HI in small elliptical galaxies

It has been known for more than a decade that many small elliptical galaxies contain HI. Lake & Schommer (1984) detected eleven (39%) of a sample of 28 low-luminosity elliptical galaxies observed at Arecibo, and suggested that HI was common in these galaxies.

Phillips et al. (1986) found that 5/18 (28%) of the low-luminosity (M fainter than -18) elliptical and S0 galaxies in their optical emission-line survey had optical spectra characteristic of HII regions. Since these galaxies are currently forming massive stars, they must contain reasonable amounts of cold gas. Parkes HI observations of four of the Phillips et al. (1986) `star-forming ellipticals' (Sadler & Whiteoak, unpublished) detected all of them, with typical HI masses of a few times 10 M.

In summary, the rather sparse data available so far suggest that at least 30% of `small' elliptical galaxies contain detectable amounts of HI. If so, small HI-rich elliptical galaxies are common objects. They are nevertheless surprisingly hard to find optically, since on photographic plates they are indistinguishable from more distant and luminous giant ellipticals.

б© Copyright Astronomical Society of Australia 1997