Is GBT 1355+5439 a dark galaxy?

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dc.contributor.authorOosterloo, T A
dc.contributor.authorHeald, G H
dc.contributor.authorde Blok, W J G
dc.date.accessioned2021-10-08T11:01:09Z
dc.date.available2021-10-08T11:01:09Z
dc.date.issued2013
dc.description.abstractWe present H i imaging of GBT 1355+5439 performed with the Westerbork Synthesis Radio Telescope. This is a dark H i object recently discovered close to the nearby galaxy M101. We find GBT 1355+5439 to be an H i cloud 5 × 3 arcmin in size. The total H i image and the kinematics show that the cloud consists of condensations that have small (~10 km s-1) motions with respect to each other. The column densities of the H i are low; the observed peak value is 7.1 × 1019 cm-2. The velocity field shows a mild velocity gradient over the body of GBT 1355+5439, possibly due to rotation, but it may also indicate large-scale radial motions. Although our data are limited in sensitivity, at all positions the H i velocity dispersion is higher than 5 km s-1 and no narrow, cold, H i component is seen. Because its distance is not known, we considered various possibilities for the nature of GBT 1355+5439. Both the scenarios that it is a tidal remnant near M101 and that it is a dark dwarf companion of M101 meet difficulties. Neither do the data fit the properties of known compact high-velocity clouds in the Galactic halo exactly, but we cannot entirely exclude this option and deeper observations are required. We also considered the possibility that GBT 1355+5439 is a gas-rich dark minihalo in the outer regions of the Local Group. Interestingly, it would then have similar properties as the clouds of a proposed Local Group population recently found in the ALFALFA survey. In this case, the H i mass of GBT 1355+5439 would be about a few times 105M⊙, its size about 1 kpc, and the dynamical mass Mdyn > 5 × 107M⊙. However, if GBT 1355+5439 is a dark Local Group object, the internal kinematics of the H i appears to be different from that of gas-dominated, almost dark galaxies of similar size.
dc.identifier.apacitationOosterloo, T. A., Heald, G. H., & de Blok, W. J. G. (2013). Is GBT 1355+5439 a dark galaxy?. <i>Astronomy and Astrophysics</i>, 555(4), L7 - 177. http://hdl.handle.net/11427/35097en_ZA
dc.identifier.chicagocitationOosterloo, T A, G H Heald, and W J G de Blok "Is GBT 1355+5439 a dark galaxy?." <i>Astronomy and Astrophysics</i> 555, 4. (2013): L7 - 177. http://hdl.handle.net/11427/35097en_ZA
dc.identifier.citationOosterloo, T.A., Heald, G.H. & de Blok, W.J.G. 2013. Is GBT 1355+5439 a dark galaxy?. <i>Astronomy and Astrophysics.</i> 555(4):L7 - 177. http://hdl.handle.net/11427/35097en_ZA
dc.identifier.issn0004-6361
dc.identifier.issn1432-0746
dc.identifier.ris TY - Journal Article AU - Oosterloo, T A AU - Heald, G H AU - de Blok, W J G AB - We present H i imaging of GBT 1355+5439 performed with the Westerbork Synthesis Radio Telescope. This is a dark H i object recently discovered close to the nearby galaxy M101. We find GBT 1355+5439 to be an H i cloud 5 × 3 arcmin in size. The total H i image and the kinematics show that the cloud consists of condensations that have small (~10 km s-1) motions with respect to each other. The column densities of the H i are low; the observed peak value is 7.1 × 1019 cm-2. The velocity field shows a mild velocity gradient over the body of GBT 1355+5439, possibly due to rotation, but it may also indicate large-scale radial motions. Although our data are limited in sensitivity, at all positions the H i velocity dispersion is higher than 5 km s-1 and no narrow, cold, H i component is seen. Because its distance is not known, we considered various possibilities for the nature of GBT 1355+5439. Both the scenarios that it is a tidal remnant near M101 and that it is a dark dwarf companion of M101 meet difficulties. Neither do the data fit the properties of known compact high-velocity clouds in the Galactic halo exactly, but we cannot entirely exclude this option and deeper observations are required. We also considered the possibility that GBT 1355+5439 is a gas-rich dark minihalo in the outer regions of the Local Group. Interestingly, it would then have similar properties as the clouds of a proposed Local Group population recently found in the ALFALFA survey. In this case, the H i mass of GBT 1355+5439 would be about a few times 105M⊙, its size about 1 kpc, and the dynamical mass Mdyn > 5 × 107M⊙. However, if GBT 1355+5439 is a dark Local Group object, the internal kinematics of the H i appears to be different from that of gas-dominated, almost dark galaxies of similar size. DA - 2013 DB - OpenUCT DP - University of Cape Town IS - 4 J1 - Astronomy and Astrophysics LK - https://open.uct.ac.za PY - 2013 SM - 0004-6361 SM - 1432-0746 T1 - Is GBT 1355+5439 a dark galaxy? TI - Is GBT 1355+5439 a dark galaxy? UR - http://hdl.handle.net/11427/35097 ER - en_ZA
dc.identifier.urihttp://hdl.handle.net/11427/35097
dc.identifier.vancouvercitationOosterloo TA, Heald GH, de Blok WJG. Is GBT 1355+5439 a dark galaxy?. Astronomy and Astrophysics. 2013;555(4):L7 - 177. http://hdl.handle.net/11427/35097.en_ZA
dc.language.isoeng
dc.publisher.departmentDepartment of Astronomy
dc.publisher.facultyFaculty of Science
dc.sourceAstronomy and Astrophysics
dc.source.journalissue4
dc.source.journalvolume555
dc.source.paginationL7 - 177
dc.source.urihttps://dx.doi.org/10.1051/0004-6361/201321965
dc.subject.otherEconomies et finances
dc.subject.otherÉconomie
dc.subject.otherténèbres
dc.subject.otherobjet
dc.subject.otherGestion des connaissances
dc.subject.othernain
dc.subject.othermesse
dc.subject.otherimage
dc.subject.othercolonne
dc.subject.othervaleur
dc.subject.othercorps
dc.subject.othernature
dc.subject.otherpopulation
dc.subject.otherprospection
dc.subject.othergalaxies: dwarf
dc.subject.otherradio lines: galaxies
dc.subject.otherHIGH-VELOCITY CLOUDS
dc.subject.otherLOCAL GROUP
dc.subject.otherSTAR-FORMATION
dc.subject.otherLEO T
dc.subject.otherCOMPACT
dc.subject.otherGAS
dc.subject.otherHI
dc.subject.otherSATELLITES
dc.subject.otherMINIHALOS
dc.subject.otherCATALOG
dc.titleIs GBT 1355+5439 a dark galaxy?
dc.typeJournal Article
uct.type.publicationResearch
uct.type.resourceJournal Article
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