scholarly journals Molecules in the Cep E-mm jet: evidence for shock-driven photochemistry?

2019 ◽  
Vol 490 (2) ◽  
pp. 2679-2691 ◽  
Author(s):  
J Ospina-Zamudio ◽  
B Lefloch ◽  
C Favre ◽  
A López-Sepulcre ◽  
E Bianchi ◽  
...  
Keyword(s):  
Chemical Composition ◽  
Molecular Species ◽  
Abundant Species ◽  
Intermediate Mass ◽  
Turbulent Layer ◽  
Large Velocity ◽  
Protostellar Jets ◽  
Line Survey ◽  
Molecular Abundances ◽  
Large Velocity Gradient

ABSTRACT The chemical composition of protostellar jets and its origin are still badly understood. More observational constraints are needed to make progress. With that objective, we have carried out a systematic search for molecular species in the jet of Cep E-mm, a template for intermediate-mass Class 0 protostars, associated with a luminous, high-velocity outflow. We made use of an unbiased spectral line survey in the range 72–350 GHz obtained with the IRAM 30-m telescope, complementary observations of the CO J = 3–2 transition with the JCMT, and observations at 1 arcsec angular resolution of the CO J = 2–1 transition with the IRAM Plateau de Bure Interferometer. In addition to CO, we have detected rotational transitions from SiO, SO, H2CO, CS, HCO+, and HCN. A strong chemical differentiation is observed in the southern and northern lobes of the jet. Radiative transfer analysis in the large velocity gradient approximation yields typical molecular abundances of the order of 10−8 for all molecular species other than CO. Overall, the jets exhibit an unusual chemical composition, as CS, SO, and H2CO are found to be the most abundant species, with a typical abundance of (3–4)× 10−8. The transverse size of the CO jet emission estimated from interferometric observations is about 1000 au, suggesting that we are detecting emission from a turbulent layer of gas entrained by the jet in its propagation and not the jet itself. We propose that some molecular species could be the signatures of the specific photochemistry driven by the UV radiation field generated in the turbulent envelope.

scholarly journals A sensitive λ 3 mm line survey of L483

2019 ◽  
Vol 625 ◽  
pp. A147 ◽  
Author(s):  
M. Agúndez ◽  
N. Marcelino ◽  
J. Cernicharo ◽  
E. Roueff ◽  
M. Tafalla
Keyword(s):  
Chemical Composition ◽  
Chemical Characterization ◽  
Isotopic Ratios ◽  
Dark Cloud ◽  
Carbon Chains ◽  
Prestellar Cores ◽  
Low Mass ◽  
Line Survey ◽  
Molecular Abundances

An exhaustive chemical characterization of dense cores is mandatory to our understanding of chemical composition changes from a starless to a protostellar stage. However, only a few sources have had their molecular composition characterized in detail. Here we present a λ 3 mm line survey of L483, a dense core around a Class 0 protostar, which was observed with the IRAM 30 m telescope in the 80–116 GHz frequency range. We detected 71 molecules (140 including different isotopologs), most of which are present in the cold and quiescent ambient cloud according to their narrow lines (FWHM ~ 0.5 km s−1) and low rotational temperatures (≲10 K). Of particular interest among the detected molecules are the cis isomer of HCOOH, the complex organic molecules HCOOCH3, CH3OCH3, and C2H5OH, a wide variety of carbon chains, nitrogen oxides like N2O, and saturated molecules like CH3SH, in addition to eight new interstellar molecules (HCCO, HCS, HSC, NCCNH+, CNCN, NCO, H2NCO+, and NS+) whose detection has already been reported. In general, fractional molecular abundances in L483 are systematically lower than in TMC-1 (especially for carbon chains), tend to be higher than in L1544 and B1-b, and are similar to those in L1527. Apart from the overabundance of carbon chains in TMC-1, we find that L483 does not have a marked chemical differentiation with respect to starless/prestellar cores like TMC-1 and L1544, although it does chemically differentiate from Class 0 hot corino sources like IRAS 16293−2422. This fact suggests that the chemical composition of the ambient cloud of some Class 0 sources could be largely inherited from the dark cloud starless/prestellar phase. We explore the use of potential chemical evolutionary indicators, such as the HNCO/C3S, SO2/C2S, and CH3SH/C2S ratios, to trace the prestellar/protostellar transition. We also derived isotopic ratios for a variety of molecules, many of which show isotopic ratios close to the values for the local interstellar medium (remarkably all those involving 34S and 33S), while there are also several isotopic anomalies like an extreme depletion in 13C for one of the two isotopologs of c-C3H2, a drastic enrichment in 18O for SO and HNCO (SO being also largely enriched in 17O), and different abundances for the two 13C substituted species of C2H and the two 15N substituted species of N2H+. We report the first detection in space of some minor isotopologs like c-C3D. The exhaustive chemical characterization of L483 presented here, together with similar studies of other prestellar and protostellar sources, should allow us to identify the main factors that regulate the chemical composition of cores along the process of formation of low-mass protostars.

scholarly journals New molecular species at redshift z = 0.89

2020 ◽  
Vol 636 ◽  
pp. L7 ◽  
Author(s):  
B. Tercero ◽  
J. Cernicharo ◽  
S. Cuadrado ◽  
P. de Vicente ◽  
M. Guélin
Keyword(s):  
Molecular Species ◽  
Rest Frame ◽  
Early Time ◽  
Line Of Sight ◽  
Extragalactic Source ◽  
The Galaxy ◽  
Line Survey ◽  
Molecular Abundances ◽  
Spiral Arm ◽  
Made In

We present the first detections of CH3SH, C3H+, C3N, HCOOH, CH2CHCN, and H2CN in an extragalactic source. Namely the spiral arm of a galaxy located at z = 0.89 on the line of sight to the radio-loud quasar PKS 1830−211. OCS, SO2, and NH2CN were also detected, raising the total number of molecular species identified in that early time galaxy to 54, not counting isotopologues. The detections were made in absorption against the SW quasar image, at 2 kpc from the galaxy centre, over the course of a Q band spectral line survey made with the Yebes 40 m telescope (rest-frame frequencies: 58.7 − 93.5 GHz). We derived the rotational temperatures and column densities of those species, which are found to be subthermally excited. The molecular abundances, and in particular the large abundances of C3H+ and of several previously reported cations, are characteristic of diffuse or translucent clouds with enhanced UV radiation or strong shocks.

scholarly journals 1.7” Resolution CO(1-0) Observations of ARP220: Nuclear Gas Ring of Merger Remnant

1994 ◽  
Vol 140 ◽  
pp. 376-378 ◽  
Author(s):  
S. K. Okumura ◽  
R. Kawabe ◽  
M. Ishiguro ◽  
S. Ishizuki
Keyword(s):  
Central Region ◽  
Emission Peak ◽  
Molecular Gas ◽  
Velocity Range ◽  
No Emission ◽  
Large Velocity ◽  
Nuclear Ring ◽  
Compact Sources ◽  
Large Velocity Gradient ◽  
Co Emission

AbstractWe made aperture synthesis CO(l-O) observations of the central region of Arp220 with the Nobeyama Millimeter Array. Central CO emission was resolved with a size of 975 kpc. It shows a ring-like structure (ɪ ~ 500 pc) with a large velocity gradient, 393 km · s−1 · kpc−1, from southwest to northeast direction. The ring-like emission is located around double radio compact sources. No emission peak was found in the center of the double sources within the velocity range 5100 km s−1to 5800 km s−1. These results suggest that an inclined massive gas ring has been or is being formed in the central 1 kpc of Arp220. Most of the molecular gas in Arp220 is concentrated on this nuclear ring. The radio compact sources are probably located at the inner egde of the ring.

scholarly journals First hot corino detected around an isolated intermediate-mass protostar: Cep E-mm

2018 ◽  
Vol 618 ◽  
pp. A145 ◽  
Author(s):  
J. Ospina-Zamudio ◽  
B. Lefloch ◽  
C. Ceccarelli ◽  
C. Kahane ◽  
C. Favre ◽  
...  
Keyword(s):  
High Velocity ◽  
Rotational Temperature ◽  
Chemical Diversity ◽  
High Mass ◽  
Continuum Emission ◽  
Spectral Signature ◽  
Broad Line ◽  
Intermediate Mass ◽  
Spectral Bands ◽  
Molecular Abundances

Context. Intermediate-mass (IM) protostars provide a bridge between the low- and high-mass protostars. Despite their relevance, little is known about their chemical diversity. Aims. We want to investigate the molecular richness towards the envelope of I-M protostars and to compare their properties with those of low- and high-mass sources. Methods. We have selected the isolated IM Class 0 protostar Cep E-mm to carry out an unbiased molecular survey with the IRAM 30 m telescope between 72 and 350 GHz with an angular resolution lying in the range 7–34″. Our goal is to obtain a census of the chemical content of the protostellar envelope. These data were complemented with NOEMA observations of the spectral bands 85.9–89.6 GHz and 216.8–220.4 GHz at angular resolutions of 2.3″ and 1.4″, respectively. Results. The 30 m spectra show bright emission of O- and N-bearing complex organic molecules (COMs): CH3OH and its rare isotopologues CH2DOH and 13CH3OH, CH3CHO, CH3OCH3, CH3COCH3, HCOOH, HCOOCH3, H2CCO, NH2CHO, CH3CN, C2H3CN, C2H5CN, HNCO and H2CO. We identify up to three components in the spectral signature of COMs: an extremely broad line (eBL) component associated with the outflowing gas (FWHM > 7kms−1), a narrow line (NL) component (FWHM < 3kms−1) associated with the cold envelope, and a broad line (BL) component (FWHM ≃ 5.5kms−1) which traces the signature of a hot corino. The eBL and NL components are detected only in molecular transitions of low excitation and dominate the emission of CH3OH. The BL component is detected in highly excited gas (Eup > 100 K). The NOEMA observations reveal Cep E-mm as a binary protostellar system, whose components, Cep E-A and Cep E-B, are separated by ≈1.7″. Cep E-A dominates the core continuum emission and powers the long-studied, well-known, high-velocity jet associated with HH377. The lower flux source Cep E-B powers another high-velocity molecular jet, reaching velocities of ≈80 km s−1, which propagates in a direction close to perpendicular with respect to the Cep E-A jet. Our interferometric maps show that the emission of COMs arises from a region of ≈0.7″ size around Cep E-A, and corresponds to the BL component detected with the IRAM 30 m telescope. On the contrary, no COM emission is detected towards Cep E-B. We have determined the rotational temperature (Trot) and the molecular gas column densities from a simple population diagram analysis or assuming a given excitation temperature. Rotational temperatures of COMs emission were found to lie in the range 20−40 K with column densities ranging from a few times 1015 cm−2 for O-bearing species, down to a few times 1014 cm−2 for N-bearing species. Molecular abundances are similar to those measured towards other low- and intermediate-mass protostars. Ketene (H2CCO) appears as an exception, as it is found significantly more abundant towards Cep E-A. High-mass hot cores are significantly less abundant in methanol and N-bearing species are more abundant by two to three orders of magnitude. Conclusions. Cep E-mm reveals itself as a binary protostellar system with a strong chemical differentiation between both cores. Only the brightest component of the binary is associated with a hot corino. Its properties are similar to those of low-mass hot corinos.

scholarly journals An ALMA and ATCA Molecular Line Survey Toward Centaurus A

2012 ◽  
Vol 8 (S292) ◽  
pp. 251-251
Author(s):  
Jürgen Ott ◽  
Mark McCoy ◽  
David Meier
Keyword(s):  
Radio Galaxy ◽  
Molecular Absorption ◽  
Physical Processes ◽  
Molecular Line ◽  
Physical Conditions ◽  
Line Survey ◽  
Molecular Abundances ◽  
Excitation Conditions ◽  
Compact Array ◽  
Centaurus A

AbstractWe present Atacama Large Millimeter/submillimeter Array (ALMA) and Australia Telescope Compact Array (ATCA) data of molecular absorption lines toward the bright central core of the prominent, nearby (d ∼ 3.8 Mpc) radio galaxy Centaurus A, at 13, 7, 3, and 1mm wavelengths. The line of sight crosses the prominent dust lane and continues through the disk and eventually through gas that may be very close to the central supermassive black hole. The goal of our survey is to determine the physical conditions of the gas via analyses of molecular line tracers including molecular abundances and excitation conditions that are sensitive to changes in temperature, density, ionization, and shocks. This study allows us to derive the physical processes that are shaping each molecular environment.

scholarly journals Effect of variation in density on the stability of superposed streams of Fluid

1931 ◽  
Vol 132 (820) ◽  
pp. 499-523 ◽  
Keyword(s):  
Density Gradient ◽  
Velocity Gradient ◽  
Horizontal Plane ◽  
Experimental Results ◽  
Large Velocity ◽  
Formed Part ◽  
The Stability ◽  
Large Velocity Gradient

1. The chief part of the work described in this paper was done in 1914 and formed part of the essay for which the Adams Prize was awarded in 1915. During the war years it was laid aside, and since then I have delayed publica­tion, hoping to be able to undertake experiments designed to verify, or otherwise, the results. Lately, however, Mr. Goldstein has told me that he is engaged on similar problems and he has encouraged me to publish the work without waiting for experimental results. It is well known that when the wind near the ground drops at night owing to the cooling of the ground, the wind at a higher level frequently remains unchanged so that the effect of a decrease in density with height is to enable a large velocity gradient to be maintained. This implies that the turbulence is suppressed or at any rate much reduced by the density gradient. To the mathematician this at once presents the problem of the stability of a fluid in which the density and velocity vary with height above the ground, regarded as a horizontal plane.

Sign in / Sign up

Export Citation Format

Share Document