Volumetric star formation prescriptions in vertically resolved edge-on galaxies

Kijeong Yim, Tony Wong, Richard J. Rand, Eva Schinnerer

Research output: Contribution to journalArticlepeer-review


We measure the gas disc thicknesses of the edge-on galaxy NGC 4013 and the less edge-on galaxies (NGC 4157 and 5907) using CO (CARMA/OVRO) and/or HI (EVLA) observations. We also estimate the scale heights of stars and/or the star formation rate (SFR) for our sample of five galaxies using Spitzer IR data (3.6 and 24 μm).We derive the average volume densities of the gas and the SFR using the measured scale heights along with radial surface density profiles. Using the volume density that is more physically relevant to the SFR than the surface density, we investigate the existence of a volumetric star formation law (SFL), how the volumetric SFL is different from the surface-density SFL, and how the gas pressure regulates the SFR based on our galaxy sample. We find that the volumetric and surface SFLs in terms of the total gas have significantly different slopes, while the volumetric and surface SFLs in terms of the molecular gas do not show any noticeable difference. The volumetric SFL for the total gas has a flatter power-law slope of 1.26 with a smaller scatter of 0.19 dex compared to the slope (2.05) and the scatter (0.25 dex) of the surface SFL. The molecular gas SFLs have similar slopes of 0.78 (volume density) and 0.77 (surface density) with similar rms scatters. We show that the interstellar gas pressure is strongly correlated with the SFR but find no significant difference between the correlations based on the volume and surface densities.

Original languageEnglish (US)
Pages (from-to)4558-4575
Number of pages18
JournalMonthly Notices of the Royal Astronomical Society
Issue number3
StatePublished - 2020


  • Galaxies: ISM- galaxies: kinematics and dynamics
  • Galaxies: individual (NGC 891, NGC 4013, NGC 4157, NGC 4565, NGC 5907)
  • Galaxies: star formation
  • Galaxies: structure.

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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