APOGEE Caveats

This page consists of a list of known problems in the DR12 APOGEE data release. Note that these are problems/bugs, not a list of issues or imperfections to be aware of that are intrinsic to the data. For those, see the pages on Using APOGEE spectra, Using ASPCAP stellar parameters, and Using elemental abundances.

Uncertainties given as [X/H] are computed from [X/M] scatter for C, N and α elements

The calibrated abundances are all presented as [X/H], i.e., for C, M and alpha elements, the [M/H] parameter has been added to the raw FERRE output. However, the empirical uncertainties derived from scatter within clusters were measured in the raw [X/M] for these elements.

Character string for target flags missing in visit and visit summary files for four ancillary programs

The associated character strings for four ancillary programs were added to the software pipeline after visit reduction was complete.

APOGEE_RV_MONITOR_IC348
APOGEE_RV_MONITOR_KEPLER
APOGEE_GES_CALIBRATE
APOGEE_BULGE_RV_VERIFY

As a result, stars for these programs will have these character strings in the character target flags tag (TARGFLAGS) for the combined spectra and in the summary file for combined spectra (allStar) but these strings will not be present in the visit spectra files or the summary allVisit file.

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Some targets observed in multiple fields and appear as duplicates

For some overlapping fields, some stars were independently selected as targets in both fields. Since spectra are combined only within fields, these stars appear more than one in the combined spectra and summary tables. To avoid “double use” of these, when then are multiple combined spectra of the same object, the lower S/N observations all have a bit set in the EXTRATARG flag that appears in the summary allStar file and in the CAS table.

Some stars observed in multiple target classes

Some targets may have been selected independently for different programs within different visits to the same field. When we combine spectra, the target flag that we adopt for the combined spectrum is a bitwise OR of all of the target flags of the individual visit spectra. As a result, there are stars constructed from multiple visits for which a target flag bit may be set in the combined spectra, but not in all of the visit spectra that were used to construct it.

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Ancillary target bit not set for two ancillary programs

APOGEE_ANCILLARY bit is not set for APOGEE_KEPLER_SEISMO and APOGEE_KEPLER_HOST targets

Inconsistent IDs

For a few objects, slightly incorrect object/star names were used during the reduction. These names have all been fixed in the final summary files and associated database tables, but if you want to find the individual star spectrum files (e.g., the apStar or aspcapStar files), you will need to know the star name used during the reduction; this is stored in the REDUCTION_ID tag. In future data releases, we hope that all of the correct names will be used consistently throughout.

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