arXiv subjects

Toshinobu Takagi

Publications and source records attributed to Toshinobu Takagi.

At least 37 records · Page 2Linked to original sources

arXiv2014

Optical - Near-Infrared catalogue for the AKARI North Ecliptic Pole Deep Field

Aims. We present an 8-band (u*, g', r', i', z', Y, J, Ks) optical to NIR deep photometric catalog based on the observations made with MegaCam and WIRCam at CFHT, and compute photometric redshifts, zp in the North Ecliptic Pole (NEP) region. Our catalog provides us to identify the counterparts, and zp for AKARI NIR/MIR sources. Results. The estimated 4sigma detection limits within an 1" aperture radius are 26.7, 25.9, 25.1, and 24.1 mag [AB] for g', r', i', and z'-bands and 23.4, 23.0, and 22.7 mag for Y, J, and Ks-bands, respectively. There are a total of 85797 sources in the band-merged catalog. An astrometric accuracy of this catalog determined by examining coordinate offsets with regard to 2MASS is 0.013" with a root mean square offset of 0.32". We distinguish 5441 secure stars from extended sources using u*-J vs. g'-Ks colors, combined with the SExtractor stellarity index of the images. Comparing with galaxy spectroscopic redshifts, we find a photometric redshift dispersion, sigma_(dz/(1+z)), of 0.032 and catastrophic failure rate, dz/(1+z)>0.15, of 5.8% at z<1, while a dispersion of 0.117 and a catastrophic failures rate of 16.6% at z>1. We extend estimate of the zp uncertainty over the full magnitude/redshift space with a redshift probability distribution function and find that our redshift are highly accurate with z'<22 at zp<2.5 and for fainter sources with z'<24 at z<1. From the investigation of photometric properties of AKARI infrared sources (23354 sources) using the g'z'Ks diagram, <5% of AKARI sources with optical counterparts are classified as high-z (1.4<z<2.5) star-forming galaxies. Among the high-z star-forming galaxies, AKARI MIR detected sources seem to be affected by stronger dust extinction compared with sources with non-detections in the AKARI MIR bands. The full, electronic version of our catalog with zp will be available at the CDS.

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arXiv2013

A tale of two feedbacks: star-formation in the host galaxies of radio-AGN

Several lines of argument support the existence of a link between activity at the nuclei of galaxies, in the form of an accreting supermassive black hole, and star-formation activity in these galaxies. The exact nature of this link is still under debate. Radio jets have long been argued to be an ideal mechanism that allows AGN to interact with their host galaxy and regulate star-formation. In this context, we are using a sample of radio sources in the North Ecliptic Pole (NEP) field to study the nature of the putative link between AGN activity and star-formation. This is done by means of spectral energy distribution (SED) fitting. We use the excellent spectral coverage of the AKARI infrared space telescope together with the rich ancillary data available in the NEP to build SEDs extending from UV to far-IR wavelengths. Through SED fitting we constrain both the AGN and host galaxy components. We find a significant AGN component in our sample of relatively faint radio-sources ($<$mJy), that increases in power with increasing radio-luminosity. At the highest radio-luminosities, the presence of powerful jets dominates the radio emission of these sources. A positive correlation is found between the luminosity of the AGN component and that of star-formation in the host galaxy, independent of the radio luminosity. By contrast, for a given redshift and AGN luminosity, we find that increasing radio-luminosity leads to a decrease in the specific star-formation rate. The most radio-loud AGN are found to lie on the main sequence of star-formation for their respective redshifts. For the first time, such a two-sided feedback process is seen in the same sample. We conclude that radio jets do suppress star-formation in their host galaxies but appear not to totally quench it. Our results therefore support the maintenance nature of "radio-mode" feedback from radio-AGN jets.

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arXiv2013

Detection of H-alpha emission from z>3.5 submillimetre luminous galaxies with AKARI-FUHYU spectroscopy

We present tentative H-alpha emission line detections of four submillimetre-detected galaxies at z>3.5: the radio galaxies 8C1909+722 and 4C60.07 at signal-to-noise ratios (SNRs) of 3.1 and 2.5, and two submillimetre-selected galaxies (SMGs) near the first of these at SNRs of 10.0 and 2.4, made with the AKARI Space Telescope as part of the FUHYU mission program. These are the highest-redshift H-alpha detections in such galaxies, made possible by AKARI's unique near-infrared spectroscopic capability. The two radio galaxies had known redshifts and surrounding structure, and we have detected broad H-alpha components indicating the presence of dust-shrouded quasars. We conclude that powerful AGNs at z>3.5 occur in peaks of the star-formation density fields, supporting a close connection between stellar mass build-up and black hole mass assembly at this redshift. We also show that 4C60.07 is a binary AGN. The H-alpha detections of the two SMGs are the first redshift determinations for these sources, confirming their physical association around their companion radio galaxy. The H-alpha-derived star formation rates (SFRs) for the SMGs are lower than their far-infrared derived SFRs by a factor of ~10, suggesting a level of dust obscuration similar to that found in studies at ~1<z<2.7.

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arXiv2012

The 3.3 micron PAH Emission as a Star Formation Rate Indicator

Polycyclic Aromatic Hydrocarbon (PAH) emission features dominate the mid-infrared spectra of star-forming galaxies and can be useful to calibrate star formation rates and diagnose ionized states of grains. However, the PAH 3.3 micron feature has not been studied as much as other PAH features since it is weaker than others and resides outside of Spitzer capability. In order to detect and calibrate the 3.3 micron PAH emission and investigate its potential as a star formation rate indicator, we carried out an AKARI mission program, AKARI mJy Unbiased Survey of Extragalactic Survey (AMUSES) and compare its sample with various literature samples. We obtained 2 ~5 micron low resolution spectra of 20 flux-limited galaxies with mixed SED classes, which yields the detection of the 3.3 micron PAH emission from three out of 20 galaxies. For the combined sample of AMUSES and literature samples, the 3.3 micron PAH luminosities correlate with the infrared luminosities of star-forming galaxies, albeit with a large scatter (1.5 dex). The correlation appears to break down at the domain of ultra-luminous infrared galaxies (ULIRGs), and the power of the 3.3 micron PAH luminosity as a proxy for the infrared luminosity is hampered at log[L(PAH3.3)/(erg/sec)] > -42.0. Possible origins for this deviation in the correlation are discussed, including contribution from AGN and strongly obscured YSOs, and the destruction of PAH molecules in ULIRGs.

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arXiv2012

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 μm 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 μm, about 20,000 sources in the shorter parts of the mid-IR bands between 7 - 11 μm, and about 16,000 sources in the longer parts of the mid-IR bands, with \sim 4,000 sources at 24 μm. The estimated 5? detection limits are approximately 21 magnitude (mag) in the 2 - 5 μm bands, 19.5 - 19 mag in the 7 - 11 μm, and 18.8 - 18.5 mag in the 15 - 24 μm 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 μm, 18.6 mag at 9 μm, and 18 mag at 18 μm 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.

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arXiv2012

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.

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arXiv2012

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 micron luminosity function using about one-third of these redshifts. The results are in reasonable agreement with recent theoretical predictions.

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arXiv2011

Star Formation and AGN activity in Galaxies classified using the 1.6 μm Bump and PAH features at $z = 0.4-2$

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.

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arXiv2011

AKARI Observation of the North Ecliptic Pole (NEP) Supercluster at z = 0.087: mid-infrared view of transition galaxies

We present the mid-infrared (MIR) properties of galaxies within a supercluster in the North Ecliptic Pole region at z?0.087 observed with the AKARI satellite. We use data from the AKARI NEP-Wide (5.4 deg2) IR survey and the CLusters of galaxies EVoLution studies (CLEVL) mission program. We show that near-IR (3 μm)-mid- IR (11 μm) color can be used as an indicator of the specific star formation rate and the presence of intermediate age stellar populations. From the MIR observations, we find that red-sequence galaxies consist not only of passively evolving red early-type galaxies, but also of 1) "weak-SFG" (disk-dominated star-forming galaxies which have star formation rates lower by \sim 4 \times than blue-cloud galaxies), and 2) "intermediate- MXG" (bulge-dominated galaxies showing stronger MIR dust emission than normal red early-type galaxies). Those two populations can be a set of transition galaxies from blue, star-forming, late-type galaxies evolving into red, quiescent, early-type ones. We find that the weak-SFG are predominant at intermediate masses (1010M\odot < M\star < 1010.5M\odot) and are typically found in local densities similar to the outskirts of galaxy clusters. As much as 40% of the supercluster member galaxies in this mass range can be classified as weak-SFGs, but their proportion decreases to < 10% at larger masses (M\star > 1010.5 M\odot) at any galaxy density. The fraction of the intermediate-MXG among red- sequence galaxies at 1010M\odot < M\star < 1011M\odot also decreases as the density and mass increase. In particular, \sim42% of the red-sequence galaxies with early-type morphologies are classified as intermediate-MXG at intermediate densities. These results suggest that the star formation activity is strongly dependent on the stellar mass, but that the morphological transformation is mainly controlled by the environment.

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arXiv2011

Infrared Luminosity Functions of AKARI-SDSS Galaxies

By cross-correlating AKARI infrared (IR) sources with the SDSS galaxies, we identified 2357 infrared galaxies with a spectroscopic redshift. This is not just one of the largest samples of local IR galaxies, but AKARI provides crucial FIR bands (9, 18, 65, 90, 140, and 160um) in accurately measuring galaxy SED across the peak of the dust emission at ~100um. By fitting modern IR SED models to the AKARI photometry, we measured the total infrared luminosity (L_IR) of individual galaxies more accurately. Using this L_IR, we constructed luminosity functions of infrared galaxies at a median redshift of z=0.031, with 4 times larger sample than previous work. The LF agrees well with that at z=0.0082 (RBGS), showing smooth and continuous evolution toward higher redshift LFs measured in the AKARI NEP deep field. The derived local cosmic IR luminosity density is Omega_IR=3.8x10^8 LsunMpc^-3. We separate galaxies into AGN, star-forming, and composite by using the [NII]/Ha vs [OIII]/Hb line ratios. The fraction of AGN shows a continuous increase with increasing L_IR from 25% to 90% at 9 10^11Lsun, coinciding the break of the both SFG and AGN IR LFs. At L_IR<10^11Lsun, SFG dominates IR Lfs. Only 1.1% of Omega_IR is produced by LIRG, and only 0.03% is by ULIRG in the local Universe. This work also provides the most accurate infrared luminosity density of the local Universe to date. Compared with high redshift results from the AKARI NEP deep survey, we observed a strong evolution of Omega_IR^SFG ~(1+z)^4.1+-0.4 and Omega_IR^AGN ~(1+z)^4.1+-0.5 (abridged).

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arXiv2010

Luminosity Functions of Local Infrared Galaxies with AKARI: Implications to the Cosmic Star Formation History and AGN Evolution

Infrared (IR) luminosity is fundamental to understanding the cosmic star formation history and AGN evolution. The AKARI IR space telescope performed all sky survey in 6 IR bands (9, 18, 65, 90, 140, and 160um) with 3-10 times better sensitivity than IRAS, covering the crucial far-IR wavelengths across the peak of the dust emission. Combined with a better spatial resolution, AKARI can much more precisely measure the total infrared luminosity (L_TIR) of individual galaxies, and thus, the total infrared luminosity density in the local Universe. By fitting IR SED models, we have re-measured L_TIR of the IRAS Revised Bright Galaxy Sample. We present mid-IR monochromatic luminosity to L_TIR conversions for Spitzer 8,24um, AKARI 9,18um, IRAS 12um, WISE 12,22um, and ISO 15um filters, with scatter ranging 13-44%. The resulting AKARI IR luminosity function (LF) agrees well with that from the IRAS. We integrate the LF weighted by L_TIR to obtain a cosmic IR luminosity density of Omega_TIR= (8.5^{+1.5}_{-2.3})x 10^7 L Mpc^-3, of which 7+-1% is produced by LIRGs, and only 0.4+-0.1% is from ULIRGs in the local Universe. Once IR contributions from AGN and star-forming galaxies (SFG) are separated, SFG IR LF shows a steep decline at the bright-end. Compared with high-redshift results from the AKARI NEP deep survey, these data show a strong evolution of Omega_TIRSF propto (1+z)^4.0+-0.5, and Omega_TIRAGN propto (1+z)^4.4+-0.4. For Omega_TIRAGN, the ULIRG contribution exceeds that from LIRG already by z~1. A rapid evolution in both Omega_TIRAGN and Omega_TIRSFG suggests the correlation between star formation and black hole accretion rate continues up to higher redshifts. We compare the evolution of Omega_TIRAGN to that of X-ray luminosity density. The Omega_TIRAGN/Omega_X-rayAGN ratio shows a possible increase at z>1, suggesting an increase of obscured AGN at z>1.

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arXiv2010

A deep radio survey of the AKARI North Ecliptic Pole Field - WSRT 20 cm Radio survey description, observations and data reduction

The Westerbork Radio Synthesis Telescope, WSRT, has been used to make a deep radio survey of an ~ 1.7 sq degree field coinciding with the AKARI North Ecliptic Pole Deep Field. The observations, data reduction and source count analysis are presented, along with a description of the overall scientific objectives. The survey consisted of 10 pointings, mosaiced with enough overlap to maintain a similar sensitivity across the central region that reached as low as 21 microJy per beam at 1.4 GHz. A catalogue containing 462 sources detected with a resolution of 17"x15" is presented. The differential source counts calculated from the WSRT data have been compared with those from the shallow VLA-NEP survey of Kollgaard et al 1994, and show a pronounced excess for sources fainter than ~ 1 mJy, consistent with the presence of a population of star forming galaxies at sub-mJy flux levels. The AKARI North Ecliptic Pole Deep field is the focus of a major observing campaign conducted across the entire spectral region. The combination of these data sets, along with the deep nature of the radio observations will allow unique studies of a large range of topics including the redshift evolution of the luminosity function of radio sources, the clustering environment of radio galaxies, the nature of obscured radio-loud active galactic nuclei, and the radio/far-infrared correlation for distant galaxies. This catalogue provides the basic data set for a future series of paper dealing with source identifications, morphologies, and the associated properties of the identified radio sources.

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arXiv2009

The Mid-infrared View of Red Sequence Galaxies in Abell 2218 with AKARI

We present the {\it AKARI} InfraRed Camera (IRC) imaging observation of early-type galaxies in A2218 at z $\simeq$ 0.175. Mid-infrared (MIR) emission from early-type galaxies traces circumstellar dust emission from AGB stars or/and residual star formation. Including the unique imaging capability at 11 and 15 $μ$m, our {\it AKARI} data provide an effective way to investigate MIR properties of early-type galaxies in the cluster environment. Among our flux-limited sample of 22 red sequence early-type galaxies with precise dynamical and line strength measurements ($<$ 18 mag at 3 $μm$), we find that at least 41% have MIR-excess emission. The $N3-S11$ versus $N3$ (3 and 11 $μ$m) color-magnitude relation shows the expected blue sequence, but the MIR-excess galaxies add a red wing to the relation especially at the fainter end. A SED analysis reveals that the dust emission from AGB stars is the most likely cause for the MIR-excess, with low level of star formation being the next possible explanation. The MIR-excess galaxies show a wide spread of $N3-S11$ colors, implying a significant spread (2--11 Gyr) in the estimated mean ages of stellar populations. We study the environmental dependence of MIR-excess early-type galaxies over an area out to a half virial radius ($\sim$1 Mpc). We find that the MIR-excess early-type galaxies are preferentially located in the outer region. From these evidences, we suggest that the fainter, MIR-excess early-type galaxies have just joined the red sequence, possibly due to the infall and subsequent morphological/spectral transformation induced by the cluster environment.

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arXiv2009

North Ecliptic Pole Wide Field Survey of AKARI: Survey Strategy and Data Characteristics

We present the survey strategy and the data characteristics of the North Ecliptic Pole (NEP) Wide Survey of AKARI. The survey was carried out for about one year starting from May 2006 with 9 passbands from 2.5 to 24 micron and the areal coverage of about 5.8 sq. degrees centered on NEP. The survey depth reaches to 21.8 AB magnitude near infrared (NIR) bands, and ~ 18.6 AB maggnitude at the mid infrared (MIR) bands such as 15 and 18 micron. The total number of sources detected in this survey is about 104,000, with more sources in NIR than in the MIR. We have cross matched infrared sources with optically identified sources in CFHT imaging survey which covered about 2 sq. degrees within NEP-Wide survey region in order to characterize the nature of infrared sources. The majority of the mid infrared sources at 15 and 18 micron band are found to be star forming disk galaxies, with smaller fraction of early type galaxies and AGNs. We found that a large fraction (60~80 %) of bright sources in 9 and 11 micron stars while stellar fraction decreases toward fainter sources. We present the histograms of the sources at mid infrared bands at 9, 11, 15 and 18 micron. The number of sources per magnitude thus varies as m^0.6 for longer wavelength sources while shorter wavelength sources show steeper variation with m, where m is the AB magnitude.

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arXiv2008

Galaxy Clusters at 0.9<z<1.7 in the AKARI NEP deep field

There is a huge gap between properties of red-sequence selected massive galaxy clusters at z<1 and Lyman-break selected proto-clusters at z>3. It is important to understand when and how the z>3 proto-clusters evolve into passive clusters at z<1. We aim to fill this cluster desert by using the space-based N4(4um) imaging with the AKARI. The z'-N4 color is a powerful separator of cluster galaxies at z>1, taking advantage of the 4000A break and the 1.6um bump. We carefully selected 16 promising cluster candidates at 0.9<z<1.7, which all show obvious over-density of galaxies and a prominent red-sequence. At this redshift range, the mid-infrared S15um/S9um flux ratio is an extinction-free indicator of galaxy star formation activity due to the redshifted PAH emission lines (6.2,7.7 and 8.6um). We show statistically that the cluster galaxies have a lower S15um/S9um flux ratio than field galaxies, i.e., cluster galaxies already have lower star-formation activity at 0.9<z<1.7, pushing the formation epoch of these galaxy clusters to a higher redshift.

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arXiv2008

Mapping dusty star formation in and around a cluster at z=0.81 by wide-field imaging with AKARI

We present environmental dependence of dusty star forming activity in and around the cluster RXJ1716.4+6708 at z=0.81 based on wide-field and multi-wavelength observations with Suprime-Cam on the Subaru telescope and IRC onboard the AKARI satellite. Our optical data shows that the optical colour distribution of galaxies starts to dramatically change from blue to red at the medium-density environment such as cluster outskirts, groups and filaments. By combining with infrared data, we find that 15 micron galaxies tend to have optical colours between the red sequence and the blue cloud with a tail into the red sequence. The spatial distribution of the 15 micron galaxies over ~200 arcmin^2 around the cluster reveals that few 15 micron galaxies are detected in the cluster central region. This is probably due to the low star forming activity in the cluster core. However, interestingly, the fraction of 15 micron galaxies in the medium-density environments is as high as in the low-density field, despite the fact that the optical colours start to change in the medium-density environments. Furthermore, we find that 15 micron galaxies which have optically red colours (candidates for dusty red galaxies) and galaxies with high specific star formation rates are also concentrated in the medium-density environment. These results imply that the star forming activity in galaxies in groups and filaments is enhanced due to some environmental effects specific to the medium-density environment, and such a phenomenon is probably directly connected to the truncation of star forming activity in galaxies seen as the dramatic change in optical colours in such environments.

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arXiv2008

A close relationship at z~2: submillimetre galaxies and BzK-selected galaxies

We investigate the relationship between two massive star-forming galaxy populations at redshift z~ 2; i.e. submillimetre galaxies (SMGs) and BzK-selected galaxies (BzKs). Out of 60 SMGs found in the Subaru/XMM-Newton deep field, we collect optical--NIR photometry of 28 radio counterparts for 24 SMGs, based on refined sky positions with a radio map for 35 SMGs (Ivison et al. 2007). We find a correlation between their K-band magnitudes and BzK [= (z-K)-(B-z)] colours: almost all of the K-faint (K_AB > 21.3) radio-detected SMGs have BzK>-0.2, and therefore BzKs. This result gives strong support to perform direct optical identification of SMGs by searching for BzKs around SMGs. We calculate the formal significance (P' value) for each of the BzK associations around radio-undetected SMGs, and find 6 new robust identifications, including one double identification. From this analysis, we obtain the current best estimate on the surface density of BzK-selected SMGs, which indicates that only ~1 per cent of BzKs are SMGs. If BzKs are normal disk-like galaxies at z~ 2 as indicated by the correlation between their star formation rate (SFR) and stellar mass and also by dynamical properties, SMGs are likely to be merging BzKs. In this case, a typical enhancement of SFR due to merging is only a factor of ~ 3, which is an order of magnitude lower than that of local ULIRGs. This may indicate that most of the merging BzKs could be observed as SMGs. Considering a possible high fraction of mergers at z~ 2 (at least it would be higher than the fraction at z> 1 of ~ 10 per cent), it is rather puzzling to find such a low fraction of SMGs in the progenitor population, i.e. BzKs.

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arXiv2008

Number Density Evolution of Ks -band Selected High Redshift Galaxy Populations in the AKARI North Ecliptic Pole Field

We present the number counts of Ks-band selected high redshift galaxy populations such as extremely red objects (EROs), B, z & K -band selected galaxies (BzKs) and distant red galaxies (DRGs) in the AKARI NEP field. The final catalogue contains 308 EROs (Ks<19.0 ; 54 percent are dusty star-forming EROs and the rest are passive old EROs), 137 star-forming BzKs and 38 passive old BzKs (Ks<19.0) and 64 DRGs (Ks<18.6). We also produce individual component source counts for both the dusty star-forming and passive populations. We compare the observed number counts of the high redshift passively evolving galaxy population with a backward pure luminosity evolution (PLE) model allowing different degrees of number density evolution. We find that the PLE model without density evolution fails to explain the observed counts at faint magnitudes, while the model incorporating negative density evolution is consistent with the observed counts of the passively evolving population. We also compare our observed counts of dusty star-forming EROs with a phenomenological evolutionary model postulating that the near-infrared EROs can be explained by the source densities of the far-infrared - submillimetre populations. Our model predicts that the dusty ERO source counts can be explained assuming a 25 percent contribution of submillimetre star-forming galaxies with the majority of brighter Ks -band detected dusty EROs having luminous (rather than HR10 type ultra-luminous) submillimetre counterparts. We propose that the fainter Ks>19.5 population is dominated by the sub-millijansky submillimetre population. We also predict a turnover in in dusty ERO counts around 19<Ks<20.

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