J/MNRAS/517/632ivo://CDS.VizieR/J/MNRAS/517/632doi:10.26093/cds/vizier/bg-g5-krCDSLiu L.Bureau M.Li G.-X.Davis T.A.Nguyen D.D.Liang F.-H.Choi W.,Smith M.R.Iguchi S.2026-08-03T07:32:12Z2025-11-23T09:09:03ZCDS support team

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

cds-question@unistra.frdwarf-galaxiesinterferometryspectroscopyphotometrymillimeter-astronomysubmillimeter-astronomyradio-astronomyco-line-emissionmolecular-physicsmolecular-cloudsastrometryradial-velocitygalaxy-kinematicsWe present a study of molecular structures (clumps and clouds) in the dwarf galaxy NGC 404 using high-resolution (~0.86 * 0.51 pc^2^) Atacama Large Millimeter/sub-millimeter Array ^12^CO(2-1) observations. We find two distinct regions in NGC 404: a gravitationally stable central region (Toomre parameter Q = 3-30) and a gravitationally unstable molecular ring (Q <~ 1). The molecular structures in the central region have a steeper size-linewidth relation and larger virial parameters than those in the molecular ring, suggesting gas is more turbulent in the former. In the molecular ring, clumps exhibit a shallower mass-size relation and larger virial parameters than clouds, implying density structures and dynamics are regulated by different physical mechanisms at different spatial scales. We construct an analytical model of clump-clump collisions to explain the results in the molecular ring. We propose that clump-clump collisions are driven by gravitational instabilities coupled with galactic shear, which lead to a population of clumps whose accumulation lengths (i.e. average separations) are approximately equal to their tidal radii. Our model-predicted clump masses and sizes (and mass-size relation) and turbulence energy injection rates (and size-linewidth relation) match the observations in the molecular ring very well, suggesting clump-clump collisions are the main mechanism regulating clump properties and gas turbulence in that region. As expected, our collision model does not apply to the central region, where turbulence is likely driven by clump migration.2022MNRAS.517..632Lhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/MNRAS/517/632CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toJ/MNRAS/505/4048 : WISDOM Project IX study of GMCs in NGC 4429 (Liu+, 2021)J/MNRAS/431/1752 : ATLASGAL 6.7GHz methanol masers (Urquhart+, 2013)J/ApJ/921/130 : Local analogs to high-redshift galaxies. I.J/ApJ/901/L8 : Molecular gas properties of 70 PHANGS-ALMA galaxiesJ/ApJ/897/89 : 1482 Gaussian clumps in the Central Molecular ZoneJ/ApJ/876/141 : ALMA obs. of giant molecular clouds in Hen 2-10J/ApJ/860/172 : Cloud-scale molecular gas properties in 15 galaxiesJ/ApJ/835/278 : Molecular clouds in the dwarf galaxy NGC6822 (Schruba+,2017)J/ApJ/834/57 : Milky Way molecular clouds from ^12^COJ/ApJ/821/125 : SMA obs. of giant molecular clouds in NGC 300 (Faesi+, 2016)J/ApJ/803/16 : Giant molecular clouds in NGC4526 based on ^12^COJ/ApJ/784/3 : The PAWS catalogs of GMCs and islands in M51 (Colombo+,2014)J/ApJ/772/107 : Giant molecular clouds in nearby galaxiesJ/ApJ/723/492 : Physical properties of GRS molecular cloudsJ/A+A/645/A97 : ALMA cube and GMC catalog of J1023+1952 (Querejeta+, 2021)J/A+A/585/A117 : N131 bubble CO integrated intensity maps (Zhang+, 2016)J/ApJS/197/16 : CO observations of LMC molecular clouds (MAGMA).J/AJ/157/241 : HI clouds in LITTLE THINGS dwarf irregular galaxieshttps://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/MNRAS/517/632https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/MNRAS/517/632http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/MNRAS/517/632https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/MNRAS/517/632https://vizier.iucaa.in/viz-bin/votable?-source=J/MNRAS/517/632http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/MNRAS/517/632GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/MNRAS/517/632/table1 (*Properties of the dendrogram-defined structures of NGC 404)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/MNRAS/517/632/table1?https://vizier.iucaa.in/viz-bin/conesearch/J/MNRAS/517/632/table1?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/MNRAS/517/632/table1?GETtext/xml+votable180.050000true17.362535.7180.0055555555555555566/2282https://cdsarc.cds.unistra.fr/viz-bin/moc/J/MNRAS/517/632?format=asciiMillimeterRadiodefaultJ/MNRAS/517/632/table1*Properties of the dendrogram-defined structures of NGC 404recnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintIDIdentifier structure raw number (ID)meta.id;meta.mainintRAJ2000Right Ascension (J2000)pos.eq.ra;meta.mainDEJ2000Declination (J2000)pos.eq.dec;meta.mainVLSRThe Local Standard of Rest LSR velocity (V_LSR_)km/sphys.veloc;pos.lsr;meta.modelledfloatRcThe structure size radius (R_c_) (1)pcphys.size.radius;meta.modelled;arithfloate_RcMean uncertainty of Rc ({delta}R_c_) (5)pcstat.errorfloatsigmaThe one-dimensional observed linewidth velocity dispersion ({sigma}_obs,loc_)km/sphys.veloc.dispersion;meta.modelled;arithfloate_sigmaMean uncertainty of sigma ({delta}{sigma}_obs,loc_) (5)km/sstat.errorfloatLCO(2-1)The CO(2-1) luminosity L_CO(2-1)_ (L_CO (2-1)_)10000K.km.s**-1.pc**2phys.luminosity;em.mm.200-400GHz;meta.modelledfloate_LCO(2-1)Mean uncertainty of LCO(2-1) ({delta}L_CO (2-1)_) (5)10000K.km.s**-1.pc**2stat.errorfloatMcThe gaseous mass (M_c_) (2)100000solMassphys.mass;meta.modelled;arithfloate_McMean uncertainty of Mc ({delta}M_c_) (5)100000solMassstat.errorfloatRgDeprojected galactocentric distance (R_gal_) (3)pcpos.distance;pos.galactocentricfloatTypeStructure codes (Structure) (4)src.class.struct;meta.modelledchar