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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.
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>
DETECTION OF THE COSMIC FAR-INFRARED BACKGROUND IN AKARI DEEP FIELD SOUTH
Matsuura, S.,Shirahata, M.,Kawada, M.,Takeuchi, T. T.,Burgarella, D.,Clements, D. L.,Jeong, W.-S.,Hanami, H.,Khan, S. A.,Matsuhara, H.,Nakagawa, T.,Oyabu, S.,Pearson, C. P.,Pollo, A.,Serjeant, S.,Taka IOP Publishing 2011 The Astrophysical journal Vol.737 No.1
<P>We report new limits on the absolute brightness and spatial fluctuations of the cosmic infrared background (CIB) via the AKARI satellite. We carried out observations at 65, 90, 140, and 160 mu m as a cosmological survey in AKARI Deep Field South, which is one of the lowest cirrus regions with a contiguous area of the sky. After removing bright galaxies and subtracting zodiacal and Galactic foregrounds from the measured sky brightness, we successfully measured the CIB brightness and its fluctuations across a wide range of angular scales, from arcminutes to degrees. The measured CIB brightness is consistent with previous results reported from COBE data, but significantly higher than the lower limits at 70 and 160 mu m obtained via Spitzer from the stacking analysis of selected 24 mu m sources. The discrepancy with the Spitzer result is possibly due to a new galaxy population at high redshift obscured by hot dust or unknown diffuse emission. From a power spectrum analysis at 90 mu m, two components were identified: the CIB fluctuations with shot noise due to individual galaxies in a small angular scale from the beam size up to 10 arcminutes, and Galactic cirrus emission dominating at the largest angular scales of a few degrees. The overall shape of the power spectrum at 90 mu m is very similar to that at longer wavelengths, as observed by Spitzer and the Balloon-borne Large-Aperture Submillimeter Telescope (BLAST). Our power spectrum, with an intermediate angular scale of 10-30 arcminutes, gives a firm upper limit for galaxy clustering, which was found by Spitzer and BLAST. Moreover, the color of the CIB fluctuations, which is obtained by combining our data with the previous results, is as red as ultra-luminous infrared galaxies at high redshift. These galaxies are not likely to provide the majority of the CIB emission at 90 mu m, but are responsible for the fluctuations. Our results provide new constraints on the evolution and clustering properties of distant infrared galaxies and any diffuse emission from the early universe.</P>