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Astron. Astrophys. 326, 915-918 (1997)

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2. Data and sample selection

In this study the data of CO linewidths are taken from Young et al. (1995), who observed the [FORMULA]CO ([FORMULA]) emission line of 300 field galaxies using the 14-m telescope of the Five College Radio Astronomy Observatory (FCRAO) (HPBW = 45"). Among them the CO emission was detected at multiple positions for 103 galaxies. We excluded the following galaxies from our analysis; (1) galaxies for which we could not obtain linewidths due to weak or strange position-velocity diagrams, (2) face-on galaxies ([FORMULA]) in order to minimize the effect of inner velocity dispersion. As the result of these selection we selected 60 galaxies. We classified these galaxies into 17 interacting galaxies and 43 isolated galaxies. Then we classified the interacting galaxies into three subclasses using the interaction class (hereafter IAC) defined by Dahari (1985). Although the Dahari's IAC is classified into 6 groups based on features of interaction, we classified them into three classes due to the small sample. Our classification based on Dahari's IAC is as follows;

  • (1) weakly interacting galaxies (hereafter WIG, Dahari's IAC = 2,3),
  • (2) strongly interacting galaxies (hereafter SIG, Dahari's IAC = 4,5),
  • (3) mergers (Dahari's IAC = 6).

According to Dahari's classification, IAC = 1 stands for isolated galaxies. The classification for individual galaxies based on Dahari's method is described in Table 3a and 3b, as well as Column 9 in Table 1. The galaxies which Dahari classified are marked with asterisks.


Table 1. Linewidths and distances for the interacting galaxies

The CO linewidths are obtained from position-velocity diagrams in the literature (Young et al. 1995). The HI linewidth and inclination of galaxies are taken from Huchtmeier & Richter (1989). Among HI data in the catalog, we selected the data observed at Arecibo 1000-ft, Effelsberg 100-m, NRAO Green Bank 300-ft, Jodrell Bank 250-ft and Parks 64-m telescopes in order to keep the quality of data set.

Linewidths are defined as the full width at 20% of maximum intensity of the global profile. In order to correct for an inclination effect, we adjust to an edge-on orientation by: Wi = W / sin i, where W is the observed linewidth, i is the inclination and Wi is the linewidth corrected for the inclination. Total magnitude, the Galactic and internal extinction corrections and radial velocity corrected to the Galactic Standard of Rest are taken from the Third Reference Catalog of Bright Galaxies(RC3) (de Vaucouleurs et al. 1991).

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© European Southern Observatory (ESO) 1997

Online publication: April 8, 1998