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

TitleHigh-resolution mapping of the physical conditions in two nearby active galaxies based on 12CO(1-0), (2-1), and (3-2) lines
Authors
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
Citation
Astronomy And Astrophysics, 2010, v. 525 n. 1 How to Cite?
Abstract
We 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.
Persistent Identifierhttp://hdl.handle.net/10722/139609
ISSN
2013 Impact Factor: 4.479
ISI Accession Number ID
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.

References

 

Author Affiliations
  1. IRAM Institut de RadioAstronomie Millimétrique
  2. Université de Toulouse
  3. Rutgers, The State University of New Jersey
  4. Institute of Astrophysics and Astronomy, Academia Sinica Taiwan
  5. Laboratoire d'Etude du Rayonnement et de la Matiere en Astrophysique
  6. Max-Planck-Institut für Astronomie
  7. Atacama Large Millimeter-submillimeter Array
DC FieldValueLanguage
dc.contributor.authorBoone, Fen_HK
dc.contributor.authorGarcíaBurillo, Sen_HK
dc.contributor.authorCombes, Fen_HK
dc.contributor.authorLim, Jen_HK
dc.contributor.authorHo, Pen_HK
dc.contributor.authorBaker, AJen_HK
dc.contributor.authorMatsushita, Sen_HK
dc.contributor.authorKrips, Men_HK
dc.contributor.authorDinh, VTen_HK
dc.contributor.authorSchinnerer, Een_HK
dc.date.accessioned2011-09-23T05:52:37Z-
dc.date.available2011-09-23T05:52:37Z-
dc.date.issued2010en_HK
dc.identifier.citationAstronomy And Astrophysics, 2010, v. 525 n. 1en_HK
dc.identifier.issn0004-6361en_HK
dc.identifier.urihttp://hdl.handle.net/10722/139609-
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.en_HK
dc.languageengen_US
dc.publisherE D P Sciences. The Journal's web site is located at http://www.aanda.orgen_HK
dc.relation.ispartofAstronomy and Astrophysicsen_HK
dc.rightsThe original publication is available at [http://www.aanda.org]-
dc.subjectgalaxies: activeen_HK
dc.subjectgalaxies: individual: NGC 4569en_HK
dc.subjectgalaxies: individual: NGC 4826en_HK
dc.subjectgalaxies: ISMen_HK
dc.titleHigh-resolution mapping of the physical conditions in two nearby active galaxies based on 12CO(1-0), (2-1), and (3-2) linesen_HK
dc.typeArticleen_HK
dc.identifier.openurlhttp://library.hku.hk:4550/resserv?sid=HKU:IR&issn=0004-6361&volume=525&issue=1, article no. 18&spage=&epage=&date=2011&atitle=High-resolution+mapping+of+the+physical+conditions+in+two+nearby+active+galaxies+based+on+12CO(1-0),+(2-1),+and+(3-2)+lines-
dc.identifier.emailLim, J: jjlim@hku.hken_HK
dc.identifier.authorityLim, J=rp00745en_HK
dc.description.naturelink_to_subscribed_fulltext-
dc.identifier.doi10.1051/0004-6361/200912723en_HK
dc.identifier.scopuseid_2-s2.0-78649600112en_HK
dc.identifier.hkuros193228en_US
dc.relation.referenceshttp://www.scopus.com/mlt/select.url?eid=2-s2.0-78649600112&selection=ref&src=s&origin=recordpageen_HK
dc.identifier.volume525en_HK
dc.identifier.issue1en_HK
dc.identifier.isiWOS:000285193700007-
dc.publisher.placeFranceen_HK
dc.identifier.scopusauthoridBoone, F=8902646900en_HK
dc.identifier.scopusauthoridGarcíaBurillo, S=6602484331en_HK
dc.identifier.scopusauthoridCombes, F=7004959652en_HK
dc.identifier.scopusauthoridLim, J=7403453870en_HK
dc.identifier.scopusauthoridHo, P=7402211489en_HK
dc.identifier.scopusauthoridBaker, AJ=35555614200en_HK
dc.identifier.scopusauthoridMatsushita, S=7201408992en_HK
dc.identifier.scopusauthoridKrips, M=14622777400en_HK
dc.identifier.scopusauthoridDinh, VT=36677146600en_HK
dc.identifier.scopusauthoridSchinnerer, E=6603777391en_HK

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