Elemental Abundances in M31: Alpha and Iron Element Abundances from Low-resolution Resolved Stellar Spectroscopy in the Stellar Halo

AbstractChemical and kinematical information is needed in order to understand and trace the formation history of our Galaxy. In the homogeneous large sample of F and G stars in the survey by Nordström et al. (2004), groups of stars with orbital parameters different from field stars were found by Helmi et al. (2006). Simulations of disrupted satellites showed that the groups had similar properties as infalling dwarf satellites would have after several Gyr. From high resolution spectra, we analyse elemental abundances of stars in 3 such groups with conserved kinematic properties. Here we present first results of s- and r- process element abundances in two such groups and compare with average field stars.

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Elemental Abundances in M31: A Comparative Analysis of Alpha and Iron Element Abundances in the the Outer Disk, Giant Stellar Stream, and Inner Halo of M31

The Astrophysical Journal ◽

10.3847/1538-4357/ab6659 ◽

2020 ◽

Vol 889 (2) ◽

pp. 177 ◽

Cited By ~ 5

Author(s):

Ivanna Escala ◽

Karoline M. Gilbert ◽

Evan N. Kirby ◽

Jennifer Wojno ◽

Emily C. Cunningham ◽

...

Keyword(s):

Comparative Analysis ◽

Element Abundances ◽

Elemental Abundances ◽

Outer Disk

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INVESTIGATION OF ELEMENT ABUNDANCES IN THE SURROUNDINGS OF GRB AFTERGLOWS

International Journal of Modern Physics D ◽

10.1142/s0218271808012942 ◽

2008 ◽

Vol 17 (09) ◽

pp. 1377-1382

Author(s):

S. SIMIĆ ◽

L. Č. POPOVIĆ

Keyword(s):

Gamma Ray ◽

High Energy ◽

Gamma Ray Bursts ◽

Spectral Lines ◽

Element Abundances ◽

Elemental Abundances ◽

Doppler Parameter ◽

Lower Redshift

In the case of high energy collimated outflows it is important to know the density and structure of material through which jets propagate. Here we present a simple study of the environment of GRBs where the relativistic ejecta travel during the event. We use observed spectral lines in the afterglow of gamma-ray bursts and by constructing the curve of growth for most redshifted lines, we extract the column densities and Doppler parameter. This can give us the overall picture of abundances in the vicinity of GRBs. Also, we compare this result with the spectral lines with lower redshift to examine the dependence of elemental abundances on the distance from GRB event.

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The Milky Way has no in-situ halo other than the heated thick disc

Astronomy and Astrophysics ◽

10.1051/0004-6361/201834929 ◽

2019 ◽

Vol 632 ◽

pp. A4 ◽

Cited By ~ 32

Author(s):

P. Di Matteo ◽

M. Haywood ◽

M. D. Lehnert ◽

D. Katz ◽

S. Khoperskov ◽

...

Keyword(s):

Galactic Halo ◽

The Sun ◽

Galactic Disc ◽

Elemental Abundances ◽

Thick Disc ◽

Halo Stars ◽

Stellar Halo ◽

Halo Population ◽

Astrometric Data

Previous studies based on the analysis of Gaia DR2 data have revealed that accreted stars, possibly originating from a single progenitor satellite, are a significant component of the halo of our Galaxy, potentially constituting most of the halo stars at [Fe/H] < −1 within a few kpc from the Sun and beyond. In this paper, we couple astrometric data from Gaia DR2 with elemental abundances from APOGEE DR14 to characterise the kinematics and chemistry of in-situ and accreted populations up to [Fe/H] ∼ −2. Accreted stars appear to significantly impact the galactic chemo–kinematic relations, not only at [Fe/H] < −1, but also at metallicities typical of the thick and metal-poor thin discs. They constitute about 60% of all stars at [Fe/H] < −1, the remaining 40% being made of (metal-weak) thick-disc stars. We find that the stellar kinematic fossil record shows the imprint left by this accretion event, which heated the old galactic disc. We are able to age-date this kinematic imprint, showing that the accretion occurred between nine and 11 Gyr ago, and that it led to the last significant heating of the galactic disc. An important fraction of stars with abundances typical of the (metal-rich) thick disc, and heated by this interaction, is now found in the galactic halo. Indeed, about half of the kinematically defined halo at few kpc from the Sun is composed of metal-rich thick-disc stars. Moreover, we suggest that this metal-rich thick-disc component dominates the stellar halo of the inner Galaxy. The new picture that emerges from this study is one where the standard, non-rotating in-situ halo population, the collapsed halo, seems to be more elusive than ever.

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Galactic or extragalactic chemical tagging for NGC 3201?

Astronomy and Astrophysics ◽

10.1051/0004-6361/201731957 ◽

2018 ◽

Vol 614 ◽

pp. A146 ◽

Cited By ~ 1

Author(s):

B. Dias ◽

I. Araya ◽

J. P. Nogueira-Cavalcante ◽

L. Saker ◽

A. Shokry

Keyword(s):

High Resolution ◽

Globular Cluster ◽

High Resolution Spectroscopy ◽

Low Resolution ◽

Element Abundances ◽

Giant Stars ◽

Mass Size ◽

Red Giant ◽

Process Element ◽

Size Relation

Context. The origin of the globular cluster (GC) NGC 3201 is under debate. Its retrograde orbit points to an extragalactic origin, but no further chemical evidence supports this idea. Light-element chemical abundances are useful to tag GCs and can be used to shed light on this discussion. Aims. Recently it was shown that the CN and CH indices are useful to identify GCs that are anomalous to those typically found in the Milky Way. A possible origin of anomalous clusters is the merger of two GCs and/or the nucleus of a dwarf galaxy. We aim to derive CN and CH band strengths for red giant stars in NGC3201 and compare these with photometric indices and high-resolution spectroscopy and discuss in the context of GC chemical tagging. Methods. We measure molecular band indices of S(3839) and G4300 for CN and CH, respectively from low-resolution spectra of red giant stars. Gravity and temperature effects are removed. Photometric indices are used to indicate further chemical information on C+N+O or s-process element abundances that are not derived from low-resolution spectra. Results. We found three groups in the CN–CH distribution. A main sequence (S1), a secondary less-populated sequence (S2), and a group of peculiar (pec) CN-weak and CH-weak stars, one of which was previously known. The three groups seem to have different C+N+O and/or s-process element abundances, to be confirmed by high-resolution spectroscopy. These are typical characteristics of anomalous GCs. The CN distribution of NGC 3201 is quadrimodal, which is more common in anomalous clusters. However, NGC 3201 does not belong to the trend of anomalous GCs in the mass-size relation. Conclusions. The globular cluster NGC 3201 shows signs that it can be chemically tagged as anomalous: it has an unusual CN–CH relation, indications that pec-S1-S2 is an increasing sequence of C+N+O or s-process element abundances, and a multi-modal CN distribution that seems to correlate with s-process element abundances. The non-anomalous characteristics are that it has a debatable Fe-spread and it does not follow the trend of mass size of all anomalous clusters. Three scenarios are postulated here: (i) if the sequence pec-S1-S2 has increasing C+N+O and s-process element abundances, NGC 3201 would be the first anomalous GC outside of the mass-size relation; (ii) if the abundances are almost constant, NGC 3201 would be the first non-anomalous GC with multiple CN–CH anti-correlation groups; or (iii) it would be the first anomalous GC without variations in C+N+O and s-process element abundances. In all cases, the definition of anomalous clusters and the scenario in which they have an extragalactic origin must be revised.

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Elemental Abundances in M31: Iron and Alpha Element Abundances in M31’s Outer Halo

The Astronomical Journal ◽

10.3847/1538-3881/ab9602 ◽

2020 ◽

Vol 160 (1) ◽

pp. 41 ◽

Cited By ~ 1

Author(s):

Karoline M. Gilbert ◽

Jennifer Wojno ◽

Evan N. Kirby ◽

Ivanna Escala ◽

Rachael L. Beaton ◽

...

Keyword(s):

Element Abundances ◽

Elemental Abundances

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The COMBS survey – I. Chemical origins of metal-poor stars in the Galactic bulge

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stz1847 ◽

2019 ◽

Vol 488 (2) ◽

pp. 2283-2300 ◽

Cited By ~ 5

Author(s):

Madeline Lucey ◽

Keith Hawkins ◽

Melissa Ness ◽

Martin Asplund ◽

Thomas Bensby ◽

...

Keyword(s):

Stellar Population ◽

Milky Way ◽

Distinct Population ◽

Elemental Abundances ◽

The Galaxy ◽

Stellar Halo ◽

Kinematic Studies ◽

Galactic Stellar Populations ◽

Target Metal ◽

Metallicity Distribution

ABSTRACT Chemistry and kinematic studies can determine the origins of stellar population across the Milky Way. The metallicity distribution function of the bulge indicates that it comprises multiple populations, the more metal-poor end of which is particularly poorly understood. It is currently unknown if metal-poor bulge stars ([Fe/H] <−1 dex) are part of the stellar halo in the inner most region, or a distinct bulge population or a combination of these. Cosmological simulations also indicate that the metal-poor bulge stars may be the oldest stars in the Galaxy. In this study, we successfully target metal-poor bulge stars selected using SkyMapper photometry. We determine the stellar parameters of 26 stars and their elemental abundances for 22 elements using R∼ 47 000 VLT/UVES spectra and contrast their elemental properties with that of other Galactic stellar populations. We find that the elemental abundances we derive for our metal-poor bulge stars have lower overall scatter than typically found in the halo. This indicates that these stars may be a distinct population confined to the bulge. If these stars are, alternatively, part of the innermost distribution of the halo, this indicates that the halo is more chemically homogeneous at small Galactic radii than at large radii. We also find two stars whose chemistry is consistent with second-generation globular cluster stars. This paper is the first part of the Chemical Origins of Metal-poor Bulge Stars (COMBS) survey that will chemodynamically characterize the metal-poor bulge population.

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Chemical differences and similarities among the kinematically selected thick disk, inner halo and outer halo stars

Proceedings of the International Astronomical Union ◽

10.1017/s1743921313006224 ◽

2013 ◽

Vol 9 (S298) ◽

pp. 71-76

Author(s):

Miho N. Ishigaki ◽

Wako Aoki ◽

Masashi Chiba

Keyword(s):

Thick Disk ◽

Chemical Diversity ◽

Elemental Abundance ◽

High Dispersion ◽

Chemical Abundance ◽

Chemical Enrichment ◽

Elemental Abundances ◽

Halo Stars ◽

Stellar Halo ◽

Homogeneous Chemical

AbstractChemical diversity among metal-poor stars in the old stellar components in the Milky Way (MW), namely the thick disk and stellar halo, provides clues to understanding the early chemodynamical evolution of our Galaxy. We present our results on a homogeneous chemical abundance analysis for nearby metal-poor stars likely belonging to the MW thick disk, inner and outer stellar halos. Abundances of alpha, sodium, iron-peak and neutron-capture elements in the sample stars have been estimated using high-resolution (R 50000) spectra obtained with the High Dispersion Spectrograph mounted on the Subaru Telescope. The derived abundances are used to examine differences and similarities in elemental abundance ratios among the kinematically defined thick disk, inner and outer halo subsamples in the metallicity range of −3.3 < [Fe/H] < −0.5. We show that, in the metallicity range of [Fe/H] < −2, the three subsamples are similar in most of the elemental abundances. On the other hand, in the higher metallicities, particularly in [Fe/H] > −1.5, the thick disk and the inner/outer halo subsamples show systematically different abundance ratios for some elements including alpha, sodium, zinc and europium. A modest difference in the sodium and zinc abundances between the inner- and outer halo subsamples is also identified. The observed distinct abundances of some elements among the three subsamples implies that their constituent stars originally formed in progenitor systems that have experienced different star formation and chemical enrichment histories.

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Elemental Abundances in M31: Properties of the Inner Stellar Halo

The Astrophysical Journal ◽

10.3847/1538-4357/abb474 ◽

2020 ◽

Vol 902 (1) ◽

pp. 51

Author(s):

Ivanna Escala ◽

Evan N. Kirby ◽

Karoline M. Gilbert ◽

Jennifer Wojno ◽

Emily C. Cunningham ◽

...

Keyword(s):

Elemental Abundances ◽

Stellar Halo

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Chemical analysis of CH stars – III. Atmospheric parameters and elemental abundances

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stz759 ◽

2019 ◽

Vol 486 (3) ◽

pp. 3266-3289 ◽

Cited By ~ 4

Author(s):

Meenakshi Purandardas ◽

Aruna Goswami ◽

Partha Pratim Goswami ◽

J Shejeelammal ◽

Thomas Masseron

Keyword(s):

Spectral Properties ◽

High Resolution Spectroscopy ◽

Limited Information ◽

Chemical Abundance ◽

Element Abundances ◽

Elemental Abundances ◽

Intermediate Mass Stars ◽

First Time ◽

Homogeneous Data ◽

Detailed Chemical

Abstract Elemental abundances of CH stars can provide observational constraints for theoretical studies on the nucleosynthesis and evolution of low- and intermediate-mass stars. However, available abundance data in literature are quite scanty. In our pursuit to generate a homogeneous data base of elemental abundances of CH stars we have performed a detailed chemical abundance study for a sample of 12 potential CH star candidates based on high-resolution spectroscopy. We present first time abundance analysis for the objects HE0308–1612, CD−281082, HD30443, and HD87853. For the other objects, although limited information is available, detailed chemical composition studies are missing. Our analysis shows CD−281082 to be a very metal-poor object with [Fe/H] = −2.45 and enriched in carbon with [C/Fe] = 2.19. With a ratio of [Ba/Eu] ∼ 0.02 the star satisfies the classification criteria of a CEMP-r/s star. The objects CD−382151 with [Fe/H] = −2.03 and HD30443 with [Fe/H] ∼ −1.68 are found to show the characteristic properties of CH stars. HE0308–1612 and HD87853 are found to be moderately metal poor with [Fe/H] ∼ −0.73; while HE0308–1612 is moderately enhanced with carbon ([C/Fe] ∼ 0.78) and shows the spectral properties of CH stars, the abundance of carbon could not be estimated for HD87853. Among the two moderately metal-poor objects, HD87080 ([Fe/H] = −0.48) shows near solar carbon abundance, and HD176021 ([Fe/H] = −0.63) is mildly enhanced in carbon with [C/Fe] = 0.52. HD176021 along with HD202020 a known binary, exhibit the characteristic properties of CH stars as far as the heavy element abundances are concerned. Five objects in our sample show spectral properties that are normally seen in barium stars.

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