Accretion disks, quasars and cosmology: meandering towards understanding

0570195 - ASÚ 2024 RIV NL eng J - Journal Article
Czerny, B. - Cao, S. - Jaiswal, V. K. - Karas, Vladimír - Khadka, N. - Martinez-Aldama, M.L. - Naddaf, M.-H. - Panda, S. - Nunez, F. P. - Prince, R. - Ratra, B. - Sniegowska, M. - Yu, Z. - Zajaček, M.
Accretion disks, quasars and cosmology: meandering towards understanding.
Astrophysics and Space Science. Roč. 368, č. 2 (2023), č. článku 8. ISSN 0004-640X. E-ISSN 1572-946X
R&D Projects: GA ČR(CZ) GX21-06825X
Institutional support: RVO:67985815
Keywords : black holes * galaxies * accretion disks
OECD category: Astronomy (including astrophysics,space science)
Impact factor: 1.9, year: 2022
Method of publishing: Open access

As Setti and Woltjer noted back in 1973, one can use quasars to construct the Hubble diagram, however, the actual application of the idea was not that straightforward. It took years to implement the proposition successfully. Most ways to employ quasars for cosmology now require an advanced understanding of their structure, step by step. We briefly review this progress, with unavoidable personal biases, and concentrate on bright unobscured sources. We will mention the problem of the gas flow character close to the innermost stable circular orbit near the black hole, as discussed five decades ago. This problem later led to the development of the slim disk scenario and is recently revived in the context of Magnetically Arrested Disks (MAD) and Standard and Normal Evolution (SANE) models. We also discuss the hot or warm corona issue, which is still under debate and complicates the analysis of X-ray reflection. We present the scenario of the formation of the low ionization part of the Broad Line Region as a failed wind powered by radiation pressure acting on dust (Failed Radiatively Driven Dusty Outflow FRADO). Next, we examine the cosmological constraints currently achievable with quasars, primarily concentrating on light echo methods (continuum time delays and spectral-line time delays to the continuum) that are (or should be) incorporating the progress mentioned above. Finally, we briefly discuss prospects in this lively subject area.
Permanent Link: https://hdl.handle.net/11104/0341973