Quasars with Periodic Variability: Capabilities and Limitations of Bayesian Searches for Supermassive Black Hole Binaries in Time-Domain Surveys. (arXiv:2110.07465v3 [astro-ph.GA] UPDATED)
<a href="http://arxiv.org/find/astro-ph/1/au:+Witt_C/0/1/0/all/0/1">Caitlin A. Witt</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Charisi_M/0/1/0/all/0/1">Maria Charisi</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Taylor_S/0/1/0/all/0/1">Stephen R. Taylor</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Burke_Spolaor_S/0/1/0/all/0/1">Sarah Burke-Spolaor</a>
Supermassive black hole binaries (SMBHBs) are an inevitable consequence of
galaxy mergers. At subparsec separations, they are practically impossible to
resolve, and the most promising technique is to search for quasars with
periodic variability. However, searches for quasar periodicity in time-domain
data are challenging due to the stochastic variability of quasars. In this
paper, we used Bayesian methods to disentangle periodic SMBHB signals from
intrinsic damped random walk (DRW) variability in active galactic nuclei light
curves. We simulated a wide variety of realistic DRW and DRW+sine light curves.
Their observed properties are modeled after the Catalina Real-time Transient
Survey (CRTS) and expected properties of the upcoming Legacy Survey of Space
and Time (LSST) from the Vera C. Rubin Observatory. Through a careful analysis
of parameter estimation and Bayesian model selection, we investigated the range
of parameter space for which binary systems can be detected. We also examined
which DRW signals can mimic periodicity and be falsely classified as binary
candidates. We found that periodic signals are more easily detectable if the
period is short or the amplitude of the signal is large compared to the
contribution of the DRW noise. We saw similar detection rates both in the CRTS
and LSST-like simulations, while the false-detection rate depends on the
quality of the data and is minimal in LSST. Our idealized simulations provide
an excellent way to uncover the intrinsic limitations in quasar periodicity
searches and set the stage for future searches for SMBHBs.
Supermassive black hole binaries (SMBHBs) are an inevitable consequence of
galaxy mergers. At subparsec separations, they are practically impossible to
resolve, and the most promising technique is to search for quasars with
periodic variability. However, searches for quasar periodicity in time-domain
data are challenging due to the stochastic variability of quasars. In this
paper, we used Bayesian methods to disentangle periodic SMBHB signals from
intrinsic damped random walk (DRW) variability in active galactic nuclei light
curves. We simulated a wide variety of realistic DRW and DRW+sine light curves.
Their observed properties are modeled after the Catalina Real-time Transient
Survey (CRTS) and expected properties of the upcoming Legacy Survey of Space
and Time (LSST) from the Vera C. Rubin Observatory. Through a careful analysis
of parameter estimation and Bayesian model selection, we investigated the range
of parameter space for which binary systems can be detected. We also examined
which DRW signals can mimic periodicity and be falsely classified as binary
candidates. We found that periodic signals are more easily detectable if the
period is short or the amplitude of the signal is large compared to the
contribution of the DRW noise. We saw similar detection rates both in the CRTS
and LSST-like simulations, while the false-detection rate depends on the
quality of the data and is minimal in LSST. Our idealized simulations provide
an excellent way to uncover the intrinsic limitations in quasar periodicity
searches and set the stage for future searches for SMBHBs.
http://arxiv.org/icons/sfx.gif
