Formal Talk by Belinda Wilkes – Active Galactic Nuclei and Star Formation

Formal Talk by Belinda Wilkes – Active Galactic Nuclei and Star Formation

Hybrid meeting via Zoom and at the BPS

Active Galactic Nuclei and Star Formation.

Our current understanding of galaxy evolution across the Universe requires
significant feedback from powerful active galactic nuclei (AGN) to moderate star
formation and generate the galaxy populations we observe today. Along related
lines, co-evolution of the central super-massive black hole (SMBH) and its host
galaxy are suggested by strong correlations between its mass and properties of its
host galaxy such as stellar mass, velocity dispersion and luminosity. However, while
this evidence is suggestive, direct observations of AGN feedback are largely
confined to low luminosity, nearby galaxies, while little is known about the dominant,
most active population at z∼1–2. This is beginning to change with the advent of high-
resolution observations with JWST.

Radio jets are the most visible and powerful outflows observed from Active Galactic
Nuclei (AGN). They transport large amounts of energy through the host galaxy
providing the most visible, large-scale connection with the central AGN. Jet lengths
provide an approximate age for the AGN activity, and the ratio of core to extended
radio fluxes constrains the jet’s angle to our line of sight. In addition, while there are
several possibilities, the passage of a radio jet through its host galaxy’s interstellar
medium (ISM) is estimated to be the dominant source of AGN feedback across the
Universe. Theoretical work predicts that jet interaction with a dense ISM inflates
bipolar bubbles, bounded by an expanding blast wave which entrains and heats the
ISM, slowing star-formation and depleting the ISM gas. This phenomenon is
signposted by bipolar outflows visible via the emission lines they generate. Behind
the shock front, the resulting compression of the ISM can induce SF along the jet.
Simulations predict that jets enhance SF on timescales of ∼10 Myr. Once the jet
extends beyond the confines of the galaxy, triggering ends, SF fades, and the stars
evolve passively over ~100s Myr.

I will review recent results from multi-wavelength studies of AGN, including our own
studies of jet-ISM interactions at cosmic noon, where both star-formation and AGN
activity peak.

Dr. Belinda Wilkes is a Senior Astrophysicist at the Smithsonian Astrophysical Observatory (SAO) in Cambridge, Massachusetts, US, and former director of the Chandra X-ray Centre.

She is currently a Royal Society Wolfson Visiting Fellow at the School of Physics here in Bristol.

Location
Bristol Photographic Society