Dark matter and H i in ultra-diffuse galaxy UGC 2162

Abstract

<jats:title>ABSTRACT</jats:title> <jats:p>Our GMRT (Giant Metrewave Radio Telescope) H i observations of the ultra-diffuse galaxy (UDG) UGC 2162, projected ∼ 300 kpc from the centre of the M 77 group, reveal it to a have an extended H i disc ($R_{\rm H\,{\small I}}/R_{25}$ ∼ 3.3) with a moderate rotational velocity (Vrot ∼ 31 km s−1). This Vrotis in line with that of dwarf galaxies with similar H i mass. We estimate an Mdyn of ∼1.14 × 109 M⊙ within the galaxy’s $R_ \rm {H\,{\small I}}$ ∼ 5.2 kpc. Additionally, our estimates of M200 for the galaxy from NFW models are in the range of 5.0–8.8 × 1010 M⊙. Comparing UGC 2162 to samples of UDGs with H i detections show it to have amongst the smallest Re with its MH i/M* being distinctly higher and g – icolour slightly bluer than typical values in those samples. We also compared H i and dark matter (DM) halo properties of UGC 2162 with dwarf galaxies in the LITTLE THINGS sample and find its DM halo mass and profile are within the range expected for a dwarf galaxy. While we were unable to determine the origin of the galaxy’s present-day optical form from our study, its normal H i rotation velocity in relation to its H i mass, H i morphology, environment, and dwarf mass DM halo ruled out some of the proposed ultra-diffuse galaxy formation scenarios for this galaxy.</jats:p>

Resolved HI in two ultra-diffuse galaxies from contrasting non-cluster environments

“…Analysis of the DM content of six of the UDGs in the Leisman sample of isolated H i detected UDGs (Mancera Piña et al 2019Piña et al , 2020 indicates that those galaxies are baryon dominated within their R HI , see Figure 4 in Mancera Piña et al (2019), although their results are based on a limited number of bbarolo (Di Teodoro & Fraternali 2015) 3D kinematic tilted-ring disc model fits for each galaxy. A similar, although lower magnitude, departure from the BTFR was reported in Sengupta et al (2019) for the UDG, UGC 2162 also derived from bbarolo fitting. Confirmation of a baryon dominated population of UDGs has important implications for the origin of those UDGs.…”

“…To date only a few UDGs have been mapped in H i (e.g. Leisman et al 2017;Sengupta et al 2019;Mancera Piña et al 2019). Interestingly, several of these UDGs with resolved H i show an apparent departure from the McGaugh et al (2000) baryonic Tully Fisher relation (BTFR).…”

Implications for Galaxy Formation Models from Observations of Globular Clusters around Ultra-Diffuse Galaxies

“…In the "high-spin" model (Amorisco & Loeb 2016), a higher initial halo spin for a dwarf-like halo produces a galaxy with a large effective radius and hence low surface brightness. Again, current observations, in this case H I observations of gas-rich UDGs, provide conflicting results with some finding high-spin (Spekkens & Karunakaran 2018;Liao et al 2019) and others finding low-spin (Jones et al 2018;Sengupta et al 2019) field UDGs. In the high-spin UDGs, the baryons are less concentrated than in the low-spin analogs and so, in addition to the stars being more spread out, a lower star formation efficiency may also plausibly be responsible for the galaxy's low surface brightness.…”

WALLABY pre-pilot survey: Two dark clouds in the vicinity of NGC 1395

“…These HI-dominated systems are often remnants of past tidal (or hydrodynamic) interactions and/or could be more extreme cousins of very low surface brightness galaxies such as the class of HI-rich tidal dwarf galaxies (Bournaud et al 2007;Lelli et al 2015;Lee-Waddell et al 2016;Leisman et al 2016;Sengupta et al 2017) and 'almostdark' galaxies (e.g. Leisman et al 2017;Sengupta et al 2019;Janowiecki et al 2019;Scott et al 2021). Galaxy evolution models have demonstrated that the majority of HI clouds without optical counterparts are likely the result of galaxy-galaxy interactions (e.g.…”