M Tanaka

Kyushu University, Hukuoka, Fukuoka, Japan

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Publications (800)2179.3 Total impact

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    ABSTRACT: We present a catalog of 129 X-ray galaxy groups, covering a redshift range 0.04<z<1.23, selected in the ~3 square degree part of the CFHTLS W1 field overlapping XMM observations performed under the XMM-LSS project. We carry out a statistical study of the redshift evolution out to redshift one of the magnitude gap between the first and the second brightest cluster galaxies of a well defined mass-selected group sample. We find that the slope of the relation between the fraction of groups and the magnitude gap steepens with redshift, indicating a larger fraction of fossil groups at lower redshifts. We find that 22.2$\pm$6% of our groups at z$\leq$0.6 are fossil groups. We compare our results with the predictions of three semi-analytic models based on the Millennium simulation. The intercept of the relation between the magnitude of the brightest galaxy and the value of magnitude gap becomes brighter with increasing redshift. This trend is steeper than the model predictions which we attribute to the younger stellar age of the observed brightest cluster galaxies. This trend argues in favor of stronger evolution of the feedback from active galactic nuclei at z<1 compared to the models. The slope of the relation between the magnitude of the brightest cluster galaxy and the value of the gap does not evolve with redshift and is well reproduced by the models, indicating that the tidal galaxy stripping, put forward as an explanation of the occurrence of the magnitude gap, is both a dominant mechanism and is sufficiently well modeled.
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    ABSTRACT: We present a catalog of 129 X-ray galaxy groups, covering a redshift range 0.04
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    ABSTRACT: We present a large sample of 183 extreme emission-line galaxies (EELGs) at redshift 0.11 < z < 0.93 selected from the 20k zCOSMOS Bright Survey by their unusually large [OIII]5007 equivalent widths. Based on emission-line diagnostics, 165 purely star-forming EELGs and 18 narrow-line AGN candidates are identified. Using multiwavelength COSMOS photometry, HST-ACS I-band imaging and optical zCOSMOS spectroscopy we characterize their main physical properties. EELGs are small (R_50 ~ 1.3 kpc), low-mass (M*/Msol~10^7-10^10) galaxies forming stars at unusually high rates (SFR~0.1-35 Msol/yr), being among the highest specific SFRs galaxies in zCOSMOS. Consistently, the EELGs are luminous and extremely compact at rest-frame UV wavelengths and include strong Ly$\alpha$ emitters, as revealed by GALEX spectroscopy. Using both direct and strong-line methods, we show that zCOSMOS EELGs are low-metallicity systems (12+log(O/H)=8.16 in the median) including several extremely metal-deficient galaxies (<10% solar). Finally, HST-ACS I-band images reveal that ~80% of the EELGs show non-axisymmetric morphologies, including clumpy and tadpole galaxies, and a significant fraction (~29%) of galaxies with additional low surface brightness features strongly suggesting recent or ongoing interactions. As star-forming dwarfs in the local Universe, EELGs are preferably found in relative isolation. While only very few EELGs belong to compact groups, almost one third of them are found in spectroscopically confirmed loose pairs or triplets. The zCOSMOS EELGs are galaxies caught in a transient and probably early period of their evolution, where they are efficiently building-up a significant fraction of their present-day stellar mass in an ongoing galaxy-wide starburst. Therefore, the EELGs constitute an ideal benchmark for comparison studies between low- and high-redshift low-mass star-forming galaxies.
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    ABSTRACT: Polyomavirus BK nephropathy (BKVN) is an important infectious complication in kidney transplant patients. Regular screening using polymerase chain reaction for BK virus DNA in plasma and urinary cytology is effective for early diagnosis of BKVN. However, methods of follow-up and therapeutic targets are not well described. Ten patients with BKVN who received biweekly urinary cytology and repeat biopsies after diagnosis were retrospectively studied. Histological remission of BKVN was determined when biopsy revealed negative SV40 large T-antigen (TAg) staining. Results of urinary cytology and repeat biopsy findings were compared. Urinary decoy cells disappeared in 8 of 10 patients 55 ± 25 (range 13-79) days after index biopsies. In those cases, allograft function was preserved and the final serum creatinine level was 2.14 ± 1.19 (0.80-4.55) mg/dL after 962 ± 393 (325-1563) days of follow-up. Two cases with persistent urinary decoy cells shedding lost their graft 195 and 362 days later. Amongst 29 repeat biopsies, there were 13 TAg-positive and 16 negative biopsies. In 12 of 13 TAg-positive biopsies (92%), urinary decoy cells were still positive, whereas at the same time in 15 TAg-negative biopsies, decoy cells had already disappeared (94%). Cytology testing is advantageous because of its cost effectiveness. Clearance of decoy cells from urine was closely related to histological remission of BKVN, and may possibly be a therapeutic target in BKVN.
    Transplantation Proceedings 03/2014; 46(2):560-3. · 0.95 Impact Factor
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    ABSTRACT: Background Once-daily extended-release tacrolimus (Tac-QD) has been shown to have equivalent efficacy and safety to the twice-daily formulation (Tac-BID) in kidney transplant patients. However, detailed comparison of allograft pathology found on a protocol biopsy (PB) in Tac-QD– versus Tac-BID–based regimens has not been described. Methods We retrospectively investigated 119 de novo living donor kidney transplant patients treated with Tac-QD (n = 90) or Tac-BID (n = 29) and their 3- and 12-month PB results. Other immunosuppressive drugs administered included basiliximab, mycophenolate mofetil, and methylprednisolone. We evaluated daily doses and trough levels of Tac and serum creatinine levels, and compared pathologic findings. Results Daily doses were higher in the Tac-QD group, but trough levels and serum creatinine levels were comparable. On 3- and 12-month PB, the frequency of subclinical rejection was similar between the groups, whereas interstitial fibrosis and tubular atrophy (IF/TA) were less common in the Tac-QD group at 12 months (42.2% vs 20.6%, P = .04). Univariate and multivariate logistic regression analyses revealed that allograft rejection (borderline changes or higher) was associated with IF/TA (odds ratio 4.09, 95% confidence interval 1.76–10.10, P = .001). The Tac-QD–based regimen showed a trend toward the absence of IF/TA but it did not reach statistical significance. Tubular vacuolization and arteriolar hyaline changes were also comparable in the two groups. Conclusions We found a trend toward milder IF/TA, but no significant differences in kidney allograft pathology in patients who were administered Tac-QD– versus Tac-BID–based regimens at 12 months. The effects of Tac-QD on chronic allograft injury must be studied by longer observation.
    Transplantation Proceedings 01/2014; 46(2):395–399. · 0.95 Impact Factor
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    ABSTRACT: We previously identified LH146, a diffuse X-ray source in the Lockman Hole, as a galaxy cluster at redshift 1.753. The redshift was based on one spectroscopic value, buttressed by seven additional photometric redshifts. We here confirm the previous spectroscopic redshift and present concordant spectroscopic redshifts for an additional eight galaxies. The average of these nine redshifts is 1.714 +/- 0.012 (error on mean). Scrutiny of the galaxy distribution in redshift and the plane of the sky shows that there are two concentrations of galaxies near the X-ray source. In addition there are three diffuse X-ray sources spread along the axis connecting the galaxy concentrations. LH146 is one of these three and lies approximately at the center of the two galaxy concentrations and the outer two diffuse X-ray sources. We thus conclude that LH146 is at the redshift initially reported but it is not a single virialized galaxy cluster as previously assumed. Rather it appears to mark the approximate center of a larger region containing more objects. For brevity we term all these objects and their alignments as large scale structure. The exact nature of LH146 itself remains unclear.
    The Astrophysical Journal 11/2013; 780(1). · 6.73 Impact Factor
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    ABSTRACT: We investigate the evolution of the star formation rate (SFR)-density relation in the Extended Chandra Deep Field South (ECDFS) and the Great Observatories Origin Deep Survey (GOODS) fields up to z~1.6. In addition to the "traditional method", in which the environment is defined according to a statistical measurement of the local galaxy density, we use a "dynamical" approach, where galaxies are classified according to three different environment regimes: group, "filament-like", and field. Both methods show no evidence of a SFR-density reversal. Moreover, group galaxies show a mean SFR lower than other environments up to z~1, while at earlier epochs group and field galaxies exhibit consistent levels of star formation (SF) activity. We find that processes related to a massive dark matter halo must be dominant in the suppression of the SF below z~1, with respect to purely density-related processes. We confirm this finding by studying the distribution of galaxies in different environments with respect to the so-called Main Sequence (MS) of star-forming galaxies. Galaxies in both group and "filament-like" environments preferentially lie below the MS up to z~1, with group galaxies exhibiting lower levels of star-forming activity at a given mass. At z>1, the star-forming galaxies in groups reside on the MS. Groups exhibit the highest fraction of quiescent galaxies up to z~1, after which group, "filament-like", and field environments have a similar mix of galaxy types. We conclude that groups are the most efficient locus for star-formation quenching. Thus, a fundamental difference exists between bound and unbound objects, or between dark matter haloes of different masses.
    Monthly Notices of the Royal Astronomical Society 10/2013; 437(1). · 5.52 Impact Factor
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    ABSTRACT: Various studies have reported poorer graft survival among individuals displaying T-cell-positive flow cytometry crossmatches (FCXM). Good outcomes have been observed in immunologically high-risk patients with the use of rituximab, plasmapheresis, and γ-globulin. Because the relevance of FCXM B-cell-positivity (BCXM (+)) alone remains controversial, we examined its impact on living donor renal transplantations. We retrospectively studied 146 adult renal transplantation recipients from April 2007 to June 2012, dividing the patients into BCXM (+) (n = 31) versus BCXM (-) recipients (n = 115). We examined patient and graft survivals as well as rejection rates at 0 to 3, 3 to 12, and 12 to 24 months. We also determined the incidence of infectious diseases. We performed stepwise multivariate regression to identify risk factors contributing rejection episodes. One-year patient and graft survivals were 100% in both groups. The BCXM (-) group have a 16.8% rejection probability whereas the BCXM (+) group, 33.2% (P = .201). There were no significantly differences in the incidence of infectious diseases. Only the rate of a sensitizing history was an independent risk factor for a rejection episode. BCXM (+) showed only a tendency but not a significant impact on rejection episodes compared with BCXM (-); short-term graft survivals were similar.
    Transplantation Proceedings 10/2013; 45(8):2903-6. · 0.95 Impact Factor
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    ABSTRACT: Since the first light observation of ANIR in June 2009, we have been carrying out a Paα narrow-band imaging survey of nearby luminous infrared galaxies (LIRGs). Because Paα is the strongest hydrogen recombination line in the infrared wavelength ranges, it is a good and direct tracer of dust-enshrouded star forming regions, and enables us to probe the star formation activities in LIRGs. We find that LIRGs have two star-forming modes. The origin of the two modes probably come from differences between merging stage and/or star-forming process.
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    ABSTRACT: Fossil groups are considered the end product in a galaxy group's evolution -- a massive central galaxy that dominates the luminosity budget of the group, as the outcome of efficient merging between intermediate-luminosity members. Little is however known about the faint satellite systems of fossil groups. Here we present a SUBARU/Suprime-Cam wide-field, deep imaging study in the B- and R-band of the nearest fossil group NGC 6482 (M_{tot}\sim4\times10^{12}M_{\sun}), covering the virial radius out to 310 kpc. We perform detailed completeness estimations and select group member candidates by a combination of automated object detection and visual inspection. A fiducial sample of 48 member candidates down to M_R -10.5 mag is detected, making this study the deepest of a fossil group up to now. We investigate the photometric scaling relations, the colour-magnitude relation, and the luminosity function of our galaxy sample. We find evidence of recent and ongoing merger events among bright group galaxies. The colour-magnitude relation is comparable to that of nearby galaxy clusters, and exhibits significant scatter at the faintest luminosities. The completeness-corrected luminosity function is dominated by early-type dwarfs and is characterized by a faint end slope \alpha=-1.32\pm0.05. We conclude that the NGC 6482 fossil group shows photometric properties consistent with those of regular galaxy clusters and groups, including a normal abundance of faint satellites.
    Astronomy and Astrophysics 09/2013; · 5.08 Impact Factor
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    ABSTRACT: We present an analysis of cool outflowing gas around galaxies, traced by MgII absorption lines in the co-added spectra of a sample of 486 zCOSMOS galaxies at 1 < z < 1.5. These galaxies span a range of stellar masses (9.45< log[M*/Msun]<10.7) and star formation rates (0.14 < log [SFR/Msun/yr] < 2.35). We identify the cool outflowing component in the MgII absorption and find that the equivalent width of the outflowing component increases with stellar mass. The outflow equivalent width also increases steadily with the increasing star formation rate of the galaxies. At similar stellar masses the blue galaxies exhibit a significantly higher outflow equivalent width as compared to red galaxies. The outflow equivalent width shows strong effect with star formation surface density ({\Sigma}SFR) of the sample. For the disk galaxies, the outflow equivalent width is higher for the face-on systems as compared to the edge-on ones, indicating that for the disk galaxies, the outflowing gas is primarily bipolar in geometry. Galaxies typically exhibit outflow velocities ranging from -200 km/s to -300 km/s and on average the face-on galaxies exhibit higher outflow velocity as compared to the edge-on ones. Galaxies with irregular morphologies exhibit outflow equivalent width as well as outflow velocities comparable to face on disk galaxies. These galaxies exhibit minimum mass outflow rates > 5-7 Msun/yr and a mass loading factor ({\eta} = dMout/dt /SFR) comparable to the star formation rates of the galaxies.
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    ABSTRACT: We explore the role of environment in the evolution of galaxies over 0.1<z<0.7 using the final zCOSMOS-bright data set. Using the red fraction of galaxies as a proxy for the quenched population, we find that the fraction of red galaxies increases with the environmental overdensity and with the stellar mass, consistent with previous works. As at lower redshift, the red fraction appears to be separable in mass and environment, suggesting the action of two processes: mass and environmental quenching. The parameters describing these appear to be essentially the same at z~0.7 as locally. We explore the relation between red fraction, mass and environment also for the central and satellite galaxies separately, paying close attention to the effects of impurities in the central-satellite classification and using carefully constructed samples matched in stellar mass. There is little evidence for a dependence of the red fraction of centrals on overdensity. Satellites are consistently redder at all overdensities, and the satellite quenching efficiency increases with overdensity at 0.1<z<0.4. This is less marked at higher redshift, but both are nevertheless consistent with the equivalent local measurements. At a given stellar mass, the fraction of galaxies that are satellites also increases with the overdensity. At a given overdensity and mass, the obtained relation between the environmental quenching and the satellite fraction agrees well with the satellite quenching efficiency, demonstrating that the environmental quenching in the overall population is consistent with being entirely produced through the satellite quenching process at least up to z=0.7. However, despite the unprecedented size of our high redshift samples, the associated statistical uncertainties are still significant and our statements should be understood as approximations to physical reality, rather than physically exact formulae.
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    ABSTRACT: [abridged] The mass-size relation of early-type galaxies (ETGs) has been largely studied in the last years to probe the mass assembly of the most massive objects in the Universe. In this paper, we focus on the mass-size relation of quiescent massive ETGs (Mstar/Msol > 3*10^10) living in massive clusters (M200 ~ 10^14 Mstar) at 0.8< z <1.5, as compared to those living in the field at the same epoch. Our sample contains ~ 400 ETGs in clusters and the same number in the field. Therefore, our sample is approximately an order of magnitude larger than previous studies in the same redshift range for galaxy clusters. We find that ETGs living in clusters are between ~30-50% larger than galaxies with the same stellar mass residing in the field. We parametrize the size using the mass-normalized size, gamma=Re/Mstar^0.57. The gamma distributions in both environments peak at the same position but the distributions in clusters are more skewed towards larger sizes. Since this size difference is not observed in the local Universe, the size evolution at fixed stellar mass from z~1.5 of cluster galaxies is less steep ((1+z)-0.53pm0.04) than the evolution of field galaxies ((1+z)-0.92pm0.04). The size difference seems to be essentially driven by the galaxies residing in the clusters cores (R<0.5*R200). If part of the size evolution is due to mergers, the difference we see between cluster and field galaxies could be due to higher merger rates in clusters at higher redshift, probably during the formation phase of the clusters when velocity dispersions are lower. We cannot exclude however that the difference is driven by newly quenched galaxies which are quenched more efficiently in clusters. The implications of these results for the hierarchical growth of ETGs will be discussed in a companion paper.
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    ABSTRACT: A sample of 94 narrow line AGN with 0.65<z<1.20 has been selected from the 20k-Bright zCOSMOS galaxy sample by detection of the high-ionization [NeV]3426 line. Taking advantage of the large amount of data available in the COSMOS field, the properties of the [NeV]-selected Type-2 AGN have been investigated, focusing on their host galaxies, X-ray emission, and optical line flux ratios. Finally, the diagnostic developed by Gilli et al. (2010), based on the X-ray to [NeV] luminosity ratio, has been exploited to search for the more heavily obscured AGN. We found that [Ne v]-selected narrow line AGN have Seyfert 2-like optical spectra, although with emission line ratios diluted by a star-forming component. The ACS morphologies and stellar component in the optical spectra indicate a preference for our Type-2 AGN to be hosted in early-spirals with stellar masses greater than 10^(9.5-10)Msun, on average higher than those of the galaxy parent sample. The fraction of galaxies hosting [NeV]-selected obscured AGN increases with the stellar mass, reaching a maximum of about 3% at 2x10^11 Msun. A comparison with other selection techniques at z~1 shows that the detection of the [Ne v] line is an effective method to select AGN in the optical band, in particular the most heavily obscured ones, but can not provide by itself a complete census of AGN2. Finally, the high fraction of [NeV]-selected Type-2 AGN not detected in medium-deep Chandra observations (67%) is suggestive of the inclusion of Compton-thick sources in our sample. The presence of a population of heavily obscured AGN is corroborated by the X-ray to [NeV] ratio; we estimated, by mean of X-ray stacking technique and simulations, that the Compton-thick fraction in our sample of Type-2 AGN is 43+-4%, in good agreement with standard assumptions by the XRB synthesis models.
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    ABSTRACT: Star-formation in the galaxy populations of local massive clusters is reduced with respect to field galaxies, and tends to be suppressed in the core region. Indications of a reversal of the star-formation--density relation have been observed in a few z >1.4 clusters. Using deep imaging from 100-500um from PACS and SPIRE onboard Herschel, we investigate the infrared properties of spectroscopic and photo-z cluster members, and of Halpha emitters in XMMU J2235.3-2557, one of the most massive, distant, X-ray selected clusters known. Our analysis is based mostly on fitting of the galaxies spectral energy distribution in the rest-frame 8-1000um. We measure total IR luminosity, deriving star formation rates (SFRs) ranging from 89-463 Msun/yr for 13 galaxies individually detected by Herschel, all located beyond the core region (r >250 kpc). We perform a stacking analysis of nine star-forming members not detected by PACS, yielding a detection with SFR=48 Msun/yr. Using a color criterion based on a star-forming galaxy SED at the cluster redshift we select 41 PACS sources as candidate star-forming cluster members. We characterize a population of highly obscured SF galaxies in the outskirts of XMMU J2235.3-2557. We do not find evidence for a reversal of the SF-density relation in this massive, distant cluster.
    Monthly Notices of the Royal Astronomical Society 05/2013; 433(2). · 5.52 Impact Factor
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    ABSTRACT: We present the analysis of photometric, spectroscopic, and morphological properties for differently selected samples of passive galaxies up to z=1 extracted from the zCOSMOS-20k spectroscopic survey. This analysis intends to explore the dependence of galaxy properties on the selection criterion adopted, study the degree of contamination due to star-forming outliers, and provide a comparison between different commonly used selection criteria. We extracted from the zCOSMOS-20k catalog six different samples of passive galaxies, based on morphology, optical colors, specific star-formation rate, a best fit to the observed spectral energy distribution, and a criterion that combines morphological, spectroscopic, and photometric information. The morphological sample has the higher percentage of contamination in colors, specific star formation rate and presence of emission lines, while the red & passive ETGs sample is the purest, with properties mostly compatible with no star formation activity; however, it is also the less economic criterion in terms of information used. The best performing among the other criteria are the red SED and the quiescent ones, providing a percentage of contamination only slightly higher than the red & passive ETGs criterion (on average of a factor of ~2) but with absolute values of the properties of contaminants still compatible with a red, passively evolving population. We also provided two revised definitions of early type galaxies based on restframe color-color and color-mass criteria, that better reproduce the observed bimodalities. The analysis of the number densities shows evidences of mass-assembly downsizing, with galaxies at 10.25<log(M/Msun)<10.75 increasing their number by a factor ~2-4 from z=0.6 to z=0.2, by a factor ~2-3 from z=1 to z=0.2 at 10.75<log(M/Msun)<11, and by only ~10-50% from z=1 to z=0.2 at 11<log(M/Msun)<11.5.
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    ABSTRACT: We present a study of SN 2009js in NGC 918. Multi-band Kanata optical photometry covering the first ~120 days show the source to be a Type IIP SN. Reddening is dominated by that due to our Galaxy. One-year-post-explosion photometry with the NTT, and a Subaru optical spectrum 16 days post-discovery, both imply a good match with the well-studied subluminous SN 2005cs. The plateau phase luminosity of SN 2009js and its plateau duration are more similar to the intermediate luminosity IIP SN 2008in. Thus, SN 2009js shares characteristics with both subluminous and intermediate luminosity SNe. Its radioactive tail luminosity lies between SN 2005cs and SN 2008in, whereas its quasi-bolometric luminosity decline from peak to plateau (quantified by a newly-defined parameter Delta[logL] measuring adiabatic cooling following shock breakout) is much smaller than both the others. We estimate the ejected mass of 56Ni to be low (~0.007 Msun). The SN explosion energy appears to have been small, similar to SN 2005cs. SN 2009js is the first subluminous SN IIP to be studied in the mid-infrared. It was serendipitously caught by Spitzer at very early times. In addition, it was detected by WISE 105 days later with a significant 4.6 micron flux excess above the photosphere. The infrared excess luminosity relative to the photosphere is clearly smaller than that of SN 2004dj extensively studied in the mid-infrared. The excess may be tentatively assigned to heated dust with mass ~3e-5 Msun, or to CO fundamental emission as a precursor to dust formation.
    The Astrophysical Journal 03/2013; 767(2). · 6.73 Impact Factor
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    ABSTRACT: Active galactic nuclei (AGN) are thought to play an important role in galaxy evolution. It has been suggested that AGN feedback could be partly responsible for quenching star-formation in the hosts, leading to transition from the blue cloud to the red sequence. The transition seems to occur faster for the most massive galaxies, where traces of AGN activity have been already found as early as at z<0.1. The correlation between AGN activity, aging of the stellar populations and stellar mass still needs to be fully understood, especially at high redshifts. Our aim is to investigate the link between AGN activity, star-formation, and stellar mass of the host galaxy at 0<z<1, looking for spectroscopic traces of AGN and aging of the host. This work provides an extension of the existing studies at z<0.1 and contributes to shed light on galaxy evolution at intermediate redshifts. We used the zCOSMOS 20k data to create a sample of galaxies at z<1. We divided the sample into several mass-redshift bins to obtain stacked galaxy spectra with an improved signal-to-noise ratio (S/N). We exploited emission-line diagnostic diagrams to separate AGN from star-forming galaxies. We found an indication of a role for the total galaxy stellar mass in leading galaxy classification. Stacked spectra show AGN signatures above the log(M_*/M_Sun)>10.2 threshold. Moreover, the stellar populations of AGN hosts are found to be older than star-forming and composite galaxies. This could be due to the the tendency of AGN to reside in massive hosts. The dependence of the AGN classification on the stellar mass agrees with what has been found in previous research. Together with the evidence of older stellar populations inhabiting the AGN-like galaxies, it is consistent with the downsizing scenario. In particular, our evidence points to an evolutionary scenario where the AGN-feedback is capable of quenching the star formation in the most massive galaxies. Therefore, the AGN-feedback is the best candidate for initiating the passive evolutionary phase of galaxies.
    Astronomy and Astrophysics 02/2013; · 5.08 Impact Factor
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    ABSTRACT: We examine the red fraction of central and satellite galaxies in the large zCOSMOS group catalog out to z ~ 0.8 correcting for both the incompleteness in stellar mass and for the less than perfect purities of the central and satellite samples. We show that, at all masses and at all redshifts, the fraction of satellite galaxies that have been quenched, i.e., are red, is systematically higher than that of centrals, as seen locally in the Sloan Digital Sky Survey (SDSS). The satellite quenching efficiency, which is the probability that a satellite is quenched because it is a satellite rather than a central, is, as locally, independent of stellar mass. Furthermore, the average value is about 0.5, which is also very similar to that seen in the SDSS. We also construct the mass functions of blue and red centrals and satellites and show that these broadly follow the predictions of the Peng et al. analysis of the SDSS groups. Together, these results indicate that the effect of the group environment in quenching satellite galaxies was very similar when the universe was about a half its present age, as it is today.
    The Astrophysical Journal 11/2012; 769(1). · 6.73 Impact Factor
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    ABSTRACT: We present the first direct measurement of the mean halo occupation distribution (HOD) of X-ray-selected active galactic nuclei (AGNs) in the COSMOS field at z {<=} 1, based on the association of 41 XMM and 17 C-COSMOS AGNs with member galaxies of 189 X-ray-detected galaxy groups from XMM-Newton and Chandra data. We model the mean AGN occupation in the halo mass range log M{sub 200} [M{sub Sun }] = 13-14.5 with a rolling-off power law with the best-fit index {alpha} = 0.06(- 0.22; 0.36) and normalization parameter f{sub a} 0.05(0.04; 0.06). We find the mean HOD of AGNs among central galaxies to be modeled by a softened step function at log M{sub h} > log M{sub min} = 12.75(12.10, 12.95) M{sub Sun} while for the satellite AGN HOD we find a preference for an increasing AGN fraction with M{sub h} , suggesting that the average number of AGNs in satellite galaxies grows slower ({alpha}{sub s} < 0.6) than the linear proportion ({alpha}{sub s} = 1) observed for the satellite HOD of samples of galaxies. We present an estimate of the projected autocorrelation function (ACF) of galaxy groups over the range of r{sub p} = 0.1-40 h {sup -1} Mpc at (z) = 0.5. We use the large-scale clustering signal to verify the agreement between the group bias estimated by using the observed galaxy groups ACF and the value derived from the group mass estimates. We perform a measurement of the projected AGN-galaxy-group cross-correlation function, excluding from the analysis AGNs that are within galaxy groups and we model the two-halo term of the clustering signal with the mean AGN HOD based on our results.
    The Astrophysical Journal 10/2012; 758(1). · 6.73 Impact Factor

Publication Stats

10k Citations
2,179.30 Total Impact Points


  • 1987–2014
    • Kyushu University
      • • Department of Surgery and Oncology
      • • Division of Surgery
      • • Department of Anatomic Pathology
      • • Faculty of Medical Sciences
      • • Department of Urology
      Hukuoka, Fukuoka, Japan
  • 2013
    • Hiroshima University
      • Division of Physical Sciences
      Hirosima, Hiroshima, Japan
  • 1992–2013
    • The University of Tokyo
      • • Institute for the Physics and Mathematics of the Universe (IPMU)
      • • Department of Astronomy
      • • Department of Electrical and Electronics Engineering
      • • Department of Electrical Engineering and Information Systems
      Edo, Tōkyō, Japan
  • 2012
    • Honolulu University
      Honolulu, Hawaii, United States
  • 2011–2012
    • The Astronomical Observatory of Brera
      Merate, Lombardy, Italy
    • Paris Diderot University
      Lutetia Parisorum, Île-de-France, France
  • 2010–2012
    • French National Centre for Scientific Research
      • • Institut de recherche en astrophysique et planétologie (IRAP)
      • • Institut d'astrophysique spatiale (IAS)
      Lutetia Parisorum, Île-de-France, France
    • Max Planck Institute for Extraterrestrial Physics
      Arching, Bavaria, Germany
  • 2000–2012
    • National Institute for Fusion Science
      Tokitsu-chō, Gifu, Japan
  • 2008–2011
    • European Southern Observatory
      Arching, Bavaria, Germany
    • Ehime University
      • Department of Physics
      Matuyama, Ehime, Japan
  • 2006–2011
    • Japan Atomic Energy Agency
      • • Quantum Beam Science Directorate
      • • Advanced Photon Research Center
      Muramatsu, Niigata, Japan
  • 2009
    • Laboratoire d’Informatique Fondamentale de Marseille
      Marsiglia, Provence-Alpes-Côte d'Azur, France
    • California Institute of Technology
      • Spitzer Science Center
      Pasadena, California, United States
    • Tohoku University
      • Institute of Multidisciplinary Research for Advanced Materials (IMRAM)
      Sendai, Kagoshima, Japan
    • Tokyo Gakugei University
      Koganei, Tōkyō, Japan
  • 1994–2009
    • Nara Medical University
      • Department of Urology
      Nara-shi, Nara, Japan
  • 2006–2008
    • NEC Corporation
      Edo, Tōkyō, Japan
  • 1989–2005
    • Osaka City University
      • • Department of Biochemistry
      • • Faculty of Science
      Ōsaka, Ōsaka, Japan
    • Monash University (Australia)
      Melbourne, Victoria, Australia
  • 2001–2003
    • Osaka University
      • • Institute of Laser Engineering
      • • Department of Physiology
      Ibaraki, Osaka-fu, Japan
    • Kyoto University
      • Faculty of Integrated Human Studies
      Kyoto, Kyoto-fu, Japan
    • Otsu Red Cross Hospital
      Ōtu, Shiga, Japan
  • 2002
    • Noguchi Thyroid Clinic and Hospital Foundation
      Бэппу, Ōita, Japan
    • High Energy Accelerator Research Organization
      • Institute of Materials Structure Science
      Tsukuba, Ibaraki, Japan
  • 1996–2001
    • Asahi General Hospital
      Asahi, Chiba, Japan
    • Fukuoka University
      • Department of Gastroenterology
      Hukuoka, Fukuoka, Japan
  • 1992–2001
    • National Institute for Basic Biology
      Okazaki, Aichi, Japan
  • 1988–2001
    • Gunma University
      • Department of Neurology
      Maebashi, Gunma Prefecture, Japan
  • 1981–2001
    • Kyoto Prefectural University of Medicine
      • • Department of Anatomy
      • • Division of Anatomy and Neurobiology
      • • Department of Anesthesiology
      Kioto, Kyōto, Japan
  • 1992–2000
    • Chiba University
      • Department of Urology
      Chiba-shi, Chiba-ken, Japan
  • 1999
    • Chiba University Hospital
      Tiba, Chiba, Japan
  • 1988–1999
    • University of Tsukuba
      • • Institute of Community Medicine
      • • Department of Neurology
      Tsukuba, Ibaraki-ken, Japan
  • 1986–1999
    • Nagoya University
      • Division of Biological Chemistry
      Nagoya, Aichi, Japan
  • 1998
    • St. Luke's International Hospital
      Edo, Tōkyō, Japan
  • 1994–1998
    • Ono Pharmaceutical Co., Ltd.
      Ōsaka, Ōsaka, Japan
  • 1996–1997
    • Kyushu Kosei Nenkin Hospital
      Kitakyūshū, Fukuoka, Japan
  • 1993–1997
    • The Graduate University for Advanced Studies
      Миура, Kanagawa, Japan
  • 1995
    • Juntendo University
      • Department of Neurology
      Tokyo, Tokyo-to, Japan
  • 1992–1995
    • Japan Red Cross Fukuoka Hospital
      Hukuoka, Fukuoka, Japan
  • 1987–1995
    • Niigata University
      • Division of Neuropathology
      Niahi-niigata, Niigata, Japan
  • 1991
    • St. Vincent Hospital
      Green Bay, Wisconsin, United States
  • 1990
    • Nagaoka Red Cross Hospital
      Нагаока, Niigata, Japan