The SAMI Galaxy Survey: a new method to estimate molecular gas surface densities from star formation rates
Stars form in cold molecular clouds. However, molecular gas is difficult to observe because the most abundant molecule (H_2) lacks a permanent dipole moment. Rotational transitions of CO are often used as a tracer of H_2, but CO is much less abundant and the conversion from CO intensity to H2 mass i...
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ftcaltechauth:oai:authors.library.caltech.edu:9gnjz-4yg09 2024-06-23T07:56:32+00:00 The SAMI Galaxy Survey: a new method to estimate molecular gas surface densities from star formation rates Federrath, Christoph Salim, Diane M. Medling, Anne M. Davies, Rebecca L. Yuan, Tiantian Bian, Fuyan Groves, Brent A. Ho, I-Ting Sharp, Robert Kewley, Lisa J. Sweet, Sarah M. Richards, Samuel N. Bryant, Julia J. Brough, Sarah Croom, Scott Scott, Nicholas Lawrence, Jon Konstantopoulos, Iraklis Goodwin, Michael 2017-07 https://doi.org/10.1093/mnras/stx727 unknown Royal Astronomical Society https://arxiv.org/abs/1703.09224 https://doi.org/10.1093/mnras/stx727 oai:authors.library.caltech.edu:9gnjz-4yg09 eprintid:78696 resolverid:CaltechAUTHORS:20170629-124334903 info:eu-repo/semantics/openAccess Other Monthly Notices of the Royal Astronomical Society, 468(4), 3965-3978, (2017-07) turbulence techniques: spectroscopic stars: formation galaxies: ISM galaxies: star formation galaxies: structure info:eu-repo/semantics/article 2017 ftcaltechauth https://doi.org/10.1093/mnras/stx727 2024-06-12T02:13:56Z Stars form in cold molecular clouds. However, molecular gas is difficult to observe because the most abundant molecule (H_2) lacks a permanent dipole moment. Rotational transitions of CO are often used as a tracer of H_2, but CO is much less abundant and the conversion from CO intensity to H2 mass is often highly uncertain. Here we present a new method for estimating the column density of cold molecular gas (Σ_(gas)) using optical spectroscopy. We utilize the spatially resolved Hα maps of flux and velocity dispersion from the Sydney-AAO Multi-object Integral field spectrograph (SAMI) Galaxy Survey. We derive maps of Σ_(gas) by inverting the multi-freefall star formation relation, which connects the star formation rate surface density (Σ_(SFR)) with Σ_(gas) and the turbulent Mach number (M). Based on the measured range of Σ_(SFR) = 0.005-1.5M⊙ yr^(−1) kpc^(−2) and M=18–130, we predict Σ_(gas) = 7–200 M⊙ pc^(−2) in the star-forming regions of our sample of 260 SAMI galaxies. These values are close to previously measured Σ_(gas) obtained directly with unresolved CO observations of similar galaxies at low redshift. We classify each galaxy in our sample as 'star-forming' (219) or 'composite/AGN/shock' (41), and find that in 'composite/AGN/shock' galaxies the average Σ_(SFR), M and Σ_(gas) are enhanced by factors of 2.0, 1.6 and 1.3, respectively, compared to star-forming galaxies. We compare our predictions of Σ_(gas) with those obtained by inverting the Kennicutt–Schmidt relation and find that our new method is a factor of 2 more accurate in predicting Σ_(gas), with an average deviation of 32 per cent from the actual Σ_(gas). © 2017 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. Accepted 2017 March 22. Received 2017 March 19; in original form 2016 October 15. Published: 27 March 2017. We thank Mark Krumholz and the anonymous referee for their useful comments, which helped to improve this work. CF acknowledges funding provided by the ... Article in Journal/Newspaper sami Caltech Authors (California Institute of Technology) Monthly Notices of the Royal Astronomical Society 468 4 3965 3978 |
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Caltech Authors (California Institute of Technology) |
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topic |
turbulence techniques: spectroscopic stars: formation galaxies: ISM galaxies: star formation galaxies: structure |
spellingShingle |
turbulence techniques: spectroscopic stars: formation galaxies: ISM galaxies: star formation galaxies: structure Federrath, Christoph Salim, Diane M. Medling, Anne M. Davies, Rebecca L. Yuan, Tiantian Bian, Fuyan Groves, Brent A. Ho, I-Ting Sharp, Robert Kewley, Lisa J. Sweet, Sarah M. Richards, Samuel N. Bryant, Julia J. Brough, Sarah Croom, Scott Scott, Nicholas Lawrence, Jon Konstantopoulos, Iraklis Goodwin, Michael The SAMI Galaxy Survey: a new method to estimate molecular gas surface densities from star formation rates |
topic_facet |
turbulence techniques: spectroscopic stars: formation galaxies: ISM galaxies: star formation galaxies: structure |
description |
Stars form in cold molecular clouds. However, molecular gas is difficult to observe because the most abundant molecule (H_2) lacks a permanent dipole moment. Rotational transitions of CO are often used as a tracer of H_2, but CO is much less abundant and the conversion from CO intensity to H2 mass is often highly uncertain. Here we present a new method for estimating the column density of cold molecular gas (Σ_(gas)) using optical spectroscopy. We utilize the spatially resolved Hα maps of flux and velocity dispersion from the Sydney-AAO Multi-object Integral field spectrograph (SAMI) Galaxy Survey. We derive maps of Σ_(gas) by inverting the multi-freefall star formation relation, which connects the star formation rate surface density (Σ_(SFR)) with Σ_(gas) and the turbulent Mach number (M). Based on the measured range of Σ_(SFR) = 0.005-1.5M⊙ yr^(−1) kpc^(−2) and M=18–130, we predict Σ_(gas) = 7–200 M⊙ pc^(−2) in the star-forming regions of our sample of 260 SAMI galaxies. These values are close to previously measured Σ_(gas) obtained directly with unresolved CO observations of similar galaxies at low redshift. We classify each galaxy in our sample as 'star-forming' (219) or 'composite/AGN/shock' (41), and find that in 'composite/AGN/shock' galaxies the average Σ_(SFR), M and Σ_(gas) are enhanced by factors of 2.0, 1.6 and 1.3, respectively, compared to star-forming galaxies. We compare our predictions of Σ_(gas) with those obtained by inverting the Kennicutt–Schmidt relation and find that our new method is a factor of 2 more accurate in predicting Σ_(gas), with an average deviation of 32 per cent from the actual Σ_(gas). © 2017 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. Accepted 2017 March 22. Received 2017 March 19; in original form 2016 October 15. Published: 27 March 2017. We thank Mark Krumholz and the anonymous referee for their useful comments, which helped to improve this work. CF acknowledges funding provided by the ... |
format |
Article in Journal/Newspaper |
author |
Federrath, Christoph Salim, Diane M. Medling, Anne M. Davies, Rebecca L. Yuan, Tiantian Bian, Fuyan Groves, Brent A. Ho, I-Ting Sharp, Robert Kewley, Lisa J. Sweet, Sarah M. Richards, Samuel N. Bryant, Julia J. Brough, Sarah Croom, Scott Scott, Nicholas Lawrence, Jon Konstantopoulos, Iraklis Goodwin, Michael |
author_facet |
Federrath, Christoph Salim, Diane M. Medling, Anne M. Davies, Rebecca L. Yuan, Tiantian Bian, Fuyan Groves, Brent A. Ho, I-Ting Sharp, Robert Kewley, Lisa J. Sweet, Sarah M. Richards, Samuel N. Bryant, Julia J. Brough, Sarah Croom, Scott Scott, Nicholas Lawrence, Jon Konstantopoulos, Iraklis Goodwin, Michael |
author_sort |
Federrath, Christoph |
title |
The SAMI Galaxy Survey: a new method to estimate molecular gas surface densities from star formation rates |
title_short |
The SAMI Galaxy Survey: a new method to estimate molecular gas surface densities from star formation rates |
title_full |
The SAMI Galaxy Survey: a new method to estimate molecular gas surface densities from star formation rates |
title_fullStr |
The SAMI Galaxy Survey: a new method to estimate molecular gas surface densities from star formation rates |
title_full_unstemmed |
The SAMI Galaxy Survey: a new method to estimate molecular gas surface densities from star formation rates |
title_sort |
sami galaxy survey: a new method to estimate molecular gas surface densities from star formation rates |
publisher |
Royal Astronomical Society |
publishDate |
2017 |
url |
https://doi.org/10.1093/mnras/stx727 |
genre |
sami |
genre_facet |
sami |
op_source |
Monthly Notices of the Royal Astronomical Society, 468(4), 3965-3978, (2017-07) |
op_relation |
https://arxiv.org/abs/1703.09224 https://doi.org/10.1093/mnras/stx727 oai:authors.library.caltech.edu:9gnjz-4yg09 eprintid:78696 resolverid:CaltechAUTHORS:20170629-124334903 |
op_rights |
info:eu-repo/semantics/openAccess Other |
op_doi |
https://doi.org/10.1093/mnras/stx727 |
container_title |
Monthly Notices of the Royal Astronomical Society |
container_volume |
468 |
container_issue |
4 |
container_start_page |
3965 |
op_container_end_page |
3978 |
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1802649676110888960 |