Black hole images: A review

Chen, Songbai; Jing, Jiliang; Qian, Wei-Liang; Wang, Bin

doi:10.1007/s11433-022-2059-5

Cited by 38 publications

(11 citation statements)

References 185 publications

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“…Note that this BH solution is of the RN-like form. In [644], this was argued to be possibly related to the remnant of global conformal invariance enjoyed by the action defined by equation ( 63), as the extremal RN space-time itself is known to possess a discrete conformal isometry related to spatial inversion 44 . Within the negative p eff regime, p eff > −M 2 /8π is required (else the solution describes a NS), whereas no such restrictions are present in the positive p eff regime.…”

Section: Casementioning

confidence: 99%

“…Nonetheless, we note that the BH solution is equally valid for the η > 0 and η < 0 regimes, provided p eff satisfies p eff > −M 2 /8π, as noted in [644] (albeit with a different notation compared to us), and as we later impose. 44 This symmetry is best known as Couch-Torrence inversion symmetry, and maps (t, r) → (t, M + M 2 /(r − M)) [648] (see also [649,650]). Under this symmetry, the metric of an extremal RN BH transforms as gµν → ω 2 gµν , with ω = M/(r − M), making this a (discrete) conformal symmetry.…”

Section: Casementioning

confidence: 99%

“…On the plane of a distant observer, the boundary of the BH shadow marks the apparent image of the photon region (the boundary of the region of space-time which supports closed spherical photon orbits) 22 , and separates capture orbits from scattering orbits: for detailed reviews on BH shadows, see e.g. [41][42][43][44][45]. Under certain conditions and after appropriate calibration, the radius of the bright ring can serve as a proxy for the BH shadow radius, with very little dependence on the details of the surrounding accretion flow [11,12,28,[46][47][48][49][50][51][52].…”

Section: Introductionmentioning

confidence: 99%

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Horizon-scale tests of gravity theories and fundamental physics from the Event Horizon Telescope image of Sagittarius A ∗

Vagnozzi

Roy

Tsai

et al. 2023

Class. Quantum Grav.

290

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Horizon-scale images of black holes (BHs) and their shadows have opened an unprecedented window onto tests of gravity and fundamental physics in the strong-field regime. We consider a wide range of well-motivated deviations from classical General Relativity (GR) BH solutions, and constrain them using the Event Horizon Telescope (EHT) observations of Sagittarius A* (Sgr A*), connecting the size of the bright ring of emission to that of the underlying BH shadow and exploiting high-precision measurements of Sgr A*’s mass-to-distance ratio. The scenarios we consider, and whose fundamental parameters we constrain, include various regular BHs, string-inspired space-times, violations of the no-hair theorem driven by additional fields, alternative theories of gravity, novel fundamental physics frameworks, and BH mimickers including well-motivated wormhole and naked singularity space-times. We demonstrate that the EHT image of Sgr A* places particularly stringent constraints on models predicting a shadow size larger than that of a Schwarzschild BH of a given mass, with the resulting limits in some cases surpassing cosmological ones. Our results are among the first tests of fundamental physics from the shadow of Sgr A* and, while the latter appears to be in excellent agreement with the predictions of GR, we have shown that a number of well-motivated alternative scenarios, including BH mimickers, are far from being ruled out at present.

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Section: Casementioning

confidence: 99%

Section: Casementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Horizon-scale tests of gravity theories and fundamental physics from the Event Horizon Telescope image of Sagittarius A ∗

Vagnozzi

Roy

Tsai

et al. 2023

Class. Quantum Grav.

290

View full text Add to dashboard Cite

show abstract

“…In previous studies, many works focus on the emission from the accretion flows around BHs [12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29]. According to [30], the EHT Collaboration also considered models that the radiation comes mainly from the jet around a BH and found some of those models has not been rule out by any other observations temporarily.…”

Section: Introductionmentioning

confidence: 99%

Polarized images of charged particles in vortical motions around a magnetized Kerr black hole

Zhang,

Hou,

et al. 2024

J. Cosmol. Astropart. Phys.

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In this work, we study the images of a Kerr black hole (BH) immersed in uniform magnetic fields, illuminated by the synchrotron radiation of charged particles in the jet. We particularly focus on the spontaneously vortical motions (SVMs) of charged particles in the jet region and investigate the polarized images of electromagnetic radiations from the trajectories along SVMs. We notice that there is a critical value ω_c for charged particle released at a given initial position and subjected an outward force, and once |qB_0/m|=|ω_B|>|ω_c| charged particles can move along SVMs in the jet region. We obtain the polarized images of the electromagnetic radiations from the trajectories along SVMs. Our simplified model suggests that the SVM radiations can act as the light source to illuminate the BH and form a photon ring structure.

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“…The analyses of the properties of accretion disks can disclose the motion of matter near the central celestial body, which could offer the opportunity to capture some information from the celestial body because the accretion occurs in the strong gravity region. Therefore, the studies of accretion disks have contributed to the examination of the predictions from various theories of gravity, including general relativity, which may deepen the understanding of the gravitational interaction [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19]. Generally, in terms of their geometrical thickness, accretion disk models can be classified into two types.…”

Section: Introductionmentioning

confidence: 99%

Thick accretion disk configurations around a compact object in the brane-world scenario

Wei,

Chen,

Jing

2023

Commun. Theor. Phys.

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We have studied equipotential surfaces of a thick accretion disk around a Casadio-Fabbri-Mazzacurati (CFM) compact object in the brane-world scenario, which owns a mass parameter together with a parameterized post-newtonian (PPN) parameter. With the increase of the PPN parameter, the size of the thick accretion disk decreases, but the corresponding Roche lobe size increases. Thus, the larger PPN parameter yields the larger region of existing bound disk structures where the fluid is not accreted into the central wormhole. Moreover, with the increase of the PPN parameter, the position of the Roche lobe gradually moves away from the central compact object, the thickness of the region enclosed by the Roche lobe decreases near the compact object, but increases in the region far from the compact object. Our results also show that the pressure gradient in the disk decreases with the PPN parameter. These effects of the PPN parameter on thick accretion disk could help to further understand compact objects in brane-world scenario.

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Black hole images: A review

Cited by 38 publications

References 185 publications

Horizon-scale tests of gravity theories and fundamental physics from the Event Horizon Telescope image of Sagittarius A ∗

Horizon-scale tests of gravity theories and fundamental physics from the Event Horizon Telescope image of Sagittarius A ∗

Polarized images of charged particles in vortical motions around a magnetized Kerr black hole

Thick accretion disk configurations around a compact object in the brane-world scenario

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