J/AJ/144/182ivo://CDS.VizieR/J/AJ/144/182doi:10.26093/cds/vizier.51440182CDSPellerin A.Meyer M.M.Calzetti D.Harris J.2017-07-04T07:09:29Z2014-02-10T06:58:13ZCDS support team

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

cds-question@unistra.frstellar-associationsstellar-agesDissolving stellar groups are very difficult to detect using traditional surface photometry techniques. We have developed a method to find and characterize non-compact stellar systems in galaxies where the young stellar population can be spatially resolved. By carrying out photometry on individual stars, we are able to separate the luminous blue stellar population from the star field background. The locations of these stars are used to identify groups by applying the HOP algorithm, which are then characterized using color-magnitude and stellar density radial profiles to estimate age, size, density, and shape. We test the method on Hubble Space Telescope Advanced Camera for Surveys archival images of IC 2574 and find 75 dispersed stellar groups. Of these, 20 highly dispersed groups are good candidates for dissolving systems. We find few compact systems with evidence of dissolution, potentially indicating that star formation in this galaxy occurs mostly in unbound clusters or groups. These systems indicate that the dispersion rate of groups and clusters in IC 2574 is at most 0.45pc/Myr. The location of the groups found with HOP correlate well with HI contour map features. However, they do not coincide with HI holes, suggesting that those holes were not created by star-forming regions.2012AJ....144..182Phttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/AJ/144/182CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toVII/161 : Nearby Galaxies (Schmidt+ 1993)J/ApJ/744/44 : H{alpha} and UV fluxes in nearby galaxies (Weisz+, 2012)J/MNRAS/412/1539 : Ages of stars in dwarf galaxies (Bastian+, 2011)J/ApJ/733/87 : Star formation efficiency in galaxies (Shi+, 2011)J/ApJ/734/L22 : ACS Nearby Galaxy Survey Treasury (Williams+, 2011)J/ApJS/192/10 : Chandra ACIS survey in 383 nearby galaxies. I. (Liu, 2011)J/ApJ/714/1256 : Far-IR star formation rate indicators (Calzetti+, 2010)J/ApJS/190/147 : Mid-IR galaxy morphology from S4G (Buta+, 2010)J/PASP/122/1397 : Spitzer Survey of Stellar Structure in Gal. (Sheth+, 2010)J/ApJS/190/233 : Spectroscopy & abundances of SINGS gal. (Moustakas+, 2010)J/ApJ/701/1965 : Radial dust properties of SINGS gal. (Munoz-Mateos+, 2009)J/ApJ/706/516 : Gas content of star-forming gal. (Pflamm-Altenburg+, 2009)J/ApJ/703/517 : The Spitzer Local Volume Legacy: IR photometry (Dale+, 2009)J/AJ/136/2782 : Star formation efficiency in nearby galaxies (Leroy+, 2008)J/ApJS/173/185 : GALEX UV atlas of nearby galaxies (Gil de Paz+, 2007)J/AJ/120/1794 : Far-UV observations of the shell in IC 2574 (Stewart+, 2000)J/other/Ap/41.1 : Catalog of barred galaxies (Kandalian+, 1998)http://archive.stsci.edu/ : MAST Web sitehttps://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/AJ/144/182https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/AJ/144/182http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/AJ/144/182https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/AJ/144/182https://vizier.iucaa.in/viz-bin/votable?-source=J/AJ/144/182http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/AJ/144/182GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/AJ/144/182/groups (Physical properties of stellar groups)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/AJ/144/182/groups?https://vizier.iucaa.in/viz-bin/conesearch/J/AJ/144/182/groups?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/AJ/144/182/groups?GETtext/xml+votable180.050000true157.163437568.475194440.0055555555555555566/7624https://cdsarc.cds.unistra.fr/viz-bin/moc/J/AJ/144/182?format=asciidefaultJ/AJ/144/182/groupsPhysical properties of stellar groupsSizeSizepcphys.size.diameterintrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintSGSimbad column added by the CDSsrc.classnullableNameDispersed stellar group identifier (<[PMC2012] NNa> in Simbad)meta.id;meta.maincharprimaryXposx coordinate in the pixel map (see Figure 4)pixpos.cartesian.xintYposy coordinate in the pixel map (see Figure 4)pixpos.cartesian.yintRAJ2000Hour of Right Ascension (J2000)pos.eq.ra;meta.mainDEJ2000Degree of Declination (J2000)pos.eq.dec;meta.mainEll[0/1] Ellipticity {epsilon}src.ellipticityfloatPA[-115/200] Position angledegpos.posAngintn_Size[-?] - when interval, ? for other possible valuemeta.notecharSize1? Upper limit on Size if intervalpcphys.size.diameterintnullableNStar number density (in units of stars/pc^-2^)pc**-2meta.idfloatl_Age[?~<= ] Uncertainty or upper limit flag on Agemeta.code.error;time.agecharAgeCluster age (1)Myrtime.ageintf_Age[-,] Flag for interval (-), or alternative value (,) (2)meta.codecharAge1? Upper limit if interval or second value of AgeMyrtime.interval;stat.maxintnullableJ/AJ/144/182/notesNotesrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintNameDispersed stellar group identifiermeta.id;pos.lgcharNoteNotesmeta.notechar