Ilya S. Khrykin
astrophysicist, Ph.D

I am Ilya Khrykin, currently a Postdoctoral Researcher at Kavli Institute for Physic and Mathematics of the Universe (Kavli IPMU, Japan) in the group of Khee-Gan Lee. My research is mainly focused on understanding the evolution of quasars and growth of the supermassive black holes, analysis of the fast-radio-bursts (FRB), and unraveling the physical mechanisms responsible for evolution of the intergalactic medium.

I was born in Rostov-on-Don, USSR (now Russia) and got my Bachelor and Master's degrees in Physics from the Southern Federal University (Rostov-on-Don, Russia). I did my PhD at the Max Planck Institute for Astronomy (Heidelberg, Germany) with Joe Hennawi (UC Santa Barabra). Before moving to Japan, I was a short term researcher at the Research Institute for Physics (Southern Federal University, Rostov-on-Don, Russia).

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Curriculum vitae

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My current research

• Quasar proximity zones: inferring properties of the SMBH and IGM

Analogous to how O-stars transform their nearby interstellar medium, the enhanced radiation field in the so-called proximity zones of luminous quasars, dramatically alters the ionization state of the surrounding intergalactic medium (IGM), resulting in enhanced Lyα transmission near the quasar itself. By studing the quasar proximity zones we can infer several important properties of both quasars and the IGM.

One of the key quantities necessary to distinguish between various models of formation and growth of the supermassive black holes, the evolution of quasars, and the feedback effects on the surrounding gas is the duration of individual accretion episodes, i.e., the quasar lifetime. By measuring the extent of observed quasar He II proximity zones at z~3-4 (analogous to HI Lya proximity zones at z~6, but sensetive to the lifetime timescales 3 orders of magnitude longer) and comparing them to the results of the hydrodynamical and radiative transfer simulations, we are able to measure the quasar lifetime to the unprecedented accuracy.

Recently, we have developed a fully Bayesian algorithm to infer lifetimes of individual quasars, and sucsessfully applied it to all existing He II Lya transparent quasars. Our analyses has revealed a surprisingly broad distribution of individual lifetimes, both very young (<1 Myr) and old (>30Myr). Please check out these cool results presented in Khrykin et al. (2019) and Worseck, Khrykin et al. (2021)

In addition, quasars not only ionize gas in their proximity zones, but also dramatically increase the temperature of the surrounding IGM. In Khrykin et al. (2017) we showed that his effect, also known as thermal proximity effect can be measured in spectra of z~3-5 quasars and can yield the measurement of HeII fraction to ~0.04 absolute precision. This opens up the possibility to directly constrain the extent and timing of the He II reionization!

• Fast Radio Bursts: search for the missing baryons

Fast Radio Bursts (FRBs) are transient radio sources of an extragalactic origin. While the radio signal from FRBs is traveling towards Earth through the intergalactic medium (it also intersects the circumgalactic media of the galaxies along the line-of-sight), it experiences dispersion by free electrons along the line-of-sight. This dispersion is quantified by the so-called Dispersion Measure (DM) - one of the main properties of the FRBs. It is also possible to distinguish the contributions of different traversed regions into the measured DM. The largest contribution is expected from the underling large-scale gas in the IGM, parametrized by the fraction of baryons that reside in it. The holy grail will be the measurement of this baryon fraction as it might shed light on the old standing cosmological problem of the missing baryons. However, the cosmic variance introduces significant uncertanty into any estimates of the IGM contrubution. Ideally, one would need to map the large-scale density field that is traversed by the FRB signal in order to significantly reduce the uncertainty.

We are working on combining the observational efforts (FLIMFLAM survey, PI: K.G. Lee) and the Bayesian density reconstruction algorithm ARGO (Ata et al. (2015)) to estimate the underlying density field along the line-of-sight of observed localazed FRBs. Coupled with Bayseian statistical methods (e.g. MCMC) this will allow us to measure the fraction of baryons that reside in the IGM to unprecidented ~5-10% accuracy. Stay tuned!

• Temperature-Density relation in the IGM at z~2.5

Coming soon..

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Publications

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Public Outreach

I have presented public lectures about astrophysics, supermassive black holes and cosmology on several Science Festivals across Russia (2017-2019). I have also organized monthly public outreach event in Rostov-on-Don called "Science Burger" (a version of Astronomy on Tap), where young scientists could present there research to public in a lively and friendly environment.

From Spring 2021, I am co-host of a weekly podcast on Clubhouse social media platform, dedicated to explaining astronomical and astrophysical discoveres to the general public.

I strongly believe that communication with public is one of the key responsibilities of scientists, therefore, I frequently participate in public outreach events live, online and on the radio.

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Contact Details

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