On the Kinematic Separation of Field and Cluster Stars Across the Bulge Globular Ngc 6528

Lagioia, E. P.; Milone, A. P.; Stetson, P. B.; Bono, G.; Moroni, P. G. Prada; Dall’Ora, M.; Aparicio, A.; Buonanno, R.; Calamida, A.; Ferraro, I.; Gilmozzi, R.; Iannicola, G.; Matsunaga, Noriyuki; Monelli, M.; Walker, A. R.

doi:10.1088/0004-637x/782/1/50

Cited by 23 publications

(16 citation statements)

References 54 publications

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“…These findings indicate that the chemical enrichment in lowmass dwarfs has been slower than in the Galactic halo (Cayrel et al 2004) and in the Galactic bulge (Lagioia et al 2014). This means that dwarf galaxies might have played a minor role in building up the Galactic spheroid (Leaman et al 2013;Stetson et al 2014;Fiorentino et al 2015).…”

Section: Introductionmentioning

confidence: 93%

The Carina Project

Fabrizio

Nonino

Bono

et al. 2015

A&A

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We have performed a new abundance analysis of Carina red giant (RG) stars from spectroscopic data collected with UVES (high spectral resolution) and FLAMES/GIRAFFE (high and medium resolution) at ESO/VLT. The former sample includes 44 RGs, while the latter consists of 65 (high-resolution) and ∼800 (medium-resolution) RGs, covering a significant fraction of the galaxy's RG branch, and red clump stars. To improve the abundance analysis at the faint magnitude limit, the FLAMES/GIRAFFE data were divided into ten surface gravity and effective temperature bins. The spectra of the stars belonging to the same gravity and temperature bin were stacked. This approach allowed us to increase the signal-to-noise ratio in the faint magnitude limit (V ≥ 20.5 mag) by at least a factor of five. We took advantage of the new photometry index c U,B,I introduced recently as an age and probably a metallicity indicator to split stars along the red giant branch. These two stellar populations display distinct [Fe/H] and [Mg/H] distributions: their mean iron abundances are −2.15 ± 0.06 dex (σ = 0.28), and −1.75 ± 0.03 dex (σ = 0.21), respectively. The two iron distributions differ at the 75% level. This supports preliminary results. Moreover, we found that the old and intermediate-age stellar populations have mean [Mg/H] abundances of −1.91 ± 0.05 dex (σ = 0.22) and −1.35 ± 0.03 dex (σ = 0.22); these differ at the 83% level. Carina's α-element abundances agree, within 1σ, with similar abundances for field halo stars and for cluster (Galactic and Magellanic) stars. The same outcome applies to nearby dwarf spheroidals and ultra-faint dwarf galaxies in the iron range covered by Carina stars. Finally, we found evidence of a clear correlation between Na and O abundances, thus suggesting that Carina's chemical enrichment history is quite different from that in the globular clusters.

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Section: Introductionmentioning

confidence: 93%

The Carina Project

Fabrizio

Nonino

Bono

et al. 2015

A&A

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“…Barbuy et al (2006) and Barbuy et al (2007) presented nearly identical arguments for the Galactic bulge globular clusters HP-1 and NGC 6558, and thus the indication of an old relative age at [Fe/H]= −1.0 is a trend and not an anomaly. Interested readers are referred to Dotter et al (2010) and Milone et al (2014) for reviews for the link between age and horizontal branch morphology in Galactic globular clusters.…”

Section: Argument For An Exceptionally Oldermentioning

confidence: 99%

The Controversial Star-Formation History and Helium Enrichment of the Milky Way Bulge

Nataf

2016

Publ. Astron. Soc. Aust.

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The stellar population of the Milky Way bulge is thoroughly studied, with a plethora of measurements from virtually the full suite of instruments available to astronomers. It is thus perhaps surprising that alongside well-established results lies some substantial uncertainty in its star-formation history. Cosmological models predict the bulge to host the Galaxy's oldest stars for [Fe/H] −1, and this is demonstrated by RR Lyrae stars and globular cluster observations. There is consensus that bulge stars with [Fe/H] 0 are older than t ≈ 10 Gyr. However, at super-solar metallicity, there is a substantial unresolved discrepancy. Data from spectroscopic measurements of the main-sequence turnoff and subgiant branch, the abundances of asymptotic giant branch stars, the period distribution of Mira variables, the chemistry and central-star masses of planetary nebulae, all suggest a substantial intermediate-age population (t ≈ 3 Gyr). This is in conflict with predictions from cosmologically-motivated chemical evolution models and photometric studies of the main-sequence turnoff region, which both suggest virtually no stars younger than t ≈ 8 Gyr. A possible resolution to this conflict is enhanced helium-enrichment, as this would shift nearly all of the age estimates in the direction of decreasing discrepancy. Enhanced helium-enrichment is also arguably suggested by measurements of the red giant branch bump and the R-parameter.

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“…It relies on the difference either in magnitude or in color between the MSTO and a well defined knee in the low-mass regime of the main sequence (MSK). The MSK has already been detected in several GCs -ω Cen ; M4 (Pulone et al, 1999;Milone et al, 2014;Braga et al, 2015;Correnti et al, 2016); NGC 3201 (Bono et al, 2010); 47 Tuc (Lagioia et al, 2014;Correnti et al, 2016); NGC 2808 (Milone et al, 2012;Massari et al, 2016a); M71 (Di Cecco et al, 2015); NGC 6752 (Correnti et al, 2016)), in intermediate-age open clusters (Sarajedini et al, 2009b;An et al, 2008An et al, , 2009 and in the field of the Galactic bulge (Zoccali et al, 2000) by using either near-infrared (NIR) and/or optical-NIR photometry.…”

Section: A New Approach For Absolute Age Estimatesmentioning

confidence: 91%

“…The pointing is typically located across the center of the cluster and in these regions cluster stars outnumber field stars. This rule of thumb does not apply to clusters either located or projected onto crowded Galactic regions such as the Bulge and Galactic thin disk (Zoccali et al, 2001a;Ferraro et al, 2009;Lagioia et al, 2014) or nearby dwarf galaxies (Kalirai et al, 2012). A significant step forward in dealing with this problem was provided by HST photometry.…”

Section: The Main Sequence Turn Offmentioning

confidence: 99%

Impact of Distance Determinations on Galactic Structure. II. Old Tracers

Kunder¹,

Valenti²,

Dall’Ora³

et al. 2018

Space Sciences Series of ISSI

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Here we review the efforts of a number of recent results that use old tracers to understand the build up of the Galaxy. Details that lead directly to using these old tracers to measure distances are discussed. We concentrate on the following: (1) the structure and evolution of the Galactic bulge and inner Galaxy constrained from the dynamics of individual stars residing therein;(2) the spatial structure of the old Galactic bulge through photometric observations of RR Lyrae-type stars; (3) the three-dimensional structure, stellar density, mass, chemical composition, and age of the Milky Way bulge as traced by its old stellar populations; (4) an overview of RR Lyrae stars known in the ultra-faint dwarfs and their relation to the Galactic halo; and (5) different approaches for estimating absolute and relative cluster ages.

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On the Kinematic Separation of Field and Cluster Stars Across the Bulge Globular Ngc 6528

Cited by 23 publications

References 54 publications

The Carina Project

The Carina Project

The Controversial Star-Formation History and Helium Enrichment of the Milky Way Bulge

Impact of Distance Determinations on Galactic Structure. II. Old Tracers

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