* Astronomy

Title: Herschel far-infrared observations of the Carina Nebula Complex. - III: Detailed cloud structure and feedback effects
Authors: Veronica Roccatagliata, Thomas Preibisch, Thorsten Ratzka, Benjamin Gaczkowski

The Carina Nebula complex (CNC) represents one of the most massive star-forming regions in our Galaxy and shows strong feedback from the high massive stars. We use our Herschel FIR observations to study the properties of the clouds over the entire area of the CNC. The good angular resolution of the Herschel maps corresponds to physical scales of 0.1 - 0.4 pc, and allows us to analyse the small-scale structures of the clouds. The full extent of the CNC was mapped with PACS and SPIRE from 70 to 500 micron. We determine temperatures and column densities at each point in this maps by modelling the observed FIR SEDs. We also derive a map showing the strength of the UV field. We investigate the relation between the cloud properties and the spatial distribution of the high-mass stars, and compute total cloud masses for different density thresholds. Our Herschel maps resolve, for the first time, the small-scale structure of the dense clouds. Several particularly interesting regions, including the prominent pillars south of eta Car, are analysed in detail. We compare the cloud masses derived from the Herschel data to previous mass estimates based on sub-mm and molecular line data. Our maps also reveal a peculiar "wave"-like pattern in the northern part of the Carina Nebula. Finally, we characterise two prominent cloud complexes at the periphery of our Herschel maps, which are probably molecular clouds in the Galactic background. We find that the density and temperature structure of the clouds in most parts of the CNC is dominated by the strong feedback from the numerous massive stars, rather than random turbulence. Comparing the cloud mass and the star formation rate derived for the CNC to other Galactic star forming regions suggests that the CNC is forming stars in an particularly efficient way. We suggest this to be a consequence of triggered star formation by radiative cloud compression.

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Title: H.E.S.S. observations of the Carina nebula and its enigmatic colliding wind binary Eta Carinae
Authors: HESS Collaboration, A. Abramowski, F. Acero, F. Aharonian, A. G. Akhperjanian, G. Anton, A. Balzer, A. Barnacka, Y. Becherini, J. Becker, K. Bernlöhr, E. Birsin, J. Biteau, A. Bochow, C. Boisson, J. Bolmont, P. Bordas, J. Brucker, F. Brun, P. Brun, T. Bulik, I. Büsching, S. Carrigan, S. Casanova, M. Cerruti, P. M. Chadwick, A. Charbonnier, R. C. G. Chaves, A. Cheesebrough, G. Cologna, J. Conrad, M. Dalton, M. K. Daniel, I. D. Davids, B. Degrange, C. Deil, H. J. Dickinson, A. Djannati-Ataï, W. Domainko, L. O'C. Drury, G. Dubus, K. Dutson, J. Dyks, M. Dyrda, K. Egberts, P. Eger, P. Espigat, L. Fallon, S. Fegan, F. Feinstein, M. V. Fernandes, A. Fiasson, G. Fontaine, A. Förster, M. Fübling, Y. A. Gallant, T. Garrigoux, H. Gast, L. Gèrard, B. Giebels, J. F. Glicenstein, et al. (133 additional authors not shown)

The massive binary system Eta Carinae and the surrounding HII complex, the Carina Nebula, are potential particle acceleration sites from which very-high-energy (VHE; E > 100 GeV) \gamma-ray emission could be expected. This paper presents data collected during VHE \gamma-ray observations with the H.E.S.S. telescope array from 2004 to 2010, which cover a full orbit of Eta Carinae. In the 33.1-hour data set no hint of significant \gamma-ray emission from Eta Carinae has been found and an upper limit on the \gamma-ray flux of 7.7 x 10-13 ph cm-2 s-1 (99% confidence level) is derived above the energy threshold of 470 GeV. Together with the detection of high-energy (HE; 0.1 GeV > E > 100 GeV) \gamma-ray emission by the Fermi-LAT up to 100 GeV, and assuming a continuation of the average HE spectral index into the VHE domain, these results imply a cut-off in the \gamma-ray spectrum between the HE and VHE \gamma-ray range. This could be caused either by a cut-off in the accelerated particle distribution or by severe \gamma-\gamma\ absorption losses in the wind collision region. Furthermore, the search for extended \gamma-ray emission from the Carina Nebula resulted in an upper limit on the \gamma-ray flux of 4.2 x 10-12 ph cm-2 s-1 (99% confidence level). The derived upper limit of ~23 on the cosmic-ray enhancement factor is compared with results found for the old-age mixed-morphology supernova remnant W 28.

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The Very Large Telescope in Chile has captured the most detailed infrared image yet of the Carina Nebula, a "stellar nursery" visible from the Southern Hemisphere.
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A Pocket of Star Formation



This new view shows a stellar nursery called NGC 3324. It was taken using the Wide Field Imager on the MPG/ESO 2.2-metre telescope at the La Silla Observatory in Chile. The intense ultraviolet radiation from several of NGC 3324's hot young stars causes the gas cloud to glow with rich colours and has carved out a cavity in the surrounding gas and dust.
NGC 3324 is located in the southern constellation of Carina (The Keel, part of Jason's ship the Argo) roughly 7500 light-years from Earth. It is on the northern outskirts of the chaotic environment of the Carina Nebula, which has been sculpted by many other pockets of star formation. A rich deposit of gas and dust in the NGC 3324 region fuelled a burst of starbirth there several millions of years ago and led to the creation of several hefty and very hot stars that are prominent in the new picture.
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