3 Observations and reductions

Long-slit spectroscopic observations were carried out in two observing runs (2001 Feb. 2-4 UT and Aug. 17-20 UT) with the Cassegrain Spectrograph on the 1.5-metre telescope at the Cerro Tololo Inter-American Observatory. Details of the instrumentation employed and the log of observations are listed in Tables 2 and 3, respectively. Observing conditions were varied. For the February run, all three nights were clear, although high thin patchy clouds were present at times. The lunar illumination increased from 0.55 to 0.76. For the August run, cloud and snow prevented observations for the first two nights; the final two nights were clear with near-zero lunar illumination. The slit angle was kept constant in an east-west orientation for all observations. The central positions of the long slit for each target are listed in Table 3. After visual inspection of an image for each target, the centre of the long-slit was placed at the brightest candidate H II region for each galaxy.

 

 

Table 3: Log of observations. Column (1): Galaxy name in alphabetical order (within each association). Column (2): Date of observation. Columns (3) and (4): Central position of the long-slit: right ascension in hours, minutes and seconds, and declination in degrees, minutes, and seconds (Epoch J2000). Column (5): Number of exposures obtained and the length of each exposure in seconds. Column (6): Total exposure time. Column (7): Mean effective airmass. Column (8): [O III] $\lambda 4363$ : detected, upper limit, or not detected. Column (9): Relative root-mean-square error in the sensitivity function obtained from observations of standard stars. NOTES: ^a H II region label from Webster et al. (1983). ^b H II region number from Miller (1996). ^c Only [O III] $\lambda 5007$ and H$\alpha$ detected. ^d H II region number from Hodge et al. (1990); also known as S3. ^e H II region label from Talent (1980) and Webster et al. (1983). ^f H II region number from Richer & McCall (1992). ^g H II region number from Skillman et al. (1989b) and Strobel et al. (1991).

Galaxy	2001 Date	$\alpha_{\rm slit}$ (J2000)	$\delta_{\rm slit}$ (J2000)	$N_{\rm exp}$	$t_{\rm total}$	$\langle X \rangle$	[O III] $\lambda 4363$	RMS
	(UT)	$(^h\;^m\;^s)$	$(\hbox{$^\circ$ }\;\hbox{$^\prime$ }\;\hbox{$^{\prime\prime}$ })$		(s)			(mag)
(1)	(2)	(3)	(4)	(5)	(6)	(7)	(8)	(9)
Centaurus A group dwarfs
A1243-335 (H II#A) a	2 Feb	12$\;$46$\;$02.4	$-33\;50\;10.0$	$12 \times 600$	7200	1.18	...	3.5%
A1324-412	4 Feb	13$\;$27$\;$37.2	$-41\;28\;29.4$	$2 \times 1200$	2400	1.47	...	6.5%
A1334-277	4 Feb	13$\;$37$\;$20.3	$-28\;02\;15.8$	$8 \times 900$	7200	1.13	...	6.5%
A1346-358 (H II#A) a	3 Feb	13$\;$49$\;$18.7	$-36\;03\;10.4$	$8 \times 900$	7200	1.08	detected	4.1%
DDO 161	3 Feb	13$\;$03$\;$16.7	$-17\;25\;03.2$	$7 \times 900$	6300	1.36	upper limit	4.1%
NGC 5264	2 Feb	13$\;$41$\;$37.0	$-29\;54\;29.0$	$9 \times 600$	5400	1.05	...	3.5%
Sculptor group dwarfs
AM0106-382	20 Aug	01$\;$08$\;$24.9	$-38\;11\;59.8$	$1 \times 300, 2 \times 1800$	3900	1.18	...	5.0%
ESO 347-G017	19 Aug	23$\;$26$\;$56.3	$-37\;20\;53.7$	$3 \times 1800$	5400	1.21	upper limit	5.0%
ESO 348-G009	20 Aug	23$\;$49$\;$26.5	$-37\;45\;42.1$	$1 \times 300, 2 \times 1800$	3900	1.32	...	5.0%
UGCA 442 (H II#2) b	19 Aug	23$\;$43$\;$45.4	$-31\;57\;27.4$	$1 \times 600, 4 \times 1800$	7800	1.07	upper limit	5.0%
Other southern dwarfs
A0355-465 (H II#B) a	3 Feb	03$\;$57$\;$22.5	$-46\;22\;00.2$	$6 \times 900$	5400	1.11	upper limit	4.1%
ESO 302-G014 c	2 Feb	03$\;$51$\;$40.9	$-38\;27\;09.5$	$1 \times 206, 4 \times 3600$	3806	1.17	...	3.5%
ESO 358-G060	4 Feb	03$\;$45$\;$11.7	$-35\;34\;22.9$	$7 \times 900$	6300	1.18	upper limit	6.5%
IC 1613 (H II#13) d	20 Aug	01$\;$04$\;$47.3	$+02\;06\;41.9$	$1 \times 300, 3 \times 1800$	5700	1.19	upper limit	5.0%
IC 1613 (H II#37) d	19 Aug	01$\;$05$\;$00.8	$+02\;04\;26.1$	$1 \times 600, 2 \times 1800$	4200	1.20	detected	5.0%
IC 2032	2 Feb	04$\;$07$\;$02.9	$-55\;19\;31.2$	$12 \times 600$	7200	1.46	...	3.5%
IC 5152 (H II#A) e	20 Aug	22$\;$02$\;$51.8	$-51\;17\;12.0$	$1 \times 300, 3 \times 1800$	5700	1.43	detected	5.0%
NGC 2915	3 Feb	09$\;$26$\;$28.7	$-76\;37\;31.2$	$6 \times 900$	5400	1.47	...	4.1%
NGC 3109 (H II#6) f	4 Feb	10$\;$03$\;$04.2	$-26\;09\;18.5$	$6 \times 900$	5400	1.07	...	6.5%
Sag DIG (H II#3) g	19 Aug	19$\;$30$\;$02.3	$-17\;41\;35.1$	$6 \times 1800$	10800	1.05	...	5.0%

Data reductions were carried out in the standard manner using IRAF routines. The raw two-dimensional images were subtracted for bias and trimmed. Dome flat exposures were used to remove pixel-to-pixel variations in response. Twilight flats were acquired at dusk each night to correct for variations over larger spatial scales. To correct for the "slit function'' in the spatial direction, the variation of illumination along the slit was taken into account using dome and twilight flats. Multiple exposures of a given galaxy facilitated the removal of cosmic rays. Wavelength calibration was obtained using helium-argon (He-Ar) arc lamp exposures taken throughout each night. Flux calibration was obtained using exposures of standard stars Feige 56, LTT 1788, LTT 3864 (February run); and LTT 1020, LTT 7379, LTT 9239 (August run). The flux accuracy is listed in Table 3. Final one-dimensional spectra for each H II region were obtained via unweighted summed extractions. For H II regions which were previously unidentified (i.e., other than those listed in Col. 1, Table 3), individual H II regions or aperture extractions are numbered along the slit increasing to the east. Representative H II region spectra are shown in Fig. 1; the spectrum for IC 1613 H II region #37 is displayed in Fig. 2 to highlight faint emission lines.