‘Polden’ v komnate’

Smith, Gerald Stanton

doi:10.1007/978-1-349-20765-7_7

Cited by 4 publications

(4 citation statements)

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“…3, a full picture of the chemical abundances inferred from our sample is shown: blue squares are the average values for NGC 1866 and red triangles for the LMC‐field stars. In Figs 4–9, we summarize the derived abundances of our sample for some interesting elements (filled grey points for the field stars and grey large square for the average value of the stars of NGC 1866), comparing these results with other data bases based on high‐resolution spectroscopy for the Galactic stars (empty grey points by Edvardsson et al 1993; Burris et al 2000; Fulbright 2000; Gratton et al 2003; Reddy et al 2003; Reddy, Lambert & Allende Prieto 2006), the LMC‐field stars (blue points by Smith et al 2002; Pompeia et al 2008) and the LMC globular clusters (GCs) (blue squares by Johnson et al 2006; Mucciarelli et al 2008b, 2010).…”

Section: Resultsmentioning

confidence: 88%

“… Behaviour of [O/Fe] (upper panel) and [Na/Fe] (lower panel) as a function of [Fe/H] for the observed stars: the grey square is the average value for the stars of NGC 1866, large grey points represent the individual LMC field stars, blue squares represent the intermediate‐age LMC clusters by Mucciarelli et al (2008b), and the old LMC clusters by Johnson et al (2006) and Mucciarelli et al (2010), the small grey points represent Galactic stars by Edvardsson et al (1993), Fulbright (2000), Burris et al (2000), Reddy et al (2003), Gratton et al (2003) and Reddy et al (2006), and the small blue points represent the LMC‐field giants by Pompeia et al (2008) and Smith et al (2002). Error bars indicate the typical uncertainties arising from the atmospheric parameters and the error in the fitting procedure.…”

Section: Resultsmentioning

confidence: 99%

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NGC 1866: a milestone for understanding the chemical evolution of stellar populations in the Large Magellanic Cloud★

Mucciarelli¹,

Cristallo²,

Brocato³

et al. 2011

Monthly Notices of the Royal Astronomical Society

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We present new FLAMES@VLT spectroscopic observations of 30 stars in the field of the Large Magellanic Cloud (LMC) stellar cluster NGC 1866. NGC 1866 is one of the few young and massive globular clusters that is close enough so that its stars can be individually studied in detail. Radial velocities have been used to separate stars belonging to the cluster and to the LMC field, and the same spectra have been used to derive chemical abundances for a variety of elements, from [Fe/H] to the light (i.e. Na, O, Mg, etc.) to the heavy ones. The average iron abundance of NGC 1866 turns out to be [Fe/H]=−0.43 ± 0.01 dex (with a dispersion σ= 0.04 dex), from the analysis of 14 cluster member stars. Within our uncertainties, the cluster stars are homogeneous, as far as chemical composition is concerned, independent of the evolutionary status. The observed cluster stars do not show any sign of the light elements' ‘anticorrelation’ present in all the Galactic globular clusters so far studied and are also found in the old LMC stellar clusters. A similar lack of anticorrelations has been detected in the massive intermediate‐age LMC clusters, indicating a different formation/evolution scenario for the LMC massive clusters younger than ∼3 Gyr with respect to the old ones. Also opposite to the Galactic globulars, the chemical composition of the older red giant branch field stars and of the young post‐main‐sequence cluster stars show robust homogeneity suggesting a quite similar process of chemical evolution. The field and cluster abundances are in agreement with recent chemical analysis of LMC stars, which show a distinctive chemical pattern for this galaxy with respect to the Milky Way. We discuss these findings in light of the theoretical scenario of chemical evolution of the LMC.

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Section: Resultsmentioning

confidence: 88%

Section: Resultsmentioning

confidence: 99%

NGC 1866: a milestone for understanding the chemical evolution of stellar populations in the Large Magellanic Cloud★

Mucciarelli¹,

Cristallo²,

Brocato³

et al. 2011

Monthly Notices of the Royal Astronomical Society

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“…Our synthetic LMC population has been computed using the scaled solar models by Girardi et al (2000). The LMC chemical evolution models by Pagel & Tautvaisiene (1998) and the spectroscopic observations by Hill et al (2000) and Smith et al (2002) show that at low metallicity the α‐elements (i.e. O, Ne, Mg, Si, S, Ca, Ti) are mildly enhanced with respect to Fe, i.e.…”

Section: Application To Composite Stellar Populationsmentioning

confidence: 99%

Tip of the Red Giant Branch distances to galaxies with composite stellar populations

Salaris

Girardi

2005

Monthly Notices of the Royal Astronomical Society

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The accurate determination of galaxy relative distances is extremely important for the empirical calibration of the uncertain metallicity dependence of some standard candles like Cepheid stars, or for studying the galaxy space distribution and peculiar velocities. Here we have investigated the reliability of the widely used I‐band Tip of the Red Giant Branch (TRGB) relative distances for a sample of Local Group galaxies with complex star formation histories (SFHs) and age–metallicity relationships (AMRs) namely the Large Magellanic Cloud (LMC), Small Magellanic Cloud (SMC) and LGS3. The use of the K band is also discussed. By employing theoretical stellar population synthesis techniques, we find that using actual determinations of SFH and AMR of the LMC and SMC, their RGB is populated by stars much younger (by ∼9 Gyr) than the Galactic globular cluster counterparts, on which the I‐band (and K‐band) TRGB absolute magnitude is calibrated. This age difference induces a bias in both the photometric metallicity estimates based on the comparison of RGB colours with globular cluster ones, and the TRGB distances. The extent of the distance bias – which is not influenced by the actual value of the TRGB absolute magnitude zero‐point – is strongly dependent on the specific TRGB technique applied, and on the assumed I‐band bolometric correction (BCI) scale adopted; the correction to apply to the SMC–LMC distance modulus ranges from 0 up to +0.10 mag. LGS3 is an example of a galaxy populated mainly by old stars, so that photometric metallicity and distance estimates using globular cluster calibrations are reliable. However, the relative distance moduli between the Magellanic Clouds and LGS3 are affected by the population effects discussed for the LMC and SMC. The correction to apply to the LGS3–LMC distance modulus ranges between −0.05 and +0.14 mag, whereas in the case of the LGS3–SMC distance modulus it goes from −0.07 to +0.04 mag. In the case of all three relative distances discussed before, the correction to apply to the K‐band TRGB distances are larger than the I‐band case. Our results clearly show that the presence of a well‐developed RGB in the colour – magnitude diagram of a stellar system with a complex SFH does not guarantee that it is populated by globular cluster‐like red giants, and therefore the TRGB method for distance determination has to be applied with caution. A definitive assessment of the appropriate corrections for population effects on TRGB distances has, however, to wait for a substantial reduction in the uncertainties on the BCI scale for cold stars.

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“…A better match to the optical colour–magnitude diagram of the cluster stars is obtained by an isochrone of slightly younger age, t ∼ 800 Myr, yet the best match is obtained by an isochrone with t ∼ 1 Gyr but with a lower metallicity of [ M / H ]∼−0.7. Smith et al (2002) also argue that, with [ M / H ]∼−0.6, LMC red giants with M ZAMS ∼ 3 M ⊙ often have metallicities lower than what is normally taken as the canonical LMC metallicity, [ M / H ]∼−0.4 to −0.3. Consequently, we also suspect that the older, a few Gyr old, field population has a low metallicity of [ M / H ]∼−0.7.…”

Section: The Progenitor Mass Of Li‐lmc 1813mentioning

confidence: 93%

The superwind mass-loss rate of the metal-poor carbon star LI-LMC 1813 in the LMC cluster KMHK 1603

Loon

Marshall

Matsuura³

et al. 2003

Monthly Notices of the Royal Astronomical Society

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The superwind mass-loss rate of the metal-poor carbon star LI-LMC 1813 Optical and infrared photometry between 0.5 and 60 µm is obtained to constrain the spectral energy distribution of LI-LMC 1813. Near-infrared spectra unambiguously show it to be a carbon star. Modelling with the radiation transfer code Dusty yields accurate values for the bolometric luminosity, L = 1.5 × 10 4 L ⊙ , and mass-loss rate, M = 3.7(±1.2) × 10 −5 M ⊙ yr −1 . On the basis of colour-magnitude diagrams, the age of the cluster KMHK 1603 is estimated to be t = 0.9-1.0 Gyr, which implies a ZeroAge Main Sequence mass for LI-LMC 1813 of M ZAMS = 2.2 ± 0.1 M ⊙ . This makes LI-LMC 1813 arguably the object with the most accurately and reliably determined (circum)stellar parameters amongst all carbon stars in the superwind phase.

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‘Polden’ v komnate’

Cited by 4 publications

References 0 publications

NGC 1866: a milestone for understanding the chemical evolution of stellar populations in the Large Magellanic Cloud★

NGC 1866: a milestone for understanding the chemical evolution of stellar populations in the Large Magellanic Cloud★

Tip of the Red Giant Branch distances to galaxies with composite stellar populations

The superwind mass-loss rate of the metal-poor carbon star LI-LMC 1813 in the LMC cluster KMHK 1603

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