• 천문학회보
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• 제46권2호
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• pp.70.1-70.1
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• 2021

We examine the HI gas kinematics and distributions of galaxy pairs in group or cluster environments from high-resolution Australian Square Kilometer Array Pathfinder (ASKAP) WALLABY pilot observations. We use 32 well-resolved close pair galaxies from the Hydra, Norma, and NGC 4636, two clusters and a group of which are identified by their spectroscopy information and additional visual inspection. We perform profile decomposition of HI velocity profiles of the galaxies using a new tool, BAYGAUD which allows us to separate a line-of-sight velocity profile into an optimal number of Gaussian components based on Bayesian MCMC techniques. Then, we construct super profiles via stacking of individual HI velocity profiles after aligning their central velocities. We fit a model which consists of double Gaussian components to the super profiles, and classify them as kinematically cold and warm HI gas components with respect to their velocity dispersions, narrower or wider 𝜎, respectively. The kinematically cold HI gas reservoir (M_cold/M_HI) of the paired galaxies is found to be relatively higher than that of unpaired control samples in the clusters and the group, showing a positive correlation with the HI mass in general. Additionally, we quantify the gravitational instability of the HI gas disk of the sample galaxies using their Toomre Q parameters and HI morphological disturbances. While no significant difference is found for the Q parameter values between the paired and unpaired galaxies, the paired galaxies tend to have larger HI asymmetry values which are derived using their moment0 map compared to those of the non-paired control sample galaxies in the distribution.

• 천문학논총
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• 제27권4호
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• pp.221-222
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• 2012

We present the results of far-infrared spectral mapping of the Galactic center region with FIS-FTS, which covered the two massive star-forming clusters, Arches and Quintuplet. We find that two dust components with temperatures of about 20 K and 50 K are required to fit the overall continuum spectra. The warm dust emission is spatially correlated with the [OIII] $88{\mu}m$ emission and both are likely to be associated with the two clusters, while the cool dust emission is more widely distributed without any clear spatial correlation with the clusters. We find differences in the properties of the ISM around the two clusters, suggesting that the star-forming activity of the Arches cluster is at an earlier stage than that of the Quintuplet cluster.

• 천문학논총
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• 제30권2호
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• pp.109-112
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• 2015

We present [$Fe\;{\small{II}}$] ${\lambda}1.257{\mu}m$ spectra toward the interacting binary UY Aur with 0".14 angular resolution, obtained with the Near infrared Integral Field Spectrograph (NIFS) combined with the adaptive optics system Altair of the GEMINI observatory. In the [$Fe\;{\small{II}}$] emission, UY Aur A (primary) is brighter than UY Aur B (secondary). The blueshifted and redshifted emission between the primary and secondary show a complicated structure. The radial velocities of the [$Fe\;{\small{II}}$] emission features are similar for UY Aur A and B: ${\sim}-100km\;s^{-1}$ and ${\sim}+130km\;s^{-1}$ for the blueshifted and redshifted components, respectively. Considering the morphologies of the [$Fe\;{\small{II}}$] emissions and bipolar outflow context, we concluded that UY Aur A drives fast and widely opening outflows with an opening angle of ${\sim}90^{\circ}$ while UY Aur B has micro collimated jets.

• 천문학회보
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• 제37권2호
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• pp.67-67
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• 2012

Exploring the distant universe by observing various astronomical objects and extending knowledge on the cosmos by applying human intuition and reasoning to observations are astronomers' professional activity. Astronomers are the people born under a lucky star since this elegant and beautiful job is their the only duty. Being in the 21st century we astronomers now know that galaxies are holding evolving stars and gas, and distribute in the infinite spacetime in an interesting way revealing the secrets of the beginning of the universe. Cosmic structures such as galaxies, large-scale structures, and cosmic microwave background fluctuations are also the tracers of the expansion of space and the invisible components of the energy contents of the universe. Unlike the past century we are in a situation where integral knowledge on various cosmic structures as well as that on a variety of observational and analysis tools are available to everyone and often required for our special mission. However, my experience made me think that accumulating critical questions on nature driven by curiosity is vital for researchers and far more important than absorbing knowledge from others and books. Transforming one's own question marks to acclamation marks is the reward of our life. That is THE fun.

• 천문학회보
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• 제43권2호
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• pp.57.2-57.2
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• 2018

In astronomical observation, sequential device control and real-time data processing are important to maximize observing efficiency. We have developed series of automatic observing software (KAOS, KHU Automatic Observing Software), e.g. KAOS30 for the 30 inch telescope in the McDonald Observatory and KAOS76 for the 76 cm telescope in the KHAO. The series consist of four packages: the DAP (Data Acquisition Package) for CCD Camera control, the TCP (Telescope Control Package) for telescope control, the AFP (Auto Focus Package) for focusing, and the SMP (Script Mode Package) for automation of sequences. In this poster, we introduce KAOS10 which is being developed for controlling a small telescope such as aperture size of 10 cm. The hardware components are the QHY8pro CCD, the QHY5-II CMOS, the iOptron CEM 25 mount, and the Stellarvue SV102ED telescope. The devices are controlled on ASCOM Platform. In addition to the previous packages (DAP, SMP, TCP), KAOS10 has QLP (Quick Look Package) and astrometry function in the TCP. QHY8pro CCD has RGB Bayer matrix and the QLP transforms RGB images into BVR images in real-time. The TCP includes astrometry function which adjusts the telescope position by comparing the image with a star catalog. In the future, We expect KAOS10 be used on the research of transient objects such as a variable star.

• 천문학회보
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• 제46권1호
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• pp.34.2-34.2
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• 2021

SPT-CL J2106-5844 is the most massive galaxy cluster at z>1 discovered to date. It has been known to be an isolated system with a singular, well-defined halo. However, recent studies provide lines of evidence for its merging state. We strengthen the case with the multi-wavelength observations from ALMA, ACA, ASKAP, ATCA, and Chandra. With the sensitive, high resolution ALMA+ACA observations, we reconstruct the ICM pressure map from the thermal SZ effect. It reveals two main gas components that are associated with the mass clumps inferred from the weak-lensing analysis. Furthermore, the X-ray hardness map supports the bimodal gas distribution. With these multi-wavelength data, we probe the merger phase in SPT-CL J2106-5844.

• 천문학회보
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• 제40권1호
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• pp.74.3-74.3
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• 2015

We present 2D- photometric decompositions of ~1,200 nearby dwarf galaxies. Our representative sample is derived from 'A catalog of Visually classified galaxies in the Local Universe'(Ann, Seo and Ha APJS,,,2015) of which galaxy morphological types are determined by visual inspection of color images using the Sloan Digital Sky Survey data release 7. In this catalog, dwarf galaxies were divided into 5 subtypes : dS0, dE, dSph, dEbc, dEblue with distinction of the presence of nucleation in dE, dSph, and dS0. The dSph types are less brighter than other types, and galaxies with nuclei are slightly brighter than those with no nuclei in the same types. Sersic index n have a range 1~1.5, and $dE_{un}$ and $dSph_{un}$ galaxies have n less than 1, and $dSph_n$ galaxies have largest values. We performed two-dimensional decomposition of galaxies using GALFIT, and analyzed their structural components, and residual features which are seen in the residual image.

• 천문학논총
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• 제27권4호
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• pp.291-292
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• 2012

We select infrared-luminous galaxies by cross-matching the SDSS spectroscopic sample of galaxies with the WISE all-sky survey catalog. Based on photometric data points covering from SDSS u-band to WISE $22{\mu}m$, their spectral energy distributions (SEDs) are separated into AGN, elliptical, spiral, and irregular galaxy components. The derived luminosities of spiral galaxy and AGN are well correlated with $H{\alpha}$ and [OIII] line luminosities, respectively. Most galaxies are dominated by young stellar populations even for optical AGNs, but at least 10% of optical non-AGNs appear to harbor buried AGNs. The AGN contribution increases dramatically with the total luminosity. These results show that the SED decomposition is successful and is useful to understand the true nature of dusty galaxies.

• 천문학논총
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• 제27권4호
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• pp.287-288
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• 2012

Radio-loud active galaxies have been found to exhibit a close connection to galactic mergers and host galaxy star-formation quenching. We present preliminary results of an optical spectroscopic investigation of the AKARI NEP field. We focus on the population of radio-loud AGN and use photometric and spectroscopic information to study both their star-formation and nuclear activity components. Preliminary results show that radio-AGN are associated with early type, massive galaxies with relatively old stellar populations.

• 천문학회지
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• 제37권5호
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• pp.465-470
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• 2004

I address the issue of nonthermal processes in the large scale structure of the universe. After reviewing the properties of cosmic shocks and their role as particle accelerators, I discuss the main observational results, from radio to $\gamma$-ray and describe the processes that are thought be responsible for the observed nonthermal emissions. Finally, I emphasize the important role of $\gamma$-ray astronomy for the progress in the field. Non detections at these photon energies have already allowed us important conclusions. Future observations will tell us more about the physics of the intracluster medium, shocks dissipation and CR acceleration.