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The AKARI NEP-Deep survey: a mid-infrared source catalogue
Takagi, T.,Matsuhara, H.,Goto, T.,Hanami, H.,Im, M.,Imai, K.,Ishigaki, T.,Lee, H. M.,Lee, M. G.,Malkan, M.,Ohyama, Y.,Oyabu, S.,Pearson, C. P.,Serjeant, S.,Wada, T.,White, G. J. Springer-Verlag 2012 Astronomy and astrophysics Vol.537 No.-
<P>We present a new catalogue of mid-IR sources using the AKARI NEP-Deep survey. The InfraRed Camera (IRC) onboard AKARI has a comprehensive mid-IR wavelength coverage with 9 photometric bands at 2–24?µm. We utilized all of these bands to cover a nearly circular area adjacent to the north ecliptic pole (NEP). We designed the catalogue to include most of sources detected in 7, 9, 11, 15 and 18?µm bands, and found 7284 sources in a 0.67?deg<SUP>2</SUP> area. From our simulations, we estimate that the catalogue is~80 per cent complete to 200µJy at 15–18µm, and ~10 per cent of sources are missed, owing to source blending. Star-galaxy separation is conducted using only AKARI photometry, as a result of which 10 per cent of catalogued sources are found to be stars. The number counts at 11, 15, 18, and 24µm are presented for both stars and galaxies. A drastic increase in the source density is found in between 11 and 15µm at the flux level of~300micro;Jy. This is likely due to the redshifted PAH emission at 8µm, given our rough estimate of redshifts from an AKARI colour–colour plot. Along with the mid-IR source catalogue, we present optical-NIR photometry for sources falling inside a Subaru/Sprime-cam image covering part of the AKARI NEP-Deep field, which is deep enough to detect most of AKARI mid-IR sources, and useful to study optical characteristics of a complete mid-IR source sample.</P>
Stability of the Broad-line Region Geometry and Dynamics in Arp 151 Over Seven Years
Pancoast, A.,Barth, A. J.,Horne, K.,Treu, T.,Brewer, B. J.,Bennert, V. N.,Canalizo, G.,Gates, E. L.,Li, W.,Malkan, M. A.,Sand, D.,Schmidt, T.,Valenti, S.,Woo, J.-H.,Clubb, K. I.,Cooper, M. C.,Crawford American Astronomical Society 2018 The Astrophysical journal Vol.856 No.2
<P>The Seyfert 1 galaxy Arp 151 was monitored as part of three reverberation mapping campaigns spanning 2008-2015. We present modeling of these velocity-resolved reverberation mapping data sets using a geometric and dynamical model for the broad-line region (BLR). By modeling each of the three data sets independently, we infer the evolution of the BLR structure in Arp 151 over a total of 7 yr and constrain the systematic uncertainties in nonvarying parameters such as the black hole mass. We find that the BLR geometry of a thick disk viewed close to face-on is stable over this time, although the size of the BLR grows by a factor of similar to 2. The dynamics of the BLR are dominated by inflow, and the inferred black hole mass is consistent for the three data sets, despite the increase in BLR size. Combining the inference for the three data sets yields a black hole mass and statistical uncertainty of log(10)(M-BH/M-circle dot) = 6.82(-0.09)(+0.09) with a standard deviation in individual measurements of 0.13 dex.</P>
AKARI mid-infrared slitless spectroscopic survey of star-forming galaxies at <i>z</i> ≲ 0.5
Ohyama, Y.,Wada, T.,Matsuhara, H.,Takagi, T.,Malkan, M.,Goto, T.,Egami, E.,Lee, H.-M.,Im, M.,Kim, J.H.,Pearson, C.,Inami, H.,Oyabu, S.,Usui, F.,Burgarella, D.,Mazyed, F.,Imanishi, M.,Jeong, W.-S.,Miya EDP Sciences 2018 Astronomy and astrophysics Vol.618 No.-
<P><I>Context.</I> Deep mid-infrared (MIR) surveys have revealed numerous strongly star-forming galaxies at redshift <I>z</I> ≲ 2. Their MIR fluxes are produced by a combination of continuum and polycyclic aromatic hydrocarbon (PAH) emission features. The PAH features can dominate the total MIR flux, but are difficult to measure without spectroscopy.</P><P><I>Aims.</I> We aim to study star-forming galaxies by using a blind spectroscopic survey at MIR wavelengths to understand evolution of their star formation rate (SFR) and specific SFR (SFR per stellar mass) up to <I>z</I> ≃ 0.5, by paying particular attention to their PAH properties.</P><P><I>Methods.</I> We conducted a low-resolution (<I>R</I> ≃ 50) slitless spectroscopic survey at 5-13 <I>μ</I>m of 9 <I>μ</I>m flux-selected sources (>0.3 mJy) around the north ecliptic pole with the infrared camera (IRC) onboard AKARI. After removing 11 AGN candidates by using the IRC photometry, we identify 48 PAH galaxies with PAH 6.2, 7.7, and 8.6 <I>μ</I>m features at <I>z</I> < 0.5. The rest-frame optical-MIR spectral energy distributions (SEDs) based on CFHT and IRC imaging covering 0.37-18 <I>μ</I>m were produced, and analysed in conjunction with the PAH spectroscopy. We defined the PAH enhancement by using the luminosity ratio of the 7.7 <I>μ</I>m PAH feature over the 3.5 <I>μ</I>m stellar component of the SEDs.</P><P><I>Results.</I> The rest-frame SEDs of all PAH galaxies have a universal shape with stellar and 7.7 <I>μ</I>m bumps, except that the PAH enhancement significantly varies as a function of the PAH luminosities. We identify a PAH-enhanced population at <I>z</I> ≳ 0.35, whose SEDs and luminosities are typical of luminous infrared galaxies. They show particularly larger PAH enhancement at high luminosity, implying that they are vigorous star-forming galaxies with elevated specific SFR. Our composite starburst model that combines a very young and optically very thick starburst with a very old population can successfully reproduce most of their SED characteristics, although we cannot confirm this optically think component from our spectral analysis.</P>
<i>Spitzer</i> Observations of the North Ecliptic Pole
Nayyeri, H.,Ghotbi, N.,Cooray, A.,Bock, J.,Clements, D. L.,Im, M.,Kim, M. G.,Korngut, P.,Lanz, A.,Lee, H. M.,Lee, D. H.,Malkan, M.,Matsuhara, H.,Matsumoto, T.,Matsuura, S.,Nam, U. W.,Pearson, C.,Serje American Astronomical Society 2018 The Astrophysical journal Supplement series Vol.234 No.2
<P>We present a photometric catalog for Spitzer Space Telescope warm mission observations of the North Ecliptic Pole (NEP; centered at R.A. = 18(h)00(m)00(s), decl. = 66(d)33(m)38(s).552). The observations are conducted with IRAC in the 3.6 and 4.5 mu m bands over an area of 7.04 deg(2), reaching 1 sigma depths of 1.29 mu Jy and 0.79 mu Jy in the 3.6 mu m and 4.5 mu m bands, respectively. The photometric catalog contains 380,858 sources with 3.6 and 4.5 mu m band photometry over the full-depth NEP mosaic. Point-source completeness simulations show that the catalog is 80% complete down to 19.7 AB. The accompanying catalog can be used for constraining the physical properties of extragalactic objects, studying the AGN population, measuring the infrared colors of stellar objects, and studying the extragalactic infrared background light.</P>
OVERVIEW OF THE NORTH ECLIPTIC POLE DEEP MULTI-WAVELENGTH SURVEY (NEP-DEEP)
Matsuhara, H.,Wada, T.,Takagi, T.,Nakagawa, T.,Murata, K.,Churei, S.,Goto, T.,Oyabu, S.,Takeuchi, T.T.,Ohyama, Y.,Miyaji, T.,Krumpe, M.,Lee, H.M.,Im, M.,Serjeant, S.,Peason, C.P.,White, G.,Malkan, M.A The Korean Astronomical Society 2012 天文學論叢 Vol.27 No.4
An overview of the North Ecliptic Pole (NEP) deep multi-wavelength survey covering from X-ray to radio wavelengths is presented. The main science objective of this multi-wavelength project is to unveil the star-formation and AGN activities obscured by dust in the violent epoch of the Universe (z=0.5-2), when the star formation and black-hole evolution activities were much stronger than the present. The NEP deep survey with AKARI/IRC consists of two survey projects: shallow wide (8.2 sq. deg, NEP-Wide) and the deep one (0.6 sq. deg, NEP-Deep). The NEP-Deep provides us with a $15{\mu}m$ or $18{\mu}m$ selected sample of several thousands of galaxies, the largest sample ever made at these wavelengths. A continuous filter coverage at mid-IR wavelengths (7, 9, 11, 15, 18, and $24{\mu}m$) is unique and vital to diagnose the contribution from starbursts and AGNs in the galaxies at the violent epoch. The recent updates of the ancillary data are also provided: optical/near-IR magnitudes (Subaru, CFHT), X-ray (Chandra), FUV/NUV (GALEX), radio (WSRT, GMRT), optical spectra (Keck/DEIMOS etc.), Subaru/FMOS, Herschel/SPIRE, and JCMT/SCUBA-2.
SURVEY OF DUSTY ACTIVE GALACTIC NUCLEI BASED ON THE MID-INFRARED ALL-SKY SURVEY CATALOG
Oyabu, S.,Ishihara, D.,Yamada, R.,Kaneda, H.,Yamagishi, M.,Toba, Y.,Matsuhara, H.,Nakagawa, T.,Malkan, M.,Shirahata, M. The Korean Astronomical Society 2012 天文學論叢 Vol.27 No.4
Many observations have found evidence of the presence of a large number of heavily obscured Active Galactic Nuclei (AGNs). However, the nature of this population is only poorly understood because heavy obscuration by dust prevents one from finding them at optical wavelengths. Mid-infrared AGN searches can overcome this obstacle by penetrating through dust and by detecting direct emission from the dust torus. Thus, we can identify most of the AGN population, including type-2 and buried AGNs. Using the AKARI mid-infrared all-sky survey, we performed an AGN search in the nearby universe. Utilizing the 2MASS photometry, we selected mid-infrared-excess sources and carried out near-infrared spectroscopic observations in the AKARI Phase 3. During these follow-up observations, we have found three galaxies that show strong near-infrared red continuum from hot dust with a temperature of about 500 K, but do not show any AGN features in other wavelengths. The most suitable explanation of near-infrared continuum is the presence of central AGNs. Therefore, we conclude that they are AGNs obscured by dust. We performed X-ray observations of the two galaxies with SUZAKU. No detections in the 0.4-10 keV suggest that the column density may be much higher than $N_H=10^{23.5}cm^{-2}$. Comparing the masses of the host galaxies with those of the SDSS AGNs, we find that the host galaxies of the dusty AGNs discovered with AKARI are less massive populations than those of optically selected AGNs.
CHANDRA OBSERVATIONS OF THE AKARI NEP DEEP FIELD
T. Miyaji,M. Krumpe,H. Brunner,T. Ishigaki,H. Hanami,A. Markowitz,T. Takagi,T. Goto,M. A. Malkan,H. Matsuhara,C. Pearson,Y. Ueda,T. Wada 한국천문학회 2017 天文學論叢 Vol.32 No.1
The AKARI NEP Deep Field Survey is an international multiwavelength survey over 0.4 deg$^2$ of the sky. This is the deepest survey made by the InfraRed Camera (IRC) of the infrared astronomical satellite AKARI with 9 filters continuously covering the 2-25 μm range, including three filters in the Spitzer gap between the IRAC and MIPS coverages. This enabled us to make sensitive MIR detection of AGN candidates at z ~ 1, based on hot dust emission in the AGN torus. It is also efficient in detecting highly obscured Compton-thick AGN population. In this article, we report the first results of X-ray observations on this field. The field was covered by 15 overlapping Chandra ACIS-I observations with a total exposure of ~ 300 ks, detecting $\approx 450$ X-ray sources. We utilize rest-frame stacking analysis of the MIR AGN candidates that are not detected individually. Our preliminary analysis shows a marginal detection of the rest-frame stacked Fe K$\alpha$ line from our strong Compton-thick candidates.
NEP-AKARI: EVOLUTION WITH REDSHIFT OF DUST ATTENUATION IN 8 μm SELECTED GALAXIES
V. Buat,N. Oi,D. Burgarella,K. Malek,H. Matsuhara,K. Murata,S. Serjeant,T.T. Takeuchi,M. Malkan,C. Pearson,T. Wada 한국천문학회 2017 天文學論叢 Vol.32 No.1
We built a 8 $\mu$m selected sample of galaxies in the NEP-AKARI field by defining 4redshift bins with the four AKARI bands at 11, 15, 18 and 24 microns (0.15 < z < 0.49,0.75 < z < 1.34, 1.34 < z < 1.7 and 1.7 < z < 2.05) . Our sample contains 4079 sources, 599 are securely detected with$Herschel$/PACS. Also adding ultraviolet (UV) data from $GALEX$, we fit the spectral energy distributions using the physically motivated codeCIGALE to extract the star formation rate, stellar mass, dustattenuation and the AGN contribution to the total infrared luminosity ($L_{\rm IR}$). We discuss the impact of the adoptedattenuation curve and that of the wavelength coverage to estimate these physical parameters. We focus on galaxies with a luminosity close the characteristic $L_{\rm IR}^*$ in the different redshift bins to studythe evolution with redshift of the dust attenuation in these galaxies.
FAR INFRARED GALAXIES IN AKARI'S EYE
Malek, K.,Pollo, A.,Takeuchi, T.T.,Giovannoli, E.,Buat, V.,Burgarella, D.,Malkan, M. The Korean Astronomical Society 2012 天文學論叢 Vol.27 No.4
We present the results of Spectral Energy Distribution (SED) fitting of far-infrared galaxies detected in the AKARI Deep Field-South (ADF-S) Survey and discuss their physical properties. Additionally, we perform a comparison between photometric redshifts estimated using only optical and both optical and infrared data. We conclude that our sample consists mostly of nearby galaxies rich in dust and young stars. We observe an improvement in the estimation of photometric redshifts when the IR data are included, comparing to a standard approach based mainly on the optical to UV photometry.