Collapse and Fragmentation of Cylindrical Magnetized Clouds: Simulation with Nested Grid Scheme

Publications of the Astronomical Society of Japan

Tomisaka, Kohji¹ 

[1] Faculty of Education, Niigata University, 2-8050 Ikarashi, Niigata 950-21 E-mail:

关键词: "Interstellar: clouds";    "Interstellar: magnetic fields";    "Interstellar: medium";    Magnetohydrodynamics;    "Stars: formation";   

DOI  :  10.1093/pasj/48.5.701

学科分类：天文学(综合)

来源: Oxford University Press

【 摘 要 】

Thefragmentationprocessinacylindricalmagnetizedcloudhasbeenstudiedusingthenestedgridmethod.Thenestedgridschemeuses15levelsofgridswithincreasingspatialresolution,whichenabledustotracetheevolutionfrommolecularclouddensities∼100cm−3tothatofprotostellardisks,∼1010cm−3orhigher.Fluctuationswithsmallamplitudegrowduetoagravitationalinstability.Adiskisformedwhosesymmetricplaneisperpendiculartomagneticfieldlineswhichruninthedirectionparalleltothemajoraxisofthecloud.Matteraccretesontothedisk,mainlyflowingalongthemagneticfields.Thisincreasesthecolumndensity.Theradialinflowvelocityisslowerthantheflowperpendiculartothedisk,whichisdrivenbyanincreaseofthegravity.Thecontractioncontinuesindefinitelyforanisothermalequationofstateandwhilethemagneticfieldsareperfectlycoupledtomatter.Bothconditionsarerealizedinthedensityrangeofρ≲1010cm−3.Thestructureofthecontractingdiskreachesthatofasingularsolutionasthedensityandcolumndensityobeyρ(r)∝r−2andσ(r)∝r−1,respectively.Themagneticfieldstrengthinthemid-planeisproportionaltoρ(r)1/2andthefieldatthecenter(Bc)evolvesproportionallytothesquarerootofthegasdensity(∝ρc1/2).Itisshownthatisothermalcloudsexperiencea“run-away„collapse.Theevolution,includingahardeningoftheequationofstateduetoradiationtrapping,isalsodiscussed.

【 授权许可】

Unknown