3 The sample

Figure 1: Sky distribution of the 312 spiral galaxies brighter than $m_p \leq 16.0$ in the VCC. The filled symbols represent 235 galaxies with available H$\alpha$ data, the empty ones to unobserved galaxies. Circles are drawn at 2, 4, 6 deg projected radial distance from M 87 (cross).

Figure 2: Sky distribution of the 256 spiral galaxies brighter than $m_p \leq 15.7$ in the CGCG in the Coma supercluster region (top). Wedge diagram (bottom). The filled symbols represent 158 galaxies with available H$\alpha$ data, the empty ones to unobserved galaxies.

Including the new observations presented in this paper, this work comprises H$\alpha$ and NIR (H band) imaging observations of 369 late-type galaxies belonging to the Virgo cluster and to the Coma supercluster region.

The Virgo cluster galaxies were selected from the Virgo Cluster Catalogue (VCC) of Binggeli et al. (1985), with $m_p \leq 16.0$, Hubble type later than S0a (as given in the VCC) and classified as cluster members, possible members or belonging to the W, W', M clouds or to the southern extension (Binggeli et al. 1985, 1993; see also Gavazzi et al. 1999a) matching V<3000 $\rm km ~s^{-1}$ (see Fig. 1).

The late-type (> S0a) galaxies in the Coma supercluster region ( $\rm 18^o \le \delta \le 32^o$; $\rm 11.5^h \le \alpha \le 13.5^h$) were selected from the CGCG catalogue ( $m_p \leq ~15.7$) (Zwicky et al. 1961-68) and include members to the Coma Supercluster according to Gavazzi et al. (1999b) (see Fig. 2). Table 1 gives the details of the sample completeness in the two studied regions. The Coma supercluster members are divided in cluster (A1367+A1656) members, members to groups and pairs (see Gavazzi et al. 1999b) and strictly isolated supercluster objects (with projected separations >300 kpc). The H$\alpha$ observations were taken either from the present series of papers (Papers I, II, III, IV, primarily devoted to the Virgo cluster), from Gavazzi et al. (1991, 1998) (containing mostly observations of the Coma supercluster region) or from Kennicutt & Kent (1983), Kennicutt et al. (1984), Romanishin (1990), Koopmann et al. (2001) (see detailed references in Table 4).

The NIR observations were taken from the series of papers "Near-infrared H surface photometry of galaxies'' (Gavazzi et al. 1996a,b, 2000a; Boselli et al. 1997; Boselli et al. 2000 and from Gavazzi et al. 2001). Total asymptotic H band magnitudes were obtained by Gavazzi et al. (2000b) and by Gavazzi et al. (2001).

As listed in Table 1 the combined NIR+ H$\alpha$ observations cover more than 60% of the targets in all regions (except Coma supercluster groups+pairs), thus our data can be considered as representative of the late-type galaxies in the studied regions.

 

 

Table 1: The sample completeness.

region	$m_p \leq 16.0$	with NIR	with NIR & H$_\alpha$	Compl.
Virgo	323	271	205	63%
Coma S. (Clusters)	72	72	54	75%
Coma S. (Grps+Prs)	67	67	27	40%
Coma S. (Isolated)	119	83	83	69%
Tot.	568	480	356	63%

The analyzed galaxies are listed in Table 4 as follows:

• Column 1: VCC designation, from Binggeli et al. (1985) for Virgo galaxies, or CGCG (Zwicky et al. 1961-68) for Coma supercluster galaxies.
• Column 2: 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 3: morphological type as given in the VCC or in Gavazzi & Boselli (1996).
• Column 4: projected angular separation from the nearest cluster center (degrees).
• Column 5: asymptotic H band magnitude, obtained as described in Gavazzi et al. (2000b).
• Column 6: distance (Mpc); we assume 17 Mpc for Virgo A, N, S, E, 23 Mpc for Virgo B and 32 Mpc for Virgo W, M as given in Gavazzi et al. (1999a), 96 Mpc for Coma, 91 Mpc for A1367. For galaxies not belonging to the clusters, the distance is determined from the redshift using H₀= 75 $\rm km~s^{-1}~Mpc^{-1}$.
• Column 7: gas deficiency parameter as defined in Sect. 4.2.
• Column 8: ${\rm H_\alpha+[NII]} EW({\rm\AA})$.
• Column 9: Log of the $\rm H_\alpha$ flux ( $\rm erg~cm^{-2}~s^{-1}$) deblended from the [NII] contribution and corrected for internal extinction as in Boselli et al. (2001).
• Column 10: reference to the $\rm H_\alpha$ data (as listed at the bottom of the table).