Binospec reduced data formats

Binospec reduced data format description

This page describes Binospec reduced data and is largely copied from the Binospec pipeline wiki at bitbucket, to preserve that information if/when bitbucket disables the wiki.

Reduced Data Products

MMT users should be able to download their reduced data directly from the MMT scheduler website. If you have arrived at this page after receiving an email notification that your data is available to download, please note the following: You will have one set of data products for each queue catalog target that was observed. If a target was observed on multiple nights, you will receive multiple sets of reduced data, one per night. Any co-adding across nights must currently be performed by the user on the reduced files. The pipeline routines bino_ob_combine.pro and bino_ob_combine_1d.pro are provided for this purpose.

We provide multiple data products, both 2D and extracted 1D spectra with and without pseudo-flux calibration, as described below. If you choose to run or re-run the pipeline yourself, you will see other intermediate-step output files as well, but the files listed below represent the most useful final data products. Data taken with the Binospec IFU has final data products that are slightly different, see item 5. below.

1. Co-added, sky subtracted, rectified/linearized 2D spectra and their uncertainties (indicated with “err” in the filename) stored in the following multi-extention FITS files:

   Flat fielded in total counts but not flux calibrated

   • obj_counts_slits_lin.fits
   • obj_counts_err_slits_lin.fits

   Corrected for blaze function and flux-calibrated (not accounting for sky or slit losses, flux hitting the detector only)

   • obj_abs_slits_lin.fits
   • obj_abs_err_slits_lin.fits

   Every slit is stored in a separate FITS extension. The fits header for each extension includes wavelength WCS info, as well as SLIT* keywords providing the information about the target and slit geometry. By default we apply a barycentric correction to all wavelength solutions. These files can be displayed using ds9 as follows: ds9 -mecube obj_counts_slits_lin.fits

2. Quick-look versions of the results in counts, with all slits displayed together as they appeared on the slit mask, shifted so that wavelengths are aligned (a line of constant X pixel=constant wavelength). These files have two fits extensions, one for Binospec side A, and one for side B.
   obj_counts_qlook.fits

3. Co-added, sky subtracted, 1D spectra and their uncertainties stored as a multi-extension FITS file, indicated with “extr” in the filename: Flat fielded in total counts but not flux calibrated.
   obj_counts_slits_extr.fits
   Corrected for blaze function and relatively flux calibrated (throughput-corrected).
   obj_abs_slits_extr.fits

   These files contain one spectrum per row in the 1st FITS extension. The spectra are aligned in the wavelength scale and the corresponding WCS coordinates are provided in the header. The 2nd FITS extension contains the uncertainty for each spectrum, the 3rd contains the sky spectrum that was subtracted, and the 4th and 5th extensions contain fits binary tables with target information from the mask design (for mask side A and B, respectively.)

4. 1D spectra split into individual fits files, one spectrum per file. They are distributed bundled up into tar files, whose contents are the 1D files with file names derived from object names submitted with the mask design. These files have fits header keywords that improve compatibility with IRAF.
   • obj_counts_1D.tar
   • obj_abs_1D.tar

5. Binospec IFU has two primary data products. First, the individual lenslets are reduced and the extracted spectra are stored stacked as two large ‘psedo-slits’ in obj-sky_fib_lin.fits, a file with strcture very similar to ‘obj_counts_slits_lin.fits’ for a longslit observation: that is 2 fits extensions containing the spectra that fell on the side A and side B CCDs, followed by a fits binary table containing info on the mapping of individual fiber traces to their x, y positions in the lenslet array (and on the sky). This is the file that should be used for most scientific measurements, as it is minimally resampled. However, for visualization purposes, we also provide obj-sky_cube_lin.fits which is the 3D data cube formed from all the lenslets assembled into an image. Since the lenslets are hexagonal, we drizzle onto a slightly oversampled regular grid, which does introduce some artifacts (and why we reccommend using the _fib_lin.fits files for science.)

Every FITS file produced by the pipeline contains the SOFTWARE keyword in the primary HDU that provides the pipeline version used to reduce this dataset. Should you have any question/feedback related to the data reduction, please include the pipeline version in the correspondance.