Chemically Dissected Rotation Curves of the Galactic Bulge from Main-sequence Proper Motions
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2018-05
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en
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Institute of Physics Publishing
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Licencia CC
Resumen
We report results from an exploratory study implementing a new probe of Galactic evolution using archival Hubble Space Telescope imaging observations. Precise proper motions are combined with photometric relative metallicity and temperature indices, to produce the proper-motion rotation curves of the Galactic bulge separately for metal-poor and metal-rich main-sequence samples. This provides a "pencil-beam" complement to large-scale wide-field surveys, which to date have focused on the more traditional bright giant branch tracers. We find strong evidence that the Galactic bulge rotation curves drawn from "metal-rich" and "metal-poor" samples are indeed discrepant. The "metal-rich" sample shows greater rotation amplitude and a steeper gradient against line-of-sight distance, as well as possibly a stronger central concentration along the line of sight. This may represent a new detection of differing orbital anisotropy between metal-rich and metal-poor bulge objects. We also investigate selection effects that would be implied for the longitudinal proper-motion cut often used to isolate a "pure-bulge" sample. Extensive investigation of synthetic stellar populations suggests that instrumental and observational artifacts are unlikely to account for the observed rotation curve differences. Thus, proper-motion-based rotation curves can be used to probe chemodynamical correlations for main-sequence tracer stars, which are orders of magnitude more numerous in the Galactic bulge than the bright giant branch tracers. We discuss briefly the prospect of using this new tool to constrain detailed models of Galactic formation and evolution. © 2018. The American Astronomical Society. All rights reserved.
Notas
Indexación: Scopus.
This work has made use of data from the European Space Agency (ESA) mission Gaia (https://www.cosmos.esa.int/gaia), processed by the Gaia Data Processing and Analysis Consortium (DPAC, https://www.cosmos.esa.int/web/gaia/dpac/consortium). Funding for the DPAC has been provided by national institutions, in particular the institutions participating in the Gaia Multilateral Agreement. W.I.C. acknowledges support from the University of Michigan–Dearborn through startup funding from the Department of Natural Sciences (project U039878) and from the Office of Research and Sponsored Programs (project U042549, The Milky Way Bulge at UM-Dearborn), partial support from HST program GO-12020 (PI Clarkson), and equipment funding from a Theodore Dunham Jr. Grant from the Foundation Center (award 1179, project N017429). V.P.D. is supported by STFC Consolidated grant ST/M000877/1. D.M. and M.Z. acknowledge support by the Ministry of Economy, Development, and Tourism's Millennium Science Initiative through grant IC120009, awarded to The Millennium Institute of Astrophysics (MAS); by Fondecyt Regular grants 1170121 and 1150345; and by the BASAL-CATA Center for Astrophysics and Associated Technologies PFB-06. All the external software packages and methods used in this work are freely available to the community. This research made use of Astropy, a community-developed core Python package for Astronomy. This work made use of the astroML suite of tools for machine learning in Astronomy. This work made use of scikit-learn. This work has made use of the pysynphot synthetic photometry utilities. This work has made use of BaSTI web tools. W.I.C. thanks Jay Anderson, Jo Bovy, Dana Casetti-Dinescu, Oscar Gonzalez, Noé Kains, Andreas Koch, Vera Kozhurina-Platais, and Laura Watkins for enlightening interaction at various stages of this analysis. This work was only possible thanks to the distortion solution and astrometric measurement methods developed by Jay Anderson. We thank Santi Cassisi for assistance with the BaSTI synthetic stellar population tools and for kindly providing custom synthetic populations at high metallicity. Finally, we thank the anonymous referee, whose thorough reading and insightful comments led to substantial improvement of the manuscript.
This work has made use of data from the European Space Agency (ESA) mission Gaia (https://www.cosmos.esa.int/gaia), processed by the Gaia Data Processing and Analysis Consortium (DPAC, https://www.cosmos.esa.int/web/gaia/dpac/consortium). Funding for the DPAC has been provided by national institutions, in particular the institutions participating in the Gaia Multilateral Agreement. W.I.C. acknowledges support from the University of Michigan–Dearborn through startup funding from the Department of Natural Sciences (project U039878) and from the Office of Research and Sponsored Programs (project U042549, The Milky Way Bulge at UM-Dearborn), partial support from HST program GO-12020 (PI Clarkson), and equipment funding from a Theodore Dunham Jr. Grant from the Foundation Center (award 1179, project N017429). V.P.D. is supported by STFC Consolidated grant ST/M000877/1. D.M. and M.Z. acknowledge support by the Ministry of Economy, Development, and Tourism's Millennium Science Initiative through grant IC120009, awarded to The Millennium Institute of Astrophysics (MAS); by Fondecyt Regular grants 1170121 and 1150345; and by the BASAL-CATA Center for Astrophysics and Associated Technologies PFB-06. All the external software packages and methods used in this work are freely available to the community. This research made use of Astropy, a community-developed core Python package for Astronomy. This work made use of the astroML suite of tools for machine learning in Astronomy. This work made use of scikit-learn. This work has made use of the pysynphot synthetic photometry utilities. This work has made use of BaSTI web tools. W.I.C. thanks Jay Anderson, Jo Bovy, Dana Casetti-Dinescu, Oscar Gonzalez, Noé Kains, Andreas Koch, Vera Kozhurina-Platais, and Laura Watkins for enlightening interaction at various stages of this analysis. This work was only possible thanks to the distortion solution and astrometric measurement methods developed by Jay Anderson. We thank Santi Cassisi for assistance with the BaSTI synthetic stellar population tools and for kindly providing custom synthetic populations at high metallicity. Finally, we thank the anonymous referee, whose thorough reading and insightful comments led to substantial improvement of the manuscript.
Palabras clave
Galaxy: bulge, Galaxy: disk, Galaxy: kinematics and dynamics, Instrumentation: high angular resolution, Methods: data analysis, Techniques: photometric
Citación
Astrophysical Journal, 858(1), art. no. 46.