Article: High-resolution mapping of the physical conditions in two nearby active galaxies based on 12CO(1-0), (2-1), and (3-2) lines

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TitleHigh-resolution mapping of the physical conditions in two nearby active galaxies based on 12CO(1-0), (2-1), and (3-2) lines
AuthorsBoone, F3 5
GarcíaBurillo, S
Combes, F5
Lim, J1
Ho, P1
Baker, AJ4
Matsushita, S1 7
Krips, M2
Dinh, VT1
Schinnerer, E6
Keywordsgalaxies: active
galaxies: individual: NGC 4569
galaxies: individual: NGC 4826
galaxies: ISM
Issue Date2010
PublisherE D P Sciences. The Journal's web site is located at http://www.aanda.org
CitationAstronomy And Astrophysics, 2010, v. 525 n. 1 [How to Cite?]
DOI: http://dx.doi.org/10.1051/0004-6361/200912723
AbstractWe present a detailed analysis of high resolution observations of the three lowest CO transitions in two nearby active galaxies, NGC 4569 and NGC 4826. The CO(1-0) and (2-1) lines were observed with the Plateau de Bure Interferometer and the CO(3-2) line with the Submillimeter Array. Combining these data allows us to compare the emission in the three lines and to map the line ratios, R 21 = I CO(2-1)/I CO(1-0) and R 32 = I CO(3-2)/I CO(1-0) at a resolution of ~2", i.e., a linear resolution of 160 pc for NGC 4569 and 40 pc for NGC 4826. In both galaxies the emission in the three lines is similarly distributed spatially and in velocity, and CO is less excited (R 32 < 0.6) than in the Galactic Center or the centers of other active galaxies studied so far. According to a pseudo-LTE model the molecular gas in NGC 4569 is cold and mainly optically thick in the CO(1-0) and (2-1) lines; less than 50% of the gas is optically thin in the CO(3-2) line. LVG modeling suggests the presence of an elongated ring of cold and dense gas coinciding with the inner Lindblad resonance (ILR) of the stellar bar in agreement with a previous analysis of the kinematics. More excited gas is resolved in the circumnuclear disk of NGC 4826. According to our pseudo-LTE model this corresponds to warmer gas with a ~20% of the CO(3-2) emission being optically thin. LVG modeling indicates the presence of a semicircular arc of dense and cold gas centered on the dynamical center and ~70 pc in radius. The gas temperature increases and its density decreases toward the center. A near side/far side asymmetry noticeable in the CO, R 32 and Paα maps suggests that opacity effects play a role. Examining published CO maps of nearby active galaxies we find similar asymmetries suggesting that this could be a common phenomenon in active galaxies. These mainly qualitative results open new perspectives for the study of active galaxies with the future Atacama Large Millimeter/submillimeter Array. © 2010 ESO.
ISSN0004-6361
2011 Impact Factor: 4.587
2011 SCImago Journal Rankings: 0.090
DOIhttp://dx.doi.org/10.1051/0004-6361/200912723
ISI Accession Number IDWOS:000285193700007
Funding AgencyGrant Number
ORCHID French-Taiwanese Hubert Curien Program
Funding Information:

We are much indebted to Christine Wilson and Frank Israel for very kindly providing us with their single dish CO(3-2) data. F. B. thanks the Max-Planck-Institut fur Radioastronomie in Bonn, where he was a postdoc at the time of the observations, for supporting the travel to the SMA. We thank the scientific and technical staffs at the SMA for their help at the observatory. The collaboration between LERMA and ASIAA was supported by the ORCHID French-Taiwanese Hubert Curien Program.

ReferencesReferences in Scopus
DC Field
Value
dc.contributor.authorBoone, F
dc.contributor.authorGarcíaBurillo, S
dc.contributor.authorCombes, F
dc.contributor.authorLim, J
dc.contributor.authorHo, P
dc.contributor.authorBaker, AJ
dc.contributor.authorMatsushita, S
dc.contributor.authorKrips, M
dc.contributor.authorDinh, VT
dc.contributor.authorSchinnerer, E
dc.date.accessioned2011-09-23T05:52:37Z
dc.date.available2011-09-23T05:52:37Z
dc.date.issued2010
dc.description.abstractWe present a detailed analysis of high resolution observations of the three lowest CO transitions in two nearby active galaxies, NGC 4569 and NGC 4826. The CO(1-0) and (2-1) lines were observed with the Plateau de Bure Interferometer and the CO(3-2) line with the Submillimeter Array. Combining these data allows us to compare the emission in the three lines and to map the line ratios, R 21 = I CO(2-1)/I CO(1-0) and R 32 = I CO(3-2)/I CO(1-0) at a resolution of ~2", i.e., a linear resolution of 160 pc for NGC 4569 and 40 pc for NGC 4826. In both galaxies the emission in the three lines is similarly distributed spatially and in velocity, and CO is less excited (R 32 < 0.6) than in the Galactic Center or the centers of other active galaxies studied so far. According to a pseudo-LTE model the molecular gas in NGC 4569 is cold and mainly optically thick in the CO(1-0) and (2-1) lines; less than 50% of the gas is optically thin in the CO(3-2) line. LVG modeling suggests the presence of an elongated ring of cold and dense gas coinciding with the inner Lindblad resonance (ILR) of the stellar bar in agreement with a previous analysis of the kinematics. More excited gas is resolved in the circumnuclear disk of NGC 4826. According to our pseudo-LTE model this corresponds to warmer gas with a ~20% of the CO(3-2) emission being optically thin. LVG modeling indicates the presence of a semicircular arc of dense and cold gas centered on the dynamical center and ~70 pc in radius. The gas temperature increases and its density decreases toward the center. A near side/far side asymmetry noticeable in the CO, R 32 and Paα maps suggests that opacity effects play a role. Examining published CO maps of nearby active galaxies we find similar asymmetries suggesting that this could be a common phenomenon in active galaxies. These mainly qualitative results open new perspectives for the study of active galaxies with the future Atacama Large Millimeter/submillimeter Array. © 2010 ESO.
dc.description.natureLink_to_subscribed_fulltext
dc.identifier.citationAstronomy And Astrophysics, 2010, v. 525 n. 1 [How to Cite?]
DOI: http://dx.doi.org/10.1051/0004-6361/200912723
dc.identifier.doihttp://dx.doi.org/10.1051/0004-6361/200912723
dc.identifier.hkuros193228
dc.identifier.isiWOS:000285193700007
Funding AgencyGrant Number
ORCHID French-Taiwanese Hubert Curien Program
Funding Information:

We are much indebted to Christine Wilson and Frank Israel for very kindly providing us with their single dish CO(3-2) data. F. B. thanks the Max-Planck-Institut fur Radioastronomie in Bonn, where he was a postdoc at the time of the observations, for supporting the travel to the SMA. We thank the scientific and technical staffs at the SMA for their help at the observatory. The collaboration between LERMA and ASIAA was supported by the ORCHID French-Taiwanese Hubert Curien Program.

dc.identifier.issn0004-6361
2011 Impact Factor: 4.587
2011 SCImago Journal Rankings: 0.090
dc.identifier.issue1
dc.identifier.openurl
dc.identifier.scopuseid_2-s2.0-78649600112
dc.identifier.urihttp://hdl.handle.net/10722/139609
dc.identifier.volume525
dc.languageeng
dc.publisherE D P Sciences. The Journal's web site is located at http://www.aanda.org
dc.publisher.placeFrance
dc.relation.ispartofAstronomy and Astrophysics
dc.relation.referencesReferences in Scopus
dc.rightsThe original publication is available at [http://www.aanda.org]
dc.subjectgalaxies: active
dc.subjectgalaxies: individual: NGC 4569
dc.subjectgalaxies: individual: NGC 4826
dc.subjectgalaxies: ISM
dc.titleHigh-resolution mapping of the physical conditions in two nearby active galaxies based on 12CO(1-0), (2-1), and (3-2) lines
dc.typeArticle
Author Affiliations
  1. Institute of Astrophysics and Astronomy, Academia Sinica Taiwan
  2. IRAM Institut de RadioAstronomie Millimétrique
  3. Université de Toulouse
  4. Rutgers, The State University of New Jersey
  5. Laboratoire d'Etude du Rayonnement et de la Matiere en Astrophysique
  6. Max-Planck-Institut für Astronomie
  7. Atacama Large Millimeter-submillimeter Array