Metallicity Effects on the Properties of Very Young Star Clusters

García-Vargas, María Luisa; Bressan, A.; Díaz, Ángeles I.

doi:10.1017/cbo9780511600159.026

Cited by 56 publications

(102 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Our modelling differs from theirs in (a) the metal mixture, especially for what concerns the N/O ratio, which in our grid varies with the metallicity, and (b) the geometry, which is spherical in our case and plane-parallel geometry in García-Vargas et al (1995a).…”

Section: Continuum Shape and Intensitymentioning

confidence: 88%

“…It is important to note that using a zeroage SED is roughly equivalent to using a single stellar atmosphere model with T eff between 45 000 and 50 000 K (cf. MasHesse & Kunth 1991;García-Vargas et al 1995a), with the exact value depending on metallicity. One of the conclusions of these authors, specifically that Hii regions can be modelled with zero-age SEDs, contrasts with the philosophy underlying evolutionary synthesis models, which are in their essence evolutionary.…”

Section: Continuum Shape and Intensitymentioning

confidence: 99%

See 1 more Smart Citation

On emission-line spectra obtained from evolutionary synthesis models

Villaverde

Cerviño

Luridiana

2010

A&A

View full text Add to dashboard Cite

Aims. In this paper we study the influence of the ionizing cluster mass on the emission line spectrum of H ii regions in order to determine the influence of low mass clusters on the integrated emission line spectra of galaxies. Methods. For this purpose, we present a grid of photoionization models that covers metallicities from Z = 0.001 to Z = 0.040, ages from 0.1 to 10 Ma (with a time step of 0.1 Ma), and cluster initial masses from 1 to 10 7 M . The stellar masses follow a Salpeter initial mass function (IMF) in an instantaneous burst mode of star formation. We obtain power-law scale-relations between emission-line luminosities and ionizing cluster masses from the grids and we evaluate the dependences on the ionizing cluster mass for some line luminosities, equivalent widths and line ratios. Results. Power-law scale-relations are shown to be useful tools to obtain robust diagnostics, as examples: (a) Hα/Hβ ratio varies from the usually assumed value of 2.86, these variations imply the existence of a lower limit to the attainable precision in extinction star formation rate indicator for ages older than ∼4.5 Ma. We also show that the ionizing cluster mass dependence explains why empirical calibrations produce more reliable diagnostics of some emission lines than photoionization models grids. Finally, we show preliminary results about the contribution of low mass clusters (M < 10 4 M ) to the integrated emission line spectra of galaxies, which can be as high as 80% for some relevant lines.

show abstract

Section: Continuum Shape and Intensitymentioning

confidence: 88%

Section: Continuum Shape and Intensitymentioning

confidence: 99%

On emission-line spectra obtained from evolutionary synthesis models

Villaverde

Cerviño

Luridiana

2010

A&A

View full text Add to dashboard Cite

show abstract

“…There are copious studies related to the existence and modeling of a M − m max correlation (for instance, Reddish 1978;Larson 1982;Vanbeveren 1982;García-Vargas & Díaz 1994;García-Vargas et al 1995;Elmegreen 1997Elmegreen , 1999Elmegreen , 2000 Kroupa et al 2011). Some of these articles give an explicit formulation of this relation, while others propose that it is a physical relation that links both quantities.…”

Section: Literature On the M − M Max And The N − M Max Correlationsmentioning

confidence: 99%

“…Let us consider the case of García-Vargas & Díaz (1994) and García-Vargas et al (1995) as an example of this interpretation. They assume that the IMF is not a probability distribution but an exact analytical law, φ GV (m) = k(M) × φ(m), where k(M) is a renormalization constant that, because M is the exact value of the amount of gas transformed into stars, verifies…”

Section: The Imf As An Exact Analytical Lawmentioning

confidence: 99%

“…Even if the authors themselves now consider the sorted sampling proposal just as a first approximation (Kroupa et al 2011), we want to emphasize that the key point of different sampling algorithms is not the sorting process, but the assumed relation between N and M (e.g., the sorted sampling proposal uses an N value estimated by means of M divided by m|m < m max , which imposes a constraint in N). The situation is actually more clearly described in the richness effect proposed by García-Vargas & Díaz (1994); García-Vargas et al (1995): a star with mass m a is formed according to the amount of gas that remains in the system once a certain number of stars with m < m a have been formed. The sampling problem appears when we try to fix M(m < m a ) and N(m < m a ) simultaneously and include it analytically in the φ(m) functional form.…”

Section: Sampling Iid Variables and The Relation Of The Imf With Sfmentioning

confidence: 99%

See 1 more Smart Citation

Crucial aspects of the initial mass function

Cerviño

Romann-Zuniga

Luridiana

et al. 2013

A&A

View full text Add to dashboard Cite

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.

show abstract

Zero Metallicity Stellar Sources and the Reionization Epoch

Cojazzi

Bressan

Lucchin

et al.

Eso Astrophysics Symposia

View full text Add to dashboard Cite

We reconsider the problem of the cosmological reionization due to stellar sources. Using a method similar to that developed by Haiman & Loeb (1997), we investigate the effect of changing the stellar models and the stellar spectra adopted for deriving the ionizing photon production rate. In particular, we study the consequences of adopting zero metallicity stars, which is the natural choice for the first stellar populations. We construct young isochrones representative of Population III stars from existing sets of evolutionary models (Forieri 1982;Cassisi & Castellani 1993) and calculate a suitable library of zero metallicity model atmospheres. The number of ionizing photons emitted by such a zero metal population is about 40% higher than that produced by standard metal poor isochrones. We find that adopting suitable zero metallicity models modifies the reionization epoch. However the latter is still largely affected by current uncertainties in other important physical processes such as the efficiency of the star formation and the fraction of escaping UV photons.

show abstract

Metallicity Effects on the Properties of Very Young Star Clusters

Cited by 56 publications

References 0 publications

On emission-line spectra obtained from evolutionary synthesis models

On emission-line spectra obtained from evolutionary synthesis models

Crucial aspects of the initial mass function

Zero Metallicity Stellar Sources and the Reionization Epoch

Contact Info

Product

Resources

About