Description file for sdss-ukidss-enviros.fits  (binary-format table)

Data selection and derived parameters are described in detail by
Baldry, Sullivan, Rani & Turner (2021) ui.adsabs.harvard.edu/abs/2021MNRAS.500.1557B/abstract
Title: Compact galaxies and the size-mass galaxy distribution from a colour-selected sample
at 0.04 < z < 0.15 supplemented by ugrizYJHK photometric redshifts.

These data, in the fits file, are restricted to 0.04 < z < 0.15 to give 163186 galaxies.
This is the primary sample described in the paper. Some visual cleaning has taken place but only for compact galaxies.
The file provides the environmental measurements described in Section 4.6. 

Comoving distances were measured to the three nearest neighbours that were part of the
density-defining population (DDP). The DDP was selected: 
(i) with log M* > 10.5 or (log M* > 10.0 and quenched); and
(ii) with a spec-z or (a photo-z that had a nominal error < 0.015).
Note the DDP extends beyond the redshift range of the sample to avoid redshift boundary effects.
However, the densities are not corrected for survey edge effects. 

Since this is not a volume-limited sample beyond about z=0.08, an adjustment is made
as per Eq. 20 to create a log(1+delta) value for the environment. delta is the overdensity
wrt. a uniform population. For most galaxies, delta > 0 because galaxies are clustered.

Columns:

OBJID            SDSS objid from DR14 query (match to sdss-ukidss-data.fits or other SDSS data via casjobs)
DIST1            Comoving distance to nearest DDP neighbour (Mpc)
DIST2            Comoving distance to 2nd nearest DDP neighbour (Mpc)
DIST3            Comoving distance to 3rd nearest DDP neighbour (Mpc)
LOG_SIGMA        Uncorrected environmental surface density as per Eq. 19 (sigma has units of per Mpc^2)
DELTA_LOG_SIGMA  log(1+delta) as per Eq. 20 (dimensionless)