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- ItemCool stars in the Galactic center as seen by APOGEE : M giants, AGB stars, and supergiant stars and candidates(Les Ulis : EDP Sciences, 2020) Schultheis, M.; Rojas-Arriagada, A.; Cunha, K.; Zoccali, M.; Chiappini, C.; Zasowski, G.; Queiroz, A.B.A.; Minniti, D.; Fritz, T.; García-Hernández, D.A.; Nitschelm, C.; Zamora, O.; Hasselquist, S.; Fernández-Trincado, J.G.; Munoz, R.R.The Galactic center region, including the nuclear disk, has until recently been largely avoided in chemical census studies because of extreme extinction and stellar crowding. Large, near-IR spectroscopic surveys, such as the Apache Point Observatory Galactic Evolution Experiment (APOGEE), allow the measurement of metallicities in the inner region of our Galaxy. Making use of the latest APOGEE data release (DR16), we are able for the first time to study cool Asymptotic Giant branch (AGB) stars and supergiants in this region. The stellar parameters of five known AGB stars and one supergiant star (VR 5-7) show that their location is well above the tip of the red giant branch. We studied metallicities of 157 M giants situated within 150 pc of the Galactic center from observations obtained by the APOGEE survey with reliable stellar parameters from the APOGEE pipeline making use of the cool star grid down to 3200 K. Distances, interstellar extinction values, and radial velocities were checked to confirm that these stars are indeed situated in the Galactic center region. We detect a clear bimodal structure in the metallicity distribution function, with a dominant metal-rich peak of [Fe/H] ∼ +0.3 dex and a metal-poor peak around {Fe/H] = −0.5 dex, which is 0.2 dex poorer than Baade’s Window. The α-elements Mg, Si, Ca, and O show a similar trend to the Galactic bulge. The metal-poor component is enhanced in the α-elements, suggesting that this population could be associated with the classical bulge and a fast formation scenario. We find a clear signature of a rotating nuclear stellar disk and a significant fraction of high-velocity stars with vgal > 300 km s−1; the metal-rich stars show a much higher rotation velocity (∼200 km s−1) with respect to the metal-poor stars (∼140 km s−1). The chemical abundances as well as the metallicity distribution function suggest that the nuclear stellar disk and the nuclear star cluster show distinct chemical signatures and might be formed differently.
- ItemExploring the S-process History in the Galactic Disk: Cerium Abundances and Gradients in Open Clusters from the OCCAM/APOGEE Sample(London : Institute of Physics Publ., 2021) Sales-Silva, J.V.; Daflon, S.; Cunha, K.; Souto, D.; Smith, V.V.; Chiappini, C.; Donor, J.; Frinchaboy, P.M.; García-Hernández, D.A.; Hayes, C.; Majewski, S. R.; Masseron, T.; Schiavon, R.P.; Weinberg, D.H.; Beaton, R.L.; Fernández-Trincado, J.G.; Jönsson, H.; Lane, R.R.; Minniti, D.; Manchado, A.; Moni Bidin, C.; Nitschelm, C.; O’Connell, J.; Villanova, S.The APOGEE Open Cluster Chemical Abundances and Mapping survey is used to probe the chemical evolution of the s-process element cerium in the Galactic disk. Cerium abundances were derived from measurements of Ce ii lines in the APOGEE spectra using the Brussels Automatic Code for Characterizing High Accuracy Spectra in 218 stars belonging to 42 open clusters. Our results indicate that, in general, for ages < 4 Gyr, younger open clusters have higher [Ce/Fe] and [Ce/α-element] ratios than older clusters. In addition, metallicity segregates open clusters in the [Ce/X]-age plane (where X can be H, Fe, or the α-elements O, Mg, Si, or Ca). These metallicity-dependent relations result in [Ce/Fe] and [Ce/α] ratios with ages that are not universal clocks. Radial gradients of [Ce/H] and [Ce/Fe] ratios in open clusters, binned by age, were derived for the first time, with d[Ce/H]/d R GC being negative, while d[Ce/Fe]/d R GC is positive. [Ce/H] and [Ce/Fe] gradients are approximately constant over time, with the [Ce/Fe] gradient becoming slightly steeper, changing by ∼+0.009 dex kpc-1 Gyr-1. Both the [Ce/H] and [Ce/Fe] gradients are shifted to lower values of [Ce/H] and [Ce/Fe] for older open clusters. The chemical pattern of Ce in open clusters across the Galactic disk is discussed within the context of s-process yields from asymptotic giant branch (AGB) stars, gigayear time delays in Ce enrichment of the interstellar medium, and the strong dependence of Ce nucleosynthesis on the metallicity of its AGB stellar sources.
- ItemThe 16th Data Release of the Sloan Digital Sky Surveys: First Release from the APOGEE-2 Southern Survey and Full Release of eBOSS Spectra(London : Institute of Physics Publ., 2020) Ahumada, Romina; Prieto, Carlos Allende; Almeida, Andrés; Anders, Friedrich; Anderson, Scott F.; Andrews, Brett H.; Anguiano, Borja; Arcodia, Riccardo; Armengaud, Eric; Aubert, Marie; Avila, Santiago; Garcia, Rafael A.; García-Hernández, D.A.; Oehmichen, Luis Alberto Garma; Ge, Junqiang; Maia, Marcio Antonio Geimba; Geisler, Doug; Gelfand, Joseph; Goddy, Julian; Gonzalez-Perez, Violeta; Grabowski, Kathleen; Avila-Reese, Vladimir; Green, Paul; Grier, Catherine J.; Guo, Hong; Guy, Julien; Harding, Paul; Hasselquist, Sten; Hawken, Adam James; Hayes, Christian R.; Hearty, Fred; Hekker, S.; Badenes, Carles; Hogg, David W.; Holtzman, Jon A.; Horta, Danny; Hou, Jiamin; Hsieh, Bau-Ching; Huber, Daniel; Hunt, Jason A. S.; Chitham, J. Ider; Imig, Julie; Jaber, Mariana; Balland, Christophe; Angel, Camilo Eduardo Jimenez; Johnson, Jennifer A.; Jones, Amy M.; Jönsson, Henrik; Jullo, Eric; Kim, Yerim; Kinemuchi, Karen; Kirkpatrick IV, Charles C.; Kite, George W.; Klaene, Mark; Barger, Kat; Kneib, Jean-Paul; Kollmeier, Juna A.; Kong, Hui; Kounkel, Marina; Krishnarao, Dhanesh; Lacerna, Ivan; Lan, Ting-Wen; Lane, Richard R.; Law, David R.; Le Goff, Jean-Marc; Barrera-Ballesteros, Jorge K.; Leung, Henry W.; Lewis, Hannah; Li, Cheng; Lian, Jianhui; Lin, Lihwai; Long, Dan; Longa-Peña, Penélope; Lundgren, Britt; Lyke, Brad W.; Ted Mackereth, J.; Basu, Sarbani; MacLeod, Chelsea L.; Majewski, Steven R.; Manchado, Arturo; Maraston, Claudia; Martini, Paul; Masseron, Thomas; Masters, Karen L.; Mathur, Savita; McDermid, Richard M.; Merloni, Andrea; Bautista, Julian; Merrifield, Michael; Mészáros, Szabolcs; Miglio, Andrea; Minniti, Dante; Minsley, Rebecca; Miyaji, Takamitsu; Mohammad, Faizan Gohar; Mosser, Benoit; Mueller, Eva-Maria; Muna, Demitri; Beaton, Rachael L.; Muñoz-Gutiérrez, Andrea; Myers, Adam D.; Nadathur, Seshadri; Nair, Preethi; Nandra, Kirpal; do Nascimento, Janaina Correa; Nevin, Rebecca Jean; Newman, Jeffrey A.; Nidever, David L.; Nitschelm, Christian; Beers, Timothy C.; Noterdaeme, Pasquier; O’Connell, Julia E.; Olmstead, Matthew D.; Oravetz, Daniel; Oravetz, Audrey; Osorio, Yeisson; Pace, Zachary J.; Padilla, Nelson; Palanque-Delabrouille, Nathalie; Palicio, Pedro A.; Benavides, B. Izamar T.; Pan, Hsi-An; Pan, Kaike; Parker, James; Paviot, Romain; Peirani, Sebastien; Ramŕez, Karla Peña; Penny, Samantha; Percival, Will J.; Perez-Fournon, Ismael; Pérez-Ràfols, Ignasi; Bender, Chad F.; Petitjean, Patrick; Pieri, Matthew M.; Pinsonneault, Marc; Poovelil, Vijith Jacob; Povick, Joshua Tyler; Prakash, Abhishek; Price-Whelan, Adrian M.; Raddick, M. Jordan; Raichoor, Anand; Ray, Amy; Bernardi, Mariangela; Rembold, Sandro Barboza; Rezaie, Mehdi; Riffel, Rogemar A.; Riffel, Rogério; Rix, Hans-Walter; Robin, Annie C.; Roman-Lopes, A.; Román-Zúñiga, Carlos; Rose, Benjamin; Ross, Ashley J.; Bershady, Matthew; Rossi, Graziano; Rowlands, Kate; Rubin, Kate H. R.; Salvato, Mara; Sánchez, Ariel G.; Sánchez-Menguiano, Laura; Sánchez-Gallego, José R.; Sayres, Conor; Schaefer, Adam; Schiavon, Ricardo P.; Beutler, Florian; Schimoia, Jaderson S.; Schlafly, Edward; Schlegel, David; Schneider, Donald P.; Schultheis, Mathias; Schwope, Axel; Seo, Hee-Jong; Serenelli, Aldo; Shafieloo, Arman; Shamsi, Shoaib Jamal; Bidin, Christian Moni; Shao, Zhengyi; Shen, Shiyin; Shetrone, Matthew; Shirley, Raphael; Aguirre, Víctor Silva; Simon, Joshua D.; Skrutskie, M.F.; Slosar, Anže; Smethurst, Rebecca; Sobeck, Jennifer; Bird, Jonathan; Sodi, Bernardo Cervantes; Souto, Diogo; Stark, David V.; Stassun, Keivan G.; Steinmetz, Matthias; Stello, Dennis; Stermer, Julianna; Storchi-Bergmann, Thaisa; Streblyanska, Alina; Stringfellow, Guy S.; Bizyaev, Dmitry; Stutz, Amelia; Suárez, Genaro; Sun, Jing; Taghizadeh-Popp, Manuchehr; Talbot, Michael S.; Tayar, Jamie; Thakar, Aniruddha R.; Theriault, Riley; Thomas, Daniel; Thomas, Zak C.; Blanc, Guillermo A.; Tinker, Jeremy; Tojeiro, Rita; Toledo, Hector Hernandez; Tremonti, Christy A.; Troup, Nicholas W.; Tuttle, Sarah; Unda-Sanzana, Eduardo; Valentini, Marica; Vargas-González, Jaime; Vargas-Magaña, Mariana; Blanton, Michael R.; Vázquez-Mata, Jose Antonio; Vivek, M.; Wake, David; Wang, Yuting; Weaver, Benjamin Alan; Weijmans, Anne-Marie; Wild, Vivienne; Wilson, John C.; Wilson, Robert F.; Wolthuis, Nathan; Boquien, Médéric; Wood-Vasey, W. M.; Yan, Renbin; Yang, Meng; Yèche, Christophe; Zamora, Olga; Zarrouk, Pauline; Zasowski, Gail; Zhang, Kai; Zhao, Cheng; Zhao, Gongbo; Borissova, Jura; Zheng, Zheng; Zheng, Zheng; Zhu, Guangtun; Zou, Hu; Bovy, Jo; Brandt, W. N.; Brinkmann, Jonathan; Brownstein, Joel R.; Bundy, Kevin; Bureau, Martin; Burgasser, Adam; Burtin, Etienne; Cano-Díaz, Mariana; Capasso, Raffaella; Cappellari, Michele; Carrera, Ricardo; Chabanier, Solène; Chaplin, William; Chapman, Michael; Cherinka, Brian; Chiappini, Cristina; Doohyun Choi, Peter; Chojnowski, S. Drew; Chung, Haeun; Clerc, Nicolas; Coffey, Damien; Comerford, Julia M.; Comparat, Johan; da Costa, Luiz; Cousinou, Marie-Claude; Covey, Kevin; Crane, Jeffrey D.; Cunha, Katia; Ilha, Gabriele da Silva; Dai, Yu Sophia; Damsted, Sanna B.; Darling, Jeremy; Davidson, James W.; Davies, Roger; Dawson, Kyle; De, Nikhil; de la Macorra, Axel; De Lee, Nathan; Queiroz, Anna Bárbara de Andrade; Deconto Machado, Alice; de la Torre, Sylvain; Dell’Agli, Flavia; du Mas des Bourboux, Hélion; Diamond-Stanic, Aleksandar M.; Dillon, Sean; Donor, John; Drory, Niv; Duckworth, Chris; Dwelly, Tom; Ebelke, Garrett; Eftekharzadeh, Sarah; Davis Eigenbrot, Arthur; Elsworth, Yvonne P.; Eracleous, Mike; Erfanianfar, Ghazaleh; Escoffier, Stephanie; Fan, Xiaohui; Farr, Emily; Fernández-Trincado, José G.; Feuillet, Diane; Finoguenov, Alexis; Fofie, Patricia; Fraser-McKelvie, Amelia; Frinchaboy, Peter M.; Fromenteau, Sebastien; Fu, Hai; Galbany, LluísThis paper documents the 16th data release (DR16) from the Sloan Digital Sky Surveys (SDSS), the fourth and penultimate from the fourth phase (SDSS-IV). This is the first release of data from the Southern Hemisphere survey of the Apache Point Observatory Galactic Evolution Experiment 2 (APOGEE-2); new data from APOGEE-2 North are also included. DR16 is also notable as the final data release for the main cosmological program of the Extended Baryon Oscillation Spectroscopic Survey (eBOSS), and all raw and reduced spectra from that project are released here. DR16 also includes all the data from the Time Domain Spectroscopic Survey and new data from the SPectroscopic IDentification of ERosita Survey programs, both of which were co-observed on eBOSS plates. DR16 has no new data from the Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) survey (or the MaNGA Stellar Library "MaStar"). We also preview future SDSS-V operations (due to start in 2020), and summarize plans for the final SDSS-IV data release (DR17).