Abstract by Ching-Wa Yip
Star formation is one of the most important processes in galaxy formation. The luminosity of Hα recombination and [O II]λ3728 forbidden emissions re- main to be most used in measuring formation rate of massive stars in galax- ies. Here we report the inclination dependency of continuum-subtracted and aperture-corrected nebular luminosities, including Hα, Hβ, Hγ, [O II], [N II], of disk-dominated galaxies in the local universe. Their luminosities decrease by a factor of three from face-on to edge-on (axis ratio limit = 0.17) orientations. This dependence is deduced to be caused by extinction due to diffuse dust within the disks with an amplitude of 1.2 mag. The line-luminosity–inclination rela- tion provides a novel way to remove extinction in emission lines and present star formation rate of disk galaxies out to redshift of 1.6.
Relevant Papers
"Extinction in Nebular Luminosities & Star Formation Rate of Disk Galaxies: Inclination Correction"
Yip & Szalay
Tuesday, October 25, 2011
Sunday, October 23, 2011
Nature of Starburst in Local Lyman Break Galaxy Analogs
Abstract by Sanch Borthakur
In this talk, I'll briefly describe the properties of local Lyman
break galaxy analogs (LBAs) and then go on to discuss our COS data for
a sample of LBAs. I'll primarily present our analysis of the spectra
focusing on various transitions in the UV. And finally I'll compare
these spectra with various Starburst99 models to understand the nature
of star formation in these systems.
Relevant Papers
"The Properties of Ultraviolet-luminous Galaxies at the Current Epoch"
Heckman et al. 2005
"Hubble Space Telescope Morphologies of Local Lyman Break Galaxy Analogs. I. Evidence for Starbursts Triggered by Merging"
Overzier et al. 2008
"Morphologies of Local Lyman Break Galaxy Analogs. II. A Comparison with Galaxies at z ~= 2-4 in ACS and WFC3 Images of the Hubble Ultra Deep Field"
Overzier et al. 2010
"Extreme Feedback and the Epoch of Reionization: Clues in the Local Universe"
Heckman et al. 2011
Talk Slides
In this talk, I'll briefly describe the properties of local Lyman
break galaxy analogs (LBAs) and then go on to discuss our COS data for
a sample of LBAs. I'll primarily present our analysis of the spectra
focusing on various transitions in the UV. And finally I'll compare
these spectra with various Starburst99 models to understand the nature
of star formation in these systems.
Relevant Papers
"The Properties of Ultraviolet-luminous Galaxies at the Current Epoch"
Heckman et al. 2005
"Hubble Space Telescope Morphologies of Local Lyman Break Galaxy Analogs. I. Evidence for Starbursts Triggered by Merging"
Overzier et al. 2008
"Morphologies of Local Lyman Break Galaxy Analogs. II. A Comparison with Galaxies at z ~= 2-4 in ACS and WFC3 Images of the Hubble Ultra Deep Field"
Overzier et al. 2010
"Extreme Feedback and the Epoch of Reionization: Clues in the Local Universe"
Heckman et al. 2011
Talk Slides
Monday, October 10, 2011
The Hunt for Massive Stars Hiding in the Milky Way
Abstract by Matthew Povich
The failure to achieve a clear picture of the formation mechanism(s) and properties of massive stars remains one of the most persistent problems in astrophysics. An underlying cause for this lack of clarity is that massive stars are difficult to observe. They are relatively rare, generally located at large (often unknown) heliocentric distances and behind significant extinction. Ironically, simple color-magnitude diagrams yield a far better census of the highest-mass stars in Magellanic Clouds than is possible in the Milky Way, where overwhelming field star contamination conspires with uncertain stellar distances and differential reddening to foil well-intentioned observers. I will discuss the curious case of the missing OB stars in the Great Nebula in Carina, the nearest Galactic analog to extragalactic starburst regions. We have developed a new methodology for identifying candidate luminous stars using X-ray emission and infrared spectral energy distributions. First results from applying this methodology to Carina indicate that the population massive stars in this well-studied region may actually be twice as large as previously thought, with profound implications for the energy budget and stellar initial mass function in the region. I will also highlight the Milky Way Project (http://www.milkywayproject.org), our latest effort to map massive star-forming regions throughout the Galaxy by enlisting >20,000 "citizen scientists" to search Spitzer Space Telescope images for bubbles.
Figure. Image of the central 1° of the Great Nebula in Carina. The color code is blue=visible light (Digitized Sky Survey), green=near-IR (2MASS), and red=8.0 micron mid-IR (Spitzer Space Telescope). Regions that appear blue suffer little obscuration by interstellar dust, while regions that appear red have high obscuration. Previously cataloged massive stars are marked by diamonds, and new candidate massive stars identified by Povich et al. (2011) are marked by circles. Note that the candidate massive stars tend to be found in regions of higher dust obscuration.
Relevant Papers
"Candidate X-ray-emitting OB Stars in the Carina Nebula Identified Via Infrared Spectral Energy Distributions."
Povich et al. 2011
"The Bubbling Galactic Disk"
Churchwell et al. 2006
Talk Slides
pdf
The failure to achieve a clear picture of the formation mechanism(s) and properties of massive stars remains one of the most persistent problems in astrophysics. An underlying cause for this lack of clarity is that massive stars are difficult to observe. They are relatively rare, generally located at large (often unknown) heliocentric distances and behind significant extinction. Ironically, simple color-magnitude diagrams yield a far better census of the highest-mass stars in Magellanic Clouds than is possible in the Milky Way, where overwhelming field star contamination conspires with uncertain stellar distances and differential reddening to foil well-intentioned observers. I will discuss the curious case of the missing OB stars in the Great Nebula in Carina, the nearest Galactic analog to extragalactic starburst regions. We have developed a new methodology for identifying candidate luminous stars using X-ray emission and infrared spectral energy distributions. First results from applying this methodology to Carina indicate that the population massive stars in this well-studied region may actually be twice as large as previously thought, with profound implications for the energy budget and stellar initial mass function in the region. I will also highlight the Milky Way Project (http://www.milkywayproject.org), our latest effort to map massive star-forming regions throughout the Galaxy by enlisting >20,000 "citizen scientists" to search Spitzer Space Telescope images for bubbles.
Figure. Image of the central 1° of the Great Nebula in Carina. The color code is blue=visible light (Digitized Sky Survey), green=near-IR (2MASS), and red=8.0 micron mid-IR (Spitzer Space Telescope). Regions that appear blue suffer little obscuration by interstellar dust, while regions that appear red have high obscuration. Previously cataloged massive stars are marked by diamonds, and new candidate massive stars identified by Povich et al. (2011) are marked by circles. Note that the candidate massive stars tend to be found in regions of higher dust obscuration.
Relevant Papers
"Candidate X-ray-emitting OB Stars in the Carina Nebula Identified Via Infrared Spectral Energy Distributions."
Povich et al. 2011
"The Bubbling Galactic Disk"
Churchwell et al. 2006
Talk Slides
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