly gas-rich satellites occurs at LV ∼ 107L⊙, in line with simulations. The observations presented here are a key step toward characterizing the properties of dwarf satellite galaxies around Local Volume systems and future wide-field radio surveys with higher angular resolution (e.g. WALLABY) will vastly improve upon the study of such systems.

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

“…We can go beyond C22 and use both archival Hα and published H I measurements to support further the fidelity of the early/late-type demarcation. Karunakaran et al (2022a) find that within this archival sample, all the H I detected galaxies are classified as late type by C22. Turning to Hα, we use the catalog of Karachentsev et al (2021).…”

“…In ELVES, none of these ideal tracers are available for the full sample. Karunakaran et al (2022a; see also Karunakaran et al 2020) presents some archival and some new H I constraints to ELVES, but they are not comprehensive. Many galaxies in ELVES have archival Galaxy Evolution Explorer (GALEX) and/or Hα measurements, but by no means all.…”

“…Note the distinct tilt toward bluer colors for lower-mass galaxies. The galaxies that Karunakaran et al (2022a) would label as star forming based on their NUV luminosities are indicated with the black dots, showing again that nearly every morphologically early-type satellite with M * < 10 7 M e is considered star forming by this criterion. As argued in the text, given the star formation histories that do exist for these galaxies, this metric for star formation seems overly inclusive.…”

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

“…The best-fit NFW concentration is consistent with an MW-mass halo, whereas the best-fit Einasto profiles have a smaller concentration than MW-mass halos. Karunakaran et al 2022;Zhu & Putman 2023) and derive the quiescent fraction. However, due to the low surface brightness and low-luminosity nature of our mass-size outliers, obtaining such measurements is extremely expensive over the full footprint of our sample.…”

“…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.…”