scholarly journals An unbiased spectral line survey observation toward the low-mass star-forming region L1527

2019 ◽  
Vol 71 (Supplement_1) ◽  
Author(s):  
Kento Yoshida ◽  
Nami Sakai ◽  
Yuri Nishimura ◽  
Tomoya Tokudome ◽  
Yoshimasa Watanabe ◽  
...  
Keyword(s):  
Spectral Line ◽  
Carbon Chain ◽  
Mass Star ◽  
Star Forming ◽  
Organic Species ◽  
Good Template ◽  
Solar Type ◽  
Low Mass ◽  
Line Survey ◽  
Supplementary Observation

Abstract An unbiased spectral line survey toward a solar-type Class 0/I protostar, IRAS 04368+2557, in L1527 has been carried out in the 3 mm band with the Nobeyama 45 m telescope. L1527 is known as a warm carbon-chain chemistry (WCCC) source, which harbors abundant unsaturated organic species such as CnH (n = 3, 4, 5, …) in a warm and dense region near the protostar. The observation covers the frequency range from 80 to 116 GHz. A supplementary observation has also been conducted in the 70 GHz band to observe fundamental transitions of deuterated species. In total, 69 molecular species are identified, among which 27 species are carbon-chain species and their isomers, including their minor isotopologues. This spectral line survey provides us with a good template of the chemical composition of the WCCC source.

scholarly journals Deuterated methyl mercaptan (CH3SD): Laboratory rotational spectroscopy and search toward IRAS 16293–2422 B

2019 ◽  
Vol 621 ◽  
pp. A114 ◽  
Author(s):  
Olena Zakharenko ◽  
Frank Lewen ◽  
Vadim V. Ilyushin ◽  
Maria N. Drozdovskaya ◽  
Jes K. Jørgensen ◽  
...  
Keyword(s):  
Rotational Spectroscopy ◽  
Mass Star ◽  
Methyl Mercaptan ◽  
Rotational Spectrum ◽  
Star Forming ◽  
Star Forming Regions ◽  
Millimeter Wavelengths ◽  
Low Mass ◽  
Line Survey ◽  
Telescope Arrays

Methyl mercaptan (also known as methanethiol), CH3SH, has been found in the warm and dense parts of high- as well as low- mass star-forming regions. The aim of the present study is to obtain accurate spectroscopic parameters of the S-deuterated methyl mercaptan CH3SD to facilitate astronomical observations by radio telescope arrays at (sub)millimeter wavelengths. We have measured the rotational spectrum associated with the large-amplitude internal rotation of the methyl group of methyl mercaptan using an isotopically enriched sample in the 150−510 GHz frequency range using the Köln millimeter wave spectrometer. The analysis of the spectra has been performed up to the second excited torsional state. We present modeling results of these data with the RAM36 program. CH3SD was searched for, but not detected, in data from the Atacama Large Millimeter/submillimeter Array (ALMA) Protostellar Interferometric Line Survey (PILS) of the deeply embedded protostar IRAS 16293−2422. The derived upper limit corresponds to a degree of deuteration of at most ∼18%.

scholarly journals Astrophysical detections and databases for the mono deuterated species of acetaldehyde CH2DCOH and CH3COD

2019 ◽  
Vol 624 ◽  
pp. A70 ◽  
Author(s):  
L. H. Coudert ◽  
L. Margulès ◽  
C. Vastel ◽  
R. Motiyenko ◽  
E. Caux ◽  
...  
Keyword(s):  
Abundance Ratio ◽  
Spectroscopic Constants ◽  
Mass Star ◽  
Star Forming ◽  
Star Forming Regions ◽  
Complex Organic Molecule ◽  
Low Mass ◽  
Line Survey ◽  
Complex Organic ◽  
Measured Transition

Context. Detection of deuterated species may provide information on the evolving chemistry in the earliest phases of star-forming regions. For molecules with two isomeric forms of the same isotopic variant, gas-phase and solid-state formation pathways can be differentiated using their abundance ratio. Aims. Spectroscopic databases for astrophysical purposes are built for the two mono deuterated isomeric species CH2DCOH and CH3COD of the complex organic molecule acetaldehyde. These databases can be used to search and detect these two species in astrophysical surveys, retrieving their column density and therefore abundances. Methods. Submillimeter wave and terahertz transitions were measured for mono deuterated acetaldehyde CH2DCOH which is a non-rigid species displaying internal rotation of its asymmetrical CH2D methyl group. An analysis of a dataset consisting of previously measured microwave data and the newly measured transition was carried out with a model accounting for the large amplitude torsion. Results. The frequencies of 2556 transitions are reproduced with a unitless standard deviation of 2.3 yielding various spectroscopic constants. Spectroscopic databases for astrophysical purposes were built for CH2DCOH using the results of the present analysis and for CH3COD using the results of a previous spectroscopic investigation. These two species were both searched for and are detected toward a low-mass star-forming region. Conclusions. We report the first detection of CH2DCOH (93 transitions) and the detection of CH3COD (43 transitions) species in source B of the IRAS 16293−2422 young stellar binary system located in the ρ Ophiuchus cloud region, using the publicly available ALMA Protostellar Interferometric Line Survey.

scholarly journals Processed and Unprocessed Ices in Circumstellar Disks

2005 ◽  
Vol 13 ◽  
pp. 479-481
Author(s):  
Klaus Pontoppidan ◽  
Ewine van Dishoeck ◽  
Emmanuel Dartois ◽  
Wing-Fai Thi
Keyword(s):  
Circumstellar Disks ◽  
High Mass ◽  
Formation Mechanisms ◽  
Mass Star ◽  
Low Mass Stars ◽  
Star Forming ◽  
Star Forming Regions ◽  
Solar Type ◽  
Low Mass ◽  
Circumstellar Environments

AbstractWe present 3-5 µm VLT-ISAAC spectroscopy showing the presence of methanol ices in edge-on disks of young embedded stars. Examples include the disks of L1489 IRS in Taurus and CRBR 2422.8-3423 in Ophiuchus, the last of which has the highest column density of solid CO known toward a YSO. Several additional low-mass sources in the Serpens and Chameleon molecular clouds exhibit abundant solid methanol although it is not clear if the ice is associated with a disk or with the envelope. These are the first detections of solid methanol in the disks and circumstellar environments of embedded young low-mass stars providing evidence that complex molecular species previously observed only in the solid state toward high-mass star forming regions are also present near solar-type young stars. The constraints on the formation mechanisms of methanol and the chemical evolution of ices as the material is incorporated into circumstellar disks are discussed.

Peculiar Carbon-Chain Chemistry in Low-Mass Star Forming Regions

2011 ◽  
Vol 52 ◽  
pp. 235-238 ◽  
Author(s):  
N. Sakai ◽  
T. Sakai ◽  
T. Hirota ◽  
S. Yamamoto
Keyword(s):  
Carbon Chain ◽  
Mass Star ◽  
Star Forming ◽  
Star Forming Regions ◽  
Low Mass

scholarly journals Observations of Complex Molecules in Low-Mass Protostars

2011 ◽  
Vol 7 (S280) ◽  
pp. 43-52 ◽  
Author(s):  
Nami Sakai ◽  
Satoshi Yamamoto
Keyword(s):  
Organic Molecules ◽  
Carbon Chain ◽  
Chemical Diversity ◽  
Chemical Compositions ◽  
Evolutionary Stage ◽  
Mass Star ◽  
Star Forming ◽  
Key Factor ◽  
Low Mass ◽  
Complex Organic

AbstractLow-mass star forming regions are rich inventories of complex organic molecules. Furthermore, they show significant chemical diversity even among sources in a similar physical evolutionary stage (i.e. Class 0 sources). One distinct case is the hot corino chemistry characterized by rich existence of saturated complex organic molecules such as HCOOCH3 and C2H5CN, whereas the other is the warm carbon-chain chemistry (WCCC) characterized by extraordinary richness of unsaturated complex organic molecules such as carbon-chain molecules. We here summarize these observational achievements during the last decade, and present a unified picture of carbon chemistry in low-mass protostellar cores. The chemical diversity most likely originates from the source-to-source difference in chemical compositions of grain mantles. In particular, the gas-phase abundance of CH4 evaporated from grain mantles is thought to be a key factor for appearance of WCCC. The origin of the diversity and its evolution to protopranetary disks are discussed.

scholarly journals C2O and C3O in low-mass star-forming regions

2019 ◽  
Vol 628 ◽  
pp. A72 ◽  
Author(s):  
R. G. Urso ◽  
M. E. Palumbo ◽  
C. Ceccarelli ◽  
N. Balucani ◽  
S. Bottinelli ◽  
...  
Keyword(s):  
Gas Phase ◽  
Laboratory Experiments ◽  
Solid Phase ◽  
Carbon Chain ◽  
Phase Model ◽  
Mass Star ◽  
Gas Phase Reactions ◽  
Star Forming ◽  
Star Forming Regions ◽  
Low Mass

Context. C2O and C3O belong to the carbon chain oxides family. Both molecules have been detected in the gas phase towards several star-forming regions, and to explain the observed abundances, ion-molecule gas-phase reactions have been invoked. On the other hand, laboratory experiments have shown that carbon chain oxides are formed after energetic processing of CO-rich solid mixtures. Therefore, it has been proposed that they are formed in the solid phase in dense molecular clouds after cosmic ion irradiation of CO-rich icy grain mantles and released in the gas phase after their desorption. Aims. In this work, we contribute to the understanding of the role of both gas-phase reactions and energetic processing in the formation of simple carbon chain oxides that have been searched for in various low-mass star-forming regions. Methods. We present observations obtained with the Noto-32m and IRAM-30 m telescopes towards star-forming regions. We compare these with the results of a gas-phase model that simulates C2O and C3O formation and destruction, and laboratory experiments in which both molecules are produced after energetic processing (with 200 keV protons) of icy grain mantle analogues. Results. New detections of both molecules towards L1544, L1498, and Elias 18 are reported. The adopted gas phase model is not able to reproduce the observed C2O/C3O ratios, while laboratory experiments show that the ion bombardment of CO-rich mixtures produces C2O/C3O ratios that agree with the observed values. Conclusions. Based on the results obtained here, we conclude that the synthesis of both species is due to the energetic processing of CO-rich icy grain mantles. Their subsequent desorption because of non-thermal processes allows the detection in the gas-phase of young star-forming regions. In more evolved objects, the non-detection of both C2O and C3O is due to their fast destruction in the warm gas.

scholarly journals Carbon-chain molecule survey toward four low-mass molecular outflow sources

2021 ◽  
Vol 648 ◽  
pp. A83
Author(s):  
C. Zhang ◽  
Y. Wu ◽  
X.-C. Liu ◽  
Mengyao Tang ◽  
Di Li ◽  
...  
Keyword(s):  
Radio Telescope ◽  
Detection Rate ◽  
Carbon Chain ◽  
Chain Molecule ◽  
Mass Star ◽  
Star Forming ◽  
Molecular Outflow ◽  
Mass Outflow ◽  
Low Mass ◽  
Marginal Detection

We performed a carbon-chain molecule (CCM) survey toward four low-mass outflow sources, IRAS 04181+2655 (I04181), HH211, L1524, and L1598, using the 13.7 m telescope at the Purple Mountain Observatory (PMO) and the 65 m Tian Ma Radio telescope at the Shanghai Observatory. We observed the following hydrocarbons (C2H, C4H, c–C3H2), HC2n+1N (n = 1, 2), CnS (n = 2, 3), and SO, HNC, N2H+. Hydrocarbons and HC3N were detected in all the sources, except for L1598, which had a marginal detection of C4H and a non-detection of HC3N (J = 2–1). HC5N and CCCS were only detected in I04181 and L1524, whereas SO was only detected in HH211. L1598 exhibits the lowest detection rate of CCMs and is generally regarded to be lacking in CCMs source. The ratio of N(HC3N/N(N2H+)) increases with evolution in low-mass star-forming cores. I04181 and L1524 are carbon-chain-rich star-forming cores that may possibly be characterized by warm carbon-chain chemistry. In I04181 and L1524, the abundant CCCS can be explained by shocked carbon-chain chemistry. In HH211, the abundant SO suggests that SO is formed by sublimated S+. In this study, we also mapped HNC, C4H, c–C3H2, and HC3N with data from the PMO. We also find that HNC and NH3 are concentrated in L1524S and L1524N, respectively. Furthermore, we discuss the chemical differences between I04181SE and I04181W. The co-evolution between linear hydrocarbon and cyanopolyynes can be seen in I04181SE.

scholarly journals A CATALOG OF LOW-MASS STAR-FORMING CORES OBSERVED WITH SHARC-II AT 350μm

2016 ◽  
Vol 152 (2) ◽  
pp. 36 ◽  
Author(s):  
Akshaya Suresh ◽  
Michael M. Dunham ◽  
Héctor G. Arce ◽  
Neal J. Evans II ◽  
Tyler L. Bourke ◽  
...  
Keyword(s):  
Mass Star ◽  
Star Forming ◽  
Low Mass

scholarly journals ATLASGAL – Ammonia observations towards the southern Galactic plane

2018 ◽  
Vol 609 ◽  
pp. A125 ◽  
Author(s):  
M. Wienen ◽  
F. Wyrowski ◽  
K. M. Menten ◽  
J. S. Urquhart ◽  
C. M. Walmsley ◽  
...  
Keyword(s):  
Standard Deviation ◽  
Hyperfine Structure ◽  
Optical Depth ◽  
Line Width ◽  
Rotational Temperature ◽  
High Mass ◽  
Mass Star ◽  
Star Forming ◽  
Star Forming Regions ◽  
Low Mass

Context. The initial conditions of molecular clumps in which high-mass stars form are poorly understood. In particular, a more detailed study of the earliest evolutionary phases is needed. The APEX Telescope Large Area Survey of the whole inner Galactic disk at 870 μm, ATLASGAL, has therefore been conducted to discover high-mass star-forming regions at different evolutionary phases. Aims. We derive properties such as velocities, rotational temperatures, column densities, and abundances of a large sample of southern ATLASGAL clumps in the fourth quadrant. Methods. Using the Parkes telescope, we observed the NH3 (1, 1) to (3, 3) inversion transitions towards 354 dust clumps detected by ATLASGAL within a Galactic longitude range between 300° and 359° and a latitude within ± 1.5°. For a subsample of 289 sources, the N2H+ (1–0) line was measured with the Mopra telescope. Results. We measured a median NH3 (1, 1) line width of ~ 2 km s-1, rotational temperatures from 12 to 28 K with a mean of 18 K, and source-averaged NH3 abundances from 1.6 × 10-6 to 10-8. For a subsample with detected NH3 (2, 2) hyperfine components, we found that the commonly used method to compute the (2, 2) optical depth from the (1, 1) optical depth and the (2, 2) to (1, 1) main beam brightness temperature ratio leads to an underestimation of the rotational temperature and column density. A larger median virial parameter of ~ 1 is determined using the broader N2H+ line width than is estimated from the NH3 line width of ~ 0.5 with a general trend of a decreasing virial parameter with increasing gas mass. We obtain a rising NH3 (1, 1)/N2H+ line-width ratio with increasing rotational temperature. Conclusions. A comparison of NH3 line parameters of ATLASGAL clumps to cores in nearby molecular clouds reveals smaller velocity dispersions in low-mass than high-mass star-forming regions and a warmer surrounding of ATLASGAL clumps than the surrounding of low-mass cores. The NH3 (1, 1) inversion transition of 49% of the sources shows hyperfine structure anomalies. The intensity ratio of the outer hyperfine structure lines with a median of 1.27 ± 0.03 and a standard deviation of 0.45 is significantly higher than 1, while the intensity ratios of the inner satellites with a median of 0.9 ± 0.02 and standard deviation of 0.3 and the sum of the inner and outer hyperfine components with a median of 1.06 ± 0.02 and standard deviation of 0.37 are closer to 1.

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