The intriguing H i gas in NGC 5253: an infall of a diffuse, low-metallicity H i cloud?★

Abstract

We present new, deep H i line and 20‐cm radio‐continuum data of the very puzzling blue compact dwarf galaxy NGC 5253, obtained with the Australia Telescope Compact Array as part of the ‘Local Volume H i Survey’ (LVHIS). Our low‐resolution H i maps show, for the first time, the disturbed H i morphology that NGC 5253 possesses, including tails, plumes and detached H i clouds. The high‐resolution map reveals an H i plume at the SE and an H i structure at the NW that surrounds an Hα shell. This latter structure is related to an expanding bubble in the interstellar medium (ISM), but it will almost certainly not originate a galactic wind. We confirm that the kinematics of the neutral gas in NGC 5253 are highly perturbed and do not follow a rotation pattern. We discuss the outflow and infall scenarios to explain such disturbed kinematics, analyse the environment in which NGC 5253 resides and compare its properties with those observed in similar star‐forming dwarf galaxies. The radio‐continuum emission of NGC 5253 is resolved and associated with the intense star‐forming region located at the centre of the galaxy. We complete the analysis using multiwavelength data extracted from the literature, which include X‐ray, Galaxy Evolution Explorer (GALEX) far‐ultraviolet, optical B and R band and Hα, near‐infrared H band, and far‐infrared data. We estimate the star formation rate using this multiwavelength approach, and compare the results with other galaxy properties. NGC 5253 does not satisfy the Schmidt–Kennicutt law of star formation, has a very low H i mass‐to‐light ratio when comparing with its stellar mass and seems to be slightly metal‐deficient in comparison with starbursts of similar baryonic mass. Taking into account all available multiwavelength data, we conclude that NGC 5253 is probably experiencing the infall of a diffuse, low‐metallicity H i cloud along the minor axis of the galaxy. The infall of this independent H i cloud is comprising the ISM and triggering the powerful starburst we see in NGC 5253. The tidally disturbed material observed at the east and north of the galaxy is a consequence of this interaction, which probably started more than 100 Myr ago. The origin of this H i cloud may be related with a strong interaction between NGC 5253 and the late‐type spiral galaxy M83 in the past.

The Brightest Young Star Clusters in NGC 5253

“…M83 is located at a distance of 4.5 Mpc (Thim et al 2003) and is 1°54 ′ to the NW of NGC 5253; thus, M83 is separated from NGC 5253 (at a distance of 3.15 Mpc Freedman et al 2001;Davidge 2007) by about 1.35 Mpc. Although the distance is significant, and although Karachentsev et al (2007) place NGC 5253 in the neighboring Cen A subgroup, Lopez-Sanchez et al (2012) argue that NGC 5253 is located at the boundary between the two subgroups of Cen A and M83. 36 A past interaction with the latter galaxy could explain the tidal extension in HI to the SE of M83 and the extension to the North of the HI distribution in NGC 5253.…”

Star formation sustained by gas accretion

“…The survey LITTLE THINGS finds BCDs with kinematically separate components, streamers extending far beyond the optical size, kinematic HI axes offset from the optical axes, clouds associated with recent starbursts, and so on (Johnson et al 2012;Ashley et al 2013). Many other examples of HI maps showing galaxies with plumes and filaments can be found in the literature (e.g., López-Sánchez et al 2012). Morphological distortions suggestive of gas accretion are also common in optical images and are discussed in Sect.…”

The Sami Galaxy Survey: Galaxy Interactions and Kinematic Anomalies in Abell 119

“…A recent study by Bloom et al (2016) shows that morphologically disturbed galaxies correlate with asymmetry in gas kinematics better than "stellar" (i.e., photometric) parameters, such as Gini (Abraham et al 2003), M20 (Lotz et al 2004), or CAS (Abraham et al 1996;Conselice 2003). The distribution of gas is more easily disturbed than that of stars, making gas an efficient tracer of kinematic disturbances (Stil & Israel 2002;Cannon et al 2004;Koribalski & López-Sánchez 2009;López-Sánchez et al 2012). Gas, however, cannot be used for gasdeficient early-type galaxies.…”