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

Nataf, David M.

doi:10.1017/pasa.2015.38

Cited by 40 publications

(20 citation statements)

References 95 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…An assessment of the uncertainties connected with stellar evolutionary models is more difficult. Even the models of single stars differ significantly among different authors because of different input physics (Verbunt & Phinney 1995;Nataf et al 2012). In particular, the timescales of the consecutive evolutionary phases and radii of the models may differ by several percent.…”

Section: Discussionmentioning

confidence: 99%

Model computations of blue stragglers and W UMa-type stars in globular clusters

Stępień

Kiraga

2015

A&A

View full text Add to dashboard Cite

Context. It was recently demonstrated that contact binaries occur in globular clusters (GCs) only immediately below turn-off point and in the region of blue straggler stars (BSs). In addition, observations indicate that at least a significant fraction of BSs in these clusters was formed by the binary mass-transfer mechanism. Aims. The aim of our present investigation is to obtain and analyze a set of evolutionary models of cool, close detached binaries with a low metal abundance, which are characteristic of GC. Methods. We computed the evolution of 975 models of initially detached, cool close binaries with different initial parameters. The models include mass exchange between components as well as mass and angular momentum loss due to the magnetized winds for very low-metallicity binaries with Z = 0.001. The models are interpreted in the context of existing data on contact binary and blue straggler members of GCs. The models are based on our recently developed code for evolutionary modeling of cool close and contact binaries. Results. The model parameters agree well with the observed positions of the GC contact binaries in the Hertzsprung-Russell diagram, and we achieve detailed parameters of several individual contact and near-contact binaries. Contact binaries in the lower part of the cluster main sequence are absent because there are no binaries with initial orbital periods shorter than 1.5 d. Contact binaries end their evolution as mergers that appear in the BS region. Binary-formed BSs populate the whole observed BS region in a GC, but a gap is visible between low-mass mergers that are concentrated along the zero-age main sequence and binary BSs occupying the red part of the BS region. Very few binary mergers are expected to rotate rapidly and/or possess chemical peculiarities resulting from the exposure of the layers processed by CNO nuclear reactions. All other binary mergers are indistinguishable from the collisionally formed mergers. The results show that binary-formed BSs may constitute at least a substantial fraction of all BSs in a GC.

show abstract

Section: Discussionmentioning

confidence: 99%

Model computations of blue stragglers and W UMa-type stars in globular clusters

Stępień

Kiraga

2015

A&A

View full text Add to dashboard Cite

show abstract

“…We then convert these errors to distance offsets using m = + ( ) d log 1 5, where d is in parsecs and we assume μ=14.6. Lastly, we interpolate the errors and offsets of the Milky Way relations relative to the LMC, where the track with age 10 Gyr, 0.27 helium, and [Fe/H]=−0.1 is used to approximate the Milky Way Bulge (Nataf 2016;Bensby et al 2017). The results of Choudhury et al (2016) and Bensby et al (2017) indicate that the Bulge is at least ∼0.30 dex more metal-rich, on average, than the LMC, and the difference may be as much as 0.40 dex once the alpha-enhancements are taken into account.…”

Section: Effects Of Age and Metallicitymentioning

confidence: 99%

The Mira-based Distance to the Galactic Center

Qin¹,

Nataf²,

Zakamska³

et al. 2018

ApJ

Self Cite

View full text Add to dashboard Cite

Mira variables are useful distance indicators, due to their high luminosities and well-defined period-luminosity relation. We select 1863 Miras from SAAO and MACHO observations to examine their use as distance estimators in the Milky Way. We measure a distance to the Galactic center of R 0 =7.9±0.3 kpc, which is in good agreement with other literature values. The uncertainty has two components of ∼0.2 kpc each: the first is from our analysis and predominantly due to interstellar extinction, the second is due to zero-point uncertainties extrinsic to our investigation, such as the distance to the Large Magellanic Cloud (LMC). In an attempt to improve existing period-luminosity calibrations, we use theoretical models of Miras to determine the dependence of the period-luminosity relation on age, metallicity, and helium abundance, under the assumption that Miras trace the bulk stellar population. We find that at a fixed period of = P log 2.4, changes in the predicted K s magnitudes can be approximated byGyr 0.021 0.01 , and these coefficients are nearly independent of period. The expected overestimate in the Galactic center distance from using an LMC-calibrated relation is ∼0.3 kpc. This prediction is not validated by our analysis; a few possible reasons are discussed. We separately show that while the predicted color-color diagrams of solarneighborhood Miras work well in the near-infrared; though, there are offsets from the model predictions in the optical and mid-infrared.

show abstract

“…This is a stellar population quite different from that of the local disk. In particular, the vast majority of Galactic bulge (excluding the nucleus) stars are > ∼ 8 Gyr old [42] whereas the Galactic disk environment has experienced star formation up to the present day. This difference may well mean that the stellar progenitors of the putative GCE region MSPs are systematically older than the progenitors of local MSPs (and, indeed, that the MSP population is systematically older and dimmer given that MSPs spin down and become less luminous over time).…”

mentioning

confidence: 99%

Consistency between the luminosity function of resolved millisecond pulsars and the galactic center excess

Ploeg

Gordon

Crocker

et al. 2017

J. Cosmol. Astropart. Phys.

View full text Add to dashboard Cite

Fermi Large Area Telescope data reveal an excess of GeV gamma rays from the direction of the Galactic Center and bulge. Several explanations have been proposed for this excess including an unresolved population of millisecond pulsars (MSPs) and self-annihilating dark matter. It has been claimed that a key discriminant for or against the MSP explanation can be extracted from the properties of the luminosity function describing this source population. Specifically, is the luminosity function of the putative MSPs in the Galactic Center consistent with that characterizing the resolved MSPs in the Galactic disk? To investigate this we have used a Bayesian Markov Chain Monte Carlo to evaluate the posterior distribution of the parameters of the MSP luminosity function describing both resolved MSPs and the Galactic Center excess. At variance with some other claims, our analysis reveals that, within current uncertainties, both data sets can be well fit with the same luminosity function.

show abstract

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

Cited by 40 publications

References 95 publications

Model computations of blue stragglers and W UMa-type stars in globular clusters

Model computations of blue stragglers and W UMa-type stars in globular clusters

The Mira-based Distance to the Galactic Center

Consistency between the luminosity function of resolved millisecond pulsars and the galactic center excess

Contact Info

Product

Resources

About