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A new view of the size-mass distribution of galaxies : using r20 and r80 Instead of r50

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Abstract
When investigating the sizes of galaxies it is standard practice to use the half-light radius, r(50). Here we explore the effects of the size definition on the distribution of galaxies in the size-stellar mass plane. Specifically, we consider r(20) and r(80), the radii that contain 20% and 80% of a galaxy's total luminosity, as determined from a Sersic profile fit, for galaxies in the 3D-HST/CANDELS and COSMOS-DASH surveys. These radii are calculated from size catalogs based on a simple calculation assuming a Sersic profile. We find that the size-mass distributions for r(20) and r(80) are markedly different from each other and also from the canonical r(50) distribution. The most striking difference is in the relative sizes of star-forming and quiescent galaxies at fixed stellar mass. Whereas quiescent galaxies are smaller than star-forming galaxies in r(50), this difference nearly vanishes for r(80). By contrast, the distance between the two populations increases for r(20). Considering all galaxies in a given stellar mass and redshift bin we detect a significant bimodality in the distribution of r(20), with one peak corresponding to star-forming galaxies and the other to quiescent galaxies. We suggest that different measures of the size are tracing different physical processes within galaxies; r(20) is closely related to processes controlling the star formation rate of galaxies and r(80) may be sensitive to accretion processes and the relation of galaxies with their halos.
Keywords
COLOR, EVOLUTION, CAMERA, galaxies: fundamental parameters, galaxies: high-redshift, galaxies: structure

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MLA
Miller, Tim B et al. “A New View of the Size-mass Distribution of Galaxies : Using R20 and R80 Instead of R50.” ASTROPHYSICAL JOURNAL LETTERS 872.1 (2019): n. pag. Print.
APA
Miller, T. B., van Dokkum, P., Mowla, L., & van der Wel, A. (2019). A new view of the size-mass distribution of galaxies : using r20 and r80 Instead of r50. ASTROPHYSICAL JOURNAL LETTERS, 872(1).
Chicago author-date
Miller, Tim B, Pieter van Dokkum, Lamiya Mowla, and Arjen van der Wel. 2019. “A New View of the Size-mass Distribution of Galaxies : Using R20 and R80 Instead of R50.” Astrophysical Journal Letters 872 (1).
Chicago author-date (all authors)
Miller, Tim B, Pieter van Dokkum, Lamiya Mowla, and Arjen van der Wel. 2019. “A New View of the Size-mass Distribution of Galaxies : Using R20 and R80 Instead of R50.” Astrophysical Journal Letters 872 (1).
Vancouver
1.
Miller TB, van Dokkum P, Mowla L, van der Wel A. A new view of the size-mass distribution of galaxies : using r20 and r80 Instead of r50. ASTROPHYSICAL JOURNAL LETTERS. 2019;872(1).
IEEE
[1]
T. B. Miller, P. van Dokkum, L. Mowla, and A. van der Wel, “A new view of the size-mass distribution of galaxies : using r20 and r80 Instead of r50,” ASTROPHYSICAL JOURNAL LETTERS, vol. 872, no. 1, 2019.
@article{8620693,
  abstract     = {When investigating the sizes of galaxies it is standard practice to use the half-light radius, r(50). Here we explore the effects of the size definition on the distribution of galaxies in the size-stellar mass plane. Specifically, we consider r(20) and r(80), the radii that contain 20% and 80% of a galaxy's total luminosity, as determined from a Sersic profile fit, for galaxies in the 3D-HST/CANDELS and COSMOS-DASH surveys. These radii are calculated from size catalogs based on a simple calculation assuming a Sersic profile. We find that the size-mass distributions for r(20) and r(80) are markedly different from each other and also from the canonical r(50) distribution. The most striking difference is in the relative sizes of star-forming and quiescent galaxies at fixed stellar mass. Whereas quiescent galaxies are smaller than star-forming galaxies in r(50), this difference nearly vanishes for r(80). By contrast, the distance between the two populations increases for r(20). Considering all galaxies in a given stellar mass and redshift bin we detect a significant bimodality in the distribution of r(20), with one peak corresponding to star-forming galaxies and the other to quiescent galaxies. We suggest that different measures of the size are tracing different physical processes within galaxies; r(20) is closely related to processes controlling the star formation rate of galaxies and r(80) may be sensitive to accretion processes and the relation of galaxies with their halos.},
  articleno    = {L14},
  author       = {Miller, Tim B and van Dokkum, Pieter and Mowla, Lamiya and van der Wel, Arjen},
  issn         = {2041-8205},
  journal      = {ASTROPHYSICAL JOURNAL LETTERS},
  keywords     = {COLOR,EVOLUTION,CAMERA,galaxies: fundamental parameters,galaxies: high-redshift,galaxies: structure},
  language     = {eng},
  number       = {1},
  pages        = {6},
  title        = {A new view of the size-mass distribution of galaxies : using r20 and r80 Instead of r50},
  url          = {http://dx.doi.org/10.3847/2041-8213/ab0380},
  volume       = {872},
  year         = {2019},
}

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