Milky Way Survey Catalog Of Blue Horizontal Branch Stars¶
Overview¶
This is a DESI DR1 release of blue horizontal branch (BHB) from the Milky Way Survey (MWS) working group.
The catalogue contains 6,327 spectroscopically selected BHB stars following the selection in Byström et al. (2024) (hereafter B24), applied to MWS year 1 data. The spectroscopic selection has been applied to stars targeted as BHB candidates (see Sec. 2.3 in B24), and removes stellar contaminants by making a selection in effective temperature and surface gravity (Eq. (5) and Fig. 1). The BHB absolute magnitudes have been calculated following Eq. (6).
The quality cuts described in Sec. 2.4 has been applied to the catalogue (which include e.g. removing quasars (using RR_SPECTYPE == ‘QSO’), applying radial velocity cuts, removing RRLe stars, etc). For completeness, the published catalogue contains all observations of a given BHB. To remove duplicate observations and keep only the highest quality observation, the user of this catalogue should apply the PRIMARY == True flag (found in HDU1, see paragraph below). To use the BHB catalogue like in B24, this is the only cut that needs to be applied. For more information on how to load the data and the different quality cuts available in the MWS, see the tutorial for the DESI MWS DR1 VAC here.
Data Access¶
Data URL: https://data.desi.lbl.gov/public/dr1/vac/dr1/mws-bhb/v1.0/
NERSC access:
/global/cfs/cdirs/desi/public/dr1/vac/dr1/mws-bhb/v1.0/
Documentation¶
Files¶
MWS_BHB.fits: Main catalog file of BHB stars.
Data model¶
The BHB spectroscopic selection has been applied to the RVTAB, FIBERMAP and GAIA HDUs of the main file of the MWS VAC (mws-all-pix-iron.fits), and this VAC inherits the same file structure (minus the SCORES HDU). These three HDUs contain the outputs from the RVSpecfit pipeline (described in the MWS overview paper by Cooper et al. (2023) Sec. 6.1), DESI observational information, and a crossmatch with Gaia DR3, respectively. These HDUs have been described here (HDU1, HDU2 and HDU4, respectively).
Added to the FIBERMAP HDU are an additional five columns:
| Name | Type | Units | Description |
|---|---|---|---|
| MAG_DERED_G | float32 | mag | dereddened Legacy Survey g magnitude |
| MAG_DERED_R | float32 | mag | dereddened Legacy Survey r magnitude |
| MAG_DERED_Z | float32 | mag | dereddened Legacy Survey z magnitude |
| ABS_MAG_G | float64 | mag | absolute magnitude in the g-band calculated using Eq. (6) in B24 |
| DIST | float64 | kpc | heliocentric distance in kpc |
Contact¶
Contact Amanda Byström with any questions.