H i kinematics, mass distribution and star formation threshold in NGC 6822, using the SKA pathfinder KAT-7

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dc.contributor.authorNamumba, B
dc.contributor.authorCarignan, C
dc.contributor.authorPassmoor, S
dc.contributor.authorde Blok, W J G
dc.date.accessioned2021-10-08T07:08:24Z
dc.date.available2021-10-08T07:08:24Z
dc.date.issued2017
dc.description.abstractWe present high sensitivity H I observations of NGC 6822, obtained with the Karoo Array Telescope (KAT-7). We study the kinematics, the mass distribution and the star formation thresholds. The KAT-7 short baselines and low system temperature make it sensitive to large-scale, low surface brightness emission. The observations detected ∼ 23 per cent more flux than previous Australian Telescope Compact Array observations. We fit a tilted ring model to the H I velocity field to derive the rotation curve (RC). The KAT-7 observations allow the measurement of the rotation curve of NGC 6822 out to 5.8 kpc, ∼1 kpc further than existing measurements. NGC 6822 is seen to be dark matter dominated at all radii. The observationally motivated pseudo-isothermal dark matter (DM) halo model reproduces well the observed RC while the Navarro Frank-White DM model gives a poor fit to the data. We find the best-fitting mass-to-light ratio (M/L) of 0.12 ± 0.01 which is consistent with the literature. The modified Newtonian dynamics gives a poor fit to our data. We derive the star formation threshold in NGC 6822 using the H I and H α data. The critical gas densities were calculated for gravitational instabilities using the Toomre-Q criterion and the cloud-growth criterion. We found that in regions of star formation, the cloud-growth criterion explains star formation better than the Toomre-Q criterion. This shows that the local shear rate could be a key player in cloud formation for irregular galaxies such as NGC 6822.
dc.identifier.apacitationNamumba, B., Carignan, C., Passmoor, S., & de Blok, W. J. G. (2017). H i kinematics, mass distribution and star formation threshold in NGC 6822, using the SKA pathfinder KAT-7. <i>Monthly Notices of the Royal Astronomical Society</i>, 472(3), 3761 - 3773. http://hdl.handle.net/11427/34575en_ZA
dc.identifier.chicagocitationNamumba, B, C Carignan, S Passmoor, and W J G de Blok "H i kinematics, mass distribution and star formation threshold in NGC 6822, using the SKA pathfinder KAT-7." <i>Monthly Notices of the Royal Astronomical Society</i> 472, 3. (2017): 3761 - 3773. http://hdl.handle.net/11427/34575en_ZA
dc.identifier.citationNamumba, B., Carignan, C., Passmoor, S. & de Blok, W.J.G. 2017. H i kinematics, mass distribution and star formation threshold in NGC 6822, using the SKA pathfinder KAT-7. <i>Monthly Notices of the Royal Astronomical Society.</i> 472(3):3761 - 3773. http://hdl.handle.net/11427/34575en_ZA
dc.identifier.issn0035-8711
dc.identifier.issn1365-2966
dc.identifier.ris TY - Journal Article AU - Namumba, B AU - Carignan, C AU - Passmoor, S AU - de Blok, W J G AB - We present high sensitivity H I observations of NGC 6822, obtained with the Karoo Array Telescope (KAT-7). We study the kinematics, the mass distribution and the star formation thresholds. The KAT-7 short baselines and low system temperature make it sensitive to large-scale, low surface brightness emission. The observations detected ∼ 23 per cent more flux than previous Australian Telescope Compact Array observations. We fit a tilted ring model to the H I velocity field to derive the rotation curve (RC). The KAT-7 observations allow the measurement of the rotation curve of NGC 6822 out to 5.8 kpc, ∼1 kpc further than existing measurements. NGC 6822 is seen to be dark matter dominated at all radii. The observationally motivated pseudo-isothermal dark matter (DM) halo model reproduces well the observed RC while the Navarro Frank-White DM model gives a poor fit to the data. We find the best-fitting mass-to-light ratio (M/L) of 0.12 ± 0.01 which is consistent with the literature. The modified Newtonian dynamics gives a poor fit to our data. We derive the star formation threshold in NGC 6822 using the H I and H α data. The critical gas densities were calculated for gravitational instabilities using the Toomre-Q criterion and the cloud-growth criterion. We found that in regions of star formation, the cloud-growth criterion explains star formation better than the Toomre-Q criterion. This shows that the local shear rate could be a key player in cloud formation for irregular galaxies such as NGC 6822. DA - 2017 DB - OpenUCT DP - University of Cape Town IS - 3 J1 - Monthly Notices of the Royal Astronomical Society LK - https://open.uct.ac.za PY - 2017 SM - 0035-8711 SM - 1365-2966 T1 - H i kinematics, mass distribution and star formation threshold in NGC 6822, using the SKA pathfinder KAT-7 TI - H i kinematics, mass distribution and star formation threshold in NGC 6822, using the SKA pathfinder KAT-7 UR - http://hdl.handle.net/11427/34575 ER - en_ZA
dc.identifier.urihttp://hdl.handle.net/11427/34575
dc.identifier.vancouvercitationNamumba B, Carignan C, Passmoor S, de Blok WJG. H i kinematics, mass distribution and star formation threshold in NGC 6822, using the SKA pathfinder KAT-7. Monthly Notices of the Royal Astronomical Society. 2017;472(3):3761 - 3773. http://hdl.handle.net/11427/34575.en_ZA
dc.language.isoeng
dc.publisher.departmentDepartment of Astronomy
dc.publisher.facultyFaculty of Science
dc.sourceMonthly Notices of the Royal Astronomical Society
dc.source.journalissue3
dc.source.journalvolume472
dc.source.pagination3761 - 3773
dc.source.urihttps://dx.doi.org/10.1093/mnras/stx2256
dc.subject.otherObservations
dc.subject.otherExample
dc.subject.othermodel
dc.subject.otherKinematics
dc.subject.othermesse
dc.subject.otherMass
dc.subject.otherdistribution
dc.subject.otherTelescopes
dc.subject.otherténèbres
dc.subject.otherMatter
dc.subject.othermatière
dc.subject.otherPoor
dc.subject.otherTemperature
dc.subject.othertemperature
dc.subject.otheremission
dc.subject.otherCent
dc.subject.otheranneau
dc.subject.otherSpeed
dc.subject.otherfield
dc.subject.otherMeasurement
dc.subject.otherwell
dc.subject.otherpuits
dc.subject.otherlittérature
dc.subject.otherLiterature
dc.subject.otherliterature
dc.subject.otherDynamics
dc.subject.othergas
dc.subject.otherGas
dc.subject.otherRegions
dc.subject.otherrate
dc.subject.otherclé
dc.subject.othercloud
dc.subject.otherGalaxies
dc.subject.othergalaxies: haloes
dc.subject.othergalaxies: ISM
dc.subject.otherLocal Group
dc.subject.othergalaxies: star formation
dc.titleH i kinematics, mass distribution and star formation threshold in NGC 6822, using the SKA pathfinder KAT-7
dc.typeJournal Article
uct.type.publicationResearch
uct.type.resourceJournal Article
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