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Title: The Physical Origin of Long Gas Depletion Times in Galaxies

Abstract

We present a model that explains why galaxies form stars on a timescale significantly longer than the timescales of processes governing the evolution of interstellar gas. We show that gas evolves from a non-star-forming to a star-forming state on a relatively short timescale, and thus the rate of this evolution does not limit the star formation rate (SFR). Instead, the SFR is limited because only a small fraction of star-forming gas is converted into stars before star-forming regions are dispersed by feedback and dynamical processes. Thus, gas cycles into and out of a star-forming state multiple times, which results in a long timescale on which galaxies convert gas into stars. Our model does not rely on the assumption of equilibrium and can be used to interpret trends of depletion times with the properties of observed galaxies and the parameters of star formation and feedback recipes in simulations. In particular, the model explains how feedback self-regulates the SFR in simulations and makes it insensitive to the local star formation efficiency. We illustrate our model using the results of an isolated L {sub *}-sized galaxy simulation that reproduces the observed Kennicutt–Schmidt relation for both molecular and atomic gas. Interestingly, the relation formore » molecular gas is almost linear on kiloparsec scales, although a nonlinear relation is adopted in simulation cells. We discuss how a linear relation emerges from non-self-similar scaling of the gas density PDF with the average gas surface density.« less

Authors:
; ;  [1]
  1. Department of Astronomy and Astrophysics, The University of Chicago, Chicago, IL 60637 (United States)
Publication Date:
OSTI Identifier:
22663220
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 845; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; COSMIC GASES; DENSITY; EFFICIENCY; EQUILIBRIUM; GALAXIES; INTERSTELLAR SPACE; SIMULATION; STAR EVOLUTION; STARS; SURFACES

Citation Formats

Semenov, Vadim A., Kravtsov, Andrey V., and Gnedin, Nickolay Y., E-mail: semenov@uchicago.edu. The Physical Origin of Long Gas Depletion Times in Galaxies. United States: N. p., 2017. Web. doi:10.3847/1538-4357/AA8096.
Semenov, Vadim A., Kravtsov, Andrey V., & Gnedin, Nickolay Y., E-mail: semenov@uchicago.edu. The Physical Origin of Long Gas Depletion Times in Galaxies. United States. doi:10.3847/1538-4357/AA8096.
Semenov, Vadim A., Kravtsov, Andrey V., and Gnedin, Nickolay Y., E-mail: semenov@uchicago.edu. Sun . "The Physical Origin of Long Gas Depletion Times in Galaxies". United States. doi:10.3847/1538-4357/AA8096.
@article{osti_22663220,
title = {The Physical Origin of Long Gas Depletion Times in Galaxies},
author = {Semenov, Vadim A. and Kravtsov, Andrey V. and Gnedin, Nickolay Y., E-mail: semenov@uchicago.edu},
abstractNote = {We present a model that explains why galaxies form stars on a timescale significantly longer than the timescales of processes governing the evolution of interstellar gas. We show that gas evolves from a non-star-forming to a star-forming state on a relatively short timescale, and thus the rate of this evolution does not limit the star formation rate (SFR). Instead, the SFR is limited because only a small fraction of star-forming gas is converted into stars before star-forming regions are dispersed by feedback and dynamical processes. Thus, gas cycles into and out of a star-forming state multiple times, which results in a long timescale on which galaxies convert gas into stars. Our model does not rely on the assumption of equilibrium and can be used to interpret trends of depletion times with the properties of observed galaxies and the parameters of star formation and feedback recipes in simulations. In particular, the model explains how feedback self-regulates the SFR in simulations and makes it insensitive to the local star formation efficiency. We illustrate our model using the results of an isolated L {sub *}-sized galaxy simulation that reproduces the observed Kennicutt–Schmidt relation for both molecular and atomic gas. Interestingly, the relation for molecular gas is almost linear on kiloparsec scales, although a nonlinear relation is adopted in simulation cells. We discuss how a linear relation emerges from non-self-similar scaling of the gas density PDF with the average gas surface density.},
doi = {10.3847/1538-4357/AA8096},
journal = {Astrophysical Journal},
number = 2,
volume = 845,
place = {United States},
year = {Sun Aug 20 00:00:00 EDT 2017},
month = {Sun Aug 20 00:00:00 EDT 2017}
}