Chemical evolution of the Galactic bulge as traced by microlensed dwarf and subgiant stars

Bensby, T.; Adén, D.; Meléndez, Jorge; Gould, Andrew; Feltzing, Sofia; Asplund, Martin; Johnson, Jennifer A.; Lucatello, S.; Yee, Jennifer C.; Ramírez, Iván; Cohen, Judith G.; Thompson, I. B.; Bond, I. A.; Gal‐Yam, A.; Han, Cheongho; Sumi, T.; Suzuki, D.; Wada, K.; Miyake, N.; Furusawa, K.; Ohmori, K.; Saito, To.; Tristram, P. J.; Bennett, D. P.

doi:10.1051/0004-6361/201117059

Cited by 220 publications

(383 citation statements)

References 102 publications

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“…This separation was also found by Bensby et al (2010Bensby et al ( , 2011Bensby et al ( , 2013. They carried out spectroscopy of GB dwarf stars during gravitational lensing amplification events.…”

Section: Introductionsupporting

confidence: 64%

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Accelerated post-AGB evolution, initial-final mass relations, and the star-formation history of the Galactic bulge

Gęsicki

Zijlstra

Hajduk

et al. 2014

A&A

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Aims. We study the star-formation history of the Galactic bulge, as derived from the age distribution of the central stars of planetary nebulae that belong to this stellar population. Methods. The high resolution imaging and spectroscopic observations of 31 compact planetary nebulae are used to derive their central star masses. We use the Blöcker post asymptotic giant branch (post-AGB) evolutionary models, which are accelerated by a factor of three in this case to better fit the white dwarf mass distribution and asteroseismological masses. Initial-final mass relations (IFMR) are derived using white dwarfs in clusters. These are applied to determine original stellar masses and ages. The age distribution is corrected for observational bias as a function of stellar mass. We predict that there are about 2000 planetary nebulae in the bulge. Results. The planetary nebula population points at a young bulge population with an extended star-formation history. The Blöcker tracks with the cluster IFMR result in ages, which are unexpectedly young. We find that the Blöcker post-AGB tracks need to be accelerated by a factor of three to fit the local white dwarf masses. This acceleration extends the age distribution. We adjust the IFMR as a free parameter to map the central star ages on the full age range of bulge stellar populations. This fit requires a steeper IFMR than the cluster relation. We find a star-formation rate in the Galactic bulge, which is approximately constant between 3 and 10 Gyr ago. The result indicates that planetary nebulae are mainly associated with the younger and more metal-rich bulge populations. Conclusions. The constant rate of star-formation between 3 and 10 Gyr agrees with suggestions that the metal-rich component of the bulge is formed during an extended process, such as a bar interaction.

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Section: Introductionsupporting

confidence: 64%

“…A younger bulge population has been found by Bensby et al (2010Bensby et al ( , 2011Bensby et al ( , 2013 as mentioned in the Introduction. Uttenthaler et al (2007) find evidence of the third dredge-up in four out of 27 bulge AGB stars based on the presence of radioactive technetium.…”

Section: The Age Of the Bulgementioning

confidence: 94%

Accelerated post-AGB evolution, initial-final mass relations, and the star-formation history of the Galactic bulge

Gęsicki

Zijlstra

Hajduk

et al. 2014

A&A

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“…As shown in Gardner et al (2014), the bar forms a clear box/peanut shape as seen from the side, and an Xshape along the line-of-sight when observed like the Milky Way. Ness et al (2014) showed further that the bulge stars have a range of ages, as observed in the Milky Way (Bensby et al 2011(Bensby et al , 2013Valenti et al 2013).…”

Section: Global Properties Of the Modelmentioning

confidence: 89%

The formation of stellar nuclear discs in bar-induced gas inflows

Cole

Debattista

Erwin

et al. 2014

Monthly Notices of the Royal Astronomical Society

123

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The role of gas in the mass assembly at the nuclei of galaxies is still subject to some uncertainty. Stellar nuclear discs bridge the gap between the large-scale galaxy and the central massive objects that reside there. Using a high resolution simulation of a galaxy forming out of gas cooling and settling into a disc, we study the formation and properties of nuclear discs. Gas, driven to the centre by a bar, settles into a rotating star-forming nuclear disc (ND). This ND is thinner, younger, kinematically cooler, and more metal-rich than the surrounding bar. The ND is elliptical and orthogonal to the bar. The complex kinematics in the region of the ND are a result of the superposition of older stars streaming along the bar and younger stars circulating within the ND. The signature of the ND is therefore subtle in the kinematics. Instead the ND stands out clearly in metallicity and age maps. We compare the model to the density and kinematics of real galaxies with NDs finding qualitative similarities. Our results suggest that gas dissipation is very important for forming nuclear structures.

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“…We compared the abundances of the sample stars and the bulge microlensed dwarf and subgiant stars studied by Bensby et al (2010Bensby et al ( , 2011Bensby et al ( , 2013, and red giants from the bulge Plaut field by Johnson et al (2012Johnson et al ( , 2013. comparison.…”

Section: Comparison With Bulge Starsmentioning

confidence: 99%

Heavy elements in old very metal-rich stars

Trevisan

Barbuy

2014

A&A

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Context. We studied a sample of high proper motion, old and metal-rich dwarf stars, selected from the NLTT catalogue. The low pericentric distances and eccentric orbits of these solar neighbourhood stars indicate that they might have originated in the inner parts of the Galaxy. Aims. Chemical tagging can probe the formation history of stellar populations. To identify the origin of a sample of 71 very metal-rich dwarf stars, we derive the abundances of the neutron-capture elements Y, Ba, La, and Eu. Methods. The spectroscopic analysis is based on optical high-resolution échelle spectra obtained with the FEROS spectrograph at the ESO 1.52 m Telescope at La Silla, Chile. The abundances of Y, Ba, La, and Eu were derived through LTE analysis, employing the MARCS model atmospheres.Results. The abundances of Y, Ba, La, and Eu vs. Fe and Mg as the reference elements indicate similarities between our sample of old metal-rich dwarf stars and the thin disk. On the other hand, the abundance ratios using O as the reference element, as well as their kinematics, suggest that our sample is clearly distinct from the thin-disk stars. They could be old inner thin-disk stars, as suggested previously, or bulge stars. In either cases, they would have migrated from the inner parts of the Galaxy to the solar neighbourhood.

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Chemical evolution of the Galactic bulge as traced by microlensed dwarf and subgiant stars

Cited by 220 publications

References 102 publications

Accelerated post-AGB evolution, initial-final mass relations, and the star-formation history of the Galactic bulge

Accelerated post-AGB evolution, initial-final mass relations, and the star-formation history of the Galactic bulge

The formation of stellar nuclear discs in bar-induced gas inflows

Heavy elements in old very metal-rich stars

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