NGC 253 (HIPASS J0047-25)
is a well-known starburst spiral galaxy and the brightest member
of the Sculptor Group. It is oriented close to edge-on with an optical extent
of 32 arcmin × 8 arcmin and ~50 arcmin × 30 arcmin at ~28 mag
arcsec-2 (Malin & Hadley 1997). We have
adopted a TRGB distance of 3.94 ± 0.37 Mpc (Karachentsev et al. 2003).
Our ATCA data show bright HI emission extending barely beyond the stellar disc
and HI absorption (visible as the central hole) against the prominent starburst
region. The mean HI velocity field highlights the fast rotating disc
(vrot = 213 km/s) with only minor deviations from regular rotation
in its outskirts. The brightest HI emission is detected in the barred region
of NGC 253.
Previous ATCA HI observations of NGC 253 were presented by Koribalski,
Whiteoak & Houghton (1995) and Boomsma et al. (2005). Lucero et al. (2015)
use the Karoo Array Telescope (KAT-7) to map the extended HI structure of
NGC 253 at low resolution (~3.5) down to column densities of NHI
= 1.3 × 1019 cm-2. They measure FHI
= 728 ± 36 Jy km/s, in agreement with the HIPASS FHI of
692.9 ± 42.2 Jy km/s (Koribalski et al. 2004). Both are lower limits
due to significant HI absorption against the bright star-forming inner region
of NGC 253, which covers the same velocity range as the HI emission
(Koribalski, Whiteoak & Houghton 1995). Using our ATCA HI maps we measure
FHI = 746.8 Jy km/s and derive MHI = 2.7 ×
109 M☉. Using 3D FAT Wang et al. (2017) obtained
an HI rotation curve indicating vrot = 200 km/s at Rmax
= 17.2 kpc and Mdyn = 1.6 × 1011
M☉.
The large spiral galaxies NGC 247 and
NGC 253, together with the dwarf galaxies ESO 540-G030,
ESO 540-G031 and ESO 540-G032 form another small association
(D ~ 4 Mpc) within the Sculptor Group. The three faint dwarf galaxies are not
part of the LVHIS Galaxy Atlas presented here. Karachentsev et al. (2003)
obtained TRGB distances of 3.40 ± 0.34 Mpc (ESO 540-G030), 3.34 ±
0.24 Mpc (ESO 540-G031), and 3.42 ± 0.27 Mpc (ESO 540-G032), suggesting
that this dwarf grouping lies slightly in front of the spiral galaxy
NGC 247.
Reference:
Koribalski et al. 2018
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