ALMA Observations of Keplerian Disks around Protostars:

the case of L1527Nagayoshi Ohashi (NAOJ)

NMA

With K. Saigo, Y. Aso, S.-W. Yen, S. Takakuwa, S. Koyamatsu, Y. Aikawa, K. Tomisaka, K. Tomita, M. Machida, M. Saito

SMA NMA ALMA

?

Summary• In order to unambiguously identify Keplerian disks around

protostars, it is crucial to distinguish between Kepler rotation (VrotR-0.5) and rotation conserving angular momentum(VrotR-1).

• ALMA cycle 0 observations of L1527 IRS shows that• Most of C18O 2-1 emission arises from an infalling envelope.• The C18O arising the vicinity of the central star (R < 60 AU) may

suggests a Keplerian disk.• SO 65-54 shows rigid-like rotation at lower velocities (V = -1 —

1 km/s)• The kinematics of the SO emission seems to be not explained

with the same kinematics explaining the C18O emission.

Keplerian disks are ubiquitous around PMSs

• Keperian disks are formed as by-products of star formation.

• It is, however, not well understood when and how disks are formed.• Initial condition of

Keprian disks• Dynamical mass of

protostars

Simon, Dutrey, Guilloteau 2000

Formation of Keplerian disks around protostars: A conventional picture

Dynamical Infall region Vinfall > Vrotation

Keplerian rotation region Vinfall << Vrotation

Note that B-field could remove angularNote that B-field could remove angularmomentum effectively, preventing diskmomentum effectively, preventing diskformation (e.g., Mellon & Li 2008, 2009;formation (e.g., Mellon & Li 2008, 2009;Machida et al. 2011, Dapp et al. 2012)Machida et al. 2011, Dapp et al. 2012)

NMA Obs

c. f. Terebey et al. 1984; Basu 1998

Previous studies to identify (Keplerian) disks around protostars

• Arce and Sargent 2006• Brinch et al. 2007• Lommen et al. 2008• Jorgensen et al. 2009• Lee et al. 2009, 2010• Maury et al. 2010• Tanner and Arce 2011• Tobin et al. 2011, 2012

If I miss your papers please kindly let me know!

(The list is NOT complete)

It has been difficult to firmly Identify Keplerian disks around protostars.

Inner regions of the infalling envelope around L1551 IRS5

SMA CS7-6 mean velocity

SMA CS 7-6 Total Intensity

NMA C18O 1-0

Takakauwa, Ohashi + 2004

Infall RotationNMA C18O (1-0) (Momose et al. 1998)

SMA CS7-6 mean velocity

Takakauwa, Ohashi + 2004

SMA CS 7-6

Infalling motions are dominant on large scales, while rotating motions are dominant on small scales

Are Kepler motions identified around L1551 IRS5?

• Sign of spin-up motion consistent with Kepler motion.

• R-1 dependence cannot be ruled out.

R-1 and R-0.5 dependences have to be carefully distinguished.

PV diagram of the SMA CS 7-6 data

Takakuwa et al. 2004

L1527 IRS (IRAS 04368+2557)

• Class0/I protostar

• Lbol ~ 1.9 Lsolar , Tbol ~ 56 K

• Wide opening outflow (Tamura et al. 1996)

• Infalling envelope of 1000 AU scale (Ohashi et al. 1997)

• Inclination~85°

Spitzer IRACTobin et al. (2008)

NMA C18O 1-0 Infalling Envelope

• Elongated envelope perpendicular to the outflow (Ohashi et al 1997).– 2000 AU in radius– Dynamical infall

– Vinfall ~ 0.3 km/s

– Vrotation ~0.05 km/s

– dM/dt ~ 1x10-6 Mo/yr

CARMA 13CO 2-1: Keplerian Disk?

NMA C18O 1-0

CARMA 13CO 2-1

Tobin et al. 2012 Nature

VrotR-1

VrotR-0.5

How to distinguish R-1 and R-0.5 dependences?

Rotation Curve with a logarithmic scale(Yen et al. 2013)

R < 500 AU ： Gaussian fit to the intensity profile at each channel

R > 500 AU: Gaussian fit to the spectrum at a given position

Posi

tion

(arc

sec)

Velocity (km s–1)

rotation curve with a logarithmic scale

C18O 2-1 with SMA

(Yen et al. 2013)

Position (arcsec)

Veki

city

(km

s–1

)

SMA C18O 2-1 Rotation Curve

Yen et al. 2013Radius (AU)

Velo

city

(km

s–1

)

ALMA Cycle 0 Observations

• In order to investigate kinematics of circumstellar material in detail (particularly rotation), three protostars, including L1527 IRS, have been observed with ALMA cycle 0.

• 12CO, C18O 2-1, SO 65-54, 220 GHz continuum etc

• ~ 0.96” x 0.73” (PA ~ 11 deg)• V ~ 0.17 km/s• L1527 IRS, TMC1A (Aso’s talk), L1489 IRS

c. f. Sakai et al. have observed L1527 IRS in C3H2, SO, etc. with ALMA cycle 0 as well (submitted)

ALMA can identify a compact rotating component around class 0 protostar!

SMA

280 AU

V = 2.5 km/s

140 AU

V = –2.5 km/s

Rotation Curve

N

S Rotation Radius (AU)Rotation Radius (AU)10050

Rota

tion

Velo

city

(km

s–1

)1

5

0.5

Rb ~ 54 ± 0.44 AUpin~ –0.41 ± 0.24Pout ~ -1.16 ± 0.13M* ~0.33 Mo

Summary• In order to unambiguously identify Keplerian disks around

protostars, it is crucial to distinguish between Kepler rotation (VrotR-0.5) and rotation conserving angular momentum(VrotR-1).

• ALMA cycle 0 observations of L1527 IRS shows that• Most of C18O 2-1 emission arises from an infalling envelope.• The C18O arising the vicinity of the central star (R < 60 AU) may

suggests a Keplerian disk.• SO 65-54 shows rigid-like rotation at lower velocities (V = -1 —

1 km/s)• The kinematics of the SO emission seems to be not explained

with the same kinematics explaining the C18O emission.