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Steven Phillipps - One of the best experts on this subject based on the ideXlab platform.

  • galaxy and mass assembly gama maximum Likelihood Determination of the luminosity function and its evolution
    Monthly Notices of the Royal Astronomical Society, 2015
    Co-Authors: Jon Loveday, Peder Norberg, I K Baldry, Joss Blandhawthorn, Sarah Brough, M J I Brown, Simon P Driver, Lee S Kelvin, Steven Phillipps
    Abstract:

    We describe modifications to the joint stepwise maximum-Likelihood method of Cole in order to simultaneously fit the Galaxy and Mass Assembly II galaxy luminosity function (LF), corrected for radial density variations, and its evolution with redshift. The whole sample is reasonably well fitted with luminosity (Qe) and density (Pe) evolution parameters Qe, Pe ≈ 1.0, 1.0 but with significant degeneracies characterized by Qe ≈ 1.4 − 0.4Pe. Blue galaxies exhibit larger luminosity density evolution than red galaxies, as expected. We present the evolution-corrected r-band LF for the whole sample and for blue and red subsamples, using both Petrosian and Sersic magnitudes. Petrosian magnitudes miss a substantial fraction of the flux of de Vaucouleurs profile galaxies: the Sersic LF is substantially higher than the Petrosian LF at the bright end.

  • galaxy and mass assembly gama maximum Likelihood Determination of the luminosity function and its evolution
    arXiv: Astrophysics of Galaxies, 2015
    Co-Authors: Jon Loveday, Peder Norberg, I K Baldry, Joss Blandhawthorn, Sarah Brough, M J I Brown, Simon P Driver, Lee S Kelvin, Steven Phillipps
    Abstract:

    We describe modifications to the joint stepwise maximum Likelihood method of Cole (2011) in order to simultaneously fit the GAMA-II galaxy luminosity function (LF), corrected for radial density variations, and its evolution with redshift. The whole sample is reasonably well-fit with luminosity (Qe) and density (Pe) evolution parameters Qe, Pe = 1.0, 1.0 but with significant degeneracies characterized by Qe = 1.4 - 0.4Pe. Blue galaxies exhibit larger luminosity density evolution than red galaxies, as expected. We present the evolution-corrected r-band LF for the whole sample and for blue and red sub-samples, using both Petrosian and Sersic magnitudes. Petrosian magnitudes miss a substantial fraction of the flux of de Vaucouleurs profile galaxies: the Sersic LF is substantially higher than the Petrosian LF at the bright end.

Simon P Driver - One of the best experts on this subject based on the ideXlab platform.

  • galaxy and mass assembly gama maximum Likelihood Determination of the luminosity function and its evolution
    Monthly Notices of the Royal Astronomical Society, 2015
    Co-Authors: Jon Loveday, Peder Norberg, I K Baldry, Joss Blandhawthorn, Sarah Brough, M J I Brown, Simon P Driver, Lee S Kelvin, Steven Phillipps
    Abstract:

    We describe modifications to the joint stepwise maximum-Likelihood method of Cole in order to simultaneously fit the Galaxy and Mass Assembly II galaxy luminosity function (LF), corrected for radial density variations, and its evolution with redshift. The whole sample is reasonably well fitted with luminosity (Qe) and density (Pe) evolution parameters Qe, Pe ≈ 1.0, 1.0 but with significant degeneracies characterized by Qe ≈ 1.4 − 0.4Pe. Blue galaxies exhibit larger luminosity density evolution than red galaxies, as expected. We present the evolution-corrected r-band LF for the whole sample and for blue and red subsamples, using both Petrosian and Sersic magnitudes. Petrosian magnitudes miss a substantial fraction of the flux of de Vaucouleurs profile galaxies: the Sersic LF is substantially higher than the Petrosian LF at the bright end.

  • galaxy and mass assembly gama maximum Likelihood Determination of the luminosity function and its evolution
    arXiv: Astrophysics of Galaxies, 2015
    Co-Authors: Jon Loveday, Peder Norberg, I K Baldry, Joss Blandhawthorn, Sarah Brough, M J I Brown, Simon P Driver, Lee S Kelvin, Steven Phillipps
    Abstract:

    We describe modifications to the joint stepwise maximum Likelihood method of Cole (2011) in order to simultaneously fit the GAMA-II galaxy luminosity function (LF), corrected for radial density variations, and its evolution with redshift. The whole sample is reasonably well-fit with luminosity (Qe) and density (Pe) evolution parameters Qe, Pe = 1.0, 1.0 but with significant degeneracies characterized by Qe = 1.4 - 0.4Pe. Blue galaxies exhibit larger luminosity density evolution than red galaxies, as expected. We present the evolution-corrected r-band LF for the whole sample and for blue and red sub-samples, using both Petrosian and Sersic magnitudes. Petrosian magnitudes miss a substantial fraction of the flux of de Vaucouleurs profile galaxies: the Sersic LF is substantially higher than the Petrosian LF at the bright end.

Jon Loveday - One of the best experts on this subject based on the ideXlab platform.

  • galaxy and mass assembly gama maximum Likelihood Determination of the luminosity function and its evolution
    Monthly Notices of the Royal Astronomical Society, 2015
    Co-Authors: Jon Loveday, Peder Norberg, I K Baldry, Joss Blandhawthorn, Sarah Brough, M J I Brown, Simon P Driver, Lee S Kelvin, Steven Phillipps
    Abstract:

    We describe modifications to the joint stepwise maximum-Likelihood method of Cole in order to simultaneously fit the Galaxy and Mass Assembly II galaxy luminosity function (LF), corrected for radial density variations, and its evolution with redshift. The whole sample is reasonably well fitted with luminosity (Qe) and density (Pe) evolution parameters Qe, Pe ≈ 1.0, 1.0 but with significant degeneracies characterized by Qe ≈ 1.4 − 0.4Pe. Blue galaxies exhibit larger luminosity density evolution than red galaxies, as expected. We present the evolution-corrected r-band LF for the whole sample and for blue and red subsamples, using both Petrosian and Sersic magnitudes. Petrosian magnitudes miss a substantial fraction of the flux of de Vaucouleurs profile galaxies: the Sersic LF is substantially higher than the Petrosian LF at the bright end.

  • galaxy and mass assembly gama maximum Likelihood Determination of the luminosity function and its evolution
    arXiv: Astrophysics of Galaxies, 2015
    Co-Authors: Jon Loveday, Peder Norberg, I K Baldry, Joss Blandhawthorn, Sarah Brough, M J I Brown, Simon P Driver, Lee S Kelvin, Steven Phillipps
    Abstract:

    We describe modifications to the joint stepwise maximum Likelihood method of Cole (2011) in order to simultaneously fit the GAMA-II galaxy luminosity function (LF), corrected for radial density variations, and its evolution with redshift. The whole sample is reasonably well-fit with luminosity (Qe) and density (Pe) evolution parameters Qe, Pe = 1.0, 1.0 but with significant degeneracies characterized by Qe = 1.4 - 0.4Pe. Blue galaxies exhibit larger luminosity density evolution than red galaxies, as expected. We present the evolution-corrected r-band LF for the whole sample and for blue and red sub-samples, using both Petrosian and Sersic magnitudes. Petrosian magnitudes miss a substantial fraction of the flux of de Vaucouleurs profile galaxies: the Sersic LF is substantially higher than the Petrosian LF at the bright end.

Roberto Accorsi - One of the best experts on this subject based on the ideXlab platform.

  • simultaneous maximum Likelihood Determination of focal length and source position for point source experiments with pinhole collimation
    IEEE Transactions on Nuclear Science, 2005
    Co-Authors: S Metzler, N H Patil, Roberto Accorsi
    Abstract:

    A simple procedure to determine the focal length of a pinhole collimator is presented, which is important for planar and SPECT imaging. The procedure involves the use of a point source and three linear stages. The source is moved by carefully controlled relative shifts in two dimensions to a number of different positions within a plane nearly perpendicular to the detector's plane. For each position a projection is acquired. The focal length is calculated from the shift in the centroid of the projections via a maximum-Likelihood fit. A useful byproduct of the procedure is calibration of the position of the source, which can then be used for planar imaging studies such as sensitivity and point-spread function. This calibration maps the coordinate system of the stages to the coordinate system of the aperture. The method was experimentally validated for three different focal lengths.

  • simultaneous maximum Likelihood Determination of focal length and source position for point source experiments with pinhole collimation
    IEEE Symposium Conference Record Nuclear Science 2004., 2004
    Co-Authors: S Metzler, N H Patil, Roberto Accorsi
    Abstract:

    Experimental measurements with a point source provide a valuable tool for characterizing the point-spread function and sensitivity of pinhole collimation. These results may test new theoretical formulas or provide calibrations for reconstructing data. Extracting results from point-source data is also more tenable than from more complex phantoms. However, one limiting factor with point-source measurements for high-precision tests is the Determination of the position of the point source relative to the aperture. A maximum-Likelihood fit may be used to determine simultaneously the position of the point source and the collimator's focal length. In this study, a robotic 1D linear stage was mounted on a box collimator to change the angle of the point source with respect to the aperture's axis of symmetry; the perpendicular height above the aperture, y, was unchanged by this stage. A second stage controlled y. A total of 66 projections (11 angle; 6 y) were acquired for each of three different focal lengths. The projections' centroids were fit to equations predicting their value as a function of focal length, point-source position, and electronic read-out. The differences in focal length from a reference were -6.2, 7.6, and 12.8 mm. The focal length to the reference was 176.1 mm. Measured focal lengths in each case agreed well with micrometer measurements. Differences in focal length and y also agreed well with micrometer measurements. Standard deviations of focal length and y were about 0.5 mm. In conclusion, this method can determine point-source position during experiment setup and measure focal length to within a millimeter.

Peder Norberg - One of the best experts on this subject based on the ideXlab platform.

  • galaxy and mass assembly gama maximum Likelihood Determination of the luminosity function and its evolution
    Monthly Notices of the Royal Astronomical Society, 2015
    Co-Authors: Jon Loveday, Peder Norberg, I K Baldry, Joss Blandhawthorn, Sarah Brough, M J I Brown, Simon P Driver, Lee S Kelvin, Steven Phillipps
    Abstract:

    We describe modifications to the joint stepwise maximum-Likelihood method of Cole in order to simultaneously fit the Galaxy and Mass Assembly II galaxy luminosity function (LF), corrected for radial density variations, and its evolution with redshift. The whole sample is reasonably well fitted with luminosity (Qe) and density (Pe) evolution parameters Qe, Pe ≈ 1.0, 1.0 but with significant degeneracies characterized by Qe ≈ 1.4 − 0.4Pe. Blue galaxies exhibit larger luminosity density evolution than red galaxies, as expected. We present the evolution-corrected r-band LF for the whole sample and for blue and red subsamples, using both Petrosian and Sersic magnitudes. Petrosian magnitudes miss a substantial fraction of the flux of de Vaucouleurs profile galaxies: the Sersic LF is substantially higher than the Petrosian LF at the bright end.

  • galaxy and mass assembly gama maximum Likelihood Determination of the luminosity function and its evolution
    arXiv: Astrophysics of Galaxies, 2015
    Co-Authors: Jon Loveday, Peder Norberg, I K Baldry, Joss Blandhawthorn, Sarah Brough, M J I Brown, Simon P Driver, Lee S Kelvin, Steven Phillipps
    Abstract:

    We describe modifications to the joint stepwise maximum Likelihood method of Cole (2011) in order to simultaneously fit the GAMA-II galaxy luminosity function (LF), corrected for radial density variations, and its evolution with redshift. The whole sample is reasonably well-fit with luminosity (Qe) and density (Pe) evolution parameters Qe, Pe = 1.0, 1.0 but with significant degeneracies characterized by Qe = 1.4 - 0.4Pe. Blue galaxies exhibit larger luminosity density evolution than red galaxies, as expected. We present the evolution-corrected r-band LF for the whole sample and for blue and red sub-samples, using both Petrosian and Sersic magnitudes. Petrosian magnitudes miss a substantial fraction of the flux of de Vaucouleurs profile galaxies: the Sersic LF is substantially higher than the Petrosian LF at the bright end.