The QUEST-La Silla AGN Variability Survey

Abstract

We present the characterization and initial results from the QUEST-La Silla AGN variability survey. This is an effort to obtain well sampled optical light curves in extragalactic fields with unique multi-wavelength observations. We present photometry obtained from 2010 to 2012 in the XMM-COSMOS field, which was observed over 150 nights using the QUEST camera on the ESO-Schmidt telescope. The survey uses a broadband filter, the $Q$-band, similar to the union of the $g$ and the $r$ filters, achieving an intrinsic photometric dispersion of $0.05$ mag, and a systematic error of $0.05$ mag in the zero-point. Since some detectors of the camera show significant non-linearity, we use a linear correlation to fit the zero-points as a function of the instrumental magnitudes, thus obtaining a good correction to the non-linear behavior of these detectors. We obtain good photometry to an equivalent limiting magnitude of $r\sim 20.5$. Studying the optical variability of X-ray detected sources in the XMM-COSMOS field, we find that the survey is $\sim 75-80$% complete to magnitudes $r\sim 20$, and $\sim 67$% complete to a magnitude $r\sim 21$. The determination and parameterization of the structure function (${SF}_{norm}(\tau )=A{\tau }^{\gamma }$) of the variable sources shows that most BL AGN are characterized by $A>0.1$ and $\gamma >0.025$. It is further shown that variable NL AGN and GAL sources occupying the same parameter space in $A$ and $\gamma$ are very likely to correspond to obscured or low luminosity AGN. Our samples are, however, small, and we expect to revisit these results using larger samples with longer light curves obtained as part of our ongoing survey.

Accepted for publication in ApJ

References in corpus (20)

• COSMOS Photometric Redshifts with 30-bands for 2-deg2
• zCOSMOS: A Large VLT/VIMOS redshift survey covering 0 < z < 3 in the COSMOS field
• UltraVISTA: a new ultra-deep near-infrared survey in COSMOS
• Modeling the Time Variability of SDSS Stripe 82 Quasars as a Damped Random Walk
• The Sloan Digital Sky Survey-II Supernova Survey: Technical Summary
• The Chandra COSMOS Survey, I: Overview and Point Source Catalog
• Absorption Properties and Evolution of Active Galactic Nuclei
• SDSS Standard Star Catalog for Stripe 82: the Dawn of Industrial 1% Optical Photometry
• On the variability of quasars: a link between Eddington ratio and optical variability?
• Correlated X-ray/Optical Variability in the Quasar MR2251-178
• Magellan Spectroscopy of AGN Candidates in the COSMOS Field
• The XMM-Newton wide-field survey in the COSMOS field. IV: X-ray spectral properties of Active Galactic Nuclei
• Quasar Selection Based on Photometric Variability
• The dependence of quasar variability on black hole mass
• Quasars in the COSMOS Field
• High-frequency X-ray variability as a mass estimator of stellar and supermassive black holes
• Measuring Quasar Variability with Pan-STARRS1 and SDSS
• Discovery of 5000 Active Galactic Nuclei behind the Magellanic Clouds
• The QUEST Large Area CCD Camera
• Exploring the Variable Sky with the Sloan Digital Sky Survey

Cited by in corpus (20)

• Optical variability of AGN in the PTF/iPTF survey
• Pan-STARRS1 variability of XMM-COSMOS AGN. II. Physical correlations and power spectrum analysis
• Identifying AGNs in low-mass galaxies via long-term optical variability
• Ensemble X-ray variability of Active Galactic Nuclei. II. Excess Variance and updated Structure Function
• The QUEST-La Silla AGN variability survey: connection between AGN variability and black hole physical properties
• Early observations of the nearby type Ia supernova SN 2015F
• Near Infrared Variability of obscured and unobscured X-ray selected AGN in the COSMOS field
• Quasar Variability in the Mid-Infrared
• Dwarf AGNs from Optical Variability for the Origins of Seeds (DAVOS): Insights from the Dark Energy Survey Deep Fields
• The QUEST-La Silla AGN Variability Survey: selection of AGN candidates through optical variability
• A random forest-based selection of optically variable AGN in the VST-COSMOS field
• The High Cadence Transient Survey (HITS): Compilation and characterization of light-curve catalogs
• Mid-infrared Variability of Low-redshift Active Galactic Nuclei : Constraints on a Hot Dust Component with a Variable Covering Factor
• Extending the variability selection of active galactic nuclei in the W-CDF-S and SERVS/SWIRE region
• New quasars behind the Magellanic Clouds. Spectroscopic confirmation of near-infrared selected candidates
• Modeling the Variability of Active Galactic Nuclei by Infinite Mixture of Ornstein-Uhlenbeck(OU) Processes
• Ensemble power spectral density of SDSS quasars in UV/optical bands
• Observational nonstationarity of AGN variability: The only way to go is down!
• Photometric variability in star-forming galaxies as evidence for low-mass AGN and a precursor to quenching
• Seeing through the dust: Unraveling near-infrared variability in type 2 active galactic nuclei