The Local Volume HI Survey (LVHIS)


ESO 115-G021 (HIPASS J0237-61) is a Magellanic barred spiral galaxy at a TRGB distance of 4.99 ± 0.10 Mpc (Tully et al. 2006). Apart from its small HI companion noted below, ESO115-G021 has no known neighbours within 5 degrees. Our ATCA maps show an extended, regular rotating, nearly edge-on HI disc with a diameter of ~15 arcmin, corresponding to 22 kpc. We measure FHI = 110.7 Jy km/s, ~10% higher than quoted in the HIPASS BGC using a point-source fit (Koribalski et al. 2004), and derive MHI = 6.5 × 108 M. The HI velocity field of ESO 115-G021 shows some peculiar motions: (1) a disturbance in the disc area closest to the companion, suggesting mild interactions, and asserting the close proximity of the two galaxies, and (2) a significant twist in the iso-velocity contours towards the south-western (approaching) end of the disc, indicating a warp. Using high-resolution (9 arcsec) ATCA HI maps O'Brien et al. (2010) measure a projected scale height of 26.7 arcsec (646 pc) with vertical HI structures extending to nearly 2 kpc. They measure a rotational velocity of 63 km/s.

Furthermore, our deep ATCA HI observations reveal a dwarf companion, ATCA J023658-611838 at α,δ(J2000) = 02:36:58.8, -61:18:38.5, with a systemic velocity of 508 km/s at a projected distance of 6 arcmin (8.6 kpc) from ESO 115-G021's centre (vsys = 515 ± 2 km/s). The companion's HI flux density is 0.11 Jy km/s, corresponding to an HI mass of 6.5 × 105 M (assuming D = 5 Mpc). A faint GALEX UV counterpart to the HI source is visible at α,δ = 02:36:59.5, -61:18:38.7; we measure FUV and NUV magnitudes of 21.02 and 21.17, corrected for Galactic extinction (NUV−FUV = 0.15). The detected HI source is therefore not an HVC complex. For further discussions see Koribalski (2008) and O'Brien et al. (2010).

Reference: Koribalski et al. 2018 * LVHIS database * LVHIS homepage * next

Last updated on 18 Feb 2018. © Copyright CSIRO