scholarly journals First detection of the carbon chain molecules 13CCC and C13CC towards SgrB2(M)

2020 ◽  
Vol 633 ◽  
pp. A120 ◽  
Author(s):  
T. F. Giesen ◽  
B. Mookerjea ◽  
G. W. Fuchs ◽  
A. A. Breier ◽  
D. Witsch ◽  
...  
Keyword(s):  
Laboratory Data ◽  
Carbon Chain ◽  
Abundance Ratio ◽  
Chain Molecule ◽  
Excitation Temperature ◽  
Science Data ◽  
Point Energy ◽  
Star Forming ◽  
Vibrational Transitions ◽  
Carbon Molecules

Context. Carbon molecules and their 13C-isotopologues can be used to determine the 12C/13C abundance ratios in stellar and interstellar objects. C3 is a pure carbon chain molecule found in star-forming regions and in stellar shells of carbon-rich late-type stars. Latest laboratory data of 13C-isotopologues of C3 allow a selective search for the mono-substituted species 13CCC and C13CC based on accurate ro-vibrational frequencies. Aims. We aim to provide the first detection of the 13C-isotopologues 13CCC and C13CC in space and to derive the 12C/13C ratio of interstellar gas in the massive star-forming region SgrB2(M) near the Galactic Center. Methods. We used the heterodyne receivers GREAT and upGREAT on board SOFIA to search for the ro-vibrational transitions Q(2) and Q(4) of 13CCC and C13CC at 1.9 THz along the line of sight towards SgrB2(M). In addition, to determine the local excitation temperature, we analyzed data from nine ro-vibrational transitions of the main isotopologue CCC in the frequency range between 1.6 and 1.9 THz, which were taken from the Herschel Science Data Archive. Results. We report the first detection of the isotopologues 13CCC and C13CC. For both species, the ro-vibrational absorption lines Q(2) and Q(4) have been identified, primarily arising from the warm gas physically associated with the strong continuum source, SgrB2(M). From the available CCC ro-vibrational transitions, we derived a gas excitation temperature of Tex = 44.4+4.7−3.9 K, and a total column density of N(CCC) = 3.88+0.39−0.35 × 1015 cm−2. Assuming the excitation temperatures of C13CC and 13CCC to be the same as for CCC, we obtained column densities of the 13C-isotopologues of N(C13CC) = 2.1+0.9−0.6 × 1014 cm−2 and N(13CCC) = 2.4+1.2−0.8 × 1014 cm−2. The derived 12C/13C abundance ratio in the C3 molecules is 20.5 ± 4.2, which is in agreement with the elemental ratio of 20, typically observed in SgrB2(M). However, we find the N(13CCC)/N(C13CC) ratio to be 1.2 ± 0.1, which is shifted from the statistically expected value of two. We propose that the discrepant abundance ratio arises due to the lower zero-point energy of C13CC, which makes position-exchange reaction converting 13CCC to C13CC energetically favorable.

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 Mapping the 13CO/C18O abundance ratio in the massive star-forming region G29.96−0.02

2018 ◽  
Vol 617 ◽  
pp. A14 ◽  
Author(s):  
S. Paron ◽  
M. B. Areal ◽  
M. E. Ortega
Keyword(s):  
Molecular Clouds ◽  
Abundance Ratio ◽  
High Mass ◽  
Local Thermal Equilibrium ◽  
Mass Star ◽  
Galactocentric Distance ◽  
Star Forming ◽  
Physical Conditions ◽  
The Galaxy ◽  
Molecular Abundances

Aims. Estimating molecular abundances ratios from directly measuring the emission of the molecules toward a variety of interstellar environments is indeed very useful to advance our understanding of the chemical evolution of the Galaxy, and hence of the physical processes related to the chemistry. It is necessary to increase the sample of molecular clouds, located at different distances, in which the behavior of molecular abundance ratios, such as the 13CO/C18O ratio, is studied in detail. Methods. We selected the well-studied high-mass star-forming region G29.96−0.02, located at a distance of about 6.2 kpc, which is an ideal laboratory to perform this type of study. To study the 13CO/C18O abundance ratio (X13∕18) toward this region, we used 12CO J = 3–2 data obtained from the CO High-Resolution Survey, 13CO and C18O J = 3–2 data from the 13CO/C18O (J = 3–2) Heterodyne Inner Milky Way Plane Survey, and 13CO and C18O J = 2–1 data retrieved from the CDS database that were observed with the IRAM 30 m telescope. The distribution of column densities and X13∕18 throughout the extension of the analyzed molecular cloud was studied based on local thermal equilibrium (LTE) and non-LTE methods. Results. Values of X13∕18 between 1.5 and 10.5, with an average of about 5, were found throughout the studied region, showing that in addition to the dependency of X13∕18 and the galactocentric distance, the local physical conditions may strongly affect this abundance ratio. We found that correlating the X13∕18 map with the location of the ionized gas and dark clouds allows us to suggest in which regions the far-UV radiation stalls in dense gaseous components, and in which regions it escapes and selectively photodissociates the C18O isotope. The non-LTE analysis shows that the molecular gas has very different physical conditions, not only spatially throughout the cloud, but also along the line of sight. This type of study may represent a tool for indirectly estimating (from molecular line observations) the degree of photodissociation in molecular clouds, which is indeed useful to study the chemistry in the interstellar medium.

scholarly journals IRAM and Gaia views of multi-episodic star formation in IC 1396A

2019 ◽  
Vol 622 ◽  
pp. A118 ◽  
Author(s):  
Aurora Sicilia-Aguilar ◽  
Nimesh Patel ◽  
Min Fang ◽  
Veronica Roccatagliata ◽  
Konstantin Getman ◽  
...  
Keyword(s):  
Star Formation ◽  
Column Density ◽  
Velocity Structure ◽  
Initial Conditions ◽  
Carbon Chain ◽  
Star Formation History ◽  
Evolutionary Stage ◽  
Star Forming ◽  
History Of ◽  
Continuum Data

Context. IC 1396A is a cometary globule that contains the Class 0 source IC 1396A-PACS-1, which was discovered with Herschel. Aims. We use IRAM 30m telescope and Gaia DR2 data to explore the star formation history of IC 1396A and investigate the possibilities of triggered star formation. Methods. IRAM and Herschel continuum data were used to obtain dust temperature and column density maps. Heterodyne data reveal the velocity structure of the gas. Gaia DR2 proper motions for the stars complete the kinematics of the region. Results. IC 1396A-PACS-1 presents molecular emission similar to a hot corino with warm carbon chain chemistry due to the UV irradiation. The source is embedded in a dense clump surrounded by gas at velocities that are significantly different from the velocities of the Tr 37 cluster. CN emission reveals photoevaporation, while continuum data and high-density tracers (C18O, HCO+, DCO+, and N2D+) reveal distinct gaseous structures with a range of densities and masses. Conclusions. By combining the velocity, column density, and temperature information and Gaia DR2 kinematics, we confirm that the globule has experienced various episodes of star formation. IC 1396A-PACS-1 is probably the last intermediate-mass protostar that will form within IC 1396A; it shows evidence of being triggered by radiation-driven implosion. Chemical signatures such as CCS place IC 1396A-PACS-1 among the youngest known protostars. Gaia DR2 data reveal velocities in the plane of the sky ~4 km s−1 for IC 1396A with respect to Tr 37. The total velocity difference (8 km s−1) between the Tr 37 cluster and IC 1396A is too small for IC 1396A to have undergone substantial rocket acceleration, which imposes constraints on the distance to the ionizing source in time and the possibilities of triggered star formation. The three stellar populations in the globule reveal that objects located within relatively close distances (<0.5 pc) can be formed in various star-forming episodes within ~1–2 Myr. Once the remaining cloud disperses, we expect substantial differences in evolutionary stage and initial conditions for the resulting objects and their protoplanetary disks, which may affect their evolution. Finally, evidence for short-range feedback from the embedded protostars, and in particular, the A-type star V390 Cep, is also observed.

Detection of a new carbon-chain molecule, CCO

1991 ◽  
Vol 380 ◽  
pp. L39 ◽  
Author(s):  
Masatoshi Ohishi ◽  
Shin-Ichi Ishikawa ◽  
Chikashi Yamada ◽  
Hideto Kanamori ◽  
William M. Irvine ◽  
...  
Keyword(s):  
Carbon Chain ◽  
Chain Molecule

scholarly journals First detection of [13C II] in the Large Magellanic Cloud

2019 ◽  
Vol 631 ◽  
pp. L12 ◽  
Author(s):  
Yoko Okada ◽  
Ronan Higgins ◽  
Volker Ossenkopf-Okada ◽  
Cristian Guevara ◽  
Jürgen Stutzki ◽  
...  
Keyword(s):  
Optical Depth ◽  
Line Profile ◽  
Large Magellanic Cloud ◽  
Abundance Ratio ◽  
Magellanic Cloud ◽  
Star Forming ◽  
Star Forming Regions ◽  
Distant Galaxies ◽  
Nearby Galaxies ◽  
Galactic Sources

Context. [13C II] observations in several Galactic sources show that the fine-structure [12C II] emission is often optically thick (the optical depths around 1 to a few). Aims. Our goal was to test whether this also affects the [12C II] emission from nearby galaxies like the Large Magellanic Cloud (LMC). Methods. We observed three star-forming regions in the LMC with upGREAT on board SOFIA at the frequency of the [C II] line. The 4 GHz bandwidth covers all three hyperfine lines of [13C II] simultaneously. For the analysis, we combined the [13C II] F = 1−0 and F = 1−1 hyperfine components as they do not overlap with the [12C II] line in velocity. Results. Three positions in N159 and N160 show an enhancement of [13C II] compared to the abundance-ratio-scaled [12C II] profile. This is likely due to the [12C II] line being optically thick, supported by the fact that the [13C II] line profile is narrower than [12C II], the enhancement varies with velocity, and the peak velocity of [13C II] matches the [O I] 63 μm self-absorption. The [12C II] line profile is broader than expected from a simple optical depth broadening of the [13C II] line, supporting the scenario of several PDR components in one beam having varying [12C II] optical depths. The derived [12C II] optical depth at three positions (beam size of 14″, corresponding to 3.4 pc) is 1−3, which is similar to values observed in several Galactic sources shown in previous studies. If this also applies to distant galaxies, the [C II] intensity will be underestimated by a factor of approximately 2.

scholarly journals Theoretical Prediction of Thermophysical Properties of Waste Beef Tallow Biodiesel

2020 ◽  
Author(s):  
Gokul Raghavendra Srinivasan ◽  
Ranjitha Jambulingam
Keyword(s):  
Molecular Weight ◽  
Beef Tallow ◽  
Linear Equations ◽  
Carbon Chain ◽  
Carbon Chain Length ◽  
Independent Variables ◽  
Degree Of Unsaturation ◽  
Carbon Molecules ◽  
Thermo Physical Properties ◽  
Two Independent Variables

In this present study, simple linear equations were developed for predicting the thermo-physical properties of beef tallow biodiesel by considering their molecular weight and number of double bonds as two independent variables. Interestingly, molecular weight signifies as a function of carbon chain length and number of carbon molecules in it whereas numbers of double bond signifies the degree of unsaturation.

scholarly journals Theoretical Prediction of Thermophysical Properties of Waste Beef Tallow Biodiesel

2020 ◽  
Author(s):  
Gokul Raghavendra Srinivasan ◽  
Ranjitha Jambulingam
Keyword(s):  
Molecular Weight ◽  
Beef Tallow ◽  
Linear Equations ◽  
Carbon Chain ◽  
Carbon Chain Length ◽  
Independent Variables ◽  
Degree Of Unsaturation ◽  
Carbon Molecules ◽  
Thermo Physical Properties ◽  
Two Independent Variables

In this present study, simple linear equations were developed for predicting the thermo-physical properties of beef tallow biodiesel by considering their molecular weight and number of double bonds as two independent variables. Interestingly, molecular weight signifies as a function of carbon chain length and number of carbon molecules in it whereas numbers of double bond signifies the degree of unsaturation.

scholarly journals The ALMA-PILS survey: propyne (CH3CCH) in IRAS 16293–2422

2019 ◽  
Vol 631 ◽  
pp. A137 ◽  
Author(s):  
H. Calcutt ◽  
E. R. Willis ◽  
J. K. Jørgensen ◽  
P. Bjerkeli ◽  
N. F. W. Ligterink ◽  
...  
Keyword(s):  
Gas Phase ◽  
Spatial Scales ◽  
Excitation Temperature ◽  
Gas Phase Reactions ◽  
Star Forming ◽  
Physical Conditions ◽  
Star Forming Regions ◽  
Chemical Modelling ◽  
Low Mass ◽  
Grain Surface

Context. Propyne (CH3CCH), also known as methyl acetylene, has been detected in a variety of environments, from Galactic star-forming regions to extragalactic sources. These molecules are excellent tracers of the physical conditions in star-forming regions, allowing the temperature and density conditions surrounding a forming star to be determined. Aims. This study explores the emission of CH3CCH in the low-mass protostellar binary, IRAS 16293–2422, and examines the spatial scales traced by this molecule, as well as its formation and destruction pathways. Methods. Atacama Large Millimeter/submillimeter Array (ALMA) observations from the Protostellar Interferometric Line Survey (PILS) were used to determine the abundances and excitation temperatures of CH3CCH towards both protostars. This data allows us to explore spatial scales from 70 to 2400 au. This data is also compared with the three-phase chemical kinetics model MAGICKAL, to explore the chemical reactions of this molecule. Results. CH3CCH is detected towards both IRAS 16293A and IRAS 16293B, and is found the hot corino components, one around each source, in the PILS dataset. Eighteen transitions above 3σ are detected, enabling robust excitation temperatures and column densities to be determined in each source. In IRAS 16293A, an excitation temperature of 90 K and a column density of 7.8 × 1015 cm−2 best fits the spectra. In IRAS 16293B, an excitation temperature of 100 K and 6.8 × 1015 cm−2 best fits the spectra. The chemical modelling finds that in order to reproduce the observed abundances, both gas-phase and grain-surface reactions are needed. The gas-phase reactions are particularly sensitive to the temperature at which CH4 desorbs from the grains. Conclusions. CH3CCH is a molecule whose brightness and abundance in many different regions can be utilised to provide a benchmark of molecular variation with the physical properties of star-forming regions. It is essential when making such comparisons, that the abundances are determined with a good understanding of the spatial scale of the emitting region, to ensure that accurate abundances are derived.

scholarly journals Applications of Machine Learning Algorithms in Processing Terahertz Spectroscopic Data

2020 ◽  
Vol 09 (03) ◽  
pp. 2050011
Author(s):  
Young Min Seo ◽  
Paul F. Goldsmith ◽  
Volker Tolls ◽  
Russell Shipman ◽  
Craig Kulesa ◽  
...  
Keyword(s):  
Data Reduction ◽  
Galactic Plane ◽  
Machine Learning Algorithms ◽  
Least Square ◽  
Gaussian Kernel ◽  
Science Data ◽  
Star Forming ◽  
Star Forming Regions ◽  
Level 1 ◽  
Level 2

We present the data reduction software and the distribution of Level 1 and Level 2 products of the Stratospheric Terahertz Observatory 2 (STO2). STO2, a balloon-borne Terahertz telescope, surveyed star-forming regions and the Galactic plane and produced approximately 300,000 spectra. The data are largely similar to spectra typically produced by single-dish radio telescopes. However, a fraction of the data contained rapidly varying fringe/baseline features and drift noise, which could not be adequately corrected using conventional data reduction software. To process the entire science data of the STO2 mission, we have adopted a new method to find proper off-source spectra to reduce large amplitude fringes and new algorithms including Asymmetric Least Square (ALS), Independent Component Analysis (ICA), and Density-based spatial clustering of applications with noise (DBSCAN). The STO2 data reduction software efficiently reduced the amplitude of fringes from a few hundred to 10[Formula: see text]K and resulted in baselines of amplitude down to a few K. The Level 1 products typically have noise of a few K in [CII] spectra and [Formula: see text]1[Formula: see text]K in [NII] spectra. Using a regridding algorithm, we made spectral maps of star-forming regions and the Galactic plane survey using an algorithm employing a Bessel–Gaussian kernel. The level 1 and level 2 products are available to the astronomical community through the STO2 data server and the DataVerse. The software is also accessible to the public through Github. The detailed addresses are given in Sec.  4 of this paper on data distribution.

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