NOAO >   Observing Info >   Approved Programs >   2017A-0357

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Program Information for 2017A-0357


PI: Xin Liu, U. of Illinois Urbana-Champaign, xinliuxl@illinois.edu
Address: Department of Astronomy, 103 Astronomy Building, 1002 West Green Street, Urbana, IL, 61801 USA

CoI: Yuan Liu, Institute of High Energy Physics
CoI: Yue Shen, U. of Illinois Urbana-Champaign

Title: Spectroscopic Identification for Six Offset/Dual AGN Candidates at z~2 Selected by Centroid Shifts in Multi-epoch Quasar Images

Abstract: The occurrence rate of offset/dual AGNs is important for understanding the merging history of galaxies and AGN triggering. However, efficient methods are still lacking for selecting offset/dual AGN candidates in particular at high redshifts. The non-synchronous variations and/or different colors in offset and/or dual AGN systems will produce centroid shifts in one band and/or between two bands. Since the astrometric error is normally much smaller than the angular resolution, it is possible to detect such shifts using multi-epoch images even for unresolved systems. We propose Gemini/GMOS-S spectroscopy for 6 candidate offset/dual AGNs at z~2 selected by the centroid shift techniques applied to quasar images from the SDSS Stripe 82. These targets show significant centroid shifts consistent with being induced by a nearby companion close to the quasar, whose physical association needs to be confirmed with spatially resolved spectroscopy. The result will constrain for the first time the occurrence rate of offset/dual AGNs at z~2 with projected physical separations of ~10-15 kpc. It will serve as a proof of concept for the centroid shift techniques, paving the way for efficient applications with large-scale time-domain photometric surveys such as the LSST.

Program Type: Standard/Extragalactic

Scheduled Nights:
Run 1 (2017A):  GEM-SQ/GMOSS -- 9hrs band 3 (GS-2017A-Q-73)


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