Putting binning in the bin: strong evidence for a continuous relationship between galaxy starburstiness and AGN power. (arXiv:2001.11573v1 [astro-ph.GA])

Putting binning in the bin: strong evidence for a continuous relationship between galaxy starburstiness and AGN power. (arXiv:2001.11573v1 [astro-ph.GA])
<a href="http://arxiv.org/find/astro-ph/1/au:+Grimmett_L/0/1/0/all/0/1">L. P. Grimmett</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Mullaney_J/0/1/0/all/0/1">J. R. Mullaney</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Bernhard_E/0/1/0/all/0/1">E. P. Bernhard</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Harrison_C/0/1/0/all/0/1">C. M. Harrison</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Alexander_D/0/1/0/all/0/1">D. M. Alexander</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Stanley_F/0/1/0/all/0/1">F. Stanley</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Masoura_V/0/1/0/all/0/1">V. A. Masoura</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Walters_K/0/1/0/all/0/1">K. Walters</a>

Studies investigating the relationship between star formation rate (SFR) and
AGN power often rely on averaging techniques — such as stacking — to
incorporate information from non-detections. However, averages, and especially
means, can be strongly affected by outliers and can therefore give a misleading
indication of the “typical” case. Recently, a number of studies have taken a
step further by binning their sample in terms of AGN power, and investigating
how the SFR distribution differs between these bins. These bin thresholds are
often weakly motivated, and binning implicitly assumes that sources within the
same bin have similar (or even identical) properties. In this paper, we
investigate whether the main sequence-normalised SFR (i.e., starburstiness,
$R_{rm MS}$) distribution changes continuously as a function of AGN power,
using a hierarchical Bayesian model that completely removes the need to bin. In
doing so, we find strong evidence that the $R_{rm MS}$ distribution changes
with AGN power, such that higher X-ray luminosity AGNs have a tighter physical
connection to the star forming process than lower luminosity AGNs.

Studies investigating the relationship between star formation rate (SFR) and
AGN power often rely on averaging techniques — such as stacking — to
incorporate information from non-detections. However, averages, and especially
means, can be strongly affected by outliers and can therefore give a misleading
indication of the “typical” case. Recently, a number of studies have taken a
step further by binning their sample in terms of AGN power, and investigating
how the SFR distribution differs between these bins. These bin thresholds are
often weakly motivated, and binning implicitly assumes that sources within the
same bin have similar (or even identical) properties. In this paper, we
investigate whether the main sequence-normalised SFR (i.e., starburstiness,
$R_{rm MS}$) distribution changes continuously as a function of AGN power,
using a hierarchical Bayesian model that completely removes the need to bin. In
doing so, we find strong evidence that the $R_{rm MS}$ distribution changes
with AGN power, such that higher X-ray luminosity AGNs have a tighter physical
connection to the star forming process than lower luminosity AGNs.

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