Galaxy Evolution

Distributions of Stars and Dust

Measuring the distribution of stars and dust in galaxies throughout cosmic time is critical for understanding their evolution. We constructed stellar population and dust maps of star-forming galaxies at z~2 using resolved imaging from the CANDELS/3D-HST surveys and emission line measurements from the MOSDEF survey. In Fetherolf et al. (2020), we highlight using a modified Voronoi binning technique to create our resolved maps that constructs resolved elements from multiple high S/N filters. We found that a single-filter approach produces lower S/N resolved elements and causes E(B-V) measurements to be systematically redder due to the poorly constrained UV photometry.

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Reddening & SFR Discrepancies

Generally, different indicators for SFR agree, but some studies have found that both reddening and SFRs measured from nebular emission lines (such as Hɑ and Hβ) are systematically higher than those inferred from the UV continuum in z~2 star-forming galaxies. In Fetherolf et al. (2021), we investigated whether aperture effects could be at fault by minimizing assumptions (i.e., removing slit-loss corrections) when comparing Hɑ and UV SFRs, but found that the discrepancy persisted. Alternatively, we suggested that the differences between reddening and SFRs probed from nebular emission and the stellar continuum could be related to patchy dust distributions in the ISM of galaxies. Our investigation also revealed that Hɑ SFRs may be higher in the centers of large galaxies, which could be indicative of inside-out galaxy growth in z~2 star-forming galaxies.

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Morphology of the Dusty ISM

The Patchiness Metric

The Patchiness metric measures how much individual elements (i.e., pixels or bins) deviate from the average of a resolved distribution. Patchiness can be used on any resolved distribution and is sensitive to both high and low outliers, whereas other morphology metrics typically focus on high outliers (such as regions of high flux).

Quantifying galaxy structure is an important tool for understanding how galaxy morphology changes over cosmic time. In Fetherolf et al. (2022, submitted), we utilized a new morphology metric, called "Patchiness," alongside the Gini and M20 coefficients to quantify the resolved reddening distribution of z~2 star-forming galaxies. We found that the dust distribution progresses from smooth to patchy as galaxies increase in stellar mass.

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