Stochasticity, a variable stellar upper mass limit, binaries and star formation rate indicators

Eldridge, J. J.

doi:10.1111/j.1365-2966.2012.20662.x

Cited by 73 publications

(73 citation statements)

References 59 publications

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“…The conclusions from Cerviño et al (2002) were based on a Salpeter 1955 IMF over the mass range 2-120 M . Even though the increased mass range (0.08-300 M ) in our work would push the threshold total mass upward, an ensemble of such clusters in e.g., a starburst galaxy, should collectively smear out the sampling effects (see e.g., Cerviño et al 2000;Eldridge 2012). The FSPS+MIST model predicts a harder spectrum compared to the SB99+Geneva model, partially due to differences in the underlying isochrones.…”

Section: Imf Stochasticitymentioning

confidence: 89%

The Evolution and Properties of Rotating Massive Star Populations

Choi

Conroy

Byler

2017

ApJ

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We investigate the integrated properties of massive (> 10 M ), rotating, single-star stellar populations for a variety of initial rotation rates (v/v crit = 0.0, 0.2, 0.4, 0.5, and 0.6). We couple the new MESA Isochrone and Stellar Tracks (MIST) models to the Flexible Stellar Population Synthesis (FSPS) package, extending the stellar population synthesis models to include the contributions from very massive stars (> 100 M ), which can be significant in the first ∼ 4 Myr after a starburst. These models predict ionizing luminosities that are consistent with recent observations of young nuclear star clusters. We also construct composite stellar populations assuming a distribution of initial rotation rates. Even in low-metallicity environments where rotation has a significant effect on the evolution of massive stars, we find that stellar population models require a significant contribution from fast-rotating (v/v crit > 0.4) stars in order to sustain the production of ionizing photons beyond a few Myr following a starburst. These results have potentially important implications for cosmic reionization by massive stars and the interpretation of nebular emission lines in high-redshift star-forming galaxies.

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Section: Imf Stochasticitymentioning

confidence: 89%

The Evolution and Properties of Rotating Massive Star Populations

Choi

Conroy

Byler

2017

ApJ

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“…This stochasticity was ignored in earlier generations of SPS models, but detailed comparisons between the observations and newer SPS codes that include stochasticity (Eldridge & Stanway 2009;da Silva et al 2012) show that stochastic star formation plus a normal IMF is fully consistent with the data, and in fact provides a much better match than models with the proposed "top-light" IMFs (Fumagalli et al 2011;Eldridge 2012;Weisz et al 2012). This theoretical explanation has now received direct observational support from measurements of Hα to FUV ratios in individual star clusters in nearby galaxies, which show that individual clusters are indeed likely to be Hα-deficient, but that this is because a randomly-selected cluster is likely to be at an age when it most massive stars have already left the main sequence (Gogarten et al 2009).…”

Section: Unresolved Populationsmentioning

confidence: 98%

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

2014

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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 question 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.

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“…In this case it is not clear if B(m, t) can be separated into independent functions and how (Cerviño et al 2011). This implies major revisions of global galactic and extragalactic studies, including the SSP concept, and there is currently a large debate on the issue (Corbelli et al 2009;Fumagalli et al 2011;Eldridge 2012). Although a full discussion goes beyond the scope of this paper, we want to point out that there would be a M −m max physical law, although it must be imposed ad hoc, and that, whatever the case, random sampling and a probabilistic description of the IMF are compatible with it.…”

Section: Identical and Independent Distributed Variables And The Relamentioning

confidence: 99%

Crucial aspects of the initial mass function

Cerviño

Romann-Zuniga

Luridiana

et al. 2013

A&A

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Context. Our understanding of stellar systems depends on the adopted interpretation of the initial mass function, IMF φ(m). Unfortunately, there is not a common interpretation of the IMF, which leads to different methodologies and diverging analysis of observational data. Aims. We study the correlation between the most massive star that a cluster would host, m max , and its total mass into stars, M, as an example where different views of the IMF lead to different results. Methods. We assume that the IMF is a probability distribution function and analyze the m max − M correlation within this context. We also examine the meaning of the equation used to derive a theoretical M −m max relationship, N × mup mmax φ(m) dm = 1 with N the total number of stars in the system, according to different interpretations of the IMF. Results. We find that only a probabilistic interpretation of the IMF, where stellar masses are identically independent distributed random variables, provides a self-consistent result. Neither M nor the total number of stars in the cluster, N, can be used as IMF scaling factors. In addition,m max is a characteristic maximum stellar mass in the cluster, but not the actual maximum stellar mass. A M −m max correlation is a natural result of a probabilistic interpretation of the IMF; however, the distribution of observational data in the N (or M) − m max plane includes a dependence on the distribution of the total number of stars, N (and M), in the system, Φ N (N), which is not usually taken into consideration. Conclusions. We conclude that a random sampling IMF is not in contradiction to a possible m max − M physical law. However, such a law cannot be obtained from IMF algebraic manipulation or included analytically in the IMF functional form. The possible physical information that would be obtained from the N (or M) − m max correlation is closely linked with the Φ M (M) and Φ N (N) distributions; hence it depends on the star formation process and the assumed definition of stellar cluster.

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Stochasticity, a variable stellar upper mass limit, binaries and star formation rate indicators

Cited by 73 publications

References 59 publications

The Evolution and Properties of Rotating Massive Star Populations

The Evolution and Properties of Rotating Massive Star Populations

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

Crucial aspects of the initial mass function

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