Star-formation-rate estimates from water emission

Abstract

(Abridged) The star-formation rate (SFR) quantitatively describes the star-formation process in galaxies. Current ways to calibrate this rate do not usually employ observational methods accounting for the low-mass end of stellar populations as their signatures are too weak. Accessing the bulk of protostellar activity within galactic star-forming regions can be achieved by tracing signposts of ongoing star formation. One such signpost is molecular outflows, which are bright in molecular emission. We propose to utilize the protostellar outflow emission as a tracer of the SFR. In this work, we introduce a novel version of the galaxy-in-a-box model, which can be used to relate molecular emission from star formation in galaxies with the SFR. We measured the predicted para-H2O emission at 988 GHz and corresponding SFRs for galaxies with LFIR = $10^8$ - $10^{11}$ L${}_{\odot }$ in a distance-independent manner, and compared them with expectations from observations. We evaluated the derived results by varying the star formation efficiency, the free-fall time scaling factor, and the initial mass function. For the chosen H2O transition, relying on the current Galactic observations and star formation properties, we are underestimating the total galactic emission, while overestimating the SFRs, particularly for more starburst-like configurations. The current version of the galaxy-in-a-box model accounts for a limited number of processes and configurations, that is, it focuses on ongoing star formation in massive young clusters in a spiral galaxy. Therefore, the inferred results, which underestimate the emission and overestimate the SFR, are not surprising: known sources of emission are not included in the model. To improve the results, the next version of the model needs to include a more detailed treatment of the entire galactic ecosystem and other processes that would contribute to the emission.

Accepted for publication in A&A. 11 pages, 6 figures

References in corpus (12)

• Cosmic Star Formation History
• UV Star Formation Rates in the Local Universe
• A Dust-Obscured Massive Maximum-Starburst Galaxy at a Redshift of 6.34
• The Relation Between SFR and Stellar Mass for Galaxies at 3.5 $\le z\le$ 6.5 in CANDELS
• Water in star-forming regions (WISH): Physics and chemistry from clouds to disks as probed by Herschel spectroscopy
• Outflows, infall and evolution of a sample of embedded low-mass protostars. The William Herschel Line Legacy (WILL) survey
• Submillimeter H2O and H2O+ emission in lensed ultra- and hyper-luminous infrared galaxies at z ~ 2-4
• Modeling the H2O submillimeter emission in extragalactic sources
• Herschel Far-Infrared Spectral-mapping of Orion BN/KL Outflows: Spatial distribution of excited CO, H2O, OH, O and C+ in shocked gas
• Herschel Observations of the W3 GMC: Clues to the Formation of Clusters of High-Mass Stars
• High-excitation OH and H_2O lines in Markarian 231: the molecular signatures of compact far-infrared continuum sources
• Tracing Embedded Stellar Populations in Clusters and Galaxies using Molecular Emission: Methanol as a Signature of the Low-Mass End of the IMF