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Open Access Publications from the University of California

Morphological Analysis of Galaxies in the CANDELS Fields

  • Author(s): DeGroot, Laura Michelle
  • Advisor(s): Mobasher, Bahram
  • et al.

Knowledge of the morphology of galaxies is essential in studying galaxy formation and evolution. When combined with other observable characteristics, a detailed understanding of the properties of galaxies can be acquired. In this study, I analyze parametric morphology using the code GALFIT of two galaxy samples in the CANDELS fields by applying a single Sérsic function and a two-component fit to the surface brightness distribution of the galaxies. I quantify morphological properties, such as galaxy Sérsic index, bulge-to-total flux ratio, and size to study the evolution and correlation with other galaxy properties. When my parametric measurements are compared with non-parametric techniques, such as the Gini-M20 diagram, I find that the different methods show overall agreement.

I find that galaxies selected with MIPS 24 μm detection, characteristic of dusty, star-forming galaxies, in the GOODS-S field are primarily disk galaxies with a range of bulge fractions, although some galaxies with elliptical profiles are present. Many of these galaxies have AGN candidates, another source of 24 μm emission, while the remaining elliptical galaxies could contain obscured AGN. In comparison, I find that galaxies without 24μm emission are primarily disks but with a larger sample of elliptical galaxies that show an observed evolution is bulge-dominance with redshift.

For galaxies observed in the MOSDEF survey, I find little to no correlation between the relations of SFR-M* and MZR with galaxy n. The star forming main sequence is observed to form a tighter, steeper correlation for galaxies with low B/T than other populations indicating that higher mass, disky galaxies have higher SFRs with smaller bulge fractions. This relation also shows that galaxies with high B/T have much flatter slopes indicating that they may be evolving to quiescence. I examine the necessity for a morphological k-correction when studying morphology across multiple redshifts, and discover that galaxy n and re show wavelength dependence when comparing observed optical and infrared morphologies, while the B/T shows significant scatter in all wavelengths and redshifts. Overall I find that a morphological k-correction is necessary when studying galaxies across a wide redshift range.

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