Kiloparsec-scale Properties of Emission-line Galaxies

Abstract

We perform a detailed study of the resolved properties of emission-line galaxies at kiloparsec scales to investigate how small-scale and global properties of galaxies are related. We use a sample of 119 galaxies in the GOODS fields. The galaxies are selected to cover a wide range in morphologies over the redshift range 0.2 < z < 1.3. High resolution spectroscopic data from Keck/DEIMOS observations are used to fix the redshift of all the galaxies in our sample. Using the HST/ACS and HST/WFC3 imaging data taken as a part of the CANDELS project, for each galaxy, we perform spectral energy distribution fitting per resolution element, producing resolved rest-frame U - V color, stellar mass, star formation rate (SFR), age, and extinction maps. We develop a technique to identify "regions" of statistical significance within individual galaxies, using their rest-frame color maps to select red and blue regions, a broader definition for what are called "clumps" in other works. As expected, for any given galaxy, the red regions are found to have higher stellar mass surface densities and older ages compared to the blue regions. Furthermore, we quantify the spatial distribution of red and blue regions with respect to both redshift and stellar mass, finding that the stronger concentration of red regions toward the centers of galaxies is not a significant function of either redshift or stellar mass. We find that the "main sequence" of star-forming galaxies exists among both red and blue regions inside galaxies, with the median of blue regions forming a tighter relation with a slope of 1.1±0.1 and a scatter of ~0.2 dex compared to red regions with a slope of 1.3±0.1 and a scatter of ~0.6 dex. The blue regions show higher specific SFRs (sSFRs) than their red counterparts with the sSFR decreasing since z ~ 1, driven primarily by the stellar mass surface densities rather than the SFRs at a given resolution element.

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