Quantifying BOSS Galaxy Incompleteness With a WISE-Selected Sample


Photo of Benjamin Weiner
Benjamin Weiner
University of Arizona


Spectra of galaxies with a wider range of colors than those selected in the CMASS sample

Finding Targets

An object whose ANCILLARY_TARGET2 value includes one or more of the bitmasks in the following table was targeted for spectroscopy as part of this ancillary target program. See SDSS bitmasks to learn how to use these values to identify objects in this ancillary target program.

Program (bit name) Bit number Target Description Spectra Unique Primary Objects
WISE_COMPLETE 23 Galaxy in the same redshift range as the BOSS CMASS sample, but selected with a more relaxed color cut 10,117 9,163


The BOSS CMASS sample is designed to select red galaxies of high stellar mass (Mstellar > 1011 M). This program (target class WISE_COMPLETE) aimed to explore a broader range of galaxy colors in the CMASS redshift range (0.45 < z < 0.7), using optical-IR cuts by combining SDSS and WISE. In total, 26 plates were observed as part of this ancillary program (plates 6373-6398).

Target Selection

The sample criteria are:

  • 17.5 < i < 19.9
  • (r – W1) > 4.165
  • ifib2 < 21.7 (uncorrected for galactic extinction

Various quality flag cuts were imposed to limit spurious sources. Stars were eliminated using the SDSS morphological classifications for blue objects and a color-color cut in (r – i, r – W1) space for red objects.

A random subsample of 90% of these objects were selected as targets to meet the required target sky density.