5. HII GALAXIES SHOWING ONLY NEBULAR HeII EMISSION

HII regions ("local" or extragalactic objects) and HII galaxies showing nebular HeII 4686 are considered to be quite rare (e.g. Garnett et al. 1991). Although not intended as a complete inventory these authors quote only 17 objects drawn from the studies of dwarf emission-line galaxies by Kunth & Sargent (1983) and Campbell et al. (1986). Many new observations revealing nebular HeII 4686 emission have since been found, mostly in the sample of Izotov and collaborators (see Sect. 2).

In Table 2 we list extragalactic HII regions showing HeII 4686 emission which is entirely attributed to nebular emission processes. In some cases, however, WR signatures are suspected by some authors; see column 8 for references. We restrict ourself to objects from the Terlevich et al. (1991) catalogue analysed by various authors and the sample of Izotov and collaborators, since these constitute the largest available samples of such objects. All except one object (Pox 105) from Kunth & Sargent (1983) showing HeII 4686 emission was later classified as a WR galaxy (Kunth & Joubert 1985 and references in Sect. 3). From the four emission line galaxies with narrow HeII 4686 emission listed by Conti (1991, his Table 2) three are now classified as WR galaxies (see Table 1); the presence of a broad HeII 4686 component due to WR stars is suspected in the Seyfert 2 galaxy Pox 52 (Kunth et al. 1987).

Table 2. List of extragalactic HII regions with nebular HeII.

	R.A.	Decl.	Morphology	mb	Vrad	Nebular HeII 4686	Comment
Name	[1950]	[1950]		[mag]	[km s-1]	reference
SBS 0749+568	07 49 37.7	+56 49 48	BCG	18.0	5471	ITL97
Mrk 1416	09 17 25.9	+52 46 50	Irr	17.0	2305	ITL97
Tol 4	10 08 31.0	-28 39 18	E?	14.4	4219	CTM86	also C96; P99: WR?
SBS 1116+583B	11 16 31.4	+58 20 16		19.5	9905	ITL97
UM 469	11 54 38.6	+02 45 10		18.0	17388	C96
SBS 1159+545	11 59 29.0	+54 32 33	BCG	18.0	3537	ITL94
SBS 1205+557	12 05 57.5	+55 42 07	BCG	15.5	1751	ITL97
Tol 21	12 14 42.0	-27 45 00		17.5	7795	CTM86
Mrk 1318	12 16 36.5	+04 07 58	E pec	14.0	1526	C96	P99: WR?
Fairall 30	12 36 32.0	-39 54 42	SAB(r)0		1199	CTM86
UM 533	12 57 25.0	+02 19 08	dIn	15.7	874	KC98
Pox 105	13 00 00.0	-11 10 00		17.0	3405	KS83,KJ85
Tol 1304-386	13 04 32.0	-38 38 48			4197	CTM86	P99: WR?
Tol 78	13 04 48.0	-35 22 00		17.0	4197	CTM86
Tol 111	13 45 24.0	-42 06 00		16.3	2398	CTM86
SBS 1420+544	14 20 59.1	+54 27 42	BCG	18.0	6176	TIL95
CG 1258	14 41 50.9	+29 28 32		18.0	13614	ITL97
SBS 1533+469	15 33 24.0	+46 59 00			5666	TIL95
HS 1851+6933	18 51 38.6	+69 33 16		17.0	7495	I96
KEY TO REFERENCES. -- C96 Contini 1996, CTM86 Campbell et al. 1986, I96 Izotov et al. 1996, I97c Izotov et al. 1997c, ITL94 Izotov et al. 1994, ITL97 Izotov et al. 1997a, KC98 Kovo & Contini 1998, KJ85 Kunth & Joubert 1985, KS83 Kunth & Sargent 1983, P98 Pindao 1998, P99 Pindao et al. 1999, TIL Thuan et al. 1995

From the 12 objects of Campbell et al. (1986) for which a measurement is available, six remain in this category, although two additional objects are suspected to show broad HeII. In the other objects from Campbell et al., WR features have been found by other investigators (see Sect. 3), in part also in re-analysis of the same observational data (e.g. Masegosa et al. 1991).

From the sample of Izotov and collaborators (including 60 objects published up to 1998, i.e. including Izotov & Thuan 1998), 40 show nebular HeII. However only 9 objects (listed in Table 2) reveal no broad 4686 component according to these studies and the reanalysis of Guseva et al. (1998).