arXiv subjects

Joon Hyeop Lee

Publications and source records attributed to Joon Hyeop Lee.

At least 37 records · Page 2Linked to original sources

arXiv2020

Small-Scale Dynamical Coherence Accompanied with Galaxy Conformity

The discovery of the coherence between galaxy rotation and neighbor motion in 1-Mpc scales has been reported recently. Following up the discovery, we investigate whether the neighbors in such dynamical coherence also present galaxy conformity, using the Calar Alto Legacy Integral Field Area Survey (CALIFA) data and the NASA-Sloan Atlas (NSA) catalog. We measure the correlation coefficient of g - r colors between the CALIFA galaxies and their neighbors, as a quantitative indicator of galaxy conformity. The neighbors are divided into coherently moving and anti-coherently moving ones, the correlation coefficients from which are compared with each other, in various bins of relative luminosity and projected distance. In most cases, the CALIFA galaxies and their neighbors show positive correlation coefficients in g - r color, even for the anti-coherent neighbors. However, we find statistically significant (2.6-sigma) difference between coherent and anti-coherent neighbors, when the neighbor galaxies are bright (Delta Mr <= -1.0) and close (D <= 400 kpc). That is, when they are bright and close to the CALIFA galaxies, the coherently moving neighbors show stronger conformity with the CALIFA galaxies than the anti-coherently moving neighbors. This result supports that the small-scale dynamical coherence may originate from galaxy interactions as galaxy conformity is supposed to do, which agrees with the conclusion of the previous study.

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arXiv2020

KMTNet Nearby Galaxy Survey II. Searching for Dwarf Galaxies in Deep and Wide-field Images of the NGC 1291 system

We present newly discovered dwarf galaxy candidates in deep and wide-field images of NGC 1291 obtained with the Korea Microlensing Telescope Network. We identify 15 dwarf galaxy candidates by visual inspection. Using imaging simulations, we demonstrate that the completeness rate of our detection is greater than 70% for the central surface brightness value of $μ_{0,R}\lesssim26$ mag arcsec$^{-2}$ and for magnitudes $M_R\lesssim-10$ mag. The structural and photometric properties of the dwarf galaxy candidates appear to be broadly consistent with those of ordinary dwarf galaxies in nearby groups and clusters, with $μ_{0,R}\sim$ 22.5 to 26.5 mag arcsec$^{-2}$ and effective radii of 200 pc to 1 kpc. The dwarf galaxy candidates show a concentration towards NGC 1291 and tend to be redder the closer they are to the center, possibly indicating that they are associated with NGC 1291. The dwarf candidates presented in this paper appear to be bluer than those in denser environments, revealing that the quenching of star formation in dwarf galaxies is susceptible to the environment, while the morphology shaping is not.

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arXiv2019

Mysterious Coherence in Several-Megaparsec Scales Between Galaxy Rotation and Neighbor Motion

In our recent report, observational evidence supports that the rotational direction of a galaxy tends to be coherent with the average motion of its nearby neighbors within 1 Mpc. We extend the investigation to neighbors at farther distances, in order to examine if such dynamical coherence is found even in large scales. The Calar Alto Legacy Integral Field Area (CALIFA) survey data and the NASA-Sloan Atlas (NSA) catalog are used. From the composite map of velocity distribution of 'neighbor' galaxies within 15 Mpc from the CALIFA galaxies, the composite radial profiles of the luminosity-weighted mean velocity of neighbors are derived. These profiles show unexpectedly strong evidence of the dynamical coherence between the rotation of the CALIFA galaxies and the average line-of-sight motion of their neighbors within several Mpc distances. Such a signal is particularly strong when the neighbors are limited to red ones: the luminosity-weighted mean velocity at 1 < D <= 6 Mpc is as large as 30.6+/-10.9 km/s (2.8-sigma significance to random spin-axis uncertainty) for central rotation (R <= Re). In the comparison of several subsamples, the dynamical coherence tends to be marginally stronger for the diffuse or kinematically-well-aligned CALIFA galaxies. For this mysterious coherence in large scales, we cautiously suggest a scenario that it results from a possible relationship between the long-term motion of a large-scale structure and the rotations of galaxies in it.

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arXiv2019

Impact of Galaxy Mergers on the Colours of Cluster Galaxies

We examine the ultraviolet and optical colours of 906 cluster galaxies from the KASI-Yonsei Deep Imaging Survey of Clusters (KYDISC). Galaxies have been divided into two categories, morphologically-disturbed and undisturbed galaxies, based on the visual signatures related to recent mergers. We find that galaxies with signatures of recent mergers show significantly bluer colours than undisturbed galaxies. Disturbed galaxies populate more on the cluster outskirts, suggesting recent accretion into the cluster environment, which implies that disturbed galaxies can be less influenced by the environmental quenching process and remain blue. However, we still detect bluer colours of disturbed galaxies in all locations (cluster core and outskirts) for the fixed morphology, which is difficult to understand just considering the difference in time since infall into a cluster. Moreover, blue disturbed galaxies show features seemingly related to recent star formation. Therefore, we suspect that mergers make disturbed galaxies keep their blue colour longer than undisturbed galaxies under the effect of the environmental quenching through either merger-induced star formation or central gas concentration which is less vulnerable for gas stripping.

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arXiv2019

Stellar populations of nine passive spiral galaxies from the CALIFA survey: are they progenitors of S0s?

We investigate the stellar population properties of passive spiral galaxies in the CALIFA survey. Nine spiral galaxies that have NUV-r > 5 and no/weak nebular emission lines in their spectra are selected as passive spirals. Our passive spirals lie in the redshift range of 0.001 < z < 0.021 and have stellar mass range of 10.2 < log(M_{\star}/M_{\odot}) < 10.8. They clearly lie in the domain of early-type galaxies in the WISE IR color-color diagram. We analyze the stellar populations out to two effective radius, using the best-fitting model to the measured absorption line-strength indices in the Lick/IDS system. We find that stellar populations of the passive spirals span a wide range, even in their centers, and hardly show any common trend amongst themselves either. We compare the passive spirals with S0s selected in the same mass range. S0s cover a wide range in age, metallicity, and [a/Fe], and stellar populations of the passive spirals are encompassed in the spread of the S0 properties. However, the distribution of passive spirals are skewed toward higher values of metallicity, lower [a/Fe], and younger ages at all radii. These results show that passive spirals are possibly related to S0s in their stellar populations. We infer that the diversity in the stellar populations of S0s may result from different evolutionary pathways of S0 formation, and passive spirals may be one of the possible channels.

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arXiv2019

Galaxy Rotation Coherent with the Motions of Neighbors: Discovery of Observational Evidence

We present our discovery of observational evidence for the coherence between galaxy rotation and the average line-of-sight motion of neighbors. We use the Calar Alto Legacy Integral Field Area (CALIFA) survey data analyzed with the Python CALIFA STARLIGHT Synthesis Organizer (PyCASSO) platform, and the NASA-Sloan Atlas (NSA) catalog. After estimating the projected angular momentum vectors of 445 CALIFA galaxies, we build composite maps of their neighbor galaxies on the parameter space of line-of-sight velocity versus projected distance. The composite radial profiles of the luminosity-weighted mean velocity of neighbors show striking evidence for dynamical coherence between the rotational direction of the CALIFA galaxies and the average moving direction of their neighbor galaxies. The signal of such dynamical coherence is significant for the neighbors within 800 kpc distance from the CALIFA galaxies, for which the luminosity-weighted mean velocity is as large as 61.7+/-17.6 km/s (3.5-sigma significance to bootstrap uncertainty) when the angular momentum is measured at R_e<R<=2R_e of each CALIFA galaxy. In the comparison of the subsamples, we find that faint, blue or kinematically misaligned galaxies show stronger coherence with neighbor motions than bright, red or kinematically well-aligned galaxies do. Our results indicate that (1) the rotation of a galaxy (particularly at its outskirt) is significantly influenced by interactions with its neighbors up to 800 kpc, (2) the coherence is particularly strong between faint galaxies and bright neighbors, and (3) galaxy interactions often cause internal kinematic misalignment or possibly even kinematically distinct cores.

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arXiv2018

KMTNet Nearby Galaxy Survey I. : Optimal strategy for low surface brightness imaging with KMTNet

In hierarchical galaxy formation models, galaxies evolve through mergers and accretions. Tidally-disrupted debris from these processes can remain as diffuse, faint structures, which can provide useful insight into the assembly history of galaxies. To investigate the properties of the faint structures in outskirts of nearby galaxies, we conduct deep and wide-field imaging survey with KMTNet. We present our observing strategy and optimal data reduction process to recover the faint extended features in the imaging data of NGC 1291 taken with KMTNet. Through the dark sky flat-fielding and optimal sky subtraction, we can effectively remove inhomogeneous patterns. In the combined images, the peak-to-peak global sky gradients were reduced to less than $\sim0.5$% and $\sim0.3$% of the original $B$- and $R$-band sky levels, respectively. However, we find local spatial fluctuations in the background sky which can affect the precise measurement of the sky value. Consequently, we can reach the surface brightness of $μ_{B,1σ} \sim$ 29.5 and $μ_{R,1σ}\sim$ 28.5 mag arcsec$^{-2}$ in azimuthally averaged one-dimensional surface brightness profiles, that is mainly limited by the uncertainty in the sky determination. These results suggest that the deep imaging data produced by KMTNet are suitable to study the faint features of nearby galaxies such as outer disks and dwarf companions, but unideal (not impossible) to detect stellar halos. The one-dimensional profile revealed that NGC 1291 appeared to have Type I disk out to $R$ $\sim$ 30 kpc with no obvious color gradient and excess light due to a stellar halo was undetected.

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arXiv2018

JINGLE, a JCMT legacy survey of dust and gas for galaxy evolution studies: I. Survey overview and first results

JINGLE is a new JCMT legacy survey designed to systematically study the cold interstellar medium of galaxies in the local Universe. As part of the survey we perform 850um continuum measurements with SCUBA-2 for a representative sample of 193 Herschel-selected galaxies with M*>10^9Msun, as well as integrated CO(2-1) line fluxes with RxA3m for a subset of 90 of these galaxies. The sample is selected from fields covered by the Herschel-ATLAS survey that are also targeted by the MaNGA optical integral-field spectroscopic survey. The new JCMT observations combined with the multi-wavelength ancillary data will allow for the robust characterization of the properties of dust in the nearby Universe, and the benchmarking of scaling relations between dust, gas, and global galaxy properties. In this paper we give an overview of the survey objectives and details about the sample selection and JCMT observations, present a consistent 30 band UV-to-FIR photometric catalog with derived properties, and introduce the JINGLE Main Data Release (MDR). Science highlights include the non-linearity of the relation between 850um luminosity and CO line luminosity, and the serendipitous discovery of candidate z>6 galaxies.

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arXiv2018

Intra-night optical variability of AGN in the COSMOS field with the KMTNet

Active Galactic Nucleus (AGN) variability can be used to study the physics of the region in the vicinity of the central black hole. In this paper, we investigated intra-night optical variability of AGN in the COSMOS field in order to understand the AGN instability at the smallest scale. Observations were performed using the KMTNet on three separate nights for 2.5-5 hour at a cadence of 20-30 min. We find that the observation enables the detection of the short-term variability as small as $\sim$ 0.02 and 0.1 mag for $R \sim$ 18 and 20 mag sources, respectively. Using four selection methods (X-rays, mid-infrared, radio, and matching with SDSS quasars), 394 AGNs are detected in the 4 deg$^2$ field of view. After differential photometry and $χ^2-$test, we classify intra-night variable AGNs. But the fraction of variable AGNs (0-8 %) is consistent with a statistical fluctuation from null result. Eight out of 394 AGNs are found to be intra-night variable in two filters or two nights with a variability level of 0.1 mag, suggesting that they are strong candidates for intra-night variable AGNs. Still they represent a small population (2 %). There is no sub-category of AGNs that shows a statistically significant intra-night variability.

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arXiv2018

KYDISC: Galaxy Morphology, Quenching, and Mergers in the Cluster Environment

We present the KASI-Yonsei Deep Imaging Survey of Clusters (KYDISC) targeting 14 clusters at 0.015 < z < 0.144 using the Inamori Magellan Areal Camera and Spectrograph on the 6.5-meter Magellan Baade telescope and the MegaCam on the 3.6-meter Canada-France-Hawaii Telescope. We provide a catalog of cluster galaxies that lists magnitudes, redshifts, morphologies, bulge-to-total ratios, and local density. Based on the 1409 spectroscopically-confirmed cluster galaxies brighter than -19.8 in the r-band, we study galaxy morphology, color, and visual features generated by galaxy mergers. We see a clear trend between morphological content and cluster velocity dispersion, which was not presented by previous studies using local clusters. Passive spirals are preferentially found in a highly dense region (i.e., cluster center), indicating that they have gone through the environmental quenching. In deep images (mu_r ~ 27 mag/"^2), 20% of our sample show signatures of recent mergers, which is not expected from theoretical predictions and a low frequency of ongoing mergers in our sample (~ 4%). Such a high fraction of recent mergers in the cluster environment supports a scenario that the merger events that made the features have preceded the galaxy accretion into the cluster environment. We conclude that mergers affect a cluster population mainly through the pre-processing on recently accreted galaxies.

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arXiv2018

Color Dispersion as an Indicator of Stellar Population Complexity: Insights from the Pixel Color-Magnitude Diagrams of 32 Bright Galaxies in Abell 1139 and Abell 2589

We investigate the properties of bright galaxies with various morphological types in Abell 1139 and Abell 2589, using the pixel color-magnitude diagram (pCMD) analysis technique. The sample is 32 galaxies brighter than Mr = -21.3 mag with spectroscopic redshifts, which are deeply imaged in the g and r bands using the MegaCam mounted on the Canada-France-Hawaii Telescope. After masking contaminants with two-step procedures, we examine how the detailed properties in pCMDs depend on galaxy morphology and infrared color. The mean g - r color as a function of surface brightness (mu_r) in the pCMD of a galaxy shows fine performance in distinguishing between early- and late-type galaxies, but it is not perfect because of the similarity between elliptical galaxies and bulge-dominated spiral galaxies. On the other hand, the g - r color dispersion as a function of mu_r works better. We find that the best set of parameters for galaxy classification is the combination of the minimum color dispersion at mu_r <= 21.2 mag/arcsec^2 and the maximum color dispersion at 20.0 <= mu_r <= 21.0 mag/arcsec^2: the latter reflects the complexity of stellar populations at the disk component in a typical spiral galaxy. Finally, the color dispersion measurements of an elliptical galaxy appear to be correlated with the WISE infrared color ([4.6] - [12]). This indicates that the complexity of stellar populations in an elliptical galaxy is related with its recent star formation activities. From this observational evidence, we infer that gas-rich minor mergers or gas interactions may have usually happened during the recent growth of massive elliptical galaxies.

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arXiv2017

Pixel Color-Magnitude Diagram Analysis of the Brightest Cluster Galaxies in Dynamically Young and Old Clusters, Abell 1139 and Abell 2589

As a case study to understand the coevolution of Brightest Cluster Galaxies (BCGs) and their host clusters, we investigate the BCGs in dynamically young and old clusters, Abell 1139 (A1139) and Abell 2589 (A2589). We analyze the pixel color-magnitude diagrams (pCMDs) using deep g- and r-band images, obtained from the Canada-France-Hawaii Telescope observations. After masking foreground/background objects and smoothing pixels in consideration of the observational seeing size, detailed pCMD features are compared between the two BCGs. (1) While the overall shapes of the pCMDs are similar to those of typical early-type galaxies, the A2589-BCG tends to have redder mean pixel color and smaller pixel color deviation at given surface brightness than the A1139-BCG. (2) The mean pixel color distribution as a function of pixel surface brightness (pCMD backbone) indicates that the A2589-BCG formed a larger central body (~ 2.0 kpc in radius) by major dry mergers at an early epoch than the A1139-BCG (a central body ~ 1.3 kpc in radius), while they have grown commonly by subsequent minor mergers. (3) The spatial distributions of the pCMD outliers reveal that the A1139-BCG experienced considerable tidal events more recently than the A2589-BCG, whereas the A2589-BCG has an asymmetric compact core possibly resulting from major dry merger at an early epoch. (4) The A2589-BCG shows a very large faint-to-bright pixel number ratio compared to early-type non-BCGs, whereas the ratio for the A1139-BCG is not distinctively large. These results are consistent with the idea that the BCG in the dynamically older cluster (A2589) formed earlier and is relaxed better.

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arXiv2017

BVI Photometric Study of the Old Open Cluster Ruprecht 6

We present a BVI optical photometric study of the old open cluster Ruprecht 6 using the data obtained with the SMARTS 1.0 m telescope at the CTIO, Chile. Its color-magnitude diagrams show the clear existence of the main-sequence stars, of which turn-off point is located around V ~ 18.45 mag and B-V ~ 0.85 mag. Three red clump (RC) stars are identified at V = 16.00 mag, I = 14.41 mag and B-V = 1.35 mag. From the mean Ks-band magnitude of RC stars (Ks=12.39 +- 0.21 mag) in Ruprecht 6 from 2MASS photometry and the known absolute magnitudes of the RC stars (M_Ks = -1.595 +- 0.025 mag), we obtain the distance modulus to Ruprecht 6 (m-M)_0 = 13.84 +- 0.21 mag (d=5.86 +- 0.60 kpc). From the (J-K_s) and (B-V) colors of the RC stars, comparison of the (B-V) and (V-I) colors of the bright stars in Ruprecht 6 with those of the intrinsic colors of dwarf and giant stars, and the PARSEC isochrone fittings, we derive the reddening values of E(B-V) = 0.42 mag and E(V-I) = 0.60 mag. Using the PARSEC isochrone fittings onto the color-magnitude diagrams, we estimate the age and metallicity to be: log (t) =9.50 +- 0.10 (t =3.16 +- 0.82 Gyr) and [Fe/H] = -0.42 +- 0.04 dex. We present the Galactocentric radial metallicity gradient analysis for old (age > 1 Gyr) open clusters of Dias et al. catalog, which likely follow a single relation of [Fe/H] =(-0.034 +- 0.007) R_GC + (0.190 +- 0.080) (rms = 0.201) for the whole radial range or dual relation of [Fe/H] =(-0.077 +- 0.017) R_GC + (0.609 +- 0.161) (rms = 0.152) and constant ([Fe/H] ~ -0.3 dex) value, inside and outside of R_GC ~ 12 kpc, respectively. The metallicity and Galactocentric radius (13.28 +- 0.54 kpc) of Ruprecht 6 obtained in this study seem to be consistent with both of the relations.

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arXiv2017

The dependence of cluster galaxy properties on the central entropy of their host cluster

We present a study of the connection between brightest cluster galaxies (BCGs) and their host galaxy clusters. Using galaxy clusters at $0.1<z<0.3$ from the Hectospec Cluster Survey (HeCS) with X-ray information from the Archive of {\it Chandra} Cluster Entropy Profile Tables (ACCEPT), we confirm that BCGs in low central entropy clusters are well aligned with the X-ray center. Additionally, the magnitude difference between BCG and the 2nd brightest one also correlates with the central entropy of the intracluster medium. From the red-sequence (RS) galaxies, we cannot find significant dependence of RS color scatter and stellar population on the central entropy of the intracluster medium of their host cluster. However, BCGs in low entropy clusters are systematically less massive than those in high entropy clusters, although this is dependent on the method used to derive the stellar mass of BCGs. In contrast, the stellar velocity dispersion of BCGs shows no dependence on BCG activity and cluster central entropy. This implies that the potential of the BCG is established earlier and the activity leading to optical emission lines is dictated by the properties of the intracluster medium in the cluster core.

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arXiv2016

Small-Scale Conformity of the Virgo Cluster Galaxies

We investigate the small-scale conformity in color between bright galaxies and their faint companions in the Virgo cluster. Cluster member galaxies are spectroscopically determined using the Extended Virgo Cluster Catalog (EVCC) and the Sloan Digital Sky Survey Data Release 12 (SDSS DR12). We find that the luminosity-weighted mean color of faint galaxies depends on the color of adjacent bright galaxy as well as on the cluster-scale environment (gravitational potential index). From this result for the entire area of the Virgo cluster, it is not distinguishable whether the small-scale conformity is genuine or is artificially produced due to cluster-scale variation of galaxy color. To disentangle this degeneracy, we divide the Virgo cluster area into three sub-areas so that the cluster-scale environmental dependence is minimized: A1 (central), A2 (intermediate) and A3 (outermost). We find conformity in color between bright galaxies and their faint companions (color-color slope significance S ~ 2.73 sigma and correlation coefficient cc ~ 0.50) in A2, where the cluster-scale environmental dependence is almost negligible. On the other hand, the conformity is not significant or very marginal (S ~ 1.75 sigma and cc ~ 0.27) in A1. The conformity is not significant either in A3 (S ~ 1.59 sigma and cc ~ 0.44), but the sample size is too small in this area. These results are consistent with a scenario in which the small-scale conformity in a cluster is a vestige of infallen groups and these groups lose conformity as they come closer to the cluster center.

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arXiv2014

Measurable Relationship Between Bright Galaxies and Their Faint Companions in WHL J085910.0+294957, a Galaxy Cluster at z = 0.30: Vestiges of Infallen Groups?

The properties of satellite galaxies are closely related to their host galaxies in galaxy groups. In cluster environments, on the other hand, the interaction between close neighbors is known to be limited. Our goal is to examine the relationships between host and satellite galaxies in the harsh environment of a galaxy cluster. To achieve this goal, we study a galaxy cluster WHL J085910.0+294957 at z = 0.30 using deep images obtained with CQUEAN CCD camera mounted on the 2.1-m Otto Struve telescope. After member selection based on the scaling relations of photometric and structural parameters, we investigate the relationship between bright (M_i < -18) galaxies and their faint (-18 < M_i < -15) companions. The weighted mean color of faint companion galaxies shows no significant dependence (< 1 sigma to Bootstrap uncertainties) on cluster-centric distance and local luminosity density as well as the luminosity and concentration of an adjacent bright galaxy. However, the weighted mean color shows marginal dependence (~ 2.2 sigma) on the color of an adjacent bright galaxy, when the sample is limited to bright galaxies with at least 2 faint companions. By using a permutation test, we confirm that the correlation in color between bright galaxies and their faint companions in this cluster is statistically significant with a confidence level of 98.7%. The statistical significance increases if we additionally remove non-members using the SDSS photometric redshift information (~ 2.6 sigma and 99.3%). Our results suggest three possible scenarios: (1) vestiges of infallen groups, (2) dwarf capturing, and (3) tidal tearing of bright galaxies.

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arXiv2012

What determines the sizes of red early-type galaxies?

The sizes of galaxies are known to be closely related with their masses, luminosities, redshifts and morphologies. However, when we fix these quantities and morphology, we still find large dispersions in the galaxy size distribution. We investigate the origin of these dispersions for red early-type galaxies, using two SDSS-based catalogs. We find that the sizes of faint galaxies (log(M_dyn/M_sun) < 10.3 or M_r > -19.5, where M_r is the r-band absolute magnitude, k-corrected to z = 0.1) are affected more significantly by luminosity, while the sizes of bright galaxies (log(M_dyn/M_sun) > 11.4 or M_r < -21.4) are by dynamical mass. At fixed mass and luminosity, the sizes of low-mass galaxies (log(M_dyn/M_sun) ~ 10.45 and M_r ~ -19.8) are relatively less sensitive to their colors, color gradients and axis ratios. On the other hand, the sizes of intermediate-mass (log(M_dyn/M_sun) ~ 10.85 and M_r ~ -20.4) and high-mass (log(M_dyn/M_sun) ~ 11.25 and M_r ~ -21.0) galaxies significantly depend on those parameters, in the sense that larger red early-type galaxies have bluer colors, more negative color gradients (bluer outskirts) and smaller axis ratios. These results indicate that the sizes of intermediate- and high-mass red early-type galaxies are significantly affected by their recent minor mergers or rotations, whereas the sizes of low-mass red early-type galaxies are affected by some other mechanisms. Major dry mergers also seem to have influenced on the size growth of high-mass red early-type galaxies.

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arXiv2012

AKARI Near-Infrared Spectroscopy of Luminous Infrared Galaxies

We present the AKARI near-infrared (NIR; 2.5-5 micron) spectroscopic study of 36 (ultra)luminous infrared galaxies [(U)LIRGs] at z=0.01-0.4. We measure the NIR spectral features including the strengths of 3.3 micron polycyclic aromatic hydrocarbon (PAH) emission and hydrogen recombination lines (Brα. and Brβ), optical depths at 3.1 and 3.4 micron, and NIR continuum slope. These spectral features are used to identify optically elusive, buried AGN. We find that half of the (U)LIRGs optically classified as non-Seyferts show AGN signatures in their NIR spectra. Using a combined sample of (U)LIRGs with NIR spectra in the literature, we measure the contribution of buried AGN to the infrared luminosity from the SED-fitting to the IRAS photometry. The contribution of these buried AGN to the infrared luminosity is 5-10%, smaller than the typical AGN contribution of (U)LIRGs including Seyfert galaxies (10-40%). We show that NIR continuum slopes correlate well with WISE [3.4]-[4.6] colors, which would be useful for identifying a large number of buried AGN using the WISE data.

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