A detailed temperature map of the archetypal protostellar shocks in L1157

Abstract

We present sensitive $\mathrm{N}{\mathrm{H}}_3$ (1,1)--(7,7) line images from the Karl G. Jansky Very Large Array toward successive shocks, which are associated with the blueshifted outflow lobe driven by the compact protobinary system L1157. Within a projection distance of 0.1 pc, our observations not only trace the quiescent and cold gas in the flattened envelope but also illustrate the complex physical and chemical processes that take place where the high-velocity jet impinges on its surrounding medium. Specifically, the $\mathrm{N}{\mathrm{H}}_3$ ortho-to-para ratio is enhanced by a factor of 2--2.5 along the jet path, where the velocity offset between the line peak and the blueshifted wing reaches values as high as $10\mathrm{km}{\mathrm{s}}^{-1}$; it also shows a strong spatial correlation with the $\mathrm{N}{\mathrm{H}}_3$ column density, which is enhanced to $>10^{16}\mathrm{c}{\mathrm{m}}^{-2}$ toward the shock cavities. At a linear resolution of 1500 au, our refined temperature map from the seven $\mathrm{N}{\mathrm{H}}_3$ lines shows a gradient from the warm B0 eastern cavity wall ($>120\mathrm{K}$) to the cool cavity B1 and the earlier shock B2 ($<80\mathrm{K}$), indicating shock heating.

Accepted by ApJL

References in corpus (19)

• The NumPy array: a structure for efficient numerical computation
• The Critical Density and the Effective Excitation Density of Commonly Observed Molecular Dense Gas Tracers
• Observing the gas temperature drop in the high-density nucleus of L 1544
• A Large Catalog of Accurate Distances to Local Molecular Clouds: The Gaia DR2 Edition
• An Ammonia Spectral Atlas of Dense Cores in Perseus
• The importance of the ortho:para H2 ratio for the deuteration of molecules during pre-protostellar collapse
• Seeds Of Life In Space (SOLIS): The organic composition diversity at 300--1000 au scale in Solar-type star forming regions
• Seeds of Life in Space (SOLIS) III. Formamide in protostellar shocks: evidence for gas-phase formation
• A Flattened Protostellar Envelope in Absorption around L1157
• First image of the L1157 molecular jet by the CALYPSO IRAM-PdBI survey
• The clumpy structure of the chemically active L1157 outflow
• Astrochemistry at work in the L1157-B1 shock: acetaldehyde formation
• Seeds of Life in Space (SOLIS) V. Methanol and acetaldehyde in the protostellar jet-driven shocks L1157-B0 and B1
• NH_3(1_0-0_0) in the pre-stellar core L1544
• The density structure of the L1157 molecular outflow
• HfS, Hyperfine Structure Fitting Tool
• Seeds of Life in Space SOLIS. IX. Chemical segregation of $\mathrm{S}{\mathrm{O}}_2$ and SO toward the low-mass protostellar shocked region of L1157
• SOFIA/EXES observations of warm H${}_2$ at high spectral resolution: witnessing para-to-ortho conversion behind a molecular shock wave in HH7
• A 16 au Binary in the Class 0 Protostar L1157 MMS

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