So I want to get the XYZ (rectangular/Cartesian) coordinates of the LRG (luminous red galaxies) catalog. The catalog is available for download from here: https://data.sdss.org/sas/dr16/eboss/lss/catalogs/DR16/ You just have to search the "LRG" ones. Since I'm not very interested in clustering at first I figured I'd download the eBOSS_LRG_full_ALLdata-vDR16.fits. In this fits file, I see RA and DEC coordinates but I don't see any measure of distance. Thus I'm not sure how to covert this RA and DEC to XYZ coordinates. I've read some papers where they say they have done this so in principle it should be possible just I am not sure how. Am I supposed to use the magnitude to somehow estimate the distance (something like this: https://ned.ipac.caltech.edu/level5/Willick/Willick1_2.html)? For some reason, I expected this would be precomputed in the catalog measurements but maybe I'm misunderstanding something.
I understand that BAO (Baryon Acoustic Oscillation) is used for determining distance. According to https://www.sdss.org/dr16/spectro/lss/ the SDSS fits files link I posted above also contains information about BAO (it is the files that contain "rec" I am using the
eBOSS_LRGpCMASS_clustering_data_rec-NGC-vDR16.fits file for example). However, I can't find what the fields mean and more importantly how to get distance from them.
Any and all help appreciated if I'm missing some documentation please let me know.