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Titolo:
Chemically active outflow L1157
Autore:
Bachiller, R; Gutierrez, MP; Kumar, MSN; Tafalla, M;
Indirizzi:
IGN Observ Astron Nacl, Alcala De Henares 28800, Spain IGN Observ Astron Nacl Alcala De Henares Spain 28800 enares 28800, Spain
Titolo Testata:
ASTRONOMY & ASTROPHYSICS
fascicolo: 3, volume: 372, anno: 2001,
pagine: 899 - 912
SICI:
1432-0746(200106)372:3<899:CAOL>2.0.ZU;2-D
Fonte:
ISI
Lingua:
ENG
Soggetto:
MOLECULAR ION SPECTRA; MASS STAR-FORMATION; SIO EMISSION; BIPOLAR OUTFLOW; MAGNETOHYDRODYNAMIC SHOCKS; MAGNETIC-FIELD; YOUNG STARS; DARK CLOUD; INTERSTELLAR; ABUNDANCES;
Keywords:
stars : formation; interstellar medium : individual objects : L 1157; interstellar medium : jets and outflows interstellar medium : molecules;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Physical, Chemical & Earth Sciences
Citazioni:
65
Recensione:
Indirizzi per estratti:
Indirizzo: Bachiller, R IGN Observ Astron Nacl, Apartado 1143, Alcala De Henares 28800, Spain IGN Observ Astron Nacl Apartado 1143 Alcala De Henares Spain 28800
Citazione:
R. Bachiller et al., "Chemically active outflow L1157", ASTRON ASTR, 372(3), 2001, pp. 899-912

Abstract

We present millimeter-wave maps of the L1157 bipolar out ow in several molecular emission lines. The CO emission traces the bulk of the out owing gasin the red and blue shifted lobes displaying a remarkable S-shaped symmetry indicating the presence of a precessing jet. We determine the physical characteristics of the CO ow and show evidence for 3 or 4 independent episodes of mass ejection from the source. Molecules such as C3H2, N2H+ and DCO+ are seen to be abundant only in the quiescent medium, and result to be the best tracers of the high-density core surrounding the driving source of the out ow. Other molecules (SiO, CH3OH, H2CO, HCN, CN, SO, SO2) are abundant in the out ow lobes, but exhibit strong emission gradients. Multiline observations of some species indicate that these gradients are not simply due to excitation effects, but are caused by an actual stratification in the chemical composition of the shocked molecular gas. Shock tracers such as SiO, CH3OH, and sulphur-bearing molecules result to be the most promising candidates as potential chemical clocks to study the evolution of outflows. The characteristics of the L1157 out ow, when compared to those of other outflows from Class 0 sources, indicate that L1157 is the prototype of a category ofbipolar outflows around Class 0 protostars which we denominate "chemicallyactive outflows".

ASDD Area Sistemi Dipartimentali e Documentali, Università di Bologna, Catalogo delle riviste ed altri periodici
Documento generato il 03/04/20 alle ore 20:33:59