Abstract by Christa Gall
Dust plays an essential role in the formation of stars and evolution of galaxies. Large amounts of dust detected in sub-millimeter galaxies and quasars at high redshift, bear witness of a rapid production of dust. Massive stars ending their lives as either asymptotic giant branch stars or supernovae have been contemplated as the prime sources of dust, but it is uncertain whether their dust production efficiency is sufficient to account for the large dust masses observed. I shall address the challenge of determining dust masses observationally and discuss the contribution of stellar dust sources to the dust budget in the high redshift universe as well as in Local Group galaxies.
Friday, October 26, 2012
Monday, October 15, 2012
Friday October 19th: Counting Milky Way M-dwarfs in WFC3 surveys
Abstract by Benne Holwerda
Counting stars is one of the oldest techniques to determine the shape and size of the Milky Way. Long the realm of bright stars, the discovery space in deep WFC3 imaging of the high-redshift Universe covers the same luminosity and color ranges that probe dwarf stars belonging to our own Milky Way.
The BoRG pure-parallel WFC3 survey probes many lines-of-sight out of our own Galaxy with four filters. I present a way to identify the stars in this survey, and calibrate their spectral type from the colors. The ultimate goal is to characterize the shape and size of the components of the Milky Way (thin and thick disk, possible the spheroid) using these bona-fide M-dwarf stars.
Counting stars is one of the oldest techniques to determine the shape and size of the Milky Way. Long the realm of bright stars, the discovery space in deep WFC3 imaging of the high-redshift Universe covers the same luminosity and color ranges that probe dwarf stars belonging to our own Milky Way.
The BoRG pure-parallel WFC3 survey probes many lines-of-sight out of our own Galaxy with four filters. I present a way to identify the stars in this survey, and calibrate their spectral type from the colors. The ultimate goal is to characterize the shape and size of the components of the Milky Way (thin and thick disk, possible the spheroid) using these bona-fide M-dwarf stars.
Friday October 12th: Informal discussion on SN2009ip
SN2009ip, Luminous Blue Variable or actual Super Nova Type II?
In July of this year a new outburst of SN2009ip was discovered. There has been important discussion among the field on whether this object has indeed become a Core-Colapse Super Nova Type II or not. If you are interested I suggest to read the following papers... they are fun to read, so enjoy!
Jon C. Mauerhan, Nathan Smith, Alexei Filippenko, Kyle Blanchard, Peter Blanchard, Chadwick F. E. Casper, S. Bradley Cenko, Kelsey I. Clubb, Daniel Cohen, Gary Li, & Jeffrey M. Silverman
http://arxiv.org/abs/1209.6320
J. L. Prieto, J. Brimacombe, A. J. Drake, & S. Howerton
http://arxiv.org/abs/1210.3347
In July of this year a new outburst of SN2009ip was discovered. There has been important discussion among the field on whether this object has indeed become a Core-Colapse Super Nova Type II or not. If you are interested I suggest to read the following papers... they are fun to read, so enjoy!
Jon C. Mauerhan, Nathan Smith, Alexei Filippenko, Kyle Blanchard, Peter Blanchard, Chadwick F. E. Casper, S. Bradley Cenko, Kelsey I. Clubb, Daniel Cohen, Gary Li, & Jeffrey M. Silverman
http://arxiv.org/abs/1209.6320
J. L. Prieto, J. Brimacombe, A. J. Drake, & S. Howerton
http://arxiv.org/abs/1210.3347
Tuesday, September 4, 2012
Friday September 14th: The origin and ages of the most massive stars - how stellar evolution shapes the mass function
Abstract by Fabian Schneider
The stellar initial mass function (IMF) is the distribution of stellar masses at birth and thus governs observable properties of stellar systems, supernova rates and predicts the outcome of star formation. Contrary, the present day mass function (PDMF) is the stellar mass distribution today, i.e. it is given by the IMF and subsequent evolutionary effects changing stellar masses and their frequencies. One way to change stellar masses is by single and binary star evolution which we investigate here to learn from observed PDMFs about the evolutionary status of stellar samples. To that end we model populations of massive single and binary stars with a rapid binary evolution code and follow their mass functions in time. Stellar wind mass loss, mass transfer because of Roche lobe overflow, stellar mergers and rejuvenation shape the PDMF at the high mass end. From this shape it is possible to determine the age of star clusters and to identify the products of binary evolution. The determination of the stellar upper-mass limit and ages of star clusters based on the most massive stars are thus biased by binary interactions. We apply our findings to the PDMFs of the Arches and Quintuplet clusters and find that their most massive stars are probably the rejuvenated remnants of binary evolution. We conclude that binary star evolution must be taken into account to better understand the stellar content and the formation of star clusters.
The stellar initial mass function (IMF) is the distribution of stellar masses at birth and thus governs observable properties of stellar systems, supernova rates and predicts the outcome of star formation. Contrary, the present day mass function (PDMF) is the stellar mass distribution today, i.e. it is given by the IMF and subsequent evolutionary effects changing stellar masses and their frequencies. One way to change stellar masses is by single and binary star evolution which we investigate here to learn from observed PDMFs about the evolutionary status of stellar samples. To that end we model populations of massive single and binary stars with a rapid binary evolution code and follow their mass functions in time. Stellar wind mass loss, mass transfer because of Roche lobe overflow, stellar mergers and rejuvenation shape the PDMF at the high mass end. From this shape it is possible to determine the age of star clusters and to identify the products of binary evolution. The determination of the stellar upper-mass limit and ages of star clusters based on the most massive stars are thus biased by binary interactions. We apply our findings to the PDMFs of the Arches and Quintuplet clusters and find that their most massive stars are probably the rejuvenated remnants of binary evolution. We conclude that binary star evolution must be taken into account to better understand the stellar content and the formation of star clusters.
Restart of the Journal Club this 2012 Fall
The Massive Stars and Starburst Journal Club will restart next week, September Friday 14th at same time (1pm) and at the usual place (CafeCon at STScI)
Our first talk will be "The origin and ages of the most massive stars - how stellar evolution shapes the mass function" by Fabian Scheider (Argelander Institut für Astronomie, Germany)
Our first talk will be "The origin and ages of the most massive stars - how stellar evolution shapes the mass function" by Fabian Scheider (Argelander Institut für Astronomie, Germany)
Friday, April 27, 2012
A steep IMF in luminous early-type galaxies
Paper is in prep...
Background papers
"A substantial population of low-mass stars in luminous elliptical galaxies"
"Confirmation of Enhanced Dwarf-sensitive Absorption Features in the Spectra of Massive Elliptical Galaxies: Further Evidence for a Non-universal Initial Mass Function"
"Counting Low-mass Stars in Integrated Light"
"A systematic variation of the stellar initial mass function in early-type galaxies"
"Variations in the Stellar IMF: from Bottom to Top"
Background papers
"A substantial population of low-mass stars in luminous elliptical galaxies"
"Confirmation of Enhanced Dwarf-sensitive Absorption Features in the Spectra of Massive Elliptical Galaxies: Further Evidence for a Non-universal Initial Mass Function"
"Counting Low-mass Stars in Integrated Light"
"A systematic variation of the stellar initial mass function in early-type galaxies"
"Variations in the Stellar IMF: from Bottom to Top"
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