The VMC Survey - VI. Quasars behind the Magellanic system

Abstract

The number and spatial distribution of confirmed quasi-stellar objects (QSOs) behind the Magellanic system is limited. This undermines their use as astrometric reference objects for different types of studies. We have searched for criteria to identify candidate QSOs using observations from the VISTA survey of the Magellanic Clouds system (VMC) that provides photometry in the YJKs bands and 12 epochs in the Ks band. The (Y-J) versus (J-Ks) diagram has been used to distinguish QSO candidates from Milky Way stars and stars of the Magellanic Clouds. Then, the slope of variation in the Ks band has been used to identify a sample of high confidence candidates. These criteria were developed based on the properties of 117 known QSOs presently observed by the VMC survey. VMC YJKs magnitudes and Ks light-curves of known QSOs behind the Magellanic system are presented. About 75% of them show a slope of variation in Ks>10^-4 mag/day and the shape of the light-curve is in general irregular and without any clear periodicity. The number of QSO candidates found in tiles including the South Ecliptic Pole and the 30 Doradus regions is 22 and 26, respectively, with a ~20% contamination by young stellar objects, planetary nebulae, stars and normal galaxies. By extrapolating the number of QSO candidates to the entire VMC survey area we expect to find about 1200 QSOs behind the LMC, 400 behind the SMC, 200 behind the Bridge and 30 behind the Stream areas, but not all will be suitable for astrometry. Further, the Ks band light-curves can help support investigations of the mechanism responsible for the variations.

17 pages, 15 figures, replaced with accepted version by Astronomy & Astrophysics

References in corpus (26)

• The UKIRT Infrared Deep Sky Survey (UKIDSS)
• The VMC Survey - I. Strategy and First Data
• CGRaBS: An All-Sky Survey of Gamma-Ray Blazar Candidates
• New Optical Reddening Maps of the Large and Small Magellanic Clouds
• A very cool brown dwarf in UKIDSS DR1
• The SAGE-Spec Spitzer Legacy program: The life-cycle of dust and gas in the Large Magellanic Cloud. Point source classification I
• Quasar Selection Based on Photometric Variability
• Luminous K-band Selected Quasars from UKIDSS
• QSO Selection Algorithm Using Time Variability and Machine Learning: Selection of 1,620 QSO Candidates from MACHO LMC Database
• The dependence of quasar variability on black hole mass
• Near-Infrared Reverberation by Dusty Clumpy Tori in Active Galactic Nuclei
• Variation of Inner Radius of Dust Torus in NGC4151
• Probabilistic selection of high-redshift quasars
• Detailed maps of interstellar clouds in front of omega Centauri: Small-scale structures in the Galactic Disc-Halo interface
• Discovery of 5000 Active Galactic Nuclei behind the Magellanic Clouds
• The Magellanic Quasars Survey. II. Confirmation of 144 New Active Galactic Nuclei Behind the Southern Edge of the Large Magellanic Cloud
• The Magellanic Quasars Survey. I. Doubling the Number of Known AGNs Behind the Small Magellanic Cloud
• A Refined QSO Selection Method Using Diagnostics Tests: 663 QSO Candidates in the LMC
• Multiple Regression Analysis of the Variable Component in the Near-Infrared Region for Type 1 AGN MCG+08-11-011
• Using quasars as standard clocks for measuring cosmological redshift
• The VMC Survey. II. A multi-wavelength study of LMC planetary nebulae and their mimics
• The Spitzer discovery of a galaxy with infrared emission solely due to AGN activity
• Selection constraints on high redshift quasar searches in the VISTA kilo-degree infrared galaxy survey
• Ensemble Variability of Near-Infrared-Selected Active Galactic Nuclei
• Improved prospects for the detection of new Large Magellanic Cloud planetary nebulae
• Optical monitoring of the z=4.40 quasar Q 2203+292

Cited by in corpus (19)

• The SAGE-Spec Spitzer Legacy program: The life-cycle of dust and gas in the Large Magellanic Cloud. Point source classification I
• Optically Visible Post-AGB Stars, Post-RGB Stars and Young Stellar Objects in the Large Magellanic Cloud
• The SAGE-Spec Spitzer Legacy program: The life-cycle of dust and gas in the Large Magellanic Cloud. Point source classification III
• The Structure of the Circumgalactic Medium of Galaxies: Cool Accretion Inflow Around NGC 1097
• The VMC Survey - X. Cepheids, RR Lyrae stars and binaries as probes of the Magellanic System's structure
• The First Year of S-CUBED: The Swift Small Magellanic Cloud Survey
• The VVV Templates Project. Towards an Automated Classification of VVV Light-Curves. I. Building a database of stellar variability in the near-infrared
• Extreme Infrared Variables from UKIDSS - I. A Concentration in Star Forming Regions
• The VMC survey - XVII. The proper motion of the Small Magellanic Cloud and of the Milky Way globular cluster 47 Tucanae
• The VMC survey -IX. Pilot study of the proper motion of stellar populations in the LMC from 2MASS and VISTA data
• New quasars behind the Magellanic Clouds. Spectroscopic confirmation of near-infrared selected candidates
• Identification of AGN in the XMM-Newton X-ray survey of the SMC
• The VMC Survey -- XLIX. Discovery of a population of quasars dominated by nuclear dust emission behind the Magellanic Clouds
• The VMC survey
• The intrinsic reddening of the Magellanic Clouds as traced by background galaxies -- III. The Large Magellanic Cloud
• The VMC survey -- XXXVI. Young stellar variability in the Large Magellanic Cloud
• Stellar Variability in a Forming Massive Star Cluster
• The VMC survey -- LIII. Data release #7. Complete survey data and data from additional programmes
• Quasars behind the disk of M31 galaxy