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http://hdl.handle.net/20.500.12386/34409
Titolo: | High-resolution spectroscopic follow-up of the most metal-poor candidates from SkyMapper DR1.1 | Autori: | Yong, D. Da Costa, G. S. Bessell, M. S. Chiti, A. Frebel, A. Gao, X. Lind, K. Mackey, A. D. MARINO, Anna Murphy, S. J. Nordlander, T. Asplund, M. Casey, A. R. Kobayashi, C. Norris, J. E. Schmidt, B. P. |
Data pubblicazione: | 2021 | Rivista: | MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY | Numero: | 507 | Fascicolo: | 3 | Da pagina:: | 4102 | Abstract: | We present chemical abundances for 21 elements (from Li to Eu) in 150 metal-poor Galactic stars spanning -4.1 < [Fe/H] < -2.1. The targets were selected from the SkyMapper survey and include 90 objects with [Fe/H] ≤ -3 of which some 15 have [Fe/H] ≤ -3.5. When combining the sample with our previous studies, we find that the metallicity distribution function has a power-law slope of Δ(log N)/Δ[Fe/H] = 1.51 ± 0.01 dex per dex over the range -4 ≤ [Fe/H] ≤ -3. With only seven carbon-enhanced metal-poor stars in the sample, we again find that the selection of metal-poor stars based on SkyMapper filters is biased against highly carbon-rich stars for [Fe/H] > -3.5. Of the 20 objects for which we could measure nitrogen, 11 are nitrogen-enhanced metal-poor (NEMP) stars. Within our sample, the high NEMP fraction (55 per cent ± 21 per cent) is compatible with the upper range of predicted values (between 12 per cent and 35 per cent). The chemical abundance ratios [X/Fe] versus [Fe/H] exhibit similar trends to previous studies of metal-poor stars and Galactic chemical evolution models. We report the discovery of nine new r-I stars, four new r-II stars, one of which is the most metal-poor known, nine low-α stars with [α/Fe] ≤ 0.15 as well as one unusual star with [Zn/Fe] = +1.4 and [Sr/Fe] = +1.2 but with normal [Ba/Fe]. Finally, we combine our sample with literature data to provide the most extensive view of the early chemical enrichment of the Milky Way Galaxy. | URI: | http://hdl.handle.net/20.500.12386/34409 | URL: | https://academic.oup.com/mnras/article/507/3/4102/6321844 https://api.elsevier.com/content/abstract/scopus_id/85117198172 |
ISSN: | 0035-8711 | DOI: | 10.1093/mnras/stab2001 | Bibcode ADS: | 2021MNRAS.507.4102Y | Fulltext: | open |
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