Variability-selected Quasars at 1 < z < 4 to g = 22.5
|Institute of Research into the Fundamental Laws of the Universe|
Spectra of quasars in SDSS stripe 82, selected by color and variability
An object whose
ANCILLARY_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.
|Program (bit name)||Bit number||Target Description||Spectra||Unique Primary Objects|
|QSO_VAR_LF||27||Candidate quasar in stripe 82, selected by color and variability||2,400||2,328|
The target flag
QSO_VAR_LF labels a target class designed for studies of the quasar luminosity function to g < 22.5. The sample is located in Stripe 82 at 36° < α < 42° where multi-epoch SDSS photometry is available, thus enabling a variability selection with the neural network presented in Palanque-Delabrouille et al. (2011).
Targets with pointlike morphology that passed a loose variability criterion were selected (neural network threshold of 0.5, where 1/0 indicates a quasar-like/stellar-like light curve). Extended sources which satised the color selection c3 < 0.6 – 0.33c1, where c1 and c3 are linear combinations of SDSS ugriz as defined in Fan (1999), were targeted if they passed a tighter variability criterion (threshold of 0.9).
Note that targets previously spectroscopically identified as quasars were not included in the sample, and therefore do not have the
QSO_VAR_LF bit set, even if they pass the selection criteria for this program.
Fan, X. 1999, AJ, 117, 2528
Palanque-Delabrouille, N., et al. 2011, A&A, 530, 122