Published October 6, 2020 | Version v1
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Basic Considerations for the Observability of Kinematically Offset Binary AGN

  • 1. Northwestern University

Description

KDE resampled massive black-hole (MBH) binary population used for the analysis in Kelley 2020, Considerations for the Observability of Kinematically Offset Binary AGN (2005.10255).

We start with a population of MBH binaries derived from the Illustris cosmological simulations, and evolved using semi-analytic post-processing models.  These methods are described in Kelley et al. 2016 (1606.01900) and Kelley et al. 2017a,b (1702.02180 and 1711.00075).  We then use the kernel density estimation (KDE) technique to resample this population from the Illustris volume, into a sample of binaries from a full, simulated light-cone of observations.  The binaries are resampled in bins of observed orbital period.  The number of resampled binaries in a given period bin are restricted to 500,000.  When this occurs, the 'weight' of those binaries is assigned a value greater than one, while the 'weight' of binaries in unrestricted period bins is set to unity.  For example, if the 'true' number of binaries in a bin should have been 1e6, the number of samples would be restricted to 5e5, and the weight of each of those binaries would be set to 2.0.  If the number of binaries in a bin were instead 2e5, which is less than the limit, then each of those binaries is given a weight of 1.0.  Only a single realization of this sample is included, but additional realizations can be produced if needed and on request.

The data are presented in hdf5 format and contain the following arrays:

# Meta-Data

`periods`:
    shape: (201,)
    units: seconds
    descr: the edges of the bins in observed orbital period from which the population was sampled.

`counts`:
    shape: (200,)
    units: None
    descr: The number of binaries produced in each period bin.  This number for each bin is capped at 500,000.  The sum of these values equals the total number of samples (70622013).


# Data
In this particular realization of data, the number of sampled binaries is `S = 70622013`.

`mtot`:
    shape: (S,)
    units: grams
    descr: the total mass of each binary (`M = M1 + M2`).

`mrat`:
    shape: (S,)
    units: None
    descr: The mass ratio of each binary, `q = M2/M1 <= 1.0`, where M2 is the mass of the secondary (lower mass) component.

`pobs`:
    shape: (S,)
    units: seconds
    descr: The orbital period of each binary in the observer's rest frame (at redshift, `z = 0`).

`redz`:
    shape: (S,)
    units: None
    descr: The redshift of each binary.

`weights`:
    shape: (S,)
    units: None
    descr: The number of 'true' binaries (i.e. the number that are expected to occur in this realization of an observed universe) represented by this individual 'sample', and having similar binary parameters.

 

Notes

The KDE resampling was performed using the `kalepy` python package, available on github at https://github.com/lzkelley/kalepy, and installable with `pip install kalepy`.

Files

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Additional details

Related works

Is supplement to
Preprint: arXiv:2005.10255 (arXiv)