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Title: THE PRESSURE OF THE STAR-FORMING INTERSTELLAR MEDIUM IN COSMOLOGICAL SIMULATIONS

We examine the pressure of the star-forming interstellar medium (ISM) of Milky-Way-sized disk galaxies using fully cosmological SPH+N-body, high-resolution simulations. These simulations include explicit treatment of metal-line cooling in addition to dust and self-shielding, H{sub 2}-based star formation. The four simulated halos have masses ranging from a few times 10{sup 10} to nearly 10{sup 12} solar masses. Using a kinematic decomposition of these galaxies into present-day bulge and disk components, we find that the typical pressure of the star-forming ISM in the present-day bulge is higher than that in the present-day disk by an order of magnitude. We also find that the pressure of the star-forming ISM at high redshift is, on average, higher than ISM pressures at low redshift. This explains why the bulge forms at higher pressures: the disk assembles at lower redshift when the ISM exhibits lower pressure and the bulge forms at high redshift when the ISM has higher pressure. If ISM pressure and IMF variation are tied together, these results could indicate a time-dependent IMF in Milky-Way-like systems as well as a different IMF in the bulge and the disk.
Authors:
; ;  [1] ;  [2] ;  [3] ;  [4] ;  [5]
  1. Department of Astronomy, University of Washington, Seattle, WA (United States)
  2. Department Astronomy, University of Arizona, 933 North Cherry Avenue, Rm. N204, Tucson, AZ 85721 (United States)
  3. Department of Physics and Astronomy, McMaster University, Hamilton, ON (Canada)
  4. Department of Astronomy, University of Michigan, 500 Church Street, Ann Arbor, MI 48109 (United States)
  5. Department of Astronomy, University of California, Santa Cruz, 1156 High Street, ISB Bldg Room 211, Santa Cruz, CA 95064 (United States)
Publication Date:
OSTI Identifier:
22365871
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal Letters; Journal Volume: 781; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; COSMIC DUST; HYDROGEN; INTERSTELLAR SPACE; MASS; METALS; MILKY WAY; RED SHIFT; RESOLUTION; SELF-SHIELDING; STAR EVOLUTION; STARS; TIME DEPENDENCE; VARIATIONS