A Census of Star-formation and Gas Mass Tracers in Two Lensed <i>z</i>  ∼ 4 Dusty Star-forming Galaxies

Abstract We present new and archival Atacama Large Millimeter/submillimeter Array observations of two strongly lensed dusty star-forming galaxies (DSFGs) selected from the South Pole Telescope survey, SPT0418-47 ( z = 4.225) and SPT2147-50 ( z = 3.760). We study the [C ii ], CO(7–6), [C i ](2–1), and, in SPT0418-47, p –H 2 O emission, which, along with the underlying continuum (rest-frame 160 and 380 μ m), are routinely used as tracers of gas mass and/or star-formation rate (SFR). We perform a pixel-by-pixel analysis of both sources in the image plane to study the resolved Kennicutt–Schmidt relation, finding generally good agreement between the slopes of the SFR versus gas mass surface density using the different tracers. Using lens modeling methods, we find that the dust emission is more compact than the line emission in both sources, with CO(7–6) and [C i ](2–1) similar in extent and [C ii ] the most extended, reminiscent of recent findings of extended [C ii ] spatial distributions in galaxies at similar cosmic epochs. We develop the [C i ](2–1)/ CO(7–6) flux-density ratio as an observable proxy for gas depletion timescale ( τ dep ), which can be applied to large samples of DSFGs, in lieu of more detailed inferences of this timescale, which require analysis of observations at multiple wavelengths. Furthermore, the extended [C ii ] emission in both sources, compared to the total continuum and line emission, suggests that [C ii ], used in recent years as a molecular gas mass and SFR tracer in high- z galaxies, may not always be a suitable tracer of these physical quantities.

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Journal
The Astrophysical Journal
Published
2026-02-26
DOI
https://doi.org/10.3847/1538-4357/ae3744
Primary Topic
Astrophysics and Star Formation Studies
Type
article
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article

A Census of Star-formation and Gas Mass Tracers in Two Lensed z  ∼ 4 Dusty Star-forming Galaxies

Ana C. Posses, Gayathri Gururajan, M. Archipley, Vismaya R. Pillai et al.
The Astrophysical Journal
Astrophysics and Star Formation Studies
article

A Census of Star-formation and Gas Mass Tracers in Two Lensed z  ∼ 4 Dusty Star-forming Galaxies

Ana C. Posses, Gayathri Gururajan, M. Archipley, Vismaya R. Pillai, S. Birrer, Kedar A. Phadke, Ryley Hill, Jack E. Birkin, Desika Narayanan, Nikolaus Sulzenauer, Manuel Solimano, Veronica Dike, Manuel Aravena, Jared Cathey, Dazhi Zhou, Matthew Malkan, David Vizgan, Justin Spilker, Nan Zhang, Thomas R. Greve, Anthony H. Gonzalez, Scott C. Chapman, Joaquin D. Vieira
article en

Abstract

Abstract We present new and archival Atacama Large Millimeter/submillimeter Array observations of two strongly lensed dusty star-forming galaxies (DSFGs) selected from the South Pole Telescope survey, SPT0418-47 ( z = 4.225) and SPT2147-50 ( z = 3.760). We study the [C ii ], CO(7–6), [C i ](2–1), and, in SPT0418-47, p –H 2 O emission, which, along with the underlying continuum (rest-frame 160 and 380 μ m), are routinely used as tracers of gas mass and/or star-formation rate (SFR). We perform a pixel-by-pixel analysis of both sources in the image plane to study the resolved Kennicutt–Schmidt relation, finding generally good agreement between the slopes of the SFR versus gas mass surface density using the different tracers. Using lens modeling methods, we find that the dust emission is more compact than the line emission in both sources, with CO(7–6) and [C i ](2–1) similar in extent and [C ii ] the most extended, reminiscent of recent findings of extended [C ii ] spatial distributions in galaxies at similar cosmic epochs. We develop the [C i ](2–1)/ CO(7–6) flux-density ratio as an observable proxy for gas depletion timescale ( τ dep ), which can be applied to large samples of DSFGs, in lieu of more detailed inferences of this timescale, which require analysis of observations at multiple wavelengths. Furthermore, the extended [C ii ] emission in both sources, compared to the total continuum and line emission, suggests that [C ii ], used in recent years as a molecular gas mass and SFR tracer in high- z galaxies, may not always be a suitable tracer of these physical quantities.

The Astrophysical JournalVol. 999(1)
University of Copenhagen (DK), Dalhousie University (CA), Scuola Internazionale Superiore di Studi Avanzati (IT), University of British Columbia (CA), University of Illinois Urbana-Champaign (US), University of California, Los Angeles (US), Chestnut Hill College (US), Mitchell Institute (US), University of Florida (US), University of Chicago (US), Millennium Nucleus of Ion Channel Associated Diseases (CL), Centro de Astrobiología (ES), National Center for Supercomputing Applications (US), Eureka Scientific (US), Institute for Fundamental Physics of the Universe (IT), Millenium Nucleus for Planet Formation (CL), Max Planck Institute for Radio Astronomy (DE), Stony Brook University (US), Texas A&M University (US), Universidad Diego Portales (CL), Technical University of Denmark (DK)
Openalex Percentile: Top 42%
Astrophysics and Star Formation Studies
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