H surface photometry of galaxies in the Virgo cluster I. Observations with the San Pedro Martir 2.1 m telescope

A&A 386, 114-123 (2002)
DOI: 10.1051/0004-6361:20020214

H $\alpha$ surface photometry of galaxies in the Virgo cluster
I. Observations with the San Pedro Martir 2.1 m telescope^,

G. Gavazzi ¹ - A. Boselli ² - P. Pedotti ¹ - A. Gallazzi ¹ - L. Carrasco ^3,4

1 - Università degli Studi di Milano-Bicocca, Piazza delle scienze 3, 20126 Milano, Italy
2 - Laboratoire d'Astronomie Spatiale, Traverse du Siphon, 13376 Marseille Cedex 12, France
3 - Instituto Nacional de Astrofísica, Optica y Electrónica, Apartado Postal 51. C.P. 72000 Puebla, Pue., México
4 - Observatorio Astronómico Nacional, UNAM, Apartado Postal 877, C.P. 22860, Ensenada B.C., México

Received 3 December 2001 / Accepted 5 February 2002

Abstract
H $\alpha$ imaging observations of 125 galaxies obtained with the 2.1 m telescope of the San Pedro Martir Observatory (SPM) (Baja California, Mexico) are presented. The observed galaxies are mostly Virgo cluster members (77), with 36 objects in the Coma/A1367 supercluster and 12 in the clusters A2197 and A2199 taken as fillers. H $\alpha$ +[NII] fluxes and equivalent widths, as well as images of the detected targets are presented.

Key words: galaxies: photometry - galaxies: clusters: individual: Virgo

1 Introduction

One of the crucial, yet unsettled issues related to the evolution of galaxies is a robust observational determination of the present stage of star formation activity of local galaxies. By far the best tracer of the massive (> $5~M_\odot$ ) star formation rate (SFR) in galaxies is provided by the intensity of their hydrogen recombination lines, among which primarily H $\alpha$ (Kennicutt 1998). Besides having shown that the activity of star formation (per unit mass) increases along the Hubble sequence (Roberts & Haynes 1994; Kennicutt 1998), the phenomenology of the star formation properties of disk galaxies remains mostly unexplored. One of the unsettled issues refers to the environmental dependence of the mean SFR of galaxies. The very existence of the Schmidt law (Schmidt 1959) $\Sigma_{SFR} = A \Sigma^{\rm N}_{\rm gas}$ (Kennicutt 1998) implies that galaxies suffering from significant gas depletion, such as observed in clusters of galaxies (Giovanelli & Haynes 1985), should have their SFR consiredably quenched. This prediction is however controversial. If on the one hand Kennicutt (1983) found that spirals in the Virgo cluster show mean SFR as much as a factor of two lower than isolated galaxies, Gavazzi et al. (1998) did not confirm this evidence in the Coma and A1367 clusters. The result of Kennicutt (1983) was based on only two dozen galaxies with H $\alpha$ measurements from aperture photometry, thus requiring a confirmation on a larger sample with modern imaging data.

With the aim of solving this riddle we undertook an H $\alpha$ imaging survey of two optically complete samples of galaxies. The first is composed of nearly isolated objects selected from the CGCG (Zwicky et al. 1961-68) in the bridge between Coma and A1367 which we observed down to the limit of 15.7 mag. This constitutes our reference sample of non-cluster objects. The cluster sample is focused on the Virgo cluster. We concentrated the observations on cluster members (V<3000 $\rm km ~s^{-1}$ ) selected from the VCC catalogue of Binggeli et al. (1985) with $m_{\rm pg}< 16.0$ and with Hubble type later than S0a. The presentation of the first set of 77 H $\alpha$ observations obtained with the 2.1 m telescope of the San Pedro Martir Observatory is addressed in the present paper, it continues with 95 observations carried out with the 1.2 m telescopes of the Observatoire de Haute Provence and of the Calar Alto Observatory (Boselli & Gavazzi 2002; Paper II) and with a set of observations, primarily of BCD galaxies, obtained with the INT telescope (Boselli et al. 2002; Paper III). These new observations, combined with the ones available from the literature (Kennicutt & Kent 1983; Romanishin 1990; Young et al. 1996; Koopmann et al. 2001) bring to 235 the number of Virgo galaxies with H $\alpha$ data. They form a sample representative of the H $\alpha$ properties of Virgo galaxies, 75% complete at $m_{\rm pg}< 16.0$ which will be analyzed in a forthcoming paper (Gavazzi et al. 2002a, in preparation, Paper IV).

Table 1: The target galaxies.
Virgo

VCC NGC/IC UGC ${\rm RA}(J2000)$ Dec a b Vel Clust. Dist $\theta$ Type $m_{\rm pg}$ $B_{\rm T}^0$ $H_{\rm T}$

(1) (2) (3) (4) (5) (6) (7) (8) (9) (10) (11) (12) (13) (14) (15)

1 - - 120820.02 134100.2 0.80 0.18 2267 M 32 5.63 BCD 14.78 15.90 12.50

25 4152 7169 121037.23 160159.5 2.54 1.71 2169 M 32 6.09 Sc 12.46 12.47 9.84

47 4165 7201 121211.77 131447.8 1.41 0.76 1862 M 32 4.62 Sa 14.20 14.00 -

49 4168 7203 121216.46 131223.9 1.76 1.40 2307 M 32 4.60 E 12.21 12.63 8.71

58 769 7209 121232.21 120725.9 2.54 1.75 2207 M 32 4.48 Sb 13.17 13.36 10.51

73 4180 7219 121302.99 70219.0 1.88 0.68 2082 W 32 6.91 Sb 13.35 12.74 9.48

81 4186 7223 121326.18 144620.1 0.95 0.81 2075 N 17 4.85 Sc 15.60 15.72 12.53

97 4193 7234 121353.65 131022.2 1.96 0.97 2476 M 32 4.20 Sc 13.20 12.81 9.60

105 - 7239 121408.90 74634.3 2.48 2.06 1221 W 32 6.18 Sd 13.68 - -

120 4197 7247 121438.42 54816.4 3.60 0.64 2064 W 32 7.70 Scd 13.47 12.05 10.42

131 3061 7255 121504.41 140144.5 2.60 0.28 2317 N 17 4.17 Sc 14.34 12.87 -

162 3074 7279 121546.12 104153.7 2.92 0.50 1979 N 17 4.06 Sd 14.41 15.03 11.48

199 4224 7292 121633.63 72743.9 2.92 1.00 2594 W 32 6.05 Sa 12.95 12.07 8.86

221 4234 7309 121708.62 34050.1 1.76 1.56 2031 W 32 9.35 Sc 13.43 13.47 11.23

318 776 7352 121903.40 85122.7 1.71 1.00 2469 W 32 4.57 Scd 14.01 14.04 12.72

358 4264 7364 121935.66 55047.9 1.55 1.06 2633 B 23 7.11 Sa 13.80 13.60 10.17

362 4266 7368 121942.19 53216.9 2.16 0.42 1617 W 32 7.37 Sa 14.51 13.13 -

393 4276 7385 122007.47 74128.1 2.10 2.11 2617 B 23 5.38 Sc 13.25 13.65 10.63

449 4289 7403 122102.34 34319.4 4.33 0.43 2541 S 17 9.00 Sbc 14.34 12.76 -

465 4294 7407 122117.82 113031.5 3.95 1.24 357 N 17 2.49 Sc 12.61 11.69 9.76

492 4300 7413 122141.45 52304.7 2.16 0.70 2310 B 23 7.36 Sa 13.76 13.09 9.68

522 4305 7432 122203.54 124427.8 2.60 1.29 1888 A 17 2.17 Sa 13.19 13.07 9.98

523 4306 7433 122204.23 124712.8 1.87 1.16 1508 A 17 2.17 dS0 13.75 - 10.68

534 4309 7435 122212.25 70838.9 2.00 1.00 1071 B 23 5.66 Sa 13.59 13.50 10.09

552 - 7439 122227.02 43400.0 1.89 1.43 1296 S 17 8.09 Sc 13.61 13.60 -

567 3225 7441 122238.78 64037.1 2.16 0.56 2366 B 23 6.05 Scd 14.35 13.56 -

576 4316 7447 122242.18 91957.1 2.48 0.50 1254 B 23 3.65 Sbc 13.70 12.86 9.61

593 3229 7448 122252.67 64045.1 1.15 0.28 1540 B 23 6.04 S(dS) 15.08 14.92 -

613 4324 7451 122306.12 51500.2 3.52 1.00 1670 S 17 7.39 Sa 12.60 11.95 8.67

667 3259 7469 122348.48 71111.5 1.71 0.84 1420 B 23 5.49 Sc 14.24 13.83 10.85

699 3268 7477 122407.44 63626.7 1.95 1.37 727 B 23 6.01 Pec 14.22 13.47 11.13

713 4356 7482 122414.10 83203.7 3.20 0.50 1137 B 23 4.18 Sc 14.04 12.44 9.81

739 0 - 122440.51 31810.9 2.00 2.00 927 S 17 9.22 Sd 14.36 - -

768 3298 - 122503.69 170057.1 1.03 0.27 2434 A 17 4.83 Sc 14.91 14.32 12.51

785 4378 7497 122517.90 45529.2 3.06 2.48 2557 S 17 7.59 Sa 12.16 12.49 8.41

827 - 7513 122542.71 71255.4 3.60 0.43 992 B 23 5.33 Sc 13.76 12.49 9.85

851 3322 7518 122554.06 73313.5 2.16 0.50 1195 B 23 4.99 Sc 14.14 13.27 10.77

859 - 7522 122558.18 32537.5 2.92 0.37 1428 S 17 9.05 Sc 14.61 13.07 -

921 4412 7536 122635.80 35756.8 1.89 1.57 2289 S 17 8.49 Sbc 13.14 13.41 10.44

950 3356 7547 122651.38 113316.9 1.71 0.84 1098 A 17 1.28 Sm 14.49 15.76 -

951 3358 7550 122654.36 114006.0 1.43 0.94 2066 A 17 1.20 E/dS0 14.35 14.58 11.60

971 4423 7556 122708.93 55248.1 3.06 0.43 1120 B 23 6.57 Sd 14.28 14.16 11.21

980 3365 7563 122711.26 155350.1 2.48 1.00 2342 A 17 3.61 Scd 14.17 14.65 -

989 - - 122717.39 74012.1 0.67 0.50 1846 S 17 4.79 Sc 15.80 - -

1011 - 7567 122729.18 73838.2 1.29 0.55 874 S 17 4.82 Sdm 14.85 - 12.40

1091 - 7590 122818.70 84346.7 1.45 0.42 1119 B 23 3.71 Sbc 14.60 13.65 -

1118 4451 7600 122840.50 91532.9 1.96 0.96 865 B 23 3.18 Sc 13.31 12.92 10.07

1126 3392 7602 122843.26 145958.9 2.92 1.16 1687 A 17 2.66 Sc 13.30 12.45 9.39

1193 4466 7626 122930.59 74148.3 1.20 0.34 757 S 17 4.71 Sc 14.61 13.41 11.23

1249 - 7636 123000.94 75545.6 1.45 1.03 468 S 17 4.47 Im 14.75 15.80 13.37

1290 4480 7647 123026.47 41452.8 2.01 1.07 2438 S 17 8.14 Sb 13.09 12.85 9.78

1330 4492 7656 123059.58 80439.1 1.96 1.96 1777 S 17 4.30 Sa 13.17 13.15 9.42

1356 3446 - 123122.92 112934.3 1.10 0.43 1251 A 17 0.91 Sm/BCD 15.50 15.56 12.85

1379 4498 7669 123139.62 165107.5 2.85 1.53 1505 A 17 4.46 Sc 12.61 12.30 9.97

1393 797 7676 123154.59 150726.6 1.68 1.11 2100 A 17 2.74 Sc 14.01 13.41 10.94

1410 4502 7677 123203.22 164114.7 1.48 0.78 1629 A 17 4.31 Sm 14.57 14.54 11.86

1411 3466 - 123204.83 114902.7 0.69 0.42 911 A 17 0.65 Pec 15.72 15.53 -

1426 - - 123222.80 115338.9 0.80 0.80 1110 A 17 0.63 Im 15.64 16.43 -

1429 3467 7686 123224.01 114714.9 1.00 0.14 7506 bg 101 0.71 Sc 15.41 - -

1442 3474 7687 123236.78 23943.1 2.92 0.36 1735 S 17 9.74 Sd 14.82 14.88 -

**Table 1:** The target galaxies.
Virgo
VCC	NGC/IC	UGC	${\rm RA}(J2000)$	Dec	a	b	Vel	Clust.	Dist	$\theta$	Type	$m_{\rm pg}$	$B_{\rm T}^0$	$H_{\rm T}$
(1)	(2)	(3)	(4)	(5)	(6)	(7)	(8)	(9)	(10)	(11)	(12)	(13)	(14)	(15)
1	-	-	120820.02	134100.2	0.80	0.18	2267	M	32	5.63	BCD	14.78	15.90	12.50
25	4152	7169	121037.23	160159.5	2.54	1.71	2169	M	32	6.09	Sc	12.46	12.47	9.84
47	4165	7201	121211.77	131447.8	1.41	0.76	1862	M	32	4.62	Sa	14.20	14.00	-
49	4168	7203	121216.46	131223.9	1.76	1.40	2307	M	32	4.60	E	12.21	12.63	8.71
58	769	7209	121232.21	120725.9	2.54	1.75	2207	M	32	4.48	Sb	13.17	13.36	10.51
73	4180	7219	121302.99	70219.0	1.88	0.68	2082	W	32	6.91	Sb	13.35	12.74	9.48
81	4186	7223	121326.18	144620.1	0.95	0.81	2075	N	17	4.85	Sc	15.60	15.72	12.53
97	4193	7234	121353.65	131022.2	1.96	0.97	2476	M	32	4.20	Sc	13.20	12.81	9.60
105	-	7239	121408.90	74634.3	2.48	2.06	1221	W	32	6.18	Sd	13.68	-	-
120	4197	7247	121438.42	54816.4	3.60	0.64	2064	W	32	7.70	Scd	13.47	12.05	10.42
131	3061	7255	121504.41	140144.5	2.60	0.28	2317	N	17	4.17	Sc	14.34	12.87	-
162	3074	7279	121546.12	104153.7	2.92	0.50	1979	N	17	4.06	Sd	14.41	15.03	11.48
199	4224	7292	121633.63	72743.9	2.92	1.00	2594	W	32	6.05	Sa	12.95	12.07	8.86
221	4234	7309	121708.62	34050.1	1.76	1.56	2031	W	32	9.35	Sc	13.43	13.47	11.23
318	776	7352	121903.40	85122.7	1.71	1.00	2469	W	32	4.57	Scd	14.01	14.04	12.72
358	4264	7364	121935.66	55047.9	1.55	1.06	2633	B	23	7.11	Sa	13.80	13.60	10.17
362	4266	7368	121942.19	53216.9	2.16	0.42	1617	W	32	7.37	Sa	14.51	13.13	-
393	4276	7385	122007.47	74128.1	2.10	2.11	2617	B	23	5.38	Sc	13.25	13.65	10.63
449	4289	7403	122102.34	34319.4	4.33	0.43	2541	S	17	9.00	Sbc	14.34	12.76	-
465	4294	7407	122117.82	113031.5	3.95	1.24	357	N	17	2.49	Sc	12.61	11.69	9.76
492	4300	7413	122141.45	52304.7	2.16	0.70	2310	B	23	7.36	Sa	13.76	13.09	9.68
522	4305	7432	122203.54	124427.8	2.60	1.29	1888	A	17	2.17	Sa	13.19	13.07	9.98
523	4306	7433	122204.23	124712.8	1.87	1.16	1508	A	17	2.17	dS0	13.75	-	10.68
534	4309	7435	122212.25	70838.9	2.00	1.00	1071	B	23	5.66	Sa	13.59	13.50	10.09
552	-	7439	122227.02	43400.0	1.89	1.43	1296	S	17	8.09	Sc	13.61	13.60	-
567	3225	7441	122238.78	64037.1	2.16	0.56	2366	B	23	6.05	Scd	14.35	13.56	-
576	4316	7447	122242.18	91957.1	2.48	0.50	1254	B	23	3.65	Sbc	13.70	12.86	9.61
593	3229	7448	122252.67	64045.1	1.15	0.28	1540	B	23	6.04	S(dS)	15.08	14.92	-
613	4324	7451	122306.12	51500.2	3.52	1.00	1670	S	17	7.39	Sa	12.60	11.95	8.67
667	3259	7469	122348.48	71111.5	1.71	0.84	1420	B	23	5.49	Sc	14.24	13.83	10.85
699	3268	7477	122407.44	63626.7	1.95	1.37	727	B	23	6.01	Pec	14.22	13.47	11.13
713	4356	7482	122414.10	83203.7	3.20	0.50	1137	B	23	4.18	Sc	14.04	12.44	9.81
739	0	-	122440.51	31810.9	2.00	2.00	927	S	17	9.22	Sd	14.36	-	-
768	3298	-	122503.69	170057.1	1.03	0.27	2434	A	17	4.83	Sc	14.91	14.32	12.51
785	4378	7497	122517.90	45529.2	3.06	2.48	2557	S	17	7.59	Sa	12.16	12.49	8.41
827	-	7513	122542.71	71255.4	3.60	0.43	992	B	23	5.33	Sc	13.76	12.49	9.85
851	3322	7518	122554.06	73313.5	2.16	0.50	1195	B	23	4.99	Sc	14.14	13.27	10.77
859	-	7522	122558.18	32537.5	2.92	0.37	1428	S	17	9.05	Sc	14.61	13.07	-
921	4412	7536	122635.80	35756.8	1.89	1.57	2289	S	17	8.49	Sbc	13.14	13.41	10.44
950	3356	7547	122651.38	113316.9	1.71	0.84	1098	A	17	1.28	Sm	14.49	15.76	-
951	3358	7550	122654.36	114006.0	1.43	0.94	2066	A	17	1.20	E/dS0	14.35	14.58	11.60
971	4423	7556	122708.93	55248.1	3.06	0.43	1120	B	23	6.57	Sd	14.28	14.16	11.21
980	3365	7563	122711.26	155350.1	2.48	1.00	2342	A	17	3.61	Scd	14.17	14.65	-
989	-	-	122717.39	74012.1	0.67	0.50	1846	S	17	4.79	Sc	15.80	-	-
1011	-	7567	122729.18	73838.2	1.29	0.55	874	S	17	4.82	Sdm	14.85	-	12.40
1091	-	7590	122818.70	84346.7	1.45	0.42	1119	B	23	3.71	Sbc	14.60	13.65	-
1118	4451	7600	122840.50	91532.9	1.96	0.96	865	B	23	3.18	Sc	13.31	12.92	10.07
1126	3392	7602	122843.26	145958.9	2.92	1.16	1687	A	17	2.66	Sc	13.30	12.45	9.39
1193	4466	7626	122930.59	74148.3	1.20	0.34	757	S	17	4.71	Sc	14.61	13.41	11.23
1249	-	7636	123000.94	75545.6	1.45	1.03	468	S	17	4.47	Im	14.75	15.80	13.37
1290	4480	7647	123026.47	41452.8	2.01	1.07	2438	S	17	8.14	Sb	13.09	12.85	9.78
1330	4492	7656	123059.58	80439.1	1.96	1.96	1777	S	17	4.30	Sa	13.17	13.15	9.42
1356	3446	-	123122.92	112934.3	1.10	0.43	1251	A	17	0.91	Sm/BCD	15.50	15.56	12.85
1379	4498	7669	123139.62	165107.5	2.85	1.53	1505	A	17	4.46	Sc	12.61	12.30	9.97
1393	797	7676	123154.59	150726.6	1.68	1.11	2100	A	17	2.74	Sc	14.01	13.41	10.94
1410	4502	7677	123203.22	164114.7	1.48	0.78	1629	A	17	4.31	Sm	14.57	14.54	11.86
1411	3466	-	123204.83	114902.7	0.69	0.42	911	A	17	0.65	Pec	15.72	15.53	-
1426	-	-	123222.80	115338.9	0.80	0.80	1110	A	17	0.63	Im	15.64	16.43	-
1429	3467	7686	123224.01	114714.9	1.00	0.14	7506	bg	101	0.71	Sc	15.41	-	-
1442	3474	7687	123236.78	23943.1	2.92	0.36	1735	S	17	9.74	Sd	14.82	14.88	-

Table 1: continued.
Virgo

VCC NGC/IC UGC ${\rm RA}(J2000)$ Dec a b Vel Clust. Dist $\theta$ Type $m_{\rm pg}$ $B_{\rm T}^0$ $H_{\rm T}$

(1) (2) (3) (4) (5) (6) (7) (8) (9) (10) (11) (12) (13) (14) (15)

1491 3486 - 123313.98 125127.4 0.80 0.61 1903 A 17 0.75 dE 15.24 15.58 11.64

1508 4519 7709 123330.08 83916.6 3.60 2.60 1212 S 17 3.79 Sc 12.34 12.14 9.73

1532 800 7716 123356.79 152116.9 1.87 1.36 2335 A 17 3.06 Sc 14.05 13.65 10.73

1557 4533 7725 123422.11 21931.1 2.60 0.43 1759 S 17 10.10 Scd 14.50 13.30 11.74

1581 - 7739 123444.93 61807.4 1.46 1.15 2065 S 17 6.16 Sm 14.55 15.08 -

1624 4544 7756 123536.17 30204.9 2.48 0.50 1151 S 17 9.43 Sc 13.89 12.98 10.35

1654 3562 - 123610.23 95523.3 0.84 0.27 2051 A 17 2.79 Im 15.96 - 14.32

1675 - - 123634.65 80317.6 1.26 0.74 1795 S 17 4.56 Pec 14.47 - 12.31

1686 3583 7784 123643.57 131531.7 2.79 1.71 1122 A 17 1.68 Sm 13.95 13.46 11.00

1699 3589 7790 123702.24 65530.9 1.55 0.82 1635 S 17 5.67 Sm 14.10 14.44 -

1757 4584 7803 123817.79 130635.8 1.87 1.00 1783 A 17 1.96 Sa 13.60 13.59 10.56

1758 - 7802 123820.81 75328.8 1.71 0.27 1788 S 17 4.87 Sc 14.99 13.66 11.72

1789 - - 123921.34 45619.5 1.10 0.62 1619 S 17 7.74 Im 15.07 15.91 12.60

1791 3617 7822 123924.45 75752.5 1.29 0.64 2079 S 17 4.90 Sm/BCD 14.67 14.66 -

1918 - - 124218.10 54421.7 1.03 0.35 980 S 17 7.23 Im 15.80 - -

1923 4630 7871 124231.37 35736.9 2.31 1.60 742 S 17 8.91 Sbc 13.14 12.88 9.91

2023 3742 7932 124531.55 131951.3 2.01 1.00 958 E 17 3.70 Sc 13.86 13.54 11.37

**Table 1:** continued.
Virgo
VCC	NGC/IC	UGC	${\rm RA}(J2000)$	Dec	a	b	Vel	Clust.	Dist	$\theta$	Type	$m_{\rm pg}$	$B_{\rm T}^0$	$H_{\rm T}$
(1)	(2)	(3)	(4)	(5)	(6)	(7)	(8)	(9)	(10)	(11)	(12)	(13)	(14)	(15)
1491	3486	-	123313.98	125127.4	0.80	0.61	1903	A	17	0.75	dE	15.24	15.58	11.64
1508	4519	7709	123330.08	83916.6	3.60	2.60	1212	S	17	3.79	Sc	12.34	12.14	9.73
1532	800	7716	123356.79	152116.9	1.87	1.36	2335	A	17	3.06	Sc	14.05	13.65	10.73
1557	4533	7725	123422.11	21931.1	2.60	0.43	1759	S	17	10.10	Scd	14.50	13.30	11.74
1581	-	7739	123444.93	61807.4	1.46	1.15	2065	S	17	6.16	Sm	14.55	15.08	-
1624	4544	7756	123536.17	30204.9	2.48	0.50	1151	S	17	9.43	Sc	13.89	12.98	10.35
1654	3562	-	123610.23	95523.3	0.84	0.27	2051	A	17	2.79	Im	15.96	-	14.32
1675	-	-	123634.65	80317.6	1.26	0.74	1795	S	17	4.56	Pec	14.47	-	12.31
1686	3583	7784	123643.57	131531.7	2.79	1.71	1122	A	17	1.68	Sm	13.95	13.46	11.00
1699	3589	7790	123702.24	65530.9	1.55	0.82	1635	S	17	5.67	Sm	14.10	14.44	-
1757	4584	7803	123817.79	130635.8	1.87	1.00	1783	A	17	1.96	Sa	13.60	13.59	10.56
1758	-	7802	123820.81	75328.8	1.71	0.27	1788	S	17	4.87	Sc	14.99	13.66	11.72
1789	-	-	123921.34	45619.5	1.10	0.62	1619	S	17	7.74	Im	15.07	15.91	12.60
1791	3617	7822	123924.45	75752.5	1.29	0.64	2079	S	17	4.90	Sm/BCD	14.67	14.66	-
1918	-	-	124218.10	54421.7	1.03	0.35	980	S	17	7.23	Im	15.80	-	-
1923	4630	7871	124231.37	35736.9	2.31	1.60	742	S	17	8.91	Sbc	13.14	12.88	9.91
2023	3742	7932	124531.55	131951.3	2.01	1.00	958	E	17	3.70	Sc	13.86	13.54	11.37

Table 1: continued.
Coma/A1367 supercluster

CGCG NGC/IC UGC ${\rm RA}(J2000)$ Dec a b Vel Clust. Dist $\theta$ Type $m_{\rm pg}$ $B_{\rm T}^0$ $H_{\rm T}$

(1) (2) (3) (4) (5) (6) (7) (8) (9) (10) (11) (12) (13) (14) (15)

97005 - - 113247.12 200214.8 0.90 0.48 6129 Isol 81 2.74 Sc 15.50 15.00 12.41

97023 - - 113651.53 200017.2 0.72 0.70 6320 Group 84 1.78 S0 15.30 15.44 11.80

97026 - 6583 113654.20 195816.6 0.79 0.48 6202 Group 84 1.77 Pec 13.90 14.09 11.49

97027 - - 113654.35 195949.1 0.94 0.63 6630 Group 84 1.77 Sc 14.60 14.60 11.60

97063 - - 114215.51 200254.0 0.57 0.34 6102 A1367 91 0.55 Pec 15.60 15.84 13.20

97064 - - 114214.52 200549.5 0.65 0.44 5976 A1367 91 0.57 S(dS) 15.60 15.78 12.50

97068 - - 114224.47 200706.3 1.23 0.76 5974 A1367 91 0.55 Sbc 14.60 14.38 11.27

97076 - 6680 114302.10 193859.9 1.20 0.54 7060 A1367 91 0.36 Sb 15.50 - 11.39

97079 - - 114313.35 200016.4 0.75 0.45 6996 A1367 91 0.33 Pec 15.70 15.41 13.15

97130 3864 - 114515.66 192331.3 0.68 0.53 6697 A1367 91 0.48 Sa 15.50 15.50 11.86

97134 3867 6731 114529.59 192400.0 1.31 0.44 7466 A1367 91 0.50 S0 14.60 14.28 9.57

97135 3868 - 114529.93 192640.7 0.73 0.49 6385 A1367 91 0.46 S0 14.80 15.14 10.86

101033 - 8407 132250.14 194125.9 1.20 0.20 6729 Isol 89 9.80 Sc 15.70 - 12.29

101049 - 8448 132639.89 195640.6 1.15 0.91 7148 Isol 95 10.09 Sbc 14.90 14.24 11.49

127026 - 6645 114056.23 254650.9 1.12 0.87 6871 Isol 91 6.01 Sbc 14.80 14.76 11.30

127061 3911 6795 114922.24 245616.2 1.20 1.02 5954 Isol 79 5.24 Sc 15.40 15.07 12.99

130005 - - 130410.75 221723.1 0.76 0.50 7058 Isol 93 5.77 Sbc 15.50 14.95 12.24

130025 - 8343 131641.82 215846.3 1.30 1.03 7001 Isol 93 7.10 Sa 15.50 14.85 11.18

130026 867 8353 131719.62 203816.5 1.26 1.11 6870 Group 91 8.33 Sc 15.50 14.52 11.43

130028 868 - 131728.43 203639.9 0.81 0.71 6714 Group 89 8.38 E 15.40 14.59 11.07

130029 870 - 131730.81 203555.0 0.81 0.57 6743 Group 89 8.40 Sc 15.40 14.47 11.44

131008 - 8457 132730.58 205247.9 1.20 0.20 5972 Isol 79 9.48 Sbc 15.60 14.29 11.16

157062 - 6932 115728.50 310503.8 1.10 0.26 6882 Isol 91 11.64 Pec 15.50 14.48 14.53

159037 4585 - 123813.31 285614.1 0.86 0.58 7291 Isol 97 4.86 Sab 14.60 14.48 11.50

159071 - - 124543.41 292558.5 1.08 0.82 6924 Isol 92 3.43 Sc 15.50 14.90 12.78

159072N 4676 7938 124610.19 304354.6 2.20 0.40 6631 Pair 88 4.07 Pec 14.80 12.93 10.74

159072S - 7939 124611.38 304324.9 1.70 0.60 6590 Pair 87 4.05 Pec 14.80 13.53 10.85

160001 - - 125351.45 285843.0 0.80 0.41 7945 A1656 96 1.65 Sb 15.60 15.26 12.49

160009 - - 125432.95 282234.7 0.80 0.47 7132 A1656 96 1.25 S(dS) 15.50 15.07 11.44

160108 - - 130212.74 281252.9 0.46 0.43 8323 A1656 96 0.56 Pec 15.50 15.73 12.90

160110 - - 130221.41 281349.2 0.59 0.28 5733 A1656 96 0.59 S0 15.20 15.50 11.73

160111 - - 130221.50 281521.2 0.60 0.30 7149 A1656 96 0.61 E 15.70 15.91 12.06

160141 - - 130713.15 280248.0 0.50 0.45 7292 A1656 96 1.61 Pec 15.50 15.72 12.51

161040 - - 132324.64 263240.7 0.73 0.40 7260 Isol 96 5.41 Sc 15.60 15.50 12.85

161052 - - 132651.44 263528.4 0.29 0.29 7072 Isol 94 6.15 Pec 15.10 15.40 12.42

161054 4256 - 132703.07 305834.3 0.80 0.46 6767 Isol 90 6.62 Sa 15.50 15.31 12.84

A2197/A2199

224003 - 10354 162121.97 404837.5 1.00 0.84 8946 A2197 122 1.57 Sc 15.60 15.11 -

224012 - - 162337.85 391211.4 0.60 0.55 8370 A2199 125 1.04 S(dS) 15.70 15.68 -

224017 6145 - 162502.24 405648.1 0.95 0.40 8779 A2197 122 0.89 Sc 15.10 14.28 11.34

224026 - - 162652.77 411513.5 1.00 0.90 8580 A2197 122 0.69 Sc 15.20 14.69 -

224035 - 10404 162811.60 394918.7 1.18 0.86 8312 A2199 125 0.28 Sa 15.50 14.26 -

224039 6166 10409 162838.55 393307.5 1.95 1.40 9284 A2199 125 0.01 E 13.90 13.40 9.82

224040 - - 162844.28 392826.9 0.80 0.80 9167 A2199 125 0.08 Sab 15.40 - 11.44

224045 - - 162853.01 393337.4 0.55 0.50 8794 A2199 125 0.02 S(dS) 15.60 - -

224057 - 10429 163033.37 394949.2 1.10 0.90 7392 A2199 125 0.45 Sab 15.30 - -

224059 - 10430 163026.78 412900.9 1.10 1.00 8967 A2197 122 0.68 Sb 15.40 14.71 11.24

224066 - 10436 163103.74 410920.3 1.31 1.28 9064 A2197 122 0.42 Sc 14.80 14.57 11.14

224070 6184 - 163134.51 403356.4 1.23 0.80 8331 A2197 122 0.43 Sb 15.10 14.33 -

**Table 1:** continued.
Coma/A1367 supercluster
CGCG	NGC/IC	UGC	${\rm RA}(J2000)$	Dec	a	b	Vel	Clust.	Dist	$\theta$	Type	$m_{\rm pg}$	$B_{\rm T}^0$	$H_{\rm T}$
(1)	(2)	(3)	(4)	(5)	(6)	(7)	(8)	(9)	(10)	(11)	(12)	(13)	(14)	(15)
97005	-	-	113247.12	200214.8	0.90	0.48	6129	Isol	81	2.74	Sc	15.50	15.00	12.41
97023	-	-	113651.53	200017.2	0.72	0.70	6320	Group	84	1.78	S0	15.30	15.44	11.80
97026	-	6583	113654.20	195816.6	0.79	0.48	6202	Group	84	1.77	Pec	13.90	14.09	11.49
97027	-	-	113654.35	195949.1	0.94	0.63	6630	Group	84	1.77	Sc	14.60	14.60	11.60
97063	-	-	114215.51	200254.0	0.57	0.34	6102	A1367	91	0.55	Pec	15.60	15.84	13.20
97064	-	-	114214.52	200549.5	0.65	0.44	5976	A1367	91	0.57	S(dS)	15.60	15.78	12.50
97068	-	-	114224.47	200706.3	1.23	0.76	5974	A1367	91	0.55	Sbc	14.60	14.38	11.27
97076	-	6680	114302.10	193859.9	1.20	0.54	7060	A1367	91	0.36	Sb	15.50	-	11.39
97079	-	-	114313.35	200016.4	0.75	0.45	6996	A1367	91	0.33	Pec	15.70	15.41	13.15
97130	3864	-	114515.66	192331.3	0.68	0.53	6697	A1367	91	0.48	Sa	15.50	15.50	11.86
97134	3867	6731	114529.59	192400.0	1.31	0.44	7466	A1367	91	0.50	S0	14.60	14.28	9.57
97135	3868	-	114529.93	192640.7	0.73	0.49	6385	A1367	91	0.46	S0	14.80	15.14	10.86
101033	-	8407	132250.14	194125.9	1.20	0.20	6729	Isol	89	9.80	Sc	15.70	-	12.29
101049	-	8448	132639.89	195640.6	1.15	0.91	7148	Isol	95	10.09	Sbc	14.90	14.24	11.49
127026	-	6645	114056.23	254650.9	1.12	0.87	6871	Isol	91	6.01	Sbc	14.80	14.76	11.30
127061	3911	6795	114922.24	245616.2	1.20	1.02	5954	Isol	79	5.24	Sc	15.40	15.07	12.99
130005	-	-	130410.75	221723.1	0.76	0.50	7058	Isol	93	5.77	Sbc	15.50	14.95	12.24
130025	-	8343	131641.82	215846.3	1.30	1.03	7001	Isol	93	7.10	Sa	15.50	14.85	11.18
130026	867	8353	131719.62	203816.5	1.26	1.11	6870	Group	91	8.33	Sc	15.50	14.52	11.43
130028	868	-	131728.43	203639.9	0.81	0.71	6714	Group	89	8.38	E	15.40	14.59	11.07
130029	870	-	131730.81	203555.0	0.81	0.57	6743	Group	89	8.40	Sc	15.40	14.47	11.44
131008	-	8457	132730.58	205247.9	1.20	0.20	5972	Isol	79	9.48	Sbc	15.60	14.29	11.16
157062	-	6932	115728.50	310503.8	1.10	0.26	6882	Isol	91	11.64	Pec	15.50	14.48	14.53
159037	4585	-	123813.31	285614.1	0.86	0.58	7291	Isol	97	4.86	Sab	14.60	14.48	11.50
159071	-	-	124543.41	292558.5	1.08	0.82	6924	Isol	92	3.43	Sc	15.50	14.90	12.78
159072N	4676	7938	124610.19	304354.6	2.20	0.40	6631	Pair	88	4.07	Pec	14.80	12.93	10.74
159072S	-	7939	124611.38	304324.9	1.70	0.60	6590	Pair	87	4.05	Pec	14.80	13.53	10.85
160001	-	-	125351.45	285843.0	0.80	0.41	7945	A1656	96	1.65	Sb	15.60	15.26	12.49
160009	-	-	125432.95	282234.7	0.80	0.47	7132	A1656	96	1.25	S(dS)	15.50	15.07	11.44
160108	-	-	130212.74	281252.9	0.46	0.43	8323	A1656	96	0.56	Pec	15.50	15.73	12.90
160110	-	-	130221.41	281349.2	0.59	0.28	5733	A1656	96	0.59	S0	15.20	15.50	11.73
160111	-	-	130221.50	281521.2	0.60	0.30	7149	A1656	96	0.61	E	15.70	15.91	12.06
160141	-	-	130713.15	280248.0	0.50	0.45	7292	A1656	96	1.61	Pec	15.50	15.72	12.51
161040	-	-	132324.64	263240.7	0.73	0.40	7260	Isol	96	5.41	Sc	15.60	15.50	12.85
161052	-	-	132651.44	263528.4	0.29	0.29	7072	Isol	94	6.15	Pec	15.10	15.40	12.42
161054	4256	-	132703.07	305834.3	0.80	0.46	6767	Isol	90	6.62	Sa	15.50	15.31	12.84
A2197/A2199
224003	-	10354	162121.97	404837.5	1.00	0.84	8946	A2197	122	1.57	Sc	15.60	15.11	-
224012	-	-	162337.85	391211.4	0.60	0.55	8370	A2199	125	1.04	S(dS)	15.70	15.68	-
224017	6145	-	162502.24	405648.1	0.95	0.40	8779	A2197	122	0.89	Sc	15.10	14.28	11.34
224026	-	-	162652.77	411513.5	1.00	0.90	8580	A2197	122	0.69	Sc	15.20	14.69	-
224035	-	10404	162811.60	394918.7	1.18	0.86	8312	A2199	125	0.28	Sa	15.50	14.26	-
224039	6166	10409	162838.55	393307.5	1.95	1.40	9284	A2199	125	0.01	E	13.90	13.40	9.82
224040	-	-	162844.28	392826.9	0.80	0.80	9167	A2199	125	0.08	Sab	15.40	-	11.44
224045	-	-	162853.01	393337.4	0.55	0.50	8794	A2199	125	0.02	S(dS)	15.60	-	-
224057	-	10429	163033.37	394949.2	1.10	0.90	7392	A2199	125	0.45	Sab	15.30	-	-
224059	-	10430	163026.78	412900.9	1.10	1.00	8967	A2197	122	0.68	Sb	15.40	14.71	11.24
224066	-	10436	163103.74	410920.3	1.31	1.28	9064	A2197	122	0.42	Sc	14.80	14.57	11.14
224070	6184	-	163134.51	403356.4	1.23	0.80	8331	A2197	122	0.43	Sb	15.10	14.33	-

2 The sample

Galaxies observed in this work have been selected from the Virgo Cluster Catalogue (VCC) of Binggeli et al. (1985), which is complete to the optical magnitude $m_{\rm pg} = 18.0$ . The targets were selected using the following criteria:
$m_{\rm pg}< 16.0$ .
Hubble type later than S0a (as given in the VCC).
Classified as cluster members, possible members or belonging to the W, W', M clouds or to the southern extension (Binggeli et al. 1985, 1993) matching V<3000 $\rm km ~s^{-1}$ .
Because of the particular set of interferometric filters available at SPM the velocity interval of galaxies selected in this paper was narrowed to 350<V<3000 $\rm km ~s^{-1}$ . In this paper we present the first set of observations including 77 Virgo galaxies matching these selection criteria. Furthermore 36 galaxies in the Coma/A1367 supercluster and 12 in A2197 and A2199, observed as fillers are presented.
The target galaxies are listed in Table 1 as follows:

Column 1: VCC designation, from Binggeli et al. (1985) for Virgo galaxies, or CGCG (Zwicky et al. 1961-68) for Coma supercluster and A2197 and A2199 galaxies;
Column 2: NGC/IC name;
Column 3: UGC name (Nilson 1973);
Columns 4 and 5: J2000 celestial coordinates, from NED;
Columns 6 and 7: major an minor optical diameters (arcmin). For VCC galaxies the diameters are measured on the du Pont plates at the faintest detectable isophote, as listed in the VCC. For CGCG galaxies these are the major and minor optical diameters (a₂₅, b₂₅) derived as explained in Gavazzi & Boselli (1996);
Column 8: heliocentric velocity (km s^-1) from the VCC or from Gavazzi et al. (1999a);
Column 9: the membership to a cluster or supercluster, defined as in Gavazzi et al. (1999a) for Virgo and Gavazzi et al. (1999b) for the Coma/A1367 supercluster;
Column 10: the distance (Mpc); we assume the average values for the different substructures of Virgo as given in Gavazzi et al. (1999a), 96 Mpc for galaxies in Coma, 91 Mpc for A1367, 125 Mpc for A2197 and 122 Mpc for A2199. For galaxies not belonging to the clusters, the distance is determined from the redshift assuming $H_0 = 75~\rm km~s^{-1}~Mpc^{-1}$ ;
Column 11: projected angular distance from the cluster centre (degrees);
Column 12: morphological type as given in the VCC or in Gavazzi & Boselli (1996);
Column 13: photographic magnitude as given in the VCC or in the CGCG;
Column 14: B magnitude determined and corrected for dust extinction as described in Gavazzi & Boselli (1996);
Column 15: asymptotic H band magnitude, uncorrected for extinction, determined as described in Gavazzi et al. (2000).

3 Observations

Narrow band imaging in the H $\alpha$ emission line ( $\lambda$ = 6562.8 Å) of 125 galaxies was obtained during 13 nights distributed in 3 runs (1999, 2000 and 2001), using the 2.1 m telescope at San Pedro Martir Observatory (SPM) (Baja California, Mexico). The (f/7.5) SPM Cassegrain focus was equipped in 1999-2000 with a thinned TK1024 $\times$ 1024 pixels CCD detector with pixel size is 0.30 arcsec. In 2001 we used a Thompson 1024 $\times$ 1024 pixels CCD detector with pixel size is 0.36 arcsec. Each galaxy was observed through two narrow band interferometric filters centered at $\lambda$ 6603 and $\lambda$ 6723 Å, with a width of $\sim$ 90 Å. The $\lambda$ 6603 Å was selected to cover the H $\alpha$ line (ON-band filter) for galaxies at the redshift of Virgo (with $350<V<3000~{\rm km~s}^{-1}$ ) and to recover the red continuum (OFF-band) for higher redshift objects (in the Coma and Hercules superclusters). The $\lambda$ 6723 Å filter provided us with the OFF-band frames for Virgo and the ON-band frames for higher redshift objects. The typical integration time was of 15-40 min, equal for the ON- and OFF-band, generally split into 3 shorter exposures. The observations were obtained with seeing ranging from 1.8 to 3 arcsec, but mostly in photometric conditions. The observations were flux calibrated using the standard stars Feige 34 and Hz44 from the catalogue of Massey et al. (1988), observed every 2 hours. Repeated measurements gave <0.05 mag differences, which we assume as the typical uncertainty ( $1 \sigma$ ) of the photometric results given in this work. Most frames were obtained in these conditions. Some were obtained in transparent conditions ( $0.05< \sigma <0.10$ mag) and few were observed through thin cirrus ( $\sigma > 0.10$ mag). For the latter we don't derive the flux but the H $\alpha$ equivalent width only.

4 Image analysis

The reduction of the CCD frames follows a procedure similar to the one described in previous papers (e.g. Gavazzi et al. 1998), based on the IRAF STSDAS reduction packages. To remove the detector response each image was bias subtracted and divided by the median of several flat field exposures obtained on empty regions of the twilight sky. When three images in the same filter were available, a median combination of the realigned images allows removal of cosmic rays. For galaxies observed in single exposures these were removed manually by direct inspection of the frames. Subtraction of contaminating objects, such as nearby stars and galaxies, was done by direct inspection of the frames. The sky background was determined in each frame in concentric object-free annuli around the object and then subtracted from the flat-fielded image. The typical uncertainty on the mean background is estimated 10% of the rms in the individual pixels. This represents the dominant source of error in low S/N regions.

4.1 ${\mathsfsl H}\alpha+{\mathsfsl {[NII]}}$ parameters

The flux from the [NII] emission lines ( $\lambda$ 6548-6584 Å) bracketing ${\rm H\alpha }$ are included in the ON-band observations. Herafter we will use the semplified notation " ${\rm H\alpha }$ '' to refer to " ${\rm H\alpha+[NII]}$ ''. Both the flux and the EW of the ${\rm H\alpha }$ line can be recovered from narrow band observations by subtracting the continuum contribution, determined in the OFF-band frame, from the ON-band frame (continuum+line), provided that the two filters have identical profiles. This is generally not true, however the ratio n of their integrated profiles can be determined assuming that field stars (with null ${\rm H\alpha }$ in emission) have identical fluxes in the ON- and OFF-band frames.

The total counts in the two frames have been obtained by integrating the pixel counts over the area covered by each galaxy, as derived from their optical axes a and b. If $C_{\rm ON}$ and $C_{\rm OFF}$ represent the integrated pixel counts in the ON and OFF-band filter respectively,
${C_{\rm NET} = C_{\rm ON} - n C_{\rm OFF}}$
then the net flux in the ${\rm H\alpha }$ line is given by:

$\begin{displaymath}{F({\rm H}\alpha) = 10^{Z{\rm p}} \frac{C_{\rm NET}}{T R_{\rm ON}({\rm H}\alpha)}} \end{displaymath}$

(1)

and the equivalent width by:

$\begin{displaymath}{{\rm H}\alpha EW = \frac{\int R_{\rm ON}(\lambda){\rm d}\lam... ...{R_{\rm ON}({\rm H}\alpha)} \frac{C_{\rm NET}}{n C_{\rm OFF}}} \end{displaymath}$

(2)

where T is the integration time (s), $10^{Z{\rm p}}$ is the ON-band zero point ( $\rm erg~cm^{-2}~s^{-1}$ ) corrected for atmosferic extinction and $R_{\rm ON}(\lambda)$ is the trasmissivity of the ON-filter at the wavelength of the redshifted ${\rm H\alpha }$ line.

Equation (2) shows that the H $\alpha$ equivalent width does not depend on $Z{\rm p}$ , but only on the normalization constant n, thus it can be estimated also in marginal photometric conditions.

$\begin{figure} \par\includegraphics[width=7.5cm,clip]{ms2157f1.ps}\end{figure}$	Figure 1: The profiles of the 6603 and 6723 Å filters. Filled circles mark the transmission at ${\rm H\alpha }$ of Virgo galaxies. Filled squares and crosses mark the transmission at [SII] of Virgo galaxies.
Open with DEXTER

Due to an unfortunate choice of the OFF-band filter ( $\rm\lambda 6723~\AA$ ), Virgo galaxies ( 350<V<3000 $\rm km ~s^{-1}$ ) have their [SII] emission doublet ( $\rm\lambda 6717$ -6731 Å) inside the transmission window of the OFF-band filter (see Fig. 1). Thus the contribution of these two lines must be subtracted to estimate the continuum. To do so we determine $R_{\rm OFF}(\lambda)$ : the trasmissivity of the OFF-filter at the wavelength of the redshifted $\rm [SII]$ lines. The factor K, accounting for the [SII] contamination is:

$\begin{displaymath}K = 1 - \frac{F([{\rm SII}]_{1})}{F({\rm H}\alpha)} \frac{R_{... ...frac{R_{\rm OFF}([{\rm SII}]_{2})}{R_{\rm ON}({\rm H}\alpha)} \end{displaymath}$

(3)

where $\rm [SII]_{1}$ is the line at $\rm\lambda 6717~\AA$ and $\rm [SII]_{2}$ is the one at $\rm\lambda 6731~\AA$ .

For 24 galaxies the ratios $F([{\rm SII}])/F({\rm H}\alpha )$ of the two [SII] lines are known from spectroscopy (Gavazzi et al. 2002b) (see Fig. 2). When this measurement is not available their average values: $<F([{\rm SII}]_{6717})/F({\rm H}\alpha)>$ $=0.21 \pm 0.09$ and $<F([{\rm SII}]_{6731})/F({\rm H}\alpha)>$ $=0.17 \pm 0.15$ are assumed.
Accounting for the [SII] contamination, Eq. (1) becomes:

$\begin{displaymath}{F({\rm H}\alpha) = 10^{Z{\rm p}} \frac{C_{\rm NET}}{T R_{\rm ON}({\rm H}\alpha) K}} \end{displaymath}$

(4)

and Eq. (2) becomes:

$\begin{displaymath}{{\rm H}\alpha EW = \frac{\int R_{\rm ON}(\lambda){\rm d}\lam... ...pha)} \frac{C_{\rm NET}}{C_{\rm ON} (K-1)+n C_{\rm OFF}}\cdot} \end{displaymath}$

(5)

For extended sources the dominant source of error is associated with the variations of the background on scales similar to the source, which depends on the quality of the flat-fielding. We measured the background in several regions comparable with the size of the galaxies and determined that its fluctuation (per pixel) is 10% of the purely statistical rms on the individual pixels. The total uncertainty on the ON and OFF counts is thus proportional to the area A (in pixels) covered by each galaxy, estimated from the optical major and minor axes, a and b.

$\begin{displaymath}\sigma_{\rm ON} = 0.1 ~{\rm rms}_{\rm ON}~A \end{displaymath}$

$\begin{displaymath}\sigma_{\rm OFF} = 0.1 ~{\rm rms}_{\rm OFF}~A \end{displaymath}$

which add up to:

$\begin{displaymath}\sigma_{\rm NET} = \sqrt{(\sigma_{\rm ON})^2 + (\sigma_{\rm OFF})^2 + (0.1~C_{\rm NET})^2}. \end{displaymath}$

The term $(0.1~C_{\rm NET})^2$ accounts for the uncertainty on the photometric calibration.

The errors on the H $\alpha$ flux and equivalent width are finally:

$\begin{displaymath}{\sigma_{F} = \frac{F({\rm H}\alpha)}{C_{\rm NET}} \sigma_{\rm NET}} \end{displaymath}$

(6)

$\begin{displaymath}{\sigma_{EW} = \frac{\int R_{\rm ON}(\lambda){\rm d}\lambda}{... ...rm H}\alpha) (C_{\rm ON}(K-1)+n C_{\rm OFF})^2} \sqrt{\Sigma}} \end{displaymath}$

(7)

where:
$\Sigma=(2-K)^2 (n C_{\rm OFF})^2 \sigma_{\rm ON}^2 + K^2 C_{\rm ON}^2 \sigma_{\rm OFF}^2.$

$\begin{figure} \par\includegraphics[width=7.4cm,clip]{ms2157f2.ps}\end{figure}$	Figure 2: Histograms of the $F([{\rm SII}])/F({\rm H}\alpha )$ ratios determined from spectroscopy.
Open with DEXTER

Table 2: The results of the observations.
Virgo

VCC Date N T R(H $\alpha$ ) n Phot K $EW ({\rm H}\alpha)$ $F({\rm H}\alpha)$ $EW ({\rm H}\alpha)$ (ref) $F({\rm H}\alpha)$ (ref)

Å $\rm erg~cm^{-2}~s^{-1}$ Å $\rm erg~cm^{-2}~s^{-1}$

(1) (2) (3) (4) (5) (6) (7) (8) (9) (10) (11) (12)

1 18-4-1999 3 7 0.81 1.10 P 0.76 11.6 $\pm$ 0.9 -13.51 $\pm$ 0.05 14(11)

25 19-4-2001 3 5 0.81 1.10 P 0.82 58.0 $\pm$ 2.5 -11.70 $\pm$ 0.04 46(11), 33(1) -11.85(1)

47 18-4-1999 3 5 0.82 1.10 P 0.77 16.4 $\pm$ 5.6 -13.04 $\pm$ 0.11 11(11)

49 18-4-1999 3 5 0.80 1.15 P 0.85 0.1 $\pm$ 1.6 - 0(11)

58 21-4-1999 3 5 0.81 1.10 P 0.83 14.8 $\pm$ 6.2 -12.51 $\pm$ 0.15 18(11)

73 20-4-2001 3 5 0.81 1.18 P 0.81 11.2 $\pm$ 0.6 -12.39 $\pm$ 0.05

81 20-4-1999 4 5 0.81 1.10 P 0.81 21.0 $\pm$ 17.8 -13.26 $\pm$ 0.27

97 21-4-1999 3 5 0.79 1.10 P 0.94 13.9 $\pm$ 1.2 -12.33 $\pm$ 0.05 15(11)

105 01-4-2000 4 10 0.85 1.00 P 0.71 13.6 $\pm$ 9.4 -12.89 $\pm$ 0.20

120 19-4-1999 4 10 0.81 1.10 P 0.80 54.0 $\pm$ 2.0 -11.92 $\pm$ 0.04

131 31-3-2000 3 7 0.80 1.00 P 0.82 22.6 $\pm$ 1.6 -12.68 $\pm$ 0.05 24(11)

162 02-4-2000 3 10 0.82 1.00 P 0.78 30.4 $\pm$ 5.2 -12.88 $\pm$ 0.07 36(11)

199 31-3-2000 3 10 0.79 1.00 P 0.92 10.4 $\pm$ 0.6 -12.24 $\pm$ 0.05

221 20-4-1999 3 5 0.82 1.10 P 0.80 53.3 $\pm$ 4.9 -12.07 $\pm$ 0.05

318 18-4-1999 3 5 0.80 1.10 P 0.85 50.6 $\pm$ 9.4 -12.51 $\pm$ 0.07 31(11)

358 20-4-2001 3 5 0.79 1.11 P 0.93 -0.3 $\pm$ 0.7 -

362 22-4-2001 1 5 0.83 1.11 P 0.71 -3.5 $\pm$ 1.4 -

393 20-4-2001 3 5 0.76 1.14 P 0.93 25.3 $\pm$ 3.3 -12.34 $\pm$ 0.06 21(11)

449 01-4-2000 3 10 0.79 1.00 P 0.91 14.5 $\pm$ 1.7 -12.76 $\pm$ 0.06

465 19-4-2001 1 15 0.53 1.15 T 0.52 56.8 $\pm$ 3.4 -11.63 $\pm$ 0.04 64(1) -11.65(1)

492 20-4-2001 3 5 0.80 1.29 C 0.85 6.2 $\pm$ 0.8 -

522 20-4-1999 3 5 0.82 1.10 P 0.78 -0.0 $\pm$ 8.2 -

523 20-4-1999 3 5 0.84 1.10 P 0.72 3.1 $\pm$ 3.7 -13.18 $\pm$ 0.36

534 20-4-2001 3 5 0.84 1.08 T 0.71 0.1 $\pm$ 2.1 - 0(11)

552 19-4-1999 4 5 0.85 1.10 P 0.72 48.0 $\pm$ 7.5 -12.19 $\pm$ 0.06

567 23-4-2001 3 5 0.80 1.16 P 0.87 21.6 $\pm$ 2.3 -12.73 $\pm$ 0.06

576 02-4-2000 3 10 0.85 1.00 P 0.72 13.8 $\pm$ 0.9 -12.49 $\pm$ 0.05

593 23-4-2001 3 5 0.84 1.16 P 0.72 5.7 $\pm$ 1.8 -13.66 $\pm$ 0.10

613 01-4-2000 3 7 0.83 1.00 P 0.82 5.7 $\pm$ 0.9 -12.40 $\pm$ 0.07

667 23-4-2001 3 5 0.84 1.15 P 0.72 8.7 $\pm$ 2.6 -12.97 $\pm$ 0.09

699 23-4-2001 3 5 0.79 1.11 P 0.68 41.6 $\pm$ 7.0 -12.27 $\pm$ 0.06

713 31-3-2000 3 10 0.85 1.00 P 0.71 8.0 $\pm$ 1.2 -12.72 $\pm$ 0.06 8(11)

739 23-4-2001 3 7 0.83 1.11 P 0.70 35.7 $\pm$ 14.0 -12.56 $\pm$ 0.10

768 24-4-2001 2 5 0.80 1.11 P 0.89 42.5 $\pm$ 1.5 -12.83 $\pm$ 0.04

785 01-4-2000 3 5 0.79 1.00 P 0.92 8.4 $\pm$ 2.1 -12.19 $\pm$ 0.10

827 19-4-1999 4 10 0.84 1.10 P 0.72 25.8 $\pm$ 1.4 -12.25 $\pm$ 0.05 53(11)

851 23-4-2001 3 5 0.85 1.16 P 0.61 20.1 $\pm$ 2.7 -12.55 $\pm$ 0.05 26(11)

859 02-4-2000 3 10 0.84 1.00 P 0.72 12.7 $\pm$ 1.5 -12.82 $\pm$ 0.06

921 19-4-1999 4 5 0.80 1.10 P 0.85 37.6 $\pm$ 3.1 -12.03 $\pm$ 0.05

950 21-4-2001 3 10 0.85 1.17 P 0.71 23.3 $\pm$ 10.8 -13.45 $\pm$ 0.13

951 19-4-1999 2 5 0.81 1.10 C 0.80 -0.7 $\pm$ 17.5 -

971 01-4-2000 3 10 0.85 1.00 P 0.71 28.5 $\pm$ 2.3 -12.52 $\pm$ 0.05

980 31-3-2000 3 10 0.80 1.00 P 0.86 40.2 $\pm$ 6.3 -12.65 $\pm$ 0.06

989 24-4-2001 3 7 0.82 1.11 P 0.77 2.8 $\pm$ 7.3 -14.63 $\pm$ 0.82

1011 24-4-2001 3 7 0.83 1.11 P 0.70 13.1 $\pm$ 3.5 -13.27 $\pm$ 0.08

1091 24-4-2001 3 5 0.85 1.15 P 0.71 58.6 $\pm$ 2.1 -12.33 $\pm$ 0.04

1118 20-4-2001 3 5 0.83 1.15 C 0.70 17.3 $\pm$ 2.0 -

1126 19-4-1999 4 5 0.83 1.10 P 0.74 10.7 $\pm$ 4.5 -12.55 $\pm$ 0.13

1193 23-4-2001 3 5 0.80 1.11 P 0.57 30.5 $\pm$ 2.2 -12.58 $\pm$ 0.05 30(11)

1249 23-4-2001 4 5 0.63 1.08 P 0.60 192.3 $\pm$ 58 $\dagger\dagger$ -14.07 $\pm$ 0.06 $\dagger\dagger$

1290 31-3-2000 3 10 0.80 1.00 P 0.89 29.7 $\pm$ 1.0 -12.09 $\pm$ 0.04

**Table 2:** The results of the observations.
Virgo
VCC	Date	N	T	R(H $\alpha$ )	n	Phot	K	$EW ({\rm H}\alpha)$	$F({\rm H}\alpha)$	$EW ({\rm H}\alpha)$ (ref)	$F({\rm H}\alpha)$ (ref)
								Å	$\rm erg~cm^{-2}~s^{-1}$	Å	$\rm erg~cm^{-2}~s^{-1}$
(1)	(2)	(3)	(4)	(5)	(6)	(7)	(8)	(9)	(10)	(11)	(12)
1	18-4-1999	3	7	0.81	1.10	P	0.76	11.6 $\pm$ 0.9	-13.51 $\pm$ 0.05	14(11)
25	19-4-2001	3	5	0.81	1.10	P	0.82	58.0 $\pm$ 2.5	-11.70 $\pm$ 0.04	46(11), 33(1)	-11.85(1)
47	18-4-1999	3	5	0.82	1.10	P	0.77	16.4 $\pm$ 5.6	-13.04 $\pm$ 0.11	11(11)
49	18-4-1999	3	5	0.80	1.15	P	0.85	0.1 $\pm$ 1.6	-	0(11)
58	21-4-1999	3	5	0.81	1.10	P	0.83	14.8 $\pm$ 6.2	-12.51 $\pm$ 0.15	18(11)
73	20-4-2001	3	5	0.81	1.18	P	0.81	11.2 $\pm$ 0.6	-12.39 $\pm$ 0.05
81	20-4-1999	4	5	0.81	1.10	P	0.81	21.0 $\pm$ 17.8	-13.26 $\pm$ 0.27
97	21-4-1999	3	5	0.79	1.10	P	0.94	13.9 $\pm$ 1.2	-12.33 $\pm$ 0.05	15(11)
105	01-4-2000	4	10	0.85	1.00	P	0.71	13.6 $\pm$ 9.4	-12.89 $\pm$ 0.20
120	19-4-1999	4	10	0.81	1.10	P	0.80	54.0 $\pm$ 2.0	-11.92 $\pm$ 0.04
131	31-3-2000	3	7	0.80	1.00	P	0.82	22.6 $\pm$ 1.6	-12.68 $\pm$ 0.05	24(11)
162	02-4-2000	3	10	0.82	1.00	P	0.78	30.4 $\pm$ 5.2	-12.88 $\pm$ 0.07	36(11)
199	31-3-2000	3	10	0.79	1.00	P	0.92	10.4 $\pm$ 0.6	-12.24 $\pm$ 0.05
221	20-4-1999	3	5	0.82	1.10	P	0.80	53.3 $\pm$ 4.9	-12.07 $\pm$ 0.05
318	18-4-1999	3	5	0.80	1.10	P	0.85	50.6 $\pm$ 9.4	-12.51 $\pm$ 0.07	31(11)
358	20-4-2001	3	5	0.79	1.11	P	0.93	-0.3 $\pm$ 0.7	-
362	22-4-2001	1	5	0.83	1.11	P	0.71	-3.5 $\pm$ 1.4	-
393	20-4-2001	3	5	0.76	1.14	P	0.93	25.3 $\pm$ 3.3	-12.34 $\pm$ 0.06	21(11)
449	01-4-2000	3	10	0.79	1.00	P	0.91	14.5 $\pm$ 1.7	-12.76 $\pm$ 0.06
465	19-4-2001	1	15	0.53	1.15	T	0.52	56.8 $\pm$ 3.4	-11.63 $\pm$ 0.04	64(1)	-11.65(1)
492	20-4-2001	3	5	0.80	1.29	C	0.85	6.2 $\pm$ 0.8	-
522	20-4-1999	3	5	0.82	1.10	P	0.78	-0.0 $\pm$ 8.2	-
523	20-4-1999	3	5	0.84	1.10	P	0.72	3.1 $\pm$ 3.7	-13.18 $\pm$ 0.36
534	20-4-2001	3	5	0.84	1.08	T	0.71	0.1 $\pm$ 2.1	-	0(11)
552	19-4-1999	4	5	0.85	1.10	P	0.72	48.0 $\pm$ 7.5	-12.19 $\pm$ 0.06
567	23-4-2001	3	5	0.80	1.16	P	0.87	21.6 $\pm$ 2.3	-12.73 $\pm$ 0.06
576	02-4-2000	3	10	0.85	1.00	P	0.72	13.8 $\pm$ 0.9	-12.49 $\pm$ 0.05
593	23-4-2001	3	5	0.84	1.16	P	0.72	5.7 $\pm$ 1.8	-13.66 $\pm$ 0.10
613	01-4-2000	3	7	0.83	1.00	P	0.82	5.7 $\pm$ 0.9	-12.40 $\pm$ 0.07
667	23-4-2001	3	5	0.84	1.15	P	0.72	8.7 $\pm$ 2.6	-12.97 $\pm$ 0.09
699	23-4-2001	3	5	0.79	1.11	P	0.68	41.6 $\pm$ 7.0	-12.27 $\pm$ 0.06
713	31-3-2000	3	10	0.85	1.00	P	0.71	8.0 $\pm$ 1.2	-12.72 $\pm$ 0.06	8(11)
739	23-4-2001	3	7	0.83	1.11	P	0.70	35.7 $\pm$ 14.0	-12.56 $\pm$ 0.10
768	24-4-2001	2	5	0.80	1.11	P	0.89	42.5 $\pm$ 1.5	-12.83 $\pm$ 0.04
785	01-4-2000	3	5	0.79	1.00	P	0.92	8.4 $\pm$ 2.1	-12.19 $\pm$ 0.10
827	19-4-1999	4	10	0.84	1.10	P	0.72	25.8 $\pm$ 1.4	-12.25 $\pm$ 0.05	53(11)
851	23-4-2001	3	5	0.85	1.16	P	0.61	20.1 $\pm$ 2.7	-12.55 $\pm$ 0.05	26(11)
859	02-4-2000	3	10	0.84	1.00	P	0.72	12.7 $\pm$ 1.5	-12.82 $\pm$ 0.06
921	19-4-1999	4	5	0.80	1.10	P	0.85	37.6 $\pm$ 3.1	-12.03 $\pm$ 0.05
950	21-4-2001	3	10	0.85	1.17	P	0.71	23.3 $\pm$ 10.8	-13.45 $\pm$ 0.13
951	19-4-1999	2	5	0.81	1.10	C	0.80	-0.7 $\pm$ 17.5	-
971	01-4-2000	3	10	0.85	1.00	P	0.71	28.5 $\pm$ 2.3	-12.52 $\pm$ 0.05
980	31-3-2000	3	10	0.80	1.00	P	0.86	40.2 $\pm$ 6.3	-12.65 $\pm$ 0.06
989	24-4-2001	3	7	0.82	1.11	P	0.77	2.8 $\pm$ 7.3	-14.63 $\pm$ 0.82
1011	24-4-2001	3	7	0.83	1.11	P	0.70	13.1 $\pm$ 3.5	-13.27 $\pm$ 0.08
1091	24-4-2001	3	5	0.85	1.15	P	0.71	58.6 $\pm$ 2.1	-12.33 $\pm$ 0.04
1118	20-4-2001	3	5	0.83	1.15	C	0.70	17.3 $\pm$ 2.0	-
1126	19-4-1999	4	5	0.83	1.10	P	0.74	10.7 $\pm$ 4.5	-12.55 $\pm$ 0.13
1193	23-4-2001	3	5	0.80	1.11	P	0.57	30.5 $\pm$ 2.2	-12.58 $\pm$ 0.05	30(11)
1249	23-4-2001	4	5	0.63	1.08	P	0.60	192.3 $\pm$ 58 $\dagger\dagger$	-14.07 $\pm$ 0.06 $\dagger\dagger$
1290	31-3-2000	3	10	0.80	1.00	P	0.89	29.7 $\pm$ 1.0	-12.09 $\pm$ 0.04

Table 2: continued.
Virgo

VCC Date N T R(H $\alpha$ ) n Phot K $EW ({\rm H}\alpha)$ $F({\rm H}\alpha)$ $EW ({\rm H}\alpha)$ (ref) $F({\rm H}\alpha)$ (ref)

Å $\rm erg~cm^{-2}~s^{-1}$ Å $\rm erg~cm^{-2}~s^{-1}$

(1) (2) (3) (4) (5) (6) (7) (8) (9) (10) (11) (12)

1330 20-4-2001 3 5 0.83 1.18 P 0.76 3.7 $\pm$ 1.4 -12.68 $\pm$ 0.13 6(11)

1356 20-4-1999 3 5 0.85 1.10 P 0.76 43.0 $\pm$ 8.1 -13.05 $\pm$ 0.07 50(11)

1379 24-4-2001 3 5 0.84 1.05 P 0.70 36.4 $\pm$ 3.0 -11.92 $\pm$ 0.05 34(11), -12.06(9)

1393 21-4-2001 3 5 0.81 1.16 T 0.81 37.7 $\pm$ 2.5 -12.30 $\pm$ 0.05

1410 18-4-1999 3 5 0.83 1.10 P 0.65 34.9 $\pm$ 9.3 -12.71 $\pm$ 0.07 28(11)

1411 21-4-2001 3 10 0.83 1.02 P 0.70 2.1 $\pm$ 2.4 -14.37 $\pm$ 0.29

1426 23-4-2001 3 5 0.85 1.08 P 0.71 5.9 $\pm$ 7.4 -13.93 $\pm$ 0.35

1429 21-4-2001 3 10 0.73 1.02 P 1.00 45.3 $\pm$ 0.4 -13.04 $\pm$ 0.04

1442 02-4-2000 3 10 0.83 1.00 P 0.75 18.2 $\pm$ 2.9 -12.97 $\pm$ 0.06

1491 18-4-1999 3 4 0.82 1.10 P 0.78 -0.5 $\pm$ 6.4 - 0(11)

1508 24-4-2001 3 5 0.85 1.12 P 0.71 39.7 $\pm$ 5.5 -11.78 $\pm$ 0.06 -11.75(9)

1532 20-4-2001 3 5 0.80 1.17 P 0.86 17.3 $\pm$ 2.5 -12.55 $\pm$ 0.07

1557 02-4-2000 3 10 0.83 1.00 P 0.76 23.5 $\pm$ 2.3 -12.74 $\pm$ 0.05

1581 23-4-2001 3 10 0.81 1.18 P 0.80 5.8 $\pm$ 3.5 -13.46 $\pm$ 0.20 -13.24(4)

1624 02-4-2000 3 7 0.85 1.00 P 0.71 11.5 $\pm$ 2.3 -12.82 $\pm$ 0.07

1654 24-4-2001 3 7 0.81 1.18 P 0.80 19.4 $\pm$ 2.5 -13.57 $\pm$ 0.06

1675 20-4-1999 3 5 0.83 1.10 P 0.68 4.2 $\pm$ 10.3 -13.85 $\pm$ 0.68 13(11)

1686 17-4-1999 4 7 0.85 1.10 P 0.68 43.5 $\pm$ 12.2 -12.17 $\pm$ 0.08 56(11)

1699 21-4-2001 3 7 0.83 1.12 P 0.73 24.0 $\pm$ 4.2 -12.85 $\pm$ 0.06 -12.33(4)

1757 01-4-2000 3 5 0.83 1.00 P 0.70 7.5 $\pm$ 4.8 -12.98 $\pm$ 0.19 8(11)

1758 18-4-1999 3 5 0.83 1.10 P 0.76 17.0 $\pm$ 3.3 -13.07 $\pm$ 0.07

1789 21-4-2001 3 7 0.83 1.12 P 0.73 16.4 $\pm$ 3.6 -13.25 $\pm$ 0.08

1791 24-4-2001 3 5 0.81 1.13 P 0.84 71.6 $\pm$ 3.5 -12.42 $\pm$ 0.05 80(11)

1918 21-4-2001 3 7 0.84 1.13 P 0.71 14.6 $\pm$ 8.1 -13.90 $\pm$ 0.15

1923 20-4-2001 3 5 0.80 1.15 P 0.68 36.0 $\pm$ 3.6 -11.93 $\pm$ 0.05

2023 19-4-2001 3 5 0.84 1.10 P 0.70 27.5 $\pm$ 5.4 -12.56 $\pm$ 0.07

**Table 2:** continued.
Virgo
VCC	Date	N	T	R(H $\alpha$ )	n	Phot	K	$EW ({\rm H}\alpha)$	$F({\rm H}\alpha)$	$EW ({\rm H}\alpha)$ (ref)	$F({\rm H}\alpha)$ (ref)
								Å	$\rm erg~cm^{-2}~s^{-1}$	Å	$\rm erg~cm^{-2}~s^{-1}$
(1)	(2)	(3)	(4)	(5)	(6)	(7)	(8)	(9)	(10)	(11)	(12)
1330	20-4-2001	3	5	0.83	1.18	P	0.76	3.7 $\pm$ 1.4	-12.68 $\pm$ 0.13	6(11)
1356	20-4-1999	3	5	0.85	1.10	P	0.76	43.0 $\pm$ 8.1	-13.05 $\pm$ 0.07	50(11)
1379	24-4-2001	3	5	0.84	1.05	P	0.70	36.4 $\pm$ 3.0	-11.92 $\pm$ 0.05	34(11),	-12.06(9)
1393	21-4-2001	3	5	0.81	1.16	T	0.81	37.7 $\pm$ 2.5	-12.30 $\pm$ 0.05
1410	18-4-1999	3	5	0.83	1.10	P	0.65	34.9 $\pm$ 9.3	-12.71 $\pm$ 0.07	28(11)
1411	21-4-2001	3	10	0.83	1.02	P	0.70	2.1 $\pm$ 2.4	-14.37 $\pm$ 0.29
1426	23-4-2001	3	5	0.85	1.08	P	0.71	5.9 $\pm$ 7.4	-13.93 $\pm$ 0.35
1429	21-4-2001	3	10	0.73	1.02	P	1.00	45.3 $\pm$ 0.4	-13.04 $\pm$ 0.04
1442	02-4-2000	3	10	0.83	1.00	P	0.75	18.2 $\pm$ 2.9	-12.97 $\pm$ 0.06
1491	18-4-1999	3	4	0.82	1.10	P	0.78	-0.5 $\pm$ 6.4	-	0(11)
1508	24-4-2001	3	5	0.85	1.12	P	0.71	39.7 $\pm$ 5.5	-11.78 $\pm$ 0.06		-11.75(9)
1532	20-4-2001	3	5	0.80	1.17	P	0.86	17.3 $\pm$ 2.5	-12.55 $\pm$ 0.07
1557	02-4-2000	3	10	0.83	1.00	P	0.76	23.5 $\pm$ 2.3	-12.74 $\pm$ 0.05
1581	23-4-2001	3	10	0.81	1.18	P	0.80	5.8 $\pm$ 3.5	-13.46 $\pm$ 0.20		-13.24(4)
1624	02-4-2000	3	7	0.85	1.00	P	0.71	11.5 $\pm$ 2.3	-12.82 $\pm$ 0.07
1654	24-4-2001	3	7	0.81	1.18	P	0.80	19.4 $\pm$ 2.5	-13.57 $\pm$ 0.06
1675	20-4-1999	3	5	0.83	1.10	P	0.68	4.2 $\pm$ 10.3	-13.85 $\pm$ 0.68	13(11)
1686	17-4-1999	4	7	0.85	1.10	P	0.68	43.5 $\pm$ 12.2	-12.17 $\pm$ 0.08	56(11)
1699	21-4-2001	3	7	0.83	1.12	P	0.73	24.0 $\pm$ 4.2	-12.85 $\pm$ 0.06		-12.33(4)
1757	01-4-2000	3	5	0.83	1.00	P	0.70	7.5 $\pm$ 4.8	-12.98 $\pm$ 0.19	8(11)
1758	18-4-1999	3	5	0.83	1.10	P	0.76	17.0 $\pm$ 3.3	-13.07 $\pm$ 0.07
1789	21-4-2001	3	7	0.83	1.12	P	0.73	16.4 $\pm$ 3.6	-13.25 $\pm$ 0.08
1791	24-4-2001	3	5	0.81	1.13	P	0.84	71.6 $\pm$ 3.5	-12.42 $\pm$ 0.05	80(11)
1918	21-4-2001	3	7	0.84	1.13	P	0.71	14.6 $\pm$ 8.1	-13.90 $\pm$ 0.15
1923	20-4-2001	3	5	0.80	1.15	P	0.68	36.0 $\pm$ 3.6	-11.93 $\pm$ 0.05
2023	19-4-2001	3	5	0.84	1.10	P	0.70	27.5 $\pm$ 5.4	-12.56 $\pm$ 0.07

Table 2: continued.
Coma/A1367 supercluster.

CGCG Date N T R(Ha) n Phot K $EW ({\rm H}\alpha)$ $F({\rm H}\alpha)$ $EW ({\rm H}\alpha)$ (ref) $F({\rm H}\alpha)$ (ref)

Å $\rm erg~cm^{-2}~s^{-1}$ Å $\rm erg~cm^{-2}~s^{-1}$

(1) (2) (3) (4) (5) (6) (7) (8) (9) (10) (11) (12)

97005 18-4-1999 3 7 0.73 1.10 P 1.00 39.0 $\pm$ 0.1 -12.86 $\pm$ 0.04

97023 21-4-2001 3 5 0.73 1.10 P 1.00 1.0 $\pm$ 0.9 -14.30 $\pm$ 0.38

97026 21-4-2001 3 5 0.73 1.11 P 1.00 83.1 $\pm$ 0.8 -12.23 $\pm$ 0.04 88(2) - 12.26(2)

97027 21-4-2001 3 5 0.77 1.11 P 1.00 22.0 $\pm$ 0.9 -12.89 $\pm$ 0.05

97063 22-4-2001 3 5 0.72 1.11 P 1.00 22.1 $\pm$ 1.6 -13.47 $\pm$ 0.05 12(10) - 13.69(10)

97064 22-4-2001 3 5 0.71 1.13 P 1.00 0.5 $\pm$ 1.1 -14.82 $\pm$ 0.95

97068 22-4-2001 3 5 0.71 1.13 P 1.00 40.6 $\pm$ 1.6 -12.50 $\pm$ 0.05 41(7) - 12.6(7)

97076 31-3-2000 3 10 0.77 1.13 P 1.00 1.0 $\pm$ 0.7 -14.28 $\pm$ 0.31

97079 01-4-2000 3 7 0.77 1.00 P 1.00 128.9 $\pm$ 3.0 -12.66 $\pm$ 0.04 137(8) - 12.66(8)

97130 21-4-1999 3 5 0.77 1.00 P 1.00 - 2.0 $\pm$ 0.1 -

97134 21-4-1999 3 5 0.74 1.10 P 1.00 - 2.1 $\pm$ 0.0 -

97135 21-4-1999 3 5 0.74 1.10 P 1.00 - 1.2 $\pm$ 0.0 -

101033 01-4-2000 3 7 0.77 1.10 P 1.00 16.2 $\pm$ 1.2 -13.54 $\pm$ 0.05

101049 17-4-1999 4 5 0.76 1.00 P 1.00 9.9 $\pm$ 0.2 -13.08 $\pm$ 0.04

127026 19-4-1999 4 5 0.77 1.10 P 1.00 14.7 $\pm$ 0.2 -12.90 $\pm$ 0.04

127061 19-4-1999 4 5 0.70 1.10 P 1.00 29.4 $\pm$ 0.5 -12.97 $\pm$ 0.04

130005 21-4-1999 3 5 0.77 1.10 P 1.00 40.5 $\pm$ 0.2 -12.89 $\pm$ 0.04

130025 01-4-2000 3 10 0.77 1.10 P 1.00 0.5 $\pm$ 1.1 -14.46 $\pm$ 0.92

130026 20-4-2001 2 5 0.77 1.00 P 1.00 17.6 $\pm$ 5.0 -12.87 $\pm$ 0.12

130028 20-4-2001 2 5 0.77 1.14 P 1.00 2.2 $\pm$ 1.7 -13.73 $\pm$ 0.33

130029 20-4-2001 2 5 0.77 1.14 P 1.00 54.4 $\pm$ 2.9 -12.51 $\pm$ 0.05

131008 31-3-2000 3 10 0.71 1.14 P 1.00 27.0 $\pm$ 0.3 -12.87 $\pm$ 0.04

157062 21-4-1999 3 5 0.77 1.00 P 1.00 77.0 $\pm$ 0.3 -12.92 $\pm$ 0.04

159037 24-4-2001 2 5 0.75 1.28 C 1.00 44.4 $\pm$ 1.3

159071 20-4-1999 2 5 0.77 1.10 P 1.00 32.2 $\pm$ 0.3 -13.04 $\pm$ 0.04

159072N 19-4-2001 3 5 0.77 1.09 P 1.00 6.1 $\pm$ 0.8 -13.11 $\pm$ 0.07 18(3) $\dagger$

159072S 19-4-2001 3 5 0.77 1.09 P 1.00 11.8 $\pm$ 1.0 -12.82 $\pm$ 0.06 12(3) $\dagger$

160001 21-4-2001 3 5 0.71 1.09 T 1.00 14.6 $\pm$ 1.4 -13.37 $\pm$ 0.06

160009 21-4-1999 3 5 0.76 1.10 P 1.00 5.6 $\pm$ 0.1 -13.51 $\pm$ 0.04

160108 18-4-1999 3 5 0.70 1.10 P 1.00 37.4 $\pm$ 0.2 -13.05 $\pm$ 0.04

160110 18-4-1999 3 5 0.60 1.10 P 1.00 - 1.8 $\pm$ 0.1 -

160111 18-4-1999 3 5 0.76 1.10 P 1.00 1.2 $\pm$ 0.1 -14.39 $\pm$ 0.05

160141 18-4-1999 3 5 0.75 1.10 P 1.00 30.2 $\pm$ 0.2 -13.13 $\pm$ 0.04

161040 22-4-2001 3 5 0.75 1.16 P 1.00 20.5 $\pm$ 1.6 -13.38 $\pm$ 0.05

161052 19-4-2001 3 5 0.77 1.13 P 1.00 44.2 $\pm$ 0.3 -12.72 $\pm$ 0.04 48(6) - 12.67(6)

161054 24-4-2001 3 5 0.77 1.03 P 1.00 42.5 $\pm$ 1.6 -12.93 $\pm$ 0.05

A2197/A2199

224003 24-4-2001 3 5 0.66 1.03 P 1.00 10.1 $\pm$ 4.3 -13.39 $\pm$ 0.18

224012 19-4-1999 4 5 0.70 1.10 P 1.00 35.8 $\pm$ 0.2 -13.08 $\pm$ 0.04

224017 23-4-2001 3 5 0.68 1.11 P 1.00 3.8 $\pm$ 0.7 -13.51 $\pm$ 0.09

224026 17-4-1999 3 5 0.70 1.10 P 1.00 34.3 $\pm$ 0.3 -12.71 $\pm$ 0.04

224035 18-4-1999 3 5 0.70 1.10 P 1.00 5.3 $\pm$ 0.2 -13.35 $\pm$ 0.05

224039 23-4-2001 3 5 0.58 1.14 P 1.00 3.5 $\pm$ 1.0 -12.86 $\pm$ 0.13

224040 22-4-2001 3 5 0.63 1.14 P 1.00 2.0 $\pm$ 1.0 -13.82 $\pm$ 0.22

224045 23-4-2001 3 5 0.68 1.13 P 1.00 30.8 $\pm$ 2.2 -13.27 $\pm$ 0.05

224057 20-4-1999 3 5 0.74 1.10 P 1.00 20.7 $\pm$ 0.3 -12.97 $\pm$ 0.04

224059 21-4-2001 3 5 0.66 0.95 C 1.00 4.2 $\pm$ 1.8 -

224066 23-4-2001 3 5 0.64 1.10 P 1.00 6.9 $\pm$ 2.3 -13.21 $\pm$ 0.15

224070 20-4-1999 2 5 0.70 1.10 C 1.00 12.8 $\pm$ 0.2 -

**Table 2:** continued.
Coma/A1367 supercluster.
CGCG	Date	N	T	R(Ha)	n	Phot	K	$EW ({\rm H}\alpha)$	$F({\rm H}\alpha)$	$EW ({\rm H}\alpha)$ (ref)	$F({\rm H}\alpha)$ (ref)
								Å	$\rm erg~cm^{-2}~s^{-1}$	Å	$\rm erg~cm^{-2}~s^{-1}$
(1)	(2)	(3)	(4)	(5)	(6)	(7)	(8)	(9)	(10)	(11)	(12)
97005	18-4-1999	3	7	0.73	1.10	P	1.00	39.0 $\pm$ 0.1	-12.86 $\pm$ 0.04
97023	21-4-2001	3	5	0.73	1.10	P	1.00	1.0 $\pm$ 0.9	-14.30 $\pm$ 0.38
97026	21-4-2001	3	5	0.73	1.11	P	1.00	83.1 $\pm$ 0.8	-12.23 $\pm$ 0.04	88(2)	- 12.26(2)
97027	21-4-2001	3	5	0.77	1.11	P	1.00	22.0 $\pm$ 0.9	-12.89 $\pm$ 0.05
97063	22-4-2001	3	5	0.72	1.11	P	1.00	22.1 $\pm$ 1.6	-13.47 $\pm$ 0.05	12(10)	- 13.69(10)
97064	22-4-2001	3	5	0.71	1.13	P	1.00	0.5 $\pm$ 1.1	-14.82 $\pm$ 0.95
97068	22-4-2001	3	5	0.71	1.13	P	1.00	40.6 $\pm$ 1.6	-12.50 $\pm$ 0.05	41(7)	- 12.6(7)
97076	31-3-2000	3	10	0.77	1.13	P	1.00	1.0 $\pm$ 0.7	-14.28 $\pm$ 0.31
97079	01-4-2000	3	7	0.77	1.00	P	1.00	128.9 $\pm$ 3.0	-12.66 $\pm$ 0.04	137(8)	- 12.66(8)
97130	21-4-1999	3	5	0.77	1.00	P	1.00	- 2.0 $\pm$ 0.1	-
97134	21-4-1999	3	5	0.74	1.10	P	1.00	- 2.1 $\pm$ 0.0	-
97135	21-4-1999	3	5	0.74	1.10	P	1.00	- 1.2 $\pm$ 0.0	-
101033	01-4-2000	3	7	0.77	1.10	P	1.00	16.2 $\pm$ 1.2	-13.54 $\pm$ 0.05
101049	17-4-1999	4	5	0.76	1.00	P	1.00	9.9 $\pm$ 0.2	-13.08 $\pm$ 0.04
127026	19-4-1999	4	5	0.77	1.10	P	1.00	14.7 $\pm$ 0.2	-12.90 $\pm$ 0.04
127061	19-4-1999	4	5	0.70	1.10	P	1.00	29.4 $\pm$ 0.5	-12.97 $\pm$ 0.04
130005	21-4-1999	3	5	0.77	1.10	P	1.00	40.5 $\pm$ 0.2	-12.89 $\pm$ 0.04
130025	01-4-2000	3	10	0.77	1.10	P	1.00	0.5 $\pm$ 1.1	-14.46 $\pm$ 0.92
130026	20-4-2001	2	5	0.77	1.00	P	1.00	17.6 $\pm$ 5.0	-12.87 $\pm$ 0.12
130028	20-4-2001	2	5	0.77	1.14	P	1.00	2.2 $\pm$ 1.7	-13.73 $\pm$ 0.33
130029	20-4-2001	2	5	0.77	1.14	P	1.00	54.4 $\pm$ 2.9	-12.51 $\pm$ 0.05
131008	31-3-2000	3	10	0.71	1.14	P	1.00	27.0 $\pm$ 0.3	-12.87 $\pm$ 0.04
157062	21-4-1999	3	5	0.77	1.00	P	1.00	77.0 $\pm$ 0.3	-12.92 $\pm$ 0.04
159037	24-4-2001	2	5	0.75	1.28	C	1.00	44.4 $\pm$ 1.3
159071	20-4-1999	2	5	0.77	1.10	P	1.00	32.2 $\pm$ 0.3	-13.04 $\pm$ 0.04
159072N	19-4-2001	3	5	0.77	1.09	P	1.00	6.1 $\pm$ 0.8	-13.11 $\pm$ 0.07	18(3) $\dagger$
159072S	19-4-2001	3	5	0.77	1.09	P	1.00	11.8 $\pm$ 1.0	-12.82 $\pm$ 0.06	12(3) $\dagger$
160001	21-4-2001	3	5	0.71	1.09	T	1.00	14.6 $\pm$ 1.4	-13.37 $\pm$ 0.06
160009	21-4-1999	3	5	0.76	1.10	P	1.00	5.6 $\pm$ 0.1	-13.51 $\pm$ 0.04
160108	18-4-1999	3	5	0.70	1.10	P	1.00	37.4 $\pm$ 0.2	-13.05 $\pm$ 0.04
160110	18-4-1999	3	5	0.60	1.10	P	1.00	- 1.8 $\pm$ 0.1	-
160111	18-4-1999	3	5	0.76	1.10	P	1.00	1.2 $\pm$ 0.1	-14.39 $\pm$ 0.05
160141	18-4-1999	3	5	0.75	1.10	P	1.00	30.2 $\pm$ 0.2	-13.13 $\pm$ 0.04
161040	22-4-2001	3	5	0.75	1.16	P	1.00	20.5 $\pm$ 1.6	-13.38 $\pm$ 0.05
161052	19-4-2001	3	5	0.77	1.13	P	1.00	44.2 $\pm$ 0.3	-12.72 $\pm$ 0.04	48(6)	- 12.67(6)
161054	24-4-2001	3	5	0.77	1.03	P	1.00	42.5 $\pm$ 1.6	-12.93 $\pm$ 0.05
A2197/A2199
224003	24-4-2001	3	5	0.66	1.03	P	1.00	10.1 $\pm$ 4.3	-13.39 $\pm$ 0.18
224012	19-4-1999	4	5	0.70	1.10	P	1.00	35.8 $\pm$ 0.2	-13.08 $\pm$ 0.04
224017	23-4-2001	3	5	0.68	1.11	P	1.00	3.8 $\pm$ 0.7	-13.51 $\pm$ 0.09
224026	17-4-1999	3	5	0.70	1.10	P	1.00	34.3 $\pm$ 0.3	-12.71 $\pm$ 0.04
224035	18-4-1999	3	5	0.70	1.10	P	1.00	5.3 $\pm$ 0.2	-13.35 $\pm$ 0.05
224039	23-4-2001	3	5	0.58	1.14	P	1.00	3.5 $\pm$ 1.0	-12.86 $\pm$ 0.13
224040	22-4-2001	3	5	0.63	1.14	P	1.00	2.0 $\pm$ 1.0	-13.82 $\pm$ 0.22
224045	23-4-2001	3	5	0.68	1.13	P	1.00	30.8 $\pm$ 2.2	-13.27 $\pm$ 0.05
224057	20-4-1999	3	5	0.74	1.10	P	1.00	20.7 $\pm$ 0.3	-12.97 $\pm$ 0.04
224059	21-4-2001	3	5	0.66	0.95	C	1.00	4.2 $\pm$ 1.8	-
224066	23-4-2001	3	5	0.64	1.10	P	1.00	6.9 $\pm$ 2.3	-13.21 $\pm$ 0.15
224070	20-4-1999	2	5	0.70	1.10	C	1.00	12.8 $\pm$ 0.2	-

References: (1) Kennicutt & Kent (1983); (2) Kennicutt et al. (1984); (3) Keel et al. (1985); $\dagger$ from nuclear spectroscopy; (4) Gallagher & Hunter (1989); (5) Romanishin (1990); (6) Gavazzi et al. (1991); (7) Moss et al. (1998); (8) Gavazzi et al. (1998); (9) Koopmann et al. (2001); (10) Iglesias et al. (2002); (11) Gavazzi et al. (2002b), from drift-scan spectroscopy.

5 Results

The results of the present observations are listed in Table 2 as follows:

Column 1: galaxy designation;
Column 2: date of the observation;
Column 3: number of combined exposures;
Column 4: integration times in minutes of the individual exposures;
Column 5: transmissivity of the ON-band filter at the redshifted H $\alpha$ line;
Column 6: Normalization factor of the OFF-band frame;
Column 7: a flag indicating whether the frame was taken under photometric (P) or Transparent (T) conditions or through light cyrrus (C);
Column 8: correction factor for the contamination by the two lines of [SII] (see Eq. (3));
Column 9: H $\alpha$ +[NII] equivalent width and error, in Å;
Column 10: Logarithm of the H $\alpha$ +[NII] flux, in $\rm erg~cm^{-2}~s^{-1}$ . This quantity is given if the flag in Col. 7 is P or T;
Column 11 and 12: H $\alpha$ +[NII] equivalent width and flux from the literature, with references.

Galaxies with substantial H $\alpha$ structure are shown in Fig. 4. The OFF-frames are displayed with contours superposed to the NET-frames, given in grey-scale.

5.1 Comparison with the literature

Few galaxies measured in this work have independent imaging measurements in the literature (see Table 2). However 24 objects were spectroscopically observed (Gavazzi et al. 2002b) in the "drift-scan'' mode, with the slit sliding over most of the galaxy surface. Spectra taken in this way are representative of the mean galaxy, unlike most long slit observations which are dominated by the nuclear light. ${\rm H}\alpha +[{\rm NII}]$ equivalent widths from spectroscopy are thus directly comparable with our imaging data, as illustrated in Fig. 3, showing a satisfactory agreement. The average differences between our flux and equivalent width estimates and those in the literature are: ${\rm H}\alpha+[{\rm NII}] EW_{\rm TW} - {\rm H}\alpha+[{\rm NII}] EW_{\rm L} = -5.2 \pm 2.9 ~(\rm\AA)$ and $-{\rm log}F({\rm H}\alpha+[{\rm NII}])_{\rm TW} + {\rm log}F({\rm H}\alpha+[{\rm NII}])_{\rm L} = -0.12 \pm 0.1 ~(\rm erg~ cm^{-2}~s^{-1})$

$\begin{figure} \par\includegraphics[width=7.8cm,clip]{ms2157f3a.ps}\par\includegraphics[width=7.8cm,clip]{ms2157f3b.ps}\end{figure}$	Figure 3: comparison of the ${\rm H}\alpha +[{\rm NII}] EW$ (top) and fluxes (bottom) determined in this work with the ones taken from the literature.
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6 Summary

H $\alpha$ +[NII] surface photometry of 125 galaxies obtained with the 2.1 m SPM telescope is presented. We derive H $\alpha$ +[NII] fluxes and equivalent widths and we show the images of the detected galaxies. These observations are aimed at completing the H $\alpha$ survey of galaxies in the Virgo cluster and in other clusters, as well as of relatively isolated objects in the Coma supercluster, thus spanning a large range of morphological type, luminosity and environmental conditions. Combining the results of the present work with those given in Papers II and III of this series and with the ones available from the literature 235/312 (75%) late-type Virgo cluster members have H $\alpha$ measurements, as well as 177/256 (69%) late-type members to the Coma supercluster. The analysis of the current (< $\rm 10^7~yr$ ) massive (> $5~M_\odot$ ) star formation properties of galaxies in the above regions will be carried out in the forthcoming Paper IV using the statistically significant set of observations here presented.

7 Comments on individual objects

VCC 1429 is in the background of the Virgo cluster (V = 7506 km s^-1). It was serendipitously observed in the field of VCC 1426 (with inverted filters).
VCC 1249 this galaxy (UGC 7636) was observed spectroscopically by Lee et al. (2000) who discovered an HII region associated with this galaxy but not spatially coincident with it, as it is found in the envelope of the giant elliptical galaxy M 49. We do not detect any H $\alpha$ emission from VCC 1249 itself, but we detect the HII region (marked with an arrow in Fig. 4). The flux and EW quoted in Table 2 ( $\dagger\dagger$ ) refer to the HII region only.

Acknowledgements

We thank the night operators for their assistence during the observations and the SPM TAC for the generous time allocations. A.B. acknowledges financial support from the French GdR Galaxies. This research has made use of the NASA/IPAC Extragalactic Database (NED) which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration. L. Carrasco research is supported by CONACYT research grant G28586-E.

References

Binggeli, B., Sandage, A., & Tammann, G. 1985, AJ, 90, 1681 (VCC) In the text NASA ADS
Binggeli, B., Popescu, C., & Tammann, G. 1993, A&AS, 98, 275 In the text NASA ADS
Boselli, A., & Gavazzi, G. 2002, A&A, 386, 124 (Paper II) In the text
Boselli, A., Iglesias-Páramo, J., Vilchez, J., & Gavazzi, G. 2002, A&A, 386, 134 (Paper III) In the text
Gallagher, J., & Hunter, D. 1989, AJ, 98, 806 In the text NASA ADS
Gavazzi, G., Boselli, A., & Kennicutt, R. 1991, AJ, 101, 1207 In the text NASA ADS
Gavazzi, G., & Boselli, A. 1996, Astro. Lett. & Comm., 35, 1 In the text
Gavazzi, G., Catinella, B., Carrasco, L., Boselli, A., & Contursi, A. 1998, AJ, 115, 1745 In the text NASA ADS
Gavazzi, G., et al. 2002a, in preparation (Paper IV) In the text
Gavazzi, G., Boselli, A., Scodeggio, M., Pierini, D., & Belsole, E. 1999a, MNRAS, 304, 595 In the text NASA ADS
Gavazzi, G., Carrasco, L., & Galli, R. 1999b, A&AS, 136, 227 In the text NASA ADS
Gavazzi, G., Franzetti, P., Scodeggio, M., Boselli, A., & Pierini, D. 2000, A&A, 361, 863 In the text NASA ADS
Gavazzi, G., et al. 2002b, in preparation (Spectra) In the text
Giovanelli, R., & Haynes, M. 1985, ApJ, 292, 404 In the text NASA ADS
Iglesias, J., Boselli, A., Cortese, L., Vilchez, J., & Gavazzi, G. 2002, A&A, submitted In the text
Keel, W., Kennicutt, R., Hummel, E., & van der Hulst, J. 1985, AJ, 90, 708 In the text NASA ADS
Kennicutt, R. 1983, AJ, 88, 483 In the text NASA ADS
Kennicutt, R. 1998, ARA&A, 36, 189 In the text NASA ADS
Kennicutt, R., Bothun, G., & Schommer, R. 1984, AJ, 89, 1279 In the text NASA ADS
Kennicutt, R., & Kent, S. 1983, AJ, 88, 1094 In the text NASA ADS
Koopmann, R., Kenney, J., & Joung, J. 2001, ApJS, 135, 125 In the text NASA ADS
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Online Material

$\begin{figure} \par\includegraphics[width=14.5cm,clip]{ms2157f4_1r.eps} \end{figure}$	Figure 4: Galaxies with substantial ${\rm H}\alpha +[{\rm NII}]$ structure. The NET (ON-OFF) frames are given with grey-scale, with superposed contours of the OFF frames. J2000 celestial coordinates are given.
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$\begin{figure} \par\includegraphics[width=14.5cm,clip]{ms2157f4_2.eps} \end{figure}$	Figure 4: continued.
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H surface photometry of galaxies in the Virgo cluster I. Observations with the San Pedro Martir 2.1 m telescope,

H $\alpha$ surface photometry of galaxies in the Virgo cluster
I. Observations with the San Pedro Martir 2.1 m telescope^,