Postdoctoral Researcher (M/F) – Multi-scale, High Angular Resolution Analysis of Active Galactic Nuclei

Job Description

Missions

Active Galactic Nuclei (AGN) play a key role in galaxy evolution through AGN feedback on their host galaxies. They are tracers of the co-evolution of supermassive black holes (SMBHs) and galaxies. They also provide direct geometric distance measurements that could contribute to the ongoing debate on the Hubble tension.
Spectro-astrometry with GRAVITY and, soon, ASGARD on the VLTI makes it possible to spatially resolve the Broad-Line Region (BLR) of Type 1 AGN on sub-parsec scales, and provides dynamical measurements of SMBH masses through model fitting. Combined with linear size measurements obtained through reverberation mapping (RM), angular measurements from spectro-astrometry provide a direct geometric distance measurement, sometimes referred to as the “BLR parallax”.
MATISSE on the VLTI and LBTI provide images of the dusty torus and dusty winds of AGN on scales ranging from 1 to 10 pc. Reliable estimates of AGN distances and supermassive black hole masses, as well as a better understanding of AGN feedback on their host galaxies, require improved models and observations of AGN across all these scales, over a broad range of spectral bands and spectral resolutions.
The observational data obtained with each of these instrumental techniques are affected by structures that can only be accurately characterized at different spatial scales using the other instruments. Our overarching scientific goal is to study the mutual interactions between, and observational constraints on, the BLR, the dusty torus and dusty wind, inflows and outflows, and the circumnuclear disk (CND), as observed through differential interferometry in emission lines and continuum interferometry in the K, L, M, and N bands, together with larger-scale imaging of the CND, inflows, outflows, and shocks.
This will improve our understanding of AGN feedback, the accuracy of SMBH mass measurements, and consequently our constraints on SMBH–galaxy co-evolution. Ultimately, this should make BLR parallax measurements accurate enough to have an impact on the Hubble tension problem.
The instrumental context is particularly unique, with the breakthrough in VLTI sensitivity provided by GRAVITY+, and hence the increasing number of AGN that can be observed with optical interferometry, together with the first year of operations of BIFROST/ASGARD.

Activity

The first task will be to combine existing image-reconstruction codes for interferometry with deconvolution codes developed for single-aperture adaptive optics, within a global image reconstruction or model-fitting framework covering all these spatial scales. Several options are possible, but the preferred approach, building on previous work, would be to use machine learning on a simulated database to develop the tool, and then apply it to real data from GRAVITY/VLTI (K band), MATISSE/VLTI (L, M, N bands), LBTI, and SPHERE/VLT or ERIS/VLT. This approach has already proven successful, both for VLTI observations and for single-aperture observations, when treated separately.
At a different spatial scale, multi-scale tools will then be used to combine differential interferometric observations of BLR emission lines with continuum images and dust models. Applying these image-reconstruction and model-fitting tools to real data provided by GRAVITY, MATISSE, and BIFROST will enable a better understanding of gas–dust and dust–wind interactions in the CND, the use of resolved dust structures to constrain the geometry of the BLR, and ultimately improved BLR modelling for joint measurements of SMBH masses and distances using both differential interferometry and reverberation mapping.
Finally, since image reconstruction and model fitting rely on accurate models of the observational noise, a small fraction of the time could be devoted to validating and updating the GRAVITY and MATISSE noise models.

Your Profil

Skills

- Active Galactic Nuclei (AGN)
- Long-baseline optical interferometry and data processing
- Model fitting and/or image reconstruction in astrophysics
- Machine learning
Photoionization codes (preferably Cloudy)
Most of the codes are written in Python. The position involves collaboration with international teams across several institutes, with a core team based in Nice. Proficiency in English is essential.

Your Work Environment

The Joseph-Louis Lagrange Laboratory (https://lagrange.oca.eu/fr/accueil-lagrange) is a joint research unit of Université Côte d'Azur, the Côte d'Azur Observatory (OCA), and the CNRS (French National Centre for Scientific Research). It brings together research teams working on Galaxies and Cosmology (G&C), Physical Methods for Observation (MPO), Stellar and Solar Physics, Signal and Imaging (Signal), Theory and Observation in Planetology (TOP), and Turbulence, Fluids and Plasma.

The laboratory is the birthplace of multi-telescope optical interferometry and remains a world leader in the field, with leadership of the VLTI AMBER and MATISSE instrument consortia, major contributions to GRAVITY+, and a leading role in the ASGARD visitor instrument suite.
The postdoctoral researcher will join the MPO instrumental research team, working closely with international scientific groups on AGN within the MATISSE and GRAVITY+ collaborations, as well as with the G&C team.

Constraints and risks

Possible observing missions in Chile

Compensation and benefits

Compensation

Between €3,075 and €3,500 gross per month, depending on experience.

Annual leave and RTT

44 jours

Remote Working practice and compensation

Pratique et indemnisation du TT

Transport

Prise en charge à 75% du coût et forfait mobilité durable jusqu’à 300€

About the offer

About the CNRS

The CNRS is a major player in fundamental research on a global scale. The CNRS is the only French organization active in all scientific fields. Its unique position as a multi-specialist allows it to bring together different disciplines to address the most important challenges of the contemporary world, in connection with the actors of change.

CNRS

The research professions