The Scale‐Free Character of the Cluster Mass Function and the Universality of the Stellar Initial Mass Function

Selman, F.; Melnick, J.

doi:10.1086/590481

Cited by 25 publications

(40 citation statements)

References 36 publications

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“…However, more direct approaches to measure the IMF in the Milky Way and local galaxies support a universal IMF (e.g. Massey et al 1995;Scalo 1998;Selman & Melnick 2008). In a recent study, we investigated the possibility of a variable IMF by studying the high mass star formation activity A115, page 12 of 15 of the HRS late-type galaxies, using the Hα and the FUV luminosity as two independent, direct tracers of star formation ).…”

Section: Discussionmentioning

confidence: 99%

The role of cold gas and environment on the stellar mass-metallicity relation of nearby galaxies

Hughes

Cortese

Boselli

et al. 2013

A&A

183

201

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We investigate the relationship between stellar mass, metallicity and gas content for a magnitude-and volume-limited sample of 260 nearby late-type galaxies in different environments, from isolated galaxies to Virgo cluster members. We derive oxygen abundance estimates using new integrated, drift-scan optical spectroscopy and the base metallicity calibrations of Kewley & Ellison (2008, ApJ, 681, 1183. Combining these measurements with ultraviolet to near-infrared photometry and Hi 21 cm line observations, we examine the relations between stellar mass, metallicity, gas mass fraction and star formation rate. We find that, at fixed stellar mass, galaxies with lower gas fractions typically also possess higher oxygen abundances. We also observe a relationship between gas fraction and metal content, whereby gas-poor galaxies are typically more metal-rich, and demonstrate that the removal of gas from the outskirts of spirals may increase the observed average metallicity by ∼0.1 dex. Although some cluster galaxies are gas-deficient objects, statistically the stellar-mass metallicity relation is nearly invariant to the environment, in agreement with recent studies. These results indicate that internal evolutionary processes, rather than environmental effects, play a key role in shaping the stellar mass-metallicity relation. In addition, we present metallicity estimates based on observations of 478 nearby galaxies.

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Section: Discussionmentioning

confidence: 99%

The role of cold gas and environment on the stellar mass-metallicity relation of nearby galaxies

Hughes

Cortese

Boselli

et al. 2013

A&A

183

201

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“…Corbelli et al 2009;Jamet et al 2004;Maíz Apellániz et al 2007, as some examples). Even more, even if there were clusters with masses M clus lower than m up (which implies a hard physical condition for the maximum stellar mass in the IMF realization), m up would be statistically preserved if the cluster system produced by the same molecular cloud contains clusters with M clus higher than m up (size-of-sample effect, Selman & Melnick 2008).…”

Section: Discussionmentioning

confidence: 99%

Modeling the ionizing spectra of H II regions: individual stars versus stellar ensembles

Villaverde

Cerviño

Luridiana

2010

A&A

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Aims. We study how IMF sampling affects the ionizing flux and emission line spectra of low mass stellar clusters. Methods. We performed 2 × 10 6 Monte Carlo simulations of zero-age solar-metallicity stellar clusters covering the 20−10 6 M mass range. We study the distribution of cluster stellar masses, M clus , ionizing fluxes, Q(H 0 ), and effective temperatures, T clus eff . We compute photoionization models that broadly describe the results of the simulations and compare them with photoionization grids.Results. Our main results are: (a) a large number of low mass clusters (80% for M clus = 100 M ) are unable to form an H ii region. (b) There are a few overluminous stellar clusters that form H ii regions. These overluminous clusters preserve statistically the mean value of Q(H 0 ) obtained by synthesis models, but the mean value cannot be used as a description of particular clusters. (c) The ionizing continuum of clusters with M clus < ∼ 10 4 M is more accurately described by an individual star with self-consistent effective temperature (T * eff ) and Q(H 0 ) than by the ensemble of stars (or a cluster T clus eff ) produced by synthesis models. (d) Photoionization grids of stellar clusters cannot be used to derive the global properties of low mass clusters. Conclusions. Although variations in the upper mass limit, m up , of the IMF would reproduce the effects of IMF sampling, we find that an ad hoc law that relates m up to M clus in the modeling of stellar clusters is useless, since: (a) it does not cover the whole range of possible cases; and (b) the modeling of stellar clusters with an IMF is motivated by the need to derive the global properties of the cluster: however, in clusters affected by sampling effects we have no access to global information of the cluster but only particular information about a few individual stars.

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“…The PDF describing ensembles with a total number of stars N (formally conditioned to have N stars) can be calculated as successive convolutions of the corresponding PDF for one star. For instance, the PDF for the total mass, Φ M (M|N), is the result of convolving the IMF N times with itself(see Cerviño & Luridiana 2006;Selman & Melnick 2008):…”

Section: Formal Probabilistic Formulationmentioning

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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The Scale‐Free Character of the Cluster Mass Function and the Universality of the Stellar Initial Mass Function

Cited by 25 publications

References 36 publications

The role of cold gas and environment on the stellar mass-metallicity relation of nearby galaxies

The role of cold gas and environment on the stellar mass-metallicity relation of nearby galaxies

Modeling the ionizing spectra of H II regions: individual stars versus stellar ensembles

Crucial aspects of the initial mass function

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