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Utilizing a unique capability of AKARI that allows deep spectroscopy at 2.5- 5.0μm, we performed a spectroscopy study of more than 200 quasars through one of the AKARI mission programs, QSONG (Quasar Spectroscopic Observation with NIR Grism). QSONG targeted 155 high redshift (3:3 3:3. The low redshift part of QSONG is geared to uncover the rest-frame 2.5-5.0μm spectral features of active galactic nuclei to gain useful information such as the dust-extinction-free black hole mass estimators based on the Brackett lines and the temperatures of the hot dust torus. We outline the program strategy, and present some of the scientific highlights from QSONG, including the detection of the Hα line from a quasar at z > 4:5 which indicates a rigorous growth of black holes in the early universe, and the Brβ-based black hole mass estimators and the hot dust temperatures (~1100 K) of low redshift AGNs.

Multiple color selection techniques have been successful in identifying quasars from wide-field broad-band imaging survey data. Among the quasars that have been discovered so far, however, there is a redshift gap at $5 \lesssim {\rm z} \lesssim 5.7$ due to the limitations of filter sets in previous studies. In this work, we present a new selection technique of high redshift quasars using a sequence of medium-band filters: nine filters with central wavelengths from 625 to 1025 nm and bandwidths of 50 nm. Photometry with these medium-bands traces the spectral energy distribution (SED) of a source, similar to spectroscopy with resolution R $\sim$ 15. By conducting medium-band observations of high redshift quasars at 4.7 $\leq$ z $\leq$ 6.0 and brown dwarfs (the main contaminants in high redshift quasar selection) using the SED camera for QUasars in EArly uNiverse (SQUEAN) on the 2.1-m telescope at the McDonald Observatory, we show that these medium-band filters are superior to multi-color broad-band color section in separating high redshift quasars from brown dwarfs. In addition, we show that redshifts of high redshift quasars can be determined to an accuracy of $��{\rm z}/(1+{\rm z}) = 0.002$ -- $0.026$. The selection technique can be extended to z $\sim$ 7, suggesting that the medium-band observation can be powerful in identifying quasars even at the re-ionization epoch., 12 pages, 10 figures, 4 tables, accepted for publication in Journal of the Korean Astronomical Society

We develop a new auto-guiding system for the Camera for QUasars in the EArly uNiverse (CQUEAN). CQUEAN is an optical CCD camera system attached to the 2.1-m Otto-Struve Telescope (OST) at McDonald Observatory, USA. The new auto-guiding system differs from the original one in the following: instead of the cassegrain focus of the OST, it is attached to the finder scope; it has its own filter system for observation of bright targets; and it is controlled with the CQUEAN Auto-guiding Package, a newly developed auto-guiding program. Finder scope commands a very wide field of view at the expense of poorer light gathering power than that of the OST. Based on the star count data and the limiting magnitude of the system, we estimate there are more than 5.9 observable stars with a single FOV using the new auto-guiding CCD camera. An adapter is made to attach the system to the finder scope. The new auto-guiding system successfully guided the OST to obtain science data with CQUEAN during the test run in 2014 February. The FWHM and ellipticity distributions of stellar profiles on CQUEAN, images guided with the new auto-guiding system, indicate similar guiding capabilities with the original auto-guiding system but with slightly poorer guiding performance at longer exposures, as indicated by the position angle distribution. We conclude that the new auto-guiding system has overall similar guiding performance to the original system. The new auto-guiding system will be used for the second generation CQUEAN, but it can be used for other cassegrain instruments of the OST.

Intensity interferometry, based on the Hanbury Brown-Twiss effect, is a simple and inexpensive method for optical interferometry at microarcsecond angular resolutions; its use in astronomy was abandoned in the 1970s because of low sensitivity. Motivated by recent technical developments, we argue that the sensitivity of large modern intensity interferometers can be improved by factors up to approximately 25,000, corresponding to 11 photometric magnitudes, compared to the pioneering Narrabri Stellar Interferometer. This is made possible by (i) using avalanche photodiodes (APD) as light detectors, (ii) distributing the light received from the source over multiple independent spectral channels, and (iii) use of arrays composed of multiple large light collectors. Our approach permits the construction of large (with baselines ranging from few kilometers to intercontinental distances) optical interferometers at the cost of (very) long-baseline radio interferometers. Realistic intensity interferometer designs are able to achieve limiting R-band magnitudes as good as ~14, sufficient for spatially resolved observations of main-sequence O-type stars in the Magellanic Clouds. Multi-channel intensity interferometers can address a wide variety of science cases: (i) linear radii, effective temperatures, and luminosities of stars; (ii) mass-radius relationships of compact stellar remnants; (iii) stellar rotation; (iv) stellar convection and the interaction of stellar photospheres and magnetic fields; (v) the structure and evolution of multiple stars; (vi) direct measurements of interstellar distances; (vii) the physics of gas accretion onto supermassive black holes; and (viii) calibration of amplitude interferometers by providing a sample of calibrator stars., Comment: 19 pages, 4 figures, 3 tables; to appear in JKAS (received June 11, 2014; accepted October 18, 2014)

How galaxy evolution diers in dierent environments is one of the intriguing questions in the study of structure formation. While galaxy properties are clearly distinguished in dierent environments in the local universe, it is still an open issue what causes this environmental dependence of various galaxy properties. To address this question, in this work, we investigate the build-up of passive galaxies over a wide redshift range, from z 2 to z 0:5, focusing on its dependence on galaxy environment. In the UKIDSS/Ultra Deep Survey (UDS) eld, we identify high-redshift galaxy cluster candidates within this redshift range. Then, using deep optical and near-infrared data from Subaru and UKIRT available in this eld, we analyze and compare the stellar population properties of galaxies in the clusters and in the eld. Our results show that the environmental eect on galaxy star-formation properties is a strong function

Galaxy clusters, the largest gravitationally bound systems, are an important subject of study to place constraints on cosmological models. Moreover, they are excellent places to test galaxy evolution models in connection to their environments. To date, massive clusters have been found unexpectedly (Kang & Im 2009; Gonzales et al. 2012) and the evolution of galaxies in clusters is still controversial (Elbaz et al. 2007; Faloon et al. 2013). Finding galaxy cluster candidates at z > 1 in a wide, deep imaging survey data will enable us to solve such issues of modern extragalactic astronomy. We report new candidate galaxy clusters in one of the wide and deep survey elds, the European Large Area ISO Survey North1 (ELAIS-N1) and North2 (ELAIS-N2) elds, covering a sky area of 8.75 deg 2 and 4.85 deg 2 each. We also suggest a new useful color selection technique to separate z > 1 galaxies from low - z galaxies by combining multi-wavelength data.

We describe a survey of quasars in the early universe, beyond z ∼ 5, which is one of the main science goals of the Infrared Medium-deep Survey (IMS) conducted by the Center for the Exploration of the Origin of the Universe (CEOU). We use multi-wavelength archival data from SDSS, CFHTLS, UKIDSS, WISE, and SWIRE, which provide deep images over wide areas suitable for searching for high redshift quasars. In addition, we carried out a J-band imaging survey at the United Kingdom InfraRed Telescope with a depth of ∼23 AB mag and survey area of ∼120 deg, which makes IMS a suitable survey for finding faint, high redshift quasars at z ∼ 7. In addition, for the quasar candidates at z ∼ 5.5, we are conducting observations with the Camera for QUasars in EArly uNiverse (CQUEAN) on the 2.1m telescope at McDonald Observatory, which has a custom-designed filter set installed to enhance the efficiency of selecting robust quasar candidate samples in this redshift range. We used various color-color diagrams suitable for the specific redshift ranges, which can reduce contaminating sources such as M/L/T dwarfs, low redshift galaxies, and instrumental defects. The high redshift quasars we are confirming can provide us with clues to the growth of supermassive black holes since z ∼ 7. By expanding the quasar sample at 5 < z < 7, the final stage of the hydrogen reionization in the intergalactic medium (IGM) can also be fully understood. Moreover, we can make useful constraints on the quasar luminosity function to study the contribution of quasars to the IGM reionization.

Although the link between activity in the nuclei of galaxy and galactic mergers has been under scrutinyfor several years, it is still unclear to what extent and for which populations of active galaxies merger-triggered activity is relevant. The environments of AGN allow an indirect probe of the past merger historyand future merger probability of these systems, su ering less from sensitivity issues when extended tohigher redshifts than traditional morphological studies of AGN host galaxies. Here we present results fromour investigation of the environment of radio selected sources out to a redshift z=2. We employ the rstdata release J-band catalog of the new near-IR Infrared Medium-Deep Survey (IMS), 1.4 GHz radio datafrom the Faint Images of the Radio Sky at Twenty-cm (FIRST) survey and a deep dedicated VLA survey ofthe VIMOS eld, covering a combined total of 20 sq. degrees. At a ux limit of the combined radio catalogof 0.1 mJy, we probe over 8 orders of magnitude of radio luminosity. Using the second closest neighbordensity parameters, we test whether active galaxies inhabit denser environments. We nd evidence for asub-population of radio-selected AGN that reside in signi cantly overdense environments at small scales,although we do not nd signi cant overdensities for the bulk of our sample. We show that radio-AGN inthe most underdense environments have vigorous ongoing star formation. We interpret these results interms of the triggering and fuelling mechanism of radio-AGN.Key words: galaxies: active { galaxies: jets { galaxies: star formation { galaxies: evolution1. THE TRIGGERING OF RADIO-AGNThe recent decades have revolutionized our understand-ing of how galaxies and the supermassive black holes attheir centers evolve (e.g., Springel et al. 2005, Hopkinset al. 2006). However, an ongoing debate concerns theway that active galactic nuclei (AGN) in galaxies aretriggered and sustained. The temporal coincidence ofthe peak of cosmic nuclear and star-formation activity(e.g., Richards et al. 2006, Aird et al. 2010), as well asthe predominantly very luminous AGN discovered be-yond our local universe, have led to the merger-drivenparadigm of AGN triggering (e.g., Sanders et al. 1988).However, with the advent of deeper extragalactic sur-veys this paradigm has come in question. Moderateluminosity X-ray AGN at intermediate redshifts werenot found to be preferentially associated with merg-ers (e.g., Cisternas et al. 2011), nor to inhabit denserenvironments than their non-active counterparts (e.g.,Karouzos et al. 2014a). While undoubtedly a fractionof AGN are triggered by mergers, the question still re-mains: how are di erent species of AGN triggered?Here we use the population of radio-AGN as a case studyto address this question. We present results about thehttp://pkas.kas.orgenvironments and host galaxy properties of radio-AGNthat help elucidate the di erent AGN feeding mecha-nisms within the broader context of galaxy evolution.2. THE SA22 FIELD AND THE RADIO-AGN WITHIN ITWe use data from the Infrared Medium-Deep Survey(IMS; see this proceedings) at J band and the Deep eX-tragalactic Survey (DXS; Lawrence et al. 2007). In ad-dition, we utilize radio data at 1.4 GHz from the FIRSTsurvey (Becker et al. 1995) and a deep VLA survey ofpart of SA22 (Chapman et al. 2004a). The combined ra-dio ux density limit of our sample is 0.1 mJy. Finally,we also employ the full coverage of the WISE telescope(Wright et al. 2010). In total we select 913 radio-AGNover the ˘ 20 deg

We provide results of near-infrared (NIR) spectroscopic observations of 83 nearby (0.002 5 mag and J K>1.3 mag; Glikmanet al. 2007; Urrutia et al. 2009) have been found, andthey are now thought to be galaxies in an intermediatestage. However, their BH masses and activities are stillveiled by their massive dust extinction.It is common to use UV or optical lines such as CIV,Mg II, H , or H emission lines to estimate BH masses,but the usual BH mass estimators su er from dust ex-tinction and cannot give us correct information for BHmasses for the red AGNs. Therefore, previous studieshave tried to establish BH mass estimators using NIRspectrum (e.g., Paschen series: Kim et al. 2010). Inthis study, we derive BH mass estimators using Brack-ett lines, and expect that the Brackett-based BH massestimators will give us correct BH masses of the redAGNs even in type 2 AGNs.In order to use Brackett lines (Br : 2.63 m and Br :4.05 m), we need NIR spectra above 2.5 m. However,http://pkas.kas.orgNIR ( >2.5 m) spectrum of AGNs are scarce due toobservational limitation by atmospheric absorption. Inorder to get the NIR spectra of AGNs, we used theinfrared astronomy satellite AKARI with IRC for 83nearby and bright AGNs. The IRC on AKARI pro-vides us spectroscopic observations with a wide wave-length coverage of 2.5{5.0 m and a low resolution ofR˘120 at 3.6 m.2. RESULTS2.1. BH Mass Estimators with Brackett LinesWe derive new BH mass estimators based on the Br and Br lines, with luminosities serving as a BLR size,and ˙as a velocity. In order to derive BH mass esti-mators, we need three parameters, a, b, and c, in theequation log(M

We present medium resolution (R = 5000-6000) spectra in the near-infrared band, 1.4-1.8 microns, for template stars in G, K, and M types observed by the echelle spectrometer, IRCS, at the SUBARU 8.2 m telescope. The identification of lines is based on the spectra of Arcturus (K2 III) in the literature. We measured the equivalent of widths and compared our results to those of Meyer et al. (1998). We conclude that our spectral resolution (R = 6000) data can investigate more accurately the properties of lines in stellar spectra. The library of the template stellar spectra in ASCII format are available for download on the World Wide Web., 10 Pages including 13 figures. To be published in the JKAS August, 2011 issue, Vol. 44

We present the characteristics of the Seoul National University 4k Camera (SNUCAM) and report its performance on the 1.5m telescope at the Maidanak observatory in Uzbekistan. SNUCAM is a CCD camera with a pixel scale of 0.266” in 4096 × 4096 format, covering 18.1’×18.1’ field of view on the 1.5m. The camera is currently equipped with Bessell UBVRI, Hα, SDSS ugriz, and Y-band filters, allowing us to carry out a variety of scientific programs ranging from exoplanet studies to survey of quasars at high redshift. We examine properties of SNUCAM such as the bias level and its temporal variation, the dark current, the readout noise, the gain, the linearity, the fringe patterns, the amplifier bias, and the bad pixels. From our observations, we also constructed the master fringe frames in I-, z-, and Y-band. We outline some of the current scientific programs being carried out with SNUCAM, and demonstrate that SNUCAM on the 1.5m can deliver excellent images that reach to the 5-σ detection limits of R ~ 25.5 mag and z ~ 22.7 mag in 1 hour total integration.

We outline our GRB afterglow observation program using the 1-m telescope at Mt. Lemmon Optical Astronomy Observatory (LOAO), and report the first observations of the GRB afterglows. During the 2007B semester, we performed follow-up imaging obsrevations of 6 GRBs, and succeeded in detecting four GRB afterglows (GRB 071010B, GRB 071018, GRB 071020, and GRB 071025) while placing useful upper limits on the light curves of the other GRBs. Among the observed events, we find that three events are special and interesting. GRB 071010B has a light curve which has an unusually long jet break time of U.8 days. For GRB 071025, its red R - I (~ 2) color suggests that it is likely to be at z ~ 5. GRB 071020 has a light curve which shows a clear brightening at 0.3-1 days after the burst, where our LOAO data playa crucial role by providing an unambiguous evidence for the brightening. These are the first successful detections of GRB afterglows by a facility owned and operated by a Korean institution, demonstrating the usefulness of the 1-m telescope for transient phenomena such as GRBs up to very high redshift.

This paper summarizes the recent progress made by our group at Seoul National University on studies of the evolution and formation of distant galaxies. Various research projects are currently underway, which include: (i) the number density of distant early-type galaxies (z

We analyze the host galaxy of the tidal disruption object, Swift J1644+57, based on long-term optical to NIR data obtained with CQUEAN and UKIRT WFCAM observations. We decompose the bulge component using high resolution HST WFC3 images. We conclude that the host galaxy is bulge dominant. We investigate optical to NIR light curves and estimate the multi-band fluxes of the host galaxy. We fit spectral energy distribution (SED) models in order to determine the stellar mass. Finally, we estimate the mass of the black hole in the center of the host galaxy based on several scale relations.

We summarize the progress on the rest-frame optical spectroscopy of quasars at 3. This spectral window has been utilized for detecting redshifted emission lines of our high redshift subsample of quasars. From the calculated emission line widths and luminosities we measured supermassive black hole masses using well calibrated optical mass estimators. Science topics regarding optical based black hole masses at high-z are discussed.

We present the results from B-, R-, I-, J- and H-band observations of the NEP-Wide survey field. The NEP-Wide survey is an AKARI survey of the North Ecliptic Pole covering ~ 5 square degrees area. Our optical/NIR imaging supports the AKARI IR imaging data by providing a crucial coverage in the optical/NIR. The optical data were obtained in 2007 using the 1.5 m telescope and SNUCAM at Maidanak Observatory, Uzbekistan. The NIR data were obtained in 2008 with FLAMINGOS on the KPNO 2.1 m telescope. We used IRAF, SExtractor, SCAMP, and SWarp for reducing the raw data, I-band fringe pattern removal, astrometry, standard photometry calibration, and source detection. Our optical-NIR data reach the depths of B ~ 23.4, R ~ 23.1, I ~ 22.3, J ~ 21.05, and H ~ 20.64 AB mag at 5-sigma. Here, we present the astrometric accuracy, galaxy number counts, completeness, and reliability, as well as redshift tracks of some normal galaxies and quasars on the B - R vs. R - I color-color diagram. The photometric data are being used for identifying optical counterparts of the IR data provided by AKARI, studying their SEDs, and selecting interesting objects for spectroscopic follow-up studies.