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1703.09219
Mapping stellar content to dark matter haloes - III. Environmental dependence and conformity of galaxy colors
Zu, Mandelbaum
Recent studies suggest that the quenching properties of galaxies are correlated over several mega-parsecs. The large-scale "galactic conformity" phenomenon around central galaxies has been regarded as a potential signature of "galaxy assembly bias" or re-heating", both of which interpret conformity as a result of direct environmental effects acting on galaxy formation. Building on the iHOD halo quenching framework developed in Zu & Mandelbaum (15,16), discover that the fiducial halo mass quenching model, without any galaxy assembly bias, can successfully explain the overall environmental dependence and the conformity of galaxy colors in SDSS, as measured by the mark correlation functions of galaxy colors and the red galaxy fractions around isolated primaries, respectively. The fiducial iHOD halo quenching mock also correctly predicts the differences in the spatial clustering and galaxy-galaxy lensing signals between the more vs. less red galaxy subsamples, split by the red-sequence ridge-line at fixed stellar mass. Meanwhile, models that tie galaxy colors fully or partially to halo assembly bias have difficulties in matching all these observables simultaneously. Therefore, demonstrate that the observed environmental dependence of galaxy colors can be naturally explained by the combination of 1) halo quenching and 2) the variation of halo mass function with environment --- an indirect environmental effect mediated by two separate physical processes.
1703.09233
Mapping dark matter on the celestial sphere with weak gravitational lensing
Wallis, McEwen, Kitching, Leistedt, Plouviez
Convergence maps of the integrated matter distribution are a key science result from WL surveys. To date, recovering convergence maps has been performed using a planar approximation of the celestial sphere. However, with the increasing area of sky covered by DE experiments, such as Euclid, LSST, and WFIRST, this assumption will no longer be valid. Extend the Kaiser-Squires technique for recovering convergence fields, restricted previously to the plane, to the spherical setting. Through simulations, study the error introduced by planar approximations. Moreover, examine how best to recover convergence maps in the planar setting, considering a variety of different projection and defining the local rotations that are required while projecting spin fields such as cosmic shear. For the sky coverages typical of future surveys, errors introduced by projection effects can be of order tens of percent, exceeding 50% in some cases. The stereographic projection, which is confirmed and so preserves local angles, is the most effective planar projection. In any case, these errors can be avoided entirely by recovering convergence fields directly on the celestial sphere. Apply the spherical Kaiser-Squires mass-mapping method presented to the DES science verification data to recover convergence maps directly on the celestial sphere.
1703.09219
Mapping stellar content to dark matter haloes - III. Environmental dependence and conformity of galaxy colors
Zu, Mandelbaum
Recent studies suggest that the quenching properties of galaxies are correlated over several mega-parsecs. The large-scale "galactic conformity" phenomenon around central galaxies has been regarded as a potential signature of "galaxy assembly bias" or re-heating", both of which interpret conformity as a result of direct environmental effects acting on galaxy formation. Building on the iHOD halo quenching framework developed in Zu & Mandelbaum (15,16), discover that the fiducial halo mass quenching model, without any galaxy assembly bias, can successfully explain the overall environmental dependence and the conformity of galaxy colors in SDSS, as measured by the mark correlation functions of galaxy colors and the red galaxy fractions around isolated primaries, respectively. The fiducial iHOD halo quenching mock also correctly predicts the differences in the spatial clustering and galaxy-galaxy lensing signals between the more vs. less red galaxy subsamples, split by the red-sequence ridge-line at fixed stellar mass. Meanwhile, models that tie galaxy colors fully or partially to halo assembly bias have difficulties in matching all these observables simultaneously. Therefore, demonstrate that the observed environmental dependence of galaxy colors can be naturally explained by the combination of 1) halo quenching and 2) the variation of halo mass function with environment --- an indirect environmental effect mediated by two separate physical processes.
1703.09233
Mapping dark matter on the celestial sphere with weak gravitational lensing
Wallis, McEwen, Kitching, Leistedt, Plouviez
Convergence maps of the integrated matter distribution are a key science result from WL surveys. To date, recovering convergence maps has been performed using a planar approximation of the celestial sphere. However, with the increasing area of sky covered by DE experiments, such as Euclid, LSST, and WFIRST, this assumption will no longer be valid. Extend the Kaiser-Squires technique for recovering convergence fields, restricted previously to the plane, to the spherical setting. Through simulations, study the error introduced by planar approximations. Moreover, examine how best to recover convergence maps in the planar setting, considering a variety of different projection and defining the local rotations that are required while projecting spin fields such as cosmic shear. For the sky coverages typical of future surveys, errors introduced by projection effects can be of order tens of percent, exceeding 50% in some cases. The stereographic projection, which is confirmed and so preserves local angles, is the most effective planar projection. In any case, these errors can be avoided entirely by recovering convergence fields directly on the celestial sphere. Apply the spherical Kaiser-Squires mass-mapping method presented to the DES science verification data to recover convergence maps directly on the celestial sphere.
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