Data Reduction Outputs

Assuming you ran DBSP_DRP with dbsp_reduce -r $RAW_PATH -d $OUTPUT_PATH, then in the $OUTPUT_PATH/Science directory you will find:

PypeIt 2D Spectrum files spec2d_redNNNN-target_DBSPr_obstimestamp.fits described in more detail here. Briefly, these files hold flat-fielded 2D spectral images, as well as sky, noise, object, wavelength, and bad pixel mask images. These files can be visually inspected using the command pypeit_show_2dspec SPEC2D_FILE.

PypeIt 1D Spectrum files spec1d_redNNNN-target_DBSPr_obstimstamp.fits described in more detail here. Briefly, these files hold 1D spectra for each object that was traced and extracted from the raw frame. Each object’s spectrum is stored in a separate extension of the FITS file, and the extension names are of the form SPATNNNN-SLITMMMM-DET01 where the SPAT number describes the spatial pixel coordinate of the object and the SLIT number is only useful for spectrographs with multiple slits (and the DET number is only useful for spectrographs with multiple detectors for the same arm). These files can be visually inspected using the command pypeit_show_1dspec --exten N SPEC1D_FILE to view extension N of the file.

PypeIt 1D Coadd files redNNNN-redNNNN_target_SPATNNNN.fits described in more detail here. These files exist to separate out multiple objects on the same frame into their own file, and to coadd consecutive exposures of the same frame. These files can be visually inspected using the command lt_xspec COADD_FILE. The filename contains the first and last raw data file and the medial spatial pixel coordinate of the object. This was done to make the coadd filename of constant length, instead of scaling with the number of coadded frames, since all operating systems/file systems have maximum allowed filename lengths.

Telluric-corrected 1D Coadd files have _tellcorr appended to the base filename of the coadd file.

In the directory $OUTPUT_PATH/spliced are the spliced final data products. The final data product of DBSP_DRP is a FITS file named target_char.fits with structure described below, where char is a one-letter designation of which object along the slit it is.

table

Extension Number	Name	Header	Data
0	PRIMARY	Version info about DBSP_DRP, PypeIt, NumPy and Astropy	None
1	RED0031	Header from raw red side FITS file	Fluxed (not telluric-corrected) red side spectrum
2	RED0032	Header from raw red side FITS file	Fluxed (not telluric-corrected) red side spectrum
3	BLUE0032	Header from raw blue side FITS file	Fluxed blue side spectrum
4	BLUE0032	Header from raw blue side FITS file	Fluxed blue side spectrum
5	RED	Header from raw red side FITS file	Fluxed (and telluric-corrected) red side spectrum
6	BLUE	Header from raw blue side FITS file	Fluxed blue side spectrum
7	SPLICED	Empty	Final spliced spectrum

The header on the 0th extension also contains cards named B_COADD and R_COADD which contain the filename of the blue and red coadd files, respectively, that were spliced together. This is useful for determining which traces a particular final output file corresponds to. The 0th header also contains an INTERP_GAPS cards, noting whether or not detector gaps were interpolated over during splicing. If the splicing has been manually adjusted (see Manual Splicing for more details) then a RED_MULT card will also be present, recording the factor multiplied into the red coadd spectrum before splicing with the blue coadd.

If n red side files were coadded and m blue side files were coadded, then extensions 1 through n would contain the red side raw headers and fluxed spectrum from each individual file, extensions 1+*n* through 1+*n*+*m* would contain the blue side raw headers and fluxed spectra from each individual file, and the last 3 extensions are the red coadd, blue coadd, and final spliced spectrum.

If an object was not observed in the blue (red) then there will be no raw blue (red) frames, and the BLUE (RED) extension would still exist, but contain no data.

Each of the data tables contain columns for wave, flux, and sigma, with wavelength in Angstroms and both flux and sigma in units of 10^-17erg/s/cm²/Ang.