A Large Stellar Evolution Database for Population Synthesis Studies. II. Stellar Models and Isochrones for an α‐enhanced Metal Distribution

Pietrinferni, A.; Cassisi, S.; Salaris, Maurizio; Castelli, F.

doi:10.1086/501344

Cited by 626 publications

(729 citation statements)

References 47 publications

(75 reference statements)

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“…We employed the BaSTI isochrones (Pietrinferni et al , 2006, calculated with similar [α/Fe] abundance ratios to the stellar atmospheres, converted to the observational plane using extensive empirical photometric stellar libraries, mostly from Alonso et al (1996Alonso et al ( , 1999. To improve the metallicity coverage around the solar value we computed a new set of BaSTI isochrones with metallicity Z = 0.024 ([M/H] = +0.15).…”

Section: Discussionmentioning

confidence: 99%

Evolutionary stellar population synthesis with MILES – II. Scaled-solar and α-enhanced models

Vazdekis

Coelho

Cassisi

et al. 2015

Monthly Notices of the Royal Astronomical Society

320

394

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We present models that predict spectra of old-and intermediate-aged stellar populations at 2.51Å (FWHM) with varying [α/Fe] abundance. The models are based on the MILES library and on corrections from theoretical stellar spectra. The models employ recent [Mg/Fe] determinations for the MILES stars and BaSTI scaled-solar and α-enhanced isochrones. We compute models for a suite of IMF shapes and slopes, covering a wide age/metallicity range. Using BASTI, we also compute "base models" matching The Galactic abundance pattern. We confirm that the α-enhanced models show a flux excess with respect to the scaled-solar models blue-ward ∼4500Å, which increases with age and metallicity. We also confirm that both [MgFe] and [MgFe] ′ indices are [α/Fe]-insensitive. We show that the sensitivity of the higher order Balmer lines to [α/Fe] resides in their pseudo-continua, with narrower index definitions yielding lower sensitivity. We confirm that the α-enhanced models yield bluer (redder) colours in the blue (red) spectral range. To match optical colours of massive galaxies we require both α-enhancement and a bottom-heavy IMF. The comparison of Globular Cluster line-strengths with our predictions match the [Mg/Fe] determinations from their individual stars. We obtain good fits to both full spectra and indices of galaxies with varying [α/Fe]. Using thousands of SDSS galaxy spectra we obtain a linear relation between a proxy for the abundance,

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Section: Discussionmentioning

confidence: 99%

Evolutionary stellar population synthesis with MILES – II. Scaled-solar and α-enhanced models

Vazdekis

Coelho

Cassisi

et al. 2015

Monthly Notices of the Royal Astronomical Society

320

394

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“…At the highest metallicities (Z = 0.005), the main sequence evolutionary time for a star arriving at the horizontal branch (HB) with ∼ 0.55 M⊙, exceeds the age of the Universe (even assuming large mass loss along the red giant branch, e.g. Pietrinferni et al 2006;Choi et al 2016). At the low metallicities (Z = 0.002) the stars do not reach the instability strip after helium ignition, becoming red clump objects on the cool side of the classical instability strip.…”

Section: Discussionmentioning

confidence: 99%

Anomalous double-mode RR Lyrae stars in the Magellanic Clouds

Soszyński

Smolec

Dziembowski

et al. 2016

Mon. Not. R. Astron. Soc.

172

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We report the discovery of a new subclass of double-mode RR Lyrae stars in the Large and Small Magellanic Clouds. The sample of 22 pulsating stars have been extracted from the latest edition of the OGLE collection of RR Lyrae variables in the Magellanic System. The stars pulsating simultaneously in the fundamental (F) and first-overtone (1O) modes have distinctly different properties than regular double-mode RR Lyrae variables (RRd stars). The P 1O /P F period ratios of our anomalous RRd stars are within a range 0.725-0.738, while "classical" double-mode RR Lyrae variables have period ratios in the range 0.742-0.748. In contrast to the typical RRd stars, in the majority of the anomalous pulsators the F-mode amplitudes are higher than the 1O-mode amplitudes. The light curves associated with the F-mode in the anomalous RRd stars show different morphology than the light curves of, both, regular RRd stars and single-mode RRab stars. Most of the anomalous double-mode stars show long-term modulations of the amplitudes (Blazhko-like effect). Translating the period ratios into the abundance parameter, Z, we find for our stars Z ∈ (0.002, 0.005) -an order of magnitude higher values than typical for RR Lyrae stars. The mass range of the RRd stars inferred from the W I vs. P F diagram is (0.55 − 0.75) M ⊙ . These parameters cannot be accounted for with single star evolution assuming a Reimers-like mass loss. Much greater mass loss caused by interaction with other stars is postulated. We blame the peculiar pulsation properties of our stars to the parametric resonance instability of the 1O-mode to excitation of the F-and 2O-modes as with the inferred parameters of the stars 2ω 1O ≈ ω F + ω 2O .

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“…Each SSP has been calculated allowing a small age range around the current value of age given by ∆τ = 0.002 × 10 j with j = 7, ..., 9. No α-enhanced or He-enhanced tracks are in use in this example (e.g., α-enhanced tracks can easily be taken from an external database, e.g., Pietrinferni et al (2006) or He-enhanced from Bertelli et al (2008)), and interpolated as in the previous scheme, although this extra-dimension SSP interpolation is beyond the goals of the present paper focused on the kinematics of the spiral arms populations. In total, the data base contains Nτ × NZ ∼ = 150 SSP.…”

Section: Sources Of Stellar Tracks Isochrones Ssps In Different Phomentioning

confidence: 99%

Spiral arm kinematics for Milky Way stellar populations

Pasetto

Natale

Kawata

et al. 2016

Mon. Not. R. Astron. Soc.

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We present a new theoretical population synthesis model (the Galaxy Model) to examine and deal with large amounts of data from surveys of the Milky Way and to decipher the present and past structure and history of our own Galaxy.We assume the Galaxy to consist of a superposition of many composite stellar populations belonging to the thin and thick disks, the stellar halo and the bulge, and to be surrounded by a single dark matter halo component. A global model for the Milky Way's gravitational potential is built up self-consistently with the density profiles from the Poisson equation. In turn, these density profiles are used to generate synthetic probability distribution functions (PDFs) for the distribution of stars in colour-magnitude diagrams (CMDs). Finally, the gravitational potential is used to constrain the stellar kinematics by means of the moment method on a (perturbed)-distribution function. Spiral arms perturb the axisymmetric disk distribution functions in the linear response framework of density-wave theory where we present an analytical formula of the so-called 'reduction factor' using Hypergeometric functions.Finally, we consider an analytical non-axisymmetric model of extinction and an algorithm based on the concept of probability distribution function to handle colour magnitude diagrams with a large number of stars. A genetic algorithm is presented to investigate both the photometric and kinematic parameter space.This galaxy model represents the natural framework to reconstruct the structure of the Milky Way from the heterogeneous data set of surveys such as Gaia-ESO, SEGUE, APOGEE2, RAVE and the Gaia mission.

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A Large Stellar Evolution Database for Population Synthesis Studies. II. Stellar Models and Isochrones for an α‐enhanced Metal Distribution

Cited by 626 publications

References 47 publications

Evolutionary stellar population synthesis with MILES – II. Scaled-solar and α-enhanced models

Evolutionary stellar population synthesis with MILES – II. Scaled-solar and α-enhanced models

Anomalous double-mode RR Lyrae stars in the Magellanic Clouds

Spiral arm kinematics for Milky Way stellar populations

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