scholarly journals DC3N observations towards high-mass star-forming regions

2020 ◽  
Vol 496 (2) ◽  
pp. 1990-1999 ◽  
Author(s):  
V M Rivilla ◽  
L Colzi ◽  
F Fontani ◽  
M Melosso ◽  
P Caselli ◽  
...  
Keyword(s):  
Gas Phase ◽  
Massive Star ◽  
High Mass ◽  
Kinetic Temperature ◽  
Evolutionary Stage ◽  
Mass Star ◽  
Star Forming ◽  
Dark Clouds ◽  
Star Forming Regions ◽  
First Time

ABSTRACT We present the study of deuteration of cyanoacetylene (HC3N) towards a sample of 28 high-mass star-forming cores divided into different evolutionary stages, from starless to evolved protostellar cores. We report for the first time the detection of DC3N towards 15 high-mass cores. The abundance ratios of DC3N with respect HC3N range in the interval 0.003–0.022, lower than those found in low-mas protostars and dark clouds. No significant trend with the evolutionary stage, or with the kinetic temperature of the region, has been found. We compare the level of deuteration of HC3N with those of other molecules towards the same sample, finding weak correlation with species formed only or predominantly in gas phase (N2H+ and HNC, respectively), and no correlation with species formed only or predominantly on dust grains (CH3OH and NH3, respectively). We also present a single-dish map of DC3N towards the protocluster IRAS 05358+3543, which shows that DC3N traces an extended envelope (∼0.37 pc) and peaks towards two cold condensations separated from the positions of the protostars and the dust continuum. The observations presented in this work suggest that deuteration of HC3N is produced in the gas of the cold outer parts of massive star-forming clumps, giving us an estimate of the deuteration factor prior to the formation of denser gas.

scholarly journals Nitrogen and hydrogen fractionation in high-mass star-forming cores from observations of HCN and HNC

2018 ◽  
Vol 609 ◽  
pp. A129 ◽  
Author(s):  
L. Colzi ◽  
F. Fontani ◽  
P. Caselli ◽  
C. Ceccarelli ◽  
P. Hily-Blant ◽  
...  
Keyword(s):  
Solar System ◽  
Solar Nebula ◽  
Rotational Transition ◽  
High Mass ◽  
Evolutionary Stage ◽  
Mass Star ◽  
Stellar Cluster ◽  
Star Forming ◽  
Star Forming Regions ◽  
Dense Cores

The ratio between the two stable isotopes of nitrogen, 14N and 15N, is well measured in the terrestrial atmosphere (~272), and for the pre-solar nebula (~441, deduced from the solar wind). Interestingly, some pristine solar system materials show enrichments in 15N with respect to the pre-solar nebula value. However, it is not yet clear if and how these enrichments are linked to the past chemical history because we have only a limited number of measurements in dense star-forming regions. In this respect, dense cores, which are believed to be the precursors of clusters and also contain intermediate- and high-mass stars, are important targets because the solar system was probably born within a rich stellar cluster, and such clusters are formed in high-mass star-forming regions. The number of observations in such high-mass dense cores has remained limited so far. In this work, we show the results of IRAM-30 m observations of the J = 1−0 rotational transition of the molecules HCN and HNC and their 15N-bearing counterparts towards 27 intermediate- and high-mass dense cores that are divided almost equally into three evolutionary categories: high-mass starless cores, high-mass protostellar objects, and ultra-compact Hii regions. We have also observed the DNC(2–1) rotational transition in order to search for a relation between the isotopic ratios D/H and 14N/15N. We derive average 14N/15N ratios of 359 ± 16 in HCN and of 438 ± 21 in HNC, with a dispersion of about 150–200. We find no trend of the 14N/15N ratio with evolutionary stage. This result agrees with what has been found for N2H+ and its isotopologues in the same sources, although the 14N/15N ratios from N2H+ show a higher dispersion than in HCN/HNC, and on average, their uncertainties are larger as well. Moreover, we have found no correlation between D/H and 14N/15N in HNC. These findings indicate that (1) the chemical evolution does not seem to play a role in the fractionation of nitrogen, and that (2) the fractionation of hydrogen and nitrogen in these objects is not related.

scholarly journals The millimeter-wave spectrum of methyl ketene and the astronomical search for it

2018 ◽  
Vol 619 ◽  
pp. A92 ◽  
Author(s):  
C. Bermúdez ◽  
B. Tercero ◽  
R. A. Motiyenko ◽  
L. Margulès ◽  
J. Cernicharo ◽  
...  
Keyword(s):  
Excited State ◽  
Millimeter Wave ◽  
Ground State ◽  
Wave Spectrum ◽  
High Mass ◽  
Mass Star ◽  
Rotational Spectrum ◽  
Star Forming ◽  
Dark Clouds ◽  
Star Forming Regions

Context. The analysis of isomeric species of a compound observed in the interstellar medium (ISM) is a useful tool to understand the chemistry of complex organic molecules. It could, likewise, assist in the detection of new species. Aims. Our goal consists in analyzing one of the two most stable species of the C3H4O family, methyl ketene, whose actual rotational parameters are not precise enough to allow its detection in the ISM. The obtained parameters will be used to search for it in the high-mass star-forming regions Orion KL and Sagittarius B2, as well as in the cold dark clouds TMC-1 in the Taurus Molecular Cloud and Barnard 1 (B1–b). Methods. A millimeter-wave room-temperature rotational spectrum of methyl ketene was recorded from 50 to 330 GHz. The internal rotation analysis of its ground state and first torsional excited state was performed with the rho-axis method employing the RAM36 program. Results. More than 3000 transitions of the rotational spectrum of the ground state (Kamax = 18) and first torsional excited state (Kamax = 13) of methyl ketene were fitted using a Hamiltonian that contains 41 parameters with a root mean square of 44 kHz. Column density limits were calculated but no lines were detected in the ISM belonging to methyl ketene.

scholarly journals Water Masers Toward Star-Forming Regions in the Bolocam Galactic Plane Survey

2012 ◽  
Vol 8 (S287) ◽  
pp. 286-287 ◽  
Author(s):  
Miranda K. Dunham ◽  
Keyword(s):  
Physical Properties ◽  
Galactic Plane ◽  
Dust Emission ◽  
High Mass ◽  
Evolutionary Stage ◽  
Mass Star ◽  
Star Forming ◽  
Star Forming Regions ◽  
Water Masers ◽  
Green Bank Telescope

AbstractWe present preliminary results of a search for 22 GHz water masers toward 1400 star-forming regions seen in the Bolocam Galactic Plane Survey (BGPS) using the Green Bank Telescope (GBT). The BGPS is a blind survey of the Northern Galactic plane in 1.1 mm thermal dust emission that has cataloged star-forming regions at all evolutionary stages. Further information is required to determine the stage of each BGPS source. Since water masers are produced by outflows from low and high-mass star forming regions, their presence is a key component of determining whether the BGPS sources are forming stars and which evolutionary stage they are in. We present preliminary detection statistics, basic properties of the water masers, and correlations with physical properties determined from the 1.1 mm emission and ammonia observations obtained concurrently with the water masers on the GBT.

scholarly journals VLBI multi-epoch water maser observations toward massive protostars

2012 ◽  
Vol 8 (S287) ◽  
pp. 377-385 ◽  
Author(s):  
José M. Torrelles ◽  
José F. Gómez ◽  
Nimesh A. Patel ◽  
Salvador Curiel ◽  
Guillem Anglada ◽  
...  
Keyword(s):  
Massive Star ◽  
High Mass ◽  
Mass Star ◽  
Star Forming ◽  
Star Forming Regions ◽  
Central Engine ◽  
Dynamic Scenario ◽  
Low Mass ◽  
Cepheus A ◽  
Water Maser

AbstractVLBI multi-epoch water maser observations are a powerful tool to study the gas very close to the central engine responsible for the phenomena associated with the early evolution of massive protostars. In this paper we present a summary of the main observational results obtained toward the massive star-forming regions of Cepheus A and W75N. These observations revealed unexpected phenomena in the earliest stages of evolution of massive objects (e.g., non-collimated “short-lived” pulsed ejections in different massive protostars), and provided new insights in the study of the dynamic scenario of the formation of high-mass stars (e.g., simultaneous presence of a jet and wide-angle outflow in the massive object Cep A HW2, similar to what is observed in low-mass protostars). In addition, with these observations it has been possible to identify new, previously unseen centers of high-mass star formation through outflow activity.

scholarly journals 325 GHz Water Masers in Orion Source I

2012 ◽  
Vol 8 (S287) ◽  
pp. 184-185
Author(s):  
Florian Niederhofer ◽  
Elizabeth Humphreys ◽  
Ciriaco Goddi ◽  
Lincoln J. Greenhill
Keyword(s):  
Star Formation ◽  
Massive Star ◽  
High Mass ◽  
Mass Star ◽  
Compact Disk ◽  
Volume Source ◽  
Star Forming ◽  
Star Forming Regions ◽  
Water Masers ◽  
Excitation Conditions

AbstractRadio Source I in the Orion BN/KL region provides the closest example of high mass star formation. It powers a rich ensemble of SiO and H2O masers, and is one of only three star-forming regions known to display SiO maser emission. Previous monitoring of different SiO masers with the VLBA and VLA has enabled the resolution of a compact disk and a protostellar wind at radii <100 AU from Source I, which collimates into a bipolar outflow at radii of 100-1000 AU (see contribution by Greenhill et al., this volume). Source I may provide the best case of disk-mediated accretion and outflow recollimation in massive star formation. Here, we report preliminary results of sub-arcsecond resolution 325 GHz H2O maser observations made with the SMA. We find that 325 GHz H2O masers trace a more collimated portion of the Source I outflow than masers at 22 GHz, but occur at similar radii suggesting similar excitation conditions. A velocity gradient perpendicular to the outflow axis, indicating rotation, supports magneto-centrifugal driving of the flow.

scholarly journals Rotational spectroscopic study of S-methyl thioformate

2020 ◽  
Vol 644 ◽  
pp. A102
Author(s):  
A. Jabri ◽  
B. Tercero ◽  
L. Margulès ◽  
R. A. Motiyenko ◽  
E. A. Alekseev ◽  
...  
Keyword(s):  
Excited States ◽  
Methyl Formate ◽  
Wave Spectrum ◽  
High Mass ◽  
Mass Star ◽  
Star Forming ◽  
Star Forming Regions ◽  
Global Fit ◽  
Rotation Motion ◽  
First Time

Context. S-methyl thioformate CH3SC(O)H is a monosulfur derivative of methyl formate, a relatively abundant component of the interstellar medium (ISM). S-methyl thioformate being, thermodynamically, the most stable isomer, it can be reasonably proposed for detection in the ISM. Aims. This work aims to experimentally study and theoretically analyze the ground and first torsional excited states for CH3SC(O)H in a large spectral range for astrophysical use. Methods. S-methyl thioformate was synthesized as a result of a reaction of methyl mercaptan with acetic-formic anhydride. The millimeter-wave spectrum was then recorded for the first time from 150 to 660 GHz with the solid-state spectrometer located at Lille. Results. A set of 3545 lines is determined and combined with 54 previously measured lines in the microwave region, belonging to ground state νt = 0 as well as 1391 transitions in the first excited state of torsion ν18 = 1. Some 164 lines were also assigned to ν18 = 2 for the A-species. A global fit was performed using the BELGI-Cs code taking into account the large splitting of A and E lines due to methyl internal rotation motion with a relatively low barrier, V3 = 127.4846(15) cm−1. Conclusions. Using our spectroscopy work, a deep search of S-methyl thioformate was carried out in the IRAM 30 m and ALMA data of different high-mass star-forming regions (Orion KL and Sgr B2). We derived an upper limit to the CH3SC(O)H column density in these regions.

scholarly journals Methanol masers: Evolutionary and kinematic tracers of massive star formation

2002 ◽  
Vol 206 ◽  
pp. 147-150
Author(s):  
Vincent Minier ◽  
Roy Booth ◽  
John Conway ◽  
Michele Pestalozzi
Keyword(s):  
Star Formation ◽  
Massive Star ◽  
High Mass ◽  
Mass Star ◽  
Star Forming ◽  
Methanol Maser ◽  
Star Forming Regions ◽  
Vlbi Observations ◽  
Methanol Masers ◽  
Maser Sources

We summarise our recent VLBI observations of a large sample of methanol maser sources associated with high-mass star-forming regions.

scholarly journals On the size of the CO-depletion radius in the IRDC G351.77−0.51

2019 ◽  
Vol 490 (4) ◽  
pp. 4489-4501 ◽  
Author(s):  
G Sabatini ◽  
A Giannetti ◽  
S Bovino ◽  
J Brand ◽  
S Leurini ◽  
...  
Keyword(s):  
Large Scale ◽  
Spatial Scales ◽  
High Mass ◽  
Mass Star ◽  
Number Density ◽  
Dark Cloud ◽  
Star Forming ◽  
Dark Clouds ◽  
Physical Conditions ◽  
Star Forming Regions

ABSTRACT An estimate of the degree of CO-depletion (fD) provides information on the physical conditions occurring in the innermost and densest regions of molecular clouds. A key parameter in these studies is the size of the depletion radius, i.e. the radius within which the C-bearing species, and in particular CO, are largely frozen on to dust grains. A strong depletion state (i.e. fD &gt; 10, as assumed in our models) is highly favoured in the innermost regions of dark clouds, where the temperature is &lt;20 K and the number density of molecular hydrogen exceeds a few × 104 cm−3. In this work, we estimate the size of the depleted region by studying the Infrared Dark Cloud (IRDC) G351.77−0.51. Continuum observations performed with the Herschel Space Observatory and the LArge APEX BOlometer CAmera, together with APEX C18O and C17O J = 2→1 line observations, allowed us to recover the large-scale beam- and line-of-sight-averaged depletion map of the cloud. We built a simple model to investigate the depletion in the inner regions of the clumps in the filament and the filament itself. The model suggests that the depletion radius ranges from 0.02 to 0.15 pc, comparable with the typical filament width (i.e. ∼0.1 pc). At these radii, the number density of H2 reaches values between 0.2 and 5.5 × 105 cm−3. These results provide information on the approximate spatial scales on which different chemical processes operate in high-mass star-forming regions and also suggest caution when using CO for kinematical studies in IRDCs.

Probing Early Phases of High Mass Stars with 6.7 GHz Methanol Masers

2017 ◽  
Vol 13 (S336) ◽  
pp. 323-324
Author(s):  
Sonu Tabitha Paulson ◽  
Jagadheep D. Pandian
Keyword(s):  
Star Formation ◽  
Massive Star ◽  
Dust Emission ◽  
Black Body ◽  
High Mass ◽  
Mass Star ◽  
Star Forming ◽  
Star Forming Regions ◽  
Methanol Masers ◽  
Early Phases

AbstractMethanol masers at 6.7 GHz are the brightest of class II methanol masers and have been found exclusively towards massive star forming regions. These masers can thus be used as a unique tool to probe the early phases of massive star formation. We present here the SED studies of 284 methanol masers chosen from the MMB catalogue, which falls in the Hi-GAL range (|l| ≤ 60°, |b| ≤ 1°). The masers are studied using the ATLASGAL, MIPSGAL and Hi-GAL data at wavelengths ranging from 24−870 micrometers. A single grey body component fit was used to model the cold dust emission whereas the emission from the warm dust is modelled by a black body. The clump properties such as isothermal mass, FIR luminosity and MIR luminosity were obtained using the best fit parameters of the SED fits. We discuss the physical properties of the sources and explore the evolutionary stages of the sources having 6.7 GHz maser emission in the timeline of high mass star formation.

scholarly journals Newly detected H2O Masers in Seyfert and Starburst Galaxies

2005 ◽  
Vol 13 ◽  
pp. 851-853 ◽  
Author(s):  
A. B. Peck ◽  
A. Tarchi ◽  
C. Henkel ◽  
N. M. Nagar ◽  
J. Braatz ◽  
...  
Keyword(s):  
Star Formation ◽  
Molecular Clouds ◽  
Massive Star ◽  
Chemical Properties ◽  
High Mass ◽  
Mass Star ◽  
Star Forming ◽  
Star Forming Regions ◽  
Nearby Galaxies ◽  
Maser Sources

AbstractWe report new detections of three H2O megamasers and one kilomaser using the Effelsberg 100-m telescope. Isotropic luminosities are ~50, 300, 1, and 230 L⊙ for Mrk 1066, Mrk 34, NGC 3556, and Arp 299, respectively. Mrk 34 contains the most distant H2O megamaser ever detected in a Seyfert. Our targets in this survey were chosen to fit one of the following criteria: 1) to have a high probability of interaction between the radio jet and the ISM within the central few parsecs of the radio galaxy, yielding masers which arise in local molecular clouds; or 2) to have very bright IRAS sources in which massive star forming regions might yield powerful masers. The ‘jet maser’ sources can provide detailed information about the conditions in the ISM in the central 1-10 pc of AGN. The extra-galactic ‘star formation masers’ can be used to pinpoint and characterize locations of high mass star formation in nearby galaxies. In addition, these sources will help to provide a better understanding of the chemical properties of molecular clouds in extra-galactic systems.

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