ESO115-G021
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
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