The Stellar Mass Content of Submillimeter-Selected Galaxies

TL;DR

This study analyzes the stellar mass of ~70 submillimeter-selected galaxies using spectral energy distribution fitting, revealing lower stellar masses after accounting for non-stellar emission and suggesting their evolution into L* galaxies.

Contribution

It introduces a method to separate stellar from non-stellar near-IR emission in SMGs, providing more accurate stellar mass estimates and insights into their evolutionary fate.

Findings

Approximately 50% of SMGs have minimal non-stellar near-IR contributions.

A correlation exists between non-stellar K-band emission and X-ray luminosity, indicating AGN activity.

Corrected stellar masses are around 7 x 10^10 solar masses, lower than previous estimates.

Abstract

We present a new study of the stellar mass in a sample of ~ 70 submillimeter-selected galaxies (SMGs) with accurate spectroscopic redshifts. We fit combinations of stellar population synthesis models and power laws to the galaxies' observed-frame optical through mid-IR spectral energy distributions to separate stellar emission from non-stellar near-IR continuum. By separating the stellar emission from the non-stellar near-IR continuum, we find that ~ 50% of our sample have non-stellar continuum contributions of less than 10% in rest-frame H-band, but ~ 10% of our sample have non-stellar contributions greater than 50%. We find that the K-band luminosity of the non-stellar continuum emission is correlated with hard X-ray luminosity, indicating an AGN origin of the emission. Upon subtracting this AGN-contributed continuum component from all of the galaxies in our sample, we determine a lower median stellar mass for SMGs than previous studies, ~ 7 x 10^10 M_sun. We use constraints of the starburst time-scale from molecular gas studies to estimate the amount of fading our sample would undergo if they passively evolve after the starburst terminates. The results suggest that typical SMGs, while among the most massive galaxies at z ~ 2, are likely to produce descendants of similar mass and luminosity to L* galaxies in the local universe.