The Local Volume HI Survey

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 (v_rot = 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 N_HI = 1.3 × 10¹⁹ cm^-2. They measure F_HI = 728 ± 36 Jy km/s, in agreement with the HIPASS F_HI 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 F_HI = 746.8 Jy km/s and derive M_HI = 2.7 × 10⁹ M_☉. Using 3D FAT Wang et al. (2017) obtained an HI rotation curve indicating v_rot = 200 km/s at R_max = 17.2 kpc and M_dyn = 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 * LVHIS database * LVHIS homepage * next