Carbon and nitrogen abundances of individual stars in the Sculptor dwarf spheroidal galaxy

Lardo, C.; Battaglia, G.; Pancino, E.; Romano, D.; Boer, T. J. L. de; Starkenburg, Else; Tolstoy, Eline; Irwin, M. J.; Jablonka, P.; Tosi, M.

doi:10.1051/0004-6361/201527391

Cited by 27 publications

(37 citation statements)

References 93 publications

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“…Here, the blue and red histograms represent the findings from methods I and III, respectively. For comparison, we indicate the fractions for bound cluster stars as reported by Carretta et al (2009, solid dence for CN-bimodalities amongst the dSph field star populations is sparse (e.g., Smith & Dopita 1983;Lardo et al 2016a;Norris et al 2017;Salgado et al 2019). However, several GCs in the MW have been associated with dwarf-accretion events.…”

Section: The Fraction Of Chemically Altered Stars Amongst Bona-fide Ementioning

confidence: 73%

Purveyors of fine halos

Hanke

Koch

Prudil

et al. 2020

A&A

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A long-lasting open question in the field of Galactic archeology refers to the size of the contribution from former globular cluster (GC) stars to the formation of the stellar halo of the Milky Way. We contribute to answering this important question by establishing observational links between the present-day halo field star population and GCs. To this end, we combined astrometric information such as space motions and parallaxes from the second data release of the Gaia mission (Gaia DR2) with spectroscopic radial velocities and metallicities ([Fe/H]) from the Sloan Digital Sky Survey (SDSS-IV, DR14) to end up with a seven-dimensional chemodynamical information space for more than 3 · 10 5 stars. Moreover, from our previous study, we incorporated the sample of halo giant stars with a distinct chemical signature (strong CN bandheads) that resembles the light-elements anomaly otherwise only seen in the second generation of globular cluster stellar populations. Using three different tagging techniques -among which is the exploration of conservative integrals of motion -we are able to establish unique associations between 151 extratidal stars in the neighborhood of eight GCs, which coincide with earlier findings of stellar envelopes beyond the tidal radius and even beyond (out to several tens of tidal radii). In addition, we trace the possible origin of about 62% of the sample of CN-strong giants to their potential host clusters. We find a connection between several of the involved GCs and the Gaia-Enceladus and Sequoia merger events. By establishing kinematic and chemical connections between 17 CN-strong stars and their surrounding fields, we identify co-moving groups of stars at the same [Fe/H] with a possible cluster origin. Some of these associations contain RR Lyrae variables, which allows meaningful distance inferences to be made. From these, we find strong evidence that four CN-strong stars and their associates are connected to the Sagittarius stream whilst their tightly confined [Fe/H] may hint to a birth site in M 54, the massive cluster in Sagittarius' core remnant. Finally, by employing the counts of CN-strong and bona-fide CN-normal giants from our novel sample, we provide tentative estimates for the fraction of first-generation cluster stars among all stars lost to the halo. In the immediate cluster vicinity, this value amounts to 50.0 ± 16.7% while the associations in the halo field rather imply 80.2 +4.9 −5.2 %. We speculate that -if proven real by spectroscopic follow-up -the disparity between these numbers could indicate a major contribution of low-mass clusters to the overall number of stars escaped to the halo or could alternatively suggest strong mass loss from the first generation during early cluster dissolution.

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Section: The Fraction Of Chemically Altered Stars Amongst Bona-fide Ementioning

confidence: 73%

Purveyors of fine halos

Hanke

Koch

Prudil

et al. 2020

A&A

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“…If such stars exist, it would favour a picture in which massive GCs did form, but were subsequently destroyed. So far, no significant populations of field stars with GC-like abundance patterns have been found in dwarf galaxies (Lemasle et al 2014;Lardo et al 2016;Suda et al 2017), but the samples may still be too small to rule out an enriched fraction of a few percent, similar to that seen in the Milky Way halo (Martell et al 2011(Martell et al , 2016. …”

Section: Metallicitiesmentioning

confidence: 96%

Detailed abundance analysis of globular clusters in the Local Group

Larsen

Brodie

Wasserman

et al. 2018

A&A

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Context. Globular clusters (GCs) are emerging as powerful tracers of the chemical composition of extragalactic stellar populations. Aims. We present new abundance measurements for eleven GCs in the Local Group galaxies NGC 147, NGC 6822, and Messier 33. These are combined with previously published observations of four GCs in the Fornax and WLM galaxies. Methods. The abundances were determined from analysis of integrated-light spectra, obtained with the HIRES spectrograph on the Keck I telescope and with UVES on the VLT. We used our analysis technique that has been developed for this purpose and tested on Milky Way GCs. Results. We find that the clusters with [Fe/H] < −1.5 are all α-enhanced at about the same level as Milky Way GCs. Their Na abundances are also generally enhanced relative to Milky Way halo stars, suggesting that these extragalactic GCs resemble their Milky Way counterparts in containing significant fractions of Na-rich stars. For [Fe/H] > −1.5, the GCs in M33 are also α-enhanced, while the GCs that belong to dwarfs (NGC 6822 SC7 and Fornax 4) have closer to Solar-scaled α-element abundances. The abundance patterns in SC7 are remarkably similar to those in the Galactic GC Ruprecht 106, including significantly sub-solar [Na/Fe] and [Ni/Fe] ratios. In NGC 147, the GCs with [Fe/H] < −2.0 account for about 6% of the total luminosity of stars in the same metallicity range, a lower fraction than those previously found in the Fornax and WLM galaxies, but substantially higher than in the Milky Way halo. Conclusions. At low metallicities, the abundance patterns suggest that GCs in the Milky Way, dwarf galaxies, and M33 experienced similar enrichment histories and/or processes. At higher metallicities, the lower levels of α-enhancement in the GCs found in dwarf galaxies resemble the abundance patterns observed in field stars in nearby dwarfs. Constraining the presence of multiple populations in the GCs is complicated by the lack of information about detailed abundances in field stars of the corresponding metallicities. We suggest that correlations such as [Na/Fe] vs. [Ni/Fe] may prove useful for this purpose if an accuracy of ∼ 0.1 dex or better can be reached for the integrated-light measurements.

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“…Prior to this study, only four CEMP stars had been identified in Sculptor (Skúladóttir et al 2015b;Lardo et al 2016;Salgado et al 2016). Of those, only one was a CEMP-no star, resulting in an apparent disagreement between the CEMP fraction of Sculptor and the CEMP fraction of the Milky Way halo (∼42%).…”

Section: Discussionmentioning

confidence: 99%

“…Given Kirby et al (2015), 94 medium-resolution measurements from Lardo et al (2016), and 28 stars with high-resolution measurements Geisler et al 2005;Frebel et al 2010a;Tafelmeyer et al 2010;Kirby & Cohen 2012;Starkenburg et al 2013;Jablonka et al 2015;Simon et al 2015;Skúladóttir et al 2015b). Thirteen of these stars have [Fe/H] < −2.8, one of which is potentially a CEMP-no star (Scl 11_1_4296 in Simon et al 2015).…”

Section: Discussionmentioning

confidence: 99%

“…Only one CEMP-no star has been previously detected in Sculptor (Skúladóttir et al 2015b), with [Fe/H] = −2.03 and [C/Fe] ∼ 0.51, and only three CEMP-s stars are known in the galaxy out of spectroscopic samples of hundreds of stars (Lardo et al 2016;Salgado et al 2016). Under the assumptions that the ancient analogs of today's dwarf galaxies formed the Milky Way halo, one would expect that dwarf galaxies would show carbon enhancement in their oldest stellar population as well.…”

Section: Introductionmentioning

confidence: 99%

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Detection of a Population of Carbon-enhanced Metal-poor Stars in the Sculptor Dwarf Spheroidal Galaxy^∗

Chiti

Simon

Frebel

et al. 2018

ApJ

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The study of the chemical abundances of metal-poor stars in dwarf galaxies provides a venue to constrain paradigms of chemical enrichment and galaxy formation. Here we present metallicity and carbon abundance measurements of 100 stars in Sculptor from medium-resolution (R ∼ 2000) spectra taken with the Magellan/ Michigan Fiber System mounted on the Magellan-Clay 6.5 m telescope at Las Campanas Observatory. We identify 24 extremely metal-poor star candidates ([Fe/H] < −3.0) and 21 carbon-enhanced metal-poor (CEMP) star candidates. Eight carbon-enhanced stars are classified with at least 2σ confidence, and five are confirmed as such with follow-up R ∼ 6000 observations using the Magellan Echellette Spectrograph on the Magellan-Baade 6.5 m telescope. We measure a CEMP fraction of 36% for stars below [Fe/H] = −3.0, indicating that the prevalence of carbon-enhanced stars in Sculptor is similar to that of the halo (∼43%) after excluding likely CEMP-s and CEMPr/s stars from our sample. However, we do not detect that any CEMP stars are strongly enhanced in carbon ([C/Fe] > 1.0). The existence of a large number of CEMP stars both in the halo and in Sculptor suggests that some halo CEMP stars may have originated from accreted early analogs of dwarf galaxies.

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Carbon and nitrogen abundances of individual stars in the Sculptor dwarf spheroidal galaxy

Cited by 27 publications

References 93 publications

Purveyors of fine halos

Purveyors of fine halos

Detailed abundance analysis of globular clusters in the Local Group

Detection of a Population of Carbon-enhanced Metal-poor Stars in the Sculptor Dwarf Spheroidal Galaxy^∗

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Carbon and nitrogen abundances of individual stars in the Sculptor dwarf spheroidal galaxy

Cited by 27 publications

References 93 publications

Purveyors of fine halos

Purveyors of fine halos

Detailed abundance analysis of globular clusters in the Local Group

Detection of a Population of Carbon-enhanced Metal-poor Stars in the Sculptor Dwarf Spheroidal Galaxy∗

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Product

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About

Detection of a Population of Carbon-enhanced Metal-poor Stars in the Sculptor Dwarf Spheroidal Galaxy^∗