Emission-line galaxies from SDSS DR4: Statistical studies of the current star formation

2015

Astron Nachr

Self Cite

We analyse the properties of the 1.4 GHz continuum emission in 52 star-forming compact luminous galaxies (LCGs). The fluxes of the 1.4 GHz thermal (free-free) component are derived from the extinction-and aperture-corrected fluxes of the Hα emission line. The fraction of the thermal 1.4 GHz emission is shown to be in the range of 2-52 % with a median value of about 15-17 %, and its distribution is close to a log-normal one. Both the thermal and non-thermal radio continuum luminosities are shown to be proportional to the masses of the young stellar population of the LCGs. We discuss the approximation of the ratio of the 1.4 GHz luminosity-to-the mass of the young stellar population as a function of starburst age. The derived approximation is shown to be similar but less clearly defined compared to ones obtained previously for LCGs from their Hα and UV continuum luminosities.

Section: Radio Free-free Emissionsupporting

confidence: 88%

“…2 we plot the integral distribution of galaxies from the entire LCG sample and for the subsample with the 1.4 GHz detections. The star formation rates (SFRs) of LGCs are calculated from their Hα and 1.4 GHz luminosities according to Kennicutt (1998) and Izotova & Izotov (1999), respectively:…”

Section: The 14 Ghz Subsamplementioning

confidence: 99%

Radio emission at 1.4 GHz from luminous compact galaxies

2015

Astron Nachr

Self Cite

Hα and UV luminosities and star formation rates in a large sample of luminous compact galaxies

Izotov

2012

Astrophys Space Sci

Self Cite

We present the results of a statistical study of the star formation rates (SFR) derived from the Galaxy Evolution Explorer (GALEX) observations in the ultraviolet continuum and in the Hα emission line for a sample of about 800 luminous compact galaxies (LCGs). Galaxies in this sample have a compact structure and include one or several regions of active star formation. Global galaxy characteristics (metallicity, luminosity, stellar mass) are intermediate between ones of the nearby blue compact dwarf (BCD) galaxies and Lyman-break galaxies (LBGs) at high redshifts z > 2 -3. SFRs were corrected for interstellar extinction which was derived from the optical Sloan Digital Sky Survey (SDSS) spectra. We find that SFRs derived from the galaxy luminosities in the far ultraviolet (FUV) and near ultraviolet (NUV) ranges vary in a wide range from 0.18 M ⊙ yr −1 to 113 M ⊙ yr −1 with median values of 3.8 M ⊙ yr −1 and 5.2 M ⊙ yr −1 , respectively. Simple regression relations are found for luminosities L(Hα) and L(UV) as functions of the mass of the young stellar population, the starburst age, and the galaxy metallicity. We consider the evolution of L(Hα), L(FUV) and L(NUV) with a starburst age and introduce new characteristics of star formation, namely the initial Hα, FUV and NUV luminosities at zero starburst age.

Cоmpact star-forming galaxies: the fraction of thermal emission in the radio continuum at 1.4 GHz

2018

BTSNUA

The fraction of thermal (free-free) emission in the radio continuum at the frequency of 1.4 GHz is derived in 193 compact star-forming galaxies(CSFG). These galaxies with detected radio emission represent the subsample of a larger CSFG sample of about 14 000 galaxies (Izotov, Y.I., Guseva, N.G., Fricke, K.J., Henkel, C.: Mon. Not. R. Astron. Soc. 2016, 462, 4427) selected from the Data Release 12 of the Sloan Digital Sky Survey(SDSS) (Alam, S., et al.: Astrophys. J. Suppl. Ser. 219, 12, 2015). We use the 1.4 GHz fluxes from the FIRST (Becker R.H., White R.L., & Helfand D.J.: 1995, ApJ, 450, 559) and NVSS (Condon, J.J., Cotton, W.D., Greisen, E.W., et al.: 1998, AJ, 115, 1693) catalogues. The fluxes of the thermal component at 1.4 GHz are derived from the extinction- and aperture-corrected fluxes of the Hβ emission line in the SDSS spectra following to (Caplan, J., & Deharveng, L.: 1986, A&A, 155, 297) and are compared with the total fluxes in radio continuum. The distribution of the fraction of thermal emission A at 1.4 GHz is similar to the log-normal one. Its median values of 6 % and 14 % are derived respectively with the Hβemission line fluxes which are non-corrected and corrected for aperture. We consider these values as lower and upper limits and discuss their uncertainties introduced by aperture corrections. The derived fractions of thermal emission are similar to those found previously for different types of star-forming galaxies. We study the dependence of A on various parameters and find strong correlation with the equivalent width of the Hβ emission line W and the gr colour index I. The A value increases with increasing of the equivalent width W at a fixed colour index I or with increasing of the colour index I at a fixed equivalent width W. Additionally, we find that the fraction of thermal emission at 1.4 GHz is lower for older starbursts.