The document summarizes research presented at the 29th Midwest Relativity Meeting, focusing on active galactic nuclei (AGN), supermassive black holes (SMBH), and their implications for gravitational physics. It covers historical milestones in gravitational research, AGN classification, detection of relativistic outflows, and methods for measuring black hole spin and mass. Future directions for X-ray astronomy and numerical general relativity methods are also discussed, emphasizing the need for further observations and simulations.

1. Active Galactic Nuclei
Laboratory for Gravitational Physics
Image
Credit:
NASA/JPL-Caltech
Image
Credit:
NASA/JPL-Caltech
Ashkbiz Danehkar
Department of Astronomy, University of Michigan
danehkar@umich.edu
The 29th
Midwest Relativity Meeting, Grand Rapids, Michigan, USA, October 4th
, 2019

2. 10/04/2019 Midwest Relativity Meeting
2
Gravity Timeline
1687: Newtonian gravity
1915: General Relativity
1960-1975: golden age of GR (Kip Throne 1995)
– Cambridge (Sciama’s group)
– Hamburg GR group (Jordan)
– Potsdam AEI (Ehlers’ group)
– Syracuse (Bergmann’s grp)
– UT Austin (Schild’s group)
– ...
local interaction (Einstein field equations)
non-local long-range interaction (Binanchi identities)
Trumper 1964, Hawking 1966, Ellis 1971

3. 10/04/2019 Midwest Relativity Meeting
3
Gravity Timeline
1992-present: golden age of cosmology (Alan Guth 2001)
2019: EHT imaging of SMBH in M87
2016: LIGO detection of gravitational waves
●
(Weiss+Throne+Barich 2017)
1995: acceleration expansion of the universe
(Perlmutter+Schmidt+Riess 2011)
1974: Test of GR in a binary pulsar (Hulse+Taylor 1993)

4. 10/04/2019 Midwest Relativity Meeting
4
Active Galactic Nuclei (AGN)
2019: EHT imaging of SMBH in M87
First Image of a Supermassive Black Hole
Credit:
Science
History
Images
/
Alamy
Stock
Photo

5. 10/04/2019 Midwest Relativity Meeting
5
Active Galactic Nuclei (AGN)
X-ray Observations of AGN (1999-present)
Chandra X-ray Observatory (1999-present)
XMM-Newton, X-ray Multi-Mirror Mission (2000-present)
NuSTAR, Nuclear Spectroscopic Telescope Array (2012-present)
Gierlinski + 1999
Lonanov 2007
Credit: Roen Kelly @ Astronomy

6. 10/04/2019 Midwest Relativity Meeting
6
Active Galactic Nuclei (AGN)
AGN Unified Model (radio-loud & -quiet AGN, Seyfert I & II Galaxies)
Beckmann & Shrader 2012,
Active Galactic Nuclei
Unified Models for AFNs
Antonucci, ARA&A, 1993, 31, 473
Unified Schemes for AGNs
Megan Urry & Padovani, 1995, PASP, 107,
803
(Bernie Fanaroff &
Julia Riley 1974)
AGN Unified Model
• Radio-Quiet AGN
 Seyfert I (BLR+NLR,
compact outflows)
 Seyfert II (NLR)
• Radio-Loud AGN
 FR I (compact radio jets)
 FR II (extended radio jets)
 Blazar (relativistic beams)
(Carl Seyfert 1942)

7. 10/04/2019 Midwest Relativity Meeting
7
Active Galactic Nuclei (AGN)
Dermer & Giebles 2016
AGN Classification (radio-loud & -quiet AGN, Seyfert I & II Galaxies)
Blandford, Netzer, Woltjer 1990, Active Galactic Nuclei

8. 10/04/2019 Midwest Relativity Meeting
8
Ultra-fast Outflow in AGN
Detection of relativistic outflows in X-ray
●
Seyfert I PG 1211+143
Ionized outflow at -0.06c and -0.11 c
Danehkar + 2018
Pounds + 2003,2006,2009
Ionized outflow at -0.06c

9. 10/04/2019 Midwest Relativity Meeting
9
Ultra-fast Outflow in AGN
Detection of relativistic outflows in X-ray
●
Seyfert I PDS 456
Ionized outflow at -0.24c and -0.48 c
Biossay-Malaquin, Danehkar + 2019

10. 10/04/2019 Midwest Relativity Meeting
10
Ultra-fast Outflow in AGN
Detection of relativistic outflows in X-ray
Cappi 2006

11. 10/04/2019 Midwest Relativity Meeting
11
Ultra-fast Outflow in AGN
Correlation between outflow kinematics and physical conditions
Tombesi + 2013
(Ultra-fast outflows)
(Warm Absorbers)

12. 10/04/2019 Midwest Relativity Meeting
12
Ultra-fast Outflow in AGN
X-ray Ionized Outflows in AGN
Ionization parameter
Gas density
Radius
Column
density Shell thickness
Outflow
velocity
Luminosity (0.0136-
13.6 keV)
King & Pounds 2015; XMM-Newton & Suzaku
(42 radio-quiet, Tombesi et al 2011; 51 AGN, Gofford et al. 2013)
BH
mass

13. 10/04/2019 Midwest Relativity Meeting
13
Ultra-fast Outflow in AGN
Theories for Relativistic Outflows in AGN
●
strong magnetic field in accretion flow/disk
of rotating BH
– Blandford-Znajek process (1977) for strong jets from flow
– Blandford-Payne process (1982) for slow winds from disk
●
frame dragging (gravitomagnetism indirectly)
– Penrose process (1971)
– Kerr spacetime of rotating BH
– extracting black-hole rotational energy
●
frame dragging + magnetic field
(e.g. Narayan & Quataert 2005)
●
gravitomagnetism (directly)?
Frame dragging+magnetic
(Narayan & Quataert 2005)
Blandford-Znajek process
(Thorne 1995)

14. 10/04/2019 Midwest Relativity Meeting
14
Supermassive Black Hole Spin
Black Hole Spin Measurement (see Brenneman 2013)
●
Thermal Continuum Fitting (UV observation)
– stellar-mass black hole
– AGN (may problematic due to UV absorption lines!)
●
Inner Disk Reflection Modeling
– AGN (X-ray)
●
High Frequency Quasi-Periodic Oscillations
– AGN + stellar-mass black hole (fully not developed)
●
X-ray Polarimetry
– Need sensitive X-ray polarimter (not available now!)
●
Imaging the Event Horizon Shadow
– Need Very Long Baseline Interferometry (in development)
– Suitable only for Sgr A* and M87
a = J c / G M2
(a: BH spin, J: angular momentum, M: BH mass, G: gravitational constant, c: speed of light)

15. 10/04/2019 Midwest Relativity Meeting
15
Supermassive Black Hole Spin
Relativistically broadened Kα iron line (6.4 keV)
Compton hump (> 10keV)
Black Hole Spin Measurement from X-ray
a = - 1
a = 0
a = 1
Image credit: NASA/JPL-Caltech

16. 10/04/2019 Midwest Relativity Meeting
16
Supermassive Black Hole Spin
BH Spin from Reflection Modeling
●
kerrconv (Brenneman & Reynold 2006)
●
relline (Dauser + 2010)
●
xillver (Garcia + 2010,11,13)
●
relxill (Garcia + 2014)
Dauser & Garcia + 2014

17. 10/04/2019 Midwest Relativity Meeting
17
Supermassive Black Hole Mass
BH Mass from Reverberation Mapping Technique (Kaspi + 2000)
●
Variation in light curves of broad emission line region (BLR) in Seyfert I AGN
●
Time delay in variation of BLR luminosity (Hb 4861A) relative to
variation of accretion disk luminosity (continuum 5100A)
www.techfreaq.de
Bentz + 2006

18. 10/04/2019 Midwest Relativity Meeting
18
SMBH Spin Implication
Black Hole Spin Implication for a Unified AGN Model?
Garofalo + 2010
Beckmann & Shrader 2012,
Active Galactic Nuclei
AGN Unified Model
- Radio-Quiet AGN: Seyfert I, Seyfert II
- Radio-Loud AGN: FR I, FR II (extended radio jets)

19. 10/04/2019 Midwest Relativity Meeting
19
SMBH Spin Implication
Black Hole Spin Implication for a Unified AGN Model?
Danehkar +

20. 10/04/2019 Midwest Relativity Meeting
20
Future Direction for X-ray Astronomy
●
XRISM, X-Ray Imaging and Spectroscopy Mission (2022)
– Japan Aerospace Exploration Agency (JAXA)
– Replacement for Hitomi, ASTRO-H (2016, failed)
●
ATHENA, Advanced Telescope for High Energy Astrophysics (2031)
– European Space Agency (ESA)
●
Lynx X-ray Observatory (proposed 2035)
– National Aeronautics and Space Administration (NASA)
●
Arcus X-ray observatory (proposed 2023)
– NASA

21. 10/04/2019 Midwest Relativity Meeting
21
Proposed Direction for Numerical GR
●
Finite-difference Time-domain (FDTD; 1980)
●
Discontinuous Time-domain Method (FETD; 2000)
●
Finite Element Method (FEM; 1973)
●
Finite Integration Technique (FIT, 1977)
●
….
?
For Maxwell EM equations, there are several numerical methods:
For Einstein field equations (local gravitational interaction), there are several
numerical methods (see review by Font 2003 for numerical GR; Fornt 2008 for
GR+MHD)
For example, for Bianchi dynamical formulas of non-local (Weyl) gravitational fields:
Newtonian Tidal force
Non-Newtonian effect
Gravitational waves
shear induction?
computational
hydrodynamics simulation
not fully developed
angular momentum
●
Finite Difference Method (FDM; 1988)
●
Smoothed Particle Hydrodynamics (SPH; 1977)
●
Spectral Methods (1988)
●
Flow Field-dependent Variation Method (FDV; 2002)
●
….
One of reference books for mathematics of Weyl fields

22. 10/04/2019 Midwest Relativity Meeting
22
Summary
Implication of Supermassive Black Hole Angular Momentum for AGN Outflows?

Relativistic Outflows in AGN measured from
– blue-shifted highly-ionized absorption lines in X-ray spectra

AGN Outflow Physical conditions from
– photo-ionization modeling of absorbers

Black Hole Spin measured from
– relativistic Fe Kα line (6.4 keV)
– Compton hump (> 10keV)

Black Hole Mass measured from
– time delay in BLR vs. disk light curves in
Seyfert I AGN (Reverberation-mapping)

Physical Mechanism behind
relativistic outflows in AGN?
– Need for larger sample and
future X-ray observations (XRISM 2022, ATHENA 2031, Lynx 2035)
– Future developments in numerical methods & simulations of GR hydrodynamics
Credit: Roen Kelly @ Astronomy

23. Image
Credit:
NASA/JPL-Caltech
Image
Credit:
NASA/JPL-Caltech
Thank you for your attention
Thank you for your attention