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Blanco DECam Bulge Survey (BDBS), IV. Metallicity distributions and bulge structure from 2.6 million red clump stars

We present photometric metallicity measurements for a sample of 2.6 million bulge red clump stars extracted from the Blanco DECam Bulge Survey (BDBS). Similar to previous studies, we find that the bulge exhibits a strong vertical metallicity gradient, and that at least two peaks in the metallicity d...

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Main Authors: Johnson, Christian I. (Author) , Rich, R Michael (Author) , Simion, Iulia T (Author) , Young, Michael D (Author) , Clarkson, William I (Author) , Pilachowski, Catherine A (Author) , Michael, Scott (Author) , Marchetti, Tommaso (Author) , Soto, Mario (Author) , Kunder, Andrea (Author) , Koch-Hansen, Andreas (Author) , Katherina Vivas, A (Author) , Joyce, Meridith (Author) , Shen, Juntai (Author) , Osmond, Alexis (Author)
Format: Article (Journal)
Language:English
Published: 09 July 2022
In: Monthly notices of the Royal Astronomical Society
Year: 2022, Volume: 515, Issue: 1, Pages: 1469-1491
ISSN:1365-2966
DOI:10.1093/mnras/stac1840
Online Access:Verlag, lizenzpflichtig, Volltext: https://doi.org/10.1093/mnras/stac1840
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Author Notes:Christian I. Johnson, R. Michael Rich, Iulia T. Simion, Michael D.Young, William I. Clarkson, Catherine A. Pilachowski, Scott Michael, Tommaso Marchetti, Mario Soto, Andrea Kunder, Andreas J. Koch-Hansen, A.Katherina Vivas, Meridith Joyce, Juntai Shen and Alexis Osmond
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Summary:We present photometric metallicity measurements for a sample of 2.6 million bulge red clump stars extracted from the Blanco DECam Bulge Survey (BDBS). Similar to previous studies, we find that the bulge exhibits a strong vertical metallicity gradient, and that at least two peaks in the metallicity distribution functions appear at b < −5°. We can discern a metal-poor ([Fe/H] ∼ −0.3) and metal-rich ([Fe/H] ∼ +0.2) abundance distribution that each show clear systematic trends with latitude, and may be best understood by changes in the bulge’s star formation/enrichment processes. Both groups exhibit asymmetric tails, and as a result we argue that the proximity of a star to either peak in [Fe/H] space is not necessarily an affirmation of group membership. The metal-poor peak shifts to lower [Fe/H] values at larger distances from the plane while the metal-rich tail truncates. Close to the plane, the metal-rich tail appears broader along the minor axis than in off-axis fields. We also posit that the bulge has two metal-poor populations - one that belongs to the metal-poor tail of the low latitude and predominantly metal-rich group, and another belonging to the metal-poor group that dominates in the outer bulge. We detect the X-shape structure in fields with |Z| > 0.7 kpc and for stars with [Fe/H] > −0.5. Stars with [Fe/H] < −0.5 may form a spheroidal or ‘thick bar’ distribution while those with [Fe/H] $\gtrsim$ −0.1 are strongly concentrated near the plane.
Item Description:Gesehen am 14.09.2022
Physical Description:Online Resource
ISSN:1365-2966
DOI:10.1093/mnras/stac1840

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