The Local Volume HI Survey (LVHIS)

Centaurus A (NGC 5128)
figure TBD

NGC 5128 (HIPASS J1324-42) is a nearby radio galaxy (DTRGB = 3.77 ± 0.38 Mpc; Rejkuba 2004) with two giant lobes spanning ~8 degrees on the sky (ie., ~0.5 Mpc). It is the dominant elliptical galaxy in the Cen A / M 83 galaxy group, which is known to contain ~100 members. The bright and extended 20-cm radio continuum emission provides some technical challenges for accurate HI measurements which are further complicated by the presence of both HI emission and absorption over a wide velocity range (see Koribalski et al. 2004).

Cen A's optical appearance is that of a giant elliptical surrounded by a prominent band of highly opaque dust, which matches the HI disc detected with the ATCA. Struve et al. (2010) measure FHI = 144 Jy km/s, somewhat more than obtained by van Gorkom et al. (1990), and derive MHI = 4.9 × 108 M. For a comparison with Parkes FHI measurements see the discussion in Koribalski et al. (2004; their Section 3.6). Struve et al. (2010) obtain an HI extent of 814 arcsec or 15 kpc and find a regular rotating, highly warped disc. Further HI emission is detected in the outer disc, somewhat aligned with the faint optical shells of Cen A and likely the result of gas accretion in a recent merger event. Schiminovich et al. (1994) also find HI emission associated with the diffuse shells of NGC 5128 and measure FHI = 208 Jy km/s. Parkes HI spectra obtained by Gardner & Whiteoak (1976) shows emission from ~250 to 850 km/s. Using HIPASS we estimate an HI mass of at least 6 × 108 M.

Furthermore, we detect HI emission east and west of Cen A (sources A, B and C in Fig. 14) without stellar counterparts. These could either be very faint dwarf galaxies near Cen A or another set of HI shells. Their α,δ(J2000) positions and HI properties are as follows. Source A: 13:28:39.9, -42:56:56.5 (~349 − 507 km/s, 35.4 arcmin east of Cen A, FHI = 7.9 ± 1.1 Jy km/s; slightly elongated N−S); source B: 13:23:46.2, -43:06:19.9 (~257 − 414 km/s, 19.2 arcmin west of Cen A, unresolved in HIPASS), and source C: 13:21:16.9, -42:45:24.1 (~507 − 534 km/s, 48.5 arcmin east of Cen A, elongated NW−SE in HIPASS. GALEX UV images do not reveal any counterparts.

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

Last updated on 18 Feb 2018. © Copyright CSIRO