3 mai 2012 :
Probing the formation of high redshift (z~1-3) galaxies using spatially resolved colors
par Niraj Welikala (IAS)
Jeudi 3 mai 2012, à 14h, bât. 121, salle 1-2-3
The formation of high redshift (z~1-3) galaxies is a subject of considerable interest and debate. Open questions include whether these objects are formed by mergers or if they are disks formed in-situ and what role the environment of these galaxies plays in the star formation process within these systems. A knowledge of where in these galaxies star formation is concentrated, and how the spatial distribution of star formation within galaxies varies with the galaxy environment can provide important clues to how these objects formed.
I will describe new techniques that use spatially resolved colors within galaxies from high resolution optical and near-infrared imaging in order to probe high-redshift galaxy formation. I use these to measure color gradients in galaxies and to trace how these gradients evolve with cosmic time. I show that galaxies have cores which become increasingly blue at higher redshifts while their outskirts do not show a significant change in color, and I discuss the implications of this finding in terms of the star formation process. I also present a method for deriving properties of stellar populations (such as star formation rates) from the colors of individual pixels in galaxy images. I apply this method to high-redshift galaxies in order to make detailed studies of substructure in these objects, including (a) radial gradients of age, star formation rate and dust and (b) the distribution of these properties within spiral arms and clumps.
Finally, these internal color variations in high-z galaxies are also important in the context of cosmology. I discuss how they could potentially bias the shape measurements of galaxies that will be made in upcoming weak lensing surveys.
par Niraj Welikala (IAS)
Jeudi 3 mai 2012, à 14h, bât. 121, salle 1-2-3
The formation of high redshift (z~1-3) galaxies is a subject of considerable interest and debate. Open questions include whether these objects are formed by mergers or if they are disks formed in-situ and what role the environment of these galaxies plays in the star formation process within these systems. A knowledge of where in these galaxies star formation is concentrated, and how the spatial distribution of star formation within galaxies varies with the galaxy environment can provide important clues to how these objects formed.
I will describe new techniques that use spatially resolved colors within galaxies from high resolution optical and near-infrared imaging in order to probe high-redshift galaxy formation. I use these to measure color gradients in galaxies and to trace how these gradients evolve with cosmic time. I show that galaxies have cores which become increasingly blue at higher redshifts while their outskirts do not show a significant change in color, and I discuss the implications of this finding in terms of the star formation process. I also present a method for deriving properties of stellar populations (such as star formation rates) from the colors of individual pixels in galaxy images. I apply this method to high-redshift galaxies in order to make detailed studies of substructure in these objects, including (a) radial gradients of age, star formation rate and dust and (b) the distribution of these properties within spiral arms and clumps.
Finally, these internal color variations in high-z galaxies are also important in the context of cosmology. I discuss how they could potentially bias the shape measurements of galaxies that will be made in upcoming weak lensing surveys.