Evolutionary Constraints for Submillimeter Galaxies From
Uncontaminated Estimates of Stellar Mass and Luminosity
Laura Hainline (U Maryland)
We have carried out a Spitzer IRAC and MIPS survey of a sample of 70 submillimeter-selected galaxies (SMGs) with accurate spectroscopic redshifts. The availability of spectroscopic redshifts significantly enhances our ability to determine unambiguously the intrinsic properties of SMGs such as mass and luminosity, from which we can make inferences about the star formation history and future evolution of SMGs. The rest-frame near-IR colors of our sample imply that hot dust emission contributes non-negligibly to the near-IR flux of a significant fraction of our SMG sample. When we remove the best-fit power-law contributions to the IRAC (rest-frame near-IR) fluxes, we obtain a lower median stellar mass for SMGs than previous studies. Our new, lower stellar mass estimates suggest that X-ray detected SMGs fall closer to the local relation between bulge mass and central black hole mass than previous studies indicate.
We combine our stellar mass estimates with molecular gas and dynamical mass estimates for individual SMGs in the sample observed in CO rotational emission lines to place constraints on the future of star formation in SMGs. The results suggest that these galaxies are unlikely to increase their stellar mass by more than a factor of 2 in the burst of star formation we observe, and that the typical baryonic mass of SMGs is inconsistent with the monolithic formation of giant elliptical galaxies. We also compare the stellar masses and mid-IR colors of our sample of SMGs to those of high-redshift ultraviolet/optically-selected galaxies and powerful radio galaxies with spectroscopic redshifts. Our comparisons suggest that SMGs are among the more massive galaxies of their epoch, but not necessarily the most massive, as has been suggested in the literature.
Host: K. Menendez-Delmestre
Uncontaminated Estimates of Stellar Mass and Luminosity
Laura Hainline (U Maryland)
We have carried out a Spitzer IRAC and MIPS survey of a sample of 70 submillimeter-selected galaxies (SMGs) with accurate spectroscopic redshifts. The availability of spectroscopic redshifts significantly enhances our ability to determine unambiguously the intrinsic properties of SMGs such as mass and luminosity, from which we can make inferences about the star formation history and future evolution of SMGs. The rest-frame near-IR colors of our sample imply that hot dust emission contributes non-negligibly to the near-IR flux of a significant fraction of our SMG sample. When we remove the best-fit power-law contributions to the IRAC (rest-frame near-IR) fluxes, we obtain a lower median stellar mass for SMGs than previous studies. Our new, lower stellar mass estimates suggest that X-ray detected SMGs fall closer to the local relation between bulge mass and central black hole mass than previous studies indicate.
We combine our stellar mass estimates with molecular gas and dynamical mass estimates for individual SMGs in the sample observed in CO rotational emission lines to place constraints on the future of star formation in SMGs. The results suggest that these galaxies are unlikely to increase their stellar mass by more than a factor of 2 in the burst of star formation we observe, and that the typical baryonic mass of SMGs is inconsistent with the monolithic formation of giant elliptical galaxies. We also compare the stellar masses and mid-IR colors of our sample of SMGs to those of high-redshift ultraviolet/optically-selected galaxies and powerful radio galaxies with spectroscopic redshifts. Our comparisons suggest that SMGs are among the more massive galaxies of their epoch, but not necessarily the most massive, as has been suggested in the literature.
Host: K. Menendez-Delmestre