Infall and Rotation around Young Stars Formation and Evolution of Protoplanetary Disks Michiel R. Hogerheijde Steward Observatory The University of Arizona

Outline An overview of star formation Rotation in interstellar clouds Decoupling of collapsing cores Formation of disks L1489 IRS: A transitional object with a contracting disk? Summary and further work

Outline An overview of star formation Rotation in interstellar clouds Decoupling of collapsing cores Formation of disks L1489 IRS: A transitional object with a contracting disk? Summary and further work

An overview of star formation (Hogerheijde 1998; after Shu et al. 1987)

Cloud Structure Cloud complex Filaments Cores Kernels Motte & André (2001)

Outline An overview of star formation Rotation in interstellar clouds Decoupling of collapsing cores Formation of disks L1489 IRS: A transitional object with a contracting disk? Summary and further work

Rotation in interstellar clouds Line width – size relation Specific angular momentum – size relation Magnetic breaking Turbulence as a source of rotation

Rotation in interstellar clouds v–R relation (Larson 1981) Larson (1981) v R 0.5

Rotation in interstellar clouds Line width – size relationship v R, = (Caselli & Myers 1995) Virial equilibrium: 2K+W=0 M v 2 -GM 2 /R=0 v R 0.5 Turbulent and/or rotational support for cloud cores

Rotation in interstellar clouds J/M–R relation (Goodman et al. 1993) R -0.4 ~ constant J/M R 1.6 Goodman et al. (1993)

Rotation in interstellar clouds

Magnetic breaking (Königl 1987; Mouschovias 1991) Basu (1997)

Rotation in interstellar clouds Turbulence as a source of rotation (Burkert & Bodenheimer 2000) n=-4 n=-3 n=-2 Different realizations p(k)~k n J/M= km s -1 pc =0.03, independent of R Burkert & Bodenheimer (2000)

Outline An overview of star formation Rotation in interstellar clouds Decoupling of collapsing cores Formation of disks L1489 IRS: A transitional object with a contracting disk? Summary and further work

Decoupling of collapsing cores Goodman et al. (1998) R>0.1 pc v R 0.5 R<0.1 pc v R 0 Transition to coherence Scale corresponds to clustering-scale of young stars in Taurus (Larson 1995) (dramatization) Goodman et al. (1998)

Decoupling of collapsing cores Ohashi et al. (1997) Two embedded YSOs in Taurus IRAS : rotating, flattened envelope; must be infalling too IRAS : compact core; could be rotationally supported R~0.1 pc Ohashi et al. (1997)

Decoupling of collapsing cores Belloche et al. (2002) Deeply embedded YSO IRAM Outflow Flattened envelope Spectral signature of infall Position-velocity diagram suggests rotation Belloche et al. (2002)

Decoupling of collapsing cores 1D model of infall 2D model of rotation Break at ~3300 AU (0.02 pc) Infall: constant inside-out Rotation: slow spin up Mass reservoir ~0.5 M Belloche et al. (2002)

Outline An overview of star formation Rotation in interstellar clouds Decoupling of collapsing cores Formation of disks L1489 IRS: A transitional object with a contracting disk? Summary and further work

Formation of disks Terebey, Shu, & Cassen (1984; TSC84) Inside-out collapse: a sound, t Slow rotation, solid body: Centrifugal radius R c a sound t 3 2 Initial growth of disk small (t<1) Rapid growth at late times (t>1): infall of material from large R with large R

Formation of disks Basu (1998) Weak magnetic field Magnetic breaking: differential rotation R -1 R c t 2 Rapid initial growth Later growth linear: material at large R has smaller initial TSC84 Basu (1998)

Formation of disks Stahler et al. (1994) Growth of disk in TSC84 framework 3 regions Inner dense disk, Keplerian, R<R d Outer tenuous disk, rapid inflow, R d <R<R c Narrow dense ring where mass and angular momentum piles up, R d 0.34 R c Adapted from Stahler et al. (1994)

Formation of disks Shear motions dissipated by viscosity Source of viscosity unknown; turbulence? viscosity: = a sound H (Shakura & Sunyaev 1973) Stellar irradiation, viscosity sets up temperature distribution T R -1/2 R Resulting surface density distribution (R)= 0 (R/R 0 ) -1 (Lynden-Bell & Pringle 1974; Pringle 1981) Continued evolution: disk spreading while matter accretes onto star

Formation of disks Vertical scale height H set by temperature Increased angle of interception stellar light raises temperature Result: Flaring disk (e.g., DAlessio et al. 1998; Chaing & Goldreich 1997; Dullemond et al. 2001)

Outline An overview of star formation Rotation in interstellar clouds Decoupling of collapsing cores Formation of disks L1489 IRS: A transitional object with a contracting disk? Summary and further work

L1489 IRS: A transitional object with a contracting disk? L1489 IRS = IRAS L bol =3.7 L embedded YSO Taurus, d~140 pc Very weak outflow HST/NICMOS: inclined, cleared-out cavity (Padgett et al. 1999) Padgett et al. (1999)

L1489 IRS: A transitional object with a contracting disk? SCUBA submillimeter continuum images, 850 and 450 µm Compact emission around star Extended starless core 8000 AU to north-east Hogerheijde & Sandell 2000

L1489 IRS: A transitional object with a contracting disk? Hogerheijde & Sandell 2000 Best-fit Shu (1977) parameters: a sound =0.46±0.04 km s -1 t=(1.3–3.2) 10 6 yr r CEW =130,000–300,000 AU >> core

L1489 IRS: A transitional object with a contracting disk? Hogerheijde & Sandell 2000 Classic infall signature Can fit collapse model to data, but not for same (a sound, t)

L1489 IRS: A transitional object with a contracting disk? Hogerheijde & Sandell 2000 L1527 IRS Classic infall signature Well fit for same (a sound, t)

L1489 IRS: A transitional object with a contracting disk? Hogerheijde & Sandell 2000 TMC1 Classic infall signature Well fit for same (a sound, t) Not a problem with the Shu (1977) inside out collapse model

L1489 IRS: A transitional object with a contracting disk? BIMA and OVRO millimeter interferometer maps HCO + J=1–0 and 3–2 Resolution ~5 =700 AU Rotating disk, not infalling envelope Radius ~2000 AU, >> typical disk around T Tauri stars 2000 AU Hogerheijde 2001

L1489 IRS: A transitional object with a contracting disk? Position–velocity diagrams look like Keplerian rotation Velocity (km s -1 ) Offset (AU) Flared disk Keplerian rotation around M =0.65 M v in =1.3 (R/100 AU) -0.5 km s -1 M disk =0.02 M (from SCUBA) Hogerheijde 2001

L1489 IRS: A transitional object with a contracting disk? Interferometer and single-dish spectra reproduced Including infall signature Requires some foreground absorption in HCO + 1–0 Hogerheijde 2001

L1489 IRS: A transitional object with a contracting disk? L1489: Rotation>infall Life time yr M disk / M yr -1 L acc 7 L > L bol Inferred: L acc <0.3 L TMC1: Rotation<infall R c at 360 AU Expanding t 3 Reaches 2000 AU in another (1–2) 10 5 yr, ~twice current age and >> life time L1489s disk Hogerheijde (2001)

Open questions Transitional large-disk stage? Redistribution of angular momentum, leading to smaller disk as seen around T Tauri stars? Do inward motions continue all the way to the star?

L1489 IRS: A transitional object with a contracting disk? Keck/NIRSPEC CO gas and ice absorption lines at 4.7 µm (Boogert et al. 2002) 12 CO ro- vibrational P,R lines 13 CO ro- vibrational lines + 12 CO ice band C 18 O ro- vibrational lines

L1489 IRS: A transitional object with a contracting disk? Average line profiles 13 CO < 12 km s CO wing extends to +100 km s -1 Wings present in entire P,R branches Infall to within 0.1 AU from star Boogert et al. (2002)

L1489 IRS: A transitional object with a contracting disk? Infall model: Predicted average line profile Flatter density profile: skimming flared disk surface Infall model: Predicted average line profile Flatter density profile: skimming flared disk surface Add 10% scattered star light Boogert et al. (2002)

L1489 IRS: A transitional object with a contracting disk? Large disk, R~2000 AU Inward motions from 2000 to <0.1 AU Life time ~ yr 5% embedded phase Disk settling to rotationally supported size? Supersonic motions Disk instability? Mass accretion rate >> observed if entire (inner) disk flows in Inflow in surface layer only?

Summary and future work Cloud cores have velocity structure resembling rotation Turbulent origin likely Rotation not important for cores dynamics Dense condensations decouple from magnetic breaking, spin up. R~4000–20,000 AU Disk forms at center, grows t 1…3 L1489 IRS: short-lived transitional stage, where large disk settles to Keplerian structure Continued inflow puzzling. Contrary to expectation of viscous disk (subsonic accretion; disk spreading)

Summary and future work Find more objects like L1489 IRS: ~5% of YSOs Orientation of L1489 IRS may be advantageous Higher resolution observations of disks velocity structure: SMA, CARMA, ALMA Different chemical tracers: disk interior vs. surface