Evolution of z~2 Galaxies on Resolved Scales Using CANDELS/3D-HST Imaging and Emission Line Spectroscopy From the MOSDEF Survey
- Author(s): Fetherolf, Tara;
- Advisor(s): Reddy, Naveen A;
- et al.
Studying the resolved structure of high-redshift galaxies can give insight into the evolution of galaxy properties. The resolved distribution of stars and the interstellar dust obscuring their light can be probed using stellar population maps, which are derived from resolved images of galaxies. I use emission line spectroscopy from the MOSFIRE Deep Evolution Field (MOSDEF) survey combined with CANDELS/3D-HST high-resolution imaging to create resolved stellar population and reddening maps for ~300 star-forming MOSDEF galaxies at z~2. In the construction of my maps, I incorporate a more precise methodology that negates systematic biases towards dustier measurements compared to previous methodologies.
The focus of my dissertation is to understand how star formation may influence complex geometries of dust within galaxies. Uniform coverage of dust in front of the stars has typically been assumed, but some studies have revealed that instead a two-component dust model is more appropriate with higher obscuration caused by dust towards star-forming regions. To avoid assumptions made when correcting for spectroscopic slit-loss, I directly compare the MOSDEF spectroscopic measurements to the photometric measurements within the area encompassed by the spectroscopic slit placement. My results indicate that the relative optical-to-ultraviolet star-formation rate ratio is higher in the centers of large galaxies compared to their outskirts, which may imply that highly star-forming galaxies have patchier dust distributions.
Previously, resolved galaxy structure has been quantified based on their light distributions from the resolved imaging. I devise a new and more general metric, called "patchiness," that is sensitive to any deviations from the average and use it to directly probe the distribution of physical properties in galaxies. This patchiness metric is used alongside two previously established measures in order to interpret the complex geometries of the dust and stars within galaxies. My results reveal how the dustiness within galaxies changes as galaxies grow, transitioning from mostly uniform coverage to the two-component model with regions of higher obscuration. Overall, my dissertation work addresses how star-forming galaxies evolve on both resolved and unresolved scales, particularly at high redshifts when star-formation activity was at its highest.