J/AJ/129/393ivo://CDS.VizieR/J/AJ/129/393doi:10.26093/cds/vizier.51290393CDSOey M.S.Watson A.M.Kern K.Walth G.L.2005-09-24T21:34:47Z2005-09-24T21:34:32ZCDS support team

CDS, Observatoire de Strasbourg, 11 rue de l'Universite, F-67000 Strasbourg, France

cds-question@unistra.frinterstellar-mediumvisible-astronomybroad-band-photometryIt is generally believed that expanding superbubbles and mechanical feedback from massive stars trigger star formation, because there are numerous examples of superbubbles showing secondary star formation at their edges. However, although these systems show an age sequence, they do not provide strong evidence of a causal relationship. The W3/W4 Galactic star-forming complex suggests a three-generation hierarchy: the supergiant shell structures correspond to the oldest generation; these triggered the formation of IC 1795 in W3, the progenitor of a molecular superbubble that in turn triggered the current star-forming episodes in the embedded regions W3-North, W3-Main, and W3-OH. We present UBV photometry and spectroscopic classifications for IC 1795, which show an age of 3-5 Myr. This age is intermediate between the reported 6-20 Myr age of the supergiant shell system and the extremely young ages (10^4^-10^5^yr) for the embedded knots of the ultracompact HII regions, W3-North, W3-Main, and W3-OH. Thus, an age sequence is indeed confirmed for the entire W3/W4 hierarchical system. This therefore provides some of the first convincing evidence that superbubble action and mechanical feedback are indeed a triggering mechanism for star formation.2005AJ....129..393Ohttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/AJ/129/393CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicehttps://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/AJ/129/393https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/AJ/129/393http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/AJ/129/393https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/AJ/129/393https://vizier.iucaa.in/viz-bin/votable?-source=J/AJ/129/393http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/AJ/129/393GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/AJ/129/393/table2 (Photometry and spectral types for the W3 region)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/AJ/129/393/table2?https://vizier.iucaa.in/viz-bin/conesearch/J/AJ/129/393/table2?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/AJ/129/393/table2?GETtext/xml+votable180.050000true36.67212561.99005560.0055555555555555566/3649https://cdsarc.cds.unistra.fr/viz-bin/moc/J/AJ/129/393?format=asciiOpticaldefaultJ/AJ/129/393/table2Photometry and spectral types for the W3 regionrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordint[OWK2005]Identification number from this workintf_[OWK2005]Flag on [OWK2005] (1)charOI? Ogura & Ishida (1976PASJ...28..651O) identification numberintnullableRAJ2000Hour of Right Ascension (J2000)pos.eq.ra;meta.mainDEJ2000Degree of Declination (J2000)pos.eq.dec;meta.mainVmagThe V band magnitudemagfloate_VmagFormal uncertainty in VmagmagfloatBmagThe B band magnitudemagfloate_BmagFormal uncertainty in BmagmagfloatUmagThe U band magnitudemagfloate_UmagFormal uncertainty in UmagmagfloatNobsNumber of measurements averagedintSpTypeSpectroscopic classificationcharn_SpType[*] *: from Mathys, 1989A&AS...81..237Mchar