scholarly journals Sub-mm∕mm studies of the molecular gas in the Galactic disk; the TeV gamma ray SNR RXJ1713.7-3946 and the W28 high mass star forming region

2008 ◽  
Author(s):  
Yasuo Fukui ◽  
Felix A. Aharonian ◽  
Werner Hofmann ◽  
Frank Rieger ◽  
Keyword(s):  
Gamma Ray ◽  
Galactic Disk ◽  
High Mass ◽  
Molecular Gas ◽  
Mass Star ◽  
Star Forming

scholarly journals Unveiling the chemistry of interstellar CH

2018 ◽  
Vol 612 ◽  
pp. A37 ◽  
Author(s):  
H. Wiesemeyer ◽  
R. Güsten ◽  
K.M. Menten ◽  
C.A. Durán ◽  
T. Csengeri ◽  
...  
Keyword(s):  
Ground State ◽  
Far Infrared ◽  
High Resolution Spectroscopy ◽  
High Mass ◽  
Molecular Gas ◽  
Mass Star ◽  
Star Forming ◽  
Star Forming Regions ◽  
Enhanced Production ◽  
Global Correlation

Context. The methylidyne radical CH is commonly used as a proxy for molecular hydrogen in the cold, neutral phase of the interstellar medium. The optical spectroscopy of CH is limited by interstellar extinction, whereas far-infrared observations provide an integral view through the Galaxy. While the HF ground state absorption, another H2 proxy in diffuse gas, frequently suffers from saturation, CH remains transparent both in spiral-arm crossings and high-mass star forming regions, turning this light hydride into a universal surrogate for H2. However, in slow shocks and in regions dissipating turbulence its abundance is expected to be enhanced by an endothermic production path, and the idea of a “canonical” CH abundance needs to be addressed. Aim. The N = 2 ← 1 ground state transition of CH at λ149 μm has become accessible to high-resolution spectroscopy thanks to the German Receiver for Astronomy at Terahertz Frequencies (GREAT) aboard the Stratospheric Observatory for Infrared Astronomy (SOFIA). Its unsaturated absorption and the absence of emission from the star forming regions makes it an ideal candidate for the determination of column densities with a minimum of assumptions. Here we present an analysis of four sightlines towards distant Galactic star forming regions, whose hot cores emit a strong far-infrared dust continuum serving as background signal. Moreover, if combined with the sub-millimeter line of CH at λ560 μm , environments forming massive stars can be analyzed. For this we present a case study on the “proto-Trapezium” cluster W3 IRS5. Methods. While we confirm the global correlation between the column densities of HF and those of CH, both in arm and interarm regions, clear signposts of an over-abundance of CH are observed towards lower densities. However, a significant correlation between the column densities of CH and HF remains. A characterization of the hot cores in the W3 IRS5 proto-cluster and its envelope demonstrates that the sub-millimeter/far-infrared lines of CH reliably trace not only diffuse but also dense, molecular gas. Results. In diffuse gas, at lower densities a quiescent ion-neutral chemistry alone cannot account for the observed abundance of CH. Unlike the production of HF, for CH+ and CH, vortices forming in turbulent, diffuse gas may be the setting for an enhanced production path. However, CH remains a valuable tracer for molecular gas in environments reaching from diffuse clouds to sites of high-mass star formation.

scholarly journals Molecular tracers of radiative feedback in Orion (OMC-1)

2019 ◽  
Vol 622 ◽  
pp. A91 ◽  
Author(s):  
Javier R. Goicoechea ◽  
Miriam G. Santa-Maria ◽  
Emeric Bron ◽  
David Teyssier ◽  
Nuria Marcelino ◽  
...  
Keyword(s):  
Molecular Cloud ◽  
Massive Stars ◽  
Spatial Scales ◽  
Mass Density ◽  
High Mass ◽  
Molecular Gas ◽  
Mass Star ◽  
Star Forming ◽  
Stellar Feedback ◽  
Co Emission

Young massive stars regulate the physical conditions, ionization, and fate of their natal molecular cloud and surroundings. It is important to find tracers that quantify the stellar feedback processes that take place on different spatial scales. We present ~85 arcmin2 velocity-resolved maps of several submillimeter molecular lines, taken with Herschel/HIFI, toward the closest high-mass star-forming region, the Orion molecular cloud 1 core (OMC-1). The observed rotational lines include probes of warm and dense molecular gas that are difficult, if not impossible, to detect from ground-based telescopes: CH+ (J = 1–0), CO (J = 10–9), HCO+ (J = 6–5), HCN (J = 6–5), and CH (N, J = 1, 3/2–1, 1/2). These lines trace an extended but thin layer (AV ≃ 3–6 mag or ~1016 cm) of molecular gas at high thermal pressure, Pth = nH ⋅ Tk ≈ 107–109 cm−3 K, associated with the far-ultraviolet (FUV) irradiated surface of OMC-1. The intense FUV radiation field – emerging from massive stars in the Trapezium cluster – heats, compresses, and photoevaporates the cloud edge. It also triggers the formation of specific reactive molecules such as CH+. We find that the CH+ (J = 1–0) emission spatially correlates with the flux of FUV photons impinging the cloud: G0 from ~103 to ~105. This relationship is supported by constant-pressure photodissociation region (PDR) models in the parameter space Pth∕G0 ≈ [5 × 103 − 8 × 104] cm−3 K where many observed PDRs seem to lie. The CH+ (J = 1–0) emission also correlates with the extended infrared emission from vibrationally excited H2 (v ≥ 1), and with that of [C II] 158 μm and CO J = 10–9, all emerging from FUV-irradiated gas. These spatial correlations link the presence of CH+ to the availability of C+ ions and of FUV-pumped H2 (v ≥ 1) molecules. We conclude that the parsec-scale CH+ emission and narrow-line (Δv ≃ 3 km s−1) mid-J CO emission arises from extended PDR gas and not from fast shocks. PDR line tracers are the smoking gun of the stellar feedback from young massive stars. The PDR cloud surface component in OMC-1, with a mass density of 120–240 M⊙ pc−2, represents ~5–10% of the total gas mass; however, it dominates the emitted line luminosity, the average CO J = 10–9 surface luminosity in the mapped region being ~35 times brighter than that of CO J = 2–1. These results provide insights into the source of submillimeter CH+ and mid-J CO emission from distant star-forming galaxies.

scholarly journals Massive Star Formation Throughout the Galactic Disk

2009 ◽  
Vol 5 (H15) ◽  
pp. 798-798
Author(s):  
Stan Kurtz
Keyword(s):  
Star Formation ◽  
Galactic Plane ◽  
Galactic Disk ◽  
Young Stellar Objects ◽  
High Mass ◽  
Molecular Gas ◽  
Mass Star ◽  
Ionized Gas ◽  
Stellar Objects ◽  
Infrared Spectral

AbstractHigh-mass star formation is manifestly a phenomenon of the Galactic Plane. The process begins with pre-stellar cores, evolves to proto-stellar objects, and culminates in massive main-sequence stars. Because massive young stellar objects are deeply embedded, the radio, sub-mm, and far/mid-infrared spectral windows are the most revealing. Galactic plane surveys at these wavelengths trace hot and cold molecular gas, interstellar masers, warm dust, and ionized gas that are present during star formation.

scholarly journals GASTON: Galactic Star Formation with NIKA2. Evidence for the mass growth of star-forming clumps

2021 ◽  
Author(s):  
A J Rigby ◽  
N Peretto ◽  
R Adam ◽  
P Ade ◽  
M Anderson ◽  
...  
Keyword(s):  
Star Formation ◽  
Large Scale ◽  
Galactic Plane ◽  
High Sensitivity ◽  
High Mass ◽  
Evolutionary Stage ◽  
Mass Star ◽  
Mass Growth ◽  
Star Forming ◽  
Compact Source

Abstract Determining the mechanism by which high-mass stars are formed is essential for our understanding of the energy budget and chemical evolution of galaxies. By using the New IRAM KIDs Array 2 (NIKA2) camera on the Institut de Radio Astronomie Millimétrique (IRAM) 30-m telescope, we have conducted high-sensitivity and large-scale mapping of a fraction of the Galactic plane in order to search for signatures of the transition between the high- and low-mass star-forming modes. Here, we present the first results from the Galactic Star Formation with NIKA2 (GASTON) project, a Large Programme at the IRAM 30-m telescope which is mapping ≈2 deg2 of the inner Galactic plane (GP), centred on ℓ = 23${_{.}^{\circ}}$9, b = 0${_{.}^{\circ}}$05, as well as targets in Taurus and Ophiuchus in 1.15 and 2.00 mm continuum wavebands. In this paper we present the first of the GASTON GP data taken, and present initial science results. We conduct an extraction of structures from the 1.15 mm maps using a dendrogram analysis and, by comparison to the compact source catalogues from Herschel survey data, we identify a population of 321 previously-undetected clumps. Approximately 80 per cent of these new clumps are 70 μm-quiet, and may be considered as starless candidates. We find that this new population of clumps are less massive and cooler, on average, than clumps that have already been identified. Further, by classifying the full sample of clumps based upon their infrared-bright fraction – an indicator of evolutionary stage – we find evidence for clump mass growth, supporting models of clump-fed high-mass star formation.

scholarly journals Looking for outflow and infall signatures in high-mass star-forming regions

2012 ◽  
Vol 538 ◽  
pp. A140 ◽  
Author(s):  
P. D. Klaassen ◽  
L. Testi ◽  
H. Beuther
Keyword(s):  
High Mass ◽  
Mass Star ◽  
Star Forming ◽  
Star Forming Regions

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 APEX CO (9-8) MAPPING OF AN EXTREMELY HIGH VELOCITY AND JET-LIKE OUTFLOW IN A HIGH-MASS STAR-FORMING REGION

2011 ◽  
Vol 743 (1) ◽  
pp. L25 ◽  
Author(s):  
Keping Qiu ◽  
Friedrich Wyrowski ◽  
Karl M. Menten ◽  
Rolf Güsten ◽  
Silvia Leurini ◽  
...  
Keyword(s):  
High Velocity ◽  
High Mass ◽  
Mass Star ◽  
Star Forming

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.

Magnetic fields in high-mass star-forming regions

2015 ◽  
pp. 199-209
Author(s):  
Antonio Chrysostomou ◽  
Martin Houde ◽  
Brenda C. Matthews
Keyword(s):  
Magnetic Fields ◽  
High Mass ◽  
Mass Star ◽  
Star Forming ◽  
Star Forming Regions
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