[Oral Presentations]


======================== 13th Feb. 2019 (Wed) ========================


Session: K-GMT Facilities (Chair: Young-Wook Lee)


황나래 (Narae Hwang) KASI

K-GMT Science Program: Current Status and Future Prospect

I will present the current status of K-GMT Science Program, and share some future prospects that should be of important interest to many participants. Some agenda may need user inputs and active discussions among participants.



Jennifer Lotz Gemini Observatory

Opportunities with the Gemini Observatory

Gemini Observatory invites the Korean astronomy community  to learn about the latest opportunities at Gemini’s twin 8.1 m telescopes in Chile and Hawai'i .  Gemini’s agile queue operations, broad suite of optical/infrared facility and visiting instruments, and diverse proposal opportunities support a wide range of science programs.  We will discuss progress on the Observatory’s facility instruments under development: GHOST, a high-throughput, high-spectral resolution (R~ 50-75,000) spectrograph with continuous coverage at 0.36-0.95 microns; and SCORPIO, an 8-channel optical/IR imager and spectrograph with simultaneous coverage from 0.38-2.5 microns. We will also describe a major new program to develop a state-of-the-art wide-field AO system for Gemini North and enhancements to Gemini’s infrastructure for time-domain astronomy.



이재준 (Jae-Joon Lee) KASI

IGRINS Operation and Science Highlights

IGRINS (the Immersion Grating Infrared Spectrometer) is an echelle spectrometer that can provide an R=45,000 spectrum covering the entire H and K bands in a single exposure, which was built as part of a collaboration between the University of Texas (UT) and the Korea Astronomy and Space Institute (KASI). After a successful commission in early 2014, IGRINS has been operating at the 2.7-m Harlan J. Smith Telescope (HJST) of the McDonald observatory and has successfully visited 4.3m Discovery Channel Telescope and also the 8.1m Gemini South telescope.  I will summarize the performance of IGRINS and its current status. I will also highlight some of its science results.



Session: K-GMT Science 1 (Chair: Myungkook James Jee)


이영욱 (Young-Wook Lee) Yonsei University

Assembling the bulge from globular clusters

We present observational evidence for the formation of the outer Milky Way bulge from stars originated in globular clusters. We also report our on-going spectroscopic survey for the red clump and RGB stars in the bulge with the Gemini and Magellan telescopes.



이광호 (Gwang-Ho Lee) Steward Observatory & KASI

Evolution of Bulk Flows from Starburst to Quiescent Galaxies

We use the Na D ISM absorption line to explore how galactic outflows change with the evolution of their host galaxies. Our sample of ~270,000 SDSS spectra at z < 0.35 is divided into three subsamples that form a crude evolutionary sequence: starburst, post-starburst, and quiescent galaxies. After carefully modeling and removing the stellar continuum from the galaxy spectra, we measure the equivalent widths and velocity offsets of the Na D residual contributed by the ISM. From starburst to post-starburst to quiescent, the fraction of galaxies with significant outflows decreases from 70% to 50% to 20%. Even within the post-starburst sample, this outflow fraction similarly decreases with post-burst age. These results suggest that outflows diminish as their host galaxies age. However, the fiber-based SDSS spectra do not spatially-resolve the outflows. To better understand the origin of the outflows and their role in quenching star formation, we are conducting systematic GMOS-IFU observations of post-starburst galaxies with known post-burst ages.



현민희 (Minhee Hyun) Seoul National University

A study of galaxy overdensities at z~1 in ELAIS-N1 field

Galaxy clusters are the largest gravitationally bound structures in the universe and located in the densest peak of the dark matter. They can constraint on the cosmological model from their dark matter halo distribution and they are good laboratories to study how galaxy evolution varies with their environment. Especially, studies of galaxy clusters at z ≳ 1 are important because (i) galaxy evolution at z >1 is still controversial (Elbaz et al. 2007; Faloon et al. 2013) and (ii) some studies show that mass of galaxy clusters at z>1 seems to be higher than expected value from the cosmological model (Kang & Im 2009; Gonzales et al. 2012). In spite of their significance, there have not been many studies of galaxy clusters at z ≳ 1 because of the lack of wide and deep multi-wavelength data.  We newly found galaxy cluster candidates at 0.2 < z < 1.4 and a LSS spanning over 100Mpc at z~0.9 in ELAIS-N1 field which is one of the IMS (Infrared Medium-deep Survey; Im et al. 2017, in preparation) fields. Thanks to K-GMT science program, we performed spectroscopic follow-up observation for a z~1 galaxy cluster candidates with GMOS of Gemini North and for z~0.9 supercluster candidates with Hectospec of MMT in 2018A. We will present the result of the observation.  



김서진 (Seojin Felix Kim) Yonsei University

Weak-lensing Analysis of the Massive High-z Cluster MOO J1014+0038 with HST and GMOS Observations

Especially with a wide range of redshift, a cluster mass function can constrain various cosmological parameters. However, measuring the masses of galaxy clusters at high redshifts is not so simple since the common assumption of the hydrostatic equilibrium may not be applicable and thus masses derived from that such as Sunyaev-Zel’dovich or X-ray masses are subject to bias. Weak lensing is one of the few methods that does not need the assumption. The “See Change” Hubble Space Telescope program offers very deep and high-resolution images of 12 high-z (z>1) clusters, suitable for the weak lensing analysis. In this presentation, we focus on one of them, MOO J1014+0038 at z=1.24. Previous studies suggest that this cluster is quite massive but no lensing analysis has been carried out yet. There is not a public spectroscopic member catalogue as well, which could give the more accurate redshift and some insights on the substructure and the dynamical mass. Hence we perform multi-slit spectroscopic observations with GMOS South and confirm 11 members. We also successfully detect clear lensing signals after carefully treating the instrumental systematics of the Wide Field Camera 3. We present its 2-D mass distributions and compare it with previous studies based on the intracluster medium of the cluster.



======================== 14th Feb. 2019 (Thu) ========================


Session: K-GMT Science 2 (Chair: Myung Gyoon Lee)


John Blakeslee Gemini Observatory

The Science and Future of Gemini Observatory

After highlighting recent scientific results from Gemini Observatory, I will describe the new “Gemini in the Era of Multi-Messenger Astronomy” (GEMMA) Program. The projects that comprise GEMMA focus on the areas of high spatial resolution and rapid-response astronomy. The GEMMA Time Domain Astronomy (TDA) project will develop the infrastructure for incorporating Gemini’s telescopes into an efficient new system for following up transients identified by LSST, LIGO, and other time-domain and multi-messenger surveys. The Gemini North Adaptive Optics (GNAO) upgrade project will deliver the first queue-operated multi-conjugate AO system in the northern hemisphere. With a corrected field-of-view of about 2 arcmin and spatial resolution similar to that of JWST, GNAO will take advantage of Maunakea’s outstanding conditions for AO performance. GEMMA also includes outreach efforts to communicate the excitement of multi-messenger astronomy to the general public.



임명신 (Myungshin Im) Seoul National University

Multi-Messenger Astronomy with Gemini and IMS 2018 Progress Report

The discovery of a neutron-star merger GW170817 and the identification of a  distant neutrino source in the years of 2017 and 2018 opened up a new era of studying the universe using combined information from gravitational wave (GW), neutrino, and electromagnetic (EM) wave signals - namely, Multi-Messenger Astronomy (MMA). Optical/NIR observation has a key component in MMA, and we will describe how MMA is going to unlock the secrets of the universe. We will also describe the ongoing MMA efforts of our group at SNU/Korea, and our plan of GW source follow-up observations including an approved Gemini program. Additionally, we will briefly summarize scientific achievements of our group in 2018 with K-GMT programs, such as red quasars, the discovery of high redshift faint quasars, and the study of the environment of massive quasars.



Session: K-GMT Science 2 - cont. (Chair: Jongwan Ko)


양유진 (Yujin Yang) KASI

Polarimetric Survey of Giant Lyman Alpha Nebulae

I will present (1) KASI-Arizona polarimetric survey of giant Lyα nebulae at high-redshift using MMT/SPOL, (2) MMT/SPOL instrument upgrade done by KASI Space Astronomy group, (3) our on-going effort on Lyα radiative transfer and polarimetric modeling, and (4) discuss the polarimetric capability of Gemini/GMOS.



정웅섭 (Woong-Seob Jeong) 한국천문연구원 (KASI)

Nature of High-Redshift Dust-Obscured Galaxies in the ADF-S

We present the preliminary results for NIR spectroscopic follow-ups with FLAMINGOS-2 at GEMINI-S of Dust-Obscured Galaxies (hereafter DOGs) identified by optical imaging survey of AKARI Deep Field South (ADF-S) using the Korea Microlensing Telescope Network (KMTNet). The Dust-Obscured Galaxies with f(24um)/f(R)>~1,000 in the heavily obscured system are expected to play an important role in the formation of most massive galaxies. Using the existing various infrared photometric dataset from 3.6μm to 500μm from AKARI/Spitzer and Herschel, in addition to multi-band optical/near-infrared imaging data from KMTNet and VISTA, we uniquely constrained physical parameters of individual DOG using the SED fitting method. Among them, we specifically choose 15 DOGs for our spectroscopic follow-ups, that are hyperluminous and/or very massive. We identified the H_alpha emission from 9 out of 14 DOGs and interestingly, broad H_alpha line was detected from 8 out of 9 DOGs. We discuss the physical properties of DOGs and the relation between the star formation and the AGN activity in hyperluminous DOGs.



황호성 (Ho Seong Hwang) KASI

The KIAS Redshift Survey of Nearby Galaxy Groups and Clusters with MMT/Hectospec

Galaxy groups and clusters are important astrophysical laboratories for testing structure formation models. I will review the results from the KIAS redshift survey with MMT/Hectospec focusing on galaxy groups/clusters and their connection to the large-scale structures in the universe.



이원기 (Wonki Lee) Yonsei University

Observation of merging galaxy clusters with radio relics: Numerical simulations and MMT/Hectospec observations

A merging galaxy cluster is a useful laboratory to study many interesting astrophysical processes and the evolution of galaxy environment. Some cluster mergers show extended radio emissions called radio relics, which potentially enable us to constrain their merger scenarios and test our understanding of plasma physics of shock acceleration. Multi-wavelength observations with follow-up numerical simulations have been used to study the history of cluster mergers. However, the exact physical mechanism happening in the outskirts of the cluster mergers is still shrouded in a veil. In this talk, we will present our future MMT/Hectospec programs on the three interesting cluster mergers with distinct radio relics: Abell 746, Abell 1240 and ZwCL1856. Based on previous studies with MMT observations and numerical studies, we will forecast the expected outcomes that will be newly discovered with our observational program. In addition, we will discuss our on-going merging cluster studies with an emphasis on the derivation of the merger scenarios using our current multi-wavelength observations. The same methodology will be applied to our new targets.



Session: K-GMT Science 3 (Chair: Minjin Kim)


우종학 (Jong-Hak Woo) Seoul National University

Probing supermassive black hole physics from the gravitational sphere of influence to galactic scales: highlights from SNU AGN studies

I will highlight a couple of exciting results from our AGN studies with the K-GMT facilities. First, I will report a light-echo measurement, indicating a tiny black hole at the center of a nearby galaxy NGC 4395. The reverberation-mapping result opens a new window for searching for a population of intermediate mass black holes in dwarf galaxies, which will be a crucial signpost for understanding the formation of black hole seeds at the dawn of the universe. Second, I will present the main results from our series of studies of AGN outflows and their connection to star formation based on the Gemini GMOS-IFU data. Using a sample of low-z AGNs, we find that the kinematically-determined size of AGN outflows correlates with AGN luminosity. However, the typical size of outflows is relatively small, indicating that the overall impact of the outflows over the entire host galaxy is limited, questioning the instantaneous negative feedback. Third, to better constraint the star formation rate of AGNs with strong outflows, we utilized the sub-mm continuum flux obtained with the JCMT SCUBA-2, for measuring the total IR luminosity based on the SED. I will present the calibration of star formation rate based on sub-mm data and discuss the connection between star formation and AGN outflows.



김도형 (Dohyeong Kim) Peking University

A candidate of sub-kpc-scale binary SMBH found in obscured red AGNs

We report the GMOS IFU observation of a binary SMBH candidate found in obscured red AGNs. Obscured red AGNs have been undergoing galaxy mergers and suspected as young AGNs or intermediate phase galaxies between merger-driven star-forming galaxies and unobscured AGNs. Our sample was identified as a binary SMBH candidate due to its significant merging features and double-peaked broad emission lines found in Hb, Ha, Pb, and Pa lines. The double-peaked broad emission lines can be decomposed into primary-blue and secondary-red components, and they are separated by ~3000 km/s. Through the GMOS IFU observation, we investigate the spatial distributions of these two components in the Ha line. Intriguingly, the two components are spatially separated by ~0.1" (~290 pc). If it is confirmed via further observations in the future, being one of very rare cases of sub-kpc-scale binary SMBHs will provide us unique opportunities (i) to understand the co-evolution of SMBHs and their host galaxies; (ii) to constrain the galaxy evolution model; and (iii) to constrain the gravitational wave detection rate. Moreover, in addition to presenting a binary SMBH candidate, we attempt to emphasize the necessity of binary SMBH surveys for obscured red AGNs in the future.



신재진 (Jaejin Shin) Seoul National University

A search for low metallicity quasar at z~3 with Gemini/GNIRS

The Fe II/Mg II flux ratio has been used to investigate the chemical evolution of high redshift AGNs. No evo- lution has been found out to z ∼ 6, implying that the type 1a supernova activity has been already occurred in early universe. However, the trend of no evolution is possibly caused by the sample bias since the previous studies utilized mostly very luminous AGNs, which may be already chemically matured at the observed red- shift, resulting in the high Fe II/Mg II ratio. As motivated by the luminosity-metallicity relation (e.g., Nagao et al. 2006b), we investigate the Fe II/MgII flux ratio over a large dynamic range of luminosity, by focusing on a sample of 12 low-luminosity quasars at z ∼ 3, based on the Gemini/GNIRS observations. We find compara- ble Fe II/Mg II ratios between low- and high-luminosity quasars at similar redshift. One interpretation is that the low-luminosity quasars in our sample are still relatively luminous (i.e., log Lbol ∼ 46.5) and their ISM is chemically matured. To search for chemically young AGNs, further investigations with much lower-luminosity AGNs are necessary to investigate the chemical evolution based on the Fe II/Mg II/ flux ratio.



조호진 (Hojin Cho) Seoul National University

Hα reverberation mapping of NGC 4395 based on the Gemini spectroscopy and the photometry with small telescopes

NGC 4395 is a dwarf galaxy harboring an active black hole with the lowest AGN luminosity and mass among the known Seyfert 1 galaxies. Thus, NGC 4395 is the best target to study black hole-host galaxy correlations at low mass scales as well as the broad line region radius-luminosity relation at the low-luminosity end. We performed two monitoring campaigns, respectively, in 2017 and 2018, using Gemini-North and multiple 1m-class telescopes including MDM, BOAO, etc. to measure the time lag between broad Hα line and optical continuum. We find that the size-luminosity relation seems to fail at the very low-luminosity regime although the AGN luminosity is relatively uncertain due to the nuclear star cluster at the very center, which is revealed by the HST imaging.



Session: K-GMT Science 4 (Chair: Jae-Joon Lee)


임범두 (Beomdu Lim) Kyung Hee University

Rotating stars in the Galactic open cluster M11

Star clusters have long been believed to comprise a simple stellar population. But, this paradigm has been steadily challenged by the fact that a number of young star clusters in the Magellanic Clouds show significant color spread of stars at main sequence turn-off. This is the so-called “extended main sequence turn-off” feature. To explain the origin of this feature, age spread and stellar rotation have been proposed, however these factors have been examined using only stellar evolution models in a limited way. A large color spread of stars at main sequence turn-off is found in the Galactic open cluster M11. The proximity of this object allows us to derive reliable stellar parameters of individual cluster members, and thereby to test the impacts of these factors on stellar colors. In this talk, I will discuss about the origin of the color spread in the context of stellar evolution considering the effects of rotation.



허정은 (Jeong-Eun Heo) Sejong University

RAMSES II - RAMan Search for Extragalactic Symbiotic Stars

Symbiotic stars (SySts) are promising candidates as progenitors of SN Ia so that it is important to estimate their population for our proper understanding of stellar evolution on the late stage of low and intermediate stars. Thus far, the number of known Galactic SySts is ~ 250, whereas the prediction from population synthesis models ranges from 3, 000 to 4×10^5. The huge discrepancy between the observation and theoretical expectations may be found in the fact that spectroscopic criteria have been used to identify SySts, which is supposed to be more inefficient to search SySts than photometric approach. The two intense Raman O VI bands at 6830 Å and 7088 Å are, however, are so unique to the symbiotic phenomenon that their presence has been considered a sufficient criterion for classifying a star as a bona fide symbiotic. Through the 2016 Gemini Observatory Instrument Upgrade Project, the RAMSES II team purchased a set of narrow-band filters for both GMOS centered on Raman O VI 6830 Å. It aims at therefore discovering and characterizing the symbiotic population of the Milky Way and Local Group galaxies via the first purely photometric tool. On Dec, 2018, the RAMSES II Acceptance Test (AT) Report has been approved by the Gemini Observatory. In this talk we present the concept, commissioning and science verification phases, as well as the very first scientific AT results, of RAMSES II.



오희영 (Heeyoung Oh) KASI/UT Austin

3-Dimensional Shock Physics of Outflows using IGRINS

Immersion Grating Infrared Spectrometer (IGRINS) is a powerful tool for investigating shock physics of dense medium, due to its large wavelength coverage (1.5-2.5 micron) and high spectral resolving power (R ~45,000). We present the results of the spectral mapping toward a remarkable chain of bows (HH 205-HH 207) over ~ 0.1 pc area in the Orion KL outflow, using a dataset made with the 2.7 m Harlan J. Smith Telescope at McDonald Observatory. Datacubes of more than 40 of shock or UV excited emission lines from H2, [Fe II], and Brackett series allow us to dig up the kinematics and physical parameters such as excitation temperature, electron density, and extinction of bullet bows highly interacting with the medium. We also report the preliminary results from IGRINS/Gemini South observation which probe the nature of bow-shock with extremely High-velocity H2 emission.



박선경 (Sunkyung Park) Kyung Hee University

High-resolution spectroscopic survey of FU Orionis-type objects

Accretion disks around young stellar objects play an important role in the star formation process. While the detailed accretion mechanism from the disk to the central star is still poorly understood, episodic accretion bursts are likely important in stellar growth and disk evolution. FU Orionis-type objects (FUors) are well-studied examples of episodic accretion because of their outburst phenomenon. We present the preliminary results of high-resolution (R ~ 45,000) near-infrared spectroscopic survey of FUors with Immersion GRating INfrared Spectrograph (IGRINS). We observed about 20 FUors with IGRINS since November 2014. The observed spectra show several characteristics of FUors: double-peaked profiles and broad CO first overtone absorption features. We highlight two individual targets, which has been monitored spectroscopically since their outburst.



André-Nicolas Chene (Gemini Observatory) and Soung-Chul Yang (KASI)

The Gemini Operation and User Supports for Dummies - featured by the Operation of the Korea Gemini Office (KGO)

The K-GMT Science Group in KASI has been providing Korean Astronomy Society with an opportunity to use 8m Gemini Telescope and 6.5m Multiple Mirror Telescope (MMT) through "limited-term-partnership" since 2015. As a result of active research activities from the user community and the joint efforts of the project managing staffs of the K-GMT Science Group, KASI has now joined in the operation of Gemini Observatory as a full partner since 2019 spring season. Unlike the past observation mode (i.e., Priority Visitor (PV) mode) under the "limited-term-partnership", the upcoming Gemini observations will be performed in the queue mode, and various routes of the proposal and new types of observing modes will be available from 2019A. In today's talk, André-Nicolas will present a general overview of the Gemini Operation and Support to users, insisting on the various ways to propose for telescope time, the resources available to help you with your proposal/program and support material for data reduction. Soung-Chul will present general guidelines and notable new changes for the Korean Astronomy Society in the Gemini observation from 2019A. Some useful tips for preparing Gemini proposals also will be given.



======================== 15th Feb. 2019 (Fri) ========================


Session: Synergy with other facilities (Chair: Narae Hwang)


권우진 (Woojin Kwon) KASI

“Dancing” with ALMA

We are facing the great era with the unprecedented, large optical telescopes. However, by definition, observations of optical wavelengths alone can reveal only a part of the universe, which is filled with a variety of objects in various radiative mechanisms and at a broad range of temperatures. I will introduce the Atacama Large Millimeter/submillimeter Array (ALMA), which has opened up the great era of radio observations and which will be the main complementary tool for optical and near-IR observations.



Jinyoung Serena Kim Steward Observatory, University of Arizona

Observing with MMT: Available Instruments and Science Highlights

I will review the current and new instruments available at the MMT Observatory and will present a few selected science highlights, from local star forming regions to high-z objects, using these instruments. The instrument suite includes: Binospec, MMIRS, Blue Channel, SPOL, Hectospec, Hectochelle, and MMTCam. In this talk I will concentrate on the capabilities of the newest of the MMT's instruments, Binospec and MMIRS. I will also advertise the MMT Observatory's 40th Anniversary Symposium, to be held from May 14-16, 2019 at the University of Arizona. We would like to encourage Korean observers to join the celebration.



Session: K-GMT Science 5 (Chair: Narae Hwang)


이성국 (Seong-Kook Lee) Seoul National University

Observing active cluster formation era with large telescopes

Galaxy clusters at z~1 and beyond provide good laboratory for the study of galaxy evolution as well as structure formation. In this presentation, we will present our recent results about the star-formation properties of z~1 galaxy clusters. The star-formation properties show large variation among individual clusters and also interesting dependence on large scale structure. This study is done using the UKIDSS/UDS data (including the data from Subaru and UKIRT) and the Magellan telescope, and the presented results will highlight the benefits and necessity of using large telescopes for this kind of studies. 


Mariela Martinez Paredes KASI

The inner (< 1 kpc) mid-IR emission of QSOs: the torus and their surrounding starbursts

Quasi Stellar Objects (QSOs) are between the most luminous (L>10^43 erg s^-1) active galactic nucleus in the Universe. Their high luminosity and compact morphology have difficulted the study of their inner emission in different wavelength. Taking advantage of the high angular resolution offered by the largest optical ground-based telescopes, like the 10.4m Gran telescopio CANARIAS and the ESO Very Large Telescope at mid-IR, we studied the inner (< 1kpc) mid-IR emission for a sample of local (z<0.1) QSOs. In this talk I will present the results that we obtained from study this nuclear emission, which is mostly dominated by dust heated by the AGN. Particularly, I will show how the properties of the dusty torus of QSOS are intrinsically different from the properties of the dusty torus of Seyfert. I will  show that the combination of the geometrical parameters of the dusty torus in QSOs suggest that the clouds in the torus might have been partially evaporated and piled away by the high radiation field, as proposed by the receding torus scenario. Additionally, I will present evidences of survival of Polycyclic Aromatic Hidrocarbon molecules, which track the recent star formation, to the strong radiation of the AGN on scales of some hundred of pc, since it was previously thought that this molecule could survive to the strong radiation of the AGN only on scales of few kpc.





[Poster Presentations]



조완진 (Wanjin Cho) Seoul National University

Optical Variability base on B-band photometry from The Seoul Natioanl University AGN Monitoring Project(SAMP)

We present the photometric monitoring results for a sample of highly variable type 1 AGNs, based on last 3-year campaign. The SNU AGN Monitoring Project (SAMP) is a long-term reverberation mapping campaign, aiming for measuring the time lag of broad emission lines and black hole masses of intermediate-to-high luminosity AGNs. Based on the photometry carried out using MDM 1.3m telescope, we present the characteristics of variability and B band light curves of a subsample of the most variable AGNs.



강 인 (In Kang) Kyung Hee University

Probing the disk rotation of a massive young stellar object with IGRINS

Massive stars play an important role in terms of their feedback, but their formation process is poorly understood. Rare observational evidence suggests that a massive star is formed by accretion disk like a low mass star. Thus disk observations of massive young stellar objects (MYSOs) are important to understanding the formation process of massive stars. The inner gaseous disk can be observed with the high-resolution near-infrared spectroscopy using IGRINS. We observed a MYSO, Min 2-62, using IGRINS and detected a double peak feature in the Bracket, Pfund series lines. We report the preliminary results of a rotating disk of MYSO, Min 2-62 from IGRINS.



김준호 (Joonho Kim) Seoul National University

Searching for Electromagnetic Counterpart of Gravitational Wave Source with KMTNet

After first identification of electromagnetic counterpart of gravitational wave source (GW170817), era of multi-messenger astronomy has begun. For specifying coordinate, magnitude, and host galaxy information, optical follow-up observation of GW source becomes important. With following engineering run and O3 run of LIGO and VIRGO starting in March 2019, we present searching strategy for optical counterpart of GW source using KMTNet. 24 hours monitoring system and large field of view (4 square-degree) of KMTNet are advantage to discover a transient like GW event. By performing tiling observation of high probability area in GW localization map, we expect to observe early light-curve of GW optical counterpart. After identification, follow-up observation using Gemini will also be performed.



이서나 (Seona Lee) Yonsei University

ISM truncation due to ram-pressure stripping: Theory vs. Observation

It has been proposed by Gunn & Gott (1972) that galaxies may lose their interstellar gas while falling to the cluster potential by ram pressure due to the dense intra-cluster medium. The observational evidence for this process, which is known as ram pressure stripping, is increasing, and it is believed to be one of the key environmental effects that can dramatically change the star formation activity of galaxies and hence their evolution. Intriguingly however, quite a number of cases showing clear signs of ram pressure stripping are found in the environment which betrays our expectations (e.g. large clustercentric distances), and our understandings to the detailed working principle behind ram pressure stripping seem to be still lacking. In this work, as one of the ways to gain more theoretical insights into the conditions for ram pressure stripping process, we are comparing the gas truncation radius which is predicted based on the simple Gunn & Gott’s prescription with what is actually observed in carefully selected Virgo galaxies. In this poster, we present preliminary results and discuss which additional conditions need to be taken into account in order to fully understand the observations. We also discuss how mid to large-sized optical telescopes can contribute to leverage our probe of the impact of ram pressure stripping on galaxy evolution.



Rongxin Luo Seoul National University

Probing the Weak Outflows in Local Type-2 AGNs with Integral-Field Spectroscopy

AGN-driven outflow is considered as one of the processes driving the co-evolution of supermassive blackholes with their host galaxies. We present Gemini Multi-Object Spectrograph integral field spectroscopy of six luminous Type 2 AGNs at z < 0.1, which are selected based on the kinematics of [O III] gas as AGNs without strong outflows. We investigate kinematics and photoionization properties using emission lines in comparison with AGNs with strong outflows. From the spatially resolved spectra, we observe significant difference between the kinematics of ionized gas and stars, which are presumably signatures of AGN-driven outflows, while the velocity and velocity dispersion of outflowing gas are lower than those in AGNs with strong outflows, suggesting relatively weak outflows in our sample. Our results highlight the importance of spatially-resolved observation in investigating gas kinematics and identifying the signatures of AGN- driven outflows.



백인수 (Insu Paek) Seoul National University

Study of Galaxy Clusters in CFHTLS W2 Field

Using optical and infrared data on the CFHTLS W2 field, the density distribution the 25 square degree CFHTLS W2 field was mapped in 2-dimensional photometric redshift slices. Galaxy clusters and galaxy groups were identified from the density distribution. Utilizing stellar population synthesis on the member galaxy spectra, the star formation activity among galaxy cluster were estimated. The correlation between star formation activity and presence of nearby density structure is studied in depth.



Neha Sharma Kyung-Hee University

NIR spectroscopy of 3 class I protostars using IGRINS

We present near-infrared spectroscopic results for 3 nearby class I sources, IRAS 03445+3242, IRAS 04239+2436 and ESO Hα 279a. We detected many molecular and atomic emission lines, e.g., H2, [Fe II], Hydrogen Bracket series recombination, Ca I, Na I & CO overtone band, from these sources using the high-resolution Immersion GRating INfrared Spectrometer (IGRINS; R~45,000).  Previous studies showed that all the three sources posses an actively accreting Keplerian disks. We performed a spectral analysis to understand the origin of Hydrogen Bracket series recombination lines. We also estimated the accretion properties and mass loss rates of circumstellar disks for all the three sources.



탁윤찬 (Yoon Chan Taak) Seoul National University

High-z Universe probed via Lensing by QSOs (HULQ): How many QSO lenses are there?

The evolution of scaling relations between SMBHs and their host galaxies becomes uncertain at high redshifts. The HULQ project proposes to use gravitational lensing to measure the masses of QSO host galaxies, an otherwise difficult goal. SMBH masses of QSOs are relatively easy to determine using either reverberation mapping or the single-epoch method. These measurements, if made for a substantial number of QSOs at various redshifts, will allow us to study the co-evolution of SMBHs and their host galaxies. To determine the feasibility of this study, we present how to estimate the number of sources lensed by QSO hosts, i.e. the number of deflector QSO host galaxies (hereafter QSO lenses). Using SMBH masses measured from SDSS DR14 spectra, and the M_BH – Sigma relation, the Einstein radii are calculated as a function of source redshift, assuming singular isothermal sphere mass distributions. Using QSOs and galaxies as sources, the probability of a QSO host galaxy being a QSO lens is calculated, depending on the limiting magnitude. The expected numbers of QSO lenses are estimated for ongoing and future wide-imaging surveys, and additional factors that may affect these numbers are discussed.



윤성용 (Sungyong Yoon) Kyung Hee University

Accretion Burst Signatures in IRAS 16316-1540 Revealed by High-Resolution NIR Spectroscopy

The high-resolution near-infrared (NIR) spectroscopy can reveal the evidence of the accretion burst (e.g., the broadened absorption features produced by the Keplerian disk motion) although the moment of the outburst was not caught. The embedded protostar IRAS 16316-1540 observed with the Immersion Grating Infrared Spectrograph (IGRINS, R=Δλ/λ ~ 45,000) shows the broad absorption features in atomic and CO transitions, as seen in FU Orionis objects (FUors), indicative of an outburst event. We examine whether the spectra of IRAS 16316-1540 arise from the rotating inner hot gaseous disk. Using the IGRINS spectral library, we show that the line profiles of IRAS 16316-1540 are more consistent with an M1.5 V template spectrum convolved with a disk rotation profile than the protostellar photosphere absorption features with a high stellar rotation velocity. We also note that the absorption features deviated from the expected line profile of the accretion disk model can be explained by a turbulence motion generated in the disk atmosphere. From previous observations that show the complicated environment and the misaligned outflow axes in IRAS 16316-1540, we suggest that an impact of infalling clumpy envelope material against the disk induces the disk precession, causing the accretion burst from the inner disk to the protostar.