Abstract
(abridged) We studied a large sample of ~14000 dwarf star-forming galaxies with strong emission lines selected from the Sloan Digital Sky Survey (SDSS) and distributed in the redshift range of z~0-0.6. We modelled spectral energy distributions (SED) of all galaxies which were based on the SDSS spectra in the visible range of 0.38-0.92 micron and included both the stellar and ionised gas emission. These SEDs were extrapolated to the UV and mid-infrared ranges to cover the wavelength range of 0.1-22 micron. The SDSS spectroscopic data were supplemented by photometric data from the GALEX, SDSS, 2MASS, WISE, IRAS, and NVSS all-sky surveys. We derived global characteristics of the galaxies, such as their element abundances, luminosities, and stellar masses. The luminosities and stellar masses range within the sample over ~5 orders of magnitude, thereby linking low-mass and low-luminosity blue compact dwarf (BCD) galaxies to luminous galaxies, which are similar to high-redshift Lyman-break galaxies (LBGs). The luminosity L(Hbeta) of the Hbeta emission line, a characteristic of the youngest stellar population with an age of a few Myr, is correlated with luminosities in other wavelength ranges. This implies that the most recent burst of star formation makes a significant contribution to the emission in the visible range and dominates in other wavelength ranges. We found 20 galaxies with very red WISE mid-infrared m(3.4micron)-m(4.6micron) colour (>2 mag), which suggests the important contribution of the hot (with a temperature of several hundred degree) dust emission in these galaxies. Our analysis of the balance between the luminosity in the WISE bands that covered a wavelength range of 3.4-22 micron and the luminosity of the emission absorbed at shorter wavelengths showed that the luminosity of the hot dust emission is increased with increasing L(Hbeta) and EW(Hbeta).
Highlights
The problems related to the formation of first galaxies at high redshifts from nearly pristine gas and the determination of their physical properties were extensively studied in recent years (e.g., Pettini et al 2001; Stark et al 2009; Erb et al 2010; Schaerer & de Barros 2010)
We modelled spectral energy distributions (SED) of all galaxies, which were based on the Sloan Digital Sky Survey (SDSS) spectra in the visible range of 0.38 μm−0.92 μm and included both the stellar and ionised gas emission
These data are supplemented by data from the Galaxy Evolution Explorer (GALEX) survey in the UV range, the 2MASS survey in the nearinfrared range, the WISE survey in the mid-infrared range, the IRAS survey in the far-infrared range, and the NRAO VLA Sky Survey (NVSS) survey in the radio continuum at 20 cm
Summary
The problems related to the formation of first galaxies at high redshifts from nearly pristine gas and the determination of their physical properties were extensively studied in recent years (e.g., Pettini et al 2001; Stark et al 2009; Erb et al 2010; Schaerer & de Barros 2010). The completion of the space GALEX survey in the UV range (Morrissey et al 2007), the Sloan Digital Sky Survey (SDSS) in the visible range (Abazajian et al 2009), the 2MASS survey in the near-infrared range (Skrutskie et al 2006), the space Widefield Infrared Survey Explorer survey (WISE, Wright et al 2010), and the NRAO VLA Sky Survey (NVSS) in the radio continuum at 20 cm (Condon et al 1998) opened the opportunity to study properties of large samples of star-forming galaxies over the extremely large wavelength range of ∼0.15 μm−20 cm We used all these data bases with the aim to fit spectral energy distributions (SEDs) in ∼14 000 star-forming galaxies with strong emission lines to derive global characteristics of the galaxies and the relations between them
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