2014/10/30 by Arturo I. Gómez-Ruiz, A. I. Gómez-Ruiz, C. Codella +8 · 37 citations
Chemistry · Earth and Planetary Sciences · Physics and Astronomy · #Astrophysics #Astrophysics and Star Formation Studies #Atmospheric Ozone and Climate #Bow shock (aerodynamics) #Excitation #Jet (fluid) #Line (geometry) #Mechanics #Molecular Spectroscopy and Structure #Outflow #Physics #Shock (circulatory) #Shock wave #astro-ph.GA
paper · pdf · doi:10.1093/mnras/stu2311
published in Monthly Notices of the Royal Astronomical Society 446(4), 3346-3355 (Oxford University Press) · 11 pages, 10 figures, accepted for publication in Monthly Notices of the Royal Astronomical Society (MNRAS)
arxiv created 2014/10/30 · openalex publication_date 2014/12/08 · arxiv updated 2015/06/23 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
We present a multiline CS survey towards the brightest bow-shock B1 in the prototypical chemically active protostellar outflow L1157. We made use of (sub-)mm data obtained in the framework of the Chemical HErschel Surveys of Star forming regions and Astrochemical Surveys at IRAM (ASAI) key science programs. We detected 12C32S, 12C34S, 13C32S, and 12C33S emissions, for a total of 18 transitions, with Eu up to ∼180 K. The unprecedented sensitivity of the survey allows us to carefully analyse the line profiles, revealing high-velocity emission, up to 20 km s−1 with respect to the systemic. The profiles can be well fitted by a combination of two exponential laws that are remarkably similar to what previously found using CO. These components have been related to the cavity walls produced by the ∼2000 yr B1 shock and the older (∼4000 yr) B2 shock, respectively. The combination of low- and high-excitation CS emission was used to properly sample the different physical components expected in a shocked region. Our CS observations show that this molecule is highlighting the dense, nH2 = 1–5 × 105 cm−3, cavity walls produced by the episodic outflow in L1157. In addition, the highest excitation (Eu ≥ 130 K) CS lines provide us with the signature of denser (1–5 × 106 cm−3) gas, associated with a molecular reformation zone of a dissociative J-type shock, which is expected to arise where the precessing jet impacting the molecular cavities. The CS fractional abundance increases up to ∼10−7 in all the kinematical components. This value is consistent with what previously found for prototypical protostars and it is in agreement with the prediction of the abundances obtained via the chemical code Astrochem.