Groups of igmspec

This document describes the data groups of igmspec.

List of Surveys

Below is the list of data groups included in igmspec v03:

Each document provides the survey reference and additional details on the spectra and associated meta data.

Here is the list of data groups in v02 that are not included in v03 because they are superseded by v03:


Each group included in igmspec is composed of two components:

  1. A Table of meta data
  2. A numpy data array containing the spectra

Meta Data

Each group has its own unique set of meta data describing the data products. The following keys are required for inclusion in igmspec:

Key Type Description
IGM_ID int Unique igmspec identifier
zem_GROUP float Emission redshift of background source given by the survey
RA_GROUP float Right Ascension (deg) given by the survey
DEC_GROUP float Declination (deg) given by the survey
EPOCH float Coordinate epoch (only 2000 in igmspec v1.0)
DATE-OBS str Date observed (YYYY-MM-DD)
R float Instrument resolution, \(\lambda/\Delta\lambda\) (FWHM)
WV_MIN float Minimum wavelength of the spectrum
WV_MAX float Maximum wavelength of the spectrum
NPIX int Number of pixels in the spectrum; may include null values
GROUP_ID int Unique identifier for the group [not well implemented yet]
SPEC_FILE str Spectrum file name
INSTR str Instrument file name (see instr-and-disp for definitions)
DISPERSER str Disperser name (see instr-and-disp for definitions)
TELESCOPE str Telescope name (see Telescopes below for definitions)

Additional meta data may be provided for individual surveys.

Instruments and Dispersers

The complete list of instruments and associated dispersers that may be used in igmspec are provided in the specdb documentation.


Similarly, the list of telescopes that may be used in igmspec are provided in the specdb documentation.

Spectral Data

The spectra in igmspec are written as a numpy masked array with three required columns and one optional:

Key Type Description
wave float64 Wavelength array; default is Angstroms
flux float32 Flux array; default is unitless
sig float32 Error array; same units as flux
co (optional) float32 Continuum array; same units as flux

The software included with specdb read these data into a XSpectrum1D object in the linetools software repository.