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.

Publications

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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