3 years ago

Cosmic web dependence of galaxy clustering and quenching in SDSS.

Ying Zu, John A. Peacock, Rachel Mandelbaum, Shadab Alam

Galaxies exhibit different clustering and quenching properties in clusters, filaments, and the field, but it is still uncertain whether such differences are imprints of the tidal environment on galaxy formation, or if they reflect the variation of the underlying halo mass function across the cosmic web. We measure the dependence of galaxy clustering and quenching on the cosmic web in the Sloan Digital Sky Survey, characterized by the combination of spherical overdensity $\delta_8$ and tidal anisotropy $\alpha_5$ centred on each galaxy. We find that the galaxy clustering is a non-monotonic function of either $\delta_8$ or $\alpha_5$, and the large-scale galaxy bias shows complex and rich behaviour on the $\delta_8$ vs. $\alpha_5$ plane. Using the mean galaxy colour as a proxy for the average quenched level of galaxies, we find that galaxy quenching is primarily a function of $\delta_8$, with some subtle yet non-trivial dependence on $\alpha_5$ at fixed $\delta_8$. The quenched galaxies generally show stronger small-scale clustering than the star-forming ones at fixed $\delta_8$ or $\alpha_5$, while the characteristic scale at which the amplitude of clustering becomes comparable for both galaxy population varies with $\delta_8$ and $\alpha_5$. Remarkably, those observed cosmic web dependences of galaxy clustering and quenching can be well reproduced by a mock galaxy catalogue constructed from the iHOD model, which places quenched and star-forming galaxies inside dark matter haloes based on the stellar-to-halo mass relation and the halo quenching model --- the $\delta_8$ and $\alpha_5$ dependences of iHOD galaxies are solely derived from the cosmic web modulation of the halo mass function. The success of the simple iHOD model suggests that any direct effect of the large-scale tidal field on galaxy formation is not currently detectable.[Abridged]

Publisher URL: http://arxiv.org/abs/1801.04878

DOI: arXiv:1801.04878v1

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