The Local Volume HI Survey

NGC 7793 (HIPASS J2357-32) is a bright spiral galaxy in the Sculptor group at a TRGB distance of 3.91 ± 0.41 Mpc (Karachentsev et al. 2003). We use the low-resolution ATCA 16-pointing mosaic data of NGC 7793 and its surroundings to obtain HI maps of NGC 7793. The ATCA HI distribution extends beyond the previously published single-pointing VLA maps (Carignan & Puche 1990; Walter et al. 2008). We measure D_HI = 16.5 arcmin and FHI = 292.6 Jy km/s, in agreement with the HIPASS BGC FHI of 278.5 ± 20.4 Jy km/s (Koribalski et al. 2004). For comparison, Walter et al. (2008) measure FHI = 246 Jy km/s with the VLA, missing HI gas mainly in the extended outer disc. Our mean HI velocity field shows that the position angle of NGC 7793's outer disc (PA = 300 degr) is much larger than that of its stellar disc (PA = 278 degr), suggesting a significant warp. This is also supported by the closed velocity contours. Carignan & Puche (1990) also notice the PA change. They determine the rotation curve out to a radius of 7.5 arcmin (see also de Blok et al. 2008). Significant uncertainties remain about the inclination angle change in the outer disc, affecting the shape of the rotation curve. Combining the ATCA and VLA HI data would be of significant benefit for studying the outer disc gas distribution and kinematics (see also Radburn-Smith et al. 2012, 2014). NGC 7793 has two dwarf companions, ESO 349-G031 and UGCA 442, located at projected distances of ~3 degr.

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