A Chemical Abundance Study of 10 Open Clusters Based on Wiyn-Hydra Spectroscopy

Jacobson, Heather R.; Pilachowski, Catherine A.; Friel, Eileen D.

doi:10.1088/0004-6256/142/2/59

Cited by 118 publications

(136 citation statements)

References 116 publications

(243 reference statements)

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“…13. As discussed in the literature, this is caused by inhomogeneous chemical enhancements in the Galactic disc (Haywood , 2008;Jacobson et al , 2011), orbital diffusion, and radial migration and mixing of OCs (Schönrich & Binney , 2009). These OCs have probably originated from differing Galactic radii and/or from various star forming regions (Lepine et al , 2011).…”

Section: Discussionmentioning

confidence: 98%

CCD UBV(RI)C photometry of twenty open clusters

Oralhan¹,

Karataş²,

Schuster³

et al. 2015

New Astronomy

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Fundamental astrophysical parameters have been derived for 20 open clusters (OCs) using CCD UBV(RI) C photometric data observed with the 84 cm telescope at the San Pedro Mártir National Astronomical Observatory, México.The interstellar reddenings, metallicities, distances, and ages have been compared to the literature values. Significant differences are usually due to the usage of diverse empirical calibrations and differing assumptions, such as concerning cluster metallicity, as well as distinct isochrones which correspond to differing element-abundance ratios, internal stellar physics, and photometric systems. Different interstellar reddenings, as well as varying reduction and cluster-membership techniques, are also responsible for these kinds of systematic differences and errors.The morphological ages, which are derived from the morphological indices (δV and δ1) in the CM diagrams, are in good agreement with the isochrone ages of 12 OCs, those with good red clump (RC) and red giant (RG) star candidates. No metal abundance gradient is detected for the range 6.82 ≤ R GC ≤ 15.37 kpc, nor any correlation between the cluster ages and metal abundances for these 20 OCs.Young, metal-poor OCs, observed here in the third Galactic quadrant, may be associated with stellar over-densities, such as that in Canis Major (Martin et al.) and the Monoceros Ring (Newberg et al.), or signatures of past accretion events, as discussed by Yong et al. and Carraro et al.

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Section: Discussionmentioning

confidence: 98%

CCD UBV(RI)C photometry of twenty open clusters

Oralhan¹,

Karataş²,

Schuster³

et al. 2015

New Astronomy

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“…This may be mainly an effect of radial migration of the stars through "churning" or "blurring" 3 . However, it is unclear which type of mixing is responsible for the dispersion in metallicity measured in the so- lar vicinity, because it is known that the Sun is near the dividing line between the inner disk, which is enriched in metals (mean [Fe/H] ∼ +0.2 dex at R < 7 kpc, see Hill et al 2012), and the outer disk which is depleted in metals (mean [Fe/H] ∼ −0.3 dex at R > 10 kpc, field stars: Bensby et al (2011) and references therein; open clusters: Jacobson et al (2011) and references therein). As a result of the Sun lying near this dividing line, it is possible that the solar neighborhood has contamination from stars with a relatively wide range of metallicities but which did not originate very far from the solar orbit.…”

Section: The Age-metallicity Relationmentioning

confidence: 99%

The age structure of stellar populations in the solar vicinity

Haywood

Matteo

Lehnert

et al. 2013

A&A

529

175

868

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We analyze a sample of solar neighborhood stars that have high-quality abundance determinations and show that there are two distinct regimes of [α/Fe] versus age, which we identify as the epochs of the thick and thin disk formation. A tight correlation between metallicity and [α/Fe] versus age is clearly identifiable for thick disk stars, implying that this population formed from a well mixed interstellar medium, probably initially in starburst and then more quiescently, over a time scale of 4−5 Gyr. Thick disk stars have vertical velocity dispersions which correlate with age, with the youngest objects of this population having small scale heights similar to those of thin disk stars. A natural consequence of these two results is that a vertical metallicity gradient is expected in this population. We suggest that the youngest thick disk set the initial conditions from which the inner thin disk started to form about 8 Gyr ago, at [Fe/H] in the range of (−0.1, +0.1) dex and [α/Fe] ∼ 0.1 dex. This also provides an explanation for the apparent coincidence between the existence of a step in metallicity at 7−10 kpc in the thin disk and the confinement of the thick disk within R < 10 kpc. We suggest that the outer thin disk developed outside the influence of the thick disk, giving rise to a separate structure, but also that the high alphaenrichment of those regions may originate from a primordial pollution of the outer regions by the gas expelled from the forming thick disk. Metal-poor thin disk stars ([Fe/H] < −0.4 dex) in the solar vicinity, whose properties are best explained by them originating in the outer disk, are shown to be as old as the youngest thick disk (9−10 Gyr). This implies that the outer thin disk started to form while the thick disk was still forming stars in the inner parts of the Galaxy. Hence, while the overall inner (thick+thin) disk is comprised of two structures with different scale lengths and whose combination may give the impression of an inside-out formation process, the thin disk itself probably formed its first stars in its outskirts. Moreover, we point out that, given the tight age−metallicity and age-[α/Fe] relations that exist in the thick disk, an inside-out process would give rise to a radial gradient in metallicity and α-elements in this population, which is not observed. Finally, we argue that our results leave little room for radial migration (in the sense of churning) either to have contaminated the solar vicinity, or, on a larger scale, to have redistributed stars in significant proportion across the solar annulus.

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“…Gilroy (1989) provides the masses of the stars on the giant branch, and we used these values for our analysis. For NGC 7789 there are two recent age determinations of 1.4 Gyr (Kalirai et al 2008) and 1.8 Gyr (Jacobson et al 2011). When using isochrones from Bressan et al (2012), the turn-off mass is 1.8 ± 0.2 M .…”

Section: Sample Definition and Observationsmentioning

confidence: 99%

Oxygen isotopic ratios in intermediate-mass red giants

Lebzelter

Straniero

Hinkle

et al. 2015

A&A

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Context. The abundances of the three main isotopes of oxygen are altered in the course of the CNO-cycle. When the first dredge-up mixes the burning products to the surface, the nucleosynthesis processes can be probed by measuring oxygen isotopic ratios. Aims. By measuring 16 O/ 17 O and 16 O/ 18 O in red giants of known mass we compare the isotope ratios with predictions from stellar and galactic evolution modelling. Methods. Oxygen isotopic ratios were derived from the K-band spectra of six red giants. The sample red giants are open cluster members with known masses of between 1.8 and 4.5 M . The abundance determination employs synthetic spectra calculated with the COMARCS code. The effect of uncertainties in the nuclear reaction rates, the mixing length, and of a change in the initial abundance of the oxygen isotopes was determined by a set of nucleosynthesis and mixing models using the FUNS code.

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A Chemical Abundance Study of 10 Open Clusters Based on Wiyn-Hydra Spectroscopy

Cited by 118 publications

References 116 publications

CCD UBV(RI)C photometry of twenty open clusters

CCD UBV(RI)C photometry of twenty open clusters

The age structure of stellar populations in the solar vicinity

Oxygen isotopic ratios in intermediate-mass red giants

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