Studies of ultracompact H II regions - II. High-resolution radio continuum and methanol maser survey Walsh, Andrew en_US Burton, Michael en_US Hyland, A en_US Robinson, Garry en_US 2021-11-25T13:06:37Z 2021-11-25T13:06:37Z 1998 en_US
dc.description.abstract High spatial resolution radio continuum and 6.67-GHz methanol spectral line data are presented for methanol masers previously detected by Walsh et al. (1997). Methanol maser and/or radio continuum emission is found in 364 cases towards IRAS-selected regions. For those sources with methanol maser emission, relative positions have been obtained to an accuracy of typically 0.05 arcsec, with absolute positions accurate to around 1 arcsec. Maps of selected sources are provided. The intensity of the maser emission does not seem to depend on the presence of a continuum source. The coincidence of water and methanol maser positions in some regions suggests there is overlap in the requirements for methanol and water maser emission to be observable. However, there is a striking difference between the general proximity of methanol and water masers to both cometary and irregularly shaped ultracompact (UC) H ii regions, indicating that, in other cases, there must be differing environments conducive to stimulating their emission. We show that the methanol maser is most likely present before an observable UC H ii region is formed around a massive star and is quickly destroyed as the UC H ii region evolves. There are 36 out of 97 maser sites that are linearly extended. The hypothesis that the maser emission is found in a circumstellar disc is not inconsistent with these 36 maser sites, but is unlikely. It cannot, however, account for all other maser sites. An alternative model which uses shocks to create the masing spots can more readily reproduce the maser spot distributions. en_US
dc.identifier.issn 0035-8711 en_US
dc.language English
dc.language.iso EN en_US
dc.rights CC BY-NC-ND 3.0 en_US
dc.rights.uri en_US
dc.source Legacy MARC en_US
dc.title Studies of ultracompact H II regions - II. High-resolution radio continuum and methanol maser survey en_US
dc.type Journal Article en
dcterms.accessRights metadata only access
dspace.entity.type Publication en_US
unsw.identifier.doiPublisher en_US
unsw.relation.faculty Science
unsw.relation.faculty UNSW Canberra
unsw.relation.ispartofissue 3 en_US
unsw.relation.ispartofjournal Monthly notices of the Royal Astronomical Society en_US
unsw.relation.ispartofpagefrompageto 640-698 en_US
unsw.relation.ispartofvolume 301 en_US
unsw.relation.originalPublicationAffiliation Walsh, Andrew en_US
unsw.relation.originalPublicationAffiliation Burton, Michael, Physics, Faculty of Science, UNSW en_US
unsw.relation.originalPublicationAffiliation Hyland, A en_US
unsw.relation.originalPublicationAffiliation Robinson, Garry, Physical, Environmental & Mathematical Sciences, Australian Defence Force Academy, UNSW en_US School of Physics * School of Science *
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