Protostellar jets and outflows — what ALMA can achieve? —

平野 尚美 (Naomi Hirano)中研院天文所 (ASIAA)

Back to 1980... Discovery of the bipolar molecular

outflow from L1551 IRS5

Snell, Loren & Plambeck (1980)

A scenario of star formation

Why we study jets and outflows?

Jets are ubiquitous

from proto brown dwarfs (possibly proto planets), protostars, evolved stars, to active galactic nuclei

Key words

accretion, angular momentum, bipolar

Jets from young stellar objects (protostars)

spectroscopic observations allow us to study their kinematics → driving mechanism

Issues to be addressed‣ Can we see the primary jet ejected from the star?

CO outflows are likely to be swept-up ambient gas ≠

primary ejecta

‣ Are the jets and outflows transferring the excess

angular momentum from accreting material?

‣ Roles of magnetic field

Flow geometry v.s. magnetic field

‣ When and how jets and outflows start, and how they

evolve?

Highly-collimated jet from HH211

driving source:

cold (Tbol ~ 33 K) and low

luminosity (3.6 Lsun) protostar

CO J=2-1 observed with the JCMT

angular resolution: 20”

McCaughrean et al. (1994)Low velocity

- a pair of cavities

High velocity- narrow jet

CO J=2-1 observed with the PdBI

angular resolution: 1.5”

Gueth et al. (1999)

Highly-collimated jet:an important link between the primary jet and entrained outflow

HH211

Green: H2 in NIR, Blue & Red: SiO J=5-4Hirano et al. (2006)

Current achievement with the SMA

HH211SiO J=8-7

0.46”x 0.36”

0.35”x 0.23”

0.24”x 0.22”

Lee et al. (2009)

The innermost pair of knots

‣C-shaped bending

‣~4 sub-knots

‣transverse width < 40 AU

Observations with ALMA — 1

Search for the evidence of jet

rotation

Launhardt et al. (2009)

‣ Theoretical prediction

The jet is carrying out the excess angular momentum from accreting material

➡ The jet is spinning?

‣ Observationally, only one clear example has been known

‣ CO J=2-1 jet in CB26

• 1 Myr old star

• much older than the protostars in main accretion phase (< 105 yr)

The velocity gradient across the SiO jet in HH211

— a hint of jet rotation? —

- The NE side of the jet shows slightly larger velocity as compared to the SW side

- The mean velocity gradient

~0.5 km/s at ~10 AU (0.035”)

0.24” x 0.22”0.1” x 0.1”

Lee et al. (2009)

The velocity gradient across the SiO jet in HH212

SN: ~1 km/s @ 24 AUSS: ~1 km/s @ 73 AU

0.36” x 0.33”

0.1” x 0.1”

Lee et al. (2008)

Search for the rotation in the HH211 & HH212 jets

‣ Targets: HH211 & HH212

- The axes of these jets are close to the plane of the sky

➡ suitable for searching the velocity gradient across the jets

‣ Lines: SiO J=8-7, SO NJ=89-78, CO J=3-2

‣ 1 pointing centered at the protostelar positions

‣ Angular resolution: ~ 0.1”

- the jets need to be spatially resolved along their minor axes

Observations with ALMA — 2

Time variability of the jets

HH211 jet in 2004 and 2008

beam size: 1.28” x 0.84”time interval: 3.6 yrsproper motion: ~0.13” ± 0.04” per yeartransverse velocity: 170±60 km/s

The SiO emission from the innermost knot pair has increased

Multi-epoch observations at ~01”resolution

‣ Targets: HH211 & HH212

‣ Lines: SiO J=8-7, SO NJ=89-78, CO J=3-2

‣ 1 pointing centered at the protostelar positions

‣ Angular resolution: ~ 0.1”

‣ proper motion of the HH211 knots (0.13”per yr) can be detectable in 1 yr

‣ 3-epoch observations separated by 1 yr

‣ Variation of the structure of the innermost knots (e.g. new ejection event) is expected

Observations with ALMA — 3

B-field geometry the jets

Polarized CO J=2-1 and dust continuum emission in NGC 1333 IRAS 4

Girart, Crutcher & Rao (1999) Girart, Rao, & Marrone (2006)

B-field measurements using the polarized molecular lines

‣ Targets: HH211 & L1448C

‣ The SiO emission is bright in these sources

‣ Lines: SiO J=8-7, SO NJ=89-78, CO J=3-2

‣ 3--5 pointings (cover the inner ~30”area)

‣ Angular resolution: ~ 0.3”-- 0.5”

‣ Polarization measurements

‣ High dynamic range of >50 is necessary

‣ B-field in the jet v.s. B-field in the disk (from dust continuum observations)

‣ B-field in the jet v.s. B-field in the outflow shell

Observations with ALMA — 4

Search for the highly-

collimated molecular jets in

protostellar outflows

‣ Highly-collimated jet like HH211 is not common‣ Only seen in the extremely young sources

CO J=2-1 outflow from B335

Yen et al. (2010)

Search for the extremely high velocity jet in class 0 protostars‣ Targets: Class 0 protostars without

extremely high velocity jet

‣ First, try to start from B335

‣ Next, go to the various class 0 protostars

‣ Lines: CO J=3-2 or CO J=2-1

‣ 1 pointing centered at the protostelar positions

‣ Angular resolution: ~ 1”

‣ High sensitivity is essential

Near future directions

higher angular resolutiondown to < 0.1”

well studied objects-structure and kinematics near the base-jet rotation?, precession?-proper motion study-time variability study

evolutionary sequence~0.5–1” resolution

outflows in various evolutionary stages-when and how the outflow starts?-when and how the EHV jet develops and disappears?

outflow study with various lines

~0.5–1” resolution-shock chemistry-chemical evolution-which line is suitable for probing the primary ejecta?