Research
Mitigating the optical depth degeneracy using the kinematic Sunyaev-Zel’dovich effect with CMB-S4
The Epoch of Reionization (EoR) is one of the major phase transitions in the universe, and is the focus of several upcoming CMB experiments that will dramatically improve constraints on the cosmological parameters due to the improved sensitivities to small scale fluctuations. In this work, we explore the early time kinetic Sunyaev Zel’dovich (kSZ) effect as a probe of the EoR and we parametrize the reionization epoch with three main parameters including the mass of ionizing sources, the mean free path of photons and the ionization efficiency. We discuss the dependence of the kSZ power spectrum on the reionization model parameters, as well as on empirical parameters of reionization, namely the Thomson scattering optical depth to the CMB, tau, and the duration of reionization, delta z. We use both the two point function and the reconstructed four point function to break existing degeneracy between tau and As, the primordial amplitude of scalar fluctuations leading to forecast constraints on tau σ(τ) = 0.003 and σ(∆z) = 0.14.
Probing the Epoch of Reionization with the Simons Observatory
Reionization was a very critical process in the Universe in the transition from an opaque to a transparent Universe. However, we do not fully understand how this event happened. Using the kinetic Sunyaev-Zel’dovich Effect (kSZ), we can look critically into the reionization epoch of the Universe. This work aims to predict how well we can constrain the reionization of the Universe using forecasted data from the Simons Observatory (SO), to explain the transition from dark matter to stars. We use the model developed by ? to test whether we can determine the shape of the kSZ spectrum from patchy reionization. We estimate that the shape of the kSZ signal can be determined at multipoles between l = 1500 and l = 3000 and we conclude that models with smaller bubbles have more power at l ∼ 2000 while models with larger bubbles have similar shape.
STUDYING KINEMATICS OF NEARBY GALAXIES WITH WIFIS
Astronomical spectra are contaminated with telluric features, absorption features which originate from earth’s atmosphere. For proper analysis of these spectra, it is important to correct for these telluric features. I worked on developing the telluric correction software for removing telluric absorption from the Wide Integral Field Infrared Spectrograph (WIFIS) M85 data, following a similar process as outlined in Vacca et al. (2003). After having removed these features, we demonstrate the ability to measure kinematics and stellar abundances of galaxies observed with WIFIS as done in Cappellari et al. (2011).
DYNAMICAL EVOLUTION OF SUPERMASSIVE BINARY BLACK HOLES IN GALACTIC NUCLEI
The observed M − σ relation of central black hole mass and velocity dis persion of the host galaxy points to a co-evolution of galaxies and super mas sive black holes (SMBHs). In the standard cosmology, galaxies are growing by merger events and secular accretion of baryons. The fast coalescence of two SMBHs following the merger of two galaxies (before the next galaxy merger takes place) was a long standing problem. The bottleneck was the hard-binary phase preceding the phase of energy loss by gravitational wave emission. This so-called final-parsec problem was solved by N-body simulations of realistic ini tial conditions. Due to the triaxiality of the galaxy merger remnant, there is a large basin of stars coming close to the binary black hole. One of these simula tions, which require a couple of months computation time on a high performance computer using parallel GPU calculations, nicely show the evolution from the galaxy merger to the final coalescence by gravitational wave emission. In this work, we analyse in detail the origin and properties of those stars interacting with the BBH extracting energy and quantify the structure in terms of the radial profile and triaxiality.