Data model: BOSS Target Files

Overview

General description: Boss target files contain targeting info for the galaxies, quasars, and standards. The basic bosstarget files match one-to-one with the data sweep (calibObj) from which they were generated. Thus there is one target file per RUN/CAMCOL for the given set of RERUNs. These files at a minimum contain the run/rerun/camcol/field/id of each object and the boss_target flag bits, and a separate HDU containing status information about the processing. There are also collated files, which are reduced from the target files based on target flags and other information and collated with the full information from the calibObj from which they were generated.

Naming convention:

$BOSS_TARGET/$TARGET_RUN/bosstarget-$TARGET_TYPE-$RUN-$CAMCOL-$RERUN-$TARGET_RUN.fits
$BOSS_TARGET/$TARGET_RUN/bosstarget-$TARGET_TYPE-$TARGET_RUN-collate.fits
$BOSS_TARGET/$TARGET_RUN/bosstarget-$TARGET_TYPE-$TARGET_RUN-collate-$CHUNK.fits

for TARGET_TYPE in "lrg" "qso" "std". TARGET_RUN is generally a date string with some modifications, e.g. 2009-07-15c where c means "commissioning". The format for $RUN, $RERUN, $CAMCOL is the usual I6, string, and I1 respectively.

As shown above, the directory may contain intermediate "chunk" collated files written out during the parallel processing. The $CHUNK variable has format I3. These files are not critical and may disappear.

Relevant IDL classes and methods:

boss/bosstarget/pro/bosstarget__define.pro
- The ::process_runs method runs the targeting code on a set of data sweeps and writes the target files.
- The ::verify method can be used to verify the results of the ::process_runs method. All usable target runs must pass the verification process.
- The ::read_collated method reads the collated files.
- The ::read method reads the target files based on run/rerun/camcol.
- The ::gather method and ::gather2file methods can be used to aggregate subsets.
- There are a set of ::*partial* deal with the data in chunks for parallel processing.
boss/bosstarget/pro/bosstarget_$TARGET_TYPE__define.pro
for TARGET_TYPE in "lrg" "qso" "std"
- The ::select method selects targets and sets the relevent boss_target bits.

Basic Target File Data Model

Header Keywords

There are no required header keywords. The details of the processing are instead contained in the first binary table hdu.

First HDU: The Status Structure

This is the first binary table hdu (1 for zero-offset extension counting). This hdu contains details and status about the processing and is generally referred to as the "status structure".

Required Fields

TARGET_TYPE (string): "qso" "std" or "lrg"
TARGET_RUN (string): e.g. "2009-07-15c"
BOSSTARGET_V (string): The version of the bosstarget code used.
PHOTOOP_V (string): Version of the photoop code used.
IDLUTILS_V (string): Version of idlutils used.
PHOTO_SWEEP (string): basename of $PHOTO_SWEEP
PHOTO_RESOLVE (string): basename of $PHOTO_RESOLVE
PHOTO_CALIB (string): basename of PHOTO_CALIB
RUN (int32): SDSS run number
RERUN (string): SDSS processing rerun
CAMCOL (int32): SDSS camera column number
OUTPUT_FILE (string): basename of this file.
DATE (string): e.g. "Wed Jul 29 11:01:18 2009".
NOBJ (int32): number of objects in calibObj file as sent to the target selection code.
NRES (int32): number of objects returned from target selection code. Should equal NOBJ
EXTRA_LOGIC (string): A string containing any extra logic that was applied to the target selection via the extra_logic= keyword.
FLAGS (int32): Should be zero for successful processing.

Second HDU: Target Selection Information

In principle only the run, rerun, camcol, field, id, and boss_targetN are absolutely required. This is because these files are designed to be collated with the original calibObj files when generating a target list.

Required Fields

RUN (int32): SDSS run number
RERUN (string): SDSS processing rerun
CAMCOL (int32): SDSS camera column number
FIELD (int32): Field id within RUN/CAMCOL
ID (int32): id within FIELD
BOSS_TARGET1 (int64): boss_target selection flags.

In practice there can be many more fields in the output file, especially for the QSOs. See the details listed below.

Specifics for Different Target Types

Quasars

The qso selection is performed on the "star" calibObj files.

Galaxy

The galaxy selection is performed on the "gal" calibObj files.

Standards

The standards selection is performed on the "star" calibObj files.

Collated Target File Data Model

Header Keywords

There are no required header keywords. The details of the processing are instead contained in the first binary table hdu.

First HDU: The Collated Status Structure

This is the first binary table hdu (1 for zero-offset extension counting). This hdu contains details and status about the processing and is generally referred to as the "status structure".

Required Fields

TARGET_TYPE (string): "qso" "std" or "lrg"
TARGET_RUN (string): e.g. "2009-07-15c"
BOSSTARGET_V (string): The version of the bosstarget code used.
PHOTOOP_V (string): Version of the photoop code used.
IDLUTILS_V (string): Version of idlutils used.
PHOTO_SWEEP (string): basename of $PHOTO_SWEEP
PHOTO_RESOLVE (string): basename of $PHOTO_RESOLVE
PHOTO_CALIB (string): basename of PHOTO_CALIB

Second HDU: Target Selection Information and Full calibObj Data

In principle only the run, rerun, camcol, field, id, boss_target selection flags, RA, DEC, and fiber magnitudes are absolutely required since these are required by the tiling. In practice the union of the outputs from the basic target files with the entire set of information from the calibObj files is present in the collated files. As explained above, the different target types use different calibObj types ('star' or 'gal') as their basis. Plese see the documentation for the calibObj files for more info on what fields are available.

Required Fields

RUN (int32): SDSS run number
RERUN (string): SDSS processing rerun
CAMCOL (int32): SDSS camera column number
FIELD (int32): Field id within RUN/CAMCOL
ID (int32): id within FIELD
RA (float64): Right ascension in degrees J2000
DEC (float64): Declination in degrees J2000
FIBER2FLUX[5] (float32): Fiber flux in each band.
FIBER2FLUX_IVAR[5] (float32): Inverse variance of fiber flux in each band.
BOSS_TARGET1 (int64): boss_target selection flags.