Using the multi-object adaptive optics demonstrator RAVEN to observe metal-poor stars in and towards the Galactic Centre

Lamb, Masen; Venn, Kim A.; Andersen, David R.; Oya, Shin; Shetrone, Matthew; Fattahi, Azadeh; Howes, L. M.; Asplund, Martin; Lardière, Olivier; Akiyama, Masayuki; Ono, Yoshito; Terada, Hiroshi; Hayano, Yutaka; Suzuki, Go; Blain, Celia; Jackson, Kate; Correia, Carlos; Youakim, Kris; Bradley, Colin

doi:10.1093/mnras/stw2865

Cited by 20 publications

(12 citation statements)

References 102 publications

(176 reference statements)

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“…Although magnitude ranges often limit the distance range probed, there are still significant differences in the chemical properties of EMP stars and their present-day location and kinematics in the Galaxy (Cayrel et al 2004;Frebel et al 2006;Bonifacio et al 2009;Carollo et al 2010Carollo et al , 2012An et al 2013;Starkenburg et al 2013;Skúladóttir et al 2015). This dependence of chemical composition on Galactic environment has been further emphasized by recent studies in the bulge of the Galaxy, namely that EMP stars in the halo are often enhanced in carbon, whereas EMP stars in the bulge rarely exhibit carbon enhancement (Howes et al 2015(Howes et al , 2016Koch et al 2016;Lamb et al 2017).…”

Section: Introductionmentioning

confidence: 91%

The Pristine survey – III. Spectroscopic confirmation of an efficient search for extremely metal-poor stars

Youakim

Starkenburg

Aguado

et al. 2017

Monthly Notices of the Royal Astronomical Society

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The Pristine survey is a narrow-band, photometric survey focused around the wavelength region of the Ca ii H & K absorption lines, designed to efficiently search for extremely metal-poor stars. In this work, we use the first results of a medium-resolution spectroscopic follow-up to refine the selection criteria for finding extremely metal-poor stars ([Fe/H] ≤ −3.0) in the Pristine survey. We consider methods by which stars can be selected from available broad-band and infrared photometry plus the additional Pristine narrow-band photometry. The spectroscopic sample presented in this paper consists of 205 stars in the magnitude range 14 < V < 18. Applying the photometric selection criteria cuts the sample down to 149 stars, and from these we report a success rate of 70% for finding stars with [Fe/H] ≤ −2.5 and 22% for finding stars with [Fe/H] ≤ −3.0. These statistics compare favourably with other surveys that search for extremely metal-poor stars, namely an improvement by a factor of ∼ 4 − 5 for recovering stars with [Fe/H] ≤ −3.0. In addition, Pristine covers a fainter magnitude range than its predecessors, and can thus probe deeper into the Galactic halo.This paper is based on photometric data obtained with CFHT programs 15AC20, 15AF14, 15AF97, 16AC20, 16AC98, and 16AF14 and spectroscopic data from INT and WHT programs C71 and N5 in semester 2016A. †

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Section: Introductionmentioning

confidence: 91%

The Pristine survey – III. Spectroscopic confirmation of an efficient search for extremely metal-poor stars

Youakim

Starkenburg

Aguado

et al. 2017

Monthly Notices of the Royal Astronomical Society

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“…In addition, about a third of the [Fe/H] < −2.5 stars 1 in the Galactic halo show very high enhancements in carbon (the carbon-enhanced metal-poor stars, "CEMP"; Yong et al 2013;Aguado et al 2019a also see Kielty et al 2017;Mardini et al 2019), discussed as a signature of the earliest chemical enrichment in the Universe. However, at least one ultra metal-poor star is not carbonenhanced (SDSS J102915+172927, Caffau et al 2012), and the known metal-poor stars in the Galactic bulge do not show carbon-enhancements (Howes et al 2016;Lamb et al 2017). Norris et al (2013) suggest that there are likely multiple chemical enrichment pathways for old metal-poor stars dependent on the star formation environment, and also possibly binary mass transfer effects (also see discussions by Starkenburg et al 2014;Arentsen et al 2019).…”

Section: Introductionmentioning

confidence: 99%

The Pristine survey – IX. CFHT ESPaDOnS spectroscopic analysis of 115 bright metal-poor candidate stars

Venn

Kielty

Sestito

et al. 2019

Monthly Notices of the Royal Astronomical Society

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A chemo-dynamical analysis of 115 metal-poor candidate stars selected from the narrow-band Pristine photometric survey is presented based on CFHT highresolution ESPaDOnS spectroscopy. We have discover 28 new bright (V < 15) stars with [Fe/H]< −2.5 and 5 with [Fe/H]< −3.0 for success rates of 40% (28/70) and 19% (5/27), respectively. A detailed model atmospheres analysis is carried out for the 28 new metal-poor stars. Stellar parameters were determined from SDSS photometric colours, Gaia DR2 parallaxes, MESA/MIST stellar isochrones, and the initial Pristine survey metallicities, following a Bayesian inference method. Chemical abundances are determined for 10 elements (Na, Mg, Ca, Sc, Ti, Cr, Fe, Ni, Y, Ba). Most stars show chemical abundance patterns that are similar to the normal metal-poor stars in the Galactic halo; however, we also report the discoveries of a new r-process rich star, a new CEMP-s candidate with [Y/Ba]>0, and a metal-poor star with very low [Mg/Fe]. The kinematics and orbits for all of the highly probable metal-poor candidates are determined by combining our precision radial velocities with Gaia DR2 proper motions. Some stars show unusual kinematics for their chemistries, including planar orbits, unbound orbits, and highly elliptical orbits that plunge deeply into the Galactic bulge (R peri < 0.5 kpc); also, eight stars have orbital energies and actions consistent with the Gaia-Enceladus accretion event. This paper contributes to our understanding of the complex chemo-dynamics of the metal-poor Galaxy, and increases the number of known bright metal-poor stars available for detailed nucleosynthetic studies.

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“…Metal-poor stars are highly outnumbered by metal-rich stars, and dust extinction obstructs and disturbs our view. However, thanks to efficient pre-selection methods and/or large surveys, the number of very metal-poor (VMP) inner Galaxy stars identified and studied has been increasing in recent years (Ness et al 2013;García Pérez et al 2013;Howes et al 2014Howes et al , 2015Howes et al , 2016Casey & Schlaufman 2015;Koch et al 2016;Lamb et al 2017;Lucey et al 2019Lucey et al , 2021Reggiani et al 2020;Arentsen et al 2020b).…”

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confidence: 99%

The Pristine Inner Galaxy Survey (PIGS) III: carbon-enhanced metal-poor stars in the bulge

Arentsen

Starkenburg

Aguado

et al. 2021

Monthly Notices of the Royal Astronomical Society

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The most metal-deficient stars hold important clues about the early build-up and chemical evolution of the Milky Way, and carbon-enhanced metal-poor (CEMP) stars are of special interest. However, little is known about CEMP stars in the Galactic bulge. In this paper, we use the large spectroscopic sample of metal-poor stars from the Pristine Inner Galaxy Survey (PIGS) to identify CEMP stars ($\rm {[C/Fe]} \geqslant +0.7$) in the bulge region and to derive a CEMP fraction. We identify 96 new CEMP stars in the inner Galaxy, of which 62 are very metal-poor ($\rm {[Fe/H]} < -2.0$); this is more than a ten-fold increase compared to the seven previously known bulge CEMP stars. The cumulative fraction of CEMP stars in PIGS is $42^{\, +14\, }_{\, -13} {{\ \rm per\ cent}}$ for stars with $\rm {[Fe/H]} < -3.0$, and decreases to $16^{\, +3\, }_{\, -3} {{\ \rm per\ cent}}$ for $\rm {[Fe/H]} < -2.5$ and $5.7^{\, +0.6\, }_{\, -0.5} {{\ \rm per\ cent}}$ for $\rm {[Fe/H]} < -2.0$. The PIGS inner Galaxy CEMP fraction for $\rm {[Fe/H]} < -3.0$ is consistent with the halo fraction found in the literature, but at higher metallicities the PIGS fraction is substantially lower. While this can partly be attributed to a photometric selection bias, such bias is unlikely to fully explain the low CEMP fraction at higher metallicities. Considering the typical carbon excesses and metallicity ranges for halo CEMP-s and CEMP-no stars, our results point to a possible deficiency of both CEMP-s and CEMP-no stars (especially the more metal-rich) in the inner Galaxy. The former is potentially related to a difference in the binary fraction, whereas the latter may be the result of a fast chemical enrichment in the early building blocks of the inner Galaxy.

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Using the multi-object adaptive optics demonstrator RAVEN to observe metal-poor stars in and towards the Galactic Centre

Cited by 20 publications

References 102 publications

The Pristine survey – III. Spectroscopic confirmation of an efficient search for extremely metal-poor stars

The Pristine survey – III. Spectroscopic confirmation of an efficient search for extremely metal-poor stars

The Pristine survey – IX. CFHT ESPaDOnS spectroscopic analysis of 115 bright metal-poor candidate stars

The Pristine Inner Galaxy Survey (PIGS) III: carbon-enhanced metal-poor stars in the bulge

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