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 (H2) lacks a permanent dipole moment. Rotational transitions of CO are often used as a tracer of H2, but CO is much less abundant and the conversion from CO intensity to H2 mass is...
Published in: | Monthly Notices of the Royal Astronomical Society |
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Oxford University Press (OUP)
2017
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Online Access: | http://hdl.handle.net/1959.3/435915 https://doi.org/10.1093/mnras/stx727 |
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ftswinburne:tle:69b13a3d-5d2f-463f-ad58-440b2e30d21c:28f49f06-0da8-44be-9edc-ad1dd0a9c582:1 2023-05-15T18:11:25+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 Swinburne University of Technology 2017 http://hdl.handle.net/1959.3/435915 https://doi.org/10.1093/mnras/stx727 unknown Oxford University Press (OUP) http://hdl.handle.net/1959.3/435915 https://doi.org/10.1093/mnras/stx727 This article has been accepted for publication in the Monthly Notices of the Royal Astronomical Society ©: 2017 the authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved. Monthly Notices of the Royal Astronomical Society, Vol. 468, no. 4 (Jul 2017), pp. 3965-3978 Journal article 2017 ftswinburne https://doi.org/10.1093/mnras/stx727 2019-09-07T22:24:10Z Stars form in cold molecular clouds. However, molecular gas is difficult to observe because the most abundant molecule (H2) lacks a permanent dipole moment. Rotational transitions of CO are often used as a tracer of H2, 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 (Σgas) 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 Σgas by inverting the multi-freefall star formation relation, which connects the star formation rate surface density (ΣSFR) with Σgas and the turbulent Mach number ( M ). Based on the measured range of ΣSFR = 0.005– 1.5M⊙yr−1kpc−2 and M=18 –130, we predict Σgas = 7– 200M⊙pc−2 in the star-forming regions of our sample of 260 SAMI galaxies. These values are close to previously measured Σgas 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 ΣSFR, M and Σgas are enhanced by factors of 2.0, 1.6 and 1.3, respectively, compared to star-forming galaxies. We compare our predictions of Σgas with those obtained by inverting the Kennicutt–Schmidt relation and find that our new method is a factor of 2 more accurate in predicting Σgas, with an average deviation of 32 per cent from the actual Σgas. Article in Journal/Newspaper sami Swinburne University of Technology: Swinburne Research Bank Monthly Notices of the Royal Astronomical Society 468 4 3965 3978 |
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Swinburne University of Technology: Swinburne Research Bank |
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ftswinburne |
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unknown |
description |
Stars form in cold molecular clouds. However, molecular gas is difficult to observe because the most abundant molecule (H2) lacks a permanent dipole moment. Rotational transitions of CO are often used as a tracer of H2, 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 (Σgas) 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 Σgas by inverting the multi-freefall star formation relation, which connects the star formation rate surface density (ΣSFR) with Σgas and the turbulent Mach number ( M ). Based on the measured range of ΣSFR = 0.005– 1.5M⊙yr−1kpc−2 and M=18 –130, we predict Σgas = 7– 200M⊙pc−2 in the star-forming regions of our sample of 260 SAMI galaxies. These values are close to previously measured Σgas 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 ΣSFR, M and Σgas are enhanced by factors of 2.0, 1.6 and 1.3, respectively, compared to star-forming galaxies. We compare our predictions of Σgas with those obtained by inverting the Kennicutt–Schmidt relation and find that our new method is a factor of 2 more accurate in predicting Σgas, with an average deviation of 32 per cent from the actual Σgas. |
author2 |
Swinburne University of Technology |
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 |
spellingShingle |
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 |
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 (OUP) |
publishDate |
2017 |
url |
http://hdl.handle.net/1959.3/435915 https://doi.org/10.1093/mnras/stx727 |
genre |
sami |
genre_facet |
sami |
op_source |
Monthly Notices of the Royal Astronomical Society, Vol. 468, no. 4 (Jul 2017), pp. 3965-3978 |
op_relation |
http://hdl.handle.net/1959.3/435915 https://doi.org/10.1093/mnras/stx727 |
op_rights |
This article has been accepted for publication in the Monthly Notices of the Royal Astronomical Society ©: 2017 the authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved. |
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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1766184085600862208 |