Examinando por Autor "Weinberg, David H."

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    APOGEE chemical abundance patterns of the massive milky way satellites
    (IOP Publishing Ltd, 2021-12) Hasselquist, Sten; Hayes, Christian R; Lian, Jianhui; Weinberg, David H.; Zasowski, Gail; Horta, Danny; Beaton, Rachael; Feuillet, Diane K.; Garro, Elisa R.; Gallart, Carme; Smith, Verne V.; Holtzman, Jon A.; Minniti, Dante; Lacerna, Ivan; Shetrone, Matthew; Jönsson, Henrik; Cioni, Maria-Rosa L.; Fillingham, Sean P.; Cunha, Katia; O'Connell, Robert; Fernández-Trincado, José G.; Munoz, Ricardo R.; Schiavon, Ricardo; Almeida, Andres; Anguiano, Borja; Beers, Timothy C.; Bizyaev, Dmitry; Brownstein, Joel R.; Cohen, Roger E.; Frinchaboy, Peter; García-Hernández, D.A.; Geisler, Doug; Lane, Richard R.; Majewski, Steven R; Nidever, David L.; Nitschelm, Christian; Povick, Joshua; Price-Whelan, Adrian; Roman-Lopes, Alexandre; Rosado, Margarita; Sobeck, Jennifer; Stringfellow, Guy; Valenzuela, Octavio; Villanova, Sandro; Vincenzo, Fiorenzo
    The SDSS-IV Apache Point Observatory Galactic Evolution Experiment (APOGEE) survey has obtained high resolution spectra for thousands of red giant stars distributed among the massive satellite galaxies of the Milky Way (MW): the Large and Small Magellanic Clouds (LMC/SMC), the Sagittarius Dwarf Galaxy (Sgr), Fornax (Fnx), and the now fully disrupted Gaia Sausage/Enceladus (GSE) system. We present and analyze the APOGEE chemical abundance patterns of each galaxy to draw robust conclusions about their star formation histories, by quantifying the relative abundance trends of multiple elements (C, N, O, Mg, Al, Si, Ca, Fe, Ni, and Ce), as well as by fitting chemical evolution models to the [α/Fe]–[Fe/H] abundance plane for each galaxy. Results show that the chemical signatures of the starburst in the Magellanic Clouds (MCs) observed by Nidever et al. in the α-element abundances extend to C+N, Al, and Ni, with the major burst in the SMC occurring some 3–4 Gyr before the burst in the LMC. We find that Sgr and Fnx also exhibit chemical abundance patterns suggestive of secondary star formation epochs, but these events were weaker and earlier (∼5–7 Gyr ago) than those observed in the MCs. There is no chemical evidence of a second starburst in GSE, but this galaxy shows the strongest initial star formation as compared to the other four galaxies. All dwarf galaxies had greater relative contributions of AGB stars to their enrichment than the MW. Comparing and contrasting these chemical patterns highlight the importance of galaxy environment on its chemical evolution.
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    The chemical characterization of halo substructure in the Milky Way based on APOGEE
    (Oxford University Press, 2023-04) Horta, Danny; Schiavon, Ricardo P.; Mackereth, J. Ted; Weinberg, David H.; Hasselquist, Sten; Feuillet, Diane; O’Connell, Robert W.; Anguiano, Borja; Allende-Prieto, Carlos; Beaton, Rachael L.; Bizyaev, Dmitry; Cunha, Katia; Geisler, Doug; García-Hernández D.A.; Holtzman, Jon; Jönsson, Henrik; Lane, Richard R.; Majewski, Steve R.; Mészáros, Szabolcs; Minniti, Dante; Nitschelm, Christian; Shetrone, Matthew; Smith, Verne V.; Zasowski, Gail
    Galactic haloes in a Λ-CDM universe are predicted to host today a swarm of debris resulting from cannibalized dwarf galaxies. The chemodynamical information recorded in their stellar populations helps elucidate their nature, constraining the assembly history of the Galaxy. Using data from APOGEE and Gaia, we examine the chemical properties of various halo substructures, considering elements that sample various nucleosynthetic pathways. The systems studied are Heracles, Gaia-Enceladus/Sausage (GES), the Helmi stream, Sequoia, Thamnos, Aleph, LMS-1, Arjuna, I’itoi, Nyx, Icarus, and Pontus. Abundance patterns of all substructures are cross-compared in a statistically robust fashion. Our main findings include: (i) the chemical properties of most substructures studied match qualitatively those of dwarf Milky Way satellites, such as the Sagittarius dSph. Exceptions are Nyx and Aleph, which are chemically similar to disc stars, implying that these substructures were likely formed in situ; (ii) Heracles differs chemically from in situ populations such as Aurora and its inner halo counterparts in a statistically significant way. The differences suggest that the star formation rate was lower in Heracles than in the early Milky Way; (iii) the chemistry of Arjuna, LMS-1, and I’itoi is indistinguishable from that of GES, suggesting a possible common origin; (iv) all three Sequoia samples studied are qualitatively similar. However, only two of those samples present chemistry that is consistent with GES in a statistically significant fashion; (v) the abundance patterns of the Helmi stream and Thamnos are different from all other halo substructures. © 2022 The Author(s) Published by Oxford University Press on behalf of Royal Astronomical Society.
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    The SDSS-IV extended baryon oscillation spectroscopic survey: Overview and early data
    (Institute of Physics Publishing, 2016-02) Dawson, Kyle S.; Kneib, Jean-Paul; Percival, Will J.; Alam, Shadab; Albareti, Franco D.; Anderson, Scott F.; Armengaud, Eric; Aubourg, Éric; Bailey, Stephen; Bautista, Julian E.; Berlind, Andreas A.; Bershady, Matthew A.; Beutler, Florian; Bizyaev, Dmitry; Blanton, Michael R.; Blomqvist, Michael; Bolton, Adam S.; Bovy, Jo; Brandt, W.N.; Brinkmann, Jon; Brownstein, Joel R.; Burtin, Etienne; Busca, N.G.; Cai, Zheng; Chuang, Chia-Hsun; Clerc, Nicolas; Comparat, Johan; Cope, Frances; Croft, Rupert A. C.; Cruz-Gonzalez, Irene; Da Costa, Luiz N; Cousinou, Marie-Claude; Darling, Jeremy; De La MacOrra, Axel; De La Torre, Sylvain; Delubac, Timothée; Du Mas Des Bourboux, Hélion; Dwelly, Tom; Ealet, Anne; Eisenstein, Daniel J.; Eracleous, Michael; Escoffier, S.; Fan, Xiaohui; Finoguenov, Alexis; Font-Ribera, Andreu; Frinchaboy, Peter; Gaulme, Patrick; Georgakakis, Antonis; Green, Paul; Guo, Hong; Guy, Julien; Ho, Shirley; Holder, Diana; Huehnerhoff, Joe; Hutchinson, Timothy; Jing, Yipeng; Jullo, Eric; Kamble, Vikrant; Kinemuchi, Karen; Kirkby, David; Kitaura, Francisco-Shu; Klaene, Mark A.; Laher, Russ R.; Lang, Dustin; Laurent, Pierre; Goff, Jean-Marc Le; Li, Cheng; Liang, Yu; Lima, Marcos; Lin, Qiufan; Lin, Weipeng; Lin, Yen-Ting; Long, Daniel C.; Lundgren, Britt; MacDonald, Nicholas; Maia, Marcio Antonio Geimba; Malanushenko, Elena; Malanushenko, Viktor; Mariappan, Vivek; McBride, Cameron K.; McGreer, Ian D.; Ménard, Brice; Merloni, Andrea; Meza, Andres; Montero-Dorta, Antonio D.; Muna, Demitri; Myers, Adam D.; Nandra, Kirpal; Naugle, Tracy; Newman, Jeffrey A.; Noterdaeme, Pasquier; Nugent, Peter; Ogando, Ricardo; Olmstead, Matthew D.; Oravetz, Audrey; Oravetz, Daniel J.; Padmanabhan, Nikhil; Palanque-Delabrouille, Nathalie; Pan, Kaike; Parejko, John K.; Pâris, Isabelle; Peacock, John A.; Petitjean, Patrick; Pieri, Matthew M.; Pisani, Alice; Prada, Francisco; Prakash, Abhishek; Raichoor, Anand; Reid, Beth; Rich, James; Ridl, Jethro; Rodriguez-Torres, Sergio; Rosell, Aurelio Carnero; Ross, Ashley J.; Rossi, Graziano; Ruan, John; Salvato, Mara; Sayres, Conor; Schneider, Donald P.; Schlegel, David J.; Seljak, Uros; Seo, Hee-Jong; Sesar, Branimir; Shandera, Sarah; Shu, Yiping; Slosar, Anže; Sobreira, Flavia; Streblyanska, Alina; Suzuki, Nao; Taylor, Donna; Tao, Charling; Tinker, Jeremy L.; Tojeiro, Rita; Vargas-Magaña, Mariana; Wang, Yuting; Weaver, Benjamin A.; Weinberg, David H.; White, Martin; Wood-Vasey, W.M.; Yeche, Christophe; Zhai, Zhongxu; Zhao, Cheng; Zhao, Gong-Bo; Zheng, Zheng; Zhu, Guangtun Ben; Zou, Hu
    In a six-year program started in 2014 July, the Extended Baryon Oscillation Spectroscopic Survey (eBOSS) will conduct novel cosmological observations using the BOSS spectrograph at Apache Point Observatory. These observations will be conducted simultaneously with the Time Domain Spectroscopic Survey (TDSS) designed for variability studies and the Spectroscopic Identification of eROSITA Sources (SPIDERS) program designed for studies of X-ray sources. In particular, eBOSS will measure with percent-level precision the distance-redshift relation with baryon acoustic oscillations (BAO) in the clustering of matter. eBOSS will use four different tracers of the underlying matter density field to vastly expand the volume covered by BOSS and map the large-scale structures over the relatively unconstrained redshift range 0.6 < z < 2.2. Using more than 250,000 new, spectroscopically confirmed luminous red galaxies at a median redshift z = 0.72, we project that eBOSS will yield measurements of the angular diameter distance dA(z) to an accuracy of 1.2% and measurements of H(z) to 2.1% when combined with the z > 0.6 sample of BOSS galaxies. With ∼195,000 new emission line galaxy redshifts, we expect BAO measurements of dA(z) to an accuracy of 3.1% and H(z) to 4.7% at an effective redshift of z = 0.87. A sample of more than 500,000 spectroscopically confirmed quasars will provide the first BAO distance measurements over the redshift range 0.9 < z < 2.2, with expected precision of 2.8% and 4.2% on dA(z) and H(z), respectively. Finally, with 60,000 new quasars and re-observation of 60,000 BOSS quasars, we will obtain new Lyα forest measurements at redshifts z > 2.1; these new data will enhance the precision of dA(z) and H(z) at z > 2.1 by a factor of 1.44 relative to BOSS. Furthermore, eBOSS will provide improved tests of General Relativity on cosmological scales through redshift-space distortion measurements, improved tests for non Gaussianity in the primordial density field, and new constraints on the summed mass of all neutrino species. Here, we provide an overview of the cosmological goals, spectroscopic target sample, demonstration of spectral quality from early data, and projected cosmological constraints from eBOSS.