scholarly journals Chemical abundances of 1111 FGK stars from the HARPS GTO planet search program. IV. Carbon and C/O ratios for Galactic stellar populations and planet hosts

2021 ◽  
Author(s):  
E. Delgado Mena ◽  
V. Adibekyan ◽  
N. C. Santos ◽  
M. Tsantaki ◽  
J. I. González Hernández ◽  
...  
Keyword(s):  
Stellar Populations ◽  
Chemical Abundances ◽  
Galactic Stellar Populations ◽  
Search Program

scholarly journals Nitrogen abundance in the X-ray halos of clusters and groups of galaxies

2018 ◽  
Vol 621 ◽  
pp. A9 ◽  
Author(s):  
Junjie Mao ◽  
Jelle de Plaa ◽  
Jelle S. Kaastra ◽  
Ciro Pinto ◽  
Liyi Gu ◽  
...  
Keyword(s):  
Stellar Populations ◽  
Chemical Abundances ◽  
X Ray ◽  
Groups Of Galaxies ◽  
Extraction Region ◽  
Chemical Enrichment ◽  
The Galaxy ◽  
Systematic Effects ◽  
Nitrogen Abundance ◽  
Galactic Stellar Populations

Context. Chemical abundances in the X-ray halos (also known as the intracluster medium, ICM) of clusters and groups of galaxies can be measured via prominent emission line features in their X-ray spectra. Elemental abundances are footprints of time-integrated yields of various stellar populations that have left their specific abundance patterns prior to and during the cluster and group evolution. Aim. We aim to constrain nitrogen abundances in the CHEmical Evolution RGS Sample (CHEERS), which contains 44 nearby groups and clusters of galaxies, to gain a better understanding of their chemical enrichment. Method. We examined the high-resolution spectra of the CHEERS sample and took various systematic effects in the spectral modelling into account. We compared the observed abundance ratios with those in the Galactic stellar populations and also with predictions from stellar yields (low- and intermediate-mass stars, massive stars, and degenerate stars). Results. The nitrogen abundance can only be well constrained (≳3σ) in one cluster of galaxies and seven groups of galaxies. The [O/Fe] – [Fe/H] relation of the ICM is comparable to that for the Galaxy, while the [N/Fe] and [N/O] ratios of the ICM are both higher than in the Galaxy. Future studies on nitrogen radial distributions are required to tell whether the obtained higher [N/Fe] and [N/O] ratios are biased as a result of the small extraction region (r/r500 ≲ 0.05) that we adopt here. Since abundances of odd-Z elements are more sensitive to the initial metallicity of stellar populations, accurate abundance measurements of N, Na, and Al are required to better constrain the chemical enrichment in the X-ray halos of clusters and groups of galaxies.

scholarly journals The Metallicity Distribution of Late Type Dwarfs

1998 ◽  
Vol 11 (1) ◽  
pp. 571-571
Author(s):  
M. Haywood ◽  
J. Palasi ◽  
A. Gómez ◽  
L. Meillon Dasgal
Keyword(s):  
Star Formation Rate ◽  
Formation Rate ◽  
Angular Separation ◽  
Stellar Populations ◽  
Late Type ◽  
Limited Sample ◽  
Hipparcos Catalogue ◽  
Galactic Stellar Populations ◽  
Metallicity Distribution ◽  
Hr Diagram

The Hipparcos catalogue provides an accurate and extensive sampling of the solar neighbourhood HR diagram. The morphology of this diagram depends on selection criteria of the catalogue such as the limiting magnitude, angular separation and on the characteristics of the stellar populations near the sun (space density, metallicity, star formation rate, etc). Since the Hipparcos data are so accurate, one needs to model precisely the different selection bias and, at the same time, parametrize models of the galactic stellar populations with sufficient flexibility that as much information as possible can be grasped from the catalogue. Comparisons between our model and the Hipparcos catalogue will be presented elsewhere. Since the quantity of information contained in the Hipparcoscatalogue is so important, models ought to be complex, and external contraints, obtained prior to any general comparison with the model, are welcome. A major factor that influences the distribution of the stars in the HR diagram is the metallicity. For the late type stars, the metallicity distribution can be best studied by re-analysing a volume-limited sample of stars from the catalogue.

scholarly journals Chemical abundances in LMC stellar populations

2008 ◽  
Vol 480 (2) ◽  
pp. 379-395 ◽  
Author(s):  
L. Pompéia ◽  
V. Hill ◽  
M. Spite ◽  
A. Cole ◽  
F. Primas ◽  
...  
Keyword(s):  
Stellar Populations ◽  
Chemical Abundances

scholarly journals Chemical abundances in LMC stellar populations

2013 ◽  
Vol 560 ◽  
pp. A44 ◽  
Author(s):  
M. Van der Swaelmen ◽  
V. Hill ◽  
F. Primas ◽  
A. A. Cole
Keyword(s):  
Stellar Populations ◽  
Chemical Abundances

Abundance ratios & ages of stellar populations in HARPS-GTO sample

2017 ◽  
Vol 12 (S330) ◽  
pp. 156-159 ◽  
Author(s):  
E. Delgado Mena ◽  
M. Tsantaki ◽  
V. Zh. Adibekyan ◽  
S. G. Sousa ◽  
N. C. Santos ◽  
...  
Keyword(s):  
Chemical Evolution ◽  
Thin Disk ◽  
Thick Disk ◽  
Heavy Elements ◽  
Galactic Chemical Evolution ◽  
Chemical Abundances ◽  
Homogeneous Sample ◽  
Different Populations ◽  
Search Program ◽  
Cu And Zn

AbstractIn this work we present chemical abundances of heavy elements (Z>28) for a homogeneous sample of 1059 stars from HARPS planet search program. We also derive ages using parallaxes from Hipparcos and Gaia DR1 to compare the results. We study the [X/Fe] ratios for different populations and compare them with models of Galactic chemical evolution. We find that thick disk stars are chemically disjunt for Zn adn Eu. Moreover, the high-alpha metal-rich population presents an interesting behaviour, with clear overabundances of Cu and Zn and lower abundances of Y and Ba with respect to thin disk stars. Several abundance ratios present a significant correlation with age for chemically separated thin disk stars (regardless of their metallicity) but thick disk stars do not present that behaviour. Moreover, at supersolar metallicities the trends with age tend to be weaker for several elements.

scholarly journals Deep Multi-Colour Starcounts

1994 ◽  
Vol 161 ◽  
pp. 423-424
Author(s):  
I.N. Reid ◽  
S.R. Majewski
Keyword(s):  
Standard Model ◽  
Stellar Population ◽  
Stellar Populations ◽  
The North ◽  
Halo Stars ◽  
The Standard Model ◽  
The Galaxy ◽  
Best Fitting ◽  
Galactic Stellar Populations ◽  
North Galactic

Starcounts remain one of the most effective methods of probing the structure of the Galactic stellar populations. However, studies of the distribution at large distances above the Plane demand accurate photometry extending to faint magnitudes (V > 20), and such datasets are still rare. We (Reid & Majewski 1993) have analyzed data from one field — Majewski's (1992) UJF observations of SA57, the North Galactic Pole field. Our results revealed significant discrepancies with the standard model of the Galaxy (see refs. in Reid & Majewski), notably a paucity in the number of halo stars by a factor of two and the presence of a factor of two more disk stars than predicted — sufficient stars that the disk is the majority stellar population, outnumbering halo stars 2:1 even at V = 21. Majewski et al. (1993) has obtained UJFN photographic data for several other fields, and Fig. 1 shows a preliminary comparison of these observations with the predictions of the best-fitting SA57 model. Given that none of the parameters have been modified, the agreement is surprisingly good.

A review of the chemical abundances and kinematics of the Galactic bulge

2013 ◽  
Vol 9 (S298) ◽  
pp. 28-39 ◽  
Author(s):  
Livia Origlia
Keyword(s):  
Galactic Center ◽  
State Of The Art ◽  
Complex Structure ◽  
Stellar Populations ◽  
Galactic Bulge ◽  
Future Perspectives ◽  
Chemical Abundances ◽  
Center Region ◽  
Infrared Surveys

AbstractThis review will attempt to draw a state of the art observational picture of the Galactic bulge. The main chemical, kinematic and evolutionary properties of the gas and stellar populations in the barred bulge and towards the Galactic center region will be discussed in the context of the possible formation scenarios. Future perspectives for our comprehension of the complex structure of the Galactic bulge from ongoing and foreseen optical and infrared surveys will be also highlighted.

scholarly journals Milky Way demographics with the VVV survey

2018 ◽  
Vol 619 ◽  
pp. A4 ◽  
Author(s):  
Javier Alonso-García ◽  
Roberto K. Saito ◽  
Maren Hempel ◽  
Dante Minniti ◽  
Joyce Pullen ◽  
...  
Keyword(s):  
Near Infrared ◽  
Milky Way ◽  
Stellar Populations ◽  
Wide Field ◽  
Public Survey ◽  
Wide Field Of View ◽  
Spread Function ◽  
The Galaxy ◽  
Infrared Wavelengths ◽  
Galactic Stellar Populations

Context. The inner regions of the Galaxy are severely affected by extinction, which limits our capability to study the stellar populations present there. The Vista Variables in the Vía Láctea (VVV) ESO Public Survey has observed this zone at near-infrared wavelengths where reddening is highly diminished. Aims. By exploiting the high resolution and wide field-of-view of the VVV images we aim to produce a deep, homogeneous, and highly complete database of sources that cover the innermost regions of our Galaxy. Methods. To better deal with the high crowding in the surveyed areas, we have used point spread function (PSF)-fitting techniques to obtain a new photometry of the VVV images, in the ZY JHKs near-infrared filters available. Results. Our final catalogs contain close to one billion sources, with precise photometry in up to five near-infrared filters, and they are already being used to provide an unprecedented view of the inner Galactic stellar populations. We make these catalogs publicly available to the community. Our catalogs allow us to build the VVV giga-CMD, a series of color-magnitude diagrams of the inner regions of the Milky Way presented as supplementary videos. We provide a qualitative analysis of some representative CMDs of the inner regions of the Galaxy, and briefly mention some of the studies we have developed with this new dataset so far.

scholarly journals Azimuthal variations of oxygen abundance profiles in star-forming regions of disc galaxies in EAGLE simulations

2019 ◽  
Vol 491 (4) ◽  
pp. 4894-4901
Author(s):  
Martín Solar ◽  
Patricia B Tissera ◽  
Jose A Hernandez-Jimenez
Keyword(s):  
Stellar Populations ◽  
Chemical Abundances ◽  
Oxygen Abundance ◽  
Star Forming ◽  
Chemical Enrichment ◽  
Numerical Resolution ◽  
Star Forming Regions ◽  
Star Formation Activity ◽  
Large Dispersion ◽  
The Mean

ABSTRACT The exploration of the spatial distribution of chemical abundances in star-forming regions of galactic discs can help us to understand the complex interplay of physical processes that regulate the star formation activity and the chemical enrichment across a galaxy. We study the azimuthal variations of the normalized oxygen abundance profiles in the highest numerical resolution run of the Evolution and Assembly of GaLaxies and their Environments (EAGLE) Project at $z$ = 0. We use young stellar populations to trace the abundances of star-forming regions. Oxygen profiles are estimated along different line of sights from a centrally located observer. The mean azimuthal variation in the EAGLE discs are ∼0.12 ± 0.03 dex $R_{\rm eff}^{-1}$ for slopes and ∼0.12 ± 0.03 dex for the zero-points, in agreement with previous works. Metallicity gradients measured along random directions correlate with those determined by averaging over the whole discs, although with a large dispersion. We find a slight trend for higher azimuthal variations in the disc components of low star-forming and bulge-dominated galaxies. We also investigate the metallicity profiles of stellar populations with higher and lower levels of enrichment than the average metallicity profiles, and we find that high star-forming regions with high metallicity tend to have slightly shallower metallicity slopes compared with the overall metallicity gradient. The simulated azimuthal variations in the EAGLE discs are in agreement with observations, although the large variety of metallicity gradients would encourage further exploration of the metal mixing in numerical simulations.

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