Below you will find a list of BDBS-related publications by team members. Please indicate the name of the authors, a brief overview of co-authorship (ala "Core members", "Open to all" etc), and the status (e.g., first draft circulated, submitted, accepted, or publication details).

1. R.M. Rich et al. 2020, MNRAS: '''The Blanco DECam Bulge Survey. I. The Survey Description and Early Results'''

2. C.I. Johnson et al. 2020, MNRAS: '''Blanco DECam Bulge Survey (BDBS) II: Project Performance, Data Analysis, and Early Science Results'''

3. D. Lim et al. first draft circulated: '''Blanco DECam Bulge Survey (BDBS) III: A new view on the double red clump in the Milky Way bulge through luminosity and color distribution'''

R.M. Rich, C.I. Johnson, M. Young, et al. 2020, MNRAS: The Blanco DECam Bulge Survey. I. The Survey Description and Early Results

Status: published in MNRAS, 499, 2340

Abstract: The Blanco Dark Energy Camera (DECam) Bulge survey is a Vera Rubin Observatory (LSST) pathfinder imaging survey, spanning ⇠ 200 sq. deg. of the Southern Galactic bulge, 2 <b< 13 and 11 <l< +11 . We have employed the CTIO-4m telescope and the Dark Energy Camera (DECam) to image a contiguous ⇠ 200 sq. deg. region of the relatively less reddened Southern Galactic bulge, in SDSS u + Pan-STARRSgrizY. Optical photometry with its large color baseline will be used to investigate the age and metallicity distributions of the major structures of the bulge. Included in the survey footprint are 26 globular clusters imaged in all passbands. Over much of the bulge, we have Gaia DR2 matching astrometry to i ⇠ 18, deep enough to reach the faint end of the red clump. This paper provides the background, scientific case, and description of the survey. We present an array of new reddening-corrected colour-magnitude diagrams that span the extent of Southern Galactic bulge. We show that putative young, massive "blue loop" stars proposed as a recent star forming population instead lie at ⇠ 2 kpc from the Sun and are likely red clump giants in the old disk. A bright red clump near (l, b) = (+8 , 4 ) may be a feature in the foreground disk, or related to the long bar reported in earlier work. We also report the first map of the blue horizontal branch population spanning the BDBS field of regard, and show previously reported new bulge globular clusters cannot be confirmed as real.

C.I. Johnson, R.M. Rich, M.D. Young, et al. 2020, MNRAS: Blanco DECam Bulge Survey (BDBS) II: Project Performance, Data Analysis, and Early Science Results

Status: published in MNRAS, 499, 2357

Abstract: The Blanco DECam Bulge Survey (BDBS) imaged more than 200 square degrees of the Southern Galactic bulge using the ugrizY filters of the Dark Energy Camera, and produced point spread function photometry of approximately 250 million unique sources. In this paper, we present details regarding the construction and collation of survey catalogs, and also discuss the adopted calibration and dereddening procedures. Early science results are presented with a particular emphasis on the bulge metallic- ity distribution function and globular clusters. A key result is the strong correlation (σ ∼ 0.2 dex) between (u−i)o and [Fe/H] for bulge red clump giants. We utilized this relation to find that interior bulge fields may be well described by simple closed box enrichment models while fields exterior to b ∼ −6◦ seem to require a secondary metal-poor component. Applying scaled versions of the closed box models to the outer bulge fields is shown to significantly reduce the strengths of any additional metal-poor components when compared to Gaussian mixture models. Additional results include: a confirmation that the u-band splits the sub-giant branch in M 22 as a function of metallicity, the detection of possible extra-tidal stars along the orbits of M 22 and FSR 1758, and additional evidence that NGC 6569 may have a small but discrete He spread, as evidenced by red clump luminosity variations in the reddest bands. We do not confirm previous claims that FSR 1758 is part of a larger extended structure.

D. Lim, A. J. Koch-Hansen, C. Chung, et al.: Blanco DECam Bulge Survey (BDBS) III: A new view on the double red clump in the Milky Way bulge through luminosity and color distribution

Status: submitted to A&A, Nov. 21. 2020.

Abstract: Red clump (RC) stars are one of the best stellar tracers to investigate the structure of the Milky Way (MW) bulge. Here we report on a new view on the luminosity and color distributions of the RC stars in nine bulge fields (l = 0.0°, ±4.5°; b = -6.0°, -7.5°, -9.0°) from the Blanco DECam Bulge Survey (BDBS), which covers near-ultraviolet to near-infrared bandpasses. The bright and faint RCs show contrasting distributions in (u − g)0 and (u − i)0 colors but similar distributions in (J − Ks)0 with a variation depending on the Galactic longitude, where the bright RC is typically redder than the faint RC. In particular, the RC stars are clearly divided into the bluer and redder populations when utilizing the (u − g)0 color ((u − g)0 < 2.5 for the bluer RC; (u − g)0 ≥ 2.5 for the redder RC). The bluer stars show a single clump on the faint RC regime, whereas the redder stars form double clumps on both the bright and faint RCs. The bright clump of the redder stars is dominant in the positive latitude fields, while the faint clump of those red stars is significant at negative latitudes. We also confirm that the bluer and redder stars have different peak metallicity through comparison with spectroscopy (∆[Fe/H] ∼ 0.45 dex). Therefore, our results support that the MW bulge is composed of a spheroid of metal-poor stars and it contains a boxy/peanut shape (X-shape) predominantly made up of metal-rich stars.