Properties of Star-Forming Galaxies in the Mid-Infrared Range from the Data Obtained with the WISE Space Telescope

Abstract

We study the mid-infrared photometric properties of a sample of compact star-forming galaxies from the SDSS Data Release 14. The sample includes about 30 000 galaxies. The H_β emission lines with equivalent widths EW(H_β) > 1 nm are observed in the spectra of all selected galaxies. The selected galaxies are compact objects with angular diameters less than 6 arcsec. About 10 000 galaxies were detected by the WISE space telescope at wavelengths of 3.4 and 4.6 μm. A considerable number of galaxies was also detected at wavelengths of 12 and 22 μm. Using these data and the results of observations obtained in the ultraviolet range with the GALEX space telescope, it was shown that the heating of dust in the sample of galaxies is caused by the ultraviolet radiation of massive stars in the star-forming regions. The stellar and ionized-gas emission dominates at wavelengths of 3.4 and 4.6 μm in a majority of galaxies, whereas the dust emission dominates at wavelengths of 12 and 22 μm. In some galaxies with high H_β luminosity, dust emission is observed even at the short wavelength of 3.4 μm, and it has a steep increase in the intensity toward the wavelength of 4.6 μm. This emission is characterized by “red” color (W1 – W2 > 2^m), where W1 and W2 are magnitudes at wavelengths of 3.4 and 4.6 μm, respectively. The probable cause of this emission is the presence of hot dust with a temperature of hundreds of Kelvins. A list of 39 galaxies with such an extremely high W1 – W2 color index is presented.