magnec fields and turbulence in molecular clouds · centroid‐velocity (cv) in translucent...
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Magne&cfieldsandturbulenceinmolecularclouds:
observa&onsfrom30‐parsectomilliparsecscales
EdithFalgaroneENS&ParisObservatory,France
and
PierreHily‐BlantGrenobleObservatory,France
``CosmicMagne&sm’’,7‐11june2010,Kiama
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Kainulainenetal2009
Av<3–5mag:turbulent+BdominatedAv>3‐5mag:gravity+B+?
Bimodaldistribu&onofgascolumndensi&esinmolecularclouds
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Outline
• Sta&s&csofBPOSorienta&onatthe30‐pcscale• BPOSandintensevelocity‐shearsatthepcscale• BPOSandshear‐layersatthempc‐scale• B//intensityfromdiffusemediumtodensecores
Tools:‐Starlightpolariza&on‐ Spectro‐imageryathighspectralandspa&alresolu&onintheCOrota&onallines‐ Zeemaneffectobserva&onsintheHI,OHandCN(1‐0)lines
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1–Turbulentandmagne&cenergyatthe30pc‐scale
• Comparisonofvirialized(TaurusComplex)andnon‐virialized(PolarisFlare)fields
• Chandrasekhar‐Fermimethod:
B=6.6nH1/2(Δv/δφ)μG
Emag/Eturb=(38o/δφ)2
Validforδφ<25o(MHDsimula&onsOstrikeretal.01)
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Two30‐pcscalefields:
PolarisFlareFIRmapMiville‐Deschênesetal.
Δv=4.8km/s
Taurus‐AurigacomplexN(H2)mapGoldsmithetal.08
Δv=3.8km/sComparablevirialmasses@30pc:MV=4.4x104Msun
TaurusComplex:Mgas≈MVPolarisFlare:Mgas=5x103Msun=MV/6
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Polarisa&onmeasurementsHeiles2000
12CO(1‐0)(top)13CO(1‐0)(borom)
δφ=(24±5)o
Emag/Eturb=2.5
Tauruscomplex
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δφ=19o
NonGaussianPDF:3morecommonPA
Emag/Eturb≈4.0
Hily‐Blantetal.inprepara&on At30pc‐scale,Emag>Eturb≥Egrav
PolarisFlare
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2–BPOSandvelocity‐shearsattheparsec‐scale
• Sta&s&csonvelocityfieldbasedonCOline‐centroid‐velocity(CV)intranslucentfields
• DeparturefromGaussiansta&s&cs
• Comparisonofplane‐of‐skyprojec&onofmagne&cfieldsBPOSandlocusofextremeCVincrements(E‐CVI):extremaofΩPOSHily‐Blant&Falgarone09
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Parsec‐scalefieldinthePolarisFlare
Hily‐Blant&Falgarone2009
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PDFofcentroidvelocityincrementswithvariablelags
• Non‐Gaussiantailsincreaseatsmallerlags:moreandmorerareevents
• Locusoftheseevents:E‐CVIs∼extremaofΩPOS
(Lisetal1996)
• Intermirencyofturbulence
Hily‐Blant,Falgarone,Pety2008
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Spa&aldistribu&onofextremeCVIs(1)
Ward‐Thomsonetal.(2010)Herschel/SPIRE
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Spa&aldistribu&onofE‐CVIs(2)
TaurusedgeTaurusedge:BPOS//ΩPOS:oneclosemeasurement
PolarisFlare:Specificorienta&onsofBPOSSharpPAchangesNoclosemeasurementΩPOS//BPOSatparsec‐scale
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3–BPOSandshear‐layersatmilliparsecscales
Dusttemperature
IRAM‐PdBICO(1‐0)line.Mosaicof13fields,180hoursintegra&onPixelsize:3mpc(4arcsec)Fieldsize:0.09pcx0.045pcTranslucentfieldwithnostructurevisibleat0.01pcresolu&on
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Structureatthemilliparsecscale
‐8straightstructuresdetected,thickness3to11mpc‐SpecificPA‐Specificveloci&es(emptychannels)
Falgarone,Pety,Hily‐Blant2009
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Notfilaments:sharpedgesofthinextendedsheetsofCOemission
COemissionin2velocityranges:seenbytheIRAM‐PdBinterferometer(lex)andmergedwithshortspacingsfromIRAM‐30m(right)
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4edgesformpairsofparallelstructuresofhighvelocityshear:milliparsecscaleshear‐layers
➜
➜ComparisonwithBPOSorienta&onsatthe30‐pcscale
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Thelessonsofthemilliparsecscales
• Layersofmostintensevelocity‐shearsatmpc‐scalesandBlieinparallelplanes:quasi‐parallelprojec&onsontheplane‐of‐sky→BPOS//ΩPOS
• Coherenceoforienta&onsacrossscales• Velocityincrementsinshear‐layersatmpc‐scalesofsameorderasrmsvelocityoflargescaleturbulence(2to4kms‐1)→widescalesepara&on
• Largestobservedvelocity‐shear:3.5kms‐1over7mpcor500kms‐1pc‐1orequivalent&mescale≈2000yr
→short&mescales
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4‐HI,OH,CNZeemanmeasurements(1)
Line:M/Φ=(M/Φ)cri&cal
Noevidenceforsubcri&caldensecores
Crutcheretalinprep.
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HI,OH,CNZeemanmeasurements(2)
Bayesiananalysis:n<300cm‐3
Bmax=10μGBnotcompressedbyturbulencen>300cm‐3
Uniformdistribu&onofBTOTbetween≈0andBmax∝n2/3
WeakBindensecores
Crutcheretalinprep.
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SummaryandOpenings(1)
• At30pcscales,magne&c>turbulentenergy• Coherentstructuresofvor&city/shearsparalleltoBPOSfromparsectomilliparsecscales
• Widescalesepara&on
• Diffusemedium:Bnotcompressedbyturbulence
• Noevidenceforsubcri&caldensecores
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SummaryandOpenings(2)
• Turbulence(anditspropertyofintermirency)possiblyattheoriginofthelossofmagne&cfluxofmarer
• Ion‐neutralambipolardrixinthediffusemediumrequiredtoexplainitsrichchemistry:Herschel/HIFIresultsFalgaroneetal.2010
• ModelsofwarmchemistryincoldgasGodardetal2009