Shadow of quadrupole-deformed compact objects in a local dark-matter shell

verfasst von: Shokoufe Faraji, João Luís Rosa
Abstract: This work investigated observational properties, namely the shadow and photon ring structure, of emission profiles originating near compact objects. In particular, we considered a distorted and deformed compact object characterized by two quadrupole parameters and surrounded by an optically thin and geometrically thin accretion disk with different emission profiles modeled by Johnson's standard-unbound (SU) distribution in the reference frame of the emitter. Under these assumptions, we produced the observed intensity profiles and shadow images for a face-on observer. Our results indicate that, due to the fact that modifications of the quadrupole parameters affect the radius of the innermost stable circular orbit (ISCO) and the unstable photon orbits on the equatorial plane, the observed shadow images and their properties are significantly influenced by the quadrupole parameters and emission profiles. Furthermore, we analyzed the impact of the presence of a dark-matter halo in the observational imprints considered and verified that both the increase in the matter contained in the halo or the decrease in the length-scale of the halo led to an increase in the size of the observed shadow. Our results indicate potential degeneracies between the observational features of distorted and deformed compact objects with those of spherically symmetric black holes, which could be assessed by a comparison with the current and future generation of optical experiments in gravitational physics.
Externe Organisation(en): Universität Bremen
University of Waterloo
Perimeter Institute for Theoretical Physics
University of Gdansk
University of Tartu
Typ: Artikel
Journal: Astronomy and astrophysics
Band: 699
ISSN: 0004-6361
Publikationsdatum: 14.07.2025
Publikationsstatus: Veröffentlicht
Peer-reviewed: Ja
ASJC Scopus Sachgebiete: Astronomie und Astrophysik, Astronomie und Planetologie
Elektronische Version(en): https://doi.org/10.1051/0004-6361/202449922 (Zugang: Offen)

BibTeX

@article{09466c7b19c04f1594a6dbe84994911b,
title = "Shadow of quadrupole-deformed compact objects in a local dark-matter shell",
abstract = "This work investigated observational properties, namely the shadow and photon ring structure, of emission profiles originating near compact objects. In particular, we considered a distorted and deformed compact object characterized by two quadrupole parameters and surrounded by an optically thin and geometrically thin accretion disk with different emission profiles modeled by Johnson's standard-unbound (SU) distribution in the reference frame of the emitter. Under these assumptions, we produced the observed intensity profiles and shadow images for a face-on observer. Our results indicate that, due to the fact that modifications of the quadrupole parameters affect the radius of the innermost stable circular orbit (ISCO) and the unstable photon orbits on the equatorial plane, the observed shadow images and their properties are significantly influenced by the quadrupole parameters and emission profiles. Furthermore, we analyzed the impact of the presence of a dark-matter halo in the observational imprints considered and verified that both the increase in the matter contained in the halo or the decrease in the length-scale of the halo led to an increase in the size of the observed shadow. Our results indicate potential degeneracies between the observational features of distorted and deformed compact objects with those of spherically symmetric black holes, which could be assessed by a comparison with the current and future generation of optical experiments in gravitational physics.",
keywords = "Methods: analytical, Methods: numerical",
author = "Shokoufe Faraji and Rosa, {Jo{\~a}o Lu{\'i}s}",
note = "Publisher Copyright: {\textcopyright} 2025 EDP Sciences. All rights reserved.",
year = "2025",
month = jul,
day = "14",
doi = "10.1051/0004-6361/202449922",
language = "English",
volume = "699",
journal = "Astronomy and astrophysics",
issn = "0004-6361",
publisher = "EDP Sciences",
}