Dipolar modulation in number counts of WISE-2MASS sources

Abstract

We test the statistical isotropy of the universe by analyzing the distribution of WISE extragalactic sources that were also observed by 2MASS. We pay particular attention to color cuts and foreground marginalization in order to cull a uniform sample of extragalactic objects and avoid stars. We detect a dipole gradient in the number-counts with an amplitude of $\sim$0.05, somewhat larger than expectations based on local structures corresponding to the depth and (independently measured) bias of our WISE-2MASS sources. The direction of the dipole, $(l,b)\simeq (310{}^{\circ },-15{}^{\circ })$, is in reasonably good agreement with that found previously in the (shallower) 2MASS Extended Source Catalog alone. Interestingly, the dipole direction is not far from the direction of the dipolar modulation in the CMB found by Planck, and also fairly closely matches large-scale-structure bulk-flow directions found by various groups using galaxies and type Ia supernovae. It is difficult, however, to draw specific conclusions from the near-agreement of these directions.

5 pages, 3 figures. v2: extinction correction added; minor changes in results

References in corpus (5)

• Dipoles in the Sky
• Constraints on cosmic hemispherical power anomalies from quasars
• Cross-correlation of 2MASS and WMAP3: Implications for the Integrated Sachs-Wolfe effect
• The peculiar velocity field: constraining the tilt of the Universe
• Gauging the cosmic microwave background

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• Cosmological Solutions through Gravitational Decoupling in $f(\mathcal{R},\mathcal{T},{\mathcal{R}}_{\mathrm{ab}}{\mathcal{T}}^{\mathrm{ab}})$ Gravity
• Anisotropy in the all-sky distribution of galaxy morphological types
• Light propagation in a homogeneous and anisotropic universe
• The angular scale of homogeneity in the Local Universe with the SDSS blue galaxies
• Probing statistical isotropy of cosmological radio sources using SKA
• Probing the Cosmological Principle with the CSST Photometric Survey