Detecting the relativistic bispectrum in 21cm intensity maps. (arXiv:2009.06197v2 [astro-ph.CO] UPDATED)
<a href="http://arxiv.org/find/astro-ph/1/au:+Jolicoeur_S/0/1/0/all/0/1">Sheean Jolicoeur</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Maartens_R/0/1/0/all/0/1">Roy Maartens</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Weerd_E/0/1/0/all/0/1">Eline M. De Weerd</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Umeh_O/0/1/0/all/0/1">Obinna Umeh</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Clarkson_C/0/1/0/all/0/1">Chris Clarkson</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Camera_S/0/1/0/all/0/1">Stefano Camera</a>

We investigate the detectability of leading-order relativistic effects in the
bispectrum of future 21cm intensity mapping surveys. The relativistic signal
arises from Doppler and other line-of-sight effects in redshift space. In the
power spectrum of a single tracer, these effects are suppressed by a factor
$cH^2/k^2$. By contrast, in the bispectrum the relativistic signal couples to
short-scale modes, leading to an imaginary contribution that scales as $cH/k$,
thus increasing the possibility of detection. Previous work has shown that this
relativistic signal is detectable in a Stage IV H$alpha$ galaxy survey. {We
show that the signal is also detectable by next-generation 21cm intensity maps,
but typically with a lower signal-to-noise, due to foreground and telescope
beam effects.

We investigate the detectability of leading-order relativistic effects in the
bispectrum of future 21cm intensity mapping surveys. The relativistic signal
arises from Doppler and other line-of-sight effects in redshift space. In the
power spectrum of a single tracer, these effects are suppressed by a factor
$cH^2/k^2$. By contrast, in the bispectrum the relativistic signal couples to
short-scale modes, leading to an imaginary contribution that scales as $cH/k$,
thus increasing the possibility of detection. Previous work has shown that this
relativistic signal is detectable in a Stage IV H$alpha$ galaxy survey. {We
show that the signal is also detectable by next-generation 21cm intensity maps,
but typically with a lower signal-to-noise, due to foreground and telescope
beam effects.

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