The first (since a long time at least) meeting of AGN researchers in the Netherlands took place on Monday, 8 July 2019, at Astron, Dwingeloo and was followed by a dinner at the Bospub, Dwingeloo and we report about it here. The programme of the meeting can be found below.
Actions are marked in bold.
The meeting was considered a success by the participants and it was agreed to repeat such a meeting soon (in 2019) to follow-up on some of the discussions and to identify concrete projects to collaborate on.
The agenda was pretty full with presentations. Being the first meeting of the group, we considered important to give to as many as possible people the possibility of presenting their work. In future meetings we will limit the agenda to fewer talks and ask “senior” staff to present an overview of a topic considered relevant by the AGN group and a few junior people to present their specific work. For this we will prepare a list of key topics of relevance for multiple groups (possibly, but not necessarily, covering multiple wavelengths).
Given that not everything could be covered during the meeting, we decided to make sure this group should also stimulate students/PostDoc to visit all institutes to present their work. This will ensure communication and information also in-between the group meetings. For this we are defining reference people to organise this at each institute.
It would be good to have a more complete mailing list available on the web for communication. We need to check who is happy to be included (in addition to the one already included). It would also be good to see whether we can include any theorists / modellers. We need to identify missing people on the list and approach them on whether they are happy to be included. A new names from JIVE have been already added. A mailing list (firstname.lastname@example.org) has already been created. If you would like to be part of it, please let Violeta Gamez-Rosas know.
- 11.00 – 12.00
- Leo Burtscher (Leiden): Introduction (15+5 min)
The AGN landscape in the Netherlands and what can we learn from each other?
- Round-the-table introduction (5 min)
- Raffaella Morganti (Astron/Groningen): Impact of radio jets: the ALMA view (15+5 min)
- Violeta Gámez Rosas (Leiden): AGNs with MATISSE (15+5 min)
Interferometry in the mid infrared benefits from several advantages for the study of the cores of AGNs, namely optimum access to the innermost dusty regions that lie very close to the central blackhole and a much higher resolution compared to single dish telescopes. Already with MIDI the old model of the dusty toroidal structure was challenged by unveiling substantial extended IR emission in the most unexpected directions. MATISSE, the latest instrumentation in this field, expands the reach of MIDI further into and beyond the mid-IR to the L and M bands, adds more spectroscopic potential and aims at fully exploiting multiple-baseline interferometry with the VLTI allowing, for the first time, image reconstruction. This talk describes MATISSE and the first results from the commissioning data.
- Leo Burtscher (Leiden): Introduction (15+5 min)
- 12.00 – 13.00: Lunch break
- 13.00 – 14.30:
- Turgay Çağlar (Leiden). The M-sigma relation of the most luminous, local AGNs (15+5 min)
- Davide Lena (SRON/Utrecht): Radio jets and equatorial outflows? (15+5 min)
Optical integral field spectroscopy has opened a new window on the inner kiloparsec of galaxies. Our observations of the ionised gas have shown the existence of a puzzling and unexpected kinematical feature: a region of enhanced velocity dispersion in a plane approximately perpendicular to radio jets and radio extensions, seemingly the plane of the AGN torus. The spatial extent of the “equatorial velocity-dispersion enhancements” (EVDE) is often sharply defined, and observed to extend over about 100 – 200 pc either side from the nucleus. Within this region, emission lines display complex profiles, suggesting the coexistence of multiple kinematical components. When feasible, detailed studies suggest the presence of ionised gas in rotation and/or outflow in a plane perpendicular to the axis of the radio jet. In this talk I will present an overview of our results and possible interpretations.
- Alexander Kutkin (Astron): Acceleration of AGN jets on parsec-to-kiloparsec scales (15+5 min)
We probe jets kinematics in 11 radio-loud AGN without relying on multi-epoch VLBI kinematics analysis. The method is based on measuring multi-frequency total flux density time delay and core shift in the jets. Our estimates of the apparent jet speed are consistent with the highest velocities seen by VLBI. We derive Doppler factors, Lorentz factors and viewing angles of the jets, as well as the corresponding de-projected distance from the jet base to the core. The results support evidence for acceleration of the jets with bulk motion Lorentz factor Γ∝R^0.5 on de-projected scales R of 0.5−500 parsecs.
- Luca Ricci (UNITO / University of Torino): Spectra and ages of radio galaxy 3C 449 (15+5 min)
3C 449 is a low redshift (z = 0.017), giant Fanaroff-Riley class I (FR-I) radio galaxy located in the Zwicky cluster 2231.2+3732. Its proximity and morphology make 3C 449 an ideal target to study the spatial evolution of the radio spectrum, from the inner jets out to the edge of the hundred-parsec scale lobes, and to investigate the interaction of the radio emitting plasma with the intergalactic medium of the host cluster. In this talk, I will give a short description of the radio properties of FR-I radio galaxies, from the lower radio frequencies probed by the Low-Frequency Array (LOFAR) to the higher radio frequencies probed by the VLA. I will then describe the method that I will use in my Master Thesis project to obtain the radio spectral index map of 3C 449 and derive its spectral age, similarly to the work performed by Heesen et al. (2018) on the giant radio galaxy 3C 31. Finally, I will discuss some open questions on the discrepancies between the dynamical ages and the spectral ages of radio galaxies and possible solutions to this issue.
- Discussion (10 min)
- 14.30 – 15.00: Coffee break
- 15.00 – 16.20
- Nika Jurlin (Groningen): The life cycle of radio galaxies (15+5 min)
- Aleksandar Shulevski (Amsterdam): Case studies of AGN plasma ageing in two different environments (15+5 min)
The cycling of AGN activity leaves different morphological imprints depending on the AGN duty cycle as well as on the environment of the host galaxy. I will showcase the LoTSS view of 3C 236, an active giant radio galaxy located in a group environment with plasma ageing evident in its lobes, and Abell 1318, a curious remnant hosted in a galaxy cluster, hinting at a complex activity history. Contrasting the remnant properties, I will discuss the context of these objects in the framework of what we can infer from observations and the contribution of low frequency data sets.
- Suma Murthy (Groningen): HI in radio AGNs: A study at high redshifts (15+5 min)
It is believed that active galactic nuclei (AGNs) affect the evolution of their host galaxies. HI-21cm absorption associated with the hosts of radio-loud AGNs is a powerful tool probe of the effect of radio AGNs on cold gas. Various associated HI absorption studies at low redshifts (z < 0.25) have found that the detection rate of HI is higher in compact (young or restarted) AGNs than the extended (old) ones. Further, the effect of radio AGNs on cold gas has been found to depend on the phase of AGN activity, with the impact being maximum when the AGN is young and powerful. However, we lack similar insights into the incidence of HI and the conditions of cold gas in different AGN classes as we go higher in redshifts. This is because most of the studies at higher redshifts have focused only on specific AGN classes (compact, flat-spectrum AGNs).We have searched for associated HI absorption in a sample of ultra steep spectrum radio galaxies at z > 2. I will present results from this search aiming to probe the redshift dependence of HI detection rate and other absorber properties.
- Zsolt Paragi (Jive): AGN projects in the SKA-VLBI use case report (15+5 min)
- 16.20 – 17.00: Discussion and wrap-up
- 18.00 – 20.00: dinner at Bospub
- 21.05: Train connection from Hoogeveen arriving at 22.41 (Utrecht), 23.06 (Nijmegen), 22.53 (Amsterdam), 23.13 (Leiden)
The talk format is 10 min (talk) + 5 min (discussion).