Appendix: UBV CCD photometry of Virgo galaxies

The present work is partly based on new CCD optical photometry of 36 galaxies obtained at the 1.20 m Newton telescope at the Observatoire de Haute Provance (OHP, France), at the 0.9 m telescope at Kitt Peak and at the 2.5 m INT telescope at La Palma. The OHP and the INT observations were taken during the H$\alpha$ surveys presented in Boselli & Gavazzi (2002) and Boselli et al. (2002a) respectively. Details on the observations and data reduction procedures are found in these papers. Kitt Peak targets were observed as fillers during an H$\alpha$ survey of isolated galaxies.

The f/6 1.2 m OHP telescope was equipped with a thinned TK $1024\times 1024$ pixels CCD detector, with a pixel size of 0.69 arcsec and a field of view of $11.8\times11.8$ arcmin. At the adopted gain, the electron/adu conversion is 3.5 e^-/adu, with a readout noise of 8.5 e^-. Thirty galaxies of the present sample were observed during 26 nights in two runs, in 1998 and 2000. Fourteen galaxies were imaged in the V, 30 in the B and 1 in the U band. The observations were done in poor seeing conditions, ranging from 2 to 4 arcsec. The typical integration time was 10 minuts in the V, 15 in the B and 30 in the U bands.

INT B band imaging of 2 galaxies were obtained in 1999 using the Wide Field Camera (WFC) attached at the prime focus of the f/3.292.5 m telescope. The WFC is composed by a science array of four thinned AR coated EEV $\rm 4K\times 2K$ CCDs, plus a fifth acting as autoguider. The pixel scale at the detectors is 0.33 arcsec pixel^-1, which gives a total field of view of about $34\times 34$  arcmin². The observations were done during photometric conditions, with an average seeing of 1.5-2 arcsec and an integration time of 10 min.

Kitt Peak B band imaging of 5 galaxies were obtained during 4 nights in 1995 using the 0.9 m telescope in the f/13 configuration, equipped with a T2KA $2048\times2048$ pixel CCD, with a pixel size of 0.384 arcsec pixel^-1 and a total field of view of $13.1\times13.1$ arcmin. At the adopted gain, the electron/adu conversion is 2 e^-/adu, with a lecture noise of 4 e^-. The observations were done during non photometric conditions, with an average seeing of 1-1.5 arcsec and an integration time of 15 min.

The observations were calibrated and transformed into the Johnson UBV system using standard stars in the catalogue of Landolt (1983). Observations of the standard stars were repeated every 2 hours. Repeated measurements gave <0.10 mag differences, which we assume as the typical uncertainty of the photometric result given in this work. Not all frames were obtained in photometric conditions. When the zero point was varing by more than 0.05 mag due to cirrus, we choose to observe only galaxies with available multiaperture photometry in order to perform the calibration a posteriori.

 

Table 10: Example of template dust extinction corrected B&C SEDs.

$\lambda$ ($\mu$m)	Log $(F(\nu)/F(K))$
	S0a	Sa	Sab-Sb	Sbc-Sc	Scd-Sd	Im	BCD	LH<8.3	8.3$\leq$LH<9	9$\leq$LH<9.8	9.8$\leq$LH<10.5	LH$\geq$10.5
0.1005	-3.26	-2.88	-2.04	-1.03	-0.81	-0.58	-0.40	-0.36	-0.51	-0.97	-1.26	-2.08
0.1015	-3.25	-2.88	-2.06	-1.05	-0.83	-0.62	-0.44	-0.40	-0.55	-1.01	-1.25	-2.09
0.1025	-3.36	-3.02	-2.25	-1.28	-1.02	-0.85	-0.67	-0.63	-0.77	-1.24	-1.42	-2.28
0.1035	-3.28	-2.91	-2.10	-1.09	-0.87	-0.65	-0.46	-0.43	-0.57	-1.04	-1.30	-2.13
0.1045	-3.19	-2.83	-1.98	-0.98	-0.75	-0.55	-0.37	-0.34	-0.48	-0.95	-1.16	-2.02
0.1055	-3.20	-2.83	-1.98	-0.97	-0.75	-0.54	-0.36	-0.32	-0.47	-0.93	-1.17	-2.01
...	...	...	...	...	...	...	...	...	...	...	...	...
1.0025	-0.02	0.14	0.08	0.08	0.15	0.05	0.22	0.32	0.18	0.12	0.11	0.06
1.0075	-0.02	0.13	0.07	0.08	0.15	0.04	0.21	0.32	0.17	0.12	0.10	0.05
1.0125	-0.02	0.14	0.08	0.08	0.15	0.05	0.22	0.33	0.18	0.12	0.11	0.06
1.0175	-0.02	0.14	0.08	0.08	0.15	0.05	0.22	0.32	0.18	0.12	0.10	0.06
1.0225	-0.01	0.14	0.08	0.08	0.15	0.05	0.22	0.32	0.18	0.12	0.11	0.06
...	...	...	...	...	...	...	...	...	...	...	...	...
9.7800	-1.09	-1.05	-1.10	-1.09	-1.02	-1.24	-1.06	-0.96	-1.10	-1.06	-1.07	-1.10
9.8200	-1.09	-1.05	-1.10	-1.09	-1.02	-1.24	-1.07	-0.96	-1.11	-1.06	-1.07	-1.11
9.8600	-1.09	-1.05	-1.11	-1.09	-1.02	-1.24	-1.07	-0.96	-1.11	-1.07	-1.07	-1.11
9.9000	-1.10	-1.05	-1.11	-1.09	-1.02	-1.24	-1.07	-0.96	-1.11	-1.07	-1.07	-1.11
9.9400	-1.10	-1.06	-1.11	-1.10	-1.03	-1.25	-1.08	-0.97	-1.12	-1.07	-1.08	-1.11
9.9800	-1.10	-1.06	-1.12	-1.11	-1.03	-1.25	-1.08	-0.97	-1.12	-1.08	-1.08	-1.12
10.0200	-1.11	-1.07	-1.12	-1.11	-1.04	-1.26	-1.09	-0.98	-1.12	-1.08	-1.09	-1.12

Notes: Table 10, 11 (template dust extinction uncorrected) and 12 (template FIR fit) are available only in electronic form at the CDS.

The data reduction of the CCD images follows a procedure identical to the one described in previous papers of the series (Gavazzi et al. 1995), based on the IRAF STSDAS data reduction packages. To remove the detector response each image is bias subtracted and devided by the mean of 5 flat field exposures obtained on the twilight sky. Direct inspection of the frames allows manual cosmic rays removal and subtraction of contaminating objects, such as nearby stars and galaxies. 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. The determination of object centroid is performed by fitting Gaussian two-dimensional profiles to the data, centered on the brightest excess in each object, generally corresponding to the nucleus. At the central coordinates determined, a growth curve is derived for each object by integrating the counts in concentric circular rings of increasing radii. The obtained growth curves, transformed from counts to magnitudes, are then compared with the multiaperture photometry available in the literature, in order to check our photometric calibration and to obtain a zero point for those objects observed in non-photometric conditions. At this stage stars projected within the target galaxies were not subtracted since, unless specified, reference aperture photometry usually includes them. Once the accurate zero point is obtained for each galaxy, a similar procedure is repeated after subtracting contaminating stars and galaxies. Following the procedure described in Gavazzi & Boselli (1996), a magnitude is obtained after integrating along circular, concentric annuli up to the isophotal 25 mag arcsec^-2B diameter. To improve the photometric accuracy, this procedure is applyed adding our measurements with aperture photometry available in the literature. UBV magnitudes of the target galaxies are given in Table 3. The estimated error on the magnitude is $\sim$10%.