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While the reverberation mapping technique is the best available method for measuring black hole mass in active galactic nuclei (AGN) beyond the local volume, this method has been mainly applied to relatively low-to-moderate luminosity AGNs at low redshift. We present the strategy of the Seoul National University AGN Monitoring Project, which aims at measuring the time delay of the \Hb\ line emission with respect to AGN continuum, using a sample of relatively high luminosity AGNs out to z $\sim$0.5. We present simulated cross correlation results based on a number of mock light curves, in order to optimally determine monitoring duration and cadence. We describe our campaign strategy based on the simulation results and the availability of observing facilities. We present the sample selection, and the properties of the selected 100 AGNs, including the optical luminosity, expected time lag, black hole mass, and Eddington ratio., Comment: 10 pages, 11 figures, JKAS in press

We present a detailed analysis of 30 very long baseline interferometric observations of the BL Lac object S5 1803+784 (z=0.679), obtained between mean observational time 1994.67 and 2012.91 at observational frequency 15 GHz. The long-term behaviour of the jet ridge line reveals the jet experiences an oscillatory motion superposed on its helical jet kinematics on a time-scale of about 6 years. The excess variance of the positional variability indicates the jet components being farther from the VLBI core have larger amplitude in their position variations. The fractional variability amplitude shows slight changes in 3-year bins of the component's position. The temporal variability in the Doppler boosting of the ridge line results in jet regions behaving as flaring "radio lanterns". We offer a qualitative scenario leading to the oscillation of the jet ridge line, that utilizes the orbital motion of the jet emitter black hole due to a binary black hole companion. A correlation analysis implies composite origin of the flux variability of the jet components, emerging due to possibly both the evolving jet-structure and its intrinsic variability., Comment: 12 pages, 9 figures, 5 tables, accepted to publish in MNRAS

The $\Lambda$CDM cosmological model successfully reproduces many aspects of the galaxy and structure formation of the universe. However, the growth of large-scale structures (LSSs) in the early universe is not well tested yet with observational data. Here, we have utilized wide and deep optical--near-infrared data in order to search for distant galaxy clusters and superclusters ($0.8

Very Long Baseline Interferometry (VLBI) allows for high-resolution and high-sensitivity observations of relativistic jets, that can reveal periodicities of several years in their structure. We perform an analysis of long-term VLBI data of the quasar S5 1928+738 in terms of a geometric model of a helical structure projected onto the plane of the sky. We monitor the direction of the jet axis through its inclination and position angles. We decompose the variation of the inclination of the inner 2 milliarcseconds of the jet of S5 1928+738 into a periodic term with amplitude of ~0.89 deg and a linear decreasing trend with rate of ~0.05 deg/yr. We also decompose the variation of the position angle into a periodic term with amplitude of ~3.39 deg and a linear increasing trend with rate of ~0.24 deg/yr. We interpret the periodic components as arising from the orbital motion of a binary black hole inspiraling at the jet base and derive corrected values of the mass ratio and separation from the accumulated 18 years of VLBI data. Then we identify the linear trends in the variations as due to the slow reorientation of the spin of the jet emitter black hole induced by the spin-orbit precession and we determine the precession period T_SO=4852+/-646 yr of the more massive black hole, acting as the jet emitter. Our study provides indications, for the first time from VLBI jet kinematics, for the spinning nature of the jet-emitting black hole., Comment: 13 pages, 6 figures, 6 tables (+ 10 pages with 3 tables for online publication only), to appear in MNRAS

Several observational studies and numerical simulations suggest that mergers must contribute to the evolution of galaxies; however, the role that they play is not yet fully understood. In this paper we study a sample of 52 double nucleus disk galaxies that are considered as candidates for a minor merger event. The luminosity of each of the nuclei and their relative separation are derived from a multi-component photometric fit of the galaxies in the Sloan Digital Sky Survey optical images. We find that the nuclei in most of the sources have projected separations $\leq$ 4 kpc. The ratio of nuclear luminosities indicates that most of the systems are likely in the coalescence stage of a major merger. This is supported by the existence of a single galaxy disk in 65% of the systems studied and the finding of a correlation between nuclear luminosity and host luminosity for the single-disk systems: those sources fitted with as single disk are in a more evolved stage of the merger and present an enhancement of the nuclear luminosity compared to the double-disk systems, as expected from simulations of galaxy mergers. Finally, we identify a sample of 19 double nucleus disk galaxies in which the two nuclei are physically separated by $\leq1$ kpc and constitute thus a sample of sub-kpc binary AGN candidates., Comment: 15 pag, 7 fig., accepted for publication in ApJ

In this paper we describe the first data release of the the Visible and Infrared Survey Telescope for Astronomy (VISTA) Deep Extragalactic Observations (VIDEO) survey. VIDEO is a ~12degree^2 survey in the near-infrared Z,Y,J,H and K_s bands, specifically designed to enable the evolution of galaxies and large structures to be traced as a function of both epoch and environment from the present day out to z=4, and active galactic nuclei (AGN) and the most massive galaxies up to and into the epoch of reionization. With its depth and area, VIDEO will be able to fully explore the period in the Universe where AGN and starburst activity were at their peak and the first galaxy clusters were beginning to virialize. VIDEO therefore offers a unique data set with which to investigate the interplay between AGN, starbursts and environment, and the role of feedback at a time when it was potentially most crucial. We provide data over the VIDEO-XMM3 tile, which also covers the Canada-France-Hawaii-Telescope Legacy Survey Deep-1 field (CFHTLS-D1). The released VIDEO data reach a 5-sigma AB-magnitude depth of Z=25.7, Y=24.5, J=24.4, H=24.1 and K_s=23.8 in 2 arcsec diameter apertures (the full depth of Y=24.6 will be reached within the full integration time in future releases). The data are compared to previous surveys over this field and we find good astrometric agreement with the Two-Micron All Sky Survey, and source counts in agreement with the recently released UltraVISTA survey data. The addition of the VIDEO data to the CFHTLS-D1 optical data increases the accuracy of photometric redshifts and significantly reduces the fraction of catastrophic outliers over the redshift range 0

We present a study of the motion of compact jet components in quasar B3 1633+382. Through analyzing 14 epochs of VLBI observations of three components (B1, B2, and B3) at 22 GHz, we find two different possibilities of component classification. Thus two corresponding kinematical models can be adopted to explain the evolutionary track of components. One is a linear motion, while another is a helical model. Future observations are needed to provide new kinematical constraints for the motion of these components in this source., Comment: 7 pages, 3 figures; Accepted for publication in A&A

For the BL Lac object S5 0716+714 conflicting apparent velocities of jet component motion have been reported in the literature. This object is an intra-day variable source and suited to investigate a possible correlation between kinematic properties and flux-density variability on different timescales. We (re-)analyze 50 VLBI observations obtained with the VLBA at 5 different frequencies (5 to 43 GHz) between 1992.73 and 2006.32. We analyze the jet component motion in detail taking care not only to account for motion in the radial but also in the orthogonal direction. We study the evolution of the jet ridge line and search for correlations between radio band light curves and the kinematic properties of the jet components. We present an alternative kinematic scenario for jet component motion in S5 0716+714 with apparent stationarity of jet components (with regard to their core separation) with time. Jet components, however, do seem to move significantly non-radially with regard to their position angle and in a direction perpendicular to the major axis of the jet. We discuss a possible correlation between the long-term radio flux-density variability and the kinematics. We conclude that a geometric contribution to the origin of the long-term variability might not be negligible. Subluminal motion has been reported for most of the TeV blazars. Our analysis also confirms this for S5 0716+714. This result increases the number of TeV blazars showing apparent subluminal motion to 7.

We present a kinematic analysis of jet component motion in the VLBI jet of the BL Lac object S5 1803+784, which does not reveal long-term outward motion for most of the components. Understanding the complex kinematic phenomena can possibly provide insights into the differences between quasars and BL Lac objects. The blazar S5 1803+784 has been studied with VLBI at $\nu$ =1.6, 2.3, 5, 8.4, and 15 GHz between 1993.88 and 2005.68 in 26 observing runs. We (re)analyzed the data and present Gaussian model-fits. We collected the already published kinematic information for this source from the literature and re-identified the components according to the new scenario presented in this paper. Altogether, 94 epochs of observations have been investigated. A careful study of the long-term kinematics reveals a new picture for component motion in S5 1803+784. In contrast to previously discussed motion scenarios, we find that the jet structure within 12 mas of the core can most easily be described by the coexistence of several bright jet features that remain on the long-term at roughly constant core separations (in addition to the already known {\it stationary} jet component $\sim$ 1.4 mas) and one faint component moving with an apparent superluminal speed ($\sim$ 19c, based on 3 epochs). While most of the components maintain long-term roughly constant distances from the core, we observe significant, smooth changes in their position angles. We report on an evolution of the whole jet ridge line with time over the almost 12 years of observations. The width of the jet changes periodically with a period of $\sim$ 8 to 9 years. We find a correlation between changes in the position angle and maxima in the total flux-density. We present evidence for a geometric origin of the phenomena and discuss possible models., Comment: The manuscript will be published by A&A

We present the result of our extensive intranight optical monitoring of the well known low-energy peaked BL Lac (LBL) object PKS 0735+178. This long-term follow-up consists of $R$-band monitoring for a minimum duration of $\sim 4$ hours, on 17 nights spanning 11 years (1998-2008). Using the CCD as an N-star photometer, a detection limit of around 1% was attained for the intra-night optical variability (INOV). Remarkably, an INOV amplitude of $\geq 3%$ on hour-like time scale was not observed on any of the 17 nights, even though the likelihood of a typical LBL showing such INOV levels in a single session of $\ga 4$ hours duration is known to be high ($\sim50%$). Our observations have thus established a peculiar long-term INOV quiescence of this radio-selected BL Lac object. Moreover, the access to unpublished optical monitoring data of similarly high sensitivity, acquired in another programme, has allowed us to confirm the same anomalous INOV quiescence of this LBL all the way back to 1989, the epoch of its historically largest radio outburst. Here, we present observational evidence revealing the very unusual INOV behaviour of this classical BL Lac object and discuss this briefly in the context of its other known exceptional properties., Comment: 24 pages, 4 figures, 2 tables; Accepted for publication in MNRAS

We present a new method to fit the variations of both coordinates of a VLBI component as a function of time, assuming that the nucleus of the radio source contains a binary black hole system (BBH system). The presence of a BBH system produces 2 perturbations of the trajectory of the ejected VLBI components. By using only the VLBI coordinates, the problem we have to solve reduces to an astrometric problem. Knowledge of the variations of the VLBI coordinates as a function of time contains the kinematical information, thus we are able to deduce the inclination angle of the source and the bulk Lorentz factor of the ejected component. Generally, there is a family of the BBH system producing the same fit to our data. To illustrate this method, we apply it to the source 1807+784. We find that the inclination of the source is i = 5.8+-1.8 degrees and the VLBI component is ejected with a bulk Lorentz factor of 3.7+-0.3. We determine the family of the BBH system which provides the best fit, assuming at first that the masses of the 2 black holes are equal and then that the masses are different. Each family of BBH systems is characterized by Tp/Tb~1.967, where Tp and Tb are the precession period of the accretion disk of the black hole ejecting the VLBI component and the orbiting period of the BBH system., Comment: 15 pages, 12 figures