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The local hole revealed by galaxy counts and redshifts

Whitbourn, J.R.; Shanks, T.

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Authors

J.R. Whitbourn

T. Shanks



Abstract

The redshifts of ≈250 000 galaxies are used to study the local hole and its associated peculiar velocities. The sample, compiled from the 6dF Galaxy Redshift Survey and Sloan Digital Sky Survey, provides wide sky coverage to a depth of ≈300 h−1 Mpc. We have therefore examined K- and r-limited galaxy redshift distributions and number counts to map the local density field. Comparing observed galaxy n(z) distributions to homogeneous models in three large regions of the high-latitude sky, we find evidence for underdensities ranging from ≈4–40 per cent in these regions to depths of ≈150 h−1 Mpc with the deepest underdensity being over the southern Galactic cap. Using the Galaxy and Mass Assembly survey, we then establish the normalization of galaxy counts at fainter magnitudes and thus confirm that the underdensity over all three fields at K < 12.5 is ≈15 ± 3 per cent. Finally, we further use redshift catalogues to map sky-averaged peculiar velocities over the same areas using the average redshift–magnitude, z¯(m), technique of Soneira. After accounting for the direct effect of the large-scale structure on z¯(m), we can then search for peculiar velocities. Taking all three regions into consideration, the data reject at the ≈4σ level the idea that we have recovered the cosmic microwave background rest frame in the volume probed. We therefore conclude that there is some consistent evidence from both counts and Hubble diagrams for a ‘local hole’ with an ≈150 h−1 Mpc underdensity that deeper counts and redshifts in the northern Galactic cap suggest may extend to ≈300 h−1 Mpc.

Citation

Whitbourn, J., & Shanks, T. (2014). The local hole revealed by galaxy counts and redshifts. Monthly Notices of the Royal Astronomical Society, 437(3), 2146-2162. https://doi.org/10.1093/mnras/stt2024

Journal Article Type Article
Publication Date Jan 21, 2014
Deposit Date Jun 2, 2014
Publicly Available Date Jun 4, 2014
Journal Monthly Notices of the Royal Astronomical Society
Print ISSN 0035-8711
Electronic ISSN 1365-2966
Publisher Royal Astronomical Society
Peer Reviewed Peer Reviewed
Volume 437
Issue 3
Pages 2146-2162
DOI https://doi.org/10.1093/mnras/stt2024
Keywords Methods: analytical, Galaxies: general, Local Group, Large-scale structure of Universe, Infrared: galaxies

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Copyright Statement
This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society © 2013 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society.







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