Asymptotic giant branch stars in NGC 6822: Probes of star formation history

1994 ◽  
Vol 425 ◽  
pp. L9 ◽  
Author(s):  
C. Gallart ◽  
A. Aparicio ◽  
C. Chiosi ◽  
G. Bertelli ◽  
J. M. Vilchez
Keyword(s):  
Star Formation ◽  
Asymptotic Giant Branch ◽  
Star Formation History ◽  
Asymptotic Giant Branch Stars ◽  
Formation History ◽  
Ngc 6822 ◽  
Giant Branch Stars

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

2016 ◽  
Vol 33 ◽  
Author(s):  
David M. Nataf
Keyword(s):  
Star Formation ◽  
Main Sequence ◽  
Milky Way ◽  
Central Star ◽  
Asymptotic Giant Branch ◽  
Star Formation History ◽  
Asymptotic Giant Branch Stars ◽  
Rr Lyrae ◽  
Formation History ◽  
Solar Metallicity

AbstractThe 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.

scholarly journals A critical look at the role of AGB stars in stellar population synthesis

1999 ◽  
Vol 191 ◽  
pp. 579-588 ◽  
Author(s):  
A. Lançon
Keyword(s):  
Asymptotic Giant Branch ◽  
Star Formation History ◽  
Asymptotic Giant Branch Stars ◽  
Agb Stars ◽  
Population Synthesis ◽  
Set Constraints ◽  
Formation History ◽  
Ir Emission ◽  
Giant Branch Stars

Asymptotic giant branch stars are essential contributors to the near and mid-IR emission of intermediate age (108-109 yr old) stellar populations. Detecting this light will set constraints on the star formation history in galaxies and, conversely, the search for AGB signatures in well studied populations will help us reduce some of the still large uncertainties in AGB models. This paper reviews how AGB stars are currently included in population synthesis models and which spectral features can be used to identify their emission in galaxy light; targets for observational tests are suggested, and some observational and theoretical difficulties are discussed.

scholarly journals Extragalactic archaeology with the C, N, and O chemical abundances

2018 ◽  
Vol 610 ◽  
pp. L16 ◽  
Author(s):  
Fiorenzo Vincenzo ◽  
Chiaki Kobayashi
Keyword(s):  
Star Formation ◽  
Asymptotic Giant Branch ◽  
Star Formation History ◽  
Asymptotic Giant Branch Stars ◽  
Chemical Abundances ◽  
Star Forming ◽  
Chemical Enrichment ◽  
Formation History ◽  
The Galaxy ◽  
Disc Galaxies

We predict how the C, N, and O abundances within the interstellar medium of galaxies evolve as functions of the galaxy star formation history (SFH). We adopt a hydrodynamical cosmological simulation, focusing on three star-forming disc galaxies with different SFHs. By assuming failed supernovae, we can predict an increasing trend of the gas-phase N/O–O/H abundance diagram, which was not produced in our previous simulations without failed supernovae. At high redshifts, contrary to the predictions of classical chemical evolution models with instantaneous mixing approximation, we find almost flat trends in the N/O–O/H diagram, which are due to the contribution of intermediate-mass stars together with an inhomogeneous chemical enrichment. Finally, we also predict that the average N/O and C/O steadily increase as functions of time, while the average C/N decreases, due to the mass and metallicity dependence of the yields of asymptotic giant branch stars; such variations are more marked during more intense star formation episodes. Our predictions on the CNO abundance evolution can be used to study the SFH of disc galaxies with the James Webb Space Telescope.

scholarly journals Carbon stars as standard candles – II. The median J magnitude as a distance indicator

2020 ◽  
Vol 501 (1) ◽  
pp. 933-947
Author(s):  
Javiera Parada ◽  
Jeremy Heyl ◽  
Harvey Richer ◽  
Paul Ripoche ◽  
Laurie Rousseau-Nepton
Keyword(s):  
Luminosity Function ◽  
Asymptotic Giant Branch ◽  
Distance Modulus ◽  
Asymptotic Giant Branch Stars ◽  
Luminosity Functions ◽  
Best Fitting ◽  
Distance Indicator ◽  
Ngc 6822 ◽  
The Given ◽  
Giant Branch Stars

ABSTRACT We introduce a new distance determination method using carbon-rich asymptotic giant branch stars (CS) as standard candles and the Large and Small Magellanic Clouds (LMC and SMC) as the fundamental calibrators. We select the samples of CS from the ((J − Ks)0, J0) colour–magnitude diagrams, as, in this combination of filters, CS are bright and easy to identify. We fit the CS J-band luminosity functions using a Lorentzian distribution modified to allow the distribution to be asymmetric. We use the parameters of the best-fitting distribution to determine if the CS luminosity function of a given galaxy resembles that of the LMC or SMC. Based on this resemblance, we use either the LMC or SMC as the calibrator and estimate the distance to the given galaxy using the median J magnitude ($\overline{J}$) of the CS samples. We apply this new method to the two Local Group galaxies NGC 6822 and IC 1613. We find that NGC 6822 has an ‘LMC-like’ CS luminosity function, while IC 1613 is more ‘SMC-like’. Using the values for the median absolute J magnitude for the LMC and SMC found in Paper I we find a distance modulus of μ0 = 23.54 ± 0.03 (stat) for NGC 6822 and μ0 = 24.34 ± 0.05 (stat) for IC 1613.

scholarly journals Recovering the Star Formation History of IC1613 Dwarf Galaxy Using Evolved Stars

2018 ◽  
Vol 14 (S344) ◽  
pp. 77-80
Author(s):  
Seyed Azim Hashemi ◽  
Atefeh Javadi ◽  
Jacco Th. van Loon
Keyword(s):  
Star Formation ◽  
Dwarf Galaxy ◽  
Stellar Populations ◽  
Asymptotic Giant Branch ◽  
Star Formation History ◽  
Evolved Stars ◽  
Formation History ◽  
The Galaxy ◽  
Red Supergiants ◽  
Period Variable

AbstractDetermining the star formation history (SFH) is key to understand the formation and evolution of dwarf galaxies. Recovering the SFH in resolved galaxies is mostly based on deep colour–magnitude diagrams (CMDs), which trace the signatures of multiple evolutionary stages of their stellar populations. In distant and unresolved galaxies, the integrated light of the galaxy can be decomposed, albeit made difficult by an age–metallicity degeneracy. Another solution to determine the SFH of resolved galaxies is based on evolved stars; these luminous stars are the most accessible tracers of the underlying stellar populations and can trace the entire SFH. Here we present a novel method based on long period variable (LPV) evolved asymptotic giant branch (AGB) stars and red supergiants (RSGs). We applied this method to reconstruct the SFH for IC1613, an irregular dwarf galaxy at a distance of 750 kpc. Our results provide an independent confirmation that no major episode of star formation occurred in IC1613 over the past 5 Gyr.

The Local Group Dwarf Irregular Galaxy NGC 6822.III. The Recent Star Formation History

1996 ◽  
Vol 112 ◽  
pp. 2596 ◽  
Author(s):  
C. Gallart ◽  
A. Aparicio ◽  
G. Bertelli ◽  
C. Chiosi
Keyword(s):  
Star Formation ◽  
Local Group ◽  
Star Formation History ◽  
Irregular Galaxy ◽  
Formation History ◽  
Ngc 6822

scholarly journals The Star Formation History of NGC 6822

2001 ◽  
Vol 122 (5) ◽  
pp. 2490-2523 ◽  
Author(s):  
Ted K. Wyder
Keyword(s):  
Star Formation ◽  
Star Formation History ◽  
Formation History ◽  
History Of ◽  
Ngc 6822
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