[Poster Presentations]

 

이정환 (Jeong Hwan Lee)        Seoul National University        

A GMOS/IFU Study of the Star Formation Activity of Jellyfish Galaxies in Massive Galaxy Clusters        

Jellyfish galaxies show interesting blue knots in their disks and tails due to strong ram-pressure stripping (RPS). These knots are composed of young stars, implying that the star formation activity of jellyfish galaxies is locally enhanced within a short period of time.

Thus, jellyfish galaxies are ideal laboratories to study the relation between their star formation activity and RPS. Previous integral field spectroscopic studies of jellyfish galaxies have been limited to low-mass clusters, where the RPS effect is expected to be mild.

In order to investigate extreme RPS effects on jellyfish galaxies, we observe three jellyfish galaxies in very massive clusters using Gemini GMOS/IFU. We select jellyfish galaxies from galaxy clusters in the MAssive Cluster Survey (MACS) and Hubble Frontier Fields (HFF), where RPS is expected to be much stronger than in low-mass clusters. Our results show that star-forming knots in the three jellyfish galaxies are dynamically cold and excited by photoionization, in agreement with the results from jellyfish galaxies in low-mass clusters. However, the star formation rates of our sample galaxies are much higher than those of jellyfish galaxies in low-mass clusters. This implies that the star formation activity of jellyfish galaxies is much more enhanced in massive clusters than in low-mass clusters. We suggest that there is a positive correlation between the star formation activity of jellyfish galaxies and RPS by including the jellyfish galaxy samples in massive galaxy clusters.

 

 

[Oral Presentations]

 

======================== 19th Nov. 2020 (Thu) ========================

 

Session: K-GMT Facilities (Chair: Soung-Chul Yang)

 

황나래 (Narae Hwang)        KASI        

(TBD) K-GMT Science Program: Status and Future Perspective        

TBW

 

오희영 (Heeyoung Oh)        KASI

IGRINS Operation (TBD)        

 

박찬 (Chan Park)        KASI

IGRINS-2: New IGRINS for Gemini Telescopes        

 

 

Session: K-GMT Science 1 - Stars/Milky Way (Chair: Sang-Hyun Chun)

 

이영선 (Young Sun Lee)        Chungnam National University        

Chemical and Dynamical Properties of Extremely Metal-Poor ([Fe/H] < -3.0) Stars Observed with Gemini/GRACES        

Extremely metal-poor (EMP; [Fe/H] < -3.0) stars in the Milky Way (MW) are thought to be genuine second-generation of stars because they were born from relatively pristine gas chemically enriched by one or two supernovae. Thus, the chemistry and kinematics of these stars serve as powerful tools to trace the early chemical evolution and assembly history of the MW. In this study, we present the preliminary results on the chemodynamical analysis of about two dozens of the EMP stars, which are newly discovered by the observations with Gemini/GRACES.

 

임범두 (Beomdu Lim)        Kyung Hee University        

The Gaia-Hectochelle survey of the Galactic OB associations        

Star formation in the Galactic disk takes places along hierarchical structures with self-similar nature. Molecular cloud complexes are composed of several stellar associations. Similarly, stellar clusters and distributed stellar populations constitute stellar associations. Therefore, stellar associations are the essential units for understanding the star formation process on different spatial scales. In this context, it is necessary to study their formation and evolution. There are three theoretical models explaining their formation process: dynamical evolution of star clusters, star formation in turbulent clouds, and feedback-driven star formation. The signatures of their formation process may remain in the kinematic properties of stars, since the age of stellar associations is still young. In order to assess these theoretical models from stellar kinematics, the Gaia-Hectochelle survey of several Galactic OB associations was initiated. In this talk, we present some results obtained from this survey.

 

박선경 (Sunkyung Park)        Konkoly Observatory

High-resolution near-infrared spectroscopic survey of FU Orionis-type objects

Accretion disks around young stellar objects play an important role in the star formation process. While the accretion mechanism from disk to central star is still poorly understood, episodic accretion bursts are likely important in the growth of star and evolution of disk. FU Orionis-type objects (FUors) are observable evidence of episodic accretion. Observations show that FUor-type outbursts can happen at all evolutionary phases, from the very embedded objects to the ones with only tenuous remnant envelopes. We have been conducting a survey of 20 FUors with Immersion GRating INfrared Spectrograph (IGRINS). Our aim is to relate the observed variety of spectral features to differences in the evolutionary state. We present the preliminary results of the FUors survey.

 

홍승수 (Seungsoo Hong)        Yonsei University

Spectroscopic Survey for Bulge Red Clump Stars: New Insights on the Structure and Formation of the Milky Way Bulge

Two scenarios have been suggested to explain the double red clump (RC) phenomenon observed in the Milky Way bulge. One is the X-shaped bulge model, and the other is multiple population model as is observed in globular clusters (GCs). Because these two scenarios imply very different pictures on the formation of the bulge, understanding the origin of the double RC is of crucial importance. In order to investigate the origin of the double RC, we are undertaking spectroscopic surveys for the RC stars in different latitude and longitude fields of the bulge. Low-resolution multi-object spectroscopy for CN index is being performed with LCO 2.5m and Gemini south 8.1m telescopes, while high-resolution spectroscopy for Na and Fe abundances is being carried out with the M2FS instrument on the Magellan 6.5m telescope. In this talk, we will present our preliminary results of the surveys.

 

 

Session: K-GMT Science 2 - Galaxies/Galaxy Cluster (Chair: Yun-Kyeong Sheen)

 

고유경 (Youkyung Ko)        Korea Astronomy and Space Science Institute        

Wide-field Kinematics of the Globular Cluster System in the Peculiar Massive Galaxy M85        

M85 is a massive merger remnant galaxy in the Virgo Cluster that shows intriguing features produced by past mergers. It is of great importance to study how these merger remnants have been formed and evolved in the context of the hierarchical galaxy formation scenario. Globular clusters (GCs) are one of great tools to investigate the faint stellar halo where merging features last long and to trace the assembly history of their host galaxy. In this talk, I will present a study on kinematics of GCs in M85 based on the wide-field spectroscopy taken from MMT/Hectospec. We find a strong rotation feature of the inner GC system and a bulk motion of a GC subpopulation, which are clearly distinct from those of typical massive galaxies. We infer that M85 has undergone merging events lately, resulting in the peculiar kinematics of the GC system.

 

강지수 (Jisu Kang)        서울대학교 (Seoul National University)

Are Nearby Massive Compact Elliptical Galaxies Local Analogs of Red Nuggets?

Nearby massive compact elliptical galaxies (MCEGs) are as massive as giant elliptical galaxies but extremely compact (M* > 1.0e11 Msun, Reff < 1.5 kpc). They are strong candidates for relic galaxies that have not undergone many mergers. We can determine if MCEGs are indeed relic galaxies by studying their globular cluster (GC) populations because relic galaxies are expected to host much more red GC populations than blue GCs. To date, however, NGC 1277 is the only MCEG that was revealed as a true relic galaxy with a single red GC population. To find more relic galaxies, we analyzed HST/WFC3 F814W(I)/F160W(H) images of 12 nearby MCEGs. We find that the red GC fractions of our sample MCEGs are larger than those of giant elliptical galaxies on average. However, these values are not as large as the value for NGC 1277. The (I - H) color derived from the HST data is not as sensitive as optical color, so the red GC fractions based on (I - H) color may be a lower limit. To solve the issue, we obtained deep Gemini/GMOS-N g'r'i' images of a nearby MCEG NGC 1270 to examine its GC distributions. In (g - i) color distributions, we estimate the red GC fraction of NGC 1270 f(RGC)=0.63+/-0.07. Although this value is not as large as the value for NGC 1277, it is much larger than the values for giant elliptical galaxies. We conclude that NGC 1270 is indeed a relic galaxy, and we expect that the other MCEGs are also strong candidates for relic galaxies like NGC 1277 and NGC 1270.

 

황호성 (Ho Seong Hwang)        KASI        

An MMT/Hectospec survey of mid-infrared detected galaxies in the AKARI North Ecliptic Pole region        

Thanks to the continuous coverage of AKARI photometric bands at the near-/mid-infrared wavelengths from 2 micron to 24 micron, the AKARI provides unique data sets for studying the emission features including PAHs and AGN dust of dusty galaxies. We have been conducting an MMT/Hectospec spectroscopic survey of AKARI 9 micron selected galaxies in the North Ecliptic Pole Wide field (NEP-Wide), covering a 5.4 deg^2 region of the northern sky, to study the star formation and nuclear activity of dusty galaxies and its environmental dependence at intermediate redshifts (z < 0.6). We present the current progress of the survey, and preview science highlights in combination with other multiwavelength data sets.

 

======================== 20th Nov. 2020 (Fri) ========================

 

Session: Gemini  (Chair: Narae Hwang)

 

John Blakeslee        Gemini Observatory

A Sampling of Recent Science Results from the Gemini Partnership

 

Scot Kleinman        Gemini Observatory

Current and Future Instrumentation at Gemini

With a concentration on future instrumentation coming to the Gemini telescopes, I will provide a brief overview of the current and in-progress instruments at Gemini Observatory.

 

양성철 (Soung-Chul Yang)        KASI

Korea Gemini Office Operation

 

André-Nicolas Chené        Gemini Observatory        

User Support update (in collaboration with Soung-Chul)        

User support refresher (who can help you), user feedback (what we have heard, learned, and improved).

 

Kathleen Labrie        NOIRLab/Gemini Observatory        

Introduction to DRAGONS        

The new Gemini data reduction platform DRAGONS (Data Reduction for Astronomy from Gemini Observatory North and South) will be briefly introduced to the users.

 

 

Session: K-GMT Science 3 - Cosmology/Galaxy Cluster (Chair: Ho Seong Hwang)

 

강이정 (Yijung Kang)        Gemini Observatory/NSF's NOIRLab

Correlation between Hubble Residual of Type Ia Supernovae and the Stellar Population Age of Their Early-type Host Galaxies

The most direct evidence for the presence of dark energy is provided by the distance measurement of SNe Ia. This result is based on the assumption that the corrected brightness of SN Ia through the empirical standardization would not evolve with look-back time. Recent studies have shown, however, that the standardized brightness of SN Ia is correlated with host morphology, host mass, and local star formation rate, suggesting a possible correlation with stellar population property. In order to understand the origin of these correlations, we have continued our spectroscopic observations to cover most of the reported nearby early-type host galaxies. From high-quality (S/N ~175) spectra, we obtained stellar population age and metallicity for these host galaxies. In this presentation, we will present our results reported in the latest paper. At first, we found a significant correlation between Hubble residual and stellar population age at a 99.5% confidence level. Based on this result, we further suggested that the previously reported correlations with host morphology, host mass, and local SFR are most likely originated from the difference in population age. Notably, taken at face values, a significant fraction of the Hubble residual used in the discovery of the dark energy could be affected by the luminosity evolution. Together with this result, we will also introduce our future projects briefly.

 

Kyle Finner        Yonsei University        

Probing the Galaxy Populations of Merging Galaxy Clusters from Filaments to the Core        

Cosmological models predict galaxy clusters are linked to the large scale structure by a series of cosmic web filaments. Most previous studies of galaxy clusters focus on cluster members only and neglect the surrounding environment. The merging cluster sample provides an ideal sample of clusters to study the connection of filaments. Utilizing the large field of view of MMT Hectospec, we are mapping the galaxies around merging clusters. These galaxies will be connected to the ongoing merging activity in the clusters that is revealed through radio, X-ray, and weak-lensing analysis. I will present the current status of our Hectospec project and the results for Abell 521 and Abell 1240

 

손주비 (Jubee Sohn)        Center for Astrophysics | Harvard & Smithsonian

Massive Cluster Surveys with Hectospec: Lesson from A2029

MAssive Cluster surveys with Hectospec (MACH) is an extremely dense survey of the seven most massive clusters within 0.05 < z < 0.09. Each MACH cluster includes a complete magnitude-limited sample of 3,500 - 5,000 redshifts within 40' of each cluster center. MACH clusters also have deep imaging from CTIO/DECam and Subaru/HSC observations enabling weak lensing analysis. A2029 is one of the MACH clusters that has a record number of ~1200 spectroscopic members. Based on this dense spectroscopy along with X-ray and weak lensing data, we study the mass accretion history and the future of the system. A2029 will accrete ~60% of its mass within 2-3 Gyrs, which is comparable with the maximum accretion expected from N-body simulations. This dense spectroscopy also enables a spectroscopic tomographic detection of the galaxy cluster based only on spectroscopically determined background galaxies, which is the first of its kind. I will discuss the importance of a dense spectroscopic survey in understanding the evolution of galaxy clusters.

 

 

Session: K-GMT Science - AGN/BH (Chair: Minjin Kim)

 

김도형 (Dohyeong Kim)                부산대학교        

A possible merging SMBH system at the center of a red AGN 1659+1834        

Galaxy mergers are expected to produce merging supermassive black holes (SMBHs) in close-separation, but the detection of such SMBHs has been difficult. 2MASS J165939.7+183436 is a red active galactic nucleus (AGN) that is a prospective merging SMBH candidate owing to its merging features in Hubble Space Telescope imaging and double-peaked broad emission lines (BELs). Herein, we report a Gemini Multi-Object Spectrograph Integral Field Unit observation of a double-peaked broad Hα line of 2MASS J165939.7+183436. Furthermore, we confirm the existence of two BEL peaks that are kinematically separated by 3000km/s, with the SMBH of each BEL component weighing at 10^(8.92±0.06) and 10^(7.13±0.06) solar mass, if they arise from independent BELs near the two SMBHs. The BEL components were not separated at > 0.1"; however, under several plausible assumptions regarding the fitting of each spaxel, the two components are found to be spatially separated at 0.085" (∼ 250pc). Different assumptions for the fitting can lead to a null (< 0.05") or a larger spatial separation (∼ 0.15"). Given the uncertainty regarding the spatial separation, various models, such as the disk emitter and multiple SMBH models, are viable solutions to explain the double BEL components. These results will promote future research for finding more merging SMBH systems in red AGNs, and higher-resolution imaging validates these different models.

 

김용정 (Yongjung Kim)        KIAA at Peking University        

Hunting for Faint High-redshift Quasars with Infrared Medium-deep Survey        

Faint quasars are known to be the potentially important contributors to the ultraviolet ionizing background in the post-reionization era. However, their number density has not been well determined, making it difficult to assess their role in the early ionization of the intergalactic medium (IGM). In this talk, I will present the updated results of our high-redshift quasar survey using the Infrared Medium-deep Survey (IMS), a near-infrared imaging survey covering an area of 85 square degree. So far, we identified more than 20 faint quasars with M1450<= -23 mag at z ~ 5, mainly using the Gemini Multi-Object Spectrograph (GMOS) on the Gemini 8 m Telescopes, supported by the K-GMT science group at Koran Astronomy and Space Science Institute (KASI). With these IMS quasars, we derived the quasar luminosity functions (QLFs) at z ~ 5. The number density of the faint quasars from the QLFs gives low ionizing emissivity and ionizing photon density by quasars. These results imply that quasars are responsible for only 1-20% of the photons required to completely ionize the IGM at z ~ 5, disfavoring the idea that quasars along could have ionized the IGM at z ~ 5.

 

조호진 (Hojin Cho)        Seoul National University        

Spectroscopic Reverberation Mapping of the Intermediate-Mass AGN in NGC 4395        

NGC 4395 harbors the least luminous active galactic nucleus (AGN) known so far, which is powered by an intermediate-mass black hole (IMBH). Despite being only 4 Mpc away, there has been no reliable measurement of spectroscopic reverberation mapping on its Balmer broad lines, leaving its broad line region (BLR) size -- and consequently its mass -- uncertain. Here, we present our latest reverberation mapping results on NGC 4395. We carried out 3 nights of spectroscopic monitoring observations in 2019, one using GMOS-IFU and the other two using Keck/LRIS MOS. We present the main results including the feasibility of spectroscopic measurements, as well as the advantages of the IFU observations. We will discuss its mass and the black hole scaling relations.