VLBI

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.

AGN et jetsVLBI

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.

Articles clésAGN et jetsFormation des galaxiesVLBIAvec mes étudiants

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.

AGN et jetsVLBI

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.

AGN et jetsFormation des galaxiesVLBIAvec mes étudiants

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 $D_A = 72^{+5}_{-6}$ Mpc, consistent with other measurements at that redshift.

AGN et jetsVLBI