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 H-2 mass...
Published in: | Monthly Notices of the Royal Astronomical Society |
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Oxford University Press
2017
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ftunivqespace:oai:espace.library.uq.edu.au:UQ:44d4653 2023-05-15T18:11:29+02:00 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 2017-07-01 https://espace.library.uq.edu.au/view/UQ:44d4653/UQ44d4653_OA.pdf https://espace.library.uq.edu.au/view/UQ:44d4653 eng eng Oxford University Press doi:10.1093/mnras/stx727 issn:0035-8711 issn:1365-2966 orcid:0000-0002-1576-2505 DP150104329 HST-HF2-51377 NAS5-26555 FT140101202 FT140101166 FT100100457 CE110001020 Mass Assembly Gama Modeling Co Emission On Spiral Galaxies Formation Law Milky-Way Interstellar Turbulence Nearby Galaxies Data Release 3-Dimensional Distribution Probability-Distribution Journal Article 2017 ftunivqespace https://doi.org/10.1093/mnras/stx727 2020-12-08T07:55:29Z 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 H-2 mass is often highly uncertain. Here we present a new method for estimating the column density of cold molecular gas (Sigma(gas)) using optical spectroscopy. We utilize the spatially resolved H alpha maps of flux and velocity dispersion from the Sydney-AAO Multi-object Integral field spectrograph (SAMI) Galaxy Survey. We derive maps of Sigma(gas) by inverting the multi-freefall star formation relation, which connects the star formation rate surface density (Sigma(SFR)) with Sigma(gas) and the turbulent Mach number (M). Based on the measured range of Sigma(SFR) = 0.005-1.5M(circle dot)yr(-1) kpc(-2) and M = 18-130, we predict Sigma(gas) = 7-200M(circle dot)pc(-2) in the star-forming regions of our sample of 260 SAMI galaxies. These values are close to previously measured Sigma(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 Sigma(SFR), M and Sigma(gas) are enhanced by factors of 2.0, 1.6 and 1.3, respectively, compared to star-forming galaxies. We compare our predictions of Sigma(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 Sigma(gas), with an average deviation of 32 per cent from the actual Sigma(gas). Article in Journal/Newspaper sami The University of Queensland: UQ eSpace Milky Way ENVELOPE(-68.705,-68.705,-71.251,-71.251) Monthly Notices of the Royal Astronomical Society 468 4 3965 3978 |
institution |
Open Polar |
collection |
The University of Queensland: UQ eSpace |
op_collection_id |
ftunivqespace |
language |
English |
topic |
Mass Assembly Gama Modeling Co Emission On Spiral Galaxies Formation Law Milky-Way Interstellar Turbulence Nearby Galaxies Data Release 3-Dimensional Distribution Probability-Distribution |
spellingShingle |
Mass Assembly Gama Modeling Co Emission On Spiral Galaxies Formation Law Milky-Way Interstellar Turbulence Nearby Galaxies Data Release 3-Dimensional Distribution Probability-Distribution 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 |
Mass Assembly Gama Modeling Co Emission On Spiral Galaxies Formation Law Milky-Way Interstellar Turbulence Nearby Galaxies Data Release 3-Dimensional Distribution Probability-Distribution |
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 H-2 mass is often highly uncertain. Here we present a new method for estimating the column density of cold molecular gas (Sigma(gas)) using optical spectroscopy. We utilize the spatially resolved H alpha maps of flux and velocity dispersion from the Sydney-AAO Multi-object Integral field spectrograph (SAMI) Galaxy Survey. We derive maps of Sigma(gas) by inverting the multi-freefall star formation relation, which connects the star formation rate surface density (Sigma(SFR)) with Sigma(gas) and the turbulent Mach number (M). Based on the measured range of Sigma(SFR) = 0.005-1.5M(circle dot)yr(-1) kpc(-2) and M = 18-130, we predict Sigma(gas) = 7-200M(circle dot)pc(-2) in the star-forming regions of our sample of 260 SAMI galaxies. These values are close to previously measured Sigma(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 Sigma(SFR), M and Sigma(gas) are enhanced by factors of 2.0, 1.6 and 1.3, respectively, compared to star-forming galaxies. We compare our predictions of Sigma(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 Sigma(gas), with an average deviation of 32 per cent from the actual Sigma(gas). |
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 |
Oxford University Press |
publishDate |
2017 |
url |
https://espace.library.uq.edu.au/view/UQ:44d4653/UQ44d4653_OA.pdf https://espace.library.uq.edu.au/view/UQ:44d4653 |
long_lat |
ENVELOPE(-68.705,-68.705,-71.251,-71.251) |
geographic |
Milky Way |
geographic_facet |
Milky Way |
genre |
sami |
genre_facet |
sami |
op_relation |
doi:10.1093/mnras/stx727 issn:0035-8711 issn:1365-2966 orcid:0000-0002-1576-2505 DP150104329 HST-HF2-51377 NAS5-26555 FT140101202 FT140101166 FT100100457 CE110001020 |
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 |
_version_ |
1766184141240401920 |