2021/10/11 by Adam Ingram, Guglielmo Mastroserio, Michiel van der Klis +9 · 8 citations
Physics and Astronomy · #Accretion (finance) #Active galactic nucleus #Astrophysical Phenomena and Observations #Astrophysics #Astrophysics and Cosmic Phenomena #Black hole (networking) #Cosmic ray #Galaxies: Formation, Evolution, Phenomena #Galaxy #Hubble's law #Line-of-sight #Luminosity #Luminosity distance #Optics #Photon #Physics #Redshift #astro-ph.CO #astro-ph.HE
paper · pdf · doi:10.1093/mnras/stab2950
published in Monthly Notices of the Royal Astronomical Society 509(1), 619-633 (Oxford University Press) · Accepted for publication in MNRAS
openalex publication_date 2021/10/11 · arxiv created 2021/10/29 · arxiv updated 2021/11/17 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
ABSTRACT We show that X-ray reverberation mapping can be used to measure the distance to type 1 active galactic nuclei (AGNs). This is because X-ray photons originally emitted from the ‘corona’ close to the black hole irradiate the accretion disc and are reemitted with a characteristic ‘reflection’ spectrum that includes a prominent ∼6.4 keV iron emission line. The shape of the reflection spectrum depends on the irradiating flux, and the light-crossing delay between continuum photons observed directly from the corona and the reflected photons constrain the size of the disc. Simultaneously modelling the X-ray spectrum and the time delays between photons of different energies therefore constrains the intrinsic reflected luminosity, and the distance follows from the observed reflected flux. Alternatively, the distance can be measured from the X-ray spectrum alone if the black hole mass is known. We develop a new model of our reltrans X-ray reverberation mapping package, called rtdist, that has distance as a model parameter. We simulate a synthetic observation that we fit with our new model, and find that this technique applied to a sample of ∼25 AGNs can be used to measure the Hubble constant with a 3σ statistical uncertainty of ∼ 6 \rm km \rm s-1 \rm Mpc-1. Since the technique is completely independent of the traditional distance ladder and the cosmic microwave background radiation, it has the potential to address the current tension between them. We discuss sources of modelling uncertainty, and how they can be addressed in the near future.