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تسجيل مستخدم جديدThe Galaxy Luminosity and Selection Functions of the NOG Sample
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In order to map the galaxy density field on small scales in the local universe, we use the Nearby Optical Galaxy (NOG) sample, which is currently one of the largest, nearly complete, magnitude-limited ($Bleq$ 14 mag), all-sky sample of nearby optical galaxies ($sim$ 6400 galaxies with cz< 5500 km/s). We have corrected the redshift-dependent distances of these galaxies for non-cosmological motions by means of peculiar velocity field models. Relying on group assignments and on total B magnitudes fully corrected for internal and Galactic extinctions, we determine the total and morphological-type specific luminosity functions for field and grouped galaxies using their locations in real distance space. The related determination of the selection function is meant to be an important step in recovering the galaxy density field on small scales from the NOG sample. Local galaxy density parameters will be used in statistical studies of environmental effects on galaxy properties.
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In order to map the galaxy density field in the local universe, we select the Nearby Optical Galaxy (NOG) sample, which is a distance-limited (cz < 6000 km/s) and magnitude--limited (B < 14 mag) sample of 7076 optical galaxies which covers 2/3 (8.29
sr) of the sky (|b|>20^{circ}) and has a good completeness in redshift (98%). In order to trace the galaxy density field on small scales, we identify the NOG galaxy systems by means of both the hierarchical and the percolation (friends of friends) methods. The NOG provides high resolution in both spatial sampling of the nearby universe and morphological galaxy classification. The NOG is meant to be the first step towards the construction of a statistically well-controlled galaxy sample with homogenized photometric data covering most of the celestial sphere.
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14 mag) sample of 7076 optical galaxies which covers 2/3 (8.29 sr) of the sky (|b|>20). We have replaced ``true distances measurements for all the objects in order to correct for redshif distortions. Using homogenized photometric information for the whole sample, NOG is meant to be an approximation to a homogeneous all-sky 3D optically selected and statistically well-controlled galaxy sample that probes in great detail volumes of cosmological interest. Our goal is to construct a reliable, robust and unbiased field of density contrasts covering interesting regions of galaxy and mass overdensities of the local universe.
Gravitational lensing magnification modifies the observed spatial distribution of galaxies and can severely bias cosmological probes of large-scale structure if not accurately modelled. Standard approaches to modelling this magnification bias may not
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