The Local Volume HI Survey

NGC 4945 (HIPASS J1305-49) is a well-known starburst spriral galaxy (type SBcd) in the Cen A group. It is oriented close to edge-on, highly obscured in the optical and located at a TRGB distance of 3.80 Mpc (Mould & Sakai 2008). Its nearest neighbours are ESO 269-G058 (157.1 arcmin), ES0 269-G?066 (285.1 arcmin; v_hel = 784 km/s) and NGC 5206 (290.2 arcmin); projected distances are given in brackets. About 7 arcmin north-west of the centre of NGC 4945 lies a faint galaxy, sometimes known as CEN05, but identified to be a distant spiral galaxy by Bouchard et al. (2004). Early ATCA HI maps of NGC 4945 were published by Ott et al. (2001). They also map the extended 20-cm radio continuum emission of NGC 4945 and estimate a flux density of 4.2 ± 0.1 Jy over the central source. Consequently, HI absorption dominates in the galaxy core, extending over ±200 km/s with respect to the systemic velocity. This is similar to the velocity range of the main HI emission. Here we present HI results from new ATCA mosaic observations in the EW367 and 750A arrays. The overall impression is that of a large, symmetric, regularly rotating HI disc, which does not extend much beyond the bright stellar disc.

Using 3D FAT Kamphuis et al. (2015) obtain an HI rotation curve indicating v_rot = 173.6 km/s at R_max = 16.7 kpc (for i = 82.8 degr and PA = 44.2 degr; and M_dyn = 1.2 × 10¹¹ M_☉. NGC 4945 has the highest rotational velocity in our sample. A peculiar HI feature is seen towards the south, possibly extraplanar gas lagging behind. Combining all the available ATCA HI data will allow a much more detailed analysis. Using our low-resolution ATCA mosaic we measure F_HI = 405.3 Jy km/s and derive M_HI = 1.4 × 10⁹ M_☉. This is ~20% higher than the HIPASS F_HI, which is significantly affected by HI absorption (Koribalski et al. 2004).

Bouchard et al. (2007) obtained HI observations for 18 dwarf galaxies in the Cen A Group. They detect five galaxies (ESO 269-G037, CEN06, UGCA 365, ESO 384-G016 and ESO 272-G025) with the ATCA and quote upper limits for the remaining galaxies. For the dE galaxy ESO 269-G?066 (KK 190; D_TRGB = 3.82 ± 0.26 Mpc; Karachentsev et al. 2007), which was observed with the 64-m Parkes telescope for over 10 h, Bouchard et al. (2007) give an upper limit of F_HI = 0.026 Jy km/s. This corresponds to an M_HI limit of ~9 × 10⁴ M_☉. In the vicinity is also the dwarf galaxy ESO 269-G037 (type dSph or dIrr). Using ATCA HI observations Bouchard et al. (2007) find v_hel = 744 km/s and F_HI = 0.14 ± 0.02 Jy km/s. The latter corresponds to an HI mass of only 4 × 10⁵ M_☉ for D_TRGB = 3.48 ± 0.35 Mpc (Karachentsev et al. 2002).

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