Submillimeter Array observations of the L1157 protostellar jet

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Submillimeter Array observations of the L1157
protostellar jet
5th JETSET school

• 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
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L1157 bipolar outflow
CO(1-0) SiO (2-1)

• L1157 dark cloud 440 pc distant (VLSR2.7
  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
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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 gt 0.561 km/s
• Synthesized beam 3.4 x 2.3

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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

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SiO (5-4)
Velocity channel maps
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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
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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)
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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