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Submillimeter Array observations of the L1157 protostellar jet

This study presents submillimeter array (SMA) observations of the L1157 protostellar jet, focusing on the bipolar outflow and its molecular line emission. The observations reveal a precessing bipolar outflow with different ejection events, strong SiO emission, and a clumpy structure tracing the cavity walls. The chemical stratification observed suggests different physical conditions along the cavity walls. The study is still analyzing the multi-line analysis of the SiO emission to determine the physical conditions.

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Submillimeter Array observations of the L1157 protostellar jet

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  1. 5th JETSET school Submillimeter Array observations of the L1157 protostellar jet Arturo I. Gomez Centro de Radioastronomia y Astrofisica UNAM, Mexico Collaboration: Naomi Hirano & Shen-Yuan Liu Academia Sinica Institute of Astronomy and Astrophysics ASIAA, Taiwan Laurent Loinard CRyA-UNAM Mexico

  2. L1157 bipolar outflow CO(1-0) SiO (2-1) • L1157: dark cloud 440 pc distant (VLSR=+2.7 km/s); Class 0 source with 11 Lsun • Precessing bipolar outflow with a mean dynamical age of 15 000 yrs • Strongest molecular line emission from the blue-lobe in several species • Two cavities related with different ejection events (C1 older than C2) • Prototype of chemically active outflows (shock chemistry) • Chemical stratification along the lobe (Bachiller et al., 2001; Benedettini et al., 2007) C2 C1 Bachiller et al., 2001 Gueth et al., 1998

  3. SMA observations • SMA observations in the compact-north configuration • 4 pointings separated by 30” to cover the entire blue lobe • Frequency coverage 216.6 to 218.6 GHz (LSB) and 226.6 to 228.6 GHz (USB) • Spectral resolution of 406.25 kHz across 2 GHz band => 0.561 km/s • Synthesized beam ~ 3.4’’ x 2.3’’

  4. General Results • Four molecular lines detected in LSB SiO(5-4) 217.10798 GHz H2CO 3(3,0)-2(0,2) 218.22218 GHz H2CO 3(2,2)-2(2-1) 218.47561 GHz CH3OH 4(2,2)-3(1,2)E 218.44000 GHz • Molecular emission comes from S2 and S3 shocks (C2) • SiO is the strongest of the lines detected • H2CO 3(2,2)-2(2,1) and CH3OH are the weakest lines

  5. SiO (5-4) Velocity channel maps

  6. SiO (5-4) • Several clumps around S2 and S3 shocks (from -15.4 to +2.8 km/s) • SiO clumps located along the outer edge of the eastern wall of the cavity traced by CO emission • In contrast with single-dish map, SiO(5-4) is barely seen in S1 shock • SMA observations only showing the compact high-velocity emission in S2; extended low-velocity emission shown by single-dish data SMA SiO(5-4);CO(1-0) & SiO(2-1), Gueth et al., 1998

  7. SiO and H2CO • H2CO emission from -4 to +2 km/s along C2 • SiO peaks close to the apex of the bow-shock; H2CO peaks along the eastern cavity wall • SiO along the outer edge of the eastern wall of the CO cavity; H2CO presents a cluster of clumps along the inner edge of the same part of the cavity • They are likely tracing different physical conditions SiO (5-4) H2CO* DEC (J2000) RA (J2000) * H2CO 3(3,0)-2(0,2)

  8. Conclusions • Clumpy structure of SiO and H2CO, tracing the C2 cavity walls • SMA observations show the SiO emission tracing a compact high-velocity structure in S2 shock • Emission barely seen along S1 shock, likely due to the lack of short-spacing information or sensitivity, but could be an indication of the older ejection event • Chemical stratification of the molecular lines, likely indicating different physical conditions through the cavity walls • Still working on the determination of physical condition through multi-line analysis of the SiO emission

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