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Interferometric studies of individual bright galaxies, e.g., NGC 253, NGC 660,
NGC 1068, NGC 1365, NGC 1808, M82, NGC 3079, NGC 3628, NGC 4945, etc. reveal
HI emission and absorption over about the same velocity range. And
many more galaxies can be added to the sample (see Table 1). It is remarkable
that these are all barred galaxies with high central activity and
far-infrared (FIR) luminosities of a few 1010L
(see Tables 2
and 3), often revealing outflow of gas from the central region. They also
frequently contain megamasers and Seyfert nuclei although the starburst
activity usually dominates the total power output.
Sérsic & Pastoriza (1965) had already noted that galaxies with peculiar nuclei, e.g., NGC 1097, NGC 1365, NGC 1808, and NGC 7552 (most of them containing `hot spots', i.e., extremely bright HII regions), are barred (SB or SAB), strongly indicating a relationship between the nuclei of galaxies and their whole structure. My main aim is to investigate further the nature of this relationship.
To understand the nuclear kinematics in these galaxies -- which are probably very much alike -- sensitive high-resolution HI observations need to be carried out which can at least partly resolve the central continuum. A summary of our high-resolution ATCA observations is given in Section 3. Section 4 contains a literature review of the sample of galaxies described above, including some of our new results, and a comparison with strongly interacting galaxies and others with broad HI absorption lines. As a summary I present a global model in Section 5.
Name | ![]() |
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gradient | Ref. |
[kms-1] | [kms-1] | [kms-1arcsec-1] | ||||
NGC 253 | 75-330 | 255 | 75-400 | 325 | (a) | |
NGC 660 | 640-1050 | 410 | 675-1050 | 375 | 87 | (b) |
NGC 1068 | 760-1300 | 540 | 900-1300 | 400 | (c) | |
NGC 1365 | 1473-1786 | 313 | 1432-1840 | 408 | (d) | |
NGC 1808 | 820-1180 | 360 | 810-1190 | 380 | 13 | (e) |
NGC 3034 | 66-375 | 309 | 50-380 | 330 | (f) | |
NGC 3079 | 840-1420 | 580 | 860-1420 | 560 | 500 | (g) |
NGC 3628 | 650-1080 | 430 | 670-1020 | 350 | 27 | (h) |
NGC 4945 | 380-740 | 360 | 355-750 | 395 | (j) | |
Circinus | 350-550 | 200 | 285-590 | 295 | (k) | |
NGC 6221 | 1300-1650 | 350 | (l) | |||
NGC 7552 | 1500-1700 | 200 | 1460-1760 | 300 | (l) | |
NGC 7582 | 1380-1780 | 400 | 1380-1810 | 430 | (l) |
Column (1): Galaxy name. Columns (2)-(5): The velocity range observed in HI absorption and emission, respectively. Column (6): Lower limit to the velocity gradient of the HI absorption feature, when resolved. Column (7): References. (a) Dickey, Brinks & Puche 1992; (b) Gottesmann & Mahon 1990; Baan, Rhoads & Haschick 1992; (c) Gallimore et al. 1994; Brinks et al. 1995; (d) Jörsäter & van Moorsel 1995; (e) Koribalski, Dickey & Mebold 1993; (f) Weliachew, Fomalont & Greisen 1984; Crutcher, Rogstad & Chu 1978; (g) Irwin & Seaquist 1991; Baan & Irwin 1995; (h) Schmelz, Baan & Haschick 1987; Wilding, Alexander & Green 1993; (j) Ables et al. 1987; (k) Koribalski & Whiteoak 1996; (l) Koribalski, Lavezzi, Dickey & Whiteoak 1996.