Double-lobed Radio Quasars


Photo of Amy Kimball
Amy Kimball


Spectra of point-source objects near the midpoint of a double-lobed radio quasar in FIRST

Finding Targets

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 Number of Fibers Number of Unique Primary Objects
RADIO_2LOBE_QSO 5 Object near the midpoint of a double-lobed object identified in FIRST 1,196 1,133


Objects identified as optical point sources near the midpoint of pairs of FIRST radio sources are observed as potential double-lobed radio quasars. Such quasars are important for studying quasar evolution and interactions of radio jets with their local environment.

Target Selection

Candidates were selected by identifying FIRST pairs with a separation less than 60″ and no SDSS optical counterpart within 2″ of either source. SDSS point sources located within a search radius that ranges between 2″ and 5.3″ (depending on the separation distance of the FIRST pair) from the midpoint are targeted.

FIRST pairs with a flux ratio > 10 are rejected, because true double-lobed sources are unlikely to have a high ratio of lobe-lobe flux density. The final catalog includes objects not spectroscopically observed with SDSS, not targeted in the main BOSS sample, and with 17.8 < i < 21.6 (Galactic extinction-corrected).