Guadalupe VAC (DR1 Supplement)¶

Overview ¶

This page describes the Guadalupe value-added catalog, which will be publicly released as part of the DESI Data Release 1 (DESI/DR1) sometime in 2024 (exact date TBD).

Please refer to the Acknowledgments section for the conditions for using this VAC.

Note

We only document the latest version of this VAC here; please see below for information regarding previous versions.

Data Content & Access ¶

Data from the Guadalupe VAC can be accessed at any of the following links:

Data url	https://data.desi.lbl.gov/public/dr1/vac/dr1/fastspecfit/guadalupe/v3.1
NERSC (for collaborators)	`/global/cfs/cdirs/desi/public/dr1/vac/dr1/fastspecfit/guadalupe/v3.1`

For more information regarding the content and organization of the VAC, please click on the following links:

Summary Statistics ¶

The following table summarizes the size and number of targets in each merged catalog.

Note

The last catalog listed in the table is a super-merge of all the preceding catalogs, i.e., a merge over all surveys and programs.

File Name	File Size	Number of Targets
fastspec-guadalupe-special-dark.fits	15.1 MB	3,848
fastspec-guadalupe-special-bright.fits	37.5 MB	9,598
fastspec-guadalupe-main-bright.fits	4.15 GB	1,092,041
fastspec-guadalupe-main-dark.fits	4.3 GB	1,131,858
fastspec-guadalupe.fits	8.52 GB	2,237,345

The following table summarizes the number of QSO targets whose redshift has been updated using the procedure documented here.

Catalog	Number of Objects	Number with Corrected Redshifts
fastspec-guadalupe-main-bright.fits	1,092,041	156
fastspec-guadalupe-main-dark.fits	1,131,858	22,445
fastspec-guadalupe-special-bright.fits	9,598	0
fastspec-guadalupe-special-dark.fits	3,848	111
fastspec-guadalupe.fits	2,237,345	22,712

Code & Template Versions ¶

The following tables document the code versions and environment variables used to produce this VAC. For details regarding the revision history of FastSpecFit, please see the change log.

Note that the tagged dependencies can be retrieve from any FITS file with the following bit of code:

import fitsio
from desiutil.depend import Dependencies
codever = Dependencies(fitsio.read_header('/path/to/fastspecfit/file.fits, ext=0))
for codename, version in codever.items():
    print(codename, version)

Software Package	Version(s)
python	3.10.8
numpy	1.22.4
scipy	1.8.1
astropy	5.2.1
yaml	6.0
matplotlib	3.6.2
fitsio	1.1.8
desiutil	3.4.2
desispec	0.60.2
desitarget	2.7.0
desimodel	0.19.0
speclite	0.17
fastspecfit	2.5.0

Environment Variable	Value
DESI_ROOT	/dvs_ro/cfs/cdirs/desi
DUST_DIR	/dvs_ro/cfs/cdirs/cosmo/data/dust/v0_1
FPHOTO_DIR	/dvs_ro/cfs/cdirs/desi/external/legacysurvey/dr9
FTEMPLATES_DIR	/dvs_ro/cfs/cdirs/desi/science/gqp/templates/fastspecfit
FTEMPLATES_FILE	ftemplates-chabrier-1.3.0.fits (see README.txt)
FPHOTO_FILE	/global/common/software/desi/perlmutter/desiconda/20230111-2.1.0/code/fastspecfit/2.5.0/lib/python3.10/site-packages/fastspecfit/data/legacysurvey-dr9.yaml
EMLINES_FILE	/global/common/software/desi/perlmutter/desiconda/20230111-2.1.0/code/fastspecfit/2.5.0/lib/python3.10/site-packages/fastspecfit/data/emlines.ecsv

Notes & Known Issues ¶

In this section we briefly document issues or problems which were identified with the VAC after its final release, and provide additional details regarding previous versions of this VAC.

Please see the change log for a record of what code and data model changes have occurred since these versions were released and to report additional problems or to request new features please open a ticket.

v3.1 (latest release)¶

Release date: January 2024
FastSpecFit version: 2.5.0
Templates: ftemplates-chabrier-1.3.0.fits (see README.txt).
Notes:
- Several updates to the spectrophotometric templates aimed at addressing the stellar mass bias identified in issue/#159 (see PR/#166):
  - Templates are now just solar metallicity (previously 0.1, 1, and 1.6 times solar).
  - Five age bins now (vs 8 previously).
  - Expanded velocity dispersion grid (new measurable maximum value is now 475 km/s).
- Correction to how the light-weighted ages, dust attenuations, and SFRs were being computed.
- When fitting the broad+narrow emission-line model, [OIII] 4959,5007 is now fitted separately and the narrow Balmer+helium+forbidden line-widths and velocity shifts are all tied together.
- All known bugs fixed.
Known issues:
- None at this time.

v3.0 ¶

Release date: August 2023
FastSpecFit versions: 2.4.1, 2.4.2
Templates: ftemplates-chabrier-1.1.0.fits (see README.txt).
Notes:
- Minor updates to spectrophotometric templates.
- Just two rounds of emission-line fitting, not three (see PR/#151).
- Updated IGM attenuation coefficients (see PR/#136).
- Major algorithmic updates related to how emission-line amplitudes, fluxes, and inverse variances are computed, including a bug fix which the emission-line model spectra were not being convolved with the resolution matrix (see PR/#137).
Known Issues:
- Warning: Stellar masses are systematically higher (by 0.2-0.5 dex) compared to other methods, so they should be used with caution (see issue/#159). Similarly, star-formation rates and other SPS model parameters have not been fully validated.
- Bug: Fluxes (and EWs) of lines which lie in the camera-overlap region are overestimated by a factor of 2 due to a bug handling the different pixel scale (fixed in PR/#157).

v2.0 ¶

Release date: February 2023
FastSpecFit versions: 2.1.0, 2.1.1
Templates: ftemplates-chabrier-1.0.0.fits (see README.txt).
Notes:
- Major update of underlying spectrophotometric templates.
Known Issues:
- Bug: [OII] 7320,7330 doublet amplitude ratio incorrectly inverted (fixed in PR/#120).
- Bug: Artificial redshift dependence in derived stellar masses due to age prior (fixed in PR/#132).
- Bug: Emission-line subtracted Dn(4000) values incorrectly computed (fixed in PR/#135).

v1.0 ¶

Release date: August 2022
FastSpecFit versions: 1.0.0, 1.0.1
Templates: SSP-CKC14z/v1.0
Notes & Known Issues:
- First major release; many issues addressed in future releases.