A panchromatic study of BLAST counterparts: total star-formation rate, morphology, AGN fraction and stellar mass

TL;DR

This study analyzes BLAST-detected galaxies across multiple wavelengths to understand their star formation, morphology, AGN presence, and stellar mass, revealing insights into galaxy evolution and the nature of submillimeter sources.

Contribution

It introduces a Monte Carlo method for deboosting FIR luminosities and provides a comprehensive multi-wavelength analysis of BLAST counterparts, linking them to other galaxy populations.

Findings

Star formation is heavily obscured at high FIR luminosities and redshifts.

Approximately 20% of galaxies show signs of AGN activity, mainly star formation-driven.

BLAST counterparts at z<1 are typical star-forming spirals with intermediate stellar masses.

Abstract

We carry out a multi-wavelength study of individual galaxies detected by the Balloon-borne Large Aperture Submillimeter Telescope (BLAST) and identified at other wavelengths, using data spanning the radio to the ultraviolet (UV). We develop a Monte Carlo method to account for flux boosting, source blending, and correlations among bands, which we use to derive deboosted far-infrared (FIR) luminosities for our sample. We estimate total star-formation rates for BLAST counterparts with z < 0.9 by combining their FIR and UV luminosities. Star formation is heavily obscured at L_FIR > 10^11 L_sun, z > 0.5, but the contribution from unobscured starlight cannot be neglected at L_FIR < 10^11 L_sun, z < 0.25. We assess that about 20% of the galaxies in our sample show indication of a type-1 active galactic nucleus (AGN), but their submillimeter emission is mainly due to star formation in the host galaxy. We compute stellar masses for a subset of 92 BLAST counterparts; these are relatively massive objects, with a median mass of ~10^11 M_sun, which seem to link the 24um and SCUBA populations, in terms of both stellar mass and star-formation activity. The bulk of the BLAST counterparts at z<1 appear to be run-of-the-mill star-forming galaxies, typically spiral in shape, with intermediate stellar masses and practically constant specific star-formation rates. On the other hand, the high-z tail of the BLAST counterparts significantly overlaps with the SCUBA population, in terms of both star-formation rates and stellar masses, with observed trends of specific star-formation rate that support strong evolution and downsizing.