Shear Regulation of Star Formation Efficiency in Nearby Galaxies

• Author / Creator

  Nofech, Joseph

• We use 7m ALMA CO(2-1) observations from the Physics at High Angular resolution in Nearby GalaxieS (PHANGS) survey combined with ultraviolet+infrared star formation rate (SFR) data from the z=0 Multiwavelength Galaxy Synthesis (z0MGS) project to measure the relationship between molecular depletion time and rotational shear at 750 pc resolution. In addition to this main analysis, we use the available data to test a number of proposed star formation models. This is performed for 55 galaxies, the largest uniform sample of SFRs and molecular gas observations to date. Galaxy parameters are optimized by fitting CO(2-1) velocity centroid maps to a "flat disk" model using the DISKFIT software. These fits are used to produce smooth analytic fits to the universal rotation curve model for each galaxy, which are then used to measure shear.
  Overall, despite having a very large homogeneous sample of molecular gas and star formation data, we do not find substantial evidence for the influence of shear on star formation rate; nor do our data exhibit clear support for any of the proposed star formation models.
  However, we note that while some key quantities do not display a correlation overall (such as depletion time and shear), weak correlations and anticorrelations of high statistical significance are still observed across many individual galaxies in our sample. This strongly suggests that there may be some common underlying factor(s) influencing the behaviour of these quantities.

• Subjects / Keywords

  • galaxies: ISM
  • galaxies: kinematics and dynamics
  • galaxies: evolution
  • stars: formation
  • astrophysics

• Graduation date

  Fall 2019

• Type of Item

  Thesis

• Degree

  Master of Science

• DOI

  https://doi.org/10.7939/r3-5ddb-yk48

• License

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