APOGEE’s target selection algorithm includes many red-clump (RC) stars in the APOGEE sample. A new method for identifying red-clump stars from spectrophotometric data and its application to the APOGEE data was presented in Bovy et al. (2014). This technique creates a very pure sample of red-clump stars with minimal contamination from red-giant-branch, secondary-red-clump, and asymptotic-giant-branch stars. The narrowness of the RC locus in color-metallicity-luminosity space allows distances to the stars to be assigned with an accuracy of 5%-10%. The purity is estimated to be about 95%.

The DR13 catalog is selected based on the more accurate set of spectroscopic parameters from the overall DR13 APOGEE release and therefore suffers from less contamination, leading to a slight decrease in the number of RC stars in the DR13 catalog compared to the DR12 catalog. The DR13 catalog contains 19,291 stars and is available on the SAS; its contents are described in the datamodel.

The older DR11 and DR12 catalog versions are still available. For DR11 (Niveder et al. 2014), containing 10,341 objects, the catalog is available from the SAS here, with its datamodel available here. The DR12 catalogue (Bovy et al. 2014), containing 19,937 objects, is available from the SAS here, with its datamodel available here.

Section 4 of Bovy et al. (2014) described how to correct for observational biases due to the APOGEE target selection (for the whole (J-Ks)0 > 0.5 sample, not just the red-clump sample). Specifically, these are the biases due to the incomplete sampling of the available targets with (J-Ks)0 > 0.5 as a function of position on the sky and magnitude. Tools to correct for these biases are included in the apogee python package and extensive documentation on how to use this package is given on the package webpage. This selection-function code has been updated for DR13 (from the DR11 version described in the paper).

Section 5 of Bovy et al. (2014) discussed astrophysical biases due to the red-clump selection. Specifically, they investigated the biases in recovering the underlying age and metallicity distribution by only selecting red-clump stars. The RC selection preferentially select stars with ages between 1 and 4 Gyr and with metallicities > -0.9. Please consult section 5 of the paper above for full details. The apogee python package also has tools for working with the astrophysical biases.

The SPIDERS Tier-0 target catalogs (Clerc et al., submitted ; Dwelly et al. in prep.), i.e. AGN and galaxy clusters candidates, were obtained by matching X-ray information from the ROSAT All-Sky Survey (RASS) and from XMM-Newton to multi-band photometric data.

The SPIDERS AGN target catalogs contain 9,028 candidate targets from RASS and 819 from XMMSL. They enclose information on the X-ray sources, including flux measurements, and a quantitative measure of the reliability of the association to optical and AllWISE data. The counterparts to X-ray extended sources (galaxy clusters) were identified using a red-sequence finding algorithm adapted from RedMapper (Rykoff et al. 2014). The target list contains galaxies likely to belong to a galaxy cluster, as indicated by their color, distance to the center and luminosity. The SPIDERS Galaxy Cluster target list contains 94,883 and 3,839 objects for RASS and XMM respectively. We additionally provide targeting catalogs for the SEQUELS area, similarly constructed although differing in their association and selection methods.

Details on target selection are on this page: SPIDERS target selection. The catalogs are available on the SAS. The files in the catalogs are described in the data model page.

We provide the catalogue of X-ray detected galaxy clusters spectroscopically confirmed using SEQUELS-DR12 SPIDERS spectroscopic data (Clerc et al. submitted). Galaxy clusters were identified through the emission of their hot baryonic component as X-ray extended sources from the ROSAT All-Sky Survey (RASS). The optical counterparts were found by optimally searching photometric data for the existence of a red-sequence formed by their member galaxies. Spectroscopic redshifts obtained by SPIDERS (in the SEQUELS programme) provide definitive confirmation of the clustered nature of these objects and their redshift (up to z~0.6). We assigned cluster membership combining an algorithm and visual validation of individual objects. The gas properties derived from X-ray observations (luminosity, temperature, R₂₀₀) are derived using precise cluster redshifts (Δ_z ~ 0.001). We compute galaxy cluster velocity dispersions using several methods adapted to the low number of spectroscopic members per system (of the order 15-40) and we show that their values correlate with cluster X-ray luminosities, within expectations.

The catalogs are available on the SAS. The files in the catalogs are described in the data model page.