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When did the initial mass function become bottom-heavy?
- Source :
- Monthly Notices of the Royal Astronomical Society. 509:1959-1984
- Publication Year :
- 2021
- Publisher :
- Oxford University Press (OUP), 2021.
-
Abstract
- The characteristic mass that sets the peak of the stellar initial mass function (IMF) is closely linked to the thermodynamic behaviour of interstellar gas, which controls how gas fragments as it collapses under gravity. As the Universe has grown in metal abundance over cosmic time, this thermodynamic behaviour has evolved from a primordial regime dominated by the competition between compressional heating and molecular hydrogen cooling to a modern regime where the dominant process in dense gas is protostellar radiation feedback, transmitted to the gas by dust-gas collisions. In this paper we map out the primordial-to-modern transition by constructing a model for the thermodynamics of collapsing, dusty gas clouds at a wide range of metallicities. We show the transition from the primordial regime to the modern regime begins at metallicity $Z\sim 10^{-4} \rm{Z_\odot}$, passes through an intermediate stage where metal line cooling is dominant at $Z \sim 10^{-3}\,\rm{Z_{\odot}}$, and then transitions to the modern dust- and feedback-dominated regime at $Z\sim 10^{-2} \rm{Z_\odot}$. In low pressure environments like the Milky Way, this transition is accompanied by a dramatic change in the characteristic stellar mass, from $\sim 50\,\rm{M_\odot}$ at $Z \sim 10^{-6}\,\rm{Z_{\odot}}$ to $\sim 0.3\,\rm{M_\odot}$ once radiation feedback begins to dominate, which marks the appearance of the modern bottom-heavy Milky Way IMF. In the high pressure environments typical of massive elliptical galaxies, the characteristic mass for the modern, dust-dominated regime falls to $\sim 0.1\,\rm{M_{\odot}}$, thus providing an explanation for the more bottom-heavy IMF observed in these galaxies. We conclude that metallicity is a key driver of variations in the characteristic stellar mass, and by extension, the IMF.<br />26 pages (main result in figures 7 and 8). MNRAS in press
- Subjects :
- Cosmology and Nongalactic Astrophysics (astro-ph.CO)
Initial mass function
Stellar mass
Milky Way
Metallicity
Population
FOS: Physical sciences
Astrophysics::Cosmology and Extragalactic Astrophysics
Astrophysics
01 natural sciences
0103 physical sciences
Astrophysics::Solar and Stellar Astrophysics
education
010303 astronomy & astrophysics
Solar and Stellar Astrophysics (astro-ph.SR)
Astrophysics::Galaxy Astrophysics
Line (formation)
Physics
education.field_of_study
010308 nuclear & particles physics
Astronomy and Astrophysics
Astrophysics - Astrophysics of Galaxies
Galaxy
Astrophysics - Solar and Stellar Astrophysics
Space and Planetary Science
Astrophysics of Galaxies (astro-ph.GA)
Elliptical galaxy
Astrophysics::Earth and Planetary Astrophysics
Astrophysics - Cosmology and Nongalactic Astrophysics
Subjects
Details
- ISSN :
- 13652966 and 00358711
- Volume :
- 509
- Database :
- OpenAIRE
- Journal :
- Monthly Notices of the Royal Astronomical Society
- Accession number :
- edsair.doi.dedup.....a9855d598aa13c005152e82684657256