Formation des galaxies

5 articles

Comment les galaxies assemblent-elles leur masse ? Comment évoluent-elles au sein de la structure à grande échelle ?

J’ai utilisé des simulations cosmologiques hydrodynamiques multi-zoom pour quantifier la masse assemblée par fusions et par accrétion diffuse de gaz (L'Huillier, Combes & Semelin 2012).

Zoom sur un amas de galaxies dans une simulation hydrodynamique — Zoom sur un amas dans une simulation hydrodynamique, d’après L'Huillier, Combes & Semelin (2012), A&A.

À l’aide de la simulation Horizon Run 4 (Kim et al. 2015), j’ai quantifié le taux d’interaction des halos — fusions et passages rapprochés (L'Huillier, Park & Kim 2015) — et leurs alignements (L'Huillier, Park & Kim 2017) en fonction de leur environnement (masse et densité à grande échelle).

Dans une étude menée par David Fernández Gil et publiée dans Nature Astronomy, nous avons détecté un alignement faible mais significatif entre la région centrale des jets d’AGN, observée par interférométrie à très longue base, et la forme optique de leurs galaxies hôtes dans plusieurs relevés (Fernández Gil et al. 2025, Nat. Astron.).

How the jet–host angle is measured: VLBI jet position angle (a) against the minor axis of the optical host in DES, DESI LS, SDSS and SkyMapper (b–e).

Les jets des trous noirs « connaissent » leur galaxie

2025 · Nature Astronomy 9 (2025) 302

Detection of an orthogonal alignment between parsec-scale AGN jets and their host galaxies

Fernández Gil, D.†, Hodgson, J. A., L'Huillier, B., Asorey, J., Saulder, C., Finner, K., et al.

Comparing VLBI jet directions with optical host-galaxy shapes for about 6,000 AGN, we detect a weak but significant alignment between the parsec-scale jet and the minor axis of its host galaxy: a link between the black hole and its host across three orders of magnitude in scale.

DOI · arXiv:2411.09099

Articles clés AGN et jets Formation des galaxies VLBI Avec mes étudiants

How the jet–host angle is measured: VLBI jet position angle (a) against the minor axis of the optical host in DES, DESI LS, SDSS and SkyMapper (b–e). (Figure from the 2025 follow-up paper.)

2023 · prépublication arXiv

Exploring connections between the VLBI and optical morphology of AGNs and their host galaxies

Fernández Gil, D.†, Hodgson, J. A., L'Huillier, B.

Matching over 9,000 VLBI sources from the Astrogeo catalogue to their optical host galaxies and fitting the hosts' shapes, this first study finds no clear correlation between host morphology and jet direction.

arXiv:2305.06713

AGN et jets Formation des galaxies VLBI Avec mes étudiants

Evolution of the alignment between the spins of interacting haloes, by environment (columns) and mass (rows).

2017 · MNRAS 466 (2017) 4875

Ecology of dark matter haloes – II. Effects of interactions on the alignment of halo pairs

L'Huillier, B., Park, C., Kim, J.

In Horizon Run 4, interacting haloes have lower spin and are more spherical than typical haloes. Pairs start with antiparallel spins that gradually become parallel, interactions are mostly radial, and alignments are strongest for massive, close pairs and persist up to $z = 4$ .

DOI · arXiv:1701.04417

Formation des galaxies Halos de matière noire Simulations Premier auteur

Haloes in the cosmic web at z = 0 (top) and z = 1 (bottom): the densest environments (red) sit in the nodes, intermediate ones (cyan) in filaments. — Haloes in the cosmic web at $z = 0$ (top) and $z = 1$ (bottom): the densest environments (red) sit in the nodes, intermediate ones (cyan) in filaments.

2015 · MNRAS 451 (2015) 527

The ecology of dark matter haloes – I. The rates and types of halo interactions

L'Huillier, B., Park, C., Kim, J.

Using Horizon Run 4, we measure how often haloes interact as a function of environment, separation, mass ratio, mass and redshift. Most interactions happen at density contrast $\delta \approx 20$ , while the interacting fraction peaks at $\delta \approx 1000$ ; we provide a fitting formula and identify two interaction modes.

DOI · arXiv:1505.00788

Formation des galaxies Halos de matière noire Simulations Premier auteur

Fraction of stellar mass gained through smooth accretion rather than mergers, versus galaxy mass. The mean is 77%.

2012 · A&A 544 (2012) A68

Mass assembly of galaxies: smooth accretion versus mergers

L'Huillier, B., Combes, F., Semelin, B.

Multi-zoom cosmological simulations show that galaxies grow mostly by smooth accretion, which brings on average 77% of their mass, while mergers bring 23%. Only the most massive galaxies grow significantly through mergers.

DOI · arXiv:1108.4247

Articles clés Formation des galaxies Simulations Premier auteur