The southern sample consists of five dwarf galaxies from the Centaurus A (NGC 5128, Cen A) group, four dwarf galaxies from the Sculptor (Scl) group, one dwarf in the Antlia-Sextans group, and seven dwarf galaxies in the Local Group and in the field. In particular, IC 1613, IC 5152, NGC 2915, and NGC 3109 were chosen because oxygen abundances in the literature were derived from measurements using obsolete technology or abundances were not well measured. Two galaxies (A0355-465, IC 2032) in the field were selected from the list compiled by Karachentseva & Karachentsev (1998), and two galaxies (ESO358-G060, ESO302-G014) were selected from the Feitzinger & Galinski (1985) catalog. ESO358-G060 is a member of the Fornax Cluster; see Sect. 6.1.10 for additional details.

Because half of the galaxies are members of two nearby groups of galaxies, a brief summary of prior spectroscopy is mentioned here. The Centaurus A group and the Sculptor group are each at a distance of $\la$ 5 Mpc. Webster & Smith (1983) and Webster et al. (1983) obtained oxygen abundances for southern irregular and spiral galaxies, including galaxies in the Cen A group and in the field, with a measured range of abundances from about ten to sixty per cent of the solar value. Miller (1996) carried out H $\alpha$ imaging of eight Sculptor group dwarfs; only two contained detectable H II regions. Subsequent H II region spectroscopy of these two dwarfs showed that their oxygen abundances were roughly 0.1 of the solar value, although the temperature-sensitive [O III] $\lambda 4363$ emission line (see Sect. 5) was not detected in either galaxy. Hidalgo-Gámez et al. (2001) measured [O III] $\lambda 4363$ in the low surface brightness dI ESO245-G005 in the Scl group. [O III] $\lambda 4363$ was detected in two H II regions; however, the two resulting oxygen abundances differ by 0.21 dex, which may be evidence of an abundance gradient. This is similar to the gradient ( $\approx$ 0.2 dex kpc^-1) from spectra of seven H II regions for the same galaxy measured by Miller (1996), although he determined oxygen abundances using the indirect or bright-line method (see Sect. 5.2).

Properties of galaxies in the southern sample are listed in Table 1. Galaxies with probable Local Group membership are listed in Grebel (1999,2000), and Grebel et al. (2003). Compilations of oxygen abundances for nearby dwarf irregulars are found in, e.g., Mateo (1998), Pilyugin (2001b), and Lee et al. (2003a). Comments about individual galaxies from the southern sample will be addressed in Sect. 6.1.

Table 1: Basic properties of galaxies in the southern sample. Galaxies are grouped by association to a group (or otherwise) and are listed in alphabetical order within each category. All properties are obtained from NED, unless otherwise noted. Columns (1) and (2): Galaxy name used in the present work; other names. Column (3): Membership. Column (4): Classification type. Column (5): Heliocentric velocity. Column (6): Total apparent B magnitude. Column (7): Total H I 21-cm flux. Rotational velocities in H I have been measured for A1243-335, A1334-277, DDO 161, IC 1613, and UGCA 442 (Hoffman et al. 1996; Côté et al. 2000); a rotation curve in H $\alpha$ for ESO358-G060 has been measured by Matthews & Gallagher (2002). Column (8): Total H I mass to blue luminosity ratio. Column (9): Measured or estimated distances. Centaurus A group galaxies: Karachentsev et al. (2002b), except DDO 161 (Côté et al. 2000). Sculptor group galaxies: Côté et al. (2000), except UGCA 442 (Karachentsev et al. 2003b). Other southern galaxies: ESO358-G060 - Mould et al. (2000); IC 1613 - Dolphin et al. (2001b); IC 2032 - Carrasco et al. (2001); NGC 2915 - Karachentsev et al. (2003a); NGC 3109, Sag DIG, and IC 5152 - Karachentsev et al. (2002c). NOTES: ^a From Côté et al. (1997). ^b From Longmore et al. (1982). ^c Velocity estimated from spectrum (Sect. 6.1). ^d From Barnes et al. (1997). ^e Member of Fornax Cluster Catalog (FCC; Ferguson 1989). ^f From Schröder et al. (2001); see also Matthews et al. (1998). ^g From Hoffman et al. (1996). ^h From Huchtmeier et al. (2000a). ⁱ From Huchtmeier & Richter (1986). ^j From Meurer et al. (1996). ^k Common group of dwarfs including NGC 3109, Sextans A, Sextans B, and the Antlia dwarf (van den Bergh 1999; Tully et al. 2002). ^l From Barnes & de Blok (2001). ^m From Lee & Kim (2000). ⁿ From Young & Lo (1997).
Galaxy Other Member Type $v_{\odot}$ B_T F₂₁ $M_{\rm HI}/L_B$ D

Name(s) (km s^-1) (mag) (Jy km s^-1) $(M_{\odot}/L_{{\odot},B})$ (Mpc)

(1) (2) (3) (4) (5) (6) (7) (8) (9)

Centaurus A group dwarfs

A1243-335 ESO381-G020, AM1243-333 Cen A IB(s)m +585 14.24 31.9 ^a 1.85 3.63

A1324-412 ESO324-G024, AM1324-411 Cen A IAB(s)m: +513 12.91 52.1 ^a 0.75 3.73

A1334-277 ESO444-G084, AM1334-274 Cen A Im +587 15.01 19.6 ^a 2.29 4.61

A1346-358 ESO383-G087, AM1346-354 Cen A SB(s)dm +326 11.00 27.4 ^a 0.08 3.63

DDO 161 UGCA 320, A1300-17 Cen A IB(s)m sp +744 13.52 110.1 ^a 3.10 5.25

NGC 5264 DDO 242, UGCA 370 Cen A IB(s)m +478 12.60 13.7 ^a 0.19 4.53

Sculptor group dwarfs

AM0106-382 ... Scl dwarf Im +645 16.26 <2.8 ^a <1.29 3.0

ESO347-G017 PGC071466 Scl SB(s)m: +659 14.19 10.5 ^a 0.71 3.0

ESO348-G009 A2346-380, AM2346-380 Scl IBm +657 13.60 ^b 8.4 ^a 0.33 3.0

UGCA 442 ESO471-G006, AM2341-321 Scl SB(s)m: +267 13.60 54.3 ^a 2.12 4.27

Other southern dwarfs

A0355-465 ESO249-G032, AM0355-463 field IB(s)m pec +1168 ^c 16.35 <0.20 ^b <0.10 15.6

ESO302-G014 AM0349-383 field Im pec +881 14.84 4.41 ^d 0.56 ...

ESO358-G060 FCC 302 ^e Fornax Cluster IB(s)m: +803 15.86 12.27 ^f 3.97 20.0

IC 1613 DDO 8, UGC 668 Local Group IB(s)m -234 9.88 698 ^g 0.89 0.73

IC 2032 ESO156-G042, AM0405-552 Dorado IAB(s)m pec: +1066 ^h 14.78 2.87 ^h 0.35 17.2

IC 5152 ESO237-G027, AM2159-513 field IA(s)m +124 11.03 98.0 ⁱ 0.35 2.07

NGC 2915 ESO037-G003, AM0926-762 field I0; BCD? +468 12.93 145 ^j 1.10 3.78

NGC 3109 DDO 236, UGCA 194 Antlia-Sextans ^k SB(s)m +404 10.26 1110 ^l 1.64 1.33

Sag DIG ESO594-G004 Local Group IB(s)m -77 13.99 ^m 32.6 ⁿ 1.21 1.11

**Table 1:** Basic properties of galaxies in the southern sample. Galaxies are grouped by association to a group (or otherwise) and are listed in alphabetical order within each category. All properties are obtained from NED, unless otherwise noted. Columns (1) and (2): Galaxy name used in the present work; other names. Column (3): Membership. Column (4): Classification type. Column (5): Heliocentric velocity. Column (6): Total apparent B magnitude. Column (7): Total H I 21-cm flux. Rotational velocities in H I have been measured for A1243-335, A1334-277, DDO 161, IC 1613, and UGCA 442 (Hoffman et al. 1996; Côté et al. 2000); a rotation curve in H $\alpha$ for ESO358-G060 has been measured by Matthews & Gallagher (2002). Column (8): Total H I mass to blue luminosity ratio. Column (9): Measured or estimated distances. Centaurus A group galaxies: Karachentsev et al. (2002b), except DDO 161 (Côté et al. 2000). Sculptor group galaxies: Côté et al. (2000), except UGCA 442 (Karachentsev et al. 2003b). Other southern galaxies: ESO358-G060 - Mould et al. (2000); IC 1613 - Dolphin et al. (2001b); IC 2032 - Carrasco et al. (2001); NGC 2915 - Karachentsev et al. (2003a); NGC 3109, Sag DIG, and IC 5152 - Karachentsev et al. (2002c). NOTES: ^a From Côté et al. (1997). ^b From Longmore et al. (1982). ^c Velocity estimated from spectrum (Sect. 6.1). ^d From Barnes et al. (1997). ^e Member of Fornax Cluster Catalog (FCC; Ferguson 1989). ^f From Schröder et al. (2001); see also Matthews et al. (1998). ^g From Hoffman et al. (1996). ^h From Huchtmeier et al. (2000a). ⁱ From Huchtmeier & Richter (1986). ^j From Meurer et al. (1996). ^k Common group of dwarfs including NGC 3109, Sextans A, Sextans B, and the Antlia dwarf (van den Bergh 1999; Tully et al. 2002). ^l From Barnes & de Blok (2001). ^m From Lee & Kim (2000). ⁿ From Young & Lo (1997).
Galaxy	Other	Member	Type	$v_{\odot}$	B_T	F₂₁	$M_{\rm HI}/L_B$	D
	Name(s)			(km s^-1)	(mag)	(Jy km s^-1)	$(M_{\odot}/L_{{\odot},B})$	(Mpc)
(1)	(2)	(3)	(4)	(5)	(6)	(7)	(8)	(9)
Centaurus A group dwarfs
A1243-335	ESO381-G020, AM1243-333	Cen A	IB(s)m	+585	14.24	31.9 ^a	1.85	3.63
A1324-412	ESO324-G024, AM1324-411	Cen A	IAB(s)m:	+513	12.91	52.1 ^a	0.75	3.73
A1334-277	ESO444-G084, AM1334-274	Cen A	Im	+587	15.01	19.6 ^a	2.29	4.61
A1346-358	ESO383-G087, AM1346-354	Cen A	SB(s)dm	+326	11.00	27.4 ^a	0.08	3.63
DDO 161	UGCA 320, A1300-17	Cen A	IB(s)m sp	+744	13.52	110.1 ^a	3.10	5.25
NGC 5264	DDO 242, UGCA 370	Cen A	IB(s)m	+478	12.60	13.7 ^a	0.19	4.53
Sculptor group dwarfs
AM0106-382	...	Scl	dwarf Im	+645	16.26	<2.8 ^a	<1.29	3.0
ESO347-G017	PGC071466	Scl	SB(s)m:	+659	14.19	10.5 ^a	0.71	3.0
ESO348-G009	A2346-380, AM2346-380	Scl	IBm	+657	13.60 ^b	8.4 ^a	0.33	3.0
UGCA 442	ESO471-G006, AM2341-321	Scl	SB(s)m:	+267	13.60	54.3 ^a	2.12	4.27
Other southern dwarfs
A0355-465	ESO249-G032, AM0355-463	field	IB(s)m pec	+1168 ^c	16.35	<0.20 ^b	<0.10	15.6
ESO302-G014	AM0349-383	field	Im pec	+881	14.84	4.41 ^d	0.56	...
ESO358-G060	FCC 302 ^e	Fornax Cluster	IB(s)m:	+803	15.86	12.27 ^f	3.97	20.0
IC 1613	DDO 8, UGC 668	Local Group	IB(s)m	-234	9.88	698 ^g	0.89	0.73
IC 2032	ESO156-G042, AM0405-552	Dorado	IAB(s)m pec:	+1066 ^h	14.78	2.87 ^h	0.35	17.2
IC 5152	ESO237-G027, AM2159-513	field	IA(s)m	+124	11.03	98.0 ⁱ	0.35	2.07
NGC 2915	ESO037-G003, AM0926-762	field	I0; BCD?	+468	12.93	145 ^j	1.10	3.78
NGC 3109	DDO 236, UGCA 194	Antlia-Sextans ^k	SB(s)m	+404	10.26	1110 ^l	1.64	1.33
Sag DIG	ESO594-G004	Local Group	IB(s)m	-77	13.99 ^m	32.6 ⁿ	1.21	1.11

2.2 The control sample of dIs

Richer & McCall (1995) constructed a sample of nearby dIs with direct ([O III] $\lambda 4363$ ) oxygen abundances and well-measured distances from resolved stellar photometry. As a part of his thesis, Lee updated the sample incorporating updates from recent literature and unpublished spectroscopic data (Lee 2001; Lee et al. 2003a). This sample of dIs will be referred to as the control sample, against which the present sample of southern dwarfs will be compared. Because new measurements of IC 1613 and NGC 3109 are discussed here, they are excluded from the control sample in this paper and are included in the present southern sample of dIs.

Property	Value
Loral CCD
Total area	1200 pix $\times$ 800 pix
Usable area	1200 pix $\times$ 270 pix
Pixel size	15 $\mu$ m
Image scale	1.3 arcsec pixel^-1
Gain	1.42 e^- ADU^-1
Read-noise (rms)	6.5 e^-
Grating #09
Groove density	300 lines mm^-1
Blaze $\lambda$ (1st order)	3560 Å
Dispersion	2.87 Å pixel^-1
Effective $\lambda$ range	3500-6950 Å
Long slit
Length	5.8 arcmin
Width ^a	2, 3 arcsec

2 The samples of dwarf galaxies

2.1 The southern sample of dIs

2.2 The control sample of dIs