A&A 386, 124-133 (2002)
DOI: 10.1051/0004-6361:20020215

H$\alpha $ surface photometry of galaxies in the Virgo cluster

II. Observations with the OHP and Calar Alto 1.2 m telescopes[*],[*]

A. Boselli 1 - G. Gavazzi 2


1 - Laboratoire d'Astronomie Spatiale, Traverse du Siphon, 13376 Marseille Cedex 12, France
2 - Università degli Studi di Milano-Bicocca, Piazza delle scienze 3, 20126 Milano, Italy

Received 3 December 2001 / Accepted 5 February 2002

Abstract
We present H$\alpha $ line imaging observations of 122 galaxies obtained with the 1.20 m telescopes of the Observatoire de Haute Provence (OHP) and of Calar Alto. The observed galaxies are mostly Virgo cluster members (95), along with 10 objects in the Coma/A1367 supercluster, 6 in the clusters A2197 and A2199, and 11 nearby galaxies taken as fillers. H$\alpha $+[NII] fluxes and equivalent widths, as well as images of all the detected targets, are presented.

Key words: galaxies: photometry - galaxies: fundamental parameters


1 Introduction

The star-formation activity is a fundamental parameter in the study of the formation and evolution of galaxies. Being linearly related to the number of young O-B massive stars, the H$\alpha $ line emission is the most direct tracer of star formation in normal, late-type galaxies (Kennicutt 1998). In order to study the star formation history of objects of different mass, luminosity, type and belonging to different environments (cluster, field), we are gathering H$\alpha $ data for a large sample of galaxies in the nearby Universe for which data at other wavelengths are already available. We focused our attention on the closest rich cluster of galaxies, the Virgo cluster, for which H$\alpha $ data of galaxies spanning the whole range in luminosity and morphological type, from giant early spirals to dwarfs irregulars and BCDs, can be easely obtained with 2 m class telescopes.

In this paper we present new H$\alpha $ surface photometry of late-type galaxies in the Virgo cluster obtained with the 1.20 m telescope at the Observatoire de Haute Provence and with the 1.23 m telescope at Calar Alto. In a companion paper (Gavazzi et al. 2002, Paper I), we present similar observations of lower luminosity Virgo galaxies carried out with the San Pedro Martir 2.1 m telescope. In a third paper (Boselli et al. 2002, Paper III) we present H$\alpha $ observations of blue compact galaxies carried out at the INT and NOT telescopes in La Palma. The data were jointly discussed in Boselli et al. (2001), Boissier et al. (2001) and will be further discussed in a future communication (Gavazzi et al. in preparation, Paper IV).

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 Bmagnitude $m_{\rm pg} = 18.0$. The targets were selected according to the following criteria:

-
$m_{\rm pg}$ < 16.0;

-
Hubble type later than S0a;

-
classified as cluster members, possible members or belonging to the W, W', M clouds or to the southern extension (Binggeli et al. 1985; 1993).
Among the 312 late-type Virgo cluster members matching these criteria, 235 objects (75%) either included in the present work or in Papers I and III have an H$\alpha $ measurement. Moreover limiting to the ISO sample described in Boselli et al. (1997a), 86 out 88 galaxies (98%) have H$\alpha $ data. Given the large field of view of the detectors, some galaxies not matching the selection criteria were serendipitously observed in the fields of other targets.

Few galaxies in the Coma/A1367 supercluster and in A2197 and A2199 were also observed as fillers, as well as a few nearby objects.

The target galaxies, as well as the serendipitously observed objects, are listed in Table 1, arranged as follow:

For the nearby galaxies, Table 2 lists the relevant informations taken from NED[*].

   
Table 1: The target galaxies.

Virgo		                            

VCC		 NGC/IC UGC RA(1950) 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)

67		 3044 7216 121015.5 141515.0 2.26 0.79 -183 M 32 4.66 Sc 13.98 13.62 11.27
87 - - 121108.2 154354.0 1.45 0.72 -134 N 17 5.17 Sm 15.00 15.27 13.64
92 4192 7231 121115.5 151042.0 9.78 2.60 -135 N 17 4.84 Sb 10.92 9.87 7.07
145 4206 7260 121244.0 131807.0 5.10 0.85 702 N 17 3.84 Sc 12.77 11.70 9.62
152 4207 7268 121257.3 95149.0 1.96 0.89 592 N 17 4.69 Scd 13.48 12.98 9.77
159 - - 121308.4 83348.0 1.04 0.52 2584 W 32 5.54 Im 15.08 16.02 13.20
165 - - 121320.5 132937.0 1.25 0.85 255 N 17 3.73 S0 14.87 15.51 11.54
167 4216 7284 121321.5 132540.0 9.12 2.16 140 N 17 3.72 Sb 10.97 9.89 6.69
222 4235 7310 121436.7 72809.0 4.33 0.71 2410 W 32 6.19 Sa 12.62 11.72 8.73
234 4241 7319 121452.6 65804.0 3.36 1.87 2237 W 32 6.59 Sa 12.99 12.69 9.23
267 3115 7333 121526.7 65553.0 2.01 2.01 733 B 23 6.55 Sbc 13.82 14.06 10.87
307 4254 7345 121617.0 144139.0 6.15 5.60 2405 N 17 3.55 Sc 10.43 10.41 7.21
315 - - 121627.3 62220.0 1.10 0.67 1612 W 32 6.94 Sa 14.98 - -
341 4260 7361 121649.0 62234.0 3.52 1.75 1958 B 23 6.90 Sa 12.70 12.43 8.72
371 4268 7371 121713.9 53340.0 1.84 0.57 2377 W 32 7.61 S0 13.73 13.70 9.81
375 4270 7376 121715.4 54431.0 2.16 1.00 2494 W 32 7.44 S0 13.11 13.13 9.29
382 4273 7380 121722.7 53713.0 2.01 1.29 2378 W 32 7.55 Sc 12.37 12.11 9.34
386 4277 - 121730.5 53707.0 1.55 0.97 2499 W 32 7.54 Sa 14.47 14.22 10.80
408 4281 7389 121748.4 53951.0 3.36 1.16 2711 W 32 7.47 S0 12.27 12.18 7.84
446 - - 121824.6 63654.0 0.85 0.43 825 B 23 6.52 Im/BCD 15.50 - 13.40
483 4298 7412 121900.5 145301.0 3.60 2.01 1136 A 17 3.16 Sc 12.08 11.59 8.49
497 4302 7418 121910.1 145230.0 6.74 1.60 1150 A 17 3.13 Sc 12.55 11.33 8.15
524 4307 7431 121933.0 91917.0 3.95 0.72 1092 B 23 3.98 Sbc 12.79 12.08 9.52
559 4312 7442 121959.3 154852.0 5.10 1.24 153 A 17 3.74 Sab 12.56 11.92 8.99
570 4313 7445 122006.1 120442.0 5.10 1.16 1443 A 17 2.09 Sab 12.73 11.65 8.81
596 4321 7450 122022.9 160558.0 9.12 8.11 1575 A 17 3.93 Sc 10.11 9.93 6.69
608 4322 - 122029.7 161058.0 1.25 0.62 1803 A 17 3.99 dE 14.94 15.24 11.78
630 4330 7456 122044.6 113845.0 5.86 1.45 1564 A 17 2.11 Sd 13.10 12.97 9.77
634 4328 - 122048.0 160548.0 1.65 1.28 499 A 17 3.88 dE 14.14 14.46 10.94
641 - - 122055.3 60537.0 0.73 0.24 906 B 23 6.82 BCD 15.08 - 13.87
656 4343 7465 122105.9 71352.0 2.48 0.93 1014 B 23 5.72 Sb 13.14 12.73 9.34
657 4342 7466 122106.6 71954.0 1.55 0.47 714 B 23 5.62 S0 13.54 13.24 9.10
664 3258 7470 122112.1 124520.0 2.60 1.87 -427 A 17 1.73 Sc 13.50 13.36 11.98
672 4341 7472 122120.4 72300.0 1.87 0.43 934 B 23 5.56 S0 14.21 14.22 10.81
697 3267 7474 122132.7 71906.0 1.55 1.55 1231 B 23 5.60 Sc 14.17 14.03 11.05
792 4380 7503 122249.6 101738.0 3.52 1.75 971 B 23 2.73 Sab 12.36 12.02 8.55
794 - 7504 122250.4 164224.0 1.71 0.43 918 A 17 4.25 dS0 15.50 - 12.56
797 - - 122252.8 182506.0 0.68 0.45 773 A 17 5.90 dE 17.00 16.91 -
798 4382 7508 122252.8 182760.0 5.86 3.36 760 A 17 5.94 S0 10.09 10.17 6.55
801 4383 7507 122253.8 164449.0 2.60 1.29 1710 A 17 4.28 ? 12.68 12.74 9.63
836 4388 7520 122314.5 125617.0 5.10 1.24 2515 A 17 1.26 Sab 11.83 10.98 8.26
857 4394 7523 122324.3 182926.0 3.60 3.60 914 A 17 5.94 Sb 11.76 11.91 8.24
865 4396 7526 122327.5 155649.0 3.36 1.00 -124 A 17 3.48 Sc 13.02 12.24 10.33
873 4402 7528 122335.3 132320.0 3.95 1.16 234 A 17 1.36 Sc 12.56 11.74 8.58
874 4405 7529 122335.5 162728.0 1.89 1.11 1738 A 17 3.96 Sc 12.99 12.70 9.61
905 - 7537 122356.6 90853.0 2.79 2.79 1290 B 23 3.68 Sc 13.42 13.60 11.07
912 4413 7538 122400.1 125316.0 2.92 1.75 105 A 17 1.07 Sbc 12.97 12.68 9.84
916 - - 122401.1 130111.0 0.43 0.37 1349 A 17 1.10 dE 16.04 16.35 12.36
939 4411b 7546 122414.7 90940.0 3.45 3.45 1271 B 23 3.65 Sc 12.92 12.97 10.53
958 4419 7551 122424.6 151924.0 3.52 1.39 -273 A 17 2.82 Sa 12.13 11.66 8.03
979 4424 7561 122439.2 94151.0 4.33 2.16 438 B 23 3.10 Sa 12.32 12.05 9.08
984 4425 7562 122441.3 130041.0 2.99 1.00 1883 A 17 0.94 Sa 12.82 12.33 9.60
995 3371 7565 122449.3 110831.0 1.53 0.11 928 A 17 1.75 Sc 15.32 13.46 13.00
1002 4430 7566 122453.5 63220.0 3.02 2.69 1450 B 23 6.19 Sc 12.48 12.65 9.60
1003 4429 7568 122454.1 112305.0 8.12 3.52 1130 A 17 1.53 S0a 11.15 10.58 7.03
1145 4457 7609 122626.0 35051.0 2.92 2.92 884 SE 17 8.83 Sb 11.66 11.69 7.96
1182 4465 - 122651.0 81812.0 0.65 0.32 7368 back 98 4.38 Sc 15.10 15.50 -
1189 3414 7621 122656.1 70247.0 1.84 1.07 597 SE 17 5.63 Sc 13.70 13.62 11.40
1190 4469 7622 122655.5 90134.0 4.33 1.29 508 B 23 3.66 Sa 12.22 11.84 8.27
1192 4467 - 122657.8 81613.0 0.73 0.47 1474 SE 17 4.41 E 15.04 15.28 10.97
1203 - - 122704.8 81236.0 0.65 0.65 948 SE 17 4.47 S0 15.70 16.34 12.72
1205 4470 7627 122705.3 80559.0 1.84 1.15 2339 SE 17 4.58 Sc 13.04 12.81 10.22
1375 - 7668 122906.2 41256.0 4.76 3.77 1732 SE 17 8.45 Sc 12.00 11.80 11.17
1401 4501 7675 122927.5 144143.0 7.23 3.86 2284 A 17 2.05 Sbc 10.27 10.13 6.60
1412 4503 7680 122934.2 112708.0 4.33 1.71 1342 A 17 1.25 Sa 12.12 11.73 8.28
1419 4506 7682 122938.9 134143.0 2.16 1.29 737 A 17 1.08 S.. 13.64 13.59 10.38
1450 3476 7695 123010.5 141929.0 2.60 2.01 -173 A 17 1.72 Sc 13.29 13.24 10.96
1453 3478 7696 123012.8 142819.0 1.15 0.89 1949 A 17 1.86 dE 14.34 14.74 11.59
1486 3483 - 123038.1 113722.0 1.10 0.78 129 A 17 1.19 S.. 15.30 14.84 12.05
1507 - - 123056.4 40412.0 1.16 0.57 910 SE 17 8.62 Sm 15.08 - -
1540 4527 7721 123135.2 25543.0 5.86 1.87 1736 SE 17 9.77 Sb 11.32 10.63 7.27
1552 4531 7729 123144.3 132101.0 4.24 2.42 195 A 17 1.08 Sa 12.58 12.25 8.98
1555 4535 7727 123148.0 82826.0 8.33 7.43 1962 SE 17 4.28 Sc 10.51 10.66 7.64
1562 4536 7732 123153.8 22750.0 7.23 3.28 1807 SE 17 10.24 Sc 11.01 10.65 7.78
1569 3520 - 123200.3 134645.0 1.07 0.71 799 A 17 1.43 Scd 15.00 15.55 13.51
1572 - - 123201.8 25042.0 0.93 0.29 1848 SE 17 9.87 BCD 16.00 16.45 -


 
Table 1: continued.

VCC		 NGC/IC UGC RA(1950) 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)

1575		 3521 7736 123206.8 72610.0 2.00 1.41 597 SE 17 5.32 Sm 13.98 13.79 11.23
1588 4540 7742 123219.5 154937.0 2.60 1.87 1288 A 17 3.31 Scd 12.81 12.44 9.41
1673 4567 7777 123401.0 113159.0 2.92 1.87 2277 A 17 1.80 Sc 12.08 10.83 8.64
1676 4568 7776 123402.5 113050.0 5.10 1.75 2255 A 17 1.82 Sc 11.70 10.38 7.70
1678 3576 7781 123405.1 65347.0 2.16 1.87 1073 SE 17 5.94 Sd 13.70 14.46 12.47
1690 4569 7786 123418.5 132616.0 10.73 5.35 -216 A 17 1.65 Sab 10.25 9.68 7.02
1730 4580 7794 123515.9 53836.0 2.16 1.60 1032 SE 17 7.23 Sc 12.61 12.55 8.82
1760 4586 7804 123555.1 43537.0 4.33 1.16 792 SE 17 8.29 Sa 12.54 12.15 8.74
1859 4606 7839 123826.2 121109.0 5.10 2.01 1645 E 17 2.52 Sa 12.52 12.24 9.30
1868 4607 7843 123841.0 120936.0 3.95 0.78 2255 E 17 2.59 Scd 13.75 12.79 9.74
1929 4633 7874 124006.5 143748.0 2.48 1.07 291 E 17 3.48 Scd 13.77 13.16 10.75
1931 - - 124010.2 133224.0 1.26 0.70 1100 E 17 3.02 Im 15.20 - 13.04
1932 4634 7875 124010.2 143412.0 2.92 0.87 116 E 17 3.45 Sc 13.19 12.30 9.68
1941 - - 124018.6 133354.0 0.32 0.32 1213 E 17 3.06 dE 18.00 - -
1943 4639 7884 124021.5 133152.0 3.20 2.01 1048 E 17 3.06 Sb 12.19 12.12 8.90
2037 - - 124343.8 102848.0 0.88 0.38 1142 E 17 4.37 Im/BCD 15.92 16.20 12.55
2066 4694 7969 124544.0 111528.0 3.20 1.16 1181 E 17 4.49 ? 12.19 12.29 9.28
14063 4517 7694 123011.8 2316.0 11.00 2.05 1129 SE 17 12.29 Sc 12.40 10.46 7.61
71060 4746 8007 124924.6 122118.0 2.20 0.61 1779 E 17 5.16 Sd 13.30 13.42 9.87


Coma/A1367 supercluster

CGCG		 NGC/IC UGC RA(1950) Dec a b Vel Clust Dist $\theta$ Type $m_{\rm pg}$ $B_{\rm T}^0$ $H_{\rm T}$
160065 - - 125605.3 281703.0 0.90 0.82 7188 A1656 96 0.31 E 15.00 15.01 11.19
160069 3943 - 125611.5 282300.0 1.10 0.36 6827 A1656 96 0.32 S0a 15.60 14.87 11.47
160213 4858 - 125637.3 282306.2 0.51 0.43 9386 A1656 96 0.24 Pec 15.50 15.65 13.07
160214 - - 125637.0 282941.0 0.88 0.47 8028 A1656 96 0.31 S0 15.30 15.28 11.29
160215 4860 - 125639.2 282335.0 0.96 0.80 7966 A1656 96 0.23 E 14.70 14.57 10.59
160216 3955 - 125641.2 281559.0 0.71 0.58 7895 A1656 96 0.18 S0 15.60 15.45 11.49
160221 4864 - 125648.3 281446.0 1.51 0.81 6760 A1656 96 0.15 E 14.80 14.45 10.82
160222 4867 - 125650.4 281424.0 0.64 0.43 4818 A1656 96 0.15 E 15.50 15.45 11.58
161043 5131 8422 132137.4 311453.4 1.91 0.38 6638 Isol 88 6.03 Sa 14.40 13.38 10.19
161069 5187 - 132729.7 312316.7 0.90 0.77 7172 Isol 96 7.22 Sb 14.60 14.65 11.17


A2197/A2199

CGCG		 NGC/IC UGC RA(1950) Dec a b Vel Clust Dist $\theta$ Type $m_{\rm pg}$ $B_{\rm T}^0$ $H_{\rm T}$
224008 - 362 162112.6 395425.0 1.28 0.72 9628 A2199 125 1.14 Sb 15.40 14.50 10.98
224009 - 367 162133.9 400206.0 1.23 1.17 9873 A2199 125 1.11 Sb 14.60 14.28 10.93
224037N - - 162645.1 411639.0 0.80 0.70 9800 A2197 122 0.43 S.. 15.50 15.39 11.45
224037S - - 162647.9 411609.6 0.55 0.50 9489 A2197 122 0.42 S0 15.50 15.64 11.60
224038 - 407 162648.3 411938.0 0.77 0.70 8446 A2197 122 0.47 Pec 14.30 14.28 11.86
224046 - 415 162720.8 412333.0 1.14 0.91 9401 A2197 122 0.49 Sb 14.80 14.53 11.04


 

 
Table 2: The nearby galaxies.

Name 		RA(1950) Dec a b Vel Type $m_{\rm pg}$ $B_{\rm T}^0$
M51 132746.3 472710.3 11.2 6.9 463 SA(s)bcpec 8.96 8.67
M81 95127.3 691808.3 26.9 14.1 -34 SA(s)ab 7.89 7.39
M82 95143.5 695500.8 11.2 4.3 203 I0;Sbrst 9.30 8.86
M106 121629.4 473453.2 18.6 7.2 448 SAB(s)bc 9.10 8.53
NGC 925 22417.0 332116.9 10.5 5.9 553 SAB(s)d 10.69 9.97
NGC1637 43857.5 -25711.9 4.0 3.2 717 SAB(rs)c 11.47 11.25
NGC2403 73202.3 654250.7 21.9 12.3 131 SAB(s)cd 8.93 8.43
NGC2541 81101.8 491251.0 6.3 3.2 559 SA(s)cd 12.26 11.57
NGC2805 91617.0 641852.8 6.3 4.8 1730 SAB(rs)d 11.52 11.18
NGC2903 92920.3 214321.5 12.6 6.0 556 SB(s)d 9.68 9.11
NGC5195 132752.5 473132.0 5.8 4.6 465 SB0pec 10.45 10.45


3 Observations

Narrow band imaging in the H$\alpha $ emission line ( $\lambda = 6562.8$ Å) of galaxies was obtained in 1998 and 2000 at the 1.20 m Newton telescope of the Observatoire de Haute Provence (OHP; France) and in 1999 at the 1.23 m telescope of Calar Alto (Spain). The f/6 OHP telescope is equipped with a thinned TK $1024\times1024$ pixels CCD detector. The pixel size is 0.69 arcsec. At the adopted gain, the electron/adu conversion is 3.5 e-/adu, with a readout noise of 8.5 e-. The f/8 Calar Alto telescope is equipped with a SITe 2048$\times$2048 pixel CCD detector. The pixel size is 0.50 arcsec. At the adopted gain, the electron/adu conversion is 3.5 e-/adu, with a readout noise of 5.2 e-. A total of 26 nights at the OHP and 8 at Calar Alto were allocated to this project. Of these, 22 were totally or partly useful due to technical problems or weather limitations, as reported in Table 3 (logbook of the observations and CCD technical data).


 

 
Table 3: Logbook of the observations.

Telescope 		Date Nights (ass./used) CCD Pixel size
1.2 m OHP 25/2-9/3/1998 12/6 TK $1024\times1024$ 0.690
1.23 m CA 14-21/4/1999 8/4 SITe $2048 \times 2048$ 0.502
1.2 m OHP 7-12/2/2000 7/5 TK $1024\times1024$ 0.690
1.2 m OHP 6-12/3/2000 7/7 TK $1024\times1024$ 0.690


Each galaxy was observed through two narrow band interferometric filters (see Table 4), one of them including the redshifted H$\alpha $ line (ON) and the second one mesuring the red continuum near H$\alpha $ (OFF). The filters given in Table 4 are used as ON or OFF band for each target, as specified in Cols. 2 and 3 of Table 5. The flux from the [NII] emission lines at $\lambda$6548 Å  and $\lambda$ 6584 Å  is included in the ON band observations. The tipical integration time was of 30-45 min ON- and OFF-band, generally split in 3 shorter exposures. Observations were obtained during poor seeing conditions (2-4 arcsec), expecially at the OHP. The images of a few nearby galaxies have been obtained by mosaicing several frames: M 81 (6 positions), M 106 (2 positions) and NGC 2403 (5 positions).

The observations were calibrated using the standard stars Feige 34 and Hz44 from the catalogue of Massey et al. (1988). Observations of the standard stars were repeated every 2 hours, with an integration of 2 min with the telescope defocused to avoid saturation. Repeated measurements gave <0.05 mag differences, which we assume as the typical uncertainty of the photometry given in this work. Not all frames were obtained in photometric conditions. When the zero point was varying by more than 0.1 mag due to cirrus, we choose to observe only galaxies with could be calibrated a posteriori on available photometry. The determination of the H$\alpha $ equivalent width can however be achieved also in non photometric conditions using field stars to normalize the ON and OFF band images, as described in the next section and in Paper I.

4 Image analysis

The data reduction of the CCD images follows a procedure identical to the one described in previous papers of the series (Gavazzi et al. 1998 Paper I), based on IRAF/ STSDAS[*] data reduction packages. To remove the detector response each image is bias subtracted and divided by the mean of several flat field exposures obtained on the twilight sky. Calar Alto flat fielding is sometimes poor because of filter vignetting. In some cases images were fitted with a 2-D polynomial function to remove second order structures in the image. Vignetting problems, combined with generally shorter exposures, make the Calar Alto images of poorer quality with respect to the OHP ones. When three images in the same filter are available, a median combination of the realigned images allows removal of cosmic rays. For galaxies with only one available image, direct inspection of the frames allows manual cosmic rays removal. Subtraction of contaminating objects, such as nearby stars and galaxies, is done by direct editing of the frames. The sky background is determined in each frame in concentric object-free annuli around the object. 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.

Total counts in the two frames have been obtained by integrating the pixel counts over the area covered by each galaxy, as derived by the optical major and minor diameters. H$\alpha $+[NII] fluxes and equivalent widths have been determined using Eqs. (1) and (2) given in Paper I.

 

 
Table 4: The characteristics of the narrow band filters.

$\lambda$ 		$\Delta \lambda$ $R(\lambda)$ $\int R(\lambda)$d$\lambda$ Telescope
6450 45 81 37.80 1.20 m OHP
6561 48 78 38.45 1.20 m OHP
6612 55 68 40.60 1.20 m OHP
6569 113 83 101.00 1.23 m CA
6744 97 80 82.15 1.23 m CA


Equation (2) shows that once the normalization constant $n_{\rm\frac{ON}{OFF}}$ between ON and OFF band frames is known, the H$\alpha $+[NII] equivalent width can be estimated also in non photometric conditions. The zero point of each galaxy is determined assuming an extinction law of slope 0.1 for the OHP and 0.12 for the Calar Alto observations respectively.

At the redshift of Virgo the Calar Alto OFF band filter ($\lambda$ 6744  Å) is partly contaminated by the emission of the [SII] dublet at $\lambda$ 6717  Å and 6731  Å. We corrected for this effect using Eqs. (3), (4) and (5) given in Paper I.

Errors on the H$\alpha $+[NII] flux and EW are estimated from Eqs. (6) and (7) of Paper I.

5 Results

The results of the present observations are listed in Table 5, arranged as follow:

The red continuum images of the detected galaxies with structure in their H$\alpha $emission are shown as contours plots superposed to the H$\alpha $+[NII] net image (grey levels) in Fig. 1.

The H$\alpha $+[NII] morphology is generally very different from the red continuum one. In only a few objects the spiral morphology can be seen in the H$\alpha $+[NII] image (see Col. 13 of Table 5), as in VCC 307, while in other galaxies the dominant star forming regions are located in the nucleus (see for example VCC 801) or in giant HII regions distributed non-uniformly throughout the disc of the galaxy, as in VCC 664. In some other objects the emission is diffuse (VCC 497).


   
Table 5: The results of the observations.

Virgo		                                  
  This work Literature
VCC ON OFF Tel Year T R(Ha) $n_{\rm\frac{ON}{OFF}}$ K H $\alpha+[{\rm NII}] EW$ $F({\rm H}\alpha+[{\rm NII}])$ Phot Morph Notes H $\alpha+[{\rm NII}] EW$ $F({\rm H}\alpha+[{\rm NII}])$ Ref. Notes
(1) (2) (3) (4) (5) (6) (7) (8) (9) (10) (11) (12) (13) (14) (15) (16) (17) (18)
                                   
67 6561 6450 OHP 2000 60 0.78 0.98 1.00 27 $\pm$ 3 -12.69 $\pm$ 0.05 P H   - - -  
92 6561 6450 OHP 1998 30 0.79 1.00 1.00 9 $\pm$ 1 -11.53 $\pm$ 0.06 P DS   - -11.50 Ko *
145 6561 6450 OHP 2000 45 0.68 1.02 1.00 7 $\pm$ 1 - C DS   - -12.04 Y  
165 6561 6450 OHP 2000 30 0.77 1.02 1.00 0 $\pm$ 2 - C     - - -  
167 6561 6450 OHP 2000 30 0.78 1.02 1.00 3 $\pm$ 1 - C DS   - -11.52 Y  
222 6612 6561 OHP 2000 45 0.67 1.11 1.00 2 $\pm$ 1 -12.75 $\pm$ 0.07 P N   - - -  
234 6569 6744 CA 1999 30 0.80 1.10 0.64 13 $\pm$ 12 -12.31 $\pm$ 0.23 P ND   - - -  
267 6569 6744 CA 1999 30 0.85 1.11 0.66 11 $\pm$ 18 -12.83 $\pm$ 0.45 P S   16 $\pm$ 3   Hi  
307 6612 6561 OHP 1998 30 0.68 1.16 1.00 29 $\pm$ 1 -10.96 $\pm$ 0.05 P S   32 $\pm$ 1 -10.91 KK *
315 6612 6450 OHP 2000 45 0.65 1.08 1.00 0 $\pm$ 1 - P     - - -  
341 6612 6450 OHP 2000 45 0.68 1.08 1.00 2 $\pm$ 1 -12.86 $\pm$ 0.16 P ND   - - -  
371 6569 6744 CA 1999 30 0.75 1.16 0.63 2 $\pm$ 2 - P     - - -  
375 6569 6744 CA 1999 30 0.70 1.18 0.61 -1 $\pm$ 4 - P     - - -  
382 6569 6744 CA 1999 30 0.75 1.21 0.63 30 $\pm$ 4 -11.78 $\pm$ 0.05 P HN   - - -  
386 6569 6744 CA 1999 30 0.70 1.19 0.61 -1 $\pm$ 11 - P     - - -  
408 6569 6744 CA 1999 30 0.67 1.15 0.67 4 $\pm$ 3 -12.41 $\pm$ 0.20 P D   - - -  
483 6569 6744 CA 1999 30 0.82 1.16 0.64 31 $\pm$ 7 -11.61 $\pm$ 0.07 P S   17 $\pm$ 2 -11.81 R *
497 6569 6744 CA 1999 30 0.82 1.16 0.64 15 $\pm$ 8 -11.86 $\pm$ 0.14 P D   - - -  
524 6612 6450 OHP 2000 30 0.42 1.14 1.00 5 $\pm$ 1 -12.52 $\pm$ 0.09 P D   - - -  
559 6561 6450 OHP 2000 45 0.78 1.03 1.00 2 $\pm$ 1 -12.86 $\pm$ 0.15 P N   - - -  
570 6569 6744 CA 1999 30 0.82 1.43 0.64 -1 $\pm$ 11 - C     - - -  
596 6612 6561 OHP 1998 30 0.64 1.18 1.00 18 $\pm$ 1 -11.01 $\pm$ 0.05 P S   18 $\pm$ 1 -11.05 KK *
608 6612 6561 OHP 1998 30 0.66 1.18 1.00 -1 $\pm$ 1 - P     - - -  
630 6612 6561 OHP 2000 45 0.64 1.10 1.00 7 $\pm$ 2 -12.62 $\pm$ 0.12 P SD   - - -  
634 6561 6612 OHP 1998 30 0.76 0.85 1.00 2 $\pm$ 2 - P     - - -  
656 6612 6450 OHP 2000 45 0.43 1.13 1.00 9 $\pm$ 1 - P NDS   6 - GS  
657 6612 6450 OHP 2000 45 0.27 1.13 1.00 -1 $\pm$ 1 - P     - - -  
664 6569 6744 CA 1999 30 0.82 1.17 0.64 101 $\pm$ 52 -12.12 $\pm$ 0.11 P H   164 - GS  
672 6612 6450 OHP 2000 45 0.41 1.10 1.00 -1 $\pm$ 1 - P     - - -  
697 6612 6450 OHP 2000 45 0.50 1.10 1.00 15 $\pm$ 8 -12.81 $\pm$ 0.21 P S   - - -  
792 6612 6450 OHP 2000 30 0.43 1.11 1.00 10 $\pm$ 2 -12.02 $\pm$ 0.13 P DS   - -12.64 Ko *
794 6612 6450 OHP 2000 45 0.40 1.11 1.00 -1 $\pm$ 2 - P     - - -  
797 6612 6450 OHP 2000 30 0.28 1.06 1.00 -1 $\pm$ 13: - C   * - - -  
798 6612 6450 OHP 2000 30 0.28 1.06 1.00 7 $\pm$ 1: -11.87 $\pm$ 0.12: N ND * - - -  
801 6612 6450 OHP 2000 45 0.66 1.11 1.00 69 $\pm$ 2 -11.57 $\pm$ 0.12 P N   - -11.56 Ko *
836 6612 6561 OHP 2000 60 0.67 1.17 1.00 15 $\pm$ 1 -11.67 $\pm$ 0.13 P NS   64 - GS  
857 6612 6450 OHP 2000 30 0.40 1.06 1.00 12 $\pm$ 4 - C S   - -12.25 Ko *
865 6561 6450 OHP 2000 40 0.78 1.04 1.00 34 $\pm$ 2 -12.12 $\pm$ 0.05 P SH * - - -  
873 6569 6744 CA 1999 20 0.85 1.19 0.65 10 $\pm$ 2 -12.18 $\pm$ 0.07 P S   16 $\pm$ 1 -11.97 B *
874 6569 6744 CA 1999 30 0.82 1.18 0.65 3 $\pm$ 3 -12.93 $\pm$ 0.26 P S   - -12.47 Ko *
905 6612 6450 OHP 2000 45 0.52 1.29 1.00 39 $\pm$ 16: -12.64 $\pm$ 0.14: N S * - - -  
912 6569 6744 CA 1999 30 0.84 1.21 0.65 8 $\pm$ 10: -12.56 $\pm$ 0.31: Y NS * - -12.31 Ko *
916 6569 6744 CA 1999 30 0.82 1.20 0.64 -1 $\pm$ 7 - P     - - -  
939 6612 6450 OHP 2000 45 0.51 1.29 1.00 40 $\pm$ 13: - C S   24 $\pm$ 5 -12.37 R *
958 6561 6450 OHP 2000 45 0.78 0.94 1.00 7 $\pm$ 1 - C NS   - -12.70 Ko *
979 6561 6450 OHP 2000 45 0.76 1.00 1.00 9 $\pm$ 1 - C N   - -12.22 Ko *
984 6569 6744 CA 1999 30 0.82 1.17 0.65 1 $\pm$ 4 - P   * - - -  
1003 6612 6450 OHP 2000 45 0.48 1.06 1.00 5 $\pm$ 3 -11.72 $\pm$ 0.13 P ND * - -13.15 Ko  
1145 6569 6744 CA 1999 20 0.82 1.16 0.64 11 $\pm$ 3 -11.73 $\pm$ 0.09 P H   - -11.91 Ko *
1182 6744 6569 CA 1999 30 0.82 0.86 1.00 42 $\pm$ 3 -13.08 $\pm$ 0.05 P HS   - - -  
1190 6561 6450 OHP 2000 45 0.76 0.96 1.00 3 $\pm$ 1 -12.49 $\pm$ 0.08 P ND   - - -  
1192 6569 6744 CA 1999 30 0.82 1.17 0.64 -1 $\pm$ 3 - P     - - -  
1203 6569 6744 CA 1999 30 0.82 1.17 0.64 3 $\pm$ 8 - P     - - -  
1205 6569 6744 CA 1999 30 0.75 1.17 0.63 11 $\pm$ 4 -12.50 $\pm$ 0.11 P S   38 - GS  
1375 6612 6561 OHP 2000 45 0.65 1.17 1.00 28 $\pm$ 3 - C S   33 $\pm$ 5 -11.69 KK  


 
Table 5: continued.
  This work Literature
VCC ON OFF Tel Year T R(Ha) $n_{\rm\frac{ON}{OFF}}$ K H $\alpha+[{\rm NII}] EW$ $F({\rm H}\alpha+[{\rm NII}])$ Phot Morph Notes H $\alpha+[{\rm NII}] EW$ $F({\rm H}\alpha+[{\rm NII}])$ Ref. Notes
(1) (2) (3) (4) (5) (6) (7) (8) (9) (10) (11) (12) (13) (14) (15) (16) (17) (18)

1401		 6612 6561 OHP 1998 20 0.68 1.17 1.00 6 $\pm$ 1 -11.48 $\pm$ 0.07 P S   6 $\pm$ 2 -11.50 KK *
1412 6569 6744 CA 1999 30 0.82 1.21 0.64 -1 $\pm$ 2 - P     - - -  
1450 6569 6744 CA 1999 30 0.84 1.13 0.65 69 $\pm$ 22 -11.89 $\pm$ 0.08 P H   72 - GS  
1453 6569 6744 CA 1999 30 0.82 1.13 0.65 1 $\pm$ 15 - P     - - -  
1540 6612 6561 OHP 2000 30 0.65 1.10 1.00 20 $\pm$ 1 - C S   - -11.35 Ko *
1552 6569 6744 CA 1999 30 0.85 1.20 0.65 2 $\pm$ 10 - P     3 - GS  
1555 6612 6561 OHP 1998 30 0.68 1.14 1.00 17 $\pm$ 4 -11.26 $\pm$ 0.11 P S   14 $\pm$ 3 -11.43 KK *
1562 6612 6561 OHP 1998 20 0.66 1.19 1.00 20 $\pm$ 2 -11.37 $\pm$ 0.06 P SN   18 $\pm$ 4 -11.48 KK *
1572 6612 6561 OHP 2000 30 0.66 1.10 1.00 -1 $\pm$ 2 - C     - - -  
1575 6561 6450 OHP 1998 30 0.73 1.02 1.00 13 $\pm$ 1 -12.73 $\pm$ 0.06 P H   54 - GS  
1588 6569 6744 CA 1999 30 0.82 1.16 0.64 3 $\pm$ 3 -12.56 $\pm$ 0.32 P S   - - -  
1673 6612 6561 OHP 1998 30 0.68 1.13 1.00 15 $\pm$ 1 -12.00 $\pm$ 0.05 P S   11 $\pm$ 3 -12.10 K *
1676 6612 6561 OHP 1998 30 0.68 1.13 1.00 19 $\pm$ 1 -11.74 $\pm$ 0.05 P S   20 $\pm$ 5 -11.70 K *
1690 6561 6612 OHP 1998 30 0.78 0.87 1.00 2 $\pm$ 1 -12.02 $\pm$ 0.25 P S   6 $\pm$ 2 -11.62 KK *
1730 6569 6744 CA 1999 30 0.82 1.20 0.64 4 $\pm$ 4 -12.62 $\pm$ 0.25 P SD   - -12.57 Ko *
1760 6612 6450 OHP 2000 40 0.38 1.11 1.00 5 $\pm$ 2 -12.46 $\pm$ 0.16 P NDS   - - -  
1859 6569 6744 CA 1999 30 0.82 1.24 0.64 -1 $\pm$ 12 - P     - -12.67 Ko  
1868 6569 6744 CA 1999 30 0.80 1.24 0.65 3 $\pm$ 9 - P     - - -  
1931 6612 6450 OHP 2000 30 0.47 1.10 1.00 36 $\pm$ 20 -13.33 $\pm$ 0.32 P N   - - -  
1941 6612 6450 OHP 2000 30 0.50 1.10 1.00 -1 $\pm$ 4 - P     - - -  
1943 6612 6450 OHP 2000 30 0.44 1.10 1.00 24 $\pm$ 2 -11.67 $\pm$ 0.07 P S   19 -11.82 Kpc *
14063 6612 6450 OHP 2000 30 0.48 1.07 1.00 32 $\pm$ 2 -11.24 $\pm$ 0.10 P S   - - -  
71060 6612 6561 OHP 2000 30 0.66 1.12 1.00 44 $\pm$ 1 -11.97 $\pm$ 0.04 P NHS   55 - GS  

Coma/A1367 supercluster
  This work Literature
CGCG ON OFF Tel Year T R(Ha) $n_{\rm\frac{ON}{OFF}}$ K H $\alpha+[{\rm NII}] EW$ $F({\rm H}\alpha+[{\rm NII}])$ Phot Morph Notes H $\alpha+[{\rm NII}] EW$ $F({\rm H}\alpha+[{\rm NII}])$ Ref. Notes

160065		 6744 6569 CA 1999 10 0.83 0.87 1.00 -1 $\pm$ 2 - P   * - - -  
160069 6744 6569 CA 1999 20 0.82 0.87 1.00 -1 $\pm$ 2 - P   * - - -  
160213 6744 6569 CA 1999 20 0.68 0.87 1.00 57 $\pm$ 3 -12.92 $\pm$ 0.05 P H * - - -  
160214 6744 6569 CA 1999 20 0.84 0.87 1.00 -1 $\pm$ 1 - P   * - - -  
160215 6744 6569 CA 1999 20 0.84 0.87 1.00 -1 $\pm$ 2 - P   * - - -  
160216 6744 6569 CA 1999 10 0.84 0.87 1.00 -1 $\pm$ 2 - P   * - - -  
160221 6744 6569 CA 1999 10 0.82 0.87 1.00 -1 $\pm$ 3 - P   * - - -  
160222 6744 6569 CA 1999 10 0.05 0.87 1.00 -1 $\pm$ 22 - P   * - - -  
161043 6744 6569 CA 1999 30 0.77 0.84 1.00 -1 $\pm$ 1 - P     - - -  
161069 6744 6569 CA 1999 30 0.82 0.84 1.00 24 $\pm$ 1 -12.66 $\pm$ 0.05 P H   - - -  

A2197/A2199
  This work Literature
CGCG ON OFF Tel Year T R(Ha) $n_{\rm\frac{ON}{OFF}}$ K H $\alpha+[{\rm NII}] EW$ $F({\rm H}\alpha+[{\rm NII}])$ Phot Morph Notes H $\alpha+[{\rm NII}] EW$ $F({\rm H}\alpha+[{\rm NII}])$ Ref. Notes

224008		 6744 6569 CA 1999 30 0.75 0.81 1.00 14 $\pm$ 2 -12.95 $\pm$ 0.07 P D   - - -  
224009 6744 6569 CA 1999 30 0.70 0.81 1.00 14 $\pm$ 2 -12.69 $\pm$ 0.07 P S   - - -  
224037N 6744 6569 CA 1999 30 0.70 0.84 1.00 6 $\pm$ 2 -13.40 $\pm$ 0.12 P N   - - -  
224037S 6744 6569 CA 1999 30 0.77 0.84 1.00 5 $\pm$ 1 -13.54 $\pm$ 0.08 P N   - - -  
224038 6744 6569 CA 1999 30 0.82 0.84 1.00 115 $\pm$ 2 -12.14 $\pm$ 0.04 P H   123 $\pm$ 3 -12.24 G  
224046 6744 6569 CA 1999 30 0.77 0.84 1.00 17 $\pm$ 2 -12.88 $\pm$ 0.07 P NDS   - - -  


 
Table 5: continued.

Nearby galaxies
  This work Literature
Name ON OFF Tel Year T R(Ha) $n_{\rm\frac{ON}{OFF}}$ K H $\alpha+[{\rm NII}] EW$ $F({\rm H}\alpha+[{\rm NII}])$ Phot Morph Notes H $\alpha+[{\rm NII}] EW$ $F({\rm H}\alpha+[{\rm NII}])$ Ref. Notes
                                   
M51 6561 6450 OHP 2000 15 0.77 1.02 1.00 18.6 $\pm$ 1.6 -10.55 $\pm$ 0.05 P S * 24 $\pm$ 2 -10.52: KK *
M81 6561 6450 OHP 2000 10 0.78 0.96 1.00 9.7 $\pm$ 2.9 -10.30 $\pm$ 0.13 P SN M - -10.34 D *
M82 6561 6450 OHP 1998 15 0.77 0.93 1.00 42.3 $\pm$ 0.5 -10.22 $\pm$ 0.04 P N   - -10.04 Y *
M106 6561 6450 OHP 2000 15 0.76 0.95 1.00 12.3 $\pm$ 2.0 - C S M 11 -10.66 Kpc *
N925 6561 6450 OHP 2000 30 0.74 0.98 1.00 23.3 $\pm$ 4.1 - C S   - -11.10 Y  
N1637 6561 6450 OHP 2000 60 0.68 1.09 1.00 9.9 $\pm$ 1.7 - C S   16 $\pm$ 2 -11.68 KK  
N2403 6561 6450 OHP 2000 10 0.77 0.92 1.00 64.4 $\pm$ 11.8 - C S M 26 -10.34 Kpc  
N2541 6561 6450 OHP 2000 40 0.75 0.92 1.00 39.6 $\pm$ 8.0 - C S   46 $\pm$ 7 -11.64 R  
N2805 6612 6561 OHP 2000 60 0.65 1.07 1.00 52.3 $\pm$ 11.2 - C S   - - -  
N2903 6561 6450 OHP 2000 30 0.76 1.00 1.00 15.0 $\pm$ 1.3 -11.07 $\pm$ 0.08 P S * - -10.67 Y *
N5195 6561 6450 OHP 2000 15 0.77 1.10 1.00 3.5 $\pm$ 2.3 -12.18 $\pm$ 0.99 C N * 20: - K *

Notes:

M in notes indicates a mosaic of several frames; if not specified, the given data are alternative values in the literature with reference.

VCC 92: $F({\rm H}\alpha+[{\rm NII}])=-11.43$ $\rm erg~ cm^{-2} ~s^{-1}$ (Y); H $\alpha+[{\rm NII}] EW=12$ Å  (GS). VCC 307: H $\alpha+[{\rm NII}] EW=31\pm1$ Å  (H), H $\alpha+[{\rm NII}] EW=42\pm1$ Å  (GS), $F({\rm H}\alpha+[{\rm NII}])=-10.89$ $\rm erg~ cm^{-2} ~s^{-1}$ (Y), $F({\rm H}\alpha+[{\rm NII}])=-10.95$ $\rm erg~ cm^{-2} ~s^{-1}$ (Ko).

VCC 483: H $\alpha+[{\rm NII}] EW=11\pm2$ Å, H $\alpha+[{\rm NII}] EW=18\pm1$ Å  (GS), $F({\rm H}\alpha+[{\rm NII}])=-12.02$ $\rm erg~ cm^{-2} ~s^{-1}$ (KK), $F({\rm H}\alpha+[{\rm NII}])=-11.95$ $\rm erg~ cm^{-2} ~s^{-1}$ (Ko), $F({\rm H}\alpha+[{\rm NII}])=-11.74$ $\rm erg~ cm^{-2} ~s^{-1}$ (Y).

VCC 596: H $\alpha+[{\rm NII}] EW=21\pm1$ Å  (GS), $F({\rm H}\alpha+[{\rm NII}])=-11.13$ $\rm erg~ cm^{-2} ~s^{-1}$ (Ko), $F({\rm H}\alpha+[{\rm NII}])=-11.09$ $\rm erg~ cm^{-2} ~s^{-1}$ (Y).

VCC 792: $F({\rm H}\alpha+[{\rm NII}])=-12.28$ $\rm erg~ cm^{-2} ~s^{-1}$ (Y).

VCC 797: at the border of the filter.

VCC 798: at the border of the filter; observed in non photometric conditions; flux calibrated on VCC 857 from Y.

VCC 801: H $\alpha+[{\rm NII}] EW=52\pm3$ Å (GS).

VCC 857: H $\alpha+[{\rm NII}] EW=-1\pm3$ Å (KK), H $\alpha+[{\rm NII}] EW=1\pm3$ Å (H), $F({\rm H}\alpha+[{\rm NII}])=-11.97$ $\rm erg~ cm^{-2} ~s^{-1}$ (Y).

VCC 865: 2 coherent measurements.

VCC 873: H $\alpha+[{\rm NII}] EW=11$ Å(Kpc), H $\alpha+[{\rm NII}] EW=14$ Å(GS), $F({\rm H}\alpha+[{\rm NII}])=-12.38$ $\rm erg~ cm^{-2} ~s^{-1}$ (Kpc).

VCC 874: H $\alpha+[{\rm NII}] EW=10\pm3$ Å (GS).

VCC 905: observed in non photometric conditions; flux calibrated on VCC 939 from R.

VCC 912: vignetted; poor quality; H $\alpha+[{\rm NII}] EW=12\pm7$ Å (H), H $\alpha+[{\rm NII}] EW=24\pm7$ Å (GS), and $F({\rm H}\alpha+[{\rm NII}])=-12.16$ $\rm erg~ cm^{-2} ~s^{-1}$ (Y).

VCC 939: $F({\rm H}\alpha+[{\rm NII}])=-12.28$ $\rm erg~ cm^{-2} ~s^{-1}$ (Ko)

VCC 958: $F({\rm H}\alpha+[{\rm NII}])=-11.81$ $\rm erg~ cm^{-2} ~s^{-1}$ (Y)

VCC 979: $F({\rm H}\alpha+[{\rm NII}])=-12.10$ $\rm erg~ cm^{-2} ~s^{-1}$ (Y)

VCC 984: vignetted.

VCC 1003: H $\alpha+[{\rm NII}] EW=1\pm3$ Å (GS).

VCC 1145: H $\alpha+[{\rm NII}] EW=8\pm3$ Å (GS).

VCC 1401: $F({\rm H}\alpha+[{\rm NII}])=-11.21$ $\rm erg~ cm^{-2} ~s^{-1}$ (Ko), $F({\rm H}\alpha+[{\rm NII}])=-11.14$ $\rm erg~ cm^{-2} ~s^{-1}$ (Y).

VCC 1540: $F({\rm H}\alpha+[{\rm NII}])=-11.28$ $\rm erg~ cm^{-2} ~s^{-1}$ (Y).

VCC 1555: H $\alpha+[{\rm NII}] EW=3\pm3$ Å (GS), $F({\rm H}\alpha+[{\rm NII}])=-11.21$ $\rm erg~ cm^{-2} ~s^{-1}$ (Ko), $F({\rm H}\alpha+[{\rm NII}])=-11.26$ $\rm erg~ cm^{-2} ~s^{-1}$ (Y).

VCC 1562: $F({\rm H}\alpha+[{\rm NII}])=-11.42$ $\rm erg~ cm^{-2} ~s^{-1}$ (Ko), $F({\rm H}\alpha+[{\rm NII}])=-11.34$ $\rm erg~ cm^{-2} ~s^{-1}$ (Y).

VCC 1673: $F({\rm H}\alpha+[{\rm NII}])$ in reference does not include the whole galaxy. Other references give: H $\alpha+[{\rm NII}] EW=20\pm3$ Å (GS), $F({\rm H}\alpha+[{\rm NII}])=-11.91$ $\rm erg~ cm^{-2} ~s^{-1}$ (Ko).

VCC 1676: $F({\rm H}\alpha+[{\rm NII}])$ in reference does not include the whole galaxy. Other references give: H $\alpha+[{\rm NII}] EW=27\pm3$ Å (GS), $F({\rm H}\alpha+[{\rm NII}])=-11.59$ $\rm erg~ cm^{-2} ~s^{-1}$ (Ko).

VCC 1690: H $\alpha+[{\rm NII}] EW=5\pm3$ Å (GS), $F({\rm H}\alpha+[{\rm NII}])=-11.83$ $\rm erg~ cm^{-2} ~s^{-1}$ (Ko), $F({\rm H}\alpha+[{\rm NII}])=-11.24$ $\rm erg~ cm^{-2} ~s^{-1}$ (Y).

VCC 1730: H $\alpha+[{\rm NII}] EW=9\pm3$ Å (GS).

VCC 1943: $F({\rm H}\alpha+[{\rm NII}])=-11.94$ $\rm erg~ cm^{-2} ~s^{-1}$ (Ko), $F({\rm H}\alpha+[{\rm NII}])=-11.79$ $\rm erg~ cm^{-2} ~s^{-1}$ (Y).

160065, 160069, 160213, 160214, 160215, 160216, 160221, 160222: affected by stray light from bright star.

M51: another image taken in non photometric conditions gives H $\alpha+[{\rm NII}] EW=18\pm5.4$ Å; other references give: H $\alpha+[{\rm NII}] EW=28\pm4$ Å, $F({\rm H}\alpha+[{\rm NII}])=-10.5$ $\rm erg~ cm^{-2} ~s^{-1}$ (not including the entire galaxy) (K); $F({\rm H}\alpha+[{\rm NII}])=-10.33$ $\rm erg~ cm^{-2} ~s^{-1}$ (Y).

M81: $F({\rm H}\alpha+[{\rm NII}])=-10.32$ $\rm erg~ cm^{-2} ~s^{-1}$ (Gr); H $\alpha EW=6$ Å, $F(H\alpha)=-10.49$ $\rm erg~ cm^{-2} ~s^{-1}$ (Kpc; no [NII] included).

M82: H $\alpha+[{\rm NII}] EW=45$ Å (K92), H $\alpha+[{\rm NII}] EW=110$ Å (GS).

M106: [NII] not included in the reference values.

N2903: another image taken in non photometric conditions gives H $\alpha+[{\rm NII}] EW=12\pm3$ Å; alternative value in the literature: H $\alpha+[{\rm NII}] EW=28$ Å  in K92.

N5195: another image taken in non photometric conditions gives H $\alpha+[{\rm NII}] EW=2\pm1$ Å; alternative value in the literature: H $\alpha+[{\rm NII}] EW=3.5$ Å  in K92.

References: KK: Kennicutt & Kent (1983); K: Kennicutt et al. (1987); Y: Young et al. (1996); Hi: Hippelein et al., in preparation; R: Romanishin (1987); B: Boselli et al. (2002), Paper III; G: Gavazzi et al. (1998); D: Devereux et al. (1995); Gr: Greenawalt et al. (1998); K92: Kennicutt (1992) (spectroscopic survey drifting the telescope over the entire disc of the galaxy); Kpc: Kennicutt, private communication; Ko: Koopmann et al. (2001); GS: Gavazzi et al., in preparation (spectroscopic survey drifting the telescope over the entire disc of the galaxy).


5.1 Recalibrations

16 galaxies previously observed with the Calar Alto 3.5 m telescope (Hippelein et al., in preparation) in non photometric conditions were reobserved at the OHP with 5 min exposures in the ON band filter in order to achieve a flux calibration. If $n_{\rm\frac{ON_{CA}}{ON_{OHP}}}$ is the normalization constant between the ON band Calar Alto and OHP images (normalized to the same integration time), the ON band zero point for Calar Alto observations $Zp_{\rm ON_{CA}}$ is given by the relation:

\begin{displaymath}{Zp_{\rm ON_{CA}} = \frac {Zp_{\rm ON_{OHP}}}{n_{\frac{\rm ON_{CA}}{\rm ON_{OHP}}}}} \end{displaymath} (1)

where $Zp_{\rm ON_{OHP}}$ is the OHP zero point determined for the galaxy at a given airmass. $Zp_{\rm ON_{CA}}$ does not need to be corrected for airmass.

The resulting fluxes are given in Table 6.


 

 
Table 6: Calibration of the Calar Alto 1993 observations.

VCC 		Tel H$\alpha $+[NII]EW F(H$\alpha $+[NII]) F(H$\alpha $+[NII])$_{\rm L}$ Ref.

87 		OHP $20 \pm 1$ $-12.83 \pm 0.25$: -12.94 GH
152 OHP $9 \pm 1$ $-12.63 \pm 0.26$ -  
159 OHP $19 \pm 1$ $-13.21 \pm 0.32$ -  
446 OHP $18 \pm 1$ $-13.47 \pm 0.15$ -  
641 OHP $20 \pm 1$ $-13.55 \pm 0.08$: -  
995 OHP $32 \pm 1$ $-12.98 \pm 0.13$ -  
1002 OHP $9 \pm 1$ $-12.10 \pm 1.00$: -  
1189 OHP $21 \pm 1$ $-12.66 \pm 0.19$ -  
1419 OHP $ 5 \pm 2$ $-13.06 \pm 0.79$ -  
1486 OHP $12 \pm 1$ $-13.17 \pm 1.00$: -  
1507 OHP $11 \pm 1$ $-13.51 \pm 0.24$ -  
1569 OHP $14 \pm 2$ $-13.45 \pm 0.31$ -  
1678 OHP $55 \pm 8$ $-12.56 \pm 1.00$: -  
1929 OHP $13 \pm 2$ $-12.75 \pm 0.45$ -  
1932 OHP $16 \pm 1$ $-12.32 \pm 0.49$ -  
2037 OHP $16 \pm 1$ $-13.82 \pm 0.62$ -13.53 B
2066 OHP $ 6 \pm 1$ $-12.47 \pm 1.00$: -  

Notes: 2037: also observed by GH ( $F(\rm H\alpha+[NII])=-13.47$ $\rm erg~ cm^{-2} ~s^{-1}$).
References: B: Boselli et al. (2002), Paper III; GH: Gallagher & Hunter (1989).


  \begin{figure} \par\includegraphics[width=7cm,clip]{MS2159f2.eps} \end{figure} Figure 2: Comparison with data in the literature: open dots are for KK, filled dots for Y, filled squares for H, x for R, + for Ko, $\curlywedge $ for K, open triangles for B, open squares for D, stars for Gr, filled triangles for G, filled pentagons for Kpc, open pentagons for GH, open exagons for K92 and filled exagons for GS.
Open with DEXTER

5.2 Comparison with the literature

Fluxes and equivalent widths given in this paper are in general consistent with available measurements, as shown in Fig. 2. The average value of the difference between our measurements and those available in the literature is: ${\rm H}\alpha+[{\rm NII}] EW_{\rm TW}-{\rm H}\alpha+[{\rm NII}] EW_{\rm L}= 0 \pm 10$ Å and $-\log F({\rm H}\alpha+[{\rm NII}])_{\rm TW}$ + $\log F({\rm H}\alpha+[{\rm NII}])_{\rm L} = -0.04 \pm 0.32$  $\rm erg~ cm^{-2} ~s^{-1}$ [*] (in the comparison of the H $\alpha+[{\rm NII}] EW$ we excluded those long slit spectra of Gavazzi et al. not including the entire galaxy). The outlying galaxy in the flux-flux relation is VCC 1003. Spectroscopic observations (GS) give an H $\alpha+[{\rm NII}] EW$ smaller than that obtained in this work; the flux given in Table 5 could thus be overestimated. The outlying galaxies in the equivalent width relation, whose $\alpha+[{\rm NII}] EW$ are significantly higher in this work with respect to the literature, are VCC 798 (open dot), VCC 857 (filled square) and VCC 1003 (filled exagon). As explained in the notes of Table 5, the value given for VCC 798 is highly uncertain. The H$\alpha $ image of VCC 857 shows emission in small, low surface brightness HII regions. We thus trust our value.

6 Summary and conclusion

We present H$\alpha $+[NII] imaging data (fluxes and equivalent widths) of 122 galaxies obtained at the 1.20 m telescopes of the Observatoire de Haute Provence (OHP) and of Calar Alto. The present observations of late-type galaxies in the Virgo cluster are aimed at completing a large project of multifrequency observations of galaxies spanning a large range in morphological type and luminosity and belonging to different environments (cluster-isolated) aimed at constructing a data-set suitable for statistical studies.

Acknowledgements

We wish to thank the night operators for their assistance during the observations and the OHP and Calar Alto TACs for the generous time allocation. We thank R. Kennicutt for providing us with unpublished data and J. Iglesias-Paramo for helping during the preparation of the figures. This project is partly financed by the French GdR Galaxies and PNG.

References

 

Online Material


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Copyright ESO 2002