Mapping the Interstellar Reddening and Extinction toward Baade's Window Using Minimum Light Colors of ab-type RR Lyrae Stars: Revelations from the De-reddened Color-Magnitude Diagrams

Abhijit Saha, A. Katherina Vivas, Edward W. Olszewski, Verne Smith, Knut Olsen, Robert Blum, Francisco Valdes, Jenna Claver, Annalisa Calamida, Alistair R. Walker, Thomas Matheson, Gautham Narayan, Monika Soraisam, Katia Cunha, T. Axelrod, Joshua S. Bloom, S. Bradley Cenko, Brenda Frye, Mario Juric, Catherine KaleidaAndrea Kunder, Adam Miller, David Nidever, Stephen Ridgway

Research output: Contribution to journalArticle

3 Scopus citations

Abstract

We have obtained repeated images of six fields toward the Galactic bulge in five passbands (u, g, r, i, z) with the DECam imager on the Blanco 4 m telescope at CTIO. From more than 1.6 billion individual photometric measurements in the field centered on Baade's window, we have detected 4877 putative variable stars. A total of 474 of these have been confirmed as fundamental mode RR Lyrae stars, whose colors at minimum light yield line-of-sight reddening determinations, as well as a reddenning law toward the Galactic Bulge, which differs significantly from the standard R V = 3.1 formulation. Assuming that the stellar mix is invariant over the 3 square-degree field, we are able to derive a line-of-sight reddening map with sub-arcminute resolution, enabling us to obtain de-reddened and extinction corrected color-magnitude diagrams (CMDs) of this bulge field using up to 2.5 million well-measured stars. The corrected CMDs show unprecedented detail and expose sparsely populated sequences: for example, delineation of the very wide red giant branch, structure within the red giant clump, the full extent of the horizontal branch, and a surprising bright feature that is likely due to stars with ages younger than 1 Gyr. We use the RR Lyrae stars to trace the spatial structure of the ancient stars and find an exponential decline in density with Galactocentric distance. We discuss ways in which our data products can be used to explore the age and metallicity properties of the bulge, and how our larger list of all variables is useful for learning to interpret future LSST alerts.

Original languageEnglish (US)
Article number30
JournalAstrophysical Journal
Volume874
Issue number1
DOIs
StatePublished - Mar 20 2019

Keywords

  • Galaxy: bulge
  • Galaxy: stellar content
  • Galaxy: structure
  • ISM: dust, extinction
  • methods: data analysis
  • stars: variables: RR Lyrae

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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    Saha, A., Vivas, A. K., Olszewski, E. W., Smith, V., Olsen, K., Blum, R., Valdes, F., Claver, J., Calamida, A., Walker, A. R., Matheson, T., Narayan, G., Soraisam, M., Cunha, K., Axelrod, T., Bloom, J. S., Cenko, S. B., Frye, B., Juric, M., ... Ridgway, S. (2019). Mapping the Interstellar Reddening and Extinction toward Baade's Window Using Minimum Light Colors of ab-type RR Lyrae Stars: Revelations from the De-reddened Color-Magnitude Diagrams. Astrophysical Journal, 874(1), [30]. https://doi.org/10.3847/1538-4357/ab07ba