Black Holes and Accretion: Observational Frontiers
Lead Research Organisation:
University of Cambridge
Department Name: Institute of Astronomy
Abstract
Black holes (BHs) are objects so dense that beyond a certain point even light cannot escape their gravitational attraction, and are prevalent throughout the universe. Supermassive black holes (SMBHs; weighing over a million suns) reside at the centre of every major galaxy, and large numbers of smaller stellar-remnant black holes (StMBHs; tens of solar masses), the evolutionary end-point for the most massive stars, are scattered throughout them.
There is much that we still do not understand about these enigmatic objects. Critically, we do not know how SMBHs grew to be so massive. We now know some SMBHs were already grown when the universe was still in its infancy (~1 billion years old), but we do not know how they were able to grow so quickly. We also see that BHs can launch extreme jets of material traveling close to the speed of light that can significantly influence their surroundings (feedback), but we do not understand how these jets are launched.
These are some of the most important issues in contemporary astrophysics research, and can be addressed by studying how matter falls onto the 'local' SMBHs/StMBHs in our own and neighbouring galaxies (accretion). Observations at X-ray wavelengths in particular have the power to probe the nature and geometry of the infalling material in the immediate vicinity of the black hole. With the recent launch of the NuSTAR observatory, and both the Astro-H and ASTROSAT observatories also soon to be launched, we are entering a period of unprecedented observational capabilities in the X-ray regime. My proposal aims to leverage these new facilities to improve our understanding of this complex accretion process, and in turn of SMBH growth and the physics of jet launching.
Astonishingly, black holes themselves are fully defined by two fundamental properties: mass and spin (rotation). BH spin is a quantity of key importance, as a variety of jet launching models predict that the energy associated with BH rotation may be harnessed to launch these extreme outflows. Measuring BH spin is therefore a vital step in testing these models, and is one of the primary goals of my research.
In terms of understanding SMBH growth, I will take a dual approach. First, spin measurements are again vital, as SMBH spin tells us about the history of how these objects grew: growth via random mergers (chaotic growth) should spin SMBHs down, while growth via periods of prolonged accretion (ordered growth) should spin them up. In addition to measuring spin for SMBHs in the local universe I will begin testing models for how SMBH growth should vary with cosmic time by extending these measurements to much more distant SMBHs with gravitationally lensed sources. These are rare cases in which a foreground galaxy is aligned with our line-of-sight to the SMBH, which acts as a natural lens and significantly magnifies the light received, allowing far more sensitive studies than would otherwise be possible!
Second, I will also study how accretion operates at the most extreme rates, necessary to rapidly grow the SMBHs observed in the early universe given the short growth time available. Accretion at these rates is poorly understood, so further observational constraints are vital. We now that a rare population of 'ultraluminous' X-ray sources are StMBHs exhibiting such accretion. These are therefore ideal targets for further study in order to understand this exotic regime.
In combination, this research will bring significant advances in our understanding of accretion, spin, jets and the formation of the most massive black holes.
There is much that we still do not understand about these enigmatic objects. Critically, we do not know how SMBHs grew to be so massive. We now know some SMBHs were already grown when the universe was still in its infancy (~1 billion years old), but we do not know how they were able to grow so quickly. We also see that BHs can launch extreme jets of material traveling close to the speed of light that can significantly influence their surroundings (feedback), but we do not understand how these jets are launched.
These are some of the most important issues in contemporary astrophysics research, and can be addressed by studying how matter falls onto the 'local' SMBHs/StMBHs in our own and neighbouring galaxies (accretion). Observations at X-ray wavelengths in particular have the power to probe the nature and geometry of the infalling material in the immediate vicinity of the black hole. With the recent launch of the NuSTAR observatory, and both the Astro-H and ASTROSAT observatories also soon to be launched, we are entering a period of unprecedented observational capabilities in the X-ray regime. My proposal aims to leverage these new facilities to improve our understanding of this complex accretion process, and in turn of SMBH growth and the physics of jet launching.
Astonishingly, black holes themselves are fully defined by two fundamental properties: mass and spin (rotation). BH spin is a quantity of key importance, as a variety of jet launching models predict that the energy associated with BH rotation may be harnessed to launch these extreme outflows. Measuring BH spin is therefore a vital step in testing these models, and is one of the primary goals of my research.
In terms of understanding SMBH growth, I will take a dual approach. First, spin measurements are again vital, as SMBH spin tells us about the history of how these objects grew: growth via random mergers (chaotic growth) should spin SMBHs down, while growth via periods of prolonged accretion (ordered growth) should spin them up. In addition to measuring spin for SMBHs in the local universe I will begin testing models for how SMBH growth should vary with cosmic time by extending these measurements to much more distant SMBHs with gravitationally lensed sources. These are rare cases in which a foreground galaxy is aligned with our line-of-sight to the SMBH, which acts as a natural lens and significantly magnifies the light received, allowing far more sensitive studies than would otherwise be possible!
Second, I will also study how accretion operates at the most extreme rates, necessary to rapidly grow the SMBHs observed in the early universe given the short growth time available. Accretion at these rates is poorly understood, so further observational constraints are vital. We now that a rare population of 'ultraluminous' X-ray sources are StMBHs exhibiting such accretion. These are therefore ideal targets for further study in order to understand this exotic regime.
In combination, this research will bring significant advances in our understanding of accretion, spin, jets and the formation of the most massive black holes.
Publications
Gandhi P
(2017)
The weak Fe fluorescence line and long-term X-ray evolution of the Compton-thick active galactic nucleus in NGC 7674
in Monthly Notices of the Royal Astronomical Society
Garcia Javier
(2019)
Probing the Black Hole Engine with Measurements of the Relativistic X-ray Reflection Component
in Bulletin of the American Astronomical Society
García J
(2019)
The 2017 Failed Outburst of GX 339-4: Relativistic X-Ray Reflection near the Black Hole Revealed by NuSTAR and Swift Spectroscopy
in The Astrophysical Journal
García J
(2019)
Implications of the Warm Corona and Relativistic Reflection Models for the Soft Excess in Mrk 509
in The Astrophysical Journal
Hare J
(2020)
NuSTAR Observations of the Transient Galactic Black Hole Binary Candidate Swift J1858.6-0814: A New Sibling of V404 Cyg and V4641 Sgr?
in The Astrophysical Journal
Harrison F
(2016)
THE NuSTAR EXTRAGALACTIC SURVEYS: THE NUMBER COUNTS OF ACTIVE GALACTIC NUCLEI AND THE RESOLVED FRACTION OF THE COSMIC X-RAY BACKGROUND
in The Astrophysical Journal
Heida M
(2019)
Searching for the Donor Stars of ULX Pulsars
in The Astrophysical Journal
Heida M
(2019)
Discovery of a Red Supergiant Donor Star in SN2010da/NGC 300 ULX-1
in The Astrophysical Journal
Huppenkothen D
(2017)
DETECTION OF VERY LOW-FREQUENCY, QUASI-PERIODIC OSCILLATIONS IN THE 2015 OUTBURST OF V404 CYGNI
in The Astrophysical Journal
Jiang (?) J
(2019)
A relativistic disc reflection model for 1H0419-577: Multi-epoch spectral analysis with XMM-Newton and NuSTAR
in Monthly Notices of the Royal Astronomical Society
Jiang (???) J
(2018)
The ultrafast outflow of WKK 4438: Suzaku and NuSTAR X-ray spectral analysis
in Monthly Notices of the Royal Astronomical Society
Jiang J
(2019)
High-density reflection spectroscopy: I. A case study of GX 339-4
in Monthly Notices of the Royal Astronomical Society
Jiang J
(2022)
A NuSTAR and Swift view of the hard state of MAXI J1813-095
in Monthly Notices of the Royal Astronomical Society
Jiang J
(2021)
The awakening beast in the Seyfert 1 Galaxy KUG 1141+371 - I
in Monthly Notices of the Royal Astronomical Society
Jiang J
(2020)
A NuSTAR view of GRS 1716-249 in the hard and intermediate states
in Monthly Notices of the Royal Astronomical Society
Jiang J
(2019)
High Density Reflection Spectroscopy - II. The density of the inner black hole accretion disc in AGN
in Monthly Notices of the Royal Astronomical Society
Jiang(???) J
(2018)
The 1.5 Ms observing campaign on IRAS 13224-3809 - I. X-ray spectral analysis
in Monthly Notices of the Royal Astronomical Society
Kaastra J
(2018)
Recurring obscuration in NGC 3783
in Astronomy & Astrophysics
Kammoun E
(2017)
Coronal properties of the luminous radio-quiet quasar QSO B2202-209
in Monthly Notices of the Royal Astronomical Society
Kamraj N
(2019)
The Broadband X-Ray Spectrum of the X-Ray-obscured Type 1 AGN 2MASX J193013.80+341049.5
in The Astrophysical Journal
Kara E
(2020)
Discovery of a soft X-ray lag in the ultraluminous X-ray source NGC 1313 X-1
in Monthly Notices of the Royal Astronomical Society
Kosec P
(2020)
An ionized accretion disc wind in Hercules X-1
in Monthly Notices of the Royal Astronomical Society
Kosec P
(2018)
A stratified ultrafast outflow in 1H0707-495?
in Monthly Notices of the Royal Astronomical Society
Kosec P
(2020)
Detection of a variable ultrafast outflow in the narrow-line Seyfert 1 galaxy PG 1448+273
in Monthly Notices of the Royal Astronomical Society
Kosec P
(2018)
Evidence for a variable Ultrafast Outflow in the newly discovered Ultraluminous Pulsar NGC 300 ULX-1
in Monthly Notices of the Royal Astronomical Society
Kosec P
(2021)
Ionized emission and absorption in a large sample of ultraluminous X-ray sources
in Monthly Notices of the Royal Astronomical Society
Kosec P
(2017)
Investigating the Evolution of the Dual AGN System ESO 509-IG066
in The Astrophysical Journal
Kosec P
(2022)
The Long Stare at Hercules X-1. I. Emission Lines from the Outer Disk, the Magnetosphere Boundary, and the Accretion Curtain
in The Astrophysical Journal
Kosec P
(2018)
Searching for outflows in ultraluminous X-ray sources through high-resolution X-ray spectroscopy
in Monthly Notices of the Royal Astronomical Society
Kriss G
(2019)
Space Telescope and Optical Reverberation Mapping Project. VIII. Time Variability of Emission and Absorption in NGC 5548 Based on Modeling the Ultraviolet Spectrum
in The Astrophysical Journal
Kriss G
(2018)
HST/COS observations of the newly discovered obscuring outflow in NGC 3783
in Astronomy & Astrophysics
Lansbury G
(2017)
The NuSTAR Serendipitous Survey: The 40-month Catalog and the Properties of the Distant High-energy X-Ray Source Population
in The Astrophysical Journal
Lansbury G
(2017)
The NuSTAR Serendipitous Survey: Hunting for the Most Extreme Obscured AGN at >10 keV
in The Astrophysical Journal
Lau R
(2019)
Uncovering Red and Dusty Ultraluminous X-Ray Sources with Spitzer
in The Astrophysical Journal
Lau R
(2017)
First Detection of Mid-infrared Variability from an Ultraluminous X-Ray Source Holmberg II X-1
in The Astrophysical Journal
Lazar H
(2021)
Spectral and Timing Analysis of NuSTAR and Swift/XRT Observations of the X-Ray Transient MAXI J0637-430
in The Astrophysical Journal
López K
(2017)
A Systematic Search for Near-Infrared Counterparts of Nearby Ultraluminous X-ray sources (II)
in Monthly Notices of the Royal Astronomical Society
López K
(2019)
Discovery and analysis of a ULX nebula in NGC 3521
in Monthly Notices of the Royal Astronomical Society
López K
(2020)
NIR counterparts to ULXs (III): completing the photometric survey and selected spectroscopic results?
in Monthly Notices of the Royal Astronomical Society
Madsen Kristin
(2019)
HEX-P: The High-Energy X-ray Probe
in Bulletin of the American Astronomical Society
Mao J
(2022)
Transient obscuration event captured in NGC 3227 III. Photoionization modeling of the X-ray obscuration event in 2019
in Astronomy & Astrophysics
Masini A
(2017)
The Phoenix galaxy as seen by NuSTAR
in Astronomy & Astrophysics
Mehdipour M
(2017)
Chasing obscuration in type-I AGN: discovery of an eclipsing clumpy wind at the outer broad-line region of NGC 3783
in Astronomy & Astrophysics
Mehdipour M
(2021)
Transient obscuration event captured in NGC 3227 I. Continuum model for the broadband spectral energy distribution
in Astronomy & Astrophysics
Middleton M
(2018)
Lense-Thirring precession in ULXs as a possible means to constrain the neutron star equation of state
in Monthly Notices of the Royal Astronomical Society
Description | Careers Day Speaker at Collyers Sixth Form College |
Form Of Engagement Activity | A talk or presentation |
Part Of Official Scheme? | No |
Geographic Reach | Local |
Primary Audience | Schools |
Results and Impact | I spoke about careers in research at the careers day for A-level students at Collyers Sixth Form College. The goal of the event is to showcase the varied career options that are available for students that choose to take STEM subjects at the undergraduate level, and to encourage them to consider choosing such subjects. Based on the questions afterwards, a number of the students seemed very interested in the possibility of going on to have research careers. |
Year(s) Of Engagement Activity | 2017 |
Description | Guest lectures to AY101 class at the University of Alabama |
Form Of Engagement Activity | A talk or presentation |
Part Of Official Scheme? | No |
Geographic Reach | National |
Primary Audience | Undergraduate students |
Results and Impact | Gave two guest lectures on black holes and neutron stars to the 2020/2021 AY101 classes (astronomy undergraduate students) at the University of Alabama. The talks sparked plenty of discussion with the student body afterwards, indicating a good level of interest in astronomy as a subject. |
Year(s) Of Engagement Activity | 2020,2021 |
Description | Guest speaker at the Institute of Astronomy public observing evenings |
Form Of Engagement Activity | A talk or presentation |
Part Of Official Scheme? | No |
Geographic Reach | Regional |
Primary Audience | Public/other audiences |
Results and Impact | Every Wednesday evening throughout the Winter season he Institute of Astronomy hosts a public observing evening. Prior to going out to observe, the attendees receive a guest talk from a member of the department, in which I have participated. These are designed to help educate the public about astronomy in general, and recent areas in which astronomy research has progressed. These evenings are rather popular, even when the weather is poor! |
Year(s) Of Engagement Activity | 2018 |
URL | http://www.ast.cam.ac.uk/public/public_observing |
Description | Guest speaker for the Cambridge University Astronomical Society |
Form Of Engagement Activity | A talk or presentation |
Part Of Official Scheme? | No |
Geographic Reach | Local |
Primary Audience | Undergraduate students |
Results and Impact | The Cambridge University Astronomical Society, a student-run organisation, run a weekly seminar series throughout term-time with guest lectures from professional astronomers, in which I have participated. These are primarily designed to help discuss recent areas in which astronomy research has progressed with other members of the university (although the events are also open to the public). These evenings are reasonably well attended, and the students are very enthusiastic. |
Year(s) Of Engagement Activity | 2017 |
URL | http://astronomy.soc.srcf.net/ |
Description | Institute of Astronomy Open Day |
Form Of Engagement Activity | Participation in an open day or visit at my research institution |
Part Of Official Scheme? | No |
Geographic Reach | Regional |
Primary Audience | Public/other audiences |
Results and Impact | The Institute of Astronomy Open Day is designed to help educate the general public (of all ages) about astronomy. As part of this event, we ran booth focused on black holes and high-energy astrophysics. This is an annual event, which is always very well attended (>500 attendees) and also very well received. |
Year(s) Of Engagement Activity | 2017 |
URL | http://www.ast.cam.ac.uk/public/open.day |