THE PRECISE RADIO OBSERVATION OF THE 13C ISOTOPIC FRACTIONATION FOR CARBON CHAIN MOLECULE HC3N IN THE LOW-MASS STAR FORMING REGION L1527

2016 ◽  
Author(s):  
Mitsunori Araki ◽  
Koichi Tsukiyama ◽  
Nobuhiko Kuze ◽  
Takahiro Oyama ◽  
Satoshi Yamamoto ◽  
...  
Keyword(s):  
Isotopic Fractionation ◽  
Radio Observation ◽  
Carbon Chain ◽  
Chain Molecule ◽  
Mass Star ◽  
Star Forming ◽  
Low Mass

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 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.

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 Isotopic fractionation in interstellar molecules

2017 ◽  
Vol 13 (S332) ◽  
pp. 163-174 ◽  
Author(s):  
Kenji Furuya
Keyword(s):  
Isotopic Exchange ◽  
Isotopic Fractionation ◽  
Mass Star ◽  
Exchange Reactions ◽  
Interstellar Molecules ◽  
Star Forming ◽  
Chemical Tracers ◽  
Star Forming Regions ◽  
Prestellar Cores ◽  
Low Mass

AbstractThe level of isotopic fractionation in molecules provides insights into their formation environments and how they formed. In this article, we review hydrogen and nitrogen isotopic fractionation in low-mass star-forming regions. Interstellar molecules are significantly enriched in deuterium. The importance of the nuclear spin states of light species on deuterium fractionation and the usefulness of singly and doubly deuterated molecules as chemical tracers are discussed. Observations have revealed that molecules in prestellar cores are enriched in or depleted in15N depending on molecules. Compared with deuterium fractionation chemistry, our understanding of15N fractionation chemistry is not well established. We briefly discuss potential15N fractionation routes, i.e., isotopic-exchange reactions and isotopic selective photodissociation of N2. In addition, the selective freeze-out of15N atoms onto dust grains around the transition between N atoms and N2is discussed as a potential mechanism that causes the depletion of15N in the gas phase.

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.

scholarly journals Submillimeter Array Observations of Magnetic Fields in Star Forming Regions

2010 ◽  
Vol 6 (S270) ◽  
pp. 103-106
Author(s):  
R. Rao ◽  
J.-M. Girart ◽  
D. P. Marrone
Keyword(s):  
Magnetic Field ◽  
Star Formation ◽  
Magnetic Fields ◽  
Computational Models ◽  
Dominant Role ◽  
Theoretical Models ◽  
Mass Star ◽  
Star Forming ◽  
Star Forming Regions ◽  
Low Mass

AbstractThere have been a number of theoretical and computational models which state that magnetic fields play an important role in the process of star formation. Competing theories instead postulate that it is turbulence which is dominant and magnetic fields are weak. The recent installation of a polarimetry system at the Submillimeter Array (SMA) has enabled us to conduct observations that could potentially distinguish between the two theories. Some of the nearby low mass star forming regions show hour-glass shaped magnetic field structures that are consistent with theoretical models in which the magnetic field plays a dominant role. However, there are other similar regions where no significant polarization is detected. Future polarimetry observations made by the Submillimeter Array should be able to increase the sample of observed regions. These measurements will allow us to address observationally the important question of the role of magnetic fields and/or turbulence in the process of star formation.

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