The apache point observatory galactic evolution experiment: First detection of high-velocity milky way bar stars

David L. Nidever, Gail Zasowski, Steven R. Majewski, Jonathan Bird, Annie C. Robin, Inma Martinez-Valpuesta, Rachael L. Beaton, Ralph Schönrich, Mathias Schultheis, John C. Wilson, Michael F. Skrutskie, Robert W. O'Connell, Matthew Shetrone, Ricardo P. Schiavon, Jennifer A. Johnson, Benjamin Weiner, Ortwin Gerhard, Donald P. Schneider, Carlos Allende Prieto, Kris SellgrenDmitry Bizyaev, Howard Brewington, Jon Brinkmann, Daniel J. Eisenstein, Peter M. Frinchaboy, Ana Elia García Pérez, Jon Holtzman, Fred R. Hearty, Elena Malanushenko, Viktor Malanushenko, Demitri Muna, Daniel Oravetz, Kaike Pan, Audrey Simmons, Stephanie Snedden, Benjamin A. Weaver

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Abstract

Commissioning observations with the Apache Point Observatory Galactic Evolution Experiment (APOGEE), part of the Sloan Digital Sky Survey III, have produced radial velocities (RVs) for 4700K/M-giant stars in the Milky Way (MW) bulge. These high-resolution (R 22, 500), high-S/N (>100 per resolution element), near-infrared (NIR; 1.51-1.70 μm) spectra provide accurate RVs (εV 0.2kms-1) for the sample of stars in 18 Galactic bulge fields spanning -1°<l < 20°, |b| < 20°, and δ > -32°. This represents the largest NIR high-resolution spectroscopic sample of giant stars ever assembled in this region of the Galaxy. A cold (σV 30kms-1), high-velocity peak (V GSR ≈ +200kms-1) is found to comprise a significant fraction (10%) of stars in many of these fields. These high RVs have not been detected in previous MW surveys and are not expected for a simple, circularly rotating disk. Preliminary distance estimates rule out an origin from the background Sagittarius tidal stream or a new stream in the MW disk. Comparison to various Galactic models suggests that these high RVs are best explained by stars in orbits of the Galactic bar potential, although some observational features remain unexplained.

Original languageEnglish (US)
Article numberL25
JournalAstrophysical Journal Letters
Volume755
Issue number2
DOIs
StatePublished - Aug 20 2012

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All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

Cite this

Nidever, D. L., Zasowski, G., Majewski, S. R., Bird, J., Robin, A. C., Martinez-Valpuesta, I., Beaton, R. L., Schönrich, R., Schultheis, M., Wilson, J. C., Skrutskie, M. F., O'Connell, R. W., Shetrone, M., Schiavon, R. P., Johnson, J. A., Weiner, B., Gerhard, O., Schneider, D. P., Allende Prieto, C., ... Weaver, B. A. (2012). The apache point observatory galactic evolution experiment: First detection of high-velocity milky way bar stars. Astrophysical Journal Letters, 755(2), [L25]. https://doi.org/10.1088/2041-8205/755/2/L25