1 Introduction

Among the definitely interacting galaxies in close pairs or groups, many of which were discovered by Vorontsov-Vel'yaminov and included in his Atlas and Catalog of interacting galaxies (Vorontsov-Vel'yaminov [1959], [1977]) there are objects having VV numbers, in which the interaction is not so evident. Such objects were usually classified by Vorontsov-Vel'yaminov as the "nests'' or often similarly looking systems called "chains'' or "pairs in contact''. He considered these objects as compact fragmenting systems, giving birth to young galaxies, but very soon observations showed that their nature may be different. Such systems can present both galaxies of strange and unusual shapes (either single objects or mergers), and really multiple systems, where it is hard to guess the number of components without detailed studies. In many cases only spectral measurements of their gas velocity distribution enable to prove or to disprove their solitude.

Earlier spectral observations confirmed that some VV systems actually present single dwarf galaxies with clumpy inner structure, resembling dwarf irregulars with multiple regions of active star formation (SF), or blue compact galaxies (BCGs) (Vorontsov-Vel'yaminov [1979a],b; Afanasiev et al. [1980]; Arkhipova et al. [1981], [1987a]-c). Only a few single nearby VV galaxies have been studied in detail (e.g. VV 556 $\equiv$ GR 8, VV 499 $\equiv$ DDO 053).

The important questions on the chemical abundances in the studied VV galaxies left outside the scope of these early observations. New opportunities appeared due to new CCD-detectors, which enable to realize high sensitivity and large dynamical range. It induced authors to return back to the study of "nest-like'' VV galaxies. Besides, many new observational data have appeared on many of these objects.

For the current study we selected more than twenty VV galaxies looking like multiple systems or singular irregular systems in the POSS/DSS images, for which such indicators of interaction as well defined tidal tails or bridges are absent. The main objectives of our investigation are:

• to clarify the distances, total luminosities and masses of those systems, systemic velocities of which are not known or badly known;

• to carry out high S/N ratio spectrophotometry in order to address problems of chemical abundances and evolutional status of these objects;

• to analyse the inner gas kinematics and structural properties of the objects.

Since many of VV galaxies in question are dwarfs with recent or current SF burst, it is also important to check possible companions which could exert strong enough tidal action.

 

 

Table 1: Journal of observations

Galaxy	Date	Instrument	Grating	Exposure	Wavelength	Dispersion	PA
Name			[grooves/mm]	time [s]	Range [Å]	[Å/pixel]	[Degree]
(1)	(2)	(3)	(4)	(5)	(6)	(7)
VV 432	12.02.1999	LSS+PMCCD	325	900	3700-8000	4.6	27
VV 432	23.04.1999	LSS+PMCCD	1302	2 $\times$ 1200	4000-5200	1.2	27
VV 432	23.04.1999	LSS+PMCCD	1302	2 $\times$ 1200	6000-7200	1.2	27
VV 543	11.02.1999	LSS+PMCCD	325	900	3700-8000	4.6	101
VV 747	12.02.1999	LSS+PMCCD	325	1200	3700-8000	4.6	56

 

 

Table 2: Main parameters of studied VV-galaxies

Parameter	VV 432	VV 543 W	VV 543 E	VV 747
$\alpha_{2000}$	12$^{\rm h}$17$^{\rm m}$34.7$^{\rm s}$	13$^{\rm h}$42$^{\rm m}$22.2$^{\rm s}$	13$^{\rm h}$42$^{\rm m}$23.5$^{\rm s}$	10$^{\rm h}$57$^{\rm m}$46.9$^{\rm s}$
$\delta_{2000}$	+12$^\circ$23$^{\prime}$46 $^{\prime\prime}$	+29$^\circ$49$^{\prime}$33 $^{\prime\prime}$	+29$^\circ$49$^{\prime}$30 $^{\prime\prime}$	+36$^\circ$15$^{\prime}$38 $^{\prime\prime}$
$B_{{\rm tot}}^{\rm L}$	14.73 $\pm$ 0.15	17.7 $\pm$ 0.3	15.20 $\pm$ 0.20	15.52 $\pm$ 0.71
$A_{\rm B}^{\rm N}$	0.03	0.00	0.00	0.04
$V_{{\rm HeI}}$ (km s-1)	$-160~\pm$ 6	14100 $\pm$ 20	12480 $\pm$ 90	629 $\pm$ 75
Dist $_{{\rm Vir}}$(Mpc)	20.7 $\pm$ 0.8	188.4 $\pm$ 0.3	166.8 $\pm$ 1.2	9.2 $\pm$ 0.1
MB1	-16.8	-18.6	-20.9	-14.4
D25 (arcsec)	111	$\approx$16	39	50
D25 (kpc)	11.1	$\approx$14.6	31.5	2.2
Axis ratio b/aL	0.31	0.50	1.00	0.85
12+log(O/H)	7.58 $\pm$ 0.06	8.5 $\pm$ 0.1	--	7.85 $\pm$ 0.05
H I flux2	9.04 $\pm$ 1.993	--	--	4.03 $\pm$ 0.39
W20 km s-1	1233	--	--	117 $\pm$ 11
M(H I) (10 $^{8}M_{\odot}$)	9.1 $\pm$ 2.0	--	--	0.81 $\pm$ 0.08
M(H I)/LB4	1.2	--	--	1.0
$B_{{\rm tot}}$ -- total blue magnitude; MB -- absolute blue magnitude.
D25 -- Diameter at surface brightness $\mu_{B}$ = 25 mag/ $\Box^{\prime\prime}.$
AB -- Galactic extinction; L Data from LEDA; N Data from NED.
1 With Galactic extinction correction; 2 Units of (Jy km s-1).
3 From Schneider et al. ([1991]); 4 In (M/LB)$_{\odot}$; 5 From H I-profile.

In this paper, the first in the series, we present the results of recent long-slit spectroscopy for three VV objects: VV 432, VV 543 and VV 747 and the observation in HI-line of VV 747.

In Sect. 2 we describe observations, data reduction, abundances determination and the measurements of velocity distribution of ionized gas along the slit.

Observations of VV 747 in the HI-line 21 cm and their results are presented in Sect. 3. In Sect. 4 we consider the individual properties of studied galaxies. Discussions and preliminary conclusions are presented in Sect. 5. We adopt throughout the paper $H_0 = 75\;{\rm km\,s}^{-1}$.