High-redshift active galactic nuclei and their environment
Doctoral thesis, 2020
The aim of this thesis is to study the environment of high-z quasars and radio galaxies through submillimetre and CO spectral line observations and to contribute to the effort of uncovering the underlying processes that shape the evolution of massive galaxies. The thesis focuses on three case studies of high-z AGN-companion galaxy systems at z=2-3. These were selected based on the AGN host galaxy appearing as gas-poor, while the companion galaxy being very gas-rich. However, sensitive observations with the Atacama Large Millimeter/submillimeter Array and the Karl G. Jansky Very Large Array, tracing CO line emission and dust continuum emission, revealed that a significant amount of molecular gas and dust emission is associated with the host galaxies of the AGNs. My results highlight the importance of sensitive and high-resolution observations and demonstrate that high-z AGN systems are more complex and diverse, than it is implied by theoretical studies.
galaxies: evolution -- galaxies: high-redshift -- galaxies: active -- galaxies: Starburst -- -- Submillimeter: galaxies
Chalmers, Space, Earth and Environment, Astronomy and Plasmaphysics, Extragalactic Astrophysics
On the frequency of star-forming galaxies in the vicinity of powerful AGNs: The case of SMM J04135+10277
Astronomy and Astrophysics,; Vol. 597(2017)
SMM J04135+10277: a distant QSO-starburst system caught by ALMA
Monthly Notices of the Royal Astronomical Society,; Vol. 493(2020)p. 3744-3756
Judit Fogasy, K. K. Knudsen, G. Drouart and B. Gullberg: ALMA detects molecular gas in the halo of the powerful radio galaxy TXS 0828+193
J. Fogasy, K. K. Knudsen and E. Varenius: VLA detects CO(1-0) emission in the z = 3.65 quasar SDSS
In order to understand how galaxies formed and evolved into different types, and to reveal the processes that shaped their evolution, we need to look back in time to find their progenitors. Active galactic nuclei (AGNs) at cosmological distances are the prefect targets for this, as these are bright sources, where the central SMBH is actively growing. Moreover, such distant, powerful AGNs are hosted by massive galaxies and likely trace over-dense environments or protoclusters.
The aim of this thesis is to study the environment of cosmologically distant quasars and radio galaxies, the possible progenitors of local massive galaxies. The thesis presents three case studies of AGN-companion galaxy systems found at 1.7-2.5 billion years after the Big Bang, and which were selected based on the AGN host galaxy appearing gas-poor, while the companion galaxy being very gas-rich.
Much our previous knowledge of the gas and dust in distant AGNs and their host galaxies has been derived from low-resolution observations making it difficult to disentangle the contribution from companion galaxies. In my thesis we have challenged previous results using higher quality data at mm and radio wavelengths.These observations revealed that a significant amount of molecular gas and dust emission is associated with the host galaxies of the AGNs. My results highlight the importance of sensitive and high-resolution observations and demonstrate that high-z AGN systems are more complex and diverse, than it is implied by theoretical studies.
Astronomy, Astrophysics and Cosmology
Doktorsavhandlingar vid Chalmers tekniska högskola. Ny serie: 4793
Chalmers University of Technology
Opponent: Dr. Alexandra Pope, Department of Astronomy, University of Massachusetts, USA