J- and Ks-band Galaxy Counts and Color Distributions in the AKARI North Ecliptic Pole Field

We present the J- and Ks-band galaxy counts and galaxy colors covering 750 square arcminutes in the deep AKARI North Ecliptic Pole (NEP) field, using the FLoridA Multi-object Imaging Near-ir Grism Observational Spectrometer (FLAMINGOS) on the Kitt Peak National Observatory (KPNO) 2.1m telescope. The limiting magnitudes with a signal-to-noise ratio of three in the deepest regions are 21.85 and 20.15 in the J- and Ks-bands respectively in the Vega magnitude system. The J- and Ks-band galaxy counts in the AKARI NEP field are broadly in good agreement with those of other results in the literature, however we find some indication of a change in the galaxy number count slope at J~19.5 and over the magnitude range 18.0 < Ks < 19.5. We interpret this feature as a change in the dominant population at these magnitudes because we also find an associated change in the B - Ks color distribution at these magnitudes where the number of blue samples in the magnitude range 18.5 < Ks < 19.5 is significantly larger than that of Ks < 17.5

Star Formation and AGN activity in Galaxies classified using the 1.6 {\mu}m Bump and PAH features at z=0.4−2z = 0.4-2

We have studied the star-formation and AGN activity of massive galaxies in the redshift range $z=0.4-2$, which are detected in a deep survey field using the AKARI InfraRed (IR) astronomical satellite and {\em Subaru} telescope toward the North Ecliptic Pole (NEP). The AKARI/IRC Mid-InfraRed (MIR) multiband photometry is used to trace their star-forming activities with the Polycyclic-Aromatic Hydrocarbon (PAH) emissions, which is also used to distinguish star-forming populations from AGN dominated ones and to estimate the Star Formation Rate (SFR) derived from their total emitting IR (TIR) luminosities. In combination with analyses of their stellar components, we have studied the MIR SED features of star-forming and AGN-harboring galaxies.Comment: 45 pages and 63 figures, will be published in PASJ Vol.64 No.

Angioscopic Evaluation of Neointimal Coverage of Coronary Stents

Drug-eluting stents (DES) reduce coronary restenosis significantly; however, late stent thrombosis (LST) occurs, which requires long-term antiplatelet therapy. Angioscopic grading of neointimal coverage of coronary stent struts was established, and it was revealed that neointimal formation is incomplete and prevalence of LST is higher in DES when compared to bare-metal stents. It was also observed that the neointima is thicker and LST is less frequent in paclitaxel-eluting and zotarolimus-eluting stents than in sirolimus-eluting stents. Many new stents were devised and they are now under experimental or clinical investigations to overcome the shortcomings of the stents that have been employed clinically. Endothelial cells are highly anti-thrombotic. Neo-endothelial cell damage is considered to be caused by friction between the cells and stent struts due to the thin neointima between them which might act as a cushion. Therefore, development of a DES that causes an appropriate thickness (around 100 μm) of the neointima is a potential option with which to prevent neo-endothelial cell damage and consequent LST while preventing restenosis

Unbiased large spectroscopic surveys of galaxies selected by SPICA using dust bands

The mid-infrared (IR) range contains many spectral features associated with large molecules and dust grains such as polycyclic aromatic hydrocarbons (PAHs) and silicates. These are usually very strong compared to fine-structure gas lines, and thus valuable in studying the spectral properties of faint distant galaxies. In this paper, we evaluate the capability of low-resolution mid-IR spectroscopic surveys of galaxies that could be performed by SPICA. The surveys are designed to address the question how star formation and black hole accretion activities evolved over cosmic time through spectral diagnostics of the physical conditions of the interstellar/circumnuclear media in galaxies. On the basis of results obtained with Herschel far-IR photometric surveys of distant galaxies and Spitzer and AKARI near- to mid-IR spectroscopic observations of nearby galaxies, we estimate the numbers of the galaxies at redshift z > 0.5, which are expected to be detected in the PAH features or dust continuum by a wide (10 deg^2) or deep (1 deg^2) blind survey, both for a given observation time of 600 hours. As by-products of the wide blind survey, we also expect to detect debris disks, through the mid-IR excess above the photospheric emission of nearby main-sequence stars, and we estimate their number. We demonstrate that the SPICA mid-IR surveys will efficiently provide us with unprecedentedly large spectral samples, which can be studied further in the far-IR with SPICA.Comment: Paper accepted for publication on PASA on 18th October 2017, as part of the SPICA Special Issu

The North Ecliptic Pole Wide survey of AKARI: a near- and mid-infrared source catalog

We present a photometric catalog of infrared (IR) sources based on the North Ecliptic PoleWide field (NEP-Wide) survey of AKARI, which is an infrared space telescope launched by Japan. The NEP-Wide survey covered 5.4 deg2 area, a nearly circular shape centered on the North Ecliptic Pole, using nine photometric filter-bands from 2 - 25 {\mu}m of the Infrared Camera (IRC). Extensive efforts were made to reduce possible false objects due to cosmic ray hits, multiplexer bleeding phenomena around bright sources, and other artifacts. The number of detected sources varied depending on the filter band: with about 109,000 sources being cataloged in the near-IR bands at 2 - 5 {\mu}m, about 20,000 sources in the shorter parts of the mid-IR bands between 7 - 11 {\mu}m, and about 16,000 sources in the longer parts of the mid-IR bands, with \sim 4,000 sources at 24 {\mu}m. The estimated 5? detection limits are approximately 21 magnitude (mag) in the 2 - 5 {\mu}m bands, 19.5 - 19 mag in the 7 - 11 {\mu}m, and 18.8 - 18.5 mag in the 15 - 24 {\mu}m bands in the AB magnitude scale. The completenesses for those bands were evaluated as a function of magnitude: the 50% completeness limits are about 19.8 mag at 3 {\mu}m, 18.6 mag at 9 {\mu}m, and 18 mag at 18 {\mu}m band, respectively. To construct a reliable source catalog, all of the detected sources were examined by matching them with those in other wavelength data, including optical and ground-based near-IR bands. The final band-merged catalog contains about 114,800 sources detected in the IRC filter bands. The properties of the sources are presented in terms of the distributions in various color-color diagrams.Comment: Accepted for publication in A&A, 23 pages, 27 figure

Far infrared luminosity function of local galaxies in the AKARI Deep Field South

We present the first far-infrared luminosity function in the AKARI Deep Field South, a premier deep field of the AKARI Space Telescope, using spectroscopic redshifts obtained with AAOmega. To date, we have found spectroscopic redshifts for 389 galaxies in this field and have measured the local (z<0.25) 90 μm luminosity function using about one-third of these redshifts. The results are in reasonable agreement with recent theoretical predictions

Hyper-luminous Dust Obscured Galaxies discovered by the Hyper Suprime-Cam on Subaru and WISE

We present the photometric properties of a sample of infrared (IR) bright dust obscured galaxies (DOGs). Combining wide and deep optical images obtained with the Hyper Suprime-Cam (HSC) on the Subaru Telescope and all-sky mid-IR (MIR) images taken with Wide-Field Infrared Survey Explorer (WISE), we discovered 48 DOGs with $i - K_\mathrm{s} > 1.2$ and $i - [22] > 7.0$, where $i$, $K_\mathrm{s}$, and [22] represent AB magnitude in the $i$-band, $K_\mathrm{s}$-band, and 22 $\mu$m, respectively, in the GAMA 14hr field ($\sim$ 9 deg$^2$). Among these objects, 31 ($\sim$ 65 %) show power-law spectral energy distributions (SEDs) in the near-IR (NIR) and MIR regime, while the remainder show a NIR bump in their SEDs. Assuming that the redshift distribution for our DOGs sample is Gaussian, with mean and sigma $z$ = 1.99 $\pm$ 0.45, we calculated their total IR luminosity using an empirical relation between 22 $\mu$m luminosity and total IR luminosity. The average value of the total IR luminosity is (3.5 $\pm$ 1.1) $\times$ $10^{13}$ L$_{\odot}$, which classifies them as hyper-luminous infrared galaxies (HyLIRGs). We also derived the total IR luminosity function (LF) and IR luminosity density (LD) for a flux-limited subsample of 18 DOGs with 22 $\mu$m flux greater than 3.0 mJy and with $i$-band magnitude brighter than 24 AB magnitude. The derived space density for this subsample is log $\phi$ = -6.59 $\pm$ 0.11 [Mpc$^{-3}$]. The IR LF for DOGs including data obtained from the literature is well fitted by a double-power law. The derived lower limit for the IR LD for our sample is $\rho_{\mathrm{IR}}$ $\sim$ 3.8 $\times$ 10$^7$ [L$_{\odot}$ Mpc$^{-3}$] and its contributions to the total IR LD, IR LD of all ultra-luminous infrared galaxies (ULIRGs), and that of all DOGs are $>$ 3 %, $>$ 9 %, and $>$ 15 %, respectively.Comment: 15 pages, 15 figures, and 3 tables, accepted for publication in PASJ (Subaru special issue

A far-infrared spectroscopic survey of intermediate redshift (ultra) luminous infrared galaxies

We present Herschel far-IR photometry and spectroscopy as well as ground-based CO observations of an intermediate redshift (0.21 _ z _ 0.88) sample of Herschel-selected (ultra)-luminous infrared galaxies (LIR >1011.5 L_). With these measurements, we trace the dust continuum, far-IR atomic line emission, in particular [C ii] 157.7μm, as well as the molecular gas of z ∼ 0.3 luminous and ultraluminous infrared galaxies (LIRGs and ULIRGs) and perform a detailed investigation of the interstellar medium of the population. We find that the majority of Herschel-selected intermediate redshift (U)LIRGs have LCii/LFIR ratios that are a factor of about 10 higher than that of local ULIRGs and comparable to that of local normal and high-z star-forming galaxies. Using our sample to bridge local and high-z [C ii] observations, we find that the majority of galaxies at all redshifts and all luminosities follow an LCii−LFIR relation with a slope of unity, from which local ULIRGs and high-z active-galactic-nucleus-dominated sources are clear outliers.We also confirm that the strong anti-correlation between the LCii/LFIR ratio and the far-IR color L60/L100 observed in the local universe holds over a broad range of redshifts and luminosities, in the sense that warmer sources exhibit lower LC ii/LFIR at any epoch. Intermediate redshift ULIRGs are also characterized by large molecular gas reservoirs and by lower star formation efficiencies compared to that of local ULIRGs. The high LC ii/LFIR ratios, the moderate star formation efficiencies (LIR/L _COor LIR/MH2 ), and the relatively low dust temperatures of our sample (which are also common characteristics of high-z star-forming galaxies with ULIRG-like luminosities) indicate that the evolution of the physical properties of (U)LIRGs between the present day and z > 1 is already significant by z ∼ 0.3

Detection of the Cosmic Far-Infrared Background in the AKARI Deep Field South

We report the detection and measurement of the absolute brightness and spatial fluctuations of the cosmic infrared background (CIB) with the AKARI satellite. We have carried out observations at 65, 90, 140 and 160 um as a cosmological survey in AKARI Deep Field South (ADF-S), which is one of the lowest cirrus regions with contiguous area on the sky. After removing bright galaxies and subtracting zodiacal and Galactic foregrounds from the measured sky brightness, we have 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 um obtained with the Spitzer satellite from the stacking analysis of 24-um selected sources. The discrepancy with the Spitzer result is possibly due to a new galaxy population at high redshift obscured by hot dust. From power spectrum analysis at 90 um, three components are identified: shot noise due to individual galaxies; Galactic cirrus emission dominating at the largest angular scales of a few degrees; and an additional component at an intermediate angular scale of 10-30 arcminutes, possibly due to galaxy clustering. The spectral shape of the clustering component at 90 um is very similar to that at longer wavelengths as observed by Spitzer and BLAST. Moreover, the color of the fluctuations indicates that the clustering component is as red as Ultra-luminous infrared galaxies (ULIRGs) at high redshift, These galaxies are not likely to be the majority of the CIB emission at 90 um, but responsible for the clustering component. Our results provide new constraints on the evolution and clustering properties of distant infrared galaxies.Comment: 50 pages, 15 figures, submitted to Ap

The AKARI/IRC Mid-Infrared All-Sky Survey

Context : AKARI is the first Japanese astronomical satellite dedicated to infrar ed astronomy. One of the main purposes of AKARI is the all-sky survey performed with six infrared bands between 9 and 200um during the period from 2006 May 6 to 2007 August 28. In this paper, we present the mid-infrared part (9um and 18um b ands) of the survey carried out with one of the on-board instruments, the Infrar ed Camera (IRC). Aims : We present unprecedented observational results of the 9 and 18um AKARI al l-sky survey and detail the operation and data processing leading to the point s ource detection and measurements. Methods : The raw data are processed to produce small images for every scan and point sources candidates, above the 5-sigma noise level per single scan, are der ived. The celestial coordinates and fluxes of the events are determined statisti cally and the reliability of their detections is secured through multiple detect ions of the same source within milli-seconds, hours, and months from each other. Results : The sky coverage is more than 90% for both bands. A total of 877,091 s ources (851,189 for 9um, 195,893 for 18um) are confirmed and included in the cur rent release of the point source catalogue. The detection limit for point source s is 50mJy and 90mJy for the 9um and 18um bands, respectively. The position accu racy is estimated to be better than 2". Uncertainties in the in-flight absolute flux calibration are estimated to be 3% for the 9um band and 4% for the 18um ban d. The coordinates and fluxes of detected sources in this survey are also compar ed with those of the IRAS survey and found to be statistically consistent.Comment: Accepted for publication in AandA AKARI special issu