The ESO UVES advanced data products quasar sample – III. Evidence of bimodality in the [N/α] distribution

Zafar, T.; Centurión, M.; Péroux, Céline; Molaro, P.; D’Odorico, V.; Vladilo, G.; Popping, Attila

doi:10.1093/mnras/stu1473

Cited by 30 publications

(36 citation statements)

References 86 publications

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“…We also note that the [N/O] ratio is well-determined in this DLA, since both N I and O I trace the H I bearing gas due to charge transfer reactions (Field & Steigman 1971;Steigman et al 1971). Our value of [N/O] is consistent with, or slightly lower than, the primary N/ O plateau (Izotov & Thuan 1999;Centurión et al 2003;van Zee & Haynes 2006;Petitjean et al 2008;Pettini et al 2008;Pettini & Cooke 2012b;Zafar et al 2014).…”

Section: Analysis Methodssupporting

confidence: 79%

THE PRIMORDIAL DEUTERIUM ABUNDANCE OF THE MOST METAL-POOR DAMPED Lyα SYSTEM^∗

Cooke

Pettini

Nollett

et al. 2016

ApJ

140

161

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Section: Analysis Methodssupporting

confidence: 79%

THE PRIMORDIAL DEUTERIUM ABUNDANCE OF THE MOST METAL-POOR DAMPED Lyα SYSTEM^∗

Cooke

Pettini

Nollett

et al. 2016

ApJ

140

161

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“…This suggests that primordial gas clouds could exist and trigger star formation down to at least z = 2.3. A similar conclusion has been reached in a completely independent way by considering the low N/O ratios found in DLAs (Molaro et al 2004;Zafar et al 2014). We cannot exclude that the stars that enriched these DLAs actually formed 13 Gyr ago, and that the DLA galaxy has not undergone any star formation since.…”

Section: Carbon Enhanced Damped Lyα Galaxiessupporting

confidence: 75%

TOPoS

Bonifacio

Caffau

Spite

et al. 2015

A&A

170

232

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Context. In the course of the Turn Off Primordial Stars (TOPoS) survey, aimed at discovering the lowest metallicity stars, we have found several carbon-enhanced metal-poor (CEMP) stars. These stars are very common among the stars of extremely low metallicity and provide important clues to the star formation processes. We here present our analysis of six CEMP stars. Aims. We want to provide the most complete chemical inventory for these six stars in order to constrain the nucleosynthesis processes responsible for the abundance patterns. Methods. We analyse both X-Shooter and UVES spectra acquired at the VLT. We used a traditional abundance analysis based on OSMARCS 1D local thermodynamic equilibrium (LTE) model atmospheres and the turbospectrum line formation code. were not able to detect any iron lines, yet we could place a robust (3σ) upper limit of [Fe/H] < −5.0 and measure the Ca abundance, with [Ca/H] = −5.0, and carbon, A(C) = 6.90, suggesting that this star could be even more metal-poor than SDSS J1742+2531. This makes these two stars the seventh and eighth stars known so far with [Fe/H] < −4.5, usually termed ultra-iron-poor (UIP) stars. No lithium is detected in the spectrum of SDSS J1742+2531 or SDSS J1035+0641, which implies a robust upper limit of A(Li) < 1.8 for both stars. Conclusions. Our measured carbon abundances confirm the bimodal distribution of carbon in CEMP stars, identifying a high-carbon band and a low-carbon band. We propose an interpretation of this bimodality according to which the stars on the high-carbon band are the result of mass transfer from an AGB companion, while the stars on the low-carbon band are genuine fossil records of a gas Article published by EDP Sciences A28, page 1 of 20 A&A 579, A28 (2015) cloud that has also been enriched by a faint supernova (SN) providing carbon and the lighter elements. The abundance pattern of the UIP stars shows a large star-to-star scatter in the [X/Ca] ratios for all elements up to aluminium (up to 1 dex), but this scatter drops for heavier elements and is at most of the order of a factor of two. We propose that this can be explained if these stars are formed from gas that has been chemically enriched by several SNe, that produce the roughly constant [X/Ca] ratios for the heavier elements, and in some cases the gas has also been polluted by the ejecta of a faint SN that contributes the lighter elements in variable amounts. The absence of lithium in four of the five known unevolved UIP stars can be explained by a dominant role of fragmentation in the formation of these stars. This would result either in a destruction of lithium in the pre-main-sequence phase, through rotational mixing or to a lack of late accretion from a reservoir of fresh gas. The phenomenon should have varying degrees of efficiency.

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“…For example, van Zee & Haynes (2006) reported a large scatter in N/O at low metallicities, which had been anticipated by Garnett (1990). The scatter may be due to the time delay between the release of oxygen from massive stars and primary nitrogen from low-and intermediate-mass stars as proposed by Vila Costas & Edmunds (1993) (see also Pettini et al 2008), or perhaps an infall of metal-poor gas in some galaxies (Amorín et al 2012), but a full interpretation is still far from being established Zafar et al 2014). At higher metallicities, the effects of secondary As can be seen from Fig.…”

Section: N/o Vs Oxygen Abundancementioning

confidence: 80%

Uncovering blue diffuse dwarf galaxies

James

Koposov

Stark

et al. 2015

Monthly Notices of the Royal Astronomical Society

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Extremely metal poor (XMP) galaxies are known to be very rare, despite the large numbers of low-mass galaxies predicted by the local galaxy luminosity function. This paper presents a sub-sample of galaxies that were selected via a morphology-based search on SDSS images with the aim of finding these elusive XMP galaxies. By using the recently discovered extremely metal-poor galaxy, Leo P, as a guide, we obtained a collection of faint, blue systems, each with isolated H ii regions embedded in a diffuse continuum, that have remained optically undetected until now. Here we show the first results from optical spectroscopic follow-up observations of 12 of ∼100 of these blue, diffuse dwarf (BDD) galaxies yielded by our search algorithm. Oxygen abundances were obtained via the direct method for eight galaxies, and found to be in the range 7.45 < 12 + log (O/H) < 8.0, with two galaxies being classified as XMPs. All BDDs were found to currently have a young star-forming population (< 10 Myr) and relatively high ionisation parameters of their H ii regions. Despite their low luminosities (−11 M B −18) and low surface brightnesses (∼ 23-25 mag arcsec −2 ), the galaxies were found to be actively star-forming, with current star-formation rates between 0.0003 and 0.078 M yr −1 . From our current subsample, BDD galaxies appear to be a population of non-quiescent dwarf irregular (dIrr) galaxies, or the diffuse counterparts to blue compact galaxies (BCDs) and as such may bridge the gap between these two populations. Our search algorithm demonstrates that morphology-based searches are successful in uncovering more diffuse metal-poor star-forming galaxies, which traditional emission-line based searches overlook.

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The ESO UVES advanced data products quasar sample – III. Evidence of bimodality in the [N/α] distribution

Cited by 30 publications

References 86 publications

THE PRIMORDIAL DEUTERIUM ABUNDANCE OF THE MOST METAL-POOR DAMPED Lyα SYSTEM^∗

THE PRIMORDIAL DEUTERIUM ABUNDANCE OF THE MOST METAL-POOR DAMPED Lyα SYSTEM^∗

TOPoS

Uncovering blue diffuse dwarf galaxies

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The ESO UVES advanced data products quasar sample – III. Evidence of bimodality in the [N/α] distribution

Cited by 30 publications

References 86 publications

THE PRIMORDIAL DEUTERIUM ABUNDANCE OF THE MOST METAL-POOR DAMPED Lyα SYSTEM∗

THE PRIMORDIAL DEUTERIUM ABUNDANCE OF THE MOST METAL-POOR DAMPED Lyα SYSTEM∗

TOPoS

Uncovering blue diffuse dwarf galaxies

Contact Info

Product

Resources

About

THE PRIMORDIAL DEUTERIUM ABUNDANCE OF THE MOST METAL-POOR DAMPED Lyα SYSTEM^∗

THE PRIMORDIAL DEUTERIUM ABUNDANCE OF THE MOST METAL-POOR DAMPED Lyα SYSTEM^∗