scholarly journals Probing the clumping structure of giant molecular clouds through the spectrum, polarisation and morphology of X-ray reflection nebulae

2016 ◽  
Vol 589 ◽  
pp. A88 ◽  
Author(s):  
Margherita Molaro ◽  
Rishi Khatri ◽  
Rashid A. Sunyaev
Keyword(s):  
Molecular Clouds ◽  
Giant Molecular Clouds ◽  
X Ray ◽  
Reflection Nebulae

scholarly journals X-Ray Observations of Orion OBib Association

1998 ◽  
Vol 188 ◽  
pp. 230-231
Author(s):  
M. Nakano
Keyword(s):  
Molecular Clouds ◽  
Main Sequence ◽  
Giant Molecular Clouds ◽  
Main Sequence Stars ◽  
Huge Number ◽  
X Ray ◽  
T Tauri ◽  
Sky Survey ◽  
Hα Emission ◽  
Objective Prism

The signs of the active star formation in the Orion region are mainly found in the direction of the two giant molecular clouds - Ori A and Ori B -. Recent objective prism survey in the Orion region shows large number of Hα emission-line stars distributed outside of the giant molecular clouds (Nakano et al., 1995). Many weak-lined T Tauri star candidates are also discovered by the discrimination analysis of the X-ray sources found in the ROSAT all sky survey (RASS) (Sterzik et al., 1995). Although such huge number of pre-main sequence stars outside of the molecular cloud was not expected, their nature is still in controversial (Neuhäuser, 1997). To know the X-ray properties of these sources in the Orion region, we have carried out the ASCA observations.

scholarly journals Prospects for IXPE and eXTP polarimetric archaeology of the reflection nebulae in the Galactic center

2020 ◽  
Vol 643 ◽  
pp. A52
Author(s):  
L. Di Gesu ◽  
R. Ferrazzoli ◽  
I. Donnarumma ◽  
P. Soffitta ◽  
E. Costa ◽  
...  
Keyword(s):  
Molecular Clouds ◽  
Galactic Center ◽  
Region Of Interest ◽  
Polarization Degree ◽  
Polarization Angle ◽  
Diffuse Emission ◽  
X Ray ◽  
X Ray Imaging ◽  
Spread Function ◽  
Reflection Nebulae

The X-ray polarization properties of the reflection nebulae in the Galactic center inform us about the direction of the illuminating source (through the polarization angle) and the cloud position along the line of sight (through the polarization degree). However, the detected polarization degree is expected to be lowered because the polarized emission of the clouds is mixed with the unpolarized diffuse emission that permeates the Galactic center region. In a real observation, also the morphological smearing of the source due to the point spread function and the unpolarized instrumental background contribute in diluting the polarization degree. So far, these effects have never been included in the estimation of the dilution. We evaluate the detectability of the X-ray polarization predicted for the MC2, Bridge-B2, G0.11-0.11, Sgr B2, Sgr C1, Sgr C2, and Sgr C3 molecular clouds with modern X-ray imaging polarimeters such as the Imaging X-ray Polarimetry Explorer (IXPE), which is expected to launch in 2021, and the Enhanced X-ray Timing and Polarimetry mission (eXTP), whose launch is scheduled for 2027. We perform realistic simulations of X-ray polarimetric observations considering (with the aid of Chandra maps and spectra) the spatial, spectral, and polarization properties of all the diffuse emission and background components in each region of interest. We find that in the 4.0–8.0 keV band, where the emission of the molecular clouds outshines the other components, the dilution of the polarization degree, including the contribution due to the morphological smearing of the source, ranges between ~19% and ~55%. We conclude that for some distance values reported in the literature, the diluted polarization degree of G0.11-0.11, Sgr B2, Bridge-B2, Bridge-E, Sgr C1, and Sgr C3 may be detectable in a 2 Ms long IXPE observations. With the same exposure time, and considering the whole range of possible distances reported in the literature, the enhanced capabilities of eXTP may allow detecting the 4.0–8.0 keV of all the targets considered here.

Hard X-ray emission from giant molecular clouds NGC 6334 and M17

1999 ◽  
Vol 320 (4-5) ◽  
pp. 323-323 ◽  
Author(s):  
K. Matsuzaki ◽  
Y. Sekimoto ◽  
T. Kamae ◽  
S. Yamamoto ◽  
K. Tatematsu ◽  
...  
Keyword(s):  
Molecular Clouds ◽  
Giant Molecular Clouds ◽  
X Ray ◽  
Ngc 6334

scholarly journals X-RAY DIAGNOSTICS OF GIANT MOLECULAR CLOUDS IN THE GALACTIC CENTER REGION AND PAST ACTIVITY OF Sgr A*

2011 ◽  
Vol 740 (2) ◽  
pp. 103 ◽  
Author(s):  
Hirokazu Odaka ◽  
Felix Aharonian ◽  
Shin Watanabe ◽  
Yasuyuki Tanaka ◽  
Dmitry Khangulyan ◽  
...  
Keyword(s):  
Molecular Clouds ◽  
Galactic Center ◽  
Giant Molecular Clouds ◽  
X Ray ◽  
Center Region ◽  
Sgr A ◽  
Past Activity

scholarly journals X-ray emission from the giant molecular clouds in the Galactic Center region and the discovery of new X-ray sources

2001 ◽  
Vol 372 (2) ◽  
pp. 651-662 ◽  
Author(s):  
L. Sidoli ◽  
S. Mereghetti ◽  
A. Treves ◽  
A. N. Parmar ◽  
R. Turolla ◽  
...  
Keyword(s):  
Molecular Clouds ◽  
Galactic Center ◽  
Giant Molecular Clouds ◽  
X Ray ◽  
Center Region

Reflected X-ray Emissions on Giant Molecular Clouds ? Evidence of the Past Activities of Sgr A*

2003 ◽  
Vol 324 (S1) ◽  
pp. 125-131 ◽  
Author(s):  
Hiroshi Murakami ◽  
Atsushi Senda ◽  
Yoshitomo Maeda ◽  
Katsuji Koyama
Keyword(s):  
Molecular Clouds ◽  
Giant Molecular Clouds ◽  
X Ray ◽  
The Past ◽  
Sgr A

scholarly journals Molecules in the Magellanic Clouds

1991 ◽  
Vol 148 ◽  
pp. 415-420 ◽  
Author(s):  
R. S. Booth ◽  
Th. De Graauw
Keyword(s):  
High Resolution ◽  
Molecular Clouds ◽  
Short Review ◽  
Large Magellanic Cloud ◽  
Magellanic Cloud ◽  
Magellanic Clouds ◽  
Giant Molecular Clouds ◽  
Interstellar Molecules ◽  
First Time ◽  
Excitation Conditions

In this short review we describe recent new observations of millimetre transitions of molecules in selected regions of the Magellanic Clouds. The observations were made using the Swedish-ESO Submillimetre Telescope, SEST, (Booth et al. 1989), the relatively high resolution of which facilitates, for the first time, observations of individual giant molecular clouds in the Magellanic Clouds. We have mapped the distribution of the emission from the two lowest rotational transitions of 12CO and 13CO and hence have derived excitation conditions for the molecule. In addition, we have observed several well-known interstellar molecules in the same regions, thus doubling the number of known molecules in the Large Magellanic Cloud (LMC). The fact that all the observations have been made under controlled conditions with the same telescope enables a reasonable intercomparison of the molecular column densities. In particular, we are able to observe the relative abundances among the different isotopically substituted species of CO.

scholarly journals Effects of initial density profiles on massive star cluster formation in giant molecular clouds

2021 ◽  
Author(s):  
Yingtian Chen ◽  
Hui Li ◽  
Mark Vogelsberger
Keyword(s):  
Angular Momentum ◽  
Star Formation ◽  
Molecular Clouds ◽  
Globular Clusters ◽  
Cluster Formation ◽  
Initial Density ◽  
Giant Molecular Clouds ◽  
Density Profiles ◽  
Stellar Feedback ◽  
Gas Accretion

Abstract We perform a suite of hydrodynamic simulations to investigate how initial density profiles of giant molecular clouds (GMCs) affect their subsequent evolution. We find that the star formation duration and integrated star formation efficiency of the whole clouds are not sensitive to the choice of different profiles but are mainly controlled by the interplay between gravitational collapse and stellar feedback. Despite this similarity, GMCs with different profiles show dramatically different modes of star formation. For shallower profiles, GMCs first fragment into many self-gravitation cores and form sub-clusters that distributed throughout the entire clouds. These sub-clusters are later assembled ‘hierarchically’ to central clusters. In contrast, for steeper profiles, a massive cluster is quickly formed at the center of the cloud and then gradually grows its mass via gas accretion. Consequently, central clusters that emerged from clouds with shallower profiles are less massive and show less rotation than those with the steeper profiles. This is because 1) a significant fraction of mass and angular momentum in shallower profiles is stored in the orbital motion of the sub-clusters that are not able to merge into the central clusters 2) frequent hierarchical mergers in the shallower profiles lead to further losses of mass and angular momentum via violent relaxation and tidal disruption. Encouragingly, the degree of cluster rotations in steeper profiles is consistent with recent observations of young and intermediate-age clusters. We speculate that rotating globular clusters are likely formed via an ‘accretion’ mode from centrally-concentrated clouds in the early Universe.

scholarly journals The Ballistic Particle Model

1983 ◽  
Vol 100 ◽  
pp. 133-134
Author(s):  
Frank N. Bash
Keyword(s):  
Radial Velocity ◽  
Gravitational Potential ◽  
Molecular Clouds ◽  
Milky Way ◽  
Terminal Velocity ◽  
Particle Model ◽  
The Sun ◽  
Giant Molecular Clouds ◽  
Spiral Pattern ◽  
Armed Spiral

Bash and Peters (1976) suggested that giant molecular clouds (GMC's) can be viewed as ballistic particles launched from the two-armed spiral-shock (TASS) wave with orbits influenced only by the overall galactic gravitational potential perturbed by the spiral gravitational potential in the arms. For GMC's in the Milky Way, the model predicts that the radial velocity observed from the Sun increases with age (time since launch). We showed that the terminal velocity of CO observed from l ≃ 30° to l ≃ 60° can be understood if all GMC's are born in the spiral pattern given by Yuan (1969) and live 30 × 106 yrs. Older GMC's were predicted to have radial velocities which exceed observed terminal velocities.

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