Ruprecht-Karls-Universität Heidelberg
Subproject A4: The Chemical Abundance Patterns of the Most Metal-Poor Stars

Subproject A4: The Chemical Abundance Patterns of the Most Metal-Poor Stars

Norbert Christlieb (LSW), Hans-Günter Ludwig (LSW)

Extremely metal-deficient stars hold clues to understanding the early star formation in the Universe shortly after the first stars formed and about the subsequent chemical evolution. During the first funding period, new methods to select very metal-poor candidates were developed. Spectroscopic follow-up showed that this improves the selection efficiency by a factor of two. With the enlarged samples, it could be shown that the transition from Population III and II.5 star formation to “normal” Population II low-mass star formation was smooth, contrary to earlier claims. As the Chinese LAMOST and the Australian Skymapper projects were delayed, which had been intended to be the main data resources to be used in A4, other surveys were used instead, including a new Large Programme at ESO called “TOPoS” initiated in A4. Moreover, considerable progress was made in developing advanced 3-D model atmospheres for low metallicities, an essential precondition for reliable abundance analysis.

In the second funding period, we want to continue our searches for the most metal-poor stars in the Galactic halo by means of wide-angle spectroscopic sky surveys (in particular the Chinese LAMOST survey and the Sloan Digital Sky Survey (SDSS)). Chemical abundance patterns of metal-poor candidates shall be determined based on high-resolution optical and near-infrared spectroscopy and 3-D hydrodynamical stellar model atmospheres. For the latter, we will develop and implement an improved radiative transfer scheme as well as a non-LTE molecular equilibrium code. This will ensure accurate determinations of abundances derived from diatomic molecules, such as CH, CN, NH, and C2, which are among the few features that can still be detected in the spectra of the most metal-poor stars.


Thygesen, Anders O.; Kirby, Evan N.; Gallagher, Andrew J.; Ludwig, Hans-G.; Caffau, Elisabetta; Bonifacio, Piercarlo; Sbordone, Luca
07/2017 ApJ 843, 144

Cerniauskas, A.; Kucinskas, A.; Klevas, J.; Prakapavicius, D.; Korotin, S.; Bonifacio, P.; Ludwig, H.-G.; Caffau, E.; Steffen, M.
07/2017 A&A 604, A35

Prakapavicius, D.; Kucinskas, A.; Dobrovolskas, V.; Klevas, J.; Steffen, M.; Bonifacio, P.; Ludwig, H.-G.; Spite, M.
03/2017 A&A 599, A128

Gallagher, A. J.; Caffau, E.; Bonifacio, P.; Ludwig, H.-G.; Steffen, M.; Homeier, D.; Plez, B.
02/2017 A&A 598, L10

Zhang, Z. H.; Pinfield, D. J.; Gálvez-Ortiz, M. C.; Burningham, B.; Lodieu, N.; Marocco, F.; Burgasser, A. J.; Day-Jones, A. C.; Allard, F.; Jones, H. R. A.; Homeier, D.; Gomes, J.; Smart, R. L.
01/2017 MNRAS 464, 3040

Rajpurohit, A. S.; Reylé, C.; Allard, F.; Homeier, D.; Bayo, A.; Mousis, O.; Rajpurohit, S.; Fernández-Trincado, J. G.
11/2016 A&A 596, A33

Caffau, E.; Bonifacio, P.; Spite, M.; Spite, F.; Monaco, L.; Sbordone, L.; François, P.; Gallagher, A. J.; Plez, B.; Zaggia, S.; Ludwig, H.-G.; Cayrel, R.; Koch, A.; Steffen, M.; Salvadori, S.; Klessen, R.; Glover, S.; Christlieb, N.
10/2016 A&A 595, L6

Christlieb, N.
09/2016 AN 337, 931

Ludwig, H.-G.; Steffen, M.
09/2016 AN 337, 844

Gallagher, A. J.; Caffau, E.; Bonifacio, P.; Ludwig, H.-G.; Steffen, M.; Spite, M.
09/2016 A&A 593, A48

Hansen, C. J.; Rich, R. M.; Koch, A.; Xu, S.; Kunder, A.; Ludwig, H.-G.
05/2016 A&A 590, A39

Thygesen, A. O.; Sbordone, L.; Ludwig, H.-G.; Ventura, P.; Yong, D.; Collet, R.; Christlieb, N.; Melendez, J.; Zaggia, S.
04/2016 A&A 588, A66

Jorissen, A.; Hansen, T.; Van Eck, S.; Andersen, J.; Nordström, B.; Siess, L.; Torres, G.; Masseron, T.; Van Winckel, H.
02/2016 A&A 586, A159

Klevas, J.; Kucinskas, A.; Steffen, M.; Caffau, E.; Ludwig, H.-G.
02/2016 A&A 586, A156

Manjavacas, E.; Goldman, B.; Alcalá, J. M.; Zapatero-Osorio, M. R.; Béjar, V. J. S.; Homeier, D.; Bonnefoy, M.; Smart, R. L.; Henning, T.; Allard, F.
01/2016 MNRAS 455, 1341

Sonoi, T.; Samadi, R.; Belkacem, K.; Ludwig, H.-G.; Caffau, E.; Mosser, B.
11/2015 A&A 583, A112

Hansen, T. T.; Andersen, J.; Nordström, B.; Beers, T. C.; Yoon, J.; Buchhave, L. A.
11/2015 A&A 583, A49

Steffen, M.; Prakapavicius, D.; Caffau, E.; Ludwig, H.-G.; Bonifacio, P.; Cayrel, R.; Kucinskas, A.; Livingston, W. C.
11/2015 A&A 583, A57

Placco, Vinicius M.; Beers, Timothy C.; Ivans, Inese I.; Filler, Dan; Imig, Julie A.; Roederer, Ian U.; Abate, Carlo; Hansen, Terese; Cowan, John J.; Frebel, Anna; Lawler, James E.; Schatz, Hendrik; Sneden, Christopher; Sobeck, Jennifer S.; Aoki, Wako; Smith, Verne V.; Bolte, Michael
10/2015 ApJ 812, 109

Tremblay, P.-E.; Fontaine, G.; Freytag, B.; Steiner, O.; Ludwig, H.-G.; Steffen, M.; Wedemeyer, S.; Brassard, P.
10/2015 ApJ 812, 19

Li, Haining; Aoki, Wako; Zhao, Gang; Honda, Satoshi; Christlieb, Norbert; Suda, Takuma
10/2015 PASJ 67, 84

Li, Hai-Ning; Aoki, Wako; Honda, Satoshi; Zhao, Gang; Christlieb, Norbert; Suda, Takuma
08/2015 RAA 15, 1264

Tremblay, P.-E.; Gianninas, A.; Kilic, M.; Ludwig, H.-G.; Steffen, M.; Freytag, B.; Hermes, J. J.
08/2015 ApJ 809, 148

Cordero, M. J.; Hansen, C. J.; Johnson, C. I.; Pilachowski, C. A.
07/2015 ApJ 808, L10

Kunder, Andrea; Rich, R. M.; Hawkins, K.; Poleski, R.; Storm, J.; Johnson, C. I.; Shen, J.; Li, Z.-Y.; Cordero, M. J.; Nataf, D. M.; Bono, G.; Walker, A. R.; Koch, A.; De Propris, R.; Udalski, A.; Szymanski, M. K.; Soszynski, I.; Pietrzynski, G.; Ulaczyk, K.; Wyrzykowski, L.; Pietrukowicz, P.; Skowron, J.; Kozlowski, S.; Mróz, P.
07/2015 ApJ 808, L12

Caffau, E.; Ludwig, H.-G.; Steffen, M.; Livingston, W.; Bonifacio, P.; Malherbe, J.-M.; Doerr, H.-P.; Schmidt, W.
07/2015 A&A 579, A88

Hansen, T.; Hansen, C. J.; Christlieb, N.; Beers, T. C.; Yong, D.; Bessell, M. S.; Frebel, A.; García Pérez, A. E.; Placco, V. M.; Norris, J. E.; Asplund, M.
07/2015 ApJ 807, 173

Bonifacio, P.; Caffau, E.; Spite, M.; Limongi, M.; Chieffi, A.; Klessen, R. S.; François, P.; Molaro, P.; Ludwig, H.-G.; Zaggia, S.; Spite, F.; Plez, B.; Cayrel, R.; Christlieb, N.; Clark, P. C.; Glover, S. C. O.; Hammer, F.; Koch, A.; Monaco, L.; Sbordone, L.; Steffen, M.
07/2015 A&A 579, A28

Dobrovolskas, V.; Kucinskas, A.; Bonifacio, P.; Caffau, E.; Ludwig, H.-G.; Steffen, M.; Spite, M.
04/2015 A&A 576, A128

Tremblay, P.-E.; Ludwig, H.-G.; Freytag, B.; Fontaine, G.; Steffen, M.; Brassard, P.
02/2015 ApJ 799, 142

Cordero, M. J.; Pilachowski, C. A.; Johnson, C. I.; Vesperini, E.
02/2015 ApJ 800, 3

Li, Hai-Ning; Zhao, Gang; Christlieb, Norbert; Wang, Liang; Wang, Wei; Zhang, Yong; Hou, Yonghui; Yuan, Hailong
01/2015 ApJ 798, 110

Puspitarini, L.; Lallement, R.; Babusiaux, C.; Chen, H.-C.; Bonifacio, P.; Sbordone, L.; Caffau, E.; Duffau, S.; Hill, V.; Monreal-Ibero, A.; Royer, F.; Arenou, F.; Peralta, R.; Drew, J. E.; Bonito, R.; Lopez-Santiago, J.; Alfaro, E. J.; Bensby, T.; Bragaglia, A.; Flaccomio, E.; Lanzafame, A. C.; Pancino, E.; Recio-Blanco, A.; Smiljanic, R.; Costado, M. T.; Lardo, C.; de Laverny, P.; Zwitter, T.
01/2015 A&A 573, A35

Editor: T. Lisker
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