MIR-Discovered Open Clusters
Spectra for candidate cluster members associated with newly discovered or unstudied open clusters in the outer Milky Way disk
An object whose
APOGEE_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.
|APOGEE_TARGET2 bit name||Bit||Target Description|
|APOGEE_MIRCLUSTER_STAR||17||MIR-detected candidate cluster member|
While not deviating significantly in essence from the open cluster target selection algorithm and goals of the main APOGEE sample, described in Zasowski et al. (2013a; §7.2), this ancillary program was granted dedicated fibers because its proposed targets include one cluster discovered by the ancillary team (Zasowski et al., 2013b). The other clusters that were included had been previously known, but either no follow-up study had been made to determine the clusters’ basic parameters, or existing studies had produced conflicting results.
|rachael.l.beaton -at- gmail.com|
|Johns Hopkins University|
|gail.zasowski -at- gmail.com|
Joleen Carlberg, Guillermo Damke, Steven R. Majewski
Target Selection Details
The clusters for this program were identified by visual inspection of Spitzer-IRAC mid-infrared imaging (Zasowski et al. 2013b), of which a subset were selected for follow-up spectroscopy based on both the lack of existing information and overlap with already-planned APOGEE fields in the outer disk. Candidate member stars for each cluster were isolated in the 2MASS point source catalog by application of a RJCE reddening filter (Majewski et al. 2011) and compared to the best-fit theoretical isochrone (Girardi et al. 2002). Targets were selected for APOGEE spectroscopy based on their relative position in the NIR CMD and the APOGEE fiber collision radius, with care given to balancing the needs of high likelihood candidates and reasonable sample size for these relatively compact open clusters clusters. In addition to their selection based on reddening and location in the CMD, all of the approximately 13 targets per cluster were constrained to have photometric uncertainties in J,H, Ks, and [4.5] of at most 0.1 mag. The final cluster list for this program includes FSR 0494 and FSR 0665 (Froebrich et al. 2007), Czernik 20 (Czernik 1966), NGC 1857 (Cuffey & Shapley 1937), and GLMG360-90 and GLMG360-105 (Zasowski et al. 2013b).
Cuffey, J., & Shapley, H. 1937, AnHar, 105, 403
Czernik, M. 1966, AcA, 16, 93
Froebrich, D., et al. 2007, MNRAS, 374, 399
Girardi, L., et al. 2002, A&A, 391, 195
Majewski, S. R., Zasowski, G., & Nidever, D. L. 2011, ApJ, 739, 25
Zasowski G., et al. 2013a, AJ, 146, 81
Zasowski G., Beaton, R. L., et al. 2013b AJ, 146, 64