Nina Mackensen  (Germany)

n.mackensen @ stud.uni-heidelberg.de

Quasar kinematics and accretion processes during cosmic noon

When we observe galaxies today, we generally assume that a supermassive black hole resides at their centers. Some of these galaxies host active black holes that are still accreting large amounts of matter and emitting enormous quantities of radiation; these systems are known as active galactic nuclei (AGNs). By studying them across different cosmic epochs, we can gain a clearer understanding of how the evolution of supermassive black holes is connected to that of their host galaxies.

My work focuses on six quasars observed at redshifts z ≈ 2–3, probing the epoch of ‘cosmic noon.’ I primarily analyze near-infrared spectra obtained with the LUCI spectrograph at the Large Binocular Telescope, complemented by archival ultraviolet spectra. This approach allows us to study rest-frame optical emission lines such as Hα and Hβ, as well as the ultraviolet C IV emission line.
These lines are thought to originate from different regions within the broad-line region (BLR) and are therefore influenced by different physical processes. The Balmer lines (Hα and Hβ) are generally associated with virialized gas motions dominated by the gravitational potential of the black hole, whereas the C IV line is likely more strongly affected by winds and non-virial motions. By analyzing their complex structure, we can therefore draw conclusions about the geometry of the BLR as well as related inflows and outflows.

By modeling the emission line profiles and measuring their widths and luminosities, black hole masses can be estimated using established virial methods. In addition, accretion rates can be derived from continuum luminosities and Eddington ratios. In this way, the project aims to provide a more comprehensive view of quasar kinematics and accretion processes during cosmic noon.

Supervisor:    Jochen Heidt  (LSW)