The 6.4 keV Fe Line and the SiO Emission in the GC

2001 ◽  
Vol 205 ◽  
pp. 36-37
Author(s):  
J. Martín-Pintado ◽  
P. de Vicente ◽  
N. Rodríguez-Fernández ◽  
A. Fuente ◽  
P. Planesas
Keyword(s):  
Spatial Distribution ◽  
Gas Phase ◽  
Molecular Clouds ◽  
Galactic Center ◽  
X Rays ◽  
Refractory Elements

We present a map of the Galactic center in the J=l-0 line of SiO covering the region mapped with the ASCA satellite in the 6.4 keV Fe line. We find a correlation between the spatial distribution of the Fe 6.4 keV line and the SiO emission. The SiO abundance increases by more than a factor of 20 in the regions with strong Fe 6.4 keV line. This indicates that the Fe 6.4 keV line mainly arises from molecular clouds with large gas phase abundance of refractory elements. We discuss the implications of the correlation on the origin of the hard X-rays, and the heating and the chemistry of the molecular clouds in the GC.

scholarly journals A confusion-limited spectral-line survey of Sgr B2(N) at 1, 2, and 3mm: Establishing the organic inventory in molecular clouds

2008 ◽  
Vol 4 (S251) ◽  
pp. 27-28 ◽  
Author(s):  
DeWayne T. Halfen ◽  
Lucy M. Ziurys
Keyword(s):  
Spectral Line ◽  
Gas Phase ◽  
Molecular Clouds ◽  
Galactic Center ◽  
Current Data ◽  
Complex Molecules ◽  
Preliminary Results ◽  
Prebiotic Molecules ◽  
Line Survey

AbstractWe present preliminary results of an spectral-line survey at 1, 2, and 3 mm of the galactic center cloud Sgr B2(N). With the current data, several simple prebiotic molecules have been conclusively identified, while several more complex molecules have not. When complete, this survey will provide an accurate database of the gas-phase organic inventory in Sgr B2(N).

scholarly journals Molecules in the circumnuclear disk of the Galactic center

2013 ◽  
Vol 9 (S303) ◽  
pp. 78-82
Author(s):  
Nanase Harada ◽  
Denise Riquelme ◽  
Serena Viti ◽  
Karl Menten ◽  
Miguel Requena-Torres ◽  
...  
Keyword(s):  
Chemical Composition ◽  
Shock Waves ◽  
Molecular Clouds ◽  
Galactic Center ◽  
Cosmic Ray ◽  
Central Star ◽  
Ionization Rate ◽  
Data Sets ◽  
X Rays ◽  
Circumnuclear Disk

AbstractWithin a few parsecs around the central black hole A*, chemistry in the dense molecular cloud material of the circumnuclear disk (CND) can be affected by many energetic phenomena such as high UV-flux from the massive central star cluster, X-rays from A*, shock waves, and an enhanced cosmic-ray flux. Recently, spectroscopic surveys with the IRAM 30 meter and the APEX 12 meter telescopes of substantial parts of the 80–500 GHz frequency range were made toward selected positions in and near the CND. These data sets contain lines from the molecules HCN, HCO+, HNC, CS, SO, SiO, CN, H2CO, HC3N, N2H+, H3O+ and others. We conduct Large Velocity Gradient analyses to obtain column densities and total hydrogen densities, n, for each species in molecular clouds located in the southwest lobe of the CND. The data for the above mentioned molecules indicate 105 cm−3 ≲ n < 106 cm−3, which shows that the CND is tidally unstable. The derived chemical composition is compared with a chemical model calculated using the UCL_CHEM code that includes gas and grain reactions, and the effects of shock waves. Models are run for varying shock velocities, cosmic-ray ionization rates, and number densities. The resulting chemical composition is fitted best to an extremely high value of cosmic-ray ionization rate ζ ∼ 10−14 s−1, 3 orders of magnitude higher than the value in regular Galactic molecular clouds, if the pre-shock density is n=105 cm−3.

scholarly journals Particle Propagation in the Galactic Center and Spatial Distribution of Non-Thermal X-Rays

2009 ◽  
Vol 61 (5) ◽  
pp. 1093-1098 ◽  
Author(s):  
Vladimir A. Dogiel ◽  
Dmitrii Chernyshov ◽  
Takayuki Yuasa ◽  
Kwong-Sang Cheng ◽  
Aya Bamba ◽  
...  
Keyword(s):  
Spatial Distribution ◽  
Galactic Center ◽  
X Rays ◽  
Particle Propagation

scholarly journals Spatial Distribution of the Galactic Center Diffuse X-Rays and the Spectra of the Brightest 6.4 keV Clumps

2009 ◽  
Vol 61 (sp1) ◽  
pp. S255-S262 ◽  
Author(s):  
Katsuji Koyama ◽  
Yojiro Takikawa ◽  
Yoshiaki Hyodo ◽  
Tatsuya Inui ◽  
Masayoshi Nobukawa ◽  
...  
Keyword(s):  
Spatial Distribution ◽  
Galactic Center ◽  
X Rays

X-rays from the HII Regions and Molecular Clouds near the Galactic Center

2003 ◽  
Vol 324 (S1) ◽  
pp. 117-123 ◽  
Author(s):  
Katsuji Koyama ◽  
Hiroshi Murakami ◽  
Shinichiro Takagi
Keyword(s):  
Molecular Clouds ◽  
Galactic Center ◽  
Hii Regions ◽  
X Rays

scholarly journals On a Possible Origin of the Gamma-ray Excess around the Galactic Center

Symmetry ◽  
2021 ◽  
Vol 13 (8) ◽  
pp. 1432
Author(s):  
Dmitry O. Chernyshov ◽  
Andrei E. Egorov ◽  
Vladimir A. Dogiel ◽  
Alexei V. Ivlev
Keyword(s):  
Dark Matter ◽  
Gamma Rays ◽  
Molecular Clouds ◽  
Alternative Explanation ◽  
Gamma Ray ◽  
Galactic Center ◽  
The Self ◽  
Large Area ◽  
Mhd Turbulence ◽  
The Standard Model

Recent observations of gamma rays with the Fermi Large Area Telescope (LAT) in the direction of the inner galaxy revealed a mysterious excess of GeV. Its intensity is significantly above predictions of the standard model of cosmic rays (CRs) generation and propagation with a peak in the spectrum around a few GeV. Popular interpretations of this excess are that it is due to either spherically distributed annihilating dark matter (DM) or an abnormal population of millisecond pulsars. We suggest an alternative explanation of the excess through the CR interactions with molecular clouds in the Galactic Center (GC) region. We assumed that the excess could be imitated by the emission of molecular clouds with depleted density of CRs with energies below ∼10 GeV inside. A novelty of our work is in detailed elaboration of the depletion mechanism of CRs with the mentioned energies through the “barrier” near the cloud edge formed by the self-excited MHD turbulence. This depletion of CRs inside the clouds may be a reason for the deficit of gamma rays from the Central Molecular Zone (CMZ) at energies below a few GeV. This in turn changes the ratio between various emission components at those energies and may potentially absorb the GeV excess by a simple renormalization of key components.

scholarly journals Photoproduction of H3+ from gaseous methanol inside dense molecular clouds

2008 ◽  
Vol 4 (S251) ◽  
pp. 369-370
Author(s):  
S. Pilling ◽  
D. P. P. Andrade ◽  
A. C. F. Santos ◽  
H. M. Boechat-Roberty
Keyword(s):  
Cross Sections ◽  
Molecular Clouds ◽  
Mass Spectra ◽  
Column Density ◽  
X Rays ◽  
Alternative Source ◽  
X Ray ◽  
Flight Mass Spectrometry ◽  
Dense Molecular Cloud ◽  
Synchrotron Light

AbstractWe present experimental results obtained from photoionization and photodissociation processes of abundant interstellar methanol (CH3OH) as an alternative route for the production of H3+ in dense clouds. The measurements were taken at the Brazilian Synchrotron Light Laboratory (LNLS) employing soft X-ray and time-of-flight mass spectrometry. Mass spectra were obtained using the photoelectron-photoion coincidence techniques. Absolute averaged cross sections for the production of H3+ due to molecular dissociation of methanol by soft X-rays (C1s edge) were determined. The H3+'s photoproduction rate and column density were been estimated adopting a typical soft X-ray luminosity inside dense molecular and the observed column density of methanol. Assuming a steady state scenario, the highest column density value for the photoproduced H3+ was about 1011 cm2, which gives the ratio photoproduced/observed of about 0.05%, as in the case of dense molecular cloud AFGL 2591. Despite the small value, this represent a new and alternative source of H3+ into dense molecular clouds and it is not been considered as yet in interstellar chemistry models.

POLYMÉRISATION PAR LES RAYONS-X DU CHLORURE DE VINYLE À L'ÉTAT DE VAPEUR

1963 ◽  
Vol 41 (6) ◽  
pp. 1578-1587 ◽  
Author(s):  
Jan A. Herman ◽  
Pierre M. Hupin
Keyword(s):  
Activation Energy ◽  
Gas Phase ◽  
Average Molecular Weight ◽  
Negative Temperature ◽  
Solid Polymer ◽  
X Rays ◽  
Kcal Mole ◽  
Rate Of Polymerization ◽  
G Value ◽  
Termination Process

The polymerization of vinyl chloride in the gas phase by X rays gives a solid polymer of 1140 average molecular weight. The G value of monomer disappearance varies from 100 to 400 and depends on pressure and temperature. From the measure of the rate of polymerization it was possible to deduce the activation energy of the chain propagation steps: 2.5 kcal/mole, and that of the hindered termination process: 7.4 kcal/mole. The negative temperature co-efficient of the polymerization is explained by the importance of this hindered termination process.

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