Tracing Chemical Evolution Over The Extent Of The Milky Way's Disk With APOGEE Red Clump Stars

dc.contributor.utaustinauthorShetrone, Matthewen_US
dc.creatorNidever, David L.en_US
dc.creatorBovy, Joen_US
dc.creatorBird, Jonathan C.en_US
dc.creatorAndrews, Brett H.en_US
dc.creatorHayden, Michaelen_US
dc.creatorHoltzman, Jonen_US
dc.creatorMajewski, Steven R.en_US
dc.creatorSmith, Verneen_US
dc.creatorRobin, Annie C.en_US
dc.creatorPerez, Ana E. Garciaen_US
dc.creatorCunha, Katiaen_US
dc.creatorAllende Prieto, Carlosen_US
dc.creatorZasowski, Gailen_US
dc.creatorSchiavon, Ricardo P.en_US
dc.creatorJohnson, Jennifer A.en_US
dc.creatorWeinberg, David H.en_US
dc.creatorFeuillet, Dianeen_US
dc.creatorSchneider, Donald P.en_US
dc.creatorShetrone, Matthewen_US
dc.creatorSobeck, Jenniferen_US
dc.creatorGarcia-Hernandez, D. Anibalen_US
dc.creatorZamora, O.en_US
dc.creatorRix, Hans-Walteren_US
dc.creatorBeers, Timothy C.en_US
dc.creatorWilson, John C.en_US
dc.creatorO'Connell, Robert W.en_US
dc.creatorMinchev, Ivanen_US
dc.creatorChiappini, Cristinaen_US
dc.creatorAnders, Friedrichen_US
dc.creatorBizyaev, Dmitryen_US
dc.creatorBrewington, Howarden_US
dc.creatorEbelke, Garretten_US
dc.creatorFrinchaboy, Peter M.en_US
dc.creatorGe, Jianen_US
dc.creatorKinemuchi, Karenen_US
dc.creatorMalanushenko, Elenaen_US
dc.creatorMalanushenko, Viktoren_US
dc.creatorMarchante, Mosesen_US
dc.creatorMeszaros, Szabolcsen_US
dc.creatorOravetz, Danielen_US
dc.creatorPan, Kaikeen_US
dc.creatorSimmons, Audreyen_US
dc.creatorSkrutskie, Michael F.en_US
dc.description.abstractWe employ the first two years of data from the near-infrared, high-resolution SDSS-III/APOGEE spectroscopic survey to investigate the distribution of metallicity and alpha-element abundances of stars over a large part of the Milky Way disk. Using a sample of approximate to 10,000 kinematically unbiased red-clump stars with similar to 5% distance accuracy as tracers, the [alpha/Fe] versus [Fe/H] distribution of this sample exhibits a bimodality in [alpha/Fe] at intermediate metallicities, -0.9 < [Fe/H] < -0.2, but at higher metallicities ([Fe/H] similar to +0.2) the two sequences smoothly merge. We investigate the effects of the APOGEE selection function and volume filling fraction and find that these have little qualitative impact on the alpha-element abundance patterns. The described abundance pattern is found throughout the range 5 < R < 11 kpc and 0 < |Z| < 2 kpc across the Galaxy. The [alpha/Fe] trend of the high-alpha sequence is surprisingly constant throughout the Galaxy, with little variation from region to region (similar to 10%). Using simple galactic chemical evolution models, we derive an average star-formation efficiency (SFE) in the high-alpha sequence of similar to 4.5x10(-10) yr(-1), which is quite close to the nearly constant value found in molecular-gas-dominated regions of nearby spirals. This result suggests that the early evolution of the Milky Way disk was characterized by stars that shared a similar star-formation history and were formed in a well-mixed, turbulent, and molecular-dominated ISM with a gas consumption timescale (SFE-1) of similar to 2Gyr. Finally, while the two alpha-element sequences in the inner Galaxy can be explained by a single chemical evolutionary track, this cannot hold in the outer Galaxy, requiring, instead, a mix of two or more populations with distinct enrichment histories.en_US
dc.description.departmentMcDonald Observatoryen_US
dc.description.sponsorshipNational Aeronautics and Space Administrationen_US
dc.identifier.citationNidever, David L., Jo Bovy, Jonathan C. Bird, Brett H. Andrews, Michael Hayden, Jon Holtzman, Steven R. Majewski et al. "Tracing chemical evolution over the extent of the Milky Way's Disk with APOGEE Red Clump Stars." The Astrophysical Journal, Vol. 796, No. 1 (Nov., 2014): 38.en_US
dc.relation.ispartofserialAstrophysical Journalen_US
dc.rightsAdministrative deposit of works to Texas ScholarWorks: This works author(s) is or was a University faculty member, student or staff member; this article is already available through open access or the publisher allows a PDF version of the article to be freely posted online. The library makes the deposit as a matter of fair use (for scholarly, educational, and research purposes), and to preserve the work and further secure public access to the works of the University.en_US
dc.subjectgalaxy: abundancesen_US
dc.subjectgalaxy: disken_US
dc.subjectgalaxy: evolutionen_US
dc.subjectgalaxy: stellaren_US
dc.subjectgalactic thick disken_US
dc.subjectmono-abundance subpopulationsen_US
dc.subjectmass assembly surveyen_US
dc.subjectdigital sky surveyen_US
dc.subjectway disken_US
dc.subjectmetallicity gradientsen_US
dc.subjectnearby starsen_US
dc.subjectfaint starsen_US
dc.subjectstellar populationsen_US
dc.subjectastronomy & astrophysicsen_US
dc.titleTracing Chemical Evolution Over The Extent Of The Milky Way's Disk With APOGEE Red Clump Starsen_US

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