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Post Info TOPIC: Tarantula nebula


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Title: Characterising Cosmic-Ray Propagation in Massive Star-Forming Regions: The Case of 30 Doradus and the Large Magellanic Cloud
Authors: E.J. Murphy, T.A. Porter, I.V. Moskalenko, G. Helou, A.W. Strong

Using infrared, radio, and gamma-ray data, e investigate the propagation characteristics of cosmic-ray (CR) electrons and nuclei in the 30 Doradus (30\,Dor) star-forming region in the Large Magellanic Cloud (LMC) using a phenomenological model based on the radio-far-infrared correlation within galaxies. Employing a correlation analysis, we derive an average propagation length of ~ 100-140 pc for ~ 3 GeV CR electrons resident in 30 Dor from consideration of the radio and infrared data. Assuming that the observed gamma-ray emission towards 30 Dor is associated with the star-forming region, and applying the same methodology to the infrared and gamma-ray data, we estimate a ~ 20 GeV propagation length of 200-320 pc for the CR nuclei. This is approximately twice as large as for ~ 3 GeV CR electrons, corresponding to a spatial diffusion coefficient that is ~ 4 times higher, scaling as (R/GV)^{\delta} with \delta ~ 0.7-0.8 depending on the smearing kernel used in the correlation analysis. This value is in agreement with the results found by extending the correlation analysis to include ~ 70 GeV CR nuclei traced by the 3-10 GeV gamma-ray data (\delta ~ 0.66±0.23). Using the mean age of the stellar populations in 30 Dor and the results from our correlation analysis, we estimate a diffusion coefficient D_{R} ~ 0.9-1.0 x 10^27 (R/GV)^{0.7} cm^2 s^-1. We compare the values of the CR electron propagation length and surface brightness for 30 Dor and the LMC as a whole with those of entire disk galaxies. We find that the trend of decreasing average CR propagation distance with increasing disk-averaged star formation activity holds for the LMC, and extends down to single star-forming regions, at least for the case of 30 Dor.

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Title: A kinematic study of the giant star-forming region 30 Doradus
Authors: Sergio Torres-Flores, Rodolfo Barbá, Jesús Maíz Apellániz, Mónica Rubio, Guillermo Bosch

We present, for the first time, an optical spectroscopic data cube of the giant star-forming region 30 Doradus, obtained with the GIRAFFE on the VLT at Paranal Observatory. The main emission lines present in this data cube correspond to H{\alpha}, [NII] 6548 {\AA} and [NII] 6584 {\AA}. By using this data set, we found that H{\alpha} presents from simple to multiple profiles, which suggests that different physical mechanisms act in different ways on the excited gas in 30 Doradus. We found, at least, three unclassified large expanding structures. These structures correlate with peaks in the X-ray distribution. Given the excellent signal-to-noise ratio and the large spatial coverage of this data cube, we have studied in detail the kinematics of 30 Doradus, showing the importance of the small scale phenomena on the integrated properties of 30 Doradus.

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The Tarantula Glows with X-rays and Infrared Light

This spiderweb-like tangle of gas and dust is a star-forming region called 30 Doradus. It is one of the largest such regions located close to the Milky Way galaxy, and is found in the neighbouring galaxy Large Magellanic Cloud. About 2,400 massive stars in the center of 30 Doradus, also known as the Tarantula nebula, are producing intense radiation and powerful winds as they blow off material.
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Tarantula Nebula (30 Doradus):
30 Doradus and The Growing Tarantula Within

30dor_xray_thm100.jpg

The star-forming region, 30 Doradus, is one of the largest located close to the Milky Way and is found in the neighbouring galaxy Large Magellanic Cloud. About 2,400 massive stars in the center of 30 Doradus, also known as the Tarantula Nebula, are producing intense radiation and powerful winds as they blow off material.
Multimillion-degree gas detected in X-rays (blue) by the Chandra X-ray Observatory comes from shock fronts -- similar to sonic booms --formed by these stellar winds and by supernova explosions. This hot gas carves out gigantic bubbles in the surrounding cooler gas and dust.

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Hubble Snaps Close-up of the Tarantula

heic1105a.jpg

The NASA/ESA Hubble Space Telescope has produced an outstanding image of part of the famous Tarantula Nebula, a vast star-forming cloud of gas and dust in our neighbouring galaxy, the Large Magellanic Cloud. In this picture, we see a close-up of the Tarantula's central region, glowing brightly with ionised gases and young stars.
The wispy arms of the Tarantula Nebula were originally thought to resemble spindly spider legs, giving the nebula its unusual name. The part of the nebula visible in this image from Hubbles Advanced Camera for Surveys is criss-crossed with tendrils of dust and gas churned up by recent supernovae. These supernova remnants include NGC 2060, visible above and to the left of the centre of this image, which contains the brightest known pulsar.

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Title: The R136 star cluster hosts several stars whose individual masses greatly exceed the accepted 150 Msun stellar mass limit
Authors: Paul A Crowther (Sheffield), Olivier Schnurr (Sheffield, AIP), Raphael Hirschi (Keele, Tokyo), Norhasliza Yusof (Malaya), Richard J Parker (Sheffield), Simon P Goodwin (Sheffield), Hasan Abu Kassim (Malaya)

Spectroscopic analyses of H-rich WN5-6 stars within the young star clusters NGC 3603 and R136 are presented, using archival HST & VLT spectroscopy, & high spatial resolution near-IR photometry. We derive high T* for the WN stars in NGC 3603 (T*~42±2 kK) & R136 (T*~53±3 kK) plus clumping-corrected dM/dt ~ 2-5x10^-5 Msun/yr which closely agree with theoretical predictions. These stars make a disproportionate contribution to the global budget of their host clusters. R136a1 alone supplies ~7% of N(LyC) of the entire 30 Dor region. Comparisons with stellar models calculated for the main-sequence evolution of 85-500 Msun suggest ages of ~1.5 Myr & M_init in the range 105 - 170 Msun for 3 systems in NGC 3603, plus 165-320 Msun for 4 stars in R136. Our high stellar masses are supported by dynamical mass determinations for the components of NGC 3603 A1. We consider the predicted L_X of the R136 stars if they were close, colliding wind binaries. R136c is consistent with a colliding wind binary system. However, short period, colliding wind systems are excluded for R136a WN stars if mass ratios are of order unity. Widely separated systems would have been expected to harden owing to early dynamical encounters with other massive stars in such a dense environment. From simulated star clusters, whose constituents are randomly sampled from the Kroupa IMF, both clusters are consistent with a tentative upper mass limit of ~300 Msun. The Arches cluster is either too old, exhibits a deficiency of very massive stars, or more likely stellar masses have been underestimated - M_init for the most luminous stars in the Arches cluster approach 200 Msun according to contemporary stellar & photometric results. The potential for stars greatly exceeding 150 Msun within metal-poor galaxies suggests that such pair-instability SNe could occur within the local universe, as has been claimed for SN 2007bi.

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Star cluster R136
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Astronomers have discovered the most massive stars to date.
Using the European Southern Observatory's Very Large Telescope, they found one which at birth had more than 300 times the mass of the Sun and is 10 million times more luminous.

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30 Doradus 016
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Massive star bolts across space at 250,000MPH

NASA's Hubble telescope has spotted a huge star -- 90 times more massive than the Sun -- blasting across space at over than 250,000 miles an hour, a speed that scientists say would let a spacecraft zip to the Moon and back in two hours.
The Hubble Space Telescope's Cosmic Origins Spectrograph (COS), the European Southern Observatory's Very Large Telescope (VLT) and some keen research suggest that the star may have travelled about 375 light-years from its suspected home, a giant star cluster called R136, scientists said. The cluster contains several stars topping 100 solar masses each (one solar mass is equal to  1.98892 x 10^30 kilograms, or the mass of the Sun).
Institute scientists say the massive star is about 10 times hotter than the Sun, a temperature that is consistent with a high-mass object.

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-- Edited by Blobrana on Tuesday 11th of May 2010 04:40:29 PM

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Star cluster R136
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"If the radiance of a thousand suns were to burst at once into the sky, that would be like the splendour of the mighty one.  Now I am become Death, the destroyer of worlds.

This well-publicised passage from Hindu scripture describes the nighttime sky as it would look from inside the star cluster R136 which lies 170 million light-years away in a satellite galaxy of our Milky Way, the Large Magellanic Cloud (LMC). In todays newly released Hubble Space Telescope pictures, brilliant blue white newborn stars shine like diamonds on black velvet.
The super hot stars are each blazing at tens of thousands of times the brightness of our sun. The view would be nothing less than overwhelmingly opulent for anyone living inside the cluster. The stars would cast shadows on the ground.


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RE: Tarantula nebula
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