Home » Research » Leiden AGN club

Leiden AGN club

Every second Wednesday, 2pm, Gabriela Calistro Rivera and I organise an AGN club at the Sterrewacht Leiden (room 422). We are a diverse group of radio, optical and high-energy astronomers (MSc students, PhD candidates, postdocs, staff). Feel free to join us anytime and let Gaby or me know if you’d like to contribute a talk!

Upcoming meetings

  • Wed, 13 Dec 2017 – Turgay Çaǧlar – AGN triggering in the cluster environment

Previous talks in the AGN club

  • 29 Nov 2017 – Tiago Costa – Quasar outflows driven by trapped infrared radiation
    Abstract for Tiago’s talk: “I will present a new suite of cosmological radiation-hydrodynamic simulations targeting the evolution of a massive galaxy at z > 6. These simulations follow a range of important physical processes, such as radiative cooling and star formation, but crucially also the radiation field generated by a bright quasar, self-consistently. I will show that quasar radiation pressure is able to launch large-scale outflows, particularly when the galactic gas reservoir is optically thick to reprocessed IR radiation. In addition, I will show how a thermal instability in outflowing material naturally leads to multi-phase structure, potentially explaining observations of multi-phase outflows. Finally, I will discuss the impact IR radiation pressure on star formation and will argue that quenching proceeds not only through gas ejection but also due to internal pressurisation of gas by trapped radiation, within massive galaxies, i.e. it may be possible to quench galaxies without necessarily removing their gas.”
  • 15 Nov 2017 – Andres Ramos Padilla – AGN contribution in the evolution of merger galaxies
    Utilizing the SED modeling and fitting tool CIGALE, we derive the physical conditions of the ISM in local starbursts, merger galaxies and AGNs. We investigate how the star formation rates (SFRs), the fractional contribution from the AGN to the infrared bolometric emission ($f_{\rm{AGN}}$), and stellar mass depend on galaxy type and merger stage. Using mid-infrared fine-structure lines, we solve the degeneracy in bolometric contribution between AGN and star formation
    galaxies. Our estimated stellar masses and SFRs also allow us to evaluate where these galaxies fall within the so-called main sequence of star-formating galaxies and link the SED properties to the measured sSFR. We find that mergers occupy a region between bright starbursts and pure AGNs in the $f_{\rm{AGN}}$-[NeV]/[NeII] plane, and quantify the increase in $f_{\rm{AGN}}$ as mergers progress towards late types.
  • 1 Nov 2017 – Margherita Gustini (SRON, Utrecht) – A Global View of the Inner Accretion/Ejection Flow around Super Massive Black Holes
    Understanding the physics of accretion and ejection around super massive black holes (SMBHs) is crucial to understand the evolution of active galactic nuclei (AGN) and therefore of the large scale structures of the Universe. I propose to extend the geometrical unification model for AGN by including different accretion/ejection modes, with special emphasis on the role of radiation in driving powerful accretion disk winds from the inner regions (sub-parsec scales) around SMBHs, as probed by UV and X-ray observations. The vast amount of electromagnetic radiation emitted by mass accretion is a distinctive characteristic of AGN: I will show how radiation can also fundamentally influence the presence of AGN ejection flows. In particular, the development of a strong UV line-driven accretion disk wind is unavoidable whenever mass accretion proceeds through a thin disk, for large black hole masses and Eddington ratios. The photon outflows and the mass accretion/ejection flows around SMBHs are coupled, and radiation driven accretion disk winds are a fundamental ingredient of AGN.
  • 17 Oct 2017 – Journal club

My Tweets