Studies of Second Byurakan Survey Galaxies. II. Comparison of Ultraviolet-excess and Emission-line Techniques

Details Studies of Second Byurakan Survey Galaxies. II. Comparison of Ultraviolet-excess and Emission-line Techniques Studies of Second Byurakan Survey Galaxies. II. Comparison of Ultraviolet-excess and Emission-line Techniques

Jan 2003

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2003aj....125...86p&link_type=abstract

The Astronomical Journal, Volume 125, Issue 1, pp. 86-97.

Statistics

7

Galaxies: Distances And Redshifts, Galaxies: Fundamental Parameters, Galaxies: Statistics, Radio Emission Lines, Surveys

Scientific paper

The Second Byurakan Survey (SBS) has been defined using two indicators of activity as observed on objective-prism spectra: the presence of UV excess (UVX) in the continuum, or the presence of emission lines (ELs). Of the ~3500 objects in the survey, 1401 are classified as galaxies. This paper reports on a comparative study of 524 UVX SBS galaxies and 340 EL SBS galaxies. The parameters used for the comparison were apparent magnitude, redshift, spectral class, luminosity, morphology, activity type, and close environment. The main results are as follows:1. In comparison with the UVX method, the EL method allows the creation of a deeper sample of peculiar galaxies. The existence of the emission lines also helps to detect fainter objects among the UVX galaxies.2. The UVX method covers a larger range of redshifts than does the EL method.3. Fifty-four active galactic nuclei (AGNs) have been discovered with the UVX and 11 with the EL techniques. Among the EL sample objects, there are no Seyfert-like galaxies of type 1 or 1.5. UVX galaxies with AGNs mostly are stellar and semistellar spectral classes objects, of which the majority are strong or moderate UV-excess emitters.4. Star-forming galaxies with z<0.1 and discovered via UVX have median luminosity higher than galaxies discovered via EL. The difference is mostly caused by a higher rate of high-luminosity (M<=-21.0) galaxies in the UVX sample; these are mostly galaxies with stellar or semistellar spectra. Another contribution comes from the higher rate of low-luminosity (M>=-17.0) galaxies in the EL sample, most of which have diffuse or semidiffuse spectra.5. UVX and EL active and star-forming galaxies do not show major differences in their distribution of morphological type; in both samples, the majority of galaxies are spirals.6. The UVX and EL samples are similar in their fractions of mergers or interacting systems, as well as the incidence of close pairs or neighbors within r<50 kpc. However, the UVX galaxies with the strongest excess UV radiation are often in mergers, interacting systems, or close pairs.7. The EL method allows the creation of a sample with lower apparent magnitudes and higher redshifts among the low-luminosity (M>=-17.0) galaxies and is more efficient at discovering galaxies with compact or irregular morphology.

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