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Article: The Role of Electron Excitation and Nature of Molecular Gas in Cluster Central Elliptical Galaxies

TitleThe Role of Electron Excitation and Nature of Molecular Gas in Cluster Central Elliptical Galaxies
Authors
Keywordsactive - galaxies
galaxies
individual (NGC 1275) - galaxies
ISM - galaxies
molecules
Issue Date2017
PublisherAmerican Astronomical Society, co-published with Institute of Physics Publishing, Inc. The Journal's web site is located at http://iopscience.iop.org/0004-637X/
Citation
The Astrophysical Journal, 2017, v. 850 n. 1, p. 31:1-24 How to Cite?
AbstractWe present observations in CO (3-2) that, combined with previous observations in CO (2-1), constrain the physical properties of the filamentary molecular gas in the central 6.5 kpc of NGC 1275, the central giant elliptical galaxy of the Perseus Cluster. We find this molecular gas to have a temperature ≥20 K and a density 102-104cm-3, typically warmer and denser than the bulk of Giant Molecular Clouds (GMCs) in the Galaxy. Bathed in the harsh radiation and particle field of the surrounding intracluster X-ray gas, the molecular gas likely has a much higher ionization fraction than that of GMCs. For an ionization fraction of 10-4,similar to that of Galactic diffuse (≤250cm-3) partially molecular clouds that emit in HCN (1-0) and HCO+ (1-0), we show that the same gas traced in CO can produce the previously reported emissions in HCN (3-2), HCO+ (3-2), and CN (2-1) from NGC 1275; the dominant source of excitation for all the latter molecules is collisions with electrons. For the molecular filaments to not collapse, as evidenced by their lack of star formation, they must consist of thin strands that have cross-sectional radii ≤0.2-2 pc if supported solely by thermal gas pressure; larger radii are permissible if turbulence or poloidal magnetic fields provide additional pressure support. We point out that the conditions required to relate CO luminosities to molecular gas masses in our Galaxy are unlikely to apply in cluster central elliptical galaxies. Rather than being virialized structures analogous to GMCs, we propose that the molecular gas in NGC 1275 comprises pressure-confined structures created by turbulent flows.
Persistent Identifierhttp://hdl.handle.net/10722/250035
ISSN
2015 Impact Factor: 5.909
2015 SCImago Journal Rankings: 3.266

 

DC FieldValueLanguage
dc.contributor.authorLim, JJL-
dc.contributor.authorTrung, DV-
dc.contributor.authorVrtilek, J-
dc.contributor.authorDavid, LP-
dc.contributor.authorForman, W-
dc.date.accessioned2017-12-20T09:19:44Z-
dc.date.available2017-12-20T09:19:44Z-
dc.date.issued2017-
dc.identifier.citationThe Astrophysical Journal, 2017, v. 850 n. 1, p. 31:1-24-
dc.identifier.issn0004-637X-
dc.identifier.urihttp://hdl.handle.net/10722/250035-
dc.description.abstractWe present observations in CO (3-2) that, combined with previous observations in CO (2-1), constrain the physical properties of the filamentary molecular gas in the central 6.5 kpc of NGC 1275, the central giant elliptical galaxy of the Perseus Cluster. We find this molecular gas to have a temperature ≥20 K and a density 102-104cm-3, typically warmer and denser than the bulk of Giant Molecular Clouds (GMCs) in the Galaxy. Bathed in the harsh radiation and particle field of the surrounding intracluster X-ray gas, the molecular gas likely has a much higher ionization fraction than that of GMCs. For an ionization fraction of 10-4,similar to that of Galactic diffuse (≤250cm-3) partially molecular clouds that emit in HCN (1-0) and HCO+ (1-0), we show that the same gas traced in CO can produce the previously reported emissions in HCN (3-2), HCO+ (3-2), and CN (2-1) from NGC 1275; the dominant source of excitation for all the latter molecules is collisions with electrons. For the molecular filaments to not collapse, as evidenced by their lack of star formation, they must consist of thin strands that have cross-sectional radii ≤0.2-2 pc if supported solely by thermal gas pressure; larger radii are permissible if turbulence or poloidal magnetic fields provide additional pressure support. We point out that the conditions required to relate CO luminosities to molecular gas masses in our Galaxy are unlikely to apply in cluster central elliptical galaxies. Rather than being virialized structures analogous to GMCs, we propose that the molecular gas in NGC 1275 comprises pressure-confined structures created by turbulent flows.-
dc.languageeng-
dc.publisherAmerican Astronomical Society, co-published with Institute of Physics Publishing, Inc. The Journal's web site is located at http://iopscience.iop.org/0004-637X/-
dc.relation.ispartofThe Astrophysical Journal-
dc.rightsThe Astrophysical Journal. Copyright © American Astronomical Society, co-published with Institute of Physics Publishing, Inc.-
dc.rightsThis work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.-
dc.subjectactive - galaxies-
dc.subjectgalaxies-
dc.subjectindividual (NGC 1275) - galaxies-
dc.subjectISM - galaxies-
dc.subjectmolecules-
dc.titleThe Role of Electron Excitation and Nature of Molecular Gas in Cluster Central Elliptical Galaxies-
dc.typeArticle-
dc.identifier.emailLim, JJL: jjlim@hku.hk-
dc.identifier.authorityLim, JJL=rp00745-
dc.description.naturepublished_or_final_version-
dc.identifier.doi10.3847/1538-4357/aa9275-
dc.identifier.scopuseid_2-s2.0-85037679620-
dc.identifier.hkuros283801-
dc.identifier.volume850-
dc.identifier.issue1-
dc.identifier.spage31:1-
dc.identifier.epage24-
dc.publisher.placeUnited States-

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