Population Synthesis in the Blue. II. The Spectroscopic Age of 47 Tucanae

Schiavon, Ricardo P.; Faber, S. M.; Rose, James A.; Castilho, Bruno V.

doi:10.1086/343789

Cited by 57 publications

(60 citation statements)

References 34 publications

(63 reference statements)

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“…Some solutions have been proposed, such as the inclusion of atomic diffusion in the stellar evolutionary models or the use of α-enhanced isochrones (see Vazdekis et al 2001), although none of these have been implemented in publicly available stellar population models. Schiavon et al (2002) showed, for the particular case of 47Tuc, that the luminosity function of the red giant branch is underestimated in the stellar evolutionary models and that the use of the observed luminosity functions instead of theoretical ones results in derived ages for this cluster consistent with the age of the Universe and with those derived directly from the colour-magnitude diagram. A similar effect in super-solar metallicity models would cause spectroscopic ages to be 30% too high (see Schiavon et al 2002, for details).…”

Section: Figmentioning

confidence: 62%

Evolution of red-sequence cluster galaxies from redshift 0.8 to 0.4: ages, metallicities, and morphologies

Sánchez‐Blázquez

Jablonka

Noll

et al. 2009

A&A

106

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We present a comprehensive analysis of the stellar population properties and morphologies of red-sequence galaxies in 24 clusters and groups from z ∼ 0.75 to z ∼ 0.45. The dataset, consisting of 215 spectra drawn from the ESO Distant Cluster Survey, constitutes the largest spectroscopic sample at these redshifts for which such an analysis has been conducted. Analysis reveals that the evolution of the stellar population properties of red-sequence galaxies depend on their mass: while the properties of the most massive are well described by passive evolution and high-redshift formation, those of the less massive galaxies are consistent with a more extended star-formation history. We show that these scenarios reproduce the index-σ relations and the galaxy colours. The two main results of this work are: (1) the evolution of the line-strength indices for the red-sequence galaxies can be reproduced if 40% of the galaxies with σ < 175 km s −1 entered the red-sequence between z = 0.75 to z = 0.45, in agreement with the fraction derived in studies of the luminosity functions; and (2) the percentage of red-sequence galaxies exhibiting early-type morphologies (E and S0) decreases by 20% from z = 0.75 to z = 0.45. This can be understood if the red-sequence becomes more populated at later times with disc galaxies whose star formation has been quenched. We conclude that the processes quenching star formation do not necessarily produce a simultaneous morphological transformation of the galaxies entering the red-sequence.

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Section: Figmentioning

confidence: 62%

Evolution of red-sequence cluster galaxies from redshift 0.8 to 0.4: ages, metallicities, and morphologies

Sánchez‐Blázquez

Jablonka

Noll

et al. 2009

A&A

106

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“…It is easy to see from these outputs that our results imply that 20−30% of the stars have ages older than the most recent estimates of the age of the Universe. This is a well known problem in the stellar population models (e.g., Vazdekis et al 2001;Schiavon et al 2002;Maraston et al 2011, V10). Several possible solutions have been proposed to alleviate this so-called zero point problem, and, in fact, several groups have successfully reconcile the age of globular clusters with ΛCDM cosmology (see Krauss & Chaboyer 2003); Percival & Salaris (2009) showed that systematic uncertainties associated with the three fundamental stellar atmospheric parameters might have a non negligible impact on the resulting SSP line-strengths.…”

Section: Star Formation Historiesmentioning

confidence: 98%

“…For example, the use of Padova (Girardi et al 2000; which are those used by V10) gives older ages than Padova (Bertelli et al 1994). Schiavon et al (2002) also stressed the importance of correctly modelling the luminosity function at the level of the giant branch for the particular problem of globular clusters. He showed, for 47 Tuc, that if the observed luminosity function is used rather than the theoretical ones, the spectroscopic and the colour-magnitude diagram ages coincide and are lower than the age of the Universe.…”

Section: Star Formation Historiesmentioning

confidence: 99%

Stellar population gradients in galaxy discs from the CALIFA survey

Sánchez‐Blázquez

Rosales-Ortega

Méndez-Abreu

et al. 2014

A&A

175

178

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While studies of gas-phase metallicity gradients in disc galaxies are common, very little has been done towards the acquisition of stellar abundance gradients in the same regions. We present here a comparative study of the stellar metallicity and age distributions in a sample of 62 nearly face-on, spiral galaxies with and without bars, using data from the CALIFA survey. We measure the slopes of the gradients and study their relation with other properties of the galaxies. We find that the mean stellar age and metallicity gradients in the disc are shallow and negative. Furthermore, when normalized to the effective radius of the disc, the slope of the stellar population gradients does not correlate with the mass or with the morphological type of the galaxies. In contrast to this, the values of both age and metallicity at ∼2.5 scale lengths correlate with the central velocity dispersion in a similar manner to the central values of the bulges, although bulges show, on average, older ages and higher metallicities than the discs. One of the goals of the present paper is to test the theoretical prediction that non-linear coupling between the bar and the spiral arms is an efficient mechanism for producing radial migrations across significant distances within discs. The process of radial migration should flatten the stellar metallicity gradient with time and, therefore, we would expect flatter stellar metallicity gradients in barred galaxies. However, we do not find any difference in the metallicity or age gradients between galaxies with and without bars. We discuss possible scenarios that can lead to this lack of difference.

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“…The absolute value of the age depends on the methodology, a wellknown issue plaguing most stellar population studies (see, e.g., Vazdekis et al 2001;Schiavon et al 2002). Throughout this work, we adopt as a reference the age estimates from spectral fitting (method F IT 1 above), rescaled to match the Hγ275-based value (∼ 11 Gyr) at the galaxy centre.…”

Section: Radial Profiles Of Age and Metallicitymentioning

confidence: 99%

Radial constraints on the initial mass function from TiO features and Wing–Ford band in early-type galaxies

Barbera

Vazdekis

Ferreras

et al. 2016

Mon. Not. R. Astron. Soc.

100

118

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At present, the main challenge to the interpretation of variations in gravity-sensitive line strengths as driven by a non-universal initial mass function (IMF), lies in understanding the effect of the other population parameters. Most notably, [α/Fe]-enhanced populations or even departures in the individual element abundances with respect to the solar-scaled ratio may lead to similar observational results. We combine various TiO-based, IMF-sensitive indicators in the optical and NIR spectral windows, along with the FeH-based Wing-Ford band to break this degeneracy. We obtain a significant radial trend of the IMF slope in XSG1, a massive early-type galaxy (ETG), with velocity dispersion σ ∼ 300 km s −1 , observed with the VLT/X-SHOOTER instrument. In addition, we constrain -for the first time -both the shape and normalization of the IMF, using only a stellar population analysis. We robustly rule out a single power-law to describe the IMF, whereas a power law tapered off to a constant value at low masses (defined as a bimodal IMF) is consistent with all the observational spectroscopic data and with the stellar M/L constraints based on the Jeans Anisotropic Modelling method. The IMF in XSG1 is bottom-heavy in the central regions (corresponding to a bimodal IMF slope Γ b ∼3, or a mass normalization mismatch parameter α ∼2), changing towards a standard Milky-Way like IMF (Γ b ∼1.3; α ∼1) at around one half of the effective radius. This result, combined with previous observations of local IMF variations in massive ETGs, reflects the varying processes underlying the formation of the central core and the outer regions in this type of galaxies.

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Population Synthesis in the Blue. II. The Spectroscopic Age of 47 Tucanae

Cited by 57 publications

References 34 publications

Evolution of red-sequence cluster galaxies from redshift 0.8 to 0.4: ages, metallicities, and morphologies

Evolution of red-sequence cluster galaxies from redshift 0.8 to 0.4: ages, metallicities, and morphologies

Stellar population gradients in galaxy discs from the CALIFA survey

Radial constraints on the initial mass function from TiO features and Wing–Ford band in early-type galaxies

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