148 research outputs found
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
We have studied the star-formation and AGN activity of massive galaxies in
the redshift range , 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.
A deep ATCA 20cm radio survey of the AKARI Deep Field South near the South Ecliptic Pole
The results of a deep 20 cm radio survey at 20 cm are reported of the AKARI
Deep Field South (ADF-S) near the South Ecliptic Pole (SEP), using the
Australia Telescope Compact Array telescope, ATCA. The survey has 1 sigma
detection limits ranging from 18.7--50 microJy per beam over an area of ~1.1 sq
degrees, and ~2.5 sq degrees to lower sensitivity. The observations, data
reduction and source count analysis are presented, along with a description of
the overall scientific objectives, and a catalogue containing 530 radio sources
detected with a resolution of 6.2" x 4.9". The derived differential source
counts show a pronounced excess of sources fainter than ~1 mJy, consistent with
an emerging population of star forming galaxies. Cross-correlating the radio
with AKARI sources and archival data we find 95 cross matches, with most
galaxies having optical R-magnitudes in the range 18-24 mag, and 52 components
lying within 1" of a radio position in at least one further catalogue (either
IR or optical). We have reported redshifts for a sub-sample of our catalogue
finding that they vary between galaxies in the local universe to those having
redshifts of up to 0.825. Associating the radio sources with the Spitzer
catalogue at 24 microns, we find 173 matches within one Spitzer pixel, of which
a small sample of the identifications are clearly radio loud compared to the
bulk of the galaxies. The radio luminosity plot and a colour-colour analysis
suggest that the majority of the radio sources are in fact luminous star
forming galaxies, rather than radio-loud AGN. There are additionally five cross
matches between ASTE or BLAST submillimetre galaxies and radio sources from
this survey, two of which are also detected at 90 microns, and 41 cross-matches
with submillimetre sources detected in the Herschel HerMES survey Public Data
release.Comment: MNRAS accepted and in press 9 July 2012: 28 pages, 15 Figures, 17
Table
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
An Optical Source Catalog of the North Ecliptic Pole Region
We present a five (u*,g',r',i',z') band optical photometry catalog of the
sources in the North Ecliptic Pole (NEP) region based on deep observations made
with MegaCam at CFHT. The source catalog covers about 2 square degree area
centered at the NEP and reaches depths of about 26 mag for u*, g', r' bands,
about 25 mag for i' band, and about 24 mag for z' band (4 sigma detection over
an 1 arcsec aperture). The total number of cataloged sources brighter than r'=
23 mag is about 56,000 including both point sources and extended sources. From
the investigation of photometric properties using the color-magnitude diagrams
and color-color diagrams, we have found that the colors of extended sources are
mostly (u*-r') 0.5. This can be used to separate the
extended sources from the point sources reliably, even for the faint source
domain where typical morphological classification schemes hardly work
efficiently. We have derived an empirical color-redshift relation of the red
sequence galaxies using the Sloan Digital Sky Survey data. By applying this
relation to our photometry catalog and searching for any spatial overdensities,
we have found two galaxy clusters and one nearby galaxy group.Comment: 34 pages, 15 figures, 2 tables. Accepted for publication in ApJS. The
pdf file with high resolution figures can be downloaded from
http://astro.snu.ac.kr/~nhwang/index.files/nep.htm
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 and , where
, , and [22] represent AB magnitude in the -band,
-band, and 22 m, respectively, in the GAMA 14hr field
( 9 deg). Among these objects, 31 ( 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 = 1.99
0.45, we calculated their total IR luminosity using an empirical relation
between 22 m luminosity and total IR luminosity. The average value of the
total IR luminosity is (3.5 1.1) L, 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 m flux greater than 3.0 mJy and
with -band magnitude brighter than 24 AB magnitude. The derived space
density for this subsample is log = -6.59 0.11 [Mpc]. 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
3.8 10 [L Mpc] 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
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