Updated on 2024/04/13

写真a

 
NAKAMURA, Osamu
 
Affiliation
Faculty of Political Science and Economics, School of Political Science and Economics
Job title
Associate Professor
Degree
Master ( 1997.03 University of Tokyo )
Doctor of Science ( 2001.03 University of Tokyo )
Mail Address
メールアドレス
Homepage URL

Research Experience

  • 2012.04
    -
    Now

    Associate Professor, Faculty of Political Science and Economics, Waseda University

  • 2011.04
    -
    2014.03

    Parttime lecturer, Tokyo Kasei Gakuin University

  • 2010.04
    -
    2012.03

    Assistant Professor, Waseda University

  • 2006.04
    -
    2012.03

    Parttime lecturer, Tokyo City University (Musashi Institute of Technology)

  • 2007.04
    -
    2010.03

    Lecturer, Waseda University

  • 2005.10
    -
    2007.03

    Research Associate, Waseda University

  • 2003.09
    -
    2005.09

    PPARC Researcher, University of Nottingham

  • 2001.04
    -
    2003.09

    CoE Researcher, Institute for Cosmic Ray Research, University of Tokyo

  • 2002.04
    -
    2003.08

    Parttime lecturer, Tokyo City University (Musashi Institute of Technology)

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Education Background

  • 1997.04
    -
    2001.03

    University of Tokyo   School of Science   Department of Astronomy (Doctor Course)  

  • 1995.04
    -
    1997.03

    University of Tokyo   School of Science   Department of Astronomy (Master Course)  

  • 1989.04
    -
    1993.04

    Kyoto University   Faculty of Science   Division of Physics  

Committee Memberships

  • 2018.12
    -
    2024.04

    Japanese Society for Science and Technology Studies  Editorial board member of Journal of science and technology studies

  • 2018.04
    -
    2019.03

    Japan Association for Media, Journalism and Communication Studies  'Asian Journal of Journalism and Media Studies' 2019 Editorial Board

  • 2009.11
    -
     

    Japanese Society for Science and Technology Studies  Chair of the Local Organizing Committee for the 8th (Nov. 2009) Annual Meeting

Research Areas

  • Sociology   Journalism / Sociology   Media / Gender studies   Gender / Sociology of science, history of science and technology   Science and Technology Studies / Science education   Science Education / Astronomy   Astronomy

Research Interests

  • Content Analysis

  • Media

  • Journalism

  • Gender

  • Science, Technology and Society

  • Science Communication

  • Astronomy

▼display all

 

Papers

  • Criminal Suspects and Defendants in Murder-related Incidents as Depicted in the Yomiuri Shimbun: A Perspective on Perpetrator-centric Reporting and Name-based Reporting

    Reina TAKI, Osamu NAKAMURA

    Journal of Liberal Arts   152   1 - 29  2024.03  [Domestic journal]

    Authorship:Last author, Corresponding author

  • Gender Perspectives in the List of "Good Picture Books"

    Yuzuka KAWAI, Osamu NAKAMURA

    Journal of gender studies Japan   26   65 - 78  2023.11  [Refereed]  [Domestic journal]

    Authorship:Last author, Corresponding author

  • Consonance in Television Coverage of Tokyo 2020 Olympics Bid

    Minako I, Osamu NAKAMURA

    Journal of Liberal Arts   151   43 - 74  2023.03  [Domestic journal]

    Authorship:Last author, Corresponding author

  • The tone and frame of nuclear power coverage in the editorials of the Asahi and Yomiuri newspapers

    Akira NAWA, Osamu NAKAMURA

    Journal of Liberal Arts   150   113 - 151  2022.03  [Domestic journal]

    Authorship:Last author, Corresponding author

  • Curricula for Science Journalist Education of Universities in the United States

    Osamu NAKAMURA

    Journal of Liberal Arts   141   25 - 48  2016.12  [Domestic journal]

    Authorship:Lead author, Corresponding author

  • Properties of disks and bulges of spiral and lenticular galaxies in the Sloan Digital Sky Survey

    N. Oohama, S. Okamura, M. Fukugita, N. Yasuda, O. Nakamura

    Astrophysical Journal   705 ( 1 ) 245 - 705  2009.11  [Refereed]  [International journal]  [International coauthorship]

     View Summary

    A bulge-disk decomposition is made for 737 spiral and lenticular galaxies drawn from a Sloan Digital Sky Survey galaxy sample for which morphological types are estimated. We carry out the bulge-disk decomposition using the growth curve fitting method. It is found that bulge properties, effective radius, effective surface brightness, and also absolute magnitude, change systematically with the morphological sequence; from early to late types, the size becomes somewhat larger, and surface brightness and luminosity fainter. In contrast, disks are nearly universal, their properties remaining similar among disk galaxies irrespective of detailed morphologies from S0 to Sc. While these tendencies were often discussed in previous studies, the present study confirms them based on a large homogeneous magnitude-limited field galaxy sample with morphological types estimated. The systematic change of bulge-to-total luminosity ratio, B/T, along the morphological sequence is therefore not caused by disks but mostly by bulges. It is also shown that elliptical galaxies and bulges of spiral galaxies are unlikely to be in a single sequence. We infer the stellar mass density (in units of the critical mass density) to be Ω = 0.0021 for spheroids, i.e., elliptical galaxies plus bulges of spiral galaxies, and Ω = 0.00081 for disks.

    DOI

    Scopus

    26
    Citation
    (Scopus)
  • A catalog of morphologically classified galaxies from the sloan digital sky survey: North equatorial region

    Masataka Fukugita, Osamu Nakamura, Sadanori Okamura, Naoki Yasuda, John C. Barentine, Jon Brinkmann, James E. Gunn, Mike Harvanek, Takashi Ichikawa, Robert H. Lupton, Donald P. Schneider, Michael A. Strauss, Donald G. York

    Astronomical Journal   134 ( 2 ) 579 - 593  2007.08  [Refereed]  [International journal]  [International coauthorship]

     View Summary

    We present a catalog of morphologically classified bright galaxies in the north equatorial stripe (230 deg2) derived from the Third Data Release of the Sloan Digital Sky Survey (SDSS). Morphological classification is performed by visual inspection of images in the g band. The catalog contains 2253 galaxies complete to a magnitude limit of r = 16 after Galactic extinction correction, selected from 2658 objects that are judged to be extended in the photometric catalog in the same magnitude limit. A total of 1866 galaxies in our catalog have spectroscopic information. A brief statistical analysis is presented for the frequency of morphological types and mean colors in the catalog. A visual inspection of the images reveals that the rate of interacting galaxies in the local universe is approximately 1.5% in the r ≤ 16 sample. A verification is made for the photometric catalog generated by the SDSS, especially as to its brightend completeness. © 2007. The American Astronomical Society. All rights reserved.

    DOI

    Scopus

    125
    Citation
    (Scopus)
  • Elemental abundance measurements in low-redshift damped Lyman α absorbers

    Joseph D. Meiring, Varsha P. Kulkarni, Pushpa Khare, Jill Bechtold, Donald G. York, Jun Cui, James T. Lauroesch, Arlin P.S. Crotts, Osamu Nakamura

    Monthly Notices of the Royal Astronomical Society   370 ( 1 ) 43 - 62  2006.07  [Refereed]  [International journal]  [International coauthorship]

     View Summary

    We present elemental abundance measurements for nine damped Lyman α (Lyα) systems (DLAs) and one sub-DLA at 0.1 ≤ z ≤ 1.5 from recent observations with the Multiple Mirror Telescope (MMT). Most of these absorbers are found to be metal poor, while two are found to have ≈30-50 per cent solar metallicities. Combining our data with other data from the literature, we find that the systems with higher [Zn/H] also have stronger depletion as measured by [Cr/Zn] and [Fe/Zn]. The relationship between the metallicity and Hi column density is also investigated. Together with our previous MMT survey, we have discovered two of the four known absorbers at z < 1.5 that lie above (although near) the 'obscuration threshold'. This appears to be a result of selecting absorbers with strong metal lines in our sample. It would be interesting to find other similar systems by observing a larger sample and study how much such systems contribute to the cosmic budget of metals. Finally, an analysis of the NHI-weighted mean metallicity versus redshift for our sample combined with data from the literature supports previous conclusions that the NHI-weighted mean global DLA metallicity rises slowly at best and falls short of solar levels by a factor of >4 even at z = 0. © 2006 RAS.

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    43
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    (Scopus)
  • Star formation rates and chemical abundances of emission-line galaxies in intermediate-redshift clusters

    M. Mouhcine, S. P. Bamford, A. Aragón-Salamanca, O. Nakamura, B. Milvang-Jensen

    Monthly Notices of the Royal Astronomical Society   368 ( 4 ) 1871 - 1879  2006.06  [Refereed]  [International journal]  [International coauthorship]

     View Summary

    We examine the evolutionary status of luminous, star-forming galaxies in intermediate-redshift clusters by considering their star formation rates (SFRs) and the chemical and ionization properties of their interstellar emitting gas. Our sample consists of 17 massive, star-forming, mostly disc galaxies with , in clusters with redshifts in the range , with a median of . We compare these galaxies with the identically selected and analysed intermediate-redshift field sample of Mouhcine et al., and with local galaxies from the Nearby Field Galaxy Survey of Jansen et al. From our optical spectra, we measure the equivalent widths of and [O iii]λ5007 emission lines to determine diagnostic line ratios, oxygen abundances and extinction-corrected SFRs. The star-forming galaxies in intermediate-redshift clusters display emission-line equivalent widths which are, on average, significantly smaller than measured for field galaxies at comparable redshifts. However, a contrasting fraction of our cluster galaxies have equivalent widths similar to the highest observed in the field. This tentatively suggests a bimodality in the SFRs per unit luminosity for galaxies in distant clusters. We find no evidence for further bimodalities, or differences between our cluster and field samples, when examining additional diagnostics and the oxygen abundances of our galaxies. This maybe because no such differences exist, perhaps because the cluster galaxies which still display signs of star formation have recently arrived from the field. In order to examine this topic with more certainty, and to further investigate the way in which any disparity varies as a function of cluster properties, larger spectroscopic samples are needed. © 2006 RAS.

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    7
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  • The metallicities of luminous, massive field galaxies at intermediate redshifts

    M. Mouhcine, S. P. Bamford, A. Aragón-Salamanca, O. Nakamura, B. Milvang-Jensen

    Monthly Notices of the Royal Astronomical Society   369 ( 2 ) 891 - 908  2006.06  [Refereed]  [International journal]  [International coauthorship]

     View Summary

    We derive oxygen abundances for a sample of 40 luminous (MB ≲ -19), star-forming, mostly disc, field galaxies with redshifts in the range 0.2 ≲ z ≲ 0.8, with a median of 〈z〉 = 0.45. Oxygen abundances, relative to hydrogen, of the interstellar emitting gas are estimated by means of the empirically calibrated strong emission-line ratio technique. The derived 12 + log (O/H) values range from 8.4 to 9.0, with a median of 8.7. Twenty of these galaxies have securely measured rotation velocities, in the range 50-244 km s-1. The measured emission-line equivalent widths and diagnostic ratios for the intermediate redshift galaxies cover similar ranges to those observed across a large sample of local galaxies. The estimated oxygen abundances for our luminous star-forming intermediate redshift galaxies cover the same range as their local counterparts. However, at a given galaxy luminosity, many of our galaxies have significantly lower oxygen abundances, i.e. 12 + log (O/H) ∼8.6, than local galaxies with similar luminosities. Interestingly, these luminous, massive, intermediate redshift, star-forming galaxies with low oxygen abundances exhibit physical conditions, i.e. emission-line equivalent width and ionization state, very similar to those of local faint and metal-poor star-forming galaxies. The oxygen abundance of the interstellar gas does not seem to correlate with the maximum rotation velocity or the emission scalelength of the parent galaxy. This suggests that there is diversity in the intrinsic properties of the massive field galaxy population at intermediate redshifts. The distribution of the colour excess, derived from the ratio of extinction-uncorrected Hβ and [O II]λ3727 star formation rate indicators, covers a similar range to that observed locally, but exhibits a lower mean than is observed for local optically selected star-forming galaxies. Luminous field galaxies at intermediate redshifts show similar star formation rates to their local counterparts. However, metal-poor, massive, star-forming galaxies tend to be systematically less affected by internal reddening than metal-rich, massive galaxies, which cover similar range of colour excess to local metal-rich luminous galaxies. Finally, the correlation between oxygen abundance and colour excess for intermediate redshift galaxies is found to be similar to what is observed locally. This result indicates that the dust content of galaxies is more regulated by their chemical evolution rather than by galaxy luminosity. © 2006 RAS.

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    14
    Citation
    (Scopus)
  • The Tully-Fisher relation of intermediate redshift field and cluster galaxies from Subaru spectroscopy

    O Nakamura, A Aragon-Salamanca, B Milvang-Jensen, N Arimoto, C Ikuta, SP Bamford

    MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY   366 ( 1 ) 144 - 162  2006.02  [Refereed]  [International journal]  [International coauthorship]

    Authorship:Lead author, Corresponding author

     View Summary

    We have carried out spectroscopic observations in four cluster fields using Subaru's FOCAS multislit spectrograph and obtained spectra for 103 bright disc field and cluster galaxies at 0.06 &lt;= z &lt;= 1.20. 77 of these show emission lines, and 33 provide reasonably secure determinations of the galaxies' rotation velocity. The rotation velocities, luminosities, colours and emission-line properties of these galaxies are used to study the possible effects of the cluster environment on the star formation history of the galaxies. Comparing the Tully-Fisher relations of cluster and field galaxies at similar redshifts we find no measurable difference in rest-frame B-band luminosity at a given rotation velocity (the formal difference is 0.18 +/- 0.33). The colours of the cluster emission line galaxies are only marginally redder in rest-frame B-V(by 0.06 +/- 0.04 mag) than the field galaxies in our sample. Taken at face value, these results seem to indicate that bright star-forming cluster spirals are similar to their field counterparts in their star formation properties. However, we find that the fraction of disc galaxies with absorption-line spectra (i.e. with no current star formation) is larger in clusters than in the field by a factor of similar to 3-5. This suggests that the cluster environment has the overall effect of switching off star formation in (at least) some spiral galaxies. To interpret these observational results, we carry out simulations of the possible effects of the cluster environment on the star formation history of disc galaxies and thus their photometric and spectroscopic properties. This allows us to create mock samples of unperturbed 'field' galaxies [with approximately constant star formation rates (SFRs)] and perturbed 'cluster' galaxies with different star formation histories, including star formation truncation, with or without an associated starburst. We show that, if we select only bright galaxies with current star formation (i.e. with emission lines strong enough for rotation-curve measurements), the average colours and luminosities of the 'cluster' galaxies may not be very different from those of galaxies in the 'field' sample, even though their star formation histories may be significantly different. However, the fraction of emission and absorption-line galaxies would change significantly. We also use these simulations to estimate the size of field and cluster galaxy samples that would allow us to differentiate the different star formation scenarios considered. Finally, we find that the rest-frame absolute B-band magnitude of the field galaxies in our sample shows an evolution of -1.30 +/- 1.04 mag per unit redshift at fixed rotation velocity. This indicates that the average SFR of bright disc galaxies evolves more slowly than the universal SFR as determined from ultraviolet, H alpha, far-infrared and radio studies. This suggests the evolution of the universal SFR density is not dominated by bright star-forming disc galaxies, in agreement with previous studies.

    DOI

  • Morphological classification of galaxies using photometric parameters: The concentration index versus the coarseness parameter

    Chisato Yamauchi, Shin Ichi Ichikawa, Mamoru Doi, Naoki Yasuda, Masafumi Yagi, Masataka Fukugita, Sadanori Okamura, Osamu Nakamura, Maki Sekiguchi, Tomotsugu Goto

    Astronomical Journal   130 ( 4 ) 1545 - 1557  2005.10  [Refereed]  [International journal]  [International coauthorship]

     View Summary

    We devise improved photometric parameters for the morphological classification of galaxies using a bright sample from the First Data Release of the Sloan Digital Sky Survey. In addition to using an elliptical aperture concentration index for classification, we introduce a new texture parameter, coarseness, which quantifies deviations from smooth galaxy isophotes. The elliptical aperture concentration index produces morphological classifications that are in appreciably better agreement with visual classifications than those based on circular apertures. With the addition of the coarseness parameter, the success rate of classifying galaxies into early and late types increases to ≃88% with respect to the reference visual classification. A reasonably high success rate (≃68%) is also attained in classifying galaxies into three types, early-type galaxies (E+S0) and early-type (Sa+Sb) and late-type (Sc+Sdm+Im) spiral galaxies. © 2005. The American Astronomical Society. All rights reserved.

    DOI

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    50
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  • The luminosity and color dependence of the galaxy correlation function

    Idit Zehavi, Zheng Zheng, David H. Weinberg, Joshua A. Frieman, Andreas A. Berlind, Michael R. Blanton, Roman Scoccimarro, Ravi K. Sheth, Michael A. Strauss, Issha Kayo, Yasushi Suto, Masataka Fukugita, Osamu Nakamura, Neta A. Bahcall, Jon Brinkmann, James E. Gunn, Greg S. Hennessy, Željko Ivezić, Gillian R. Knapp, Jon Loveday, Avery Meiksin, David J. Schlegel, Donald P. Schneider, Istvan Szapudi, Max Tegmark, Michael S. Vogeley, Donald G. York

    Astrophysical Journal   630 ( 1 I ) 1 - 27  2005.09  [Refereed]  [International journal]  [International coauthorship]

     View Summary

    We study the luminosity and color dependence of the galaxy two-point correlation function in the Sloan Digital Sky Survey, starting from a sample of ∼200,000 galaxies over 2500 deg2. We concentrate our analysis on volume-limited subsamples of specified luminosity ranges, for which we measure the projected correlation function wp(rp), which is directly related to the real-space correlation function ξ(r). The amplitude of wp(rp) rises continuously with luminosity from M r ≈ -17.5 to Mr ≈ -22.5, with the most rapid increase occurring above the characteristic luminosity L* (Mr ≈ -20.5). Over the scales 0.1 h-1 Mpc < rp < 10 h-1 Mpc, the measurements for samples with Mr > -22 can be approximated, imperfectly, by power-law three-dimensional correlation functions ξ(r) = (r/r0)-γ with γ ≈ 1.8 and r0(L*) ≈ 5.0 h-1 Mpc. The brightest subsample, -23 < Mr < -22, has a significantly steeper ξ(r). When we divide samples by color, redder galaxies exhibit a higher amplitude and steeper correlation function at all luminosities. The correlation amplitude of blue galaxies increases continuously with luminosity, but the luminosity dependence for red galaxies is less regular, with bright red galaxies exhibiting the strongest clustering at large scales and faint red galaxies exhibiting the strongest clustering at small scales. We interpret these results using halo occupation distribution (HOD) models assuming concordance cosmological parameters. For most samples, an HOD model with two adjustable parameters fits the wp(rp) data better than a power law, explaining inflections at rp ∼ 1-3 h-1 Mpc as the transition between the one-halo and two-halo regimes of ξ(r). The implied minimum mass for a halo hosting a central galaxy more luminous than L grows steadily, with Mmin ∝ L at low luminosities and a steeper dependence above L*. The mass at which a halo has, on average, one satellite galaxy brighter than L is M1 ≈ 23Mmin(L), at all luminosities. These results imply a conditional luminosity function (at fixed halo mass) in which central galaxies lie far above a Schechter function extrapolation of the satellite population. The HOD model fits nicely explain the color dependence of wp(rp) and the cross correlation between red and blue galaxies. For galaxies with Mr < -21, halos slightly above M min have blue central galaxies, while more massive halos have red central galaxies and predominantly red satellite populations. The fraction of blue central galaxies increases steadily with decreasing luminosity and host halo mass. The strong clustering of faint red galaxies follows from the fact that nearly all of them are satellite systems in high-mass halos. The HOD fitting results are in good qualitative agreement with the predictions of numerical and semianalytic models of galaxy formation. © 2005. The American Astronomical Society. All rights reserved.

    DOI

    Scopus

    627
    Citation
    (Scopus)
  • Metals and dust in intermediate-redshift damped Lyα galaxies

    Pushpa Khare, Varsha P. Kulkarni, James T. Lauroesch, Donald G. York, Arlin P.S. Crotts, Osamu Nakamura

    Astrophysical Journal   616 ( 1 I ) 86 - 109  2004.11  [Refereed]  [International journal]  [International coauthorship]

     View Summary

    We report on spectroscopic observations with the Multiple Mirror Telescope for 11 damped Lyα absorbers (DLAs) or strong DLA candidates at 0.1 < z < 1.5, including several absorbers discovered in the Sloan Digital Sky Survey. In particular, we have measured absorption lines of Zn II, Cr II, Ni II, Fe II, Mn II, Ti II, Ca II, and Si II. These measurements have doubled the sample of Zn and Cr measurements at z < 1. The average relative abundance patterns in these objects are very similar to those found for high-redshift DLAs reported in the literature. Our observations suggest that the dust content, as determined by [Cr/Zn], does not show much change with redshift. We also examine the sample for correlation of [Cr/Zn] with estimates of the quasar reddening. Our data suggest that the global mean metallicity of DLAs, as measured by the gas-phase abundance of Zn, at best shows a weak evolution with redshift over the range 0.4 < z < 3.9.

    DOI

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    68
    Citation
    (Scopus)
  • The Hα luminosity function of morphologically classified galaxies in the sloan digital sky survey

    Osamu Nakamura, Masataka Fukugita, Jon Brinkmann, Donald P. Schneider

    Astronomical Journal   127 ( 5 1781 ) 2511 - 2521  2004.05  [Refereed]  [International journal]  [International coauthorship]

    Authorship:Lead author

     View Summary

    We present a study of the Halpha line emission from a sample of 1482 optically selected, morphologically classified bright galaxies (median redshift of 0.05) derived from the Sloan Digital Sky Survey. The luminosity function is calculated for each morphological class and for the total sample. The luminosity function fitted with the Schechter form gives a slope alpha = -1.43 +/- 0.10 for the total sample, and the Halpha luminosity density is 10(-0.07)(39.31 +/- 0.04)(+0.10) h ergs s(-1) Mpc(-3), where the first error is statistical and the second is systematic. This value is consistent with that derived by Gallego et al. in 1995, but this agreement is caused by a fortuitous cancellation of their neglect of stellar absorption that affects the estimate of extinction corrections and a significant sample incompleteness of emission-line galaxies. The fraction of Halpha emitters monotonically increases from early ( a few percent for elliptical galaxies) to late types (100% for irregular galaxies), whereas strong emitters exist in all classes of morphological types. We find that 83% of the luminosity density comes from spiral galaxies, 5% from irregular galaxies, and 9% from early-type galaxies; a small number of morphologically disturbed galaxies contribute by 3%.

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    53
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  • The search for galaxy clustering around a quasar pair at z = 4.25 found in the sloan digital sky survey

    Masataka Fukugita, Osamu Nakamura, Donald P. Schneider, Mamoru Doi, Nobunari Kashikawa

    Astrophysical Journal   603 ( 2 II )  2004.03  [Refereed]  [International journal]  [International coauthorship]

     View Summary

    We present an investigation of the environment (≈600 kpc radius) of a pair of luminous z = 4.25 quasars, SDSS J1439-0034A and B, separated by 33″. An analysis of high-quality Subaru spectra of the quasars suggests that this configuration is indeed a physical pair and not a gravitational lens; the redshifts are slightly different (although marginally consistent with being the same), and the two spectra have strikingly different features. We search for bright galaxies (L ≳ 0.4L*) having similar redshifts using the V dropout technique and semi-narrowband imaging looking for strong Lyα emission. We find no enhancement in the galaxy density around the quasar pair; its environment differs very little from a general field, with the upper limit of the density enhancement being about 3.5 at a 90% confidence. We infer that bright quasars happened to appear in two normal galaxies in a general field.

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    12
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  • Galaxy types in the Sloan Digital Sky survey using supervised artificial neural networks

    N. M. Ball, J. Loveday, M. Fukugita, O. Nakamura, S. Okamura, J. Brinkmann, R. J. Brunner

    Monthly Notices of the Royal Astronomical Society   348 ( 3 ) 1038 - 1046  2004.03  [Refereed]  [International journal]  [International coauthorship]

     View Summary

    Supervised artificial neural networks are used to predict useful properties of galaxies in the Sloan Digital Sky Survey, in this instance morphological classifications, spectral types and redshifts. By giving the trained networks unseen data, it is found that correlations between predicted and actual properties are around 0.9 with rms errors of order ten per cent. Thus, given a representative training set, these properties may be reliably estimated for galaxies in the survey for which there are no spectra and without human intervention.

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    118
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  • Actively star-forming elliptical galaxies at low redshifts in the Sloan Digital Sky Survey

    Masataka Fukugita, Osamu Nakamura, Edwin L. Turner, Joe Helmboldt, R. C. Nichol

    Astrophysical Journal   601 ( 2 II )  2004.02  [Refereed]  [International journal]  [International coauthorship]

     View Summary

    We report the discovery of actively star-forming elliptical galaxies in a morphologically classified sample of bright galaxies at a low redshift obtained from the Sloan Digital Sky Survey. The emission lines of these galaxies do not show the characteristics of active galactic nuclei, and thus their strong Hα emission is ascribed to star formation with a rate nearly as high as that seen in typical late spiral galaxies. This is taken as evidence against the traditional view that all elliptical galaxies formed early and now evolve only passively. The frequency of such star-forming elliptical galaxies is a few tenths of a percent in the sample but increases to 3% if we include active S0 galaxies. We can identify these galaxies as probable progenitors of so-called E+A galaxies that show the strong Balmer absorption feature of A stars superimposed on an old star population. The approximate match of the abundance of active elliptical plus S0 galaxies to that of E+A galaxies indicates that the duration of such late star formation episodes is of the order of ≲1 Gyr. If we interpret these galaxies as new additions to the early-type galaxy population, and if we assume a power law for their number evolution, the abundance of early-type galaxies at z = 1 is about 30% less than that at z = 0.

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    63
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  • The luminosity function of morphologically classified galaxies in the Sloan Digital Sky Survey

    Osamu Nakamura, Masataka Fukugita, Naoki Yasuda, Jon Loveday, Jon Brinkmann, Donald P. Schneider, Kazuhiro Shimasaku, Mark SubbaRao

    Astronomical Journal   125 ( 4 1768 ) 1682 - 1688  2003.04  [Refereed]  [International journal]  [International coauthorship]

    Authorship:Lead author

     View Summary

    The morphological dependence of the luminosity function is studied, using a sample containing approximately 1500 bright galaxies classified into Hubble types by visual inspection, for a homogeneous sample obtained from the Sloan Digital Sky Survey northern equatorial stripes. Early-type galaxies are shown to have a characteristic magnitude 0.45 mag brighter than that of spiral galaxies in the r* band, consistent with the "universal characteristic luminosity'' in the B band. The shape of the luminosity function differs rather little among different morphological types: we do not see any symptoms of the sharp decline in the faint end of the luminosity function for early-type galaxies at least 2 mag fainter than the characteristic magnitude, although the faint-end behavior shows a slight decline (alpha less than or similar to -1) compared with the total sample. We also show that the rather. at faint-end slope for early-type galaxies is not due to an increasing mixture of dwarf galaxies, which have softer cores. This means that there are numerous faint early-type galaxies with highly concentrated cores.

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    191
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  • Average spectra of massive galaxies in the Sloan Digital Sky Survey

    Daniel J. Eisenstein, David W. Hogg, Masataka Fukugita, Osamu Nakamura, Mariangela Bernardi, Douglas P. Finkbeiner, David J. Schlegel, J. Brinkmann, Andrew J. Connolly, István Csabai, James E. Gunn, Željko Ivezić, Don Q. Lamb, Jon Loveday, Jeffrey A. Munn, Robert C. Nicol, Donald P. Schneider, Michael A. Strauss, Alex Szalay, Don G. York

    Astrophysical Journal   585 ( 2 I ) 694 - 713  2003.03  [Refereed]  [International journal]  [International coauthorship]

     View Summary

    We combine Sloan Digital Sky Survey spectra of 22,000 luminous, red, bulge-dominated galaxies to get high signal-to-noise ratio average spectra in the rest-frame optical and ultraviolet (2600-7000 A). The average spectra of these massive, quiescent galaxies are early type with weak emission lines and with absorption lines indicating an apparent excess of α-elements over solar abundance ratios. We make average spectra of subsamples selected by luminosity, environment, and redshift. The average spectra are remarkable in their similarity. What variations do exist in the average spectra as a function of luminosity and environment are found to form a nearly one-parameter family in spectrum space. We present a high signal-to-noise ratio spectrum of the variation. We measure the properties of the variation with a modified version of the Lick index system and compare to model spectra from stellar population syntheses. The variation may be a combination of age and chemical abundance differences, but the conservative conclusion is that the quality of the data considerably exceeds the current state of the models.

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    88
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  • Sloan Digital Sky Survey: Early Data Release

    Stoughton C., et al. (Including Nakamura O.)

    Astronomical Journal   123   485 - 548  2002.01  [Refereed]  [International journal]  [International coauthorship]

  • On the origin of the color-magnitude relation in the Virgo Cluster

    Alexandre Vazdekis, Harald Kuntschner, Roger L. Davies, Nobuo Arimoto, Osamu Nakamura, Reynier Peletier

    Astrophysical Journal   551 ( 2 PART 2 ) 127 - 130  2001.04  [Refereed]  [International journal]  [International coauthorship]

     View Summary

    We explore the origin of the color-magnitude relation (CMR) of early-type galaxies in the Virgo Cluster using spectra of very high signal-to-noise ratio for six elliptical galaxies selected along the CMR. The data are analyzed using a new evolutionary stellar population synthesis model to generate galaxy spectra at the resolution given by their velocity dispersions. In particular, we use a new age indicator that is virtually free of the effects of metallicity. We find that the luminosity-weighted mean ages of Virgo ellipticals are greater than ∼8 Gyr and show no clear trend with galaxy luminosity. We also find a positive correlation of metallicity with luminosity, color, and velocity dispersion. We conclude that the CMR is driven primarily by a luminosity-metallicity correlation. However, not all elements increase equally with the total metallicity, and we speculate that the CMR may be driven by both a total metallicity increase and a systematic departure from solar abundance ratios of some elements along the CMR. A full understanding of the role played by the total metallicity, abundance ratios, and age in generating the CMR requires the analysis of spectra of very high quality, such as those reported here, for a larger number of galaxies in Virgo and other clusters.

    DOI

    Scopus

    69
    Citation
    (Scopus)

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Books and Other Publications

  • Horizons

    ( Part: Joint translator)

    2010.10 ISBN: 4621082787

    ASIN

Research Projects

  • A Comparative Study of Press Conference of Japanese Government and News coverage on the Fukushima Nuclear Disaster in Its Early Stage

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research

    Project Year :

    2014.04
    -
    2018.03
     

    Shiro SEGAWA, Osamu NAKAMURA

     View Summary

    We tried to analyze the relationship between the three elements, “actual situation of accident,” “press conferences of Japanese government (including TEPCO),” and “coverage of major newspapers” on the Fukushima Daiichi nuclear plant accident (March 2011) in its early stage. When analyzed in quantitative and qualitative way narrowing to “meltdown”, there was a tendency that press conference officers underestimated the actual situation of meltdown and news reporting quoted comments of press conference officers as their major news source. Analyzing news coverage of major newspapers in China as a foreign coverage, it was found that news articles of China quoted Japanese news media as their major news source.
    As important data for our research, we created transcript of Japanese press conferences and constructed a site “FUKUSHIMA STUDY”. Utilizing this transcript, we conducted further research on press conference and news coverage in more detail.

  • Text Analysis of Newspaper Editorials on the Development and Use of Nuclear Energy

    The Sakurada-kai foundation  Political Research Grants

    Project Year :

    2014.04
    -
    2015.03
     

    Osamu NAKAMURA

  • Analysis of Roles and Skills of Science Communicators Based on the Curriculum of Science Communicator Training Programs in the United States

    The Japan Science Society  The Sasakawa Scientific Research Grant

    Project Year :

    2008.04
    -
    2009.03
     

    Osamu NAKAMURA

  • Spectroscopic ages of globular clusters near the center of Our Galaxy

    Foundation for Promotion of Astronomy  Research Grants

    Project Year :

    2001.05
    -
     
     

  • Spectroscopic ages of globular clusters in Our Galaxy

    Sachio Hayakawa Foundation  Overseas Research Support Fund for Young Researchers

    Project Year :

    1999.12
    -
     
     

Misc

  • Astronomical news stories in the two largest Japanese newspaper Companies

    Osamu NAKAMURA

    Proceedings of the Communicating Astronomy with the Public 2018     321 - 322  2018  [International journal]

    Article, review, commentary, editorial, etc. (international conference proceedings)  

  • How to link your questions about news coverage to research?: Introduction to content analysis

    Osamu NAKAMURA

    The Waseda journal of political science and economics   387   10 - 15  2015.03  [Domestic journal]

    Authorship:Lead author, Corresponding author

    Article, review, commentary, editorial, etc. (scientific journal)  

  • Become a Science Communicator!

    Osamu NAKAMURA

    Science Communication   3 ( 2 ) 24 - 25  2014  [Invited]  [Domestic journal]

    Authorship:Lead author, Corresponding author

    Book review, literature introduction, etc.  

  • An Analysis of Science and Technology Communicator Training Curricula in U.S. Universities

    Osamu NAKAMURA

    Proceedings of annual meeting, Japan Society for Science Education   33   317 - 318  2009.08  [Domestic journal]

    Research paper, summary (national, other academic conference)  

  • The Boom of Science Communication in Japan

    Osamu NAKAMURA

    Paper Proceedings of the 6th Asia-Pacific Symposium on Press and Scientific and Social Progress     550 - 551  2008.11  [International journal]

    Article, review, commentary, editorial, etc. (international conference proceedings)  

  • The luminosity, stellar mass, and metallicity of morphologically classified galaxies in the Sloan Digital Sky Survey

    Osamu NAKAMURA

    Astronomical Society of the Pacific Conference Series   399   473 - 474  2008.10  [International journal]

    Article, review, commentary, editorial, etc. (international conference proceedings)  

  • Elemental Abundance Measurements of Low Redshift Damped Lyman-alpha Galaxies

    Meiring J. D, Kulkarni V. P, Khare P, Bechtold J, Cui J, York D. G, Lauroesch J. T, Nakamura O, Crotts A. P. S

    American Astronomical Society Meeting   207  2005.12  [International journal]  [International coauthorship]

    Article, review, commentary, editorial, etc. (international conference proceedings)  

  • Evolution of metals and dust in the universe

    Khare P, Kulkarni V. P, Lauroesch J. T, Fall, S. M, York D. G, Welty, D. E, Crotts A. P. S, Truran, J. W, Nakamura O

    Bulletin of the Astronomical Society of India   33 ( 2 ) 219  2005.06  [International journal]  [International coauthorship]

    Article, review, commentary, editorial, etc. (bulletin of university, research institution)  

  • The Sloan Digital Sky Survey QSO absorption line catalogue

    Donald G. York, Daniel Vanden Berk, Gordon T. Richards, Arlin P.S. Crotts, Pushpa Khare, James Lauroesch, Martin Lemoine, Scott Burles, Mariangela Bernardi, Francisco J. Castander, Josh Frieman, Jon Loveday, Avery Meiksin, Robert Nichol, David Schlegel, Donald P. Schneider, Mark Subbarao, Chris Stoughton, Alex Szalay, Brian Yanny, Yusra Alsayyad, Abhishek Kumar, Britt Lundgren, Natela Shanidze, Johnny Vanlandingham, Matthew Wood, Britt Baugher, Jon Brinkmann, Robert Brunner, Masaaka Fukugita, Patrick B. Hall, Timothy M. Heckman, Lewis M. Hobbs, Craig J. Hogan, Lam Hui, Edward B. Jenkins, Daniel Kunstz, Brice Menard, Osamu Nakamura, Jean M. Quashnock, Michael Stein, Aniruddha R. Thakar, David Turnshek, Daniel E. Welty

    Proceedings of the International Astronomical Union   1 ( C199 ) 58 - 64  2005  [International journal]  [International coauthorship]

    Article, review, commentary, editorial, etc. (international conference proceedings)  

     View Summary

    The spectra of the Sloan Digital Sky Survey (SDSS) are being used to construct a catalogue of QSO absorption lines, for use in studies of abundances, relevant radiation fields, number counts as a function of redshift, and other matters, including the evolution of these parameters. The catalogue includes intervening, associated, and BAL absorbers, in order to allow a clearer definition of the relationships between these three classes. We describe the motivation for and the data products of the project to build the SDSS QSO absorption line catalogue. © 2005 International Astronomical Union.

    DOI

  • A search for galaxy clustering at z=4 using a Sloan Digital Sky Survey quasar pair

    Nakamura O, Fukugita M, Doi M, Kashikawa N, Schneider D. P

    Astronomical Society of the Pacific Conference Series   289   243 - 246  2003.05  [International journal]  [International coauthorship]

    Article, review, commentary, editorial, etc. (international conference proceedings)  

  • Compariosn of Nucleosynthesis Models

    Osamu NAKAMURA

    Proceedings of the 187th Symposium of the International Astronomical Union     230  2002  [International journal]

    Article, review, commentary, editorial, etc. (international conference proceedings)  

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Syllabus

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Sub-affiliation

  • Affiliated organization   Global Education Center

  • Faculty of Political Science and Economics   Graduate School of Political Science

  • Faculty of Science and Engineering   Graduate School of Advanced Science and Engineering