SiO J=5-4 in the HH211 Protostellar Jet Imaged with the SMA Naomi Hirano (ASIAA, Taiwan) (=^_^=) (=^_^=)/ Sheng-yuan Liu 1, Hsien Shang 1, PaulT.P. Ho 2, Hui-Chun Huang 3, Yi-Jehng Kuan 1,3, Mark McCaughrean 4, & Q. Zhang 2 1. ASIAA, Taiwan, 2. CfA, U.S.A., 3. NTNU, Taiwan, 4. U. of Exeter, U.K.

Outflows from protostars L1551 IRS5 How the outflows are launched and collimated? Highly-collimated outflow component An important link between the primary jet & entrained flow? CO outflow ≠ directly ejected material –ambient gas swept-up and entrained by the “unseen primary jet” Launching point < several AU from the star ?

HH211 — an archetype of outflow with highly-collimated jet Highly-collimated (aspect ratio ~ 15:1) outflow driven by the low- luminosity (3.6 Lo) Class 0 protostar (T bol ~ 33 K) Dynamical time scale ~ 750 yr Outflow axis ~ 10° from the plane of the sky

Cavity & jet observed in the CO J=2-1 Gueth et al with PdBI Low-velocity component V LSR = 2.2 – 18.2 km/s Cavity structure High-velocity component V LSR 18.2 km/s Jet-like structure HH211 — an archetype of outflow with highly-collimated jet Highly-collimated outflow (aspect ratio ~ 15:1) Driven by the low-luminosity (3.6 Lo) Class 0 protostar (T bol ~ 33 K) Dynamical time scale ~ 750 yr Outflow axis ~ 10° from the plane of the sky

HH211 outflow observed with the H 2 line McCaughrean et al. 2005

Shocked H 2 & continuum emission from HH211 Blue — continuum, Red — H 2 line

SiO J=5-4 observations with the SMA SiO J=3-2 observations with the NMA SiO J= GHz (LSB) 6 x 6m antennas at extended configuration - SiO J= GHz (LSB) - 6 x 10m antennas at AB, C, & D configurations

Why SiO? SiO emission is barely seen in the cold dark clouds – Si/C ~ 1/10 – SiO/CO < in TMC1 – SiO is heavily depleted onto the dust grain SiO is a good tracer of shocked molecular gas – Si or SiO is librated into the gas phase because of shock wave – SiO abundance is increase by several orders of magnitude

SiO J=5-4 jet beam: 1.60” x 0.88” P.A deg. Max: 2.09 Jy/beam T B ~ K

SiO 5-4 spectrum observed with the SMA and the JCMT SiO 5-4 spectrum observed with the SMA convolved with the 22” beam suggests that % flux was recovered by the SMA Almost all the SiO 5-4 emission comes from the narrow jet! No missing flux!

SiO J=3-2 jet beam: 1.49” x 1.30” P.A deg. Max: 0.62 Jy/beam T B ~ 93 K

Characteristics of the SiO jet The SiO jet is well collimated, and perfectly aligned with the knots seen in the shocked H 2 ➡ The SiO jet is closely linked with the H 2 jet No cavity component No SiO emission beyond ±20” ➡ Dense (> cm -3 ) & warm (> 150 K) jet is running along the axis of the low density cavity The SiO jet consists of a chain of knots separated by 3-4” (~1000 AU) ➡ Non-steady eruption?

Structure of the HH211 outflow lobe

SiO 5-4, 3-2 & 1-0 Higher transition of the SiO is better collimated and strong in the vicinity of the protostar The innermost knot pair (related to the latest activity) is seen only in the maps of higher transitions of SiO SiO 5-4 SiO 3-2 SiO 1-0 Chandler & Richer (2001), with the VLA H2H2

SiO 5-4/3-2 ratio SiO 5-4/3-2 line ratio is hign (~2) at the upstream and decreases toward the downstream High 5-4/3-2 ratio is seen along the flow axis red blue 1.6” x 1.6” resolution) LVG results (preliminary) - X(SiO)~ T K > K - n(H 2 ) ~ x 10 7 cm -3

Position-velocity map along the major axis Steep velocity gradient between the star and the innermost knots ±18 km/s at ±2” (~ 630 AU) dynamical age of the innermost knots < 175 yr The SiO jet is moving faster than the CO 2-1 jet –V(SiO ) ~ V(CO)+5 km/s SiO 5-4SiO 3-2

Summary The SiO jet is perfectly aligned with the H 2 jet The SiO 5-4 & 3-2 traces the dense (> 10 6 cm -3 ) and warm (> 150 K) jet running along the axis of the low-density cavity The excitation condition of the SiO jet varies along the radial and axial direction (SiO 5-4/3-2 ratio, SiO 5-4, 3-2, & 1-0 maps) The dense and warm jet component with higher velocity (traced by the SiO) is surrounded by the less dense cold, and lower-velocity component (traced by the CO) The innermost pair of knots at 2” from the source are first discovered with the SiO 5-4 and High excitation & high velocity --> these knots are closely linked to the primary jet

The high excitation SiO lines in the submillimeter waveband provide us with the key to understand the launching mechanism of the protostellar outflow