Measures of galaxy dust and gas mass with Herschel photometry and prospects for ALMA

TL;DR

This study assesses methods for estimating galaxy dust and gas masses using Herschel photometry, demonstrating the robustness of these estimates across different models and redshifts, and exploring prospects for ALMA observations.

Contribution

It compares two popular dust mass estimation methods, evaluates their accuracy with Herschel data, and discusses implications for future ALMA observations.

Findings

Dust mass can be reliably estimated if SED extends to 160-200 microns.

An offset of ~1.5 exists between DL07 and MBB dust mass estimates.

Dust and gas mass estimates are consistent with other scaling relations.

Abstract

(Abridged) Combining the deepest Herschel extragalactic surveys (PEP, GOODS-H, HerMES), and Monte Carlo mock catalogs, we explore the robustness of dust mass estimates based on modeling of broad band spectral energy distributions (SEDs) with two popular approaches: Draine & Li (2007, DL07) and a modified black body (MBB). As long as the observed SED extends to at least 160-200 micron in the rest frame, M(dust) can be recovered with a >3 sigma significance and without the occurrence of systematics. An average offset of a factor ~1.5 exists between DL07- and MBB-based dust masses, based on consistent dust properties. At the depth of the deepest Herschel surveys (in the GOODS-S field) it is possible to retrieve dust masses with a S/N>=3 for galaxies on the main sequence of star formation (MS) down to M(stars)~1e10 [M(sun)] up to z~1. At higher redshift (z<=2) the same result is achieved only for objects at the tip of the MS or lying above it. Molecular gas masses, obtained converting M(dust) through the metallicity-dependent gas-to-dust ratio delta(GDR), are consistent with those based on the scaling of depletion time, and on CO spectroscopy. Focusing on CO-detected galaxies at z>1, the delta(GDR) dependence on metallicity is consistent with the local relation. We combine far-IR Herschel data and sub-mm ALMA expected fluxes to study the advantages of a full SED coverage.