The big problems in star formation: The star formation rate, stellar clustering, and the initial mass function

By Mark R. Krumholz. 2014

273 citations recorded by the source corpus.

Abstract Star formation lies at the center of a web of processes that drive cosmic evolution: generation of radiant energy, synthesis of elements, formation of planets, and development of life. Decades of observations have yielded a variety of empirical rules about how it operates, but at present we have no comprehensive, quantitative theory. In this review I discuss the current state of the field of star formation, focusing on three central questions: What controls the rate at which gas in a galaxy converts to stars? What determines how those stars are clustered, and what fraction of the stellar population ends up in gravitationally-bound structures? What determines the stellar initial mass function, and does it vary with star-forming environment? I use these three questions as a lens to introduce the basics of star formation, beginning with a review of the observational phenomenology and the basic physical processes. I then review the status of current theories that attempt to solve each of the three problems, pointing out links between them and opportunities for theoretical and numerical work that crosses the scale between them. I conclude with a discussion of prospects for theoretical progress in the coming years.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/9647039e9157cdb82a067208b13eb2bdffa3b62b

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Citations in the corpus

The lifecycle of molecular clouds in nearby star-forming disc galaxies (2019, background): “…chevance@uni-heidelberg.de posits mass, metals, energy and momentum into the GMCs, eventually leading to their disruption (e.g. Dobbs et al. 2014; Krumholz 2014) and regulating the galaxy-wide star formation rate (SFR; e.g. Ostriker & Shetty 2011; Hayward & Hopkins 2017; Krumholz et al. 2018).”
The dynamical evolution of molecular clouds near the Galactic Centre - I. Orbital structure and evolutionary timeline (2014, background): “Despite its critical mportance, a fundamental physical understanding of star formation has not been achieved (McKee & Ostriker 2007; Kennicutt & Evans 2012; Krumholz 2014).”
On the universality of interstellar filaments: theory meets simulations and observations (2015, background): “…is a key for star formation (Mac Low & Klessen 2004; Elmegreen & Scalo 2004; McKee & Ostriker 2007; Hennebelle & Falgarone 2012; Hopkins 2013; Krumholz 2014; Padoan et al. 2014), so most of our simulations include a turbulence driving module1 that produces turbulence similar to what is…”
A unified model for galactic discs: star formation, turbulence driving, and mass transport (2017, background): “Perhaps the most famous of these is the Kennicutt–Schmidt relation (see reviews by Kennicutt 1998; Kennicutt & Evans 2012; Krumholz 2014), the observed correlation between the rate at which galaxies form stars and a combination of their gas content and their dynamical times.”
Double neutron stars: merger rates revisited (2017, result): “This change was motivated by the observational results of the IMF studies (e.g. Bastian et al. 2010; Offner et al. 2014; Krumholz 2014).”
Physical Processes in the Interstellar Medium (2014, methodology): “…Wilden et al., 2002), implying that the gas out of which these stars formed must have been chemically well-mixed initially, which could provide interesting pathways to better understand turbulent mixing in the ISM (see also de Avillez & Mac Low, 2002; Klessen & Lin, 2003; Feng & Krumholz, 2014).”
Dusty Star Forming Galaxies at High Redshift (2014, background): “2011b; Krumholz et al., 2011; Lagos et al., 2012; Narayanan et al., 2012b). While the effect of CO photodissociationmay play a role in lower-metallicity galaxies at high-z (e.g. Genzel et al., 2012; Tan et al., 2013), for the typical dusty heavily starforming systems that are the subject of this rev”
Inefficient star formation through turbulence, magnetic fields and feedback (2015, background): “Turbulence is a key for star formation (Mac Low & Klessen 2004; Elmegreen & Scalo 2004; McKee & Ostriker 2007; Krumholz 2014; Padoan et al. 2014), so most of our simulations include a turbulence driving module that produces turbulence similar to what is observed in real molecular clouds, i.e.,…”
The dust content of galaxies from z = 0 to z = 9 (2016, background): “Observations constrain this efficiency to ∼1% (Krumholz & Tan 2007; Krumholz, Dekel & McKee 2012; Krumholz 2014).”
A unified multiwavelength model of galaxy formation (2015, background): “Indeed, the whole issue of whether the IMF varies with environment or has varied over cosmic history remains hugely controversial, with a large literature, but arriving at conflicting conclusions (see recent reviews by Bastian et al. (2010) and Krumholz (2014)).”