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Article: TANGO I: Interstellar medium in nearby radio galaxies

TitleTANGO I: Interstellar medium in nearby radio galaxies
Authors
KeywordsGalaxies: luminosity function, mass function
Galaxy: evolution
Radio continuum: galaxies
Issue Date2010
PublisherE D P Sciences. The Journal's web site is located at http://www.aanda.org
Citation
Astronomy And Astrophysics, 2010, v. 518 n. 11 How to Cite?
AbstractContext. Powerful radio-AGN are hosted by massive elliptical galaxies that are usually very poor in molecular gas. Nevertheless, gas is needed at their very center to feed the nuclear activity. Aims. We study the molecular gas properties (i.e., mass, kinematics, distribution, origin) of these objects, and compare them with results for other known samples. Methods. At the IRAM-30m telescope, we performed a survey of the CO(1-0) and CO(2-1) emission from the most powerful radio galaxies of the Local Universe, selected only on the basis of their radio continuum fluxes. Results. The main result of our survey is that the molecular gas content of these galaxies is very low compared to spiral or FIR-selected galaxies. The median value of the molecular gas mass, including detections and upper limits, is 2.2 × 108 M⊙. When separated into FR-I and FR-II types, a difference in their H2 masses is found. The median value of FR-I galaxies is about 1.9 × 108 M⊙. and higher for FR-II galaxies, at about 4.5 × 108 M⊙. Which is probably entirely because of a Malmquist bias. Our results contrast with those of previous surveys, whose targets were mainly selected by means of their FIR emission, implying that we measure higher observed masses of molecular gas. Moreover, the shape of CO spectra suggest that a central molecular gas disk exists in 30% of these radio galaxies, a lower rate than in other active galaxy samples. Conclusions. We find a low level of molecular gas in our sample of radio-selected AGNs, indicating that galaxies do not need much molecular gas to host an AGN. The presence of a molecular gas disk in some galaxies and the wide range of molecular gas masses may be indicative of different origins for the gas, which we can not exclude at present (e.g., minor/major mergers, stellar mass loss, or accretion). 2010 © ESO.
Persistent Identifierhttp://hdl.handle.net/10722/139608
ISSN
2014 Impact Factor: 4.378
2015 SCImago Journal Rankings: 2.446
ISI Accession Number ID
Funding AgencyGrant Number
DGI, SpainAYA2008-06181-C02-02
Funding Information:

We thank Eric Emsellem for a careful refereeing and a detailed report, which helped to improve this paper significantly. B. Ocana Flaquer and S. Leon are partially supported by DGI Grant AYA2008-06181-C02-02, Spain. We thank Pamela Ocana for her careful readings and inputs on the manuscript.

References

 

DC FieldValueLanguage
dc.contributor.authorOcaña Flaquer, Ben_HK
dc.contributor.authorLeon, Sen_HK
dc.contributor.authorCombes, Fen_HK
dc.contributor.authorLim, Jen_HK
dc.date.accessioned2011-09-23T05:52:36Z-
dc.date.available2011-09-23T05:52:36Z-
dc.date.issued2010en_HK
dc.identifier.citationAstronomy And Astrophysics, 2010, v. 518 n. 11en_HK
dc.identifier.issn0004-6361en_HK
dc.identifier.urihttp://hdl.handle.net/10722/139608-
dc.description.abstractContext. Powerful radio-AGN are hosted by massive elliptical galaxies that are usually very poor in molecular gas. Nevertheless, gas is needed at their very center to feed the nuclear activity. Aims. We study the molecular gas properties (i.e., mass, kinematics, distribution, origin) of these objects, and compare them with results for other known samples. Methods. At the IRAM-30m telescope, we performed a survey of the CO(1-0) and CO(2-1) emission from the most powerful radio galaxies of the Local Universe, selected only on the basis of their radio continuum fluxes. Results. The main result of our survey is that the molecular gas content of these galaxies is very low compared to spiral or FIR-selected galaxies. The median value of the molecular gas mass, including detections and upper limits, is 2.2 × 108 M⊙. When separated into FR-I and FR-II types, a difference in their H2 masses is found. The median value of FR-I galaxies is about 1.9 × 108 M⊙. and higher for FR-II galaxies, at about 4.5 × 108 M⊙. Which is probably entirely because of a Malmquist bias. Our results contrast with those of previous surveys, whose targets were mainly selected by means of their FIR emission, implying that we measure higher observed masses of molecular gas. Moreover, the shape of CO spectra suggest that a central molecular gas disk exists in 30% of these radio galaxies, a lower rate than in other active galaxy samples. Conclusions. We find a low level of molecular gas in our sample of radio-selected AGNs, indicating that galaxies do not need much molecular gas to host an AGN. The presence of a molecular gas disk in some galaxies and the wide range of molecular gas masses may be indicative of different origins for the gas, which we can not exclude at present (e.g., minor/major mergers, stellar mass loss, or accretion). 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.subjectGalaxies: luminosity function, mass functionen_HK
dc.subjectGalaxy: evolutionen_HK
dc.subjectRadio continuum: galaxiesen_HK
dc.titleTANGO I: Interstellar medium in nearby radio galaxiesen_HK
dc.typeArticleen_HK
dc.identifier.openurlhttp://library.hku.hk:4550/resserv?sid=HKU:IR&issn=0004-6361&volume=518, article no. A9&spage=&epage=&date=2010&atitle=TANGO+I:+Interstellar+medium+in+nearby+radio+galaxies+-+Molecular+gas-
dc.identifier.emailLim, J: jjlim@hku.hken_HK
dc.identifier.authorityLim, J=rp00745en_HK
dc.description.naturelink_to_subscribed_fulltext-
dc.identifier.doi10.1051/0004-6361/200913392en_HK
dc.identifier.hkuros193226en_US
dc.relation.referenceshttp://www.scopus.com/mlt/select.url?eid=2-s2.0-77955862075&selection=ref&src=s&origin=recordpageen_HK
dc.identifier.volume518en_HK
dc.identifier.issue11en_HK
dc.identifier.isiWOS:000285342500009-
dc.publisher.placeFranceen_HK
dc.identifier.scopusauthoridOcaña Flaquer, B=25723736000en_HK
dc.identifier.scopusauthoridLeon, S=7006526119en_HK
dc.identifier.scopusauthoridCombes, F=7004959652en_HK
dc.identifier.scopusauthoridLim, J=7403453870en_HK

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