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Leiden AGN club

From October 2017 to October 2019, we organised a dedicated meeting of researchers studying AGNs at the Sterrewacht Leiden. The meeting usually took place Tuesday, 1 pm in room 1104 (Huygens Lab 11th floor). We are a diverse group of radio, optical and high-energy astronomers (MSc students, PhD candidates, postdocs, staff) and occasionally even theorists come by.

Since 2020, AGN-related talks are now usually part of either the Galaxy Coffee, Lunch Talks or general Colloquium series.

Previous talks in the AGN club

  • Tue, 29 October 2019 – Matteo Guianazzi (ESTEC)
    Title: Radiation Pressure Compression: the Rosetta Stone of AGN Narrow Line Regions and AGN outflows?Observations at various wavelengths unveil a copious amount of ionizing gas embedding accreting super-massive black holes in Active Galactic Nuclei (AGN), on spatial scales ranging from a few hundreds gravitational radii to hundreds of kiloparsecs. When/if outflowing with sub-relativistic velocities, and if efficiently coupled to the Interstellar Medium, this plasma can constitute the agent of the “AGN feed-back”, postulated to drive the concurrent cosmological evolution of the AGN and of their host galaxies. Understanding the mechanism responsible for the physical state of the ionized gas is therefore crucial for any physically-motivated AGN structure model. In this talk, I propose Radiation Pressure Compression (RPC) as the universal interpretative scenario for the gas in the AGN Extended Narrow Line Regions (NLRs) on sub-kpc scales. RPC naturally leads to density radial gradients, consistent to those observed in NLR multi-wavelength observations. It also leads to a well-defined ionisation distributions, in striking agreement with those measured via high-resolution X-ray spectroscopy of obscured AGN. At the same time, RPC provides a natural explanation for the broad ionisation structure observed in AGN outflows. In contrast with a constant gas pressure multi-phase medium, RPC further predicts an increasing gas pressure with decreasing ionisation, which can be tested with future X-ray missions using density diagnostics.
  • Fri, 6 September 2019 – special lunch talk (12:50, HL414) – Daniel Asmus (University of Southampton): “From the mid-infrared structure of AGN to a complete census of black hole growth in the local Universe”
    In this talk, I will briefly review our current understanding of the mid-infrared (MIR) structure of active galactic nuclei (AGN) with particular focus on the recent results from ground-based high angular resolution observations of nearby AGN. These surprisingly revealed prominent polar dusty structures on scales of a few to hundreds of parsecs. I will present new observations that imply that this polar dust is dominating the MIR and might be ubiquitous in AGN as a result of a radiation-driven wind. This could have far reaching consequences for the AGN unification scheme. At the same time, it explains the high level of isotropy observed in the MIR, which in turn opens up exciting possibilities to select AGN in an unbiased way. I will show how, very soon, the combination of MIR and X-ray selections will allow us to build a complete census of black hole growth in the nearby Universe. Specifically, we will be able to measure the true obscuration distribution of AGN for the first time and address many of the other big questions like the AGN–galaxy connection through feeding and feedback processes. As a side result, we will also obtain the most complete local galaxy sample thanks to the new machine-learning based image recognition algorithms.
  • Tue, 6 August 2019 – discussion of the paper A two-stage outflow in NGC 1068 (by Daniel May and João Steiner)
  • Tue, 16 July 2019 – AGN group meeting: round-the-table short presentations / updates by Michael Rosenthal, Thomas Dodds, Christian Groeneveld, Violeta Gámez Rosas, Turgay Çaǧlar
  • Mon, 8 July 2019 – AGNs in the Netherlands meeting, Dwingeloo
  • Wed, 12 June 2019 (note special time and place: 10 am, Oort room) – Vardha N. Bennert: Measuring Black Hole Masses and Calibrating Black Hole Mass Scaling Relations for Active Galaxies
    Reverberation mapping (RM) provides reliable black hole masses (MBH) for broad-line active galactic nuclei (AGN). The resulting relationship between the broad-line region radius and the AGN luminosity is the foundation of virtually all MBH measurements beyond the local universe. However, its tightness and universality has recently been questioned, especially the extrapolation from Seyfert-type AGNs typical of most RM campaigns to quasars across all cosmic times. I will discuss challenges of RM, new approaches and recent results.
  • Tue, 14 May 2019 – Thomas Dodds: Changing-look AGN
  • Tue, 2 April 2019 – Gülay Gürkan: Low-frequency radio properties of optically selected quasars and beyond
  • Tue, 5 March 2019 – Wendy Williams: The lives and times of low frequency radio AGN
  • Wed, 13 February 2019 – Violeta Gámez Rosas: Presentation of her Ph.D. project (VLTI/MATISSE observations of nearby AGNs)
  • Wed, 5 Dec 2018 – Nika Jurlin (Groningen): Dying and restarting phases of the life-cycle of
    radio galaxies
  • Wed, 21 Nov 2018 – Yannick Bahé: The EAGLE AGN model: successes, failures, and insights
  • Wed, 31 October 2018 – Davide Lena (SRON Utrecht / Nijmegen): A new dual AGN candidate
  • Tue, 16 October 2018 – Peter Barthel (Groningen): Gas outflows in quasar hosts
  • Tue, 9 October 2018 – Darshan Kakkad (ESO, Chile): Fantastic AGN outflows and where to find them: The SUPER survey
  • Tue, 18 September 2018 – Discussion session “Torus observations” (e.g. based on Chapter 3 of Netzer et al. 2015 (ARAA)) – led by Violeta Gámez-Rosas
  • 19 June 2018 – Violeta Gámez: On the history of AGN research
  • 5 June 2018 – Kim Emig: “Interpreting the first detection of radio recombination lines at cosmological distances”
  • 22 May 2018 – latest results from Tiago’s work and paper discussion (led by Tiago): “Evidence that 50% of BALQSO Outflows Are Situated at Least 100 pc from the Central Source” (Nahum Arav, Guilin Liu, Xinfeng Xu, James Stidham, Chris Benn, Carter Chamberlain)
  • 24 April 2018 – paper discussion: “Direct evidence of AGN-feedback: a post starburst galaxy stripped of its gas by AGN-driven wind” (Dalya Baron, Hagai Netzer, J. Xavier Prochaska, Zheng Cai, Sebastiano Cantalupo, D. Christopher Martin, Mateusz Matuszewski, Anna M. Moore, Patrick Morrissey, James D. Neill)
  • 6 Mar 2018 – Aayush Saxena: high-redshift radio galaxies & paper club
  • 6 Feb 2018 – brief presentation of a Python GUI to help identify a potential minor merger origin of local powerful AGNs; then: Journal club – we discussed the recent Nature astronomy article by Gobat et al.: “The unexpectedly large dust and gas content of quiescent galaxies at z>1.4
  • 23 Jan 2018 – Journal club – we discussed a recent Nature letter by Martín-Navarro et al.: “Black-hole-regulated star formation in massive galaxies
  • 13 Dec 2017 – Turgay Çaǧlar – AGN triggering in the cluster environment
    We also discussed about a recent paper on Hanny’s Voorwerp.
  • 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

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