Converting Hα Luminosities into Star Formation Rates

Pflamm-Altenburg, Jan; Weidner, C.; Kroupa, Pavel

doi:10.1086/523033

Cited by 123 publications

(174 citation statements)

References 41 publications

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“…If true, this would have important effects on a wide range of astrophysical problems, most notably, on the inferred SFRs of (low SFR) galaxies based on Hα luminosities (e.g. Pflamm-Altenburg, Weidner & Kroupa 2007; 4 .…”

Section: Super Star Clustersmentioning

confidence: 99%

A Universal Stellar Initial Mass Function? A Critical Look at Variations

Bastian

Covey

Meyer

2010

Annu. Rev. Astron. Astrophys.

908

453

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Few topics in astronomy initiate such vigorous discussion as whether or not the initial mass function (IMF) of stars is universal, or instead sensitive to the initial conditions of star formation. The distinction is of critical importance: the IMF influences most of the observable properties of stellar populations and galaxies, and detecting variations in the IMF could provide deep insights into the process by which stars form. In this review, we take a critical look at the case for IMF variations, with a view towards whether other explanations are sufficient given the evidence. Studies of the field, local young clusters and associations, and old globular clusters suggest that the vast majority were drawn from a "universal" IMF: a power-law of Salpeter index (Γ = 1.35) above a few solar masses, and a log normal or shallower power-law (Γ ∼ 0 − 0.25) between a few tenths and a few solar masses (ignoring the effects of unresolved binaries). The shape and universality of the IMF at the stellar-substellar boundary is still under investigation and uncertainties remain large, but most observations are consistent with a IMF that declines (Γ < −0.5) well below the hydrogen burning limit. Observations of resolved stellar populations and the integrated properties of most galaxies are also consistent with a "universal IMF", suggesting no gross variations in the IMF over much of cosmic time. There are indications of "non-standard" IMFs in specific local and extragalactic environments, which clearly warrant further study. Nonetheless, there is no clear evidence that the IMF varies strongly and systematically as a function of initial conditions after the first few generations of stars. We close with suggestions for future work that might uncover more subtle IMF variations than those that could be discerned to date.

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Section: Super Star Clustersmentioning

confidence: 99%

A Universal Stellar Initial Mass Function? A Critical Look at Variations

Bastian

Covey

Meyer

2010

Annu. Rev. Astron. Astrophys.

908

453

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“…These assumptions result in a low Hα-to-FUV ratio by reducing the probability of forming massive stars in low-SFR galaxies. Pflamm-Altenburg et al (2007 models differ in the assumed cluster mass functions. The Minimal1 scenario uses a cluster mass function that follows µ -dN dM M 2 over most of its mass range in accord with most observational determinations of the cluster mass function (e.g., see the review by Krumholz (2014)).…”

Section: Non-universal Imfmentioning

confidence: 99%

THE BURSTY STAR FORMATION HISTORIES OF LOW-MASS GALAXIES AT 0.4 < z < 1 REVEALED BY STAR FORMATION RATES MEASURED FROM Hβ AND FUV

Guo

Rafelski

Faber

et al. 2016

ApJ

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We investigate the burstiness of star formation histories (SFHs) of galaxies at 0.4<z<1 by using the ratio of star formation rates (SFRs) measured from Hβ and FUV (1500 Å) (Hβ-to-FUV ratio). Our sample contains 164 galaxies down to stellar mass (M * ) of 10 8.5 M e in the CANDELS GOODS-N region, where Team Keck Redshift Survey Keck/DEIMOS spectroscopy and Hubble Space Telescope/WFC3 F275W images from CANDELS and Hubble Deep UV Legacy Survey are available. When the ratio of Hβ-and FUV-derived SFRs is measured, dust extinction correction is negligible (except for very dusty galaxies) with the Calzetti attenuation curve. The Hβ-to-FUV ratio of our sample increases with M * and SFR. The median ratio is ∼0.7 at M * ∼10 8.5 M e (or SFR∼0.5 M e yr −1 ) and increases to ∼1 at M * ∼10 10 M e (or SFR∼10 M e yr −1 ). At M * <10 9.5 M e , our median Hβ-to-FUV ratio is lower than that of local galaxies at the same M * , implying a redshift evolution. Bursty SFH on a timescale of a few tens of megayears on galactic scales provides a plausible explanation for our results, and the importance of the burstiness increases as M * decreases. Due to sample selection effects, our Hβ-to-FUV ratio may be an upper limit of the true value of a complete sample, which strengthens our conclusions. Other models, e.g., non-universal initial mass function or stochastic star formation on star cluster scales, are unable to plausibly explain our results.

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“…Within each star cluster, the initial mass function (IMF) can be well approximated by the canonical two-part power-law form ξ(m) ∝ m −α (e.g. Pflamm-Altenburg et al 2007, hereafter PWK07). Massey & Hunter (1998) have shown that for stellar masses m > a few M a slope similar to the Salpeter (1955) index (i.e.…”

Section: Introductionmentioning

confidence: 99%

“…The Salpeter IMF slope has been used in a very wide range of modelling, providing good fits with observations concerning the cosmic star formation history , the X-ray properties of elliptical galaxies (Pipino et al 2005), the chemical evolution of dwarf galaxies (Larsen et al 2001) and of the Milky Way (Pilyugin & Edmunds 1996; but see also Romano et al 2005). Broadly speaking, a flatter than Salpeter IMF produces a larger fraction of massive stars.…”

Section: Introductionmentioning

confidence: 99%

The chemical evolution of galaxies within the IGIMF theory: the [α/Fe] ratios and downsizing

Recchi

Calura²,

Kroupa³

2009

A&A

106

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Context. The chemical evolution of galaxies is investigated within the framework of the star formation rate (SFR) dependent integrated galactic initial mass function (IGIMF). Aims. We study how the global chemical evolution of a galaxy and in particular how [α/Fe] abundance ratios are affected by the predicted steepening of the IGIMF with decreasing SFR. Methods. We use analytical and semi-analytical calculations to evaluate the mass-weighted and luminosity-weighted [α/Fe] ratios in early-type galaxies of different masses.Results. The models with variable IGIMF produce an [α/Fe] vs. velocity dispersion relation which has the same slope as the observations of massive galaxies, irrespective of the model parameters, provided that the star formation duration inversely correlates with the mass of the galaxy (downsizing). These models also produce steeper [α/Fe] vs. σ relations in low-mass early-type galaxies and this trend is consistent with the observations. Constant IMF models are able to reproduce the [α/Fe] ratios in large elliptical galaxies as well, but they do not predict this change of slope for small galaxies. In order to obtain the best fit between our results and observations, the downsizing effect (i.e. the shorter duration of the star formation in larger galaxies) must be milder than previously thought.

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Converting Hα Luminosities into Star Formation Rates

Cited by 123 publications

References 41 publications

A Universal Stellar Initial Mass Function? A Critical Look at Variations

A Universal Stellar Initial Mass Function? A Critical Look at Variations

THE BURSTY STAR FORMATION HISTORIES OF LOW-MASS GALAXIES AT 0.4 < z < 1 REVEALED BY STAR FORMATION RATES MEASURED FROM Hβ AND FUV

The chemical evolution of galaxies within the IGIMF theory: the [α/Fe] ratios and downsizing

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