• Publications of The Korean Astronomical Society
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• v.27 no.4
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• pp.249-252
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• 2012

The absorption features due to interstellar ices, especially $H_2O$ and $CO_2$ ices, provide us with crucial information on present and past interstellar environments, and thus the evolutionary histories of galaxies. Before AKARI, however, few detections of ices were reported for nearby galaxies. The AKARI's unique capability of near-infrared spectroscopy with high sensitivity enables us to systematically study ices in nearby galaxies. Thus we have explored many near-infrared spectra ($2.5-5{\mu}m$) of the 211 pointed observations, searching for the absorption features of ices. As a result, out of 122 nearby galaxies, we have significantly detected $H_2O$ ice from 36 galaxies and $CO_2$ ice from 9 galaxies. It is notable that the ices are detected not only in late-type galaxies but also in early-type galaxies. We find that $CO_2$ ice is more compactly distributed near the galactic center than $H_2O$ ice. Finally, we suggest that the gas density of a molecular cloud and UV radiation may be important factors to determine the abundance of ices.

• Publications of The Korean Astronomical Society
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• v.27 no.4
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• pp.357-360
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• 2012

This paper presents $H{\alpha}$ emission line detections for four galaxies at z > 3.5 made with AKARI as part of the FUHYU mission program. These are the highest-redshift $H{\alpha}$ detections to date in star-forming galaxies. AKARI's unique near-infrared spectroscopic capability has made these detections possible. For two of these galaxies, this represents the first evidence of their redshifts and confirms their physical association with a companion radio galaxy. The star formation rates (SFRs) estimated from the $H{\alpha}$ lines under-predict the SFRs estimated from their far-infrared luminosities by a factor of ~ 2 - 3. We have also detected broad $H{\alpha}$ components in the two radio galaxies which indicate the presence of quasars.

• Publications of The Korean Astronomical Society
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• v.32 no.1
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• pp.313-315
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• 2017

We present physical properties of $24{\mu}m$ galaxies detected by AKARI and Spitzer and their evolution between redshifts 0.4 < z < 2. Using multi-wavelength data from X-ray to radio observations in NEP Deep Field (for AKARI) and Subaru/XMM-Newton Deep Field (for Spitzer), we derive photometric redshift, stellar mass, star-formation rate (SFR), dust extinction magnitude and rest-frame luminosities/colors of the $24{\mu}m$ galaxies from photometric SED fitting. We infer the SFRs from rest-frame ultraviolet luminosity and total infrared luminosity calibrated against Herschel photometric data. For both survey fields, we obtain complete samples with stellar mass of > $10^{10}M_{\odot}$ and SFR of > $30M_{\odot}/yr$ up to z = 2. We find that specific SFRs evolves with redshift at all stellar masses in NON-power-law galaxies (non-PLGs) as star-formation dominant luminous infrared galaxies (LIRGs). The correlations between specific SFR and stellar mass in the Spitzer and AKARI galaxy samples are well consistent with trends of the main sequence galaxies. We also discuss nature of PLGs and their evolution.

• Journal of The Korean Astronomical Society
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• v.36 no.3
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• pp.159-165
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• 2003

Optical (R) and near-infrared (K') images of the IRAS 1-Jy sample of 118 ultraluminous infrared galaxies have been studied. All but one object in the 1-Jy sample show signs of strong tidal interaction/merger. Most of them harbor a single disturbed nucleus and are therefore in the later stages of a merger event. Single-nucleus ULIGs show a broad distribution in host magnitudes with significant overlap with those of quasars. The same statement applies to R - K' colors in ULIG and quasar hosts. An analysis of the surface brightness profiles of the host galaxies in single-nucleus sources reveals that about $35\%$ of the Rand K' surface brightness profiles are well fit by an elliptical-like $R^{1/4}$-law, while only $2\%$ are well fit by an exponential disk. Another $38\%$ of the single-nucleus systems are fit equally well with an exponential or de Vaucouleurs profile. Elliptical-like hosts are most common among merger remnants with Seyfert 1 nuclei ($83\%$) and Seyfert 2 optical characteristics ($69\%$). The mean effective radius of these ULIGs is 4.80 $\pm$ 1.37 kpc at Rand 3.48 $\pm$ 1.39 kpc at K'. These values are in excellent agreement with recent quasar measurements obtained at H with HST. The hosts of elliptical-like 1-Jy systems follow with some scatter the same ${\mu}e - r_e$ relation, giving credence to the idea that some of these objects may eventually become elliptical galaxies if they get rid of their excess gas or transform this gas into stars.

• The Bulletin of The Korean Astronomical Society
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• v.36 no.2
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• pp.66.1-66.1
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• 2011

E+A galaxies are interpreted as post-starburst systems because of strong Balmer absorption lines but any emission lines indicating the lack of current star formation activities, thus they are one of key populations for understanding how star formation activities evolve in galaxies. We present mid-infrared (MIR) spectral energy distributions of E+A galaxies using the Wide-field Infrared Survey Explorer (WISE) preliminary released data. Furthermore, we investigate the role of environment with respect to the MIR properties of E+A galaxies.

• Publications of The Korean Astronomical Society
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• v.27 no.4
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• pp.325-329
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• 2012

We will report our recent study on the properties of more than 1,600 galaxies detected by the AKARI All-Sky Survey with physical quantities based on optical and 21-cm observations, to understand the physics determining the infrared spectral energy distribution (Totani et al., 2011). We discover a tight linear correlation for normal star-forming galaxies between the radiation field strength of dust heating (corresponding to dust temperature) and the galactic-scale infrared radiation field, $L_{TIR}/R^2$. This is the tightest correlation of dust temperature ever known, and the dispersion along the mean relation is 13% in dust temperature. This relation can be explained physically by a thin layer of heating sources embedded in a thicker, optically-thick dust screen. We also find that the number of galaxies sharply drops when galaxies become optically thin against dust-heating radiation, indicating that a feedback process to galaxy formation (e.g., by the photoelectric heating) is working when dust-heating radiation is not self-shielded on a galactic scale. We discuss implications from these findings for the $M_{H_I}$ -size relation, the Kennicutt-Schmidt relation, and galaxy formation in the cosmological context.

• The Bulletin of The Korean Astronomical Society
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• v.46 no.1
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• pp.27.2-27.2
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• 2021

The unknown excess emission in the near-infrared is thought to be related to the evolution of galaxies in the early epoch of Universe. Due to its extremely faint brightness, it can be observed only in space. Many infrared space missions have been tried to trace the origin of the Cosmic Infrared Background through the measurement of its absolute brightness and its spatial fluctuation. In addition, the infrared observations can address questions ranging from the origin of first galaxies in the Universe to the formation of stars. I will overview the Korean infrared space missions and introduce the status of the recent international collaboration mission, SPHEREx.

• The Bulletin of The Korean Astronomical Society
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• v.36 no.1
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• pp.60.1-60.1
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• 2011

We present preliminary results of a statistical study on star formation history of infrared luminous galaxies selected from a IRAS-SDSS matched sample. We derive their star formation histories by comparing observed optical spectra and stellar population synthetic model templates. We find that young population fraction (<500 Myr) increases with infrared luminosity, while AGN-host (based on optical line ratios) galaxies show an enhancement of star formation at intermediate age (around 1 Gyr) compared with starburst galaxies. These results support that infrared luminosity is dominated by starburst activity and that there is an evolutionary connection from starburst to AGN.

• Publications of The Korean Astronomical Society
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• v.27 no.4
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• pp.295-296
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• 2012

We provide a new physical insight on the hot molecular clouds near the nucleus of the heavily obscured AGN IRAS 01250+2832, based on the results of near-infrared high-resolution spectroscopy of gaseous CO ro-vibrational absorption lines with Subaru/IRCS. The detected CO absorption lines up to highly excited rotational levels reveal that hot dense molecular clouds exist around the AGN under the peculiar physical conditions.

• Publications of The Korean Astronomical Society
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• v.32 no.1
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• pp.299-303
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• 2017

We crossmatch AKARI all-sky survey with the Sloan Digital Sky Survey Data Release 10 (SDSS DR10) and the Final Data Release of the Two-Degree Field Galaxy Redshift Survey (2dFGRS) and identify 118 Ultraluminous Infrared Galaxies (ULIRGs) and one Hyperluminous Infrared Galaxy (HLIRG). We find 40 new ULIRGs and one new HLIRG. ULIRGs in our sample are interacting galaxies or ongoing/post mergers. This is consistent with the fact that ULIRGs are major mergers of disk galaxies. We find that compared to local star forming SDSS galaxies of similar mass, local ULIRGs have lower oxygen abundances and this is consistent with the previous studies.