A high-dispersion molecular gas component in nearby galaxies

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dc.contributor.authorCaldú-Primo, Anahi
dc.contributor.authorSchruba, Andreas
dc.contributor.authorWalter, Fabian
dc.contributor.authorLeroy, Adam
dc.contributor.authorSandstrom, Karin
dc.contributor.authorde Blok, W J G
dc.contributor.authorIanjamasimanana, R
dc.contributor.authorMogotsi, K M
dc.date.accessioned2021-10-08T07:20:33Z
dc.date.available2021-10-08T07:20:33Z
dc.date.issued2013
dc.description.abstractWe present a comprehensive study of the velocity dispersion of the atomic (H I) and molecular (H2) gas components in the disks (R R 25) of a sample of 12 nearby spiral galaxies with moderate inclinations. Our analysis is based on sensitive high-resolution data from the THINGS (atomic gas) and HERACLES (molecular gas) surveys. To obtain reliable measurements of the velocity dispersion, we stack regions several kiloparsecs in size, after accounting for intrinsic velocity shifts due to galactic rotation and large-scale motions. We stack using various parameters: the galactocentric distance, star formation rate surface density, H I surface density, H2 surface density, and total gas surface density. We fit single Gaussian components to the stacked spectra and measure median velocity dispersions for H I of 11.9 ± 3.1 km s–1 and for CO of 12.0 ± 3.9 km s–1. The CO velocity dispersions are thus, surprisingly, very similar to the corresponding ones of H I, with an average ratio of σH I /σCO= 1.0 ± 0.2 irrespective of the stacking parameter. The measured CO velocity dispersions are significantly higher (factor of ~2) than the traditional picture of a cold molecular gas disk associated with star formation. The high dispersion implies an additional thick molecular gas disk (possibly as thick as the H I disk). Our finding is in agreement with recent sensitive measurements in individual edge-on and face-on galaxies and points toward the general existence of a thick disk of molecular gas, in addition to the well-known thin disk in nearby spiral galaxies.
dc.identifier.apacitationCaldú-Primo, A., Schruba, A., Walter, F., Leroy, A., Sandstrom, K., de Blok, W. J. G., ... Mogotsi, K. M. (2013). A high-dispersion molecular gas component in nearby galaxies. <i>The Astronomical Journal</i>, 146(6), 150 - 177. http://hdl.handle.net/11427/34954en_ZA
dc.identifier.chicagocitationCaldú-Primo, Anahi, Andreas Schruba, Fabian Walter, Adam Leroy, Karin Sandstrom, W J G de Blok, R Ianjamasimanana, and K M Mogotsi "A high-dispersion molecular gas component in nearby galaxies." <i>The Astronomical Journal</i> 146, 6. (2013): 150 - 177. http://hdl.handle.net/11427/34954en_ZA
dc.identifier.citationCaldú-Primo, A., Schruba, A., Walter, F., Leroy, A., Sandstrom, K., de Blok, W.J.G., Ianjamasimanana, R. & Mogotsi, K.M. et al. 2013. A high-dispersion molecular gas component in nearby galaxies. <i>The Astronomical Journal.</i> 146(6):150 - 177. http://hdl.handle.net/11427/34954en_ZA
dc.identifier.issn0004-6256
dc.identifier.issn1538-3881
dc.identifier.ris TY - Journal Article AU - Caldú-Primo, Anahi AU - Schruba, Andreas AU - Walter, Fabian AU - Leroy, Adam AU - Sandstrom, Karin AU - de Blok, W J G AU - Ianjamasimanana, R AU - Mogotsi, K M AB - We present a comprehensive study of the velocity dispersion of the atomic (H I) and molecular (H2) gas components in the disks (R R 25) of a sample of 12 nearby spiral galaxies with moderate inclinations. Our analysis is based on sensitive high-resolution data from the THINGS (atomic gas) and HERACLES (molecular gas) surveys. To obtain reliable measurements of the velocity dispersion, we stack regions several kiloparsecs in size, after accounting for intrinsic velocity shifts due to galactic rotation and large-scale motions. We stack using various parameters: the galactocentric distance, star formation rate surface density, H I surface density, H2 surface density, and total gas surface density. We fit single Gaussian components to the stacked spectra and measure median velocity dispersions for H I of 11.9 ± 3.1 km s–1 and for CO of 12.0 ± 3.9 km s–1. The CO velocity dispersions are thus, surprisingly, very similar to the corresponding ones of H I, with an average ratio of σH I /σCO= 1.0 ± 0.2 irrespective of the stacking parameter. The measured CO velocity dispersions are significantly higher (factor of ~2) than the traditional picture of a cold molecular gas disk associated with star formation. The high dispersion implies an additional thick molecular gas disk (possibly as thick as the H I disk). Our finding is in agreement with recent sensitive measurements in individual edge-on and face-on galaxies and points toward the general existence of a thick disk of molecular gas, in addition to the well-known thin disk in nearby spiral galaxies. DA - 2013 DB - OpenUCT DP - University of Cape Town IS - 6 J1 - The Astronomical Journal LK - https://open.uct.ac.za PY - 2013 SM - 0004-6256 SM - 1538-3881 T1 - A high-dispersion molecular gas component in nearby galaxies TI - A high-dispersion molecular gas component in nearby galaxies UR - http://hdl.handle.net/11427/34954 ER - en_ZA
dc.identifier.urihttp://hdl.handle.net/11427/34954
dc.identifier.vancouvercitationCaldú-Primo A, Schruba A, Walter F, Leroy A, Sandstrom K, de Blok WJG, et al. A high-dispersion molecular gas component in nearby galaxies. The Astronomical Journal. 2013;146(6):150 - 177. http://hdl.handle.net/11427/34954.en_ZA
dc.language.isoeng
dc.publisher.departmentDepartment of Astronomy
dc.publisher.facultyFaculty of Science
dc.sourceThe Astronomical Journal
dc.source.journalissue6
dc.source.journalvolume146
dc.source.pagination150 - 177
dc.source.urihttps://dx.doi.org/10.1088/0004-6256/146/6/150
dc.subject.otherastrophysics
dc.subject.othercosmology and astronomy
dc.subject.otheratoms
dc.subject.othercarbon monoxide
dc.subject.otherdensity
dc.subject.otherdispersions
dc.subject.otherdistance
dc.subject.othergalaxies
dc.subject.othergases
dc.subject.otherhydrogen
dc.subject.otherinclination
dc.subject.othermolecules
dc.subject.otherresolution
dc.subject.otherrotation
dc.subject.otherspectra
dc.subject.otherspiral configuration
dc.subject.otherstars
dc.subject.othersurfaces
dc.subject.othervelocity
dc.titleA high-dispersion molecular gas component in nearby galaxies
dc.typeJournal Article
uct.type.publicationResearch
uct.type.resourceJournal Article
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