Accretion Disks

Accretion DisksProf. Hannah Jang-CondellAccretion DisksGalaxy: M81Protoplanetary Disk: AB Aurigae

Neutron Star(artists conception)(Giovanni Benintende)(M. Masetti, NASA)(Fukagawa, et al. 2004)

Why are disks so common?

M. Hogerheidge 1998, after Shu et al. 1987Why are disks so common?Initial material has random velocitiesAngular momentum is conserved as material falls inThe final disk is oriented in the direction of the total net angular momentumSide note: GalaxiesWhy are elliptical galaxies not disk-like?Stars are collisionless, dont get canceling of angular momentum as with gas.Accretion DisksGalaxy: M81Protoplanetary Disk: AB Aurigae

Neutron Star(artists conception)Central object = supermassive black holeDisk = gas in the galaxyCentral object = neutron starDisk = material pulled off a companion starCentral object = young star

Disk = gas left over from star formation

DefinitionAn accretion disk a structure that enables the transport and dissipation of angular momentum so that gaseous material can fall onto a central object. Viscous spreading of a ring

Mass moves inwardA small amount of mass carries angular momentum to infinityPringle 1981Angular Momentum TransportAngular Momentum TransportAngular Momentum TransportRed ring slows green due to viscosityGreen loses angular momentumAngular Momentum TransportRed ring slows green due to viscosityGreen loses angular momentumGreen ring slows blueBlue loses angular momentumAngular Momentum TransportEach ring loses angular momentum to the next outer ring.Mass moves inward.ViscosityNeeded to enable angular momentum transportMolecular viscosity of gas is not enoughPrime suspect: turbulenceTurbulent ViscosityRandom movement of gas parcels couples adjacent streamlinesConvectionGravitational instabilityMagneto-rotational instability (MRI)Magneto-rotational Instability(Balbus & Hawley 1991)Weak polar magnetic fieldIdealized plasma (gas is ionized)Magnetic field acts as a spring linking adjacent gas parcels

Disk inner edge and Outflows

Outflows carry away angular momentum, so inner edge of disk can accreteCollimated by magnetic fieldsExactly how outflows are launched is uncertainWood 2003Outflows and JetsAGN: 3C175Protoplanetary Disk: HH30Neutron Star:Crab Nebula(NRAO)(Chandra, NASA/CXC/MSFC/M.Weisskopf et al.)(Hubble)

Crab Nebula, 11/00-4/01

ChandraHubbleDisk StructureViscosity acts like friction allowing angular momentum transportThis friction also dissipates energy and heats the diskSpectrum of a Disk

Eddington LimitLimit where radiation pressure overcomes gravity:Can relate this to a maximum accretion rate:( is the efficiency of converting mass into energy, ~0.08 for BH)Many AGN and X-ray binaries are close to Eddington, or even higher

Accretion Disk PropertiesAGNProtoplanetary DiskX-ray binary(WD/NS/BH)Central mass106 1010 Msun0.1 2 Msun0.6 1.4 10 MsunDisk mass~103 Mstar (bulge)0.01 0.1 Mstar~1 MsunDisk size0.1 1 pc100 1000 AU~0.1 AUAccretion rate~ 1 Msun/yr10-9 10-7 Msun/yr10-10 10-8 Msun/yrTemperatures103 105 K10 1000 K103 104 KWavelengthsUV, X-rayIR, radioUV, X-ray

My researchProtoplanetary disksPassively accreting well below Eddington (not a compact object)Primary heat source is stellar illumination beyond a few AUHow do planets forming planets interact with disks?Gap Opening by Planets

Bate et al., 2003Gap-opening threshold (Crida, et al 06)1 MJ0.3 MJ0.1 MJ0.03 MJMay 9, 2012Hannah Jang-Condell

Mcrit = 1 MJ25

Aristarchus crater, the MoonCredit: NASA (Apollo 15)Shadowed GapMay 9, 2012Hannah Jang-Condell26

No planet 70 MEarth200 MEarthGapAt 10 AU1 m30 m100 um

Jang-Condell & Turner, 2012

May 9, 2012Hannah Jang-CondellTW Hya

56 parsecsHubble observationsSTISNICMOS7 wavelengthsDebes, Jang-Condell, et al. (submitted)

May 9, 2012Hannah Jang-Condell28TW HyaMatch spectral and spatial dataDust opacitiesSize distributionCompositionMay 9, 2012Hannah Jang-Condell

29Multi-wavelength FitFit parameters:Gap depthGap widthGrain sizeDisk truncation

Gap depth 30% 3-10 Earth mass planet

Debes et al., submittedMay 9, 2012Hannah Jang-Condell

30Inclined DisksInclinationbrighterdimmerMay 9, 2012Hannah Jang-Condell

InclinationbrighterdimmerMay 9, 2012Hannah Jang-Condell

1 0.11000 11000 0.1Jang-Condell & Turner, in prepMay 9, 2012Hannah Jang-CondellDisk Profiles

Can recover:Inclination within 1disk thickness within 3

May 9, 2012Hannah Jang-Condell

1 um10 um30 umMay 9, 2012Hannah Jang-Condell

0.1 mm0.3 mm1 mmMay 9, 2012Hannah Jang-Condell

Thalmann et al., 2010H-band scattered light(Mulders, et al. 2010)(Espaillat, et al. 2008)Mp < 6 MJ

LkCa 15May 9, 2012Hannah Jang-Condell

Thalmann et al., 2010H-band scattered light(Mulders, et al. 2010)(Espaillat, et al. 2008)Mp < 6 MJ

LkCa 151.5 MJ