BOSS Ancillary Targets

The number density of BOSS's galaxy and quasar targets is not uniform on the sky, and in regions of lower-than-average target density, not all the 1,000 fibers on a plate will be assigned to these core target categories. With this in mind, we solicited proposals within the BOSS collaboration for relatively small (a few hundred to a few thousand fibers) programs to use spare fibers when available. Twenty-five different programs are included in DR9; these ancillary targets together make up 3.5 percent of all DR9 spectra.

Spectra for ancillary targets are available in the same manner as any other SDSS spectra: individually through the DR9 SkyServer Navigate and Explore tools, and collectively through SkyServer search tools, the CasJobs batch interface, or the Science Archive Server Advanced Search.

Ancillary Target Flags

For all SDSS-III spectroscopic data, information about how that object was targeted for spectroscopy is included in the object's Target Flags. Information about whether a target was selected for one or more ancillary target programs is included in the flags ANCILLARY_TARGET1 and ANCILLARY_TARGET2. (These parameters, like all SDSS flag data, are stored as bitmasks. For more information on how to work with such data, see the description of SDSS-III bitmasks).

Ancillary Target Selection

This page describes how to use SDSS-III ancillary targets in general; the pages linked from the list below describe how targets were selected for specific ancillary targeting programs.

BOSS's ancillary target programs were intended to support studies that require fairly large samples over large regions of sky, making them difficult to complete in conventional observations at shared facilities. Thus, the BOSS ancillary target programs provide opportunities to pursue studies that would be difficult to accomplish in other ways.

Ancillary targets were requested in two calls for proposals made to the SDSS-III collaboration: one in 2009 and one in 2010. Ancillary targets were given a lower priority for target selection than the primary science drivers of BOSS; therefore, sample selection for the ancillary target programs is often not complete.

Ancillary targeting programs fall into two categories: programs that selected targets from the repeated/stacked imaging of SDSS Stripe 82, and those selected from the rest of SDSS imaging data. BOSS's spectroscopic observations of the Stripe 82 coverage area are now complete, so the complete spectroscopic dataset for those ancillary targets in Stripe 82 is being released as part of Data Release 9. Observations of the remaining ancillary targeting programs will continue through the end of the survey; DR9 includes the first part of these data. Data from additional ancillary programs will likely appear in future data releases.

Ancillary Science Programs in Stripe 82

The following ancillary target programs are now complete. Complete data for these ancillary targets is being released as part of Data Release 9.

Ancillary Science Programs in the Full BOSS Survey Area

Spectroscopic observations in the following ancillary target programs have not yet been completed. In each of these ancillary target programs, data for a subset of targets is part of DR9. Future data releases will include more targets from these ancillary target programs.

The DR9 documentation includes an index of the values of ANCILLARY_TARGET1 and ANCILLARY_TARGET2 that correspond to each ancillary target program.