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Spiral Arm Sub-Structure in Nearby Galaxies - 2009

Listing of Poster Abstracts

Schmidt Star Formation Law in M33
Dr.  Jonathan Heiner (Université Laval)
We examine the relation between GMC total volume densities and the star formation rate, using the 'PDR method'. This method uses HI produced on the surface of giant molecular clouds to compute total hydrogen volume densities. Additionally, the far-UV luminosity of the OB association nearest to these GMCs provides a measure of the star formation rate. We recover the Schmidt Law and estimate its power law slope, taking into account the observational selection effects.
Exploring the Scaling Laws of Star Formation
Mr.  Guilin Liu (Astronomy Department, University of Massachusetts)
As a variety of surveys of the local and distant Universe are approaching a full census of galaxy populations, our attention needs to turn towards understanding and quantifying the physical mechanisms that trigger and regulate the large-scale star formation rates (SFRs) in galaxies. To shed light on this crucial theme, we carried out an investigation of the spatially resolved Schmidt-Kennicutt law by analysing a sample of 107 galaxy centers. Combining our new (HST-GO 11080; 84 galaxies) and archival HST/NICMOS Paα (1.8756μm) images of the centers of 107 nearby galaxies with their high resolution (~2"-5") interferometric millimetric CO data from BIMA/CARMA, OVRO, NRO and PdBI, we study the form of the virtually extinction-free SFR vs. gas density law in a density and dust extinction regime at least 30 times higher than normally accessible with optical SFR tracers like Hα. This sample covers the full Hubble sequence and all bar types, providing an opportunity of studying the physical properties of star formation with respect to the morphological types. Here we present our early-stage analysis of this thorough investigation of star formation scaling law with the data representing a quality extreme at present.
Effects of non-circular motions on azimuthal color gradients
Dr.  Eric E. Martinez-Garcia (Centro de Investigaciones de Astronomia (CIDA))
Assuming that density waves trigger star formation, and that young stars preserve the velocity components of the molecular gas where they are born, we analyze the effects that non-circular gas orbits have on color gradients across spiral arms.
CARMA STING Survey and Resolved Molecular Star Formation Law in NGC 4254
Dr.  Nurur Rahman (University of Maryland)
An accurate knowledge of star formation law is crucial to make progress in understanding galaxy formation and evolution. We are studying this topic using CARMA STING (Survey Toward Infrared-bright Nearby Galaxies), an interferometric CO survey of a sample of 21 star-forming nearby galaxies with a wealth of multi-wavelength data designed to study star formation in environments throughout the blue sequence at sub-kpc scales. We will present results from our case study on NGC 4254 (M99), one of our sample galaxies. We construct star formation rate surface density and gas (molecular) surface density indicators using a combination of high resolution data from GALEX, KPNO, Spitzer, IRAM, and CARMA. Our results suggest that any study focused on understanding the resolved star formation law of any galaxy is a highly complex issue which depends on various factors such as tracers of star formation, contribution from diffuse background, statistical methodologies etc.

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