The Local Hole: a galaxy under-density covering 90% of sky to ~200 Mpc. (arXiv:2107.08505v2 [astro-ph.CO] UPDATED)

The Local Hole: a galaxy under-density covering 90% of sky to ~200 Mpc. (arXiv:2107.08505v2 [astro-ph.CO] UPDATED)
<a href="http://arxiv.org/find/astro-ph/1/au:+Wong_J/0/1/0/all/0/1">Jonathan H.W. Wong</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Shanks_T/0/1/0/all/0/1">T. Shanks</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Metcalfe_N/0/1/0/all/0/1">N. Metcalfe</a> (Centre for Extragalactic Astronomy, Department of Physics, Durham University, Durham, England)

We investigate the `Local Hole’, an anomalous under-density in the local
galaxy environment, by extending our previous galaxy $K-$band number-redshift
and number-magnitude counts to $approx 90%$ of the sky. Our redshift samples
are taken from the 2MASS Redshift Survey (2MRS) and the 2M++ catalogues,
limited to $K<11.5$. We find that both surveys are in good agreement, showing
an $approx 21-22%$ under-density at $z<0.075$ when compared to our
homogeneous counts model that assumes the same luminosity function and other
parameters as Whitbourn & Shanks (2014). Using the Two Micron All Sky Survey
(2MASS) for $n(K)$ galaxy counts, we measure an under-density relative to this
model of $20pm 2 %$ at $K<11.5$, which is consistent in both form and scale
with the observed $n(z)$ under-density. To examine further the accuracy of the
counts model, we compare its prediction for the fainter $n(K)$ counts of the
Galaxy and Mass Assembly (GAMA) survey. We further compare these data with a
model assuming the parameters of Lavaux & Hudson (2011} whose previous study
found little evidence for the Local Hole. At $13<K<16$ we find a significantly
better fit for our model, arguing for our higher luminosity function
normalisation. Although our implied under-density of $approx 20%$ means local
measurements of the Hubble Constant have been over-estimated by $approx3$%,
such a scale of under-density is in tension with a global $Lambda$CDM
cosmology at an $approx3sigma$ level.

We investigate the `Local Hole’, an anomalous under-density in the local
galaxy environment, by extending our previous galaxy $K-$band number-redshift
and number-magnitude counts to $approx 90%$ of the sky. Our redshift samples
are taken from the 2MASS Redshift Survey (2MRS) and the 2M++ catalogues,
limited to $K<11.5$. We find that both surveys are in good agreement, showing
an $approx 21-22%$ under-density at $z<0.075$ when compared to our
homogeneous counts model that assumes the same luminosity function and other
parameters as Whitbourn & Shanks (2014). Using the Two Micron All Sky Survey
(2MASS) for $n(K)$ galaxy counts, we measure an under-density relative to this
model of $20pm 2 %$ at $K<11.5$, which is consistent in both form and scale
with the observed $n(z)$ under-density. To examine further the accuracy of the
counts model, we compare its prediction for the fainter $n(K)$ counts of the
Galaxy and Mass Assembly (GAMA) survey. We further compare these data with a
model assuming the parameters of Lavaux & Hudson (2011} whose previous study
found little evidence for the Local Hole. At $13<K<16$ we find a significantly
better fit for our model, arguing for our higher luminosity function
normalisation. Although our implied under-density of $approx 20%$ means local
measurements of the Hubble Constant have been over-estimated by $approx3$%,
such a scale of under-density is in tension with a global $Lambda$CDM
cosmology at an $approx3sigma$ level.

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