ASTRA-DESI DR1 Release v0.12

ASTRA-DESI Data Release 1 (DR1)

This record bundles the ASTRA-DESI DR1 products for the two DESI survey regions (NGC and SGC). Every catalogue is delivered as a compressed FITS binary table (.fits.gz) whose first extension (HDU 1) contains the data. File headers store the keywords RELEASE=DR1 and the corresponding ZONE label for quick checks.

The sky partition used in this release is mask-based rather than box-based. The survey footprint is defined as a HEALPix mask combining DESI tile coverage and LSS object coverage, requiring a minimum completeness threshold of ≥4 tiles per pixel. The resulting mask is then split into NGC and SGC according to the right ascension of the HEALPix pixel centers.

Tracer
Number of objects

BGS BRIGHT
305,900

LRG
78,668

ELG
119,015

QSO
100,331

Directory layout

The archive preserves the NERSC production tree. Top-level folders contain:

raw/ – merged real and random catalogues per region.

classification/ – neighbour count summaries per tracer and random iteration.

probabilities/ – web-type membership probabilities derived from the classification counts.

groups/ – watershed groups for a given tracer and region (NGC or SGC).

Naming conventions

raw/zone_REGION.fits.gz – Region NGC or SGC.

classification/zone_REGION_classified.fits.gz – combined tracer summary for the region.

probabilities/zone_REGION_probability.fits.gz – per-object web-type probabilities.

groups/TYPE_TRACER_REGION.fits.gz – per-object web-type groups.

Column reference

Raw catalogues (raw/*.fits.gz)

Column
Type
Description

TARGETID
int64
DESI target identifier.

RA
float64
Right ascension in degrees.

DEC
float64
Declination in degrees.

Z
float64
Spectroscopic redshift.

XCART, YCART, ZCART
float64
Comoving Cartesian coordinates (Mpc) computed with the Planck18 cosmology.

TRACERTYPE
string
Tracer label with suffix _DATA or _RAND (BGS_BRIGHT, ELG, LRG, QSO).

RANDITER
int32
-1 for real objects, otherwise the random iteration index (0–99).

SED_SFR
float64
Star formation rate derived from SED fitting.

SED_MASS
float64
Stellar mass derived from SED fitting.

FLUX_G
float64
Observed flux in the g photometric band.

FLUX_R
float64
Observed flux in the r photometric band.

Each raw file merges all tracers for its zone. Random catalogues mirror the data counts for every tracer and random iteration. 

Additional columns SED_SFR, SED_MASS, FLUX_G, and FLUX_R were incorporated from the DESI DR1 value-added catalogues associated with the emission-line sample: https://data.desi.lbl.gov/doc/releases/dr1/vac/stellar-mass-emline/. These quantities are derived via SED fitting using CIGALE (Zou et al. 2024).

Classification catalogues (classification/*.fits.gz)

Column
Type
Description

TARGETID
int64
Identifier of the central object.

RANDITER
int32
-1 for data rows, otherwise the random catalogue index.

ISDATA
bool
True for data rows; False for random iterations.

NDATA
int32
Number of neighbour pairs built from data tracers for this target.

NRAND
int32
Number of neighbour pairs contributed by random tracers.

TRACERTYPE
string
Tracer family (BGS_BRIGHT, ELG, LRG, QSO).

Probability catalogues (probabilities/*.fits.gz)

Column
Type
Description

TARGETID
int64
Identifier of the object.

TRACERTYPE
string
Tracer family.

PVOID
float32
Probability of the object being a void class.

PSHEET
float32
Probability of the sheet class.

PFILAMENT
float32
Probability of the filament class.

PKNOT
float32
Probability of the knot class.

Watershed group catalogues

Each file contains a primary header plus two binary-table extensions:

HDU 1: VOIDS (one row per retained group).

HDU 2: POINT_MEMBERSHIP (one row per data/random point).

Primary-header keywords include TRACER, CAP, NVOIDS, H, OMEGA_M, RTHRESH, and WMODE.

- Group catalogues (VOIDS, HDU 1)

Column
Type
Description

VOID_ID
int32
Group identifier.

N_DATA_IN_GROUP
int32
Number of data members in the group.

N_RAND_IN_GROUP
int32
Number of random members in the group.

RA
float64
Group center right ascension (deg).

DEC
float64
Group center declination (deg).

REDSHIFT
float64
Redshift of the group center from comoving-distance inversion.

X, Y, Z
float64
Group center Cartesian coordinates (Mpc/h).

R_EFF
float64
Effective RMS radius of members around the group center (Mpc/h).

SEMI_AXIS_A, SEMI_AXIS_B, SEMI_AXIS_C
float64
Principal semi-axes from the inertia tensor (Mpc/h).

ELLIP
float32
Ellipticity, defined as 1 - C/A.

- Point membership (POINT_MEMBERSHIP, HDU 2)

Column
Type
Description

NODE_INDEX
int32
Internal index in the combined data+random graph.

TARGETID
int64
DESI target identifier.

IS_DATA
int8
1 for data rows, 0 for random rows.

GROUPID
int32
Assigned watershed group ID; -1 means unassigned.

VOID_CLASS_ID
int8
Reserved class field (default -1).

VOID_CLASS
string
Reserved class label (default unknown).

R
float32
Local contrast statistic.

N_DATA
int32
Number of data neighbours.

N_RAND
int32
Number of random neighbours.

RA, DEC, Z
float64
Sky coordinates and redshift of each point.

X_CART, Y_CART, Z_CART
float64
Cartesian coordinates (Mpc/h).

Using the catalogues

All FITS tables are compressed with gzip.

Random catalogues use RANDITER values 0–99; filtering on RANDITER >= 0 isolates the random iterations.

The Cartesian coordinates assume the Planck18 cosmology provided by astropy.cosmology.Planck18.

The masks are distributed as a compressed archive (masks.tar.gz) containing FITS maps with the following naming convention:

dr1_mask_{program}_nside{nside}_final.fits – binary mask defining the valid survey footprint for each program (bright or dark). Pixels with value 1 belong to the footprint, while 0 indicates excluded regions.

dr1_mask_{program}_nside{nside}_ngc.fits – mask restricted to the North Galactic Cap (NGC).

dr1_mask_{program}_nside{nside}_sgc.fits – mask restricted to the South Galactic Cap (SGC).

Here, {program} corresponds to the DESI observing program (bright for BGS tracers and dark for LRG, ELG, and QSO), and {nside} indicates the HEALPix resolution parameter.

For reproducibility, additional files are provided:

dr1_mask_{program}_nside{nside}_maps.npz – compressed NumPy archive containing intermediate maps used in the mask construction, including tile coverage, LSS object counts, and smoothed mask representations.