The MOSDEF survey: probing resolved stellar populations at z ∼ 2 Using a new bayesian-defined morphology metric called patchiness

Tara Fetherolf, Naveen A. Reddy, Alice E. Shapley, Mariska Kriek, Brian Siana, Alison L. Coil, Bahram Mobasher, William R. Freeman, Sedona H. Price, Ryan L. Sanders, Irene Shivaei, Mojegan Azadi, Laura de Groot, Gene C.K. Leung, Tom O. Zick

Research output: Contribution to journalArticlepeer-review

2 Scopus citations


We define a new morphology metric called ‘patchiness’ (P) that is sensitive to deviations from the average of a resolved distribution, does not require the galaxy centre to be defined, and can be used on the spatially resolved distribution of any galaxy property. While the patchiness metric has a broad range of applications, we demonstrate its utility by investigating the distribution of dust in the interstellar medium (ISM) of 310 star-forming galaxies at spectroscopic redshifts 1.36 < z < 2.66 observed by the MOSFIRE Deep Evolution Field survey. The stellar continuum reddening distribution, derived from high-resolution multiwaveband CANDELS/3D-HST imaging, is quantified using the patchiness, Gini, and M20 coefficients. We find that the reddening maps of high-mass galaxies, which are dustier and more metal-rich on average, tend to exhibit patchier distributions (high P) with the reddest components concentrated within a single region (low M20). Our results support a picture where dust is uniformly distributed in low-mass galaxies (≲1010 M), implying efficient mixing of dust throughout the ISM. On the other hand, the dust distribution is patchier in high-mass galaxies (≳1010 M). Dust is concentrated near regions of active star formation and dust mixing time-scales are expected to be longer in high-mass galaxies, such that the outskirt regions of these physically larger galaxies remain relatively unenriched. This study presents direct evidence for patchy dust distributions on scales of a few kpc in high-redshift galaxies, which previously has only been suggested as a possible explanation for the observed differences between nebular and stellar continuum reddening, star formation rate indicators, and dust attenuation curves.

Original languageEnglish
Pages (from-to)4214-4237
Number of pages24
JournalMonthly Notices of the Royal Astronomical Society
Issue number3
StatePublished - Jan 1 2023

Bibliographical note

Publisher Copyright:
© 2022 The Author(s) Published by Oxford University Press on behalf of Royal Astronomical Society.


  • dust, extinction
  • galaxies: ISM
  • galaxies: evolution
  • galaxies: high-redshift
  • galaxies: structure
  • methods: data analysis

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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