은하의 형성과 진화 — 벤자민 루일리예

은하는 어떻게 질량을 모을까요? 은하는 우주 거대구조 속에서 어떻게 진화할까요?

다중 줌(multi-zoom) 우주론 유체역학 시뮬레이션을 이용해 병합과 매끄러운 가스 강착이 각각 은하 질량에 얼마나 기여하는지 정량화했습니다 (L'Huillier, Combes & Semelin 2012).

유체역학 시뮬레이션 속 은하단 확대 영상. L'Huillier, Combes & Semelin (2012), A&A.

Horizon Run 4 시뮬레이션(Kim et al. 2015)을 이용해 헤일로의 상호작용 빈도(병합과 근접 통과, L'Huillier, Park & Kim 2015)와 정렬(L'Huillier, Park & Kim 2017)을 환경(질량과 대규모 밀도)에 따라 정량화했습니다.

David Fernández Gil이 주도하고 Nature Astronomy에 발표한 연구에서, 초장기선 간섭계(VLBI)로 관측한 AGN 제트의 중심부와 여러 탐사에서 얻은 모은하의 광학적 모양 사이에 약하지만 유의한 정렬이 있음을 발견했습니다 (Fernández Gil et al. 2025, Nat. Astron.).

은하와 AGN 관련 논문

논문 요약은 영어로 제공됩니다.

The speed-gun counter-jet method: the approaching jet looks longer and faster than the counter-jet, which fixes the viewing angle and speed.

2026 · A&A 712 (2026) A240

A refined method for measuring cosmological distances using variability and proper motions in AGNs with VLBI-detected counter jets

Hodgson, J. A., Carr, A., Parkinson, D., Statti, M., Myeong, J., L'Huillier, B., Shafieloo, A., Liodakis, I., Oh, S.-H.

We extend the ‘speed-gun’ distance method using the proper motions of both the approaching jet and the counter-jet, which removes its dependence on the Doppler factor. For 3C 84 we obtain an angular-diameter distance of 71–79 Mpc depending on the assumed geometry; the spherical case agrees with SH0ES-calibrated supernovae.

DOI · arXiv:2608.02202

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).

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

Simulated speed-gun distance measurements (30 sources, 10 flares each) for four redshift distributions, with the recovered cosmology.

2023 · MNRAS 521 (2023) L44

Estimating the feasibility of ‘standard speed-gun’ distances

Hodgson, J. A., L'Huillier, B., Liodakis, I., Lee, S.-S., Shafieloo, A.

We extend the ‘standard speed-gun’ distance method by using the maximum intrinsic brightness temperature of a source instead of its Doppler factor. Forecasts show that recovering the cosmology depends mainly on how well this temperature is known and on the number of observed flares.

DOI · arXiv:2301.06252

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 · arXiv 프리프린트

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

43 GHz VLBI maps of 3C 84 (2015–2017). The arrow marks the flaring region used for the distance measurement.

2020 · MNRAS 495 (2020) L27

Using variability and VLBI to measure cosmological distances

Hodgson, J. A., L'Huillier, B., Liodakis, I., Lee, S.-S., Shafieloo, A.

We propose measuring AGN distances by comparing the physical size implied by variability with the angular size measured by VLBI. For 3C 84 we find $D_{A} = 7 2_{- 6}^{+ 5}$ Mpc, consistent with other measurements at that redshift.

DOI · arXiv:2003.10278

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

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