Welcome! I am a Postdoctoral Associate working at NASA Goddard Space Flight Center and University of Maryland College Park. I received my PhD from the Department of Physics at Stanford University, where I was a member of the X-ray Astronomy and Observational Cosmology group at the Kavli Institute for Particle Astrophysics and Cosmology .
In my research, I want to understand how supermassive black holes, which reside at centers of galaxies and galaxy clusters, affect the evolution of their hosts. In their accreting state, these active galactic nuclei (AGN) can prevent the stars from forming by releasing coupious radiation and powerful outflows (winds and jets of relativistic matter). However, we still do not understand how the AGN energy is transferred to the gas in the host galaxy or cluster.
The energetic X-ray radiation can provide key insights into this so-called AGN feedback, as it emerges from the immediate environment of the supermassive black hole and the hottest galactic gas. In my work, I use high resolution X-ray spectra from the excellent Chandra X-ray Observatory, XMM-Newton, and Hitomi satellites to understand the precise physical mechanisms of these AGN-galaxy interactions. I am also awaiting the upcoming launch of the JAXA/NASA X-ray Imaging and Spectroscopy Mission, which will open up a new window onto the X-ray Universe.
First measurements of hot gas velocities in massive elliptical galaxies
Massive, red and dead elliptical galaxies, no longer form stars. We think that this is because the central AGN heats and maintains the gas at high, X-ray emitting temperatures.
To understand this mode of AGN feedback, we first need to constrain transport processes in the intracluster/intragalactic gas. The key information missing is the velocity structure of this hot gas, which can, in principle, be recovered from the width of emission lines. However, the best current instrument to do this, XMM-Newton Reflection Grating Spectrometer (RGS), convolves the spatial and spectral infomation due to its large aperture (left figure: RGS spectrum of NGC 4636 and Chandra image of the galaxy with 0.8 arcmin-wide RGS apreture).
I have used a subtle radiative transfer effect called resonant scattering, which traces the turbulent gas motions, and combined it with the direct line broadening measurements. This allowed me and my colleagues to obtain, for the first time, measurements of hot gas velocities in a sample of 13 giant elliptical galaxies, dominated by the jet-driven maintence mode AGN feedback. Our results suggest that, similarly to galaxy cluster cores, the jet energy can be dissipated via turbulent cascade.
Read more: "Improved measurements of turbulence in the hot gaseous atmospheres of nearby giant elliptical galaxies", Ogorzalek A. et al., 2017, MNRAS, 472, 1659
First microcalorimeter detection of resonance scattering with Hitomi
In February 2016, a revolutionary X-ray microcalorimeter was launched on board of the Hitomi satellite. It provided an unprecedented spectral and spatial resolution, allowing us to precisely study hot gas motions in an AGN-dominated core of Perseus Cluster (pictured above). For the first time, we were able to extract high resolution spectra from multiple regions of an extended, X-ray emitting atmosphere.
Together with the Hitomi Collaboration, we studied the spatial variations of resonant scattering effect in the cluster core. Here, using the techniques I developed for massive elliptical galaxies, we showed that resonant scattering can provide a completely independent measurements of gas velocity field. As demonstrated by the Hitomi measurement, this effect will enable even more detailed studies of hot gas motions with the launch of new X-ray missions: XRISM, ATHENA, and Lynx.
Read more: "Measurements of resonant scattering in the Perseus Cluster core with Hitomi SXS", Hitomi Collaboration, incl. Ogorzalek, A., 2018, PASJ, 70, 10
A new Bayesian framework for characterizing X-ray detected AGN outflows
In the ejective AGN feedback mode, accretion driven winds are launched near the black hole. These may quench star formation by expelling the available gas, and help regulate the empirical relation between supermassive black hole masses and galactic bulge stellar velocity dispersions (i.e. M-sigma relation). The key limiting factor in understanding the impact of AGN outflows on galaxy evolution is the knowledge of their physical structure (i.e. ionization, velocity and density).
In order to precisely and robustly characterize the physical structure of such X-ray detected AGN winds, I developed an improved Bayesian framework and successfully applied it to some of the deepest Chandra High Energy Transmission Grating spectra ever observed.
You can read more on arxiv soon!
Apart from research, I enjoy teaching undergraduate and graduate students basics of optical observations and data reduction with the use of telescopes at the Stanford Student Observatory. There, you can often find me running public telescope observing and outreach sessions. My commitment to teaching
has been recognized by the Department of Physics at Stanford. I also volunteer for and help organize multiple mentorship programs for women in STEM.
SLAC Accelerating Girls' Engagement in STEM summer camp visiting Stanford Student Observatory (August 2018).
- Cecilia Payne-Gaposchkin Doctoral Dissertation Award in Astrophysics finalist talk, American Physical Society April Meeting, Washington, DC, USA: Probing the Physics of AGN Feedback with High Resolution X-ray Spectroscopy, Room Washington 2, 2:06 PM, April 18th 2020
- Black Hole Initiative Colloquium, Harvard University, USA: Uncovering the physics behind AGN feedback with high resolution X-ray spectroscopy, November 2019
- Doctoral thesis defense, Stanford University, USA: Probing the physics of AGN feedback with high resolution X-ray spectroscopy, July 2019
- Conference poster, 17th High Energy Astrophysics Division Meeting, Monterrey, USA: Constraining the power of X-ray winds: a Bayesian approach , March 2019
- Rodger Doxsey Prize Dissertation talk, AAS 233rd Winter Meeting, Seattle, USA: Probing the physics of AGN feedback with high resolution X-ray spectroscopy, January 2019
- Institute seminar, Institute of Astronomy, University of Cambridge, UK: Insights into AGN feedback from high resolution X-ray spectroscopy, September 2018
- Lunch talk, Leiden Observatory, Netherlands : Insights into AGN feedback from high resolution X-ray spectroscopy, September 2018
- Conference posters, 15th Potsdam Thinkshop. The role of feedback in galaxy formation - from small-scale winds to large-scale outflows, Potsdam, Germany: Understanding wind-mode feedback in the X-ray brightest AGN and Using hot gas velocity measurements to probe AGN feedback in massive galaxies, September 2018
- Conference talk, SnowCluster 2018: Physics of Galaxy Clusters, Snowbird, USA: Using new hot gas velocity measurements to probe feedback in massive galaxies, March 2018
- Colloquium talk, SRON Netherlands Institute for Space Research, Utrecht, Netherlands: Utilizing X-ray gas velocity measurements as a new probe of AGN feedback in giant elliptical galaxies, September 2017
- Conference talk, The power of X-ray spectroscopy, Warsaw, Poland: Probing hot gas velocity field in massive galaxies and galaxy clusters with resonant scattering in the era of high resolution X-ray spectroscopy, September 2017
- Conference talk, 16th High Energy Astrophysics Division Meeting, Sun Valley, USA: Utilizing X-ray gas velocity measurements as a new probe of AGN feedback in giant elliptical galaxies and Poster: Resonant scattering as a sensitive diagnostic of current collisional plasma models , August 2017
- Conference talk, The X-ray Universe, Rome, Italy: Using X-ray velocity measurements as a new probe of AGN feedback in massive galaxies, June 2017
- Conference poster, High Energy Density Laboratory Astrophysics, SLAC, USA: Resonant scattering measurements of turbulence in nearby elliptical galaxies, May 2016