Most stars in the universe were evidently formed in stellar nurseries like the Tarantula Nebula, shown in the spectacular image below. I’ve been wanting to shoehorn this item into our pages for a couple of weeks now but always wound up having it preempted by other news. Nonetheless, this look at the complex known as 30 Doradus is well worth pondering as we move into a new year of interstellar studies. It’s based on data collected through four filters using the Wide Field Imager on the European Southern Observatory’s 2.2-m instrument at La Silla (Chile).
Image (click to enlarge): One square degree image of the Tarantula Nebula and its surroundings. The spidery nebula is seen in the upper-centre of the image. Slightly to the lower-right, a web of filaments harbours the famous supernova SN 1987A. Many other reddish nebulae are visible in the image, as well as a cluster of young stars on the left, known as NGC 2100. Credit: Observations carried out by João Alves (Calar Alto, Spain), Benoit Vandame and Yuri Bialetski (ESO) with the Wide Field Imager (WFI) at the 2.2-m telescope on La Silla. The colour composite was made by Bob Fosbury (ST-EcF).
A part of the Large Magellanic Cloud, the Tarantula Nebula is located about 170,000 light years from Earth in the southern constellation Dorado, and is home to some of the most massive stars known. It’s what is known as an emission nebula, a cloud of ionized gas being heated by hot young stars and thereby emitting light. At almost 1000 light years across, the nebula covers an area almost the size of the full Moon as seen from Earth. So vast is the Tarantula that if it were in the Milky Way at the distance of the Orion Nebula, it would cover one-quarter of the sky.
Astrophysics, abstract
astro-ph/0701026
From: You-Hua Chu [view email]
Date: Mon, 1 Jan 2007 23:46:05 GMT (580kb)
Star Formation in the LMC: Gravitational Instability and Dynamical Triggering
Authors: Y.-H. Chu (1), R. A. Gruendl (1), C.-C. Yang (1) ((1) University of Illinois at Urbana-Champaign)
Comments: 6 pages, 6 figures, IAU Symposium 237, Triggered Star Formation in a Turbulent Medium, eds. Elmegreen and Palous
Evidence for triggered star formation is difficult to establish because energy feedback from massive stars tend to erase the interstellar conditions that led to the star formation. Young stellar objects (YSOs) mark sites of {\it current} star formation whose ambient conditions have not been significantly altered. Spitzer observations of the Large Magellanic Cloud (LMC) effectively reveal massive YSOs. The inventory of massive YSOs, in conjunction with surveys of interstellar medium, allows us to examine the conditions for star formation: spontaneous or triggered. We examine the relationship between star formation and gravitational instability on a global scale, and we present evidence of triggered star formation on local scales in the LMC.
http://arxiv.org/abs/astro-ph/0701026
Astrophysics, abstract
astro-ph/0702613
From: Hasan Yuksel [view email]
Date: Thu, 22 Feb 2007 20:54:32 GMT (58kb)
Neutrino Spectrum from SN 1987A and from Cosmic Supernovae
Authors: Hasan Yuksel, John F. Beacom (Ohio State University)
Comments: 8 pages, 3 figures
The detection of neutrinos from SN 1987A by the Kamiokande-II and Irvine-Michigan-Brookhaven detectors provided the first glimpse of core collapse in a supernova, complementing the optical observations and confirming our basic understanding of the mechanism behind the explosion. One long-standing puzzle is that, when fitted with thermal spectra, the two independent detections do not seem to agree with either each other or typical theoretical expectations. We assess the compatibility of the two data sets in a model-independent way and show that they can be reconciled if one avoids any bias on the neutrino spectrum stemming from theoretical conjecture. We reconstruct the neutrino spectrum from SN 1987A directly from the data through non-parametric inferential statistical methods and present predictions for the Diffuse Supernova Neutrino Background based on SN 1987A data. We show that this prediction cannot be too small (especially in the 10-18 MeV range), since the majority of the detected events from SN 1987 were above 18 MeV (including 6 above 35 MeV), suggesting an imminent detection in operational and planned detectors.
http://arxiv.org/abs/astro-ph/0702613
Infrared and X-Ray Evidence for Circumstellar Grain Destruction by the Blast Wave of Supernova 1987A
Authors: E. Dwek, R. G. Arendt, P. Bouchet, D. N. Burrows, P. Challis, I. J. Danziger, J. M. De Buizer, R. D. Gehrz, R. P. Kirshner, R. McCray, S. Park, E. F. Polomski, C. E. Woodward
(Submitted on 17 Dec 2007)
Abstract: Multiwavelength observations of supernova remnant (SNR) 1987A show that its morphology and luminosity are rapidly changing at X-ray, optical, infrared, and radio wavelengths as the blast wave from the explosion expands into the circumstellar equatorial ring, produced by mass loss from the progenitor star. The observed infrared (IR) radiation arises from the interaction of dust grains that formed in mass outflow with the soft X-ray emitting plasma component of the shocked gas. Spitzer IRS spectra at 5 – 30 microns taken on day 6190 since the explosion show that the emission arises from ~ 1.1E-6 Msun of silicate grains radiating at a temperature of ~180+20-15 K. Subsequent observations on day 7137 show that the IR flux had increased by a factor of 2 while maintaining an almost identical spectral shape. The observed IR-to-X-ray flux ratio (IRX) is consistent with that of a dusty plasma with standard Large Magellanic Cloud dust abundances. IRX has decreased by a factor of ~ 2 between days 6190 and 7137, providing the first direct observation of the ongoing destruction of dust in an expanding SN blast wave on dynamic time scales. Detailed models consistent with the observed dust temperature, the ionization timescale of the soft X-ray emission component, and the evolution of IRX suggest that the radiating silicate grains are immersed in a 3.5E6 K plasma with a density of (0.3-1)E4 cm^{-3}, and have a size distribution that is confined to a narrow range of radii between 0.023 and 0.22 microns. Smaller grains may have been evaporated by the initial UV flash from the supernova.
Comments: Accepted for publication in the Astrophysical Journal. Document is 28 pages long and includes 9 figures
Subjects: Astrophysics (astro-ph)
Cite as: arXiv:0712.2759v1 [astro-ph]
Submission history
From: Eli Dwek [view email]
[v1] Mon, 17 Dec 2007 16:17:45 GMT (183kb)
http://arxiv.org/abs/0712.2759