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Title: Hubble Tarantula Treasury Project: Unravelling Tarantula's Web. I. Observational overview and first results
Authors: E. Sabbi, J. Anderson, D. J. Lennon, R. P. van der Marel, A. Aloisi, M. L. Boyer, M. Cignoni, G. de Marchi, S. E. de Mink, C. J. Evans, J. S. Gallagher III, K. Gordon, D. A. Gouliermis, E. K. Grebel, A. M. Koekemoer, S. S. Larsen, N. Panagia, J. E. Ryon, L. J. Smith, M. Tosi, D. Zaritsky

The Hubble Tarantula Treasury Project (HTTP) is an ongoing panchromatic imaging survey of stellar populations in the Tarantula Nebula in the Large Magellanic Cloud that reaches into the sub-solar mass regime (< 0.5 solar masses). HTTP utilises the capability of HST to operate the Advanced Camera for Surveys (ACS) and the Wide Field Camera 3 (WFC3) in parallel to study this remarkable region in the near-ultraviolet, optical, and near-infrared spectral regions, including narrow band H\alpha images. The combination of all these bands provides a unique multi-band view. The resulting maps of the stellar content of the Tarantula Nebula within its main body provide the basis for investigations of star formation in an environment resembling the extreme conditions found in starburst galaxies and in the early Universe. Access to detailed properties of individual stars allows us to begin to reconstruct the evolution of the stellar skeleton of the Tarantula Nebula over space and time with parcsec-scale resolution. In this first paper we describe the observing strategy, the photometric techniques, and the upcoming data products from this survey and present preliminary results obtained from the analysis of the initial set of near-infrared observations.

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Title: The Top Ten Spitzer YSOs in 30 Doradus
Authors: Nolan R. Walborn (Space Telescope Science Institute), Rodolfo H. Barba (Universidad de La Serena, Instituto de Ciencias Astronomicas de la Tierra y del Espacio [ICATE-CONICET]), Marta M. Sewilo (The Johns Hopkins University, Space Science Institute)

The most luminous Spitzer point sources in the 30 Doradus triggered second generation are investigated coherently in the 3-8 micron region. Remarkable diversity and complexity in their natures are revealed. Some are also among the brightest JHK sources, while others are not. Several of them are multiple when examined at higher angular resolutions with HST NICMOS and WFPC2/WFC3 as available, or with VISTA/VMC otherwise. One is a dusty compact H II region near the far northwestern edge of the complex, containing a half dozen bright I-band sources. Three others appear closely associated with luminous WN stars and causal connections are suggested. Some are in the heads of dust pillars oriented toward R136, as previously discussed from the NICMOS data. One resides in a compact cluster of much fainter sources, while another appears monolithic at the highest resolutions. Surprisingly, one is the brighter of the two extended "mystery spots" associated with Knot 2 of Walborn et al. Masses are derived from YSO models for unresolved sources and lie in the 10-30 M_{sun} range. Further analysis of the IR sources in this unique region will advance understanding of triggered massive star formation, perhaps in some unexpected and unprecedented ways.

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R136
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Title: The central density of R136 in 30 Doradus
Authors: Fernando J. Selman, Jorge Melnick

The central density rho_0 of a stellar cluster is an important physical parameter to determine its evolutionary and dynamical state. The degree of mass segregation, or whether the cluster has undergone core collapse both depends on rho_0. We reanalyse the results of a previous paper that gives the mass density profile of R136 and combine them with both a conservative upper limit for the core parameter and a more uncertain recent measurement. We thus place a lower limit on rho_0 under reasonable and defensible assumptions about the IMF and its extrapolation to lower masses finding rho_0 >~ 1.5x10^4 solar masses/pc³ for the conservative assumption a < 0.4 pc for the cluster core parameter. If we use the smaller, but more uncertain value a = 0.025 pc, the central density estimate becomes larger than 10^7 solar masses/pc³. A mechanism based on the destruction of a large fraction of circumstellar disks is posited to explain the hitherto unexplained increase in reddening presented in that same work.

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Hubble Watches Star Clusters on a Collision Course

Astronomers using data from NASA's Hubble Space Telescope have caught two clusters full of massive stars that may be in the early stages of merging. The 30 Doradus Nebula is 170,000 light-years from Earth. What at first was thought to be only one cluster in the core of the massive star-forming region 30 Doradus has been found to be a composite of two clusters that differ in age by about one million years.
The entire 30 Doradus complex has been an active star-forming region for 25 million years, and it is currently unknown how much longer this region can continue creating new stars. Smaller systems that merge into larger ones could help to explain the origin of some of the largest known star clusters. The Hubble observations, made with the Wide Field Camera 3, were taken Oct. 20-27, 2009. The blue color is light from the hottest, most massive stars; the green from the glow of oxygen; and the red from fluorescing hydrogen.

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30 Doradus
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Title: A double cluster at the core of 30 Doradus
Authors: E. Sabbi, D. J. Lennon, M. Gieles, S. E. de Mink, N.R. Walborn, J. Anderson, A. Bellini, N. Panagia, J. Maiz Apellaniz

Based on an analysis of data obtained with the Wide Field Camera 3 (WFC3) on the Hubble Space Telescope (HST) we report the identification of two distinct stellar populations in the core of the giant HII region 30Doradus in the Large Magellanic Cloud. The most compact and richest component coincides with the center of R136 and is ~1 Myr younger than a second more diffuse clump, located ~5.4 pc toward the northeast. We note that published spectral types of massive stars in these two clumps lend support to the proposed age difference. The morphology and age difference between the two sub-clusters suggests that an ongoing merger may occurring within the core of 30Doradus. This finding is consistent with the predictions of models of hierarchical fragmentation of turbulent giant molecular clouds, according to which star clusters would be the final products of merging smaller sub-structures.

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Tarantula nebula
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Hubble's Close Encounter with the Tarantula

675693main_potw1232a-610x547.jpg

Turning its eye to the Tarantula Nebula, the NASA/ESA Hubble Space Telescope has taken this close-up of the outskirts of the main cloud of the Nebula.
The bright wispy structures are the signature of an environment rich in ionised hydrogen gas, called H II by astronomers. In reality these appear red, but the choice of filters and colours of this image, which includes exposures both in visible and infrared light, make the gas appear green.

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Title: The VLT-FLAMES Tarantula Survey. VII. A low velocity dispersion for the young massive cluster R136
Authors: V. Hénault-Brunet (Edinburgh), C. J. Evans, H. Sana, M. Gieles, N. Bastian, J. Maíz Apellániz, N. Markova, W. D. Taylor, E. Bressert, P.A. Crowther, J. Th. van Loon

Detailed studies of resolved young massive star clusters are necessary to determine their dynamical state and evaluate the importance of gas expulsion and early cluster evolution. In an effort to gain insight into the dynamical state of the young massive cluster R136 and obtain the first measurement of its velocity dispersion, we analyse multi-epoch spectroscopic data of the inner regions of 30 Doradus in the Large Magellanic Cloud (LMC) obtained as part of the VLT-FLAMES Tarantula Survey. Following a quantitative assessment of the variability, we use the radial velocities of non-variable sources to place an upper limit of 6 km/s on the line-of-sight velocity dispersion of stars within a projected distance of 5 pc from the centre of the cluster. After accounting for the contributions of undetected binaries and measurement errors through Monte Carlo simulations, we conclude that the true velocity dispersion is likely between 4 and 5 km/s given a range of standard assumptions about the binary distribution. This result is consistent with what is expected if the cluster is in virial equilibrium, suggesting that gas expulsion has not altered its dynamics. We find that the velocity dispersion would be ~25 km/s if binaries were not identified and rejected, confirming the importance of the multi-epoch strategy and the risk of interpreting velocity dispersion measurements of unresolved extragalactic young massive clusters.

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Star cluster R136
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Astronomers crack mystery of the "monster stars"

In 2010 scientists discovered four 'monster' sized stars, with the heaviest more than 300 times as massive as our Sun. Despite their incredible luminosity, these exotic objects, located in the giant star cluster R136 in the nearby galaxy the Large Magellanic Cloud; have oddly so far been found nowhere else. Now a group of astronomers at the University of Bonn have a new explanation: the ultramassive stars were created from the merger of lighter stars in tight binary systems. The team present their results in the journal Monthly Notices of the Royal Astronomical Society.
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Hubble's 22nd Anniversary Image Shows Turbulent Star-making Region

Several million young stars are vying for attention in this NASA Hubble Space Telescope image of a raucous stellar breeding ground in 30 Doradus, located in the heart of the Tarantula Nebula.  30 Doradus is the brightest star-forming region visible in a neighbouring galaxy and home to the most massive stars ever seen. The nebula resides 170,000 light-years away in the Large Magellanic Cloud, a small, satellite galaxy of our Milky Way. No known star-forming region that is inside our Milky Way is as large or as prolific as 30 Doradus.
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Peculiar objects lurk in Tarantula Nebula


Credit AstroNow09

A survey of the binary stars in the Tarantula Nebula has unexpectedly revealed some peculiar objects, as researcher Paul Dunstall explains.



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