Lyman-alpha Year 1 Deltas Catalog¶
Overview¶
This value-added catalog contains the measured Lyman-alpha forest fluctuations in regions A (1040 to 1025 Angstrom) and B (920 to 1020 Angstrom) along with the fluctuations in the CIII region (1600 to 1850 Angstrom) from DESI DR1 data. For additional information see Ramírez-Pérez et al. (2024)
Data Access¶
Data URL: https://data.desi.lbl.gov/public/dr1/vac/dr1/lya-deltas/
NERSC access:
/global/cfs/cdirs/desi/public/dr1/vac/dr1/lya-deltas/
Documentation¶
The full data model can be accessed with the picca documentation on GitHub.
File Structure¶
The sub-directories delta-ciii-0-0/, delta-lya-0-0/, and delta-lyb-0-0/ contain the flux transmission field and the complementary output files corresponding to the CIII, Lyman-alpha and Lyman-beta regions respectively. Within the sub-directories are also the input and configuration files along with the slurm script to reproduce these catalogs.
Reproduction¶
To reproduce this catalog, the software picca is needed. Instructions to install it can be found in its GitHub repository. This catalog was generated using picca v9.0.0
Once the code is installed, the catalog can be easily reproduced with picca_delta_extraction.py and the configuration files located within each tracer directory:
continuum_fitting_mask.txt: Mask used in picca runspicca_delta.ini: Configuration used for the calibration run
First the calibration:
picca_delta_extraction.py delta-ciii-0-0/picca_delta.ini
And then the individual tracers:
picca_delta_extraction.py delta-lya-0-0/picca_delta.ini
picca_delta_extraction.py delta-lyb-0-0/picca_delta.ini
Flux-transmission field data model¶
The flux-transmission field is stored under delta-TRACER-0-0/Delta/. This folder contains per-HEALPixel files, which contain the main output from the picca delta extraction: the Lyman-alpha transmission fluctuations for all analysed quasars in a given HEALPixel. Each file contains the mentioned flux-transmission field, metadata, and quasar continua. TRACER is one of lya, lyb or ciii.
- Naming convention:
delta-HEALPIX.fits.gz, whereHEALPIXis the HEALPixel ID - File type: FITS
| HDU Number | EXTNAME | Type | Contents |
|---|---|---|---|
| HDU0_ | PRIMARY | PRIMARY | — |
| HDU1_ | LAMBDA | IMAGE | Wavelength grid |
| HDU2_ | METADATA | BINTABLE | Per-forest metadata |
| HDU3_ | DELTA_BLIND | IMAGE | Flux-transmission field in wavelength bins |
| HDU4_ | WEIGHT | IMAGE | Weights in wavelength bins |
| HDU5_ | CONT | IMAGE | Quasar continua in wavelength bins |
Wavelength grid¶
EXTNAME = LAMBDA
| Header Keyword | Example Value | Type | Comment |
|---|---|---|---|
| NAXIS | 1 | int | Number of array dimensions |
| NAXIS1 | 2716 | int | Number of wavelength pixels |
| WAVE_SOLUTION | lin | str | Chosen wavelength solution |
| DELTA_LAMBDA | 0.8 | float | Pixel step |
| BUNITS | Angstrom | str | Wavelength units |
Per-forest metadata¶
EXTNAME = METADATA
| Header Keyword | Example Value | Type | Comment |
|---|---|---|---|
| NAXIS | 2 | int | Number of array dimensions |
| NAXIS1 | 84 | int | Table width |
| NAXIS2 | 340 | int | Number of forests |
| BLINDING | none | char[12] | Blinding scheme used |
Column descriptions:
| Name | Type | Units | Description |
|---|---|---|---|
| LOS_ID | int64 | — | PICCA unique target ID |
| RA | float64 | rad | Target Right Ascension (J2000) |
| DEC | float64 | rad | Target Declination (J2000) |
| Z | float64 | — | Redshift |
| MEANSNR | float64 | — | Mean signal-to-noise ratio |
| TARGETID | int64 | — | Unique 64-bit identifier for each object observed by DESI |
| NIGHT | char[12] | — | Observation night(s) |
| PETAL | char[12] | — | Observation petal(s) |
| TILE | char[12] | — | Observation tile(s) |
Flux-transmission field¶
EXTNAME = DELTA_BLIND
| Header Keyword | Example Value | Type | Comment |
|---|---|---|---|
| NAXIS | 2 | int | Number of array dimensions |
| NAXIS1 | 2716 | int | Number of wavelength pixels |
| NAXIS2 | 340 | int | Number of forests |
| BUNITS | — | str | Delta units (unitless) |
Weights¶
EXTNAME = WEIGHT
| Header Keyword | Example Value | Type | Comment |
|---|---|---|---|
| NAXIS | 2 | int | Number of array dimensions |
| NAXIS1 | 2716 | int | Number of wavelength pixels |
| NAXIS2 | 340 | int | Number of forests |
| BUNITS | — | str | Weight units (unitless) |
Quasar continua¶
EXTNAME = CONT
| Header Keyword | Example Value | Type | Comment |
|---|---|---|---|
| NAXIS | 2 | int | Number of array dimensions |
| NAXIS1 | 2716 | int | Number of wavelength pixels |
| NAXIS2 | 340 | int | Number of forests |
| BUNITS | — | str | Quasar continuum units (unitless) |
Data model for auxiliary files¶
Under delta-TRACER-0-0/Log/ there are complementary output files:
The files delta_attributes(_iteration*).fits.gz contain information about the fits performed in the analysis, for variance functions and forest continua, as well as delta statistics at each iteration.
- Naming convention:
delta-attributes.fits.gzordelta-attributes_iterationITERATION.fits.gz, whereITERATIONis the iteration step - File type: FITS
| HDU Number | EXTNAME | Type | Contents |
|---|---|---|---|
| HDU0_ | PRIMARY | PRIMARY | — |
| HDU1_ | STACK_DELTAS | BINTABLE | Delta mean properties |
| HDU2_ | VAR_FUNC | BINTABLE | Variance fitted functions |
| HDU3_ | CONT | BINTABLE | Mean quasar continuum |
| HDU4_ | FIT_METADATA | BINTABLE | Extra fit metadata |
Delta mean properties¶
EXTNAME = STACK_DELTAS
| Header Keyword | Example Value | Type | Comment |
|---|---|---|---|
| NAXIS | 2 | int | Number of array dimensions |
| NAXIS1 | 24 | int | Table width |
| NAXIS2 | 2716 | int | Number of wavelength pixels |
Column descriptions:
| Name | Type | Units | Description |
|---|---|---|---|
| LOGLAM | float64 | log(Angstrom) | log(wavelength) |
| STACK | float64 | — | mean(1 + delta) |
| WEIGHT | float64 | — | Mean weight |
Variance fitted functions¶
EXTNAME = VAR_FUNC
| Header Keyword | Example Value | Type | Comment |
|---|---|---|---|
| NAXIS | 2 | int | Number of array dimensions |
| NAXIS1 | 48 | int | Table width |
| NAXIS2 | 20 | int | Number of wavelength pixels |
Column descriptions:
| Name | Type | Units | Description |
|---|---|---|---|
| LOGLAM | float64 | log(Angstrom) | log(wavelength) |
| ETA | float64 | — | Intrinsic variance of fluctuations |
| VAR_LSS | float64 | — | Mean weight |
| NUM_PIXELS | int32 | — | Number of pixels in the fit |
| VALID_FIT | bool | — | Indicates valid fit |
Mean quasar continuum¶
EXTNAME = CONT
| Header Keyword | Example Value | Type | Comment |
|---|---|---|---|
| NAXIS | 2 | int | Number of array dimensions |
| NAXIS1 | 84 | int | Table width |
| NAXIS2 | 206 | int | Number of rest-frame pixels |
Column descriptions:
| Name | Type | Units | Description |
|---|---|---|---|
| LOGLAM_REST | float64 | log(Angstrom) | Logarithm of rest-frame wavelength |
| MEAN_CONT | float64 | — | Mean quasar continuum |
| WEIGHT | float64 | — | Mean weight |
Extra fit metadata¶
EXTNAME = FIT_METADATA
| Header Keyword | Example Value | Type | Comment |
|---|---|---|---|
| NAXIS | 2 | int | Number of array dimensions |
| NAXIS1 | 43 | int | Table width |
| NAXIS2 | 23168 | int | Number of forests |
Column descriptions:
| Name | Type | Units | Description |
|---|---|---|---|
| LOS_ID | int64 | — | PICCA unique target ID |
| ZERO_POINT | float64 | — | Continuum zero-point parameter |
| SLOPE | float64 | — | Continuum slope parameter |
| CHI2 | float64 | — | Continuum fit \(\chi^2\) |
| NUM_DATAPOINTS | int64 | — | Number of wavelenth pixels |
| ACCEPTED_FIT | bool | — | Fit acceptance |
The file rejection_log.fits.gz contains the rejection reason for each instance of a forest being rejected during the picca delta extraction.
| HDU Number | EXTNAME | Type | Contents |
|---|---|---|---|
| HDU0_ | PRIMARY | PRIMARY | — |
| HDU1_ | REJECTION_LOG | BINTABLE | Rejected forest statistics |
Rejected forest statistics¶
EXTNAME = REJECTION_LOG
| Header Keyword | Example Value | Type | Comment |
|---|---|---|---|
| NAXIS | 2 | int | Number of array dimensions |
| NAXIS1 | 104 | int | Table width |
| NAXIS2 | 24719 | int | Number of rejected forests |
Column descriptions:
| Name | Type | Units | Description |
|---|---|---|---|
| LOS_ID | int64 | — | PICCA unique target ID |
| RA | float64 | degrees | Target Right Ascension (J2000) |
| DEC | float64 | degrees | Target Declination (J2000) |
| Z | float64 | — | Redshift |
| MEANSNR | float64 | — | Mean signal-to-noise ratio |
| TARGETID | int64 | — | Unique identifier for each object observed by DESI |
| NIGHT | char[12] | — | Observation night(s) |
| PETAL | char[12] | — | Observation petal(s) |
| TILE | char[12] | — | Observation tile(s) |
| FOREST_SIZE | int64 | — | Number of pixels in the forest |
| REJECTION_STATUS | char[12] | — | Rejection status of forest |
Contact¶
Contact Sindhu Satyavolu with any questions.