Shadows of black holes - IDPASC · 2016. 6. 29. · In fact, the BHs lense each other !multiple...
Transcript of Shadows of black holes - IDPASC · 2016. 6. 29. · In fact, the BHs lense each other !multiple...
![Page 1: Shadows of black holes - IDPASC · 2016. 6. 29. · In fact, the BHs lense each other !multiple shadows! Kerr Black Hole Shadows Hairy Black Holes Shadows of Kerr Black Holes with](https://reader035.fdocuments.us/reader035/viewer/2022063016/5fd54ef8ff117d01f727b783/html5/thumbnails/1.jpg)
Kerr Black Hole Shadows Hairy Black Holes Shadows of Kerr Black Holes with scalar hair
Shadows of black holes
Pedro V. P. da Cunha1, 2
1 Departamento de Física da Universidade de Aveiro and CIDMA2 IST, Universidade de Lisboa
in collaboration with: C. Herdeiro, E. Radu, H. Rúnarsson
PhysRevLett.115.211102
![Page 2: Shadows of black holes - IDPASC · 2016. 6. 29. · In fact, the BHs lense each other !multiple shadows! Kerr Black Hole Shadows Hairy Black Holes Shadows of Kerr Black Holes with](https://reader035.fdocuments.us/reader035/viewer/2022063016/5fd54ef8ff117d01f727b783/html5/thumbnails/2.jpg)
Kerr Black Hole Shadows Hairy Black Holes Shadows of Kerr Black Holes with scalar hair
What is a BH?
Source: Interstellar
Black Holes (BHs) are predicted in General Relativity (GR).
They are compact states from which light cannot escape.
The event horizon is the no turning point.
![Page 3: Shadows of black holes - IDPASC · 2016. 6. 29. · In fact, the BHs lense each other !multiple shadows! Kerr Black Hole Shadows Hairy Black Holes Shadows of Kerr Black Holes with](https://reader035.fdocuments.us/reader035/viewer/2022063016/5fd54ef8ff117d01f727b783/html5/thumbnails/3.jpg)
Kerr Black Hole Shadows Hairy Black Holes Shadows of Kerr Black Holes with scalar hair
Sagittarius A*
Gillessen et al.
Center of the Milky Way→ evidence for a supermassive BH.
Stars orbit an extremely massive object: 4× 106M�.
This massive object is dubbed Sagittarius A*.
![Page 4: Shadows of black holes - IDPASC · 2016. 6. 29. · In fact, the BHs lense each other !multiple shadows! Kerr Black Hole Shadows Hairy Black Holes Shadows of Kerr Black Holes with](https://reader035.fdocuments.us/reader035/viewer/2022063016/5fd54ef8ff117d01f727b783/html5/thumbnails/4.jpg)
Kerr Black Hole Shadows Hairy Black Holes Shadows of Kerr Black Holes with scalar hair
Kerr Black Hole
M
~J
Kerr space-time→ describes a rotating BH in vacuum.
It is the most standard BH in astrophysics.
The BH is uniquely determined by M and J = Ma.
![Page 5: Shadows of black holes - IDPASC · 2016. 6. 29. · In fact, the BHs lense each other !multiple shadows! Kerr Black Hole Shadows Hairy Black Holes Shadows of Kerr Black Holes with](https://reader035.fdocuments.us/reader035/viewer/2022063016/5fd54ef8ff117d01f727b783/html5/thumbnails/5.jpg)
Kerr Black Hole Shadows Hairy Black Holes Shadows of Kerr Black Holes with scalar hair
What is a BH shadow?
Optical perception of a BH→ silhouette over background light.
This dark silhouette is called a shadow.
It is the fingerprint of the BH event horizon and its geometry.
![Page 6: Shadows of black holes - IDPASC · 2016. 6. 29. · In fact, the BHs lense each other !multiple shadows! Kerr Black Hole Shadows Hairy Black Holes Shadows of Kerr Black Holes with](https://reader035.fdocuments.us/reader035/viewer/2022063016/5fd54ef8ff117d01f727b783/html5/thumbnails/6.jpg)
Kerr Black Hole Shadows Hairy Black Holes Shadows of Kerr Black Holes with scalar hair
Shadow of a BH merger
arXiv:1410.7775 [gr-qc]
This is how a BH binary would look like!
Here we have two large shadows.
In fact, the BHs lense each other→ multiple shadows!
![Page 7: Shadows of black holes - IDPASC · 2016. 6. 29. · In fact, the BHs lense each other !multiple shadows! Kerr Black Hole Shadows Hairy Black Holes Shadows of Kerr Black Holes with](https://reader035.fdocuments.us/reader035/viewer/2022063016/5fd54ef8ff117d01f727b783/html5/thumbnails/7.jpg)
Kerr Black Hole Shadows Hairy Black Holes Shadows of Kerr Black Holes with scalar hair
Backwards ray-tracing
Backwards ray-tracing
Numerical integration of light rays yields the shadow.
It is more efficient to evolve the rays backwards in time.
This numerical procedure is called backwards ray-tracing.
![Page 8: Shadows of black holes - IDPASC · 2016. 6. 29. · In fact, the BHs lense each other !multiple shadows! Kerr Black Hole Shadows Hairy Black Holes Shadows of Kerr Black Holes with](https://reader035.fdocuments.us/reader035/viewer/2022063016/5fd54ef8ff117d01f727b783/html5/thumbnails/8.jpg)
Kerr Black Hole Shadows Hairy Black Holes Shadows of Kerr Black Holes with scalar hair
Backwards ray-tracing
Celestial sphere
Reference: arXiv:1410.7775 [gr-qc]
The BH and the observer are placed inside a colored sphere.
BH is in the center of the sphere.
The observer is in the equatorial plane.
![Page 9: Shadows of black holes - IDPASC · 2016. 6. 29. · In fact, the BHs lense each other !multiple shadows! Kerr Black Hole Shadows Hairy Black Holes Shadows of Kerr Black Holes with](https://reader035.fdocuments.us/reader035/viewer/2022063016/5fd54ef8ff117d01f727b783/html5/thumbnails/9.jpg)
Kerr Black Hole Shadows Hairy Black Holes Shadows of Kerr Black Holes with scalar hair
Backwards ray-tracing
Shadows of Kerr BHs
The Kerr shadow is not symmetric due to rotation.
Inside the Einstein ring→ inverted copy of the celestial sphere.
![Page 10: Shadows of black holes - IDPASC · 2016. 6. 29. · In fact, the BHs lense each other !multiple shadows! Kerr Black Hole Shadows Hairy Black Holes Shadows of Kerr Black Holes with](https://reader035.fdocuments.us/reader035/viewer/2022063016/5fd54ef8ff117d01f727b783/html5/thumbnails/10.jpg)
Kerr Black Hole Shadows Hairy Black Holes Shadows of Kerr Black Holes with scalar hair
Backwards ray-tracing
Shadows of Kerr BHs
Adapted K.Thorne.
The edge of the shadow has a recurrence structure.
Photons encircle the black hole an increasing number of times.
![Page 11: Shadows of black holes - IDPASC · 2016. 6. 29. · In fact, the BHs lense each other !multiple shadows! Kerr Black Hole Shadows Hairy Black Holes Shadows of Kerr Black Holes with](https://reader035.fdocuments.us/reader035/viewer/2022063016/5fd54ef8ff117d01f727b783/html5/thumbnails/11.jpg)
Kerr Black Hole Shadows Hairy Black Holes Shadows of Kerr Black Holes with scalar hair
Event Horizon Telescope
Source: Doleman et al.
Event Horizon Telescope→ international array of telescopes.
It aims to probe Sgr A* and obtain the first images of a shadow.
New observational templates are required!
![Page 12: Shadows of black holes - IDPASC · 2016. 6. 29. · In fact, the BHs lense each other !multiple shadows! Kerr Black Hole Shadows Hairy Black Holes Shadows of Kerr Black Holes with](https://reader035.fdocuments.us/reader035/viewer/2022063016/5fd54ef8ff117d01f727b783/html5/thumbnails/12.jpg)
Kerr Black Hole Shadows Hairy Black Holes Shadows of Kerr Black Holes with scalar hair
Introduction to “hair”
Source: Cinema 4D
Uniqueness theorems→ BHs are determined only by M and J.
This lead to the no-hair conjecture.
“Hair” is a metaphor for extra parameters (no Gauss law).
![Page 13: Shadows of black holes - IDPASC · 2016. 6. 29. · In fact, the BHs lense each other !multiple shadows! Kerr Black Hole Shadows Hairy Black Holes Shadows of Kerr Black Holes with](https://reader035.fdocuments.us/reader035/viewer/2022063016/5fd54ef8ff117d01f727b783/html5/thumbnails/13.jpg)
Kerr Black Hole Shadows Hairy Black Holes Shadows of Kerr Black Holes with scalar hair
Scalar fields
Source: Cinema 4D
Scalar fields→ simplest descriptions of matter.
One may search for BH solutions coupled with scalar fields.
However, solutions with “good” matter are very hard to find...
![Page 14: Shadows of black holes - IDPASC · 2016. 6. 29. · In fact, the BHs lense each other !multiple shadows! Kerr Black Hole Shadows Hairy Black Holes Shadows of Kerr Black Holes with](https://reader035.fdocuments.us/reader035/viewer/2022063016/5fd54ef8ff117d01f727b783/html5/thumbnails/14.jpg)
Kerr Black Hole Shadows Hairy Black Holes Shadows of Kerr Black Holes with scalar hair
Kerr BHs with scalar hair
Einstein-Klein-Gordon system
S =
∫d4x√−g[
R16πG
−∇νφ∇νφ∗ − µ2φ∗φ
].
Einstein’s gravity minimally coupled to a complex scalar field φ.
A stationary BH solution exists, in equilibrium with φ.Herdeiro & Radu: PhysRevLett.112.221101
![Page 15: Shadows of black holes - IDPASC · 2016. 6. 29. · In fact, the BHs lense each other !multiple shadows! Kerr Black Hole Shadows Hairy Black Holes Shadows of Kerr Black Holes with](https://reader035.fdocuments.us/reader035/viewer/2022063016/5fd54ef8ff117d01f727b783/html5/thumbnails/15.jpg)
Kerr Black Hole Shadows Hairy Black Holes Shadows of Kerr Black Holes with scalar hair
Shadows of Hairy BHs
Kerr BH with scalar hair Kerr BH (same M, J)
![Page 16: Shadows of black holes - IDPASC · 2016. 6. 29. · In fact, the BHs lense each other !multiple shadows! Kerr Black Hole Shadows Hairy Black Holes Shadows of Kerr Black Holes with](https://reader035.fdocuments.us/reader035/viewer/2022063016/5fd54ef8ff117d01f727b783/html5/thumbnails/16.jpg)
Kerr Black Hole Shadows Hairy Black Holes Shadows of Kerr Black Holes with scalar hair
Shadows of Hairy BHs
0
0.5
1
0.6 0.7 0.8 0.9 1
Mµ
w/(mµ)
Boson Stars (q=1)
extremal KBHsSH
m=1
q=0.97
q=0.85
q=1
q=0
Kerr black holes
The shadows of hairy BHs can be very distinct from Kerr’s.
These shadows are smaller!
![Page 17: Shadows of black holes - IDPASC · 2016. 6. 29. · In fact, the BHs lense each other !multiple shadows! Kerr Black Hole Shadows Hairy Black Holes Shadows of Kerr Black Holes with](https://reader035.fdocuments.us/reader035/viewer/2022063016/5fd54ef8ff117d01f727b783/html5/thumbnails/17.jpg)
Kerr Black Hole Shadows Hairy Black Holes Shadows of Kerr Black Holes with scalar hair
Shadows of Hairy BHs
0
0.5
1
0.6 0.7 0.8 0.9 1
Mµ
w/(mµ)
Boson Stars (q=1)
extremal KBHsSH
m=1
q=0.97
q=0.85
q=1
q=0
Kerr black holes
The shadows of hairy BHs can be very distinct from Kerr’s.
These shadows are smaller!
![Page 18: Shadows of black holes - IDPASC · 2016. 6. 29. · In fact, the BHs lense each other !multiple shadows! Kerr Black Hole Shadows Hairy Black Holes Shadows of Kerr Black Holes with](https://reader035.fdocuments.us/reader035/viewer/2022063016/5fd54ef8ff117d01f727b783/html5/thumbnails/18.jpg)
Kerr Black Hole Shadows Hairy Black Holes Shadows of Kerr Black Holes with scalar hair
Shadows of Hairy BHs
0
0.5
1
0.6 0.7 0.8 0.9 1
Mµ
w/(mµ)
Boson Stars (q=1)
extremal KBHsSH
m=1
q=0.97
q=0.85
q=1
q=0
Kerr black holes
The shadows of hairy BHs can be very distinct from Kerr’s.
These shadows are smaller!
![Page 19: Shadows of black holes - IDPASC · 2016. 6. 29. · In fact, the BHs lense each other !multiple shadows! Kerr Black Hole Shadows Hairy Black Holes Shadows of Kerr Black Holes with](https://reader035.fdocuments.us/reader035/viewer/2022063016/5fd54ef8ff117d01f727b783/html5/thumbnails/19.jpg)
Kerr Black Hole Shadows Hairy Black Holes Shadows of Kerr Black Holes with scalar hair
Shadows of Hairy BHs
0
0.5
1
0.6 0.7 0.8 0.9 1
Mµ
w/(mµ)
Boson Stars (q=1)
extremal KBHsSH
m=1
q=0.97
q=0.85
q=1
q=0
Kerr black holes
The shadows of hairy BHs can be very distinct from Kerr’s.
These shadows are smaller!
![Page 20: Shadows of black holes - IDPASC · 2016. 6. 29. · In fact, the BHs lense each other !multiple shadows! Kerr Black Hole Shadows Hairy Black Holes Shadows of Kerr Black Holes with](https://reader035.fdocuments.us/reader035/viewer/2022063016/5fd54ef8ff117d01f727b783/html5/thumbnails/20.jpg)
Kerr Black Hole Shadows Hairy Black Holes Shadows of Kerr Black Holes with scalar hair
Shadows of Hairy BHs
0
0.5
1
0.6 0.7 0.8 0.9 1
Mµ
w/(mµ)
Boson Stars (q=1)
extremal KBHsSH
m=1
q=0.97
q=0.85
q=1
q=0
Kerr black holes
The shadows of hairy BHs can be very distinct from Kerr’s.
These shadows are smaller!
![Page 21: Shadows of black holes - IDPASC · 2016. 6. 29. · In fact, the BHs lense each other !multiple shadows! Kerr Black Hole Shadows Hairy Black Holes Shadows of Kerr Black Holes with](https://reader035.fdocuments.us/reader035/viewer/2022063016/5fd54ef8ff117d01f727b783/html5/thumbnails/21.jpg)
Kerr Black Hole Shadows Hairy Black Holes Shadows of Kerr Black Holes with scalar hair
Shadows of Hairy BHs
0
0.5
1
0.6 0.7 0.8 0.9 1
Mµ
w/(mµ)
Boson Stars (q=1)
extremal KBHsSH
m=1
q=0.97
q=0.85
q=1
q=0
Kerr black holes
The shadows of hairy BHs can be very distinct from Kerr’s.
These shadows are smaller!
![Page 22: Shadows of black holes - IDPASC · 2016. 6. 29. · In fact, the BHs lense each other !multiple shadows! Kerr Black Hole Shadows Hairy Black Holes Shadows of Kerr Black Holes with](https://reader035.fdocuments.us/reader035/viewer/2022063016/5fd54ef8ff117d01f727b783/html5/thumbnails/22.jpg)
Kerr Black Hole Shadows Hairy Black Holes Shadows of Kerr Black Holes with scalar hair
Shadows of Hairy BHs
0
0.5
1
0.6 0.7 0.8 0.9 1
Mµ
w/(mµ)
Boson Stars (q=1)
extremal KBHsSH
m=1
q=0.97
q=0.85
q=1
q=0
Kerr black holes
The shadows of hairy BHs can be very distinct from Kerr’s.
These shadows are smaller!
![Page 23: Shadows of black holes - IDPASC · 2016. 6. 29. · In fact, the BHs lense each other !multiple shadows! Kerr Black Hole Shadows Hairy Black Holes Shadows of Kerr Black Holes with](https://reader035.fdocuments.us/reader035/viewer/2022063016/5fd54ef8ff117d01f727b783/html5/thumbnails/23.jpg)
Kerr Black Hole Shadows Hairy Black Holes Shadows of Kerr Black Holes with scalar hair
Shadows of Hairy BHs
0
0.5
1
0.6 0.7 0.8 0.9 1
Mµ
w/(mµ)
Boson Stars (q=1)
extremal KBHsSH
m=1
q=0.97
q=0.85
q=1
q=0
Kerr black holes
The shadows of hairy BHs can be very distinct from Kerr’s.
These shadows are smaller!
![Page 24: Shadows of black holes - IDPASC · 2016. 6. 29. · In fact, the BHs lense each other !multiple shadows! Kerr Black Hole Shadows Hairy Black Holes Shadows of Kerr Black Holes with](https://reader035.fdocuments.us/reader035/viewer/2022063016/5fd54ef8ff117d01f727b783/html5/thumbnails/24.jpg)
Kerr Black Hole Shadows Hairy Black Holes Shadows of Kerr Black Holes with scalar hair
Shadows of Hairy BHs
0
0.5
1
0.6 0.7 0.8 0.9 1
Mµ
w/(mµ)
Boson Stars (q=1)
extremal KBHsSH
m=1
q=0.97
q=0.85
q=1
q=0
Kerr black holes
The shadows of hairy BHs can be very distinct from Kerr’s.
These shadows are smaller!
![Page 25: Shadows of black holes - IDPASC · 2016. 6. 29. · In fact, the BHs lense each other !multiple shadows! Kerr Black Hole Shadows Hairy Black Holes Shadows of Kerr Black Holes with](https://reader035.fdocuments.us/reader035/viewer/2022063016/5fd54ef8ff117d01f727b783/html5/thumbnails/25.jpg)
Kerr Black Hole Shadows Hairy Black Holes Shadows of Kerr Black Holes with scalar hair
Shadows of Hairy BHs
Kerr BH with scalar hair Kerr BH (same M, J)
![Page 26: Shadows of black holes - IDPASC · 2016. 6. 29. · In fact, the BHs lense each other !multiple shadows! Kerr Black Hole Shadows Hairy Black Holes Shadows of Kerr Black Holes with](https://reader035.fdocuments.us/reader035/viewer/2022063016/5fd54ef8ff117d01f727b783/html5/thumbnails/26.jpg)
Kerr Black Hole Shadows Hairy Black Holes Shadows of Kerr Black Holes with scalar hair
Shadows of Hairy BHs
![Page 27: Shadows of black holes - IDPASC · 2016. 6. 29. · In fact, the BHs lense each other !multiple shadows! Kerr Black Hole Shadows Hairy Black Holes Shadows of Kerr Black Holes with](https://reader035.fdocuments.us/reader035/viewer/2022063016/5fd54ef8ff117d01f727b783/html5/thumbnails/27.jpg)
Kerr Black Hole Shadows Hairy Black Holes Shadows of Kerr Black Holes with scalar hair
Shadows of Hairy BHs
![Page 28: Shadows of black holes - IDPASC · 2016. 6. 29. · In fact, the BHs lense each other !multiple shadows! Kerr Black Hole Shadows Hairy Black Holes Shadows of Kerr Black Holes with](https://reader035.fdocuments.us/reader035/viewer/2022063016/5fd54ef8ff117d01f727b783/html5/thumbnails/28.jpg)
Kerr Black Hole Shadows Hairy Black Holes Shadows of Kerr Black Holes with scalar hair
Shadows of Hairy BHs
One can try a different pattern just for fun!
![Page 29: Shadows of black holes - IDPASC · 2016. 6. 29. · In fact, the BHs lense each other !multiple shadows! Kerr Black Hole Shadows Hairy Black Holes Shadows of Kerr Black Holes with](https://reader035.fdocuments.us/reader035/viewer/2022063016/5fd54ef8ff117d01f727b783/html5/thumbnails/29.jpg)
Kerr Black Hole Shadows Hairy Black Holes Shadows of Kerr Black Holes with scalar hair
Computational calculations
Source: Sun Microsystems
Previous image: 4000× 6599 pixels.
Amounts to ∼26 million photon orbits!
1/2 day computation in Blafis super-computer (Aveiro).
![Page 30: Shadows of black holes - IDPASC · 2016. 6. 29. · In fact, the BHs lense each other !multiple shadows! Kerr Black Hole Shadows Hairy Black Holes Shadows of Kerr Black Holes with](https://reader035.fdocuments.us/reader035/viewer/2022063016/5fd54ef8ff117d01f727b783/html5/thumbnails/30.jpg)
Kerr Black Hole Shadows Hairy Black Holes Shadows of Kerr Black Holes with scalar hair
The road ahead..
The future work:
build observational templates for the Event Horizon Telescope.
study shadows in detail for different latitude angles.
analyse shadows of BHs with other types of hair.
![Page 31: Shadows of black holes - IDPASC · 2016. 6. 29. · In fact, the BHs lense each other !multiple shadows! Kerr Black Hole Shadows Hairy Black Holes Shadows of Kerr Black Holes with](https://reader035.fdocuments.us/reader035/viewer/2022063016/5fd54ef8ff117d01f727b783/html5/thumbnails/31.jpg)
Kerr Black Hole Shadows Hairy Black Holes Shadows of Kerr Black Holes with scalar hair
Acknowledgements
Work is supported by the FCT IDPASC Portugal grand No.PD/BD/114071/2015 and by the Calouste GulbenkianFoundation.
Computations were performed at the Blafis cluster, in AveiroUniversity, and at the Laboratory for Advanced Computing,University of Coimbra.
@Gr v