Browsing by Author "Fernandez-Trincado, Jose G."

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    Exploring the Stellar Age Distribution of the Milky Way Bulge Using APOGEE
    (2020) Hasselquist, Sten; Zasowski, Gail; Feuillet, Diane K.; Schultheis, Mathias; Nataf, David M.; Anguiano, Borja; Beaton, Rachael L.; Beers, Timothy C.; Cohen, Roger E.; Cunha, Katia; Fernandez-Trincado, Jose G.; Garcia-Hernandez, D. A.; Geisler, Doug; Holtzman, Jon A.; Johnson, Jennifer; Lane, Richard R.; Majewski, Steven R.; Bidin, Christian Moni; Nitschelm, Christian; Roman-Lopes, Alexandre; Schiavon, Ricardo; Smith, Verne V.; Sobeck, Jennifer
    We present stellar age distributions of the Milky Way bulge region using ages for similar to 6000 high-luminosity (log (g), metal-rich ([Fe/H] >= -0.5) bulge stars observed by the Apache Point Observatory Galactic Evolution Experiment. Ages are derived using The Cannon label-transfer method, trained on a sample of nearby luminous giants with precise parallaxes for which we obtain ages using a Bayesian isochrone-matching technique. We find that the metal-rich bulge is predominantly composed of old stars (>8 Gyr). We find evidence that the planar region of the bulge (vertical bar Z(GC)vertical bar <= 0.25 kpc) is enriched in metallicity, Z, at a faster rate (dZ/dt similar to 0.0034 Gyr(-1)) than regions farther from the plane (dZ/dt similar to 0.0013 Gyr(-1) at vertical bar Z(GC)vertical bar > 1.00 kpc). We identify a nonnegligible fraction of younger stars (age similar to 2-5 Gyr) at metallicities of +0.2 < [Fe/H] < +0.4. These stars are preferentially found in the plane (vertical bar Z(GC)vertical bar <= 0.25 kpc) and at R-cy approximate to 2-3 kpc, with kinematics that are more consistent with rotation than are the kinematics of older stars at the same metallicities. We do not measure a significant age difference between stars found inside and outside the bar. These findings show that the bulge experienced an initial starburst that was more intense close to the plane than far from the plane. Then, star formation continued at supersolar metallicities in a thin disk at 2 kpc less than or similar to R-cy less than or similar to 3 kpc until similar to 2 Gyr ago.
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    Final Targeting Strategy for the SDSS-IV APOGEE-2S Survey
    (2021) Santana, Felipe A.; Beaton, Rachael L.; Covey, Kevin R.; O'Connell, Julia E.; Longa-Pena, Penelope; Cohen, Roger; Fernandez-Trincado, Jose G.; Hayes, Christian R.; Zasowski, Gail; Sobeck, Jennifer S.; Majewski, Steven R.; Chojnowski, S. D.; De Lee, Nathan; Oelkers, Ryan J.; Stringfellow, Guy S.; Almeida, Andres; Anguiano, Borja; Donor, John; Frinchaboy, Peter M.; Hasselquist, Sten; Johnson, Jennifer A.; Kollmeier, Juna A.; Nidever, David L.; Price-Whelan, Adrian M.; Rojas-Arriagada, Alvaro; Schultheis, Mathias; Shetrone, Matthew; Simon, Joshua D.; Aerts, Conny; Borissova, Jura; Drout, Maria R.; Geisler, Doug; Law, C. Y.; Medina, Nicolas; Minniti, Dante; Monachesi, Antonela; Munoz, Ricardo R.; Poleski, Radoslaw; Roman-Lopes, Alexandre; Schlaufman, Kevin C.; Stutz, Amelia M.; Teske, Johanna; Tkachenko, Andrew; Van Saders, Jennifer L.; Weinberger, Alycia J.; Zoccali, Manuela
    APOGEE is a high-resolution (R similar to 22,000), near-infrared, multi-epoch, spectroscopic survey of the Milky Way. The second generation of the APOGEE project, APOGEE-2, includes an expansion of the survey to the Southern Hemisphere called APOGEE-2S. This expansion enabled APOGEE to perform a fully panoramic mapping of all of the main regions of the Milky Way; in particular, by operating in the H band, APOGEE is uniquely able to probe the dust-hidden inner regions of the Milky Way that are best accessed from the Southern Hemisphere. In this paper we present the targeting strategy of APOGEE-2S, with special attention to documenting modifications to the original, previously published plan. The motivation for these changes is explained as well as an assessment of their effectiveness in achieving their intended scientific objective. In anticipation of this being the last paper detailing APOGEE targeting, we present an accounting of all such information complete through the end of the APOGEE-2S project; this includes several main survey programs dedicated to exploration of major stellar populations and regions of the Milky Way, as well as a full list of programs contributing to the APOGEE database through allocations of observing time by the Chilean National Time Allocation Committee and the Carnegie Institution for Science. This work was presented along with a companion article, Beaton et al. (2021), presenting the final target selection strategy adopted for APOGEE-2 in the Northern Hemisphere.
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    The Eighteenth Data Release of the Sloan Digital Sky Surveys: Targeting and First Spectra from SDSS-V
    (2023) Almeida, Andres; Anderson, Scott F.; Argudo-Fernandez, Maria; Badenes, Carles; Barger, Kat; Barrera-Ballesteros, Jorge K.; Bender, Chad F.; Benitez, Erika; Besser, Felipe; Bird, Jonathan C.; Bizyaev, Dmitry; Blanton, Michael R.; Bochanski, John; Bovy, Jo; Brandt, William Nielsen; Brownstein, Joel R.; Buchner, Johannes; Bulbul, Esra; Burchett, Joseph N.; Diaz, Mariana Cano; Carlberg, Joleen K.; Casey, Andrew R.; Chandra, Vedant; Cherinka, Brian; Chiappini, Cristina; Coker, Abigail A.; Comparat, Johan; Conroy, Charlie; Contardo, Gabriella; Cortes, Arlin; Covey, Kevin; Crane, Jeffrey D.; Cunha, Katia; Dabbieri, Collin; Davidson, James W.; Davis, Megan C.; de Andrade Queiroz, Anna Barbara; De Lee, Nathan; Mendez Delgado, Jose Eduardo; Demasi, Sebastian; Di Mille, Francesco; Donor, John; Dow, Peter; Dwelly, Tom; Eracleous, Mike; Eriksen, Jamey; Fan, Xiaohui; Farr, Emily; Frederick, Sara; Fries, Logan; Frinchaboy, Peter; Gaensicke, Boris T.; Ge, Junqiang; Gonzalez Avila, Consuelo; Grabowski, Katie; Grier, Catherine; Guiglion, Guillaume; Gupta, Pramod; Hall, Patrick; Hawkins, Keith; Hayes, Christian R.; Hermes, J. J.; Hernandez-Garcia, Lorena; Hogg, David W.; Holtzman, Jon A.; Ibarra-Medel, Hector Javier; Ji, Alexander; Jofre, Paula; Johnson, Jennifer A.; Jones, Amy M.; Kinemuchi, Karen; Kluge, Matthias; Koekemoer, Anton; Kollmeier, Juna A.; Kounkel, Marina; Krishnarao, Dhanesh; Krumpe, Mirko; Lacerna, Ivan; Lago, Paulo Jakson Assuncao; Laporte, Chervin; Liu, Chao; Liu, Ang; Liu, Xin; Lopes, Alexandre Roman; Macktoobian, Matin; Majewski, Steven R.; Malanushenko, Viktor; Maoz, Dan; Masseron, Thomas; Masters, Karen L.; Matijevic, Gal; McBride, Aidan; Medan, Ilija; Merloni, Andrea; Morrison, Sean; Myers, Natalie; Meszaros, Szabolcs; Negrete, C. Alenka; Nidever, David L.; Nitschelm, Christian; Oravetz, Daniel; Oravetz, Audrey; Pan, Kaike; Peng, Yingjie; Pinsonneault, Marc H.; Pogge, Rick; Qiu, Dan; Ramirez, Solange V.; Rix, Hans-Walter; Rosso, Daniela Fernandez; Runnoe, Jessie; Salvato, Mara; Sanchez, Sebastian F.; Santana, Felipe A.; Saydjari, Andrew; Sayres, Conor; Schlaufman, Kevin C.; Schneider, Donald P.; Schwope, Axel; Serna, Javier; Shen, Yue; Sobeck, Jennifer; Song, Ying-Yi; Souto, Diogo; Spoo, Taylor; Stassun, Keivan G.; Steinmetz, Matthias; Straumit, Ilya; Stringfellow, Guy; Sanchez-Gallego, Jose; Taghizadeh-Popp, Manuchehr; Tayar, Jamie; Thakar, Ani; Tissera, Patricia B.; Tkachenko, Andrew; Toledo, Hector Hernandez; Trakhtenbrot, Benny; Fernandez-Trincado, Jose G.; Troup, Nicholas; Trump, Jonathan R.; Tuttle, Sarah; Ulloa, Natalie; Vazquez-Mata, Jose Antonio; Alfaro, Pablo Vera; Villanova, Sandro; Wachter, Stefanie; Weijmans, Anne-Marie; Wheeler, Adam; Wilson, John; Wojno, Leigh; Wolf, Julien; Xue, Xiang-Xiang; Ybarra, Jason E.; Zari, Eleonora; Zasowski, Gail
    The eighteenth data release (DR18) of the Sloan Digital Sky Survey (SDSS) is the first one for SDSS-V, the fifth generation of the survey. SDSS-V comprises three primary scientific programs or "Mappers": the Milky Way Mapper (MWM), the Black Hole Mapper (BHM), and the Local Volume Mapper. This data release contains extensive targeting information for the two multiobject spectroscopy programs (MWM and BHM), including input catalogs and selection functions for their numerous scientific objectives. We describe the production of the targeting databases and their calibration and scientifically focused components. DR18 also includes & SIM;25,000 new SDSS spectra and supplemental information for X-ray sources identified by eROSITA in its eFEDS field. We present updates to some of the SDSS software pipelines and preview changes anticipated for DR19. We also describe three value-added catalogs (VACs) based on SDSS-IV data that have been published since DR17, and one VAC based on the SDSS-V data in the eFEDS field.
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    The Hercules stream as seen by APOGEE-2 South
    (2018) Hunt, Jason A. S.; Bovy, Jo; Perez-Villegas, Angeles; Holtzman, Jon A.; Sobeck, Jennifer; Chojnowski, Drew; Santana, Felipe A.; Palicio, Pedro A.; Wegg, Christopher; Gerhard, Ortwin; Almeida, Andres; Bizyaev, Dmitry; Fernandez-Trincado, Jose G.; Lane, Richard R.; Pelope Longa-Pena, Pen; Majewski, Steven R.; Pan, Kaike; Roman-Lopes, Alexandre
    The Hercules stream is a group of comoving stars in the solar neighbourhood, which can potentially be explained as a signature of either the outer Lindblad resonance (OLR) of a fast Galactic bar or the corotation resonance (CR) of a slower bar. In either case, the feature should be present over a large area of the disc. With the recent commissioning of the APOGEE-2 Southern spectrograph we can search for the Hercules stream at (l, b)=(270 degrees, 0), a direction in which the Hercules stream, if caused by the bar's OLR, would be strong enough to be detected using only the line-of-sight velocities. We clearly detect a narrow, Hercules-like feature in the data that can be traced from the solar neighbourhood to a distance of about 4 kpc. The detected feature matches well the line-of-sight velocity distribution from the fast-bar (OLR) model. Confronting the data with a model where the Hercules stream is caused by the CR of a slower bar leads to a poorer match, as the corotation model does not predict clearly separated modes, possibly because the slow-bar model is too hot.