Abstract by Michael F. Corcoran
Extremely massive stars (50 solar masses and above) are exceedingly rare in the local Universe but are believed to compose the entire first generation of stars, which lived fast, died young and left behind the first generation of black holes and set the stage for the formation of lower mass stars suitable to support life. For most of their lives, extremely massive stars give mass back to the ISM out of which they formed via strong radiatively-driven winds, though sporadic eruptions may play an important role too. This mass loss plays an important role in the chemical and dynamical evolution of the local interstellar medium prior to the supernova explosion. I'll discuss how high energy thermal (and, in some cases, non-thermal) emission, along with modern simulations in 2 and 3 dimensions, can be used to help determine a physically realistic picture of mass loss in some well-studied systems.
Relevant Papers
cv_corcoran.pdf
Talk Slides
pdf
Friday, April 29, 2011
Friday, April 15, 2011
Dust in the extremely metal poor galaxy I Zw 18
Abstract by Rodrigo Herrera Camus
The blue compact dwarf galaxy I Zw18 is one of the most metal poor systems in the local Universe, with a nebular metallicity of 12 + log(O/H) = 7.2. Because of this, I Zw18 can provide crucial information about the relation between dust-to-gas mass ratio and metallicity in galaxies. In this work we use Spitzer MIPS observations at 70 and 160 micrometer combined with empirical fits from Muñoz-Mateos et al. (2009) to Draine et al. (2007) dust emission models to derive a dust mass upper limit for I Zw 18 of M_Dust = 3 * 10^4 solar masses and a upper limit to the dust-to-gas mass ratio of M_Dust / M_gas = 9.1 * 10^{-4} (3 sigma limits). This upper limit for the dust-to-gas mass ratio is similar to the Milky Way value after scaling by their respective metallicities, and suggests that a linear scaling law could be compatible with metal-poor systems. The upper limit to the dust mass is driven by the confusion limit of Spitzer at 160 micrometer, and we expect it to be significantly improved by future Herschel observations.
Relevant papers
"Dust in I Zw 18 from Hubble Space Telescope Narrowband Imaging" Cannon et al. 2002
"Dust in the Extremely Metal-Poor Blue Compact Dwarf Galaxy I Zw 18: The Spitzer Mid-infrared View" Wu et al. 2007
Talk slides
pdf
The blue compact dwarf galaxy I Zw18 is one of the most metal poor systems in the local Universe, with a nebular metallicity of 12 + log(O/H) = 7.2. Because of this, I Zw18 can provide crucial information about the relation between dust-to-gas mass ratio and metallicity in galaxies. In this work we use Spitzer MIPS observations at 70 and 160 micrometer combined with empirical fits from Muñoz-Mateos et al. (2009) to Draine et al. (2007) dust emission models to derive a dust mass upper limit for I Zw 18 of M_Dust = 3 * 10^4 solar masses and a upper limit to the dust-to-gas mass ratio of M_Dust / M_gas = 9.1 * 10^{-4} (3 sigma limits). This upper limit for the dust-to-gas mass ratio is similar to the Milky Way value after scaling by their respective metallicities, and suggests that a linear scaling law could be compatible with metal-poor systems. The upper limit to the dust mass is driven by the confusion limit of Spitzer at 160 micrometer, and we expect it to be significantly improved by future Herschel observations.
Relevant papers
"Dust in I Zw 18 from Hubble Space Telescope Narrowband Imaging" Cannon et al. 2002
"Dust in the Extremely Metal-Poor Blue Compact Dwarf Galaxy I Zw 18: The Spitzer Mid-infrared View" Wu et al. 2007
Talk slides
Friday, April 1, 2011
The VLT-FLAMES Tarantula survey of Massive Stars
Abstract
This survey is an ESO Large Programme that has obtained multi-epoch optical spectroscopy of over 800 massive stars in the 30 Doradus region of the Large Magellanic Cloud. It is by far the largest homogeneous spectroscopic study of extragalactic early-type stars undertaken to date. The 30 Dor region is the only ‘super star-cluster’ at a well-known distance in which individual objects can be resolved spatially in optical light. This makes it the perfect target for the comprehensive studies required to address some of the fundamental questions that remain in our understanding of massive-star evolution, relying on the analysis of a statistically-significant and unbiased sample. Authors Danny Lennon, Selma E. de Mink, and Nolan Walborn will lead the discussion.
Relevant Papers
"The VLT-FLAMES Tarantula Survey I: Introduction and observational overview" Evans et al. 2011
"The VLT-FLAMES Tarantula Survey II: R139 revealed as a massive binary system" Taylor et al. 2011
This survey is an ESO Large Programme that has obtained multi-epoch optical spectroscopy of over 800 massive stars in the 30 Doradus region of the Large Magellanic Cloud. It is by far the largest homogeneous spectroscopic study of extragalactic early-type stars undertaken to date. The 30 Dor region is the only ‘super star-cluster’ at a well-known distance in which individual objects can be resolved spatially in optical light. This makes it the perfect target for the comprehensive studies required to address some of the fundamental questions that remain in our understanding of massive-star evolution, relying on the analysis of a statistically-significant and unbiased sample. Authors Danny Lennon, Selma E. de Mink, and Nolan Walborn will lead the discussion.
Relevant Papers
"The VLT-FLAMES Tarantula Survey I: Introduction and observational overview" Evans et al. 2011
"The VLT-FLAMES Tarantula Survey II: R139 revealed as a massive binary system" Taylor et al. 2011
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