Tag Archives: #smbh

Peering into a Galaxy’s Dusty Core to Study an Active Supermassive Black Hole (Planetary Science)

Researchers using NASA’s upcoming James Webb Space Telescope will map and model the core of nearby galaxy Centaurus A.

Centaurus A is a giant of a galaxy, but its appearances in telescope observations can be deceiving. Dark dust lanes and young blue star clusters, which crisscross its central region, are apparent in ultraviolet, visible, and near-infrared light, painting a fairly subdued landscape. But by switching to X-ray and radio light views, a far more raucous scene begins to unfold: From the core of the misshapen elliptical galaxy, spectacular jets of material have erupted from its active supermassive black hole – known as an active galactic nucleus – sending material into space well beyond the galaxy’s limits.

What, precisely, is happening at its core to cause all this activity? Upcoming observations led by Nora Lützgendorf and Macarena García Marín of the European Space Agency using NASA’s James Webb Space Telescope will allow researchers to peer through its dusty core in high resolution for the first time to begin to answer these questions.

“There’s so much going on in Centaurus A,” explains Lützgendorf. “The galaxy’s gas, disk, and stars all move under the influence of its central supermassive black hole. Since the galaxy is so close to us, we’ll be able to use Webb to create two-dimensional maps to see how the gas and stars move in its central region, how they are influenced by the jets from its active galactic nucleus, and ultimately better characterize the mass of its black hole.”

Centaurus A’s dusty core is apparent in visible light, but its jets are best viewed in X-ray and radio light. With upcoming observations from NASA’s James Webb Space Telescope in infrared light, researchers hope to better pinpoint the mass of the galaxy’s central supermassive black hole as well as evidence that shows where the jets were ejected. Credits: X-ray: NASA/CXC/SAO; optical: Rolf Olsen; infrared: NASA/JPL-Caltech; radio: NRAO/AUI/NSF/Univ.Hertfordshire/M.Hardcastle

A Quick Look Back

Let’s hit “rewind” to review a bit of what is already known about Centaurus A. It’s well studied because it’s relatively nearby – about 13 million light-years away – which means we can clearly resolve the full galaxy. The first record of it was logged in the mid-1800s, but astronomers lost interest until the 1950s because the galaxy appeared to be a quiet, if misshapen, elliptical galaxy. Once researchers were able to begin observing with radio telescopes in the 1940s and ’50s, Centaurus A became radically more interesting – and its jets came into view. In 1954, researchers found that Centaurus A is the result of two galaxies that merged, which was later estimated to have occurred 100 million years ago.

With more observations in the early 2000s, researchers estimated that about 10 million years ago, its active galactic nucleus shot out twin jets in opposite directions. When examined across the electromagnetic spectrum, from X-ray to radio light, it’s clear there is far more to this story that we still have to learn.

“Multi-wavelength studies of any galaxy are like the layers of an onion. Each wavelength shows you something different,” said Marín. “With Webb’s near- and mid-infrared instruments, we’ll see far colder gas and dust than in previous observations, and learn much more about the environment at the center of the galaxy.”

Supermassive black holes, which lie at the centers of galaxies, are voracious. They periodically “sip” or “gulp” from the swirling disks of gas and dust that orbit them, which can result in massive outflows that affect star formation locally and farther afield. When NASA’s James Webb Space Telescope begins observing galaxies’ cores, its infrared instruments will pierce through the dust to deliver images and incredibly high-resolution data that allow researchers to learn precisely how one process sets off another, and how they create an enormous feedback loop. Credits: NASA, ESA, and L. Hustak (STScI)

Visualizing Webb’s Data

The team led by Lützgendorf and Marín will observe Centaurus A not only by taking images with Webb, but by gathering data known as spectra, which spread out light into its component wavelengths like a rainbow. Webb’s spectra will reveal high-resolution information about the temperatures, speeds, and compositions of the material at the center of the galaxy.

In particular, Webb’s Near Infrared Spectrograph (NIRSpec and Mid-Infrared Instrument (MIRI) will provide the research team with a combination of data: an image plus a spectrum from within each pixel of that image. This will allow the researchers to build intricate 2D maps from the spectra that will help them identify what’s happening behind the veil of dust at the center – and analyze it from many angles in depth.

Compare this style of modeling to the analysis of a garden. In the same way botanists classify plants based on specific sets of features, these researchers will classify spectra from Webb’s MIRI to construct “gardens” or models. “If you take a snapshot of a garden from a great distance away,” Marín explained, “You will see something green, but with Webb, we will be able to see individual leaves and flowers, their stems, and maybe the soil underneath.”

As the research team digs into the spectra, they’ll build maps from individual parts of the garden, comparing one spectrum to another nearby spectrum. This is analogous to determining which parts contain which plant species based on comparisons of “stems,” “leaves,” and “flowers” as they go.

“When it comes to spectral analysis, we conduct many comparisons,” Marín continued. “If I compare two spectra in this region, maybe I will find that what was observed contains a prominent population of young stars. Or confirm which areas are both dusty and heated. Or maybe we will identify emission coming from the active galactic nucleus.”

In other words, the “ecosystem” of spectra has many levels, which will allow the team to better define precisely what is present and where it is – which is made possible by Webb’s specialized infrared instruments. And, since these studies will build on many that came before, the researchers will be able to confirm, refine, or break new ground by identifying new features.

Video: Watch as the jets and winds from a supermassive black hole affect its host galaxy – and the space hundreds of thousands of light-years away over millions of years.Credits: NASA, ESA, and L. Hustak (STScI)

Weighing the Black Hole in Centaurus A

The combination of images and spectra provided by NIRSpec and MIRI will allow the team to create very high-resolution maps of the speeds of the gas and stars at the center of Centaurus A. “We plan to use these maps to model how the entire disk at the center of the galaxy moves to more precisely determine the black hole’s mass,” Lützgendorf explains.

Since researchers understand how the gravity of a black hole governs the rotation of nearby gas, they can use the Webb data to weigh the black hole in Centaurus A. With a more complete set of infrared data, they will also determine if different parts of the gas are all behaving as anticipated. “I’m looking forward to fully filling out our data,” Lützgendorf said. “I hope to see how the ionized gas behaves and twirls, and where we see the jets.”

The researchers are also hoping to break new ground. “It’s possible we’ll find things we haven’t considered yet,” Lützgendorf explains. “In some aspects, we’ll be covering completely new territory with Webb.” Marín wholeheartedly agrees, and adds that building on a wealth of existing data is invaluable. “The most exciting aspects about these observations is the potential for new discoveries,” she said. “I think we might find something that makes us look back to other data and reinterpret what was seen earlier.”

These studies of Centaurus A will be conducted as part of Gillian Wright and Pierre Ferruit’s joint MIRI and NIRSpec Guaranteed Time Observations programs. All of Webb’s data will ultimately be stored in the publicly accessible Barbara A. Mikulski Archive for Space Telescopes (MAST) at the Space Telescope Science Institute in Baltimore.

The James Webb Space Telescope will be the world’s premier space science observatory when it launches in 2021. Webb will solve mysteries in our solar system, look beyond to distant worlds around other stars, and probe the mysterious structures and origins of our universe and our place in it. Webb is an international program led by NASA with its partners, ESA (European Space Agency) and the Canadian Space Agency.

Featured image: Centaurus A sports a warped central disk of gas and dust, which is evidence of a past collision and merger with another galaxy. It also has an active galactic nucleus that periodically emits jets. It is the fifth brightest galaxy in the sky and only about 13 million light-years away from Earth, making it an ideal target to study an active galactic nucleus – a supermassive black hole emitting jets and winds – with NASA’s upcoming James Webb Space Telescope.Credits: X-ray: NASA/CXC/SAO; optical: Rolf Olsen; infrared: NASA/JPL-Caltech; radio: NRAO/AUI/NSF/Univ.Hertfordshire/M.Hardcastle


Provided by NASA Goddard

Scientists Find Black Holes Could Reach ‘Stupendously Large’ Sizes (Astronomy)

A recent study suggests the possible existence of ‘stupendously large black holes’ or SLABS, even larger than the supermassive black holes already observed in the centres of galaxies.

The research, led by Queen Mary Emeritus Professor Bernard Carr in the School of Physics and Astronomy, together with F. Kühnel (Münich) and L. Visinelli (Frascati), investigated how these SLABs could form and potential limits to their size.

This computer-simulated image shows a supermassive black hole at the core of a galaxy. The black region in the center represents the black hole’s event horizon, where no light can escape the massive object’s gravitational grip. The black hole’s powerful gravity distorts space around it like a funhouse mirror. Light from background stars is stretched and smeared as the stars skim by the black hole. Credits: NASA, ESA, and D. Coe, J. Anderson, and R. van der Marel (STScI)

Whilst there is evidence of the existence of supermassive black holes (SMBHs) in galactic nuclei – with masses from a million to ten billion times that of  the Sun – previous studies have suggested an upper limit to their size due to our current view on how such black holes form and grow.

The existence of SLABS even larger than this could provide researchers with a powerful tool for cosmological tests and improve our understanding of the early Universe.

Challenging existing ideas

It has widely been thought that SMBHs form within a host galaxy and grow to their large sizes by swallowing stars and gas from their surroundings or merging with other black holes. In this case, there is an upper limit, somewhat above ten billion solar masses, on their mass.

In this study, the researchers propose another possibility for how SMBHs could form, which might evade this limit.  They suggest that such SLABs could be ‘primordial’, forming in the early Universe, and well before galaxies.

As ‘primordial’ black holes don’t form from a collapsing star, they could have a wide range of masses, including very small and stupendously large ones.

Professor Bernard Carr said: “We already know that black holes exist over a vast range of masses, with a SMBH of four million solar masses residing at the centre of our own galaxy. Whilst there isn’t currently evidence for the existence of SLABs, it’s conceivable that they could exist and they might also reside outside galaxies in intergalactic space, with interesting observational consequences. However, surprisingly, the idea of SLABs has largely been neglected until now.”

“We’ve proposed options for how these SLABs might form, and hope that our work will begin to motivate discussions amongst the community.”  

Understanding dark matter

Dark matter is thought to make up around 80 per cent of the ordinary mass of the Universe. Whilst we can’t see it, researchers think dark matter exists because of its gravitational effects on visible matter, such as stars and galaxies. However, we still don’t know what the dark matter is.

Primordial black holes are one of the potential candidates. The idea of their existence can be traced back to the 1970s when Professor Carr and Professor Stephen Hawking suggested that in the first moments of the Universe fluctuations in its density could have resulted in some regions collapsing into black holes.

“SLABs themselves could not provide the dark matter,“ said Professor Carr, “but if they exist at all, it would have important implications for the early Universe and would make it plausible that lighter primordial black holes might do so.“

Reference:

Bernard Carr, Florian Kühnel, Luca Visinelli, Constraints on stupendously large black holes, Monthly Notices of the Royal Astronomical Society, Volume 501, Issue 2, February 2021, Pages 2029–2043, https://doi.org/10.1093/mnras/staa3651 https://academic.oup.com/mnras/article/501/2/2029/6000254?login=true

Provided by Queensmary University of London

Galaxies Hit Single, Doubles, and a Triple (Growing Black Holes) (Astronomy)

  • A new study looked at triple galaxy mergers to learn what happens to their supermassive black holes.
  • The results find a single, four doubles, a triple giant black hole remain in six of the seven mergers.
  • A team used several telescopes including Chandra plus specially-developed software to identify these growing black holes.
  • This helps astronomers better understand what role mergers play in how galaxies and their giant black holes grow.

A new study helps reveal what happens to supermassive black holes when three galaxies merge, as reported in our latest press release. This result, which used data from NASA’s Chandra X-ray Observatory and several other telescopes, tells astronomers more about how galaxies and the giant black holes in their centers grow over cosmic time.

This pair of objects comes from a study of seven triple galaxy mergers. By using Chandra and other telescopes, astronomers determined what happened to the supermassive black holes at the centers of the galaxies after the collision of three galaxies. The results show a range of outcomes: a single growing supermassive black hole, four doubles, a triple, and one system where no black holes are rapidly pulling in matter. Two of the doubles are shown here in X-rays (Chandra) and optical light (SDSS and Hubble). This information tells astronomers more about how galaxies and the giant black holes in their centers grow over cosmic time. © X-ray: NASA/CXC/Univ. of Michigan/A. Foord et al.; Optical: SDSS & NASA/STScI

While there have been previous studies of mergers between two galaxies, this is one of the first to systematically look at the consequences for supermassive black holes when three galaxies come together. This panel of images contains data from two of seven galactic collisions in the new study containing two supermassive black holes left growing after the collision. The pair of mergers are seen in X-rays from Chandra (left in purple) and optical data (right) from NASA’s Hubble Space Telescope and the Sloan Digital Sky Survey (SDSS). Circles in a labeled version of the Chandra image show X-rays from hot gas falling towards each black hole.

These triple galaxy mergers were first identified by sifting through data from the SDSS and NASA’s WISE mission and then comparing the results to X-ray data in the Chandra archive. This method identified seven triple galaxy mergers located between 370 million and one billion light years from Earth.

Using specialized software, the team went through Chandra data targeting these systems to detect X-ray sources marking the location of growing supermassive black holes. As material falls toward a black hole, it gets heated to millions of degrees and produces X-rays. The combination of the new software and Chandra’s sharp X-ray vision enabled the researchers to identify the black holes despite their close proximity in the images.

Out of seven triple galaxy mergers, there results are: one with a single growing supermassive black hole, four with double growing supermassive black holes (two of which are shown in the main graphics), and one that is a triple. The final merger of three galaxies they studied seems to have no X-ray emission detected from the supermassive black holes. This means that none of the supermassive black holes were left rapidly pulling in matter. In the systems with multiple black holes, the separations between them range between about 10,000 and 30,000 light years.

Once they found evidence for bright X-ray sources as candidates for growing supermassive black holes in the Chandra data, the researchers incorporated archival data from other telescopes such as WISE mission, the Infrared Astronomical Satellite, and the Two Micron All Sky Telescope as another check in the process.

Studies of triple mergers can help scientists understand whether pairs of supermassive black holes can approach so close to each other that they make ripples in spacetime called gravitational waves. The energy lost by these waves will inevitably cause the black holes to merge.

Adi Foord presented the new study, which she worked on as part of her Ph.D. at the University of Michigan, at the 237th meeting of the American Astronomical Society, which is being held virtually from January 11-15, 2021. Two papers describing this work have recently been accepted for publication in The Astrophysical Journal and preprints are available here and here.

NASA’s Marshall Space Flight Center manages the Chandra program. The Smithsonian Astrophysical Observatory’s Chandra X-ray Center controls science from Cambridge Massachusetts and flight operations from Burlington, Massachusetts.

Provided by Chandra X-ray Observatory

The Earliest Supermassive Black Hole and Quasar in the Universe (Astronomy)

NOIRLab facilities provide key observations.

The most distant quasar known has been discovered. The quasar, observed just 670 million years after the Big Bang, is 1000 times more luminous than the Milky Way. It is powered by the earliest known supermassive black hole, which weighs in at more than 1.6 billion times the mass of the Sun. Seen more than 13 billion years ago, this fully formed distant quasar is also the earliest yet discovered, providing astronomers with insight into the formation of massive galaxies in the early Universe. The result was released today at the January 2021 meeting of the American Astronomical Society.

An artist’s impression of quasar J0313-1806 showing the supermassive black hole and the extremely high velocity wind. The quasar, seen just 670 million years after the Big Bang, is 1000 times more luminous than the Milky Way, and is powered by the earliest known supermassive black hole, which weighs in at more than 1.6 billion times the mass of the Sun. Credit: NOIRLab/NSF/AURA/J. da Silva

Quasars, which are powered by the feeding frenzies of colossal supermassive black holes, are the most energetic objects in the Universe. They occur when gas in the superheated accretion disk around a supermassive black hole is inexorably drawn inwards, shedding energy across the electromagnetic spectrum. The amount of electromagnetic radiation emitted by quasars is enormous, with the most massive examples easily outshining entire galaxies. Today, an international team of astronomers has announced the discovery of J0313-1806, the most distant quasar known to date.[1]

The most distant quasars are crucial for understanding how the earliest black holes formed and for understanding cosmic reionization — the last major phase transition of our Universe,” said Xiaohui Fan, study co-author and Regents Professor of Astronomy at the University of Arizona.[2]

J0313-1806 is seen more than 13 billion years ago. As the most distant quasar known, it is also the earliest, being fully formed only about 670 million years after the Big Bang. The new quasar is more than ten trillion times as luminous as our Sun — meaning that it pours out one thousand times more energy than the entire Milky Way Galaxy. The source of this quasar’s power is a supermassive black hole 1.6 billion times as massive as the Sun — the earliest black hole currently known to exist in the Universe.[3]

The presence of such a massive black hole so early in the Universe’s history challenges theories of black hole formation as astronomers need to explain how it came into existence when it barely had the time to do so. Feige Wang, NASA Hubble fellow at the University of Arizona and lead author of the research paper, explains: “Black holes created by the very first massive stars could not have grown this large in only a few hundred million years.

Video: This is CosmoView Episode 17 for press release noirlab2102: The Earliest Supermassive Black Hole and Quasar in the Universe Credit: Images and Videos: NOIRLab/NSF/AURA/J. da Silva, ESO/M.Kornmesser, CTIO/D. Munizaga, International Gemini Observatory/Kwon O Chul. Music: Stellardrone – Comet Halley

The observations that led to this discovery were made using a variety of telescopes, including three National Science Foundation NOIRLab facilities — the Víctor M. Blanco 4-meter Telescope at Cerro Tololo Inter-American ObservatoryGemini South, and Gemini North. Data from the Blanco Telescope, taken as part of the DESI Legacy Imaging Surveys, which are served to the astronomical community via the Astro Data Lab at NOIRLab’s Community Science and Data Center (CSDC), helped to first identify J0313-1806, while Gemini South observations were used to confirm its identity as a quasar. High-quality spectra from two Maunakea observatories in Hawai‘i — Gemini North and W. M. Keck Observatory —  were used to measure the mass of the central supermassive black hole. 

The most distant quasars and earliest black holes are important markers in the history of the Universe,” said Program Director Martin Still of the National Science Foundation. “The researchers combined several of NSF’s NOIRLab facilities to make this discovery.” 

As well as weighing the monster black hole, the Gemini North and Keck Observatory observations uncovered an extremely fast outflow emanating from the quasar in the form of a high-velocity wind, which is traveling at 20% of the speed of light. “The energy released by such an extreme high-velocity outflow is large enough to impact the star formation in the entire quasar host galaxy,” said Jinyi Yang, Peter A. Strittmatter postdoctoral fellow of Steward Observatory at the University of Arizona. This is the earliest known example of a quasar sculpting the growth of its host galaxy, making J0313-1806 a promising target for future observations.

The galaxy hosting J0313-1806 is undergoing a spurt of star formation, producing new stars 200 times faster than the Milky Way. The combination of this intense star formation, the luminous quasar, and the high-velocity outflow make J0313-1806 and its host galaxy a promising natural laboratory for understanding the growth of supermassive black holes and their host galaxies in the early Universe.

This would be a great target to investigate the formation of the earliest supermassive black holes,” concluded Feige Wang. “We also hope to learn more about the effect of quasar outflows on their host galaxy — as well as to learn how the most massive galaxies formed in the early Universe.

Notes

[1] At a redshift of 7.64.

[2] There are two phase transitions of the Universe.

[3] Distance and time are closely entwined in astronomy, as the light from distant objects takes time to reach observers here on Earth. We see the Sun as it was 8 minutes ago, and our latest observations of the heart of the Milky Way show it as it was over 25,000 years ago. The further astronomers look from Earth, the further back in time they see.

Reference: Feige Wang, Jinyi Yang, Xiaohui Fan, Joseph F. Hennawi, Aaron J. Barth, Eduardo Banados, Fuyan Bian, Konstantina Boutsia, Thomas Connor, Frederick B. Davies, Roberto Decarli, Anna-Christina Eilers, Emanuele Paolo Farina, Richard Green, Linhua Jiang, Jiang-Tao Li, Chiara Mazzucchelli, Riccardo Nanni, Jan-Torge Schindler, Bram Venemans, Fabian Walter, Xue-Bing Wu, Minghao Yue, “A Luminous Quasar at Redshift 7.642”, ArXiv, 2021. https://arxiv.org/abs/2101.03179

Provided by Noirlabs

IMAGE RELEASE: A Blazar In the Early Universe (Astronomy)

The supersharp radio “vision” of the National Science Foundation’s Very Long Baseline Array (VLBA) has revealed previously unseen details in a jet of material ejected at three-quarters the speed of light from the core of a galaxy some 12.8 billion light-years from Earth. The galaxy, dubbed PSO J0309+27, is a blazar, with its jet pointed toward Earth, and is the brightest radio-emitting blazar yet seen at such a distance. It also is the second-brightest X-ray emitting blazar at such a distance.

The VLBA image of the blazar PSO J0309+27 is composed of data from three observations made at different radio frequencies. Red is from an observation at 1.5 GHz; green from 5 GHz; and blue from 8.4 GHz. The lower-frequency, or longer wavelength, data show the large-scale structure of the object; the intermediate- and higher-frequency data reveal increasingly smaller structures invisible to the VLBA at the lower frequency. Credit: Spingola et al.; Bill Saxton, NRAO/AUI/NSF.

In this image, the brightest radio emission comes from the galaxy’s core, at bottom right. The jet is propelled by the gravitational energy of a supermassive black hole at the core, and moves outward, toward the upper left. The jet seen here extends some 1,600 light-years, and shows structure within it.

The blazar PSO J0309+27 is in the constellation Aries. Credit: Bill Saxton, NRAO/AUI/NSF

At this distance, PSO J0309+27 is seen as it was when the universe was less than a billion years old, or just over 7 percent of its current age.

An international team of astronomers led by Cristiana Spingola of the University of Bologna in Italy, observed the galaxy in April and May of 2020. Their analysis of the object’s properties provides support for some theoretical models for why blazars are rare in the early universe. The researchers reported their results in the journal Astronomy & Astrophysics.

VLBA image of the blazar PSO J0309+27, 12.8 billion light-years from Earth. Credit: Spingola et al.; Bill Saxton, NRAO/AUI/NSF.

The National Radio Astronomy Observatory is a facility of the National Science Foundation, operated under cooperative agreement by Associated Universities, Inc.

Reference: https://www.aanda.org/articles/aa/pdf/2020/11/aa39458-20.pdf

Provided by NRAO

Scientists Complete Yearlong Pulsar Timing Study After Reviving Long-dormant Radio Telescopes (Astronomy)

While the scientific community grapples with the loss of the Arecibo radio telescope, astronomers who recently revived a long-dormant radio telescope array in Argentina hope it can help modestly compensate for the work Arecibo did in pulsar timing. Last year, scientists at Rochester Institute of Technology and the Instituto Argentino de Radioastronomía (IAR) began a pulsar timing study using two upgraded radio telescopes in Argentina that previously lay unused for 15 years.

Scientists from RIT and IAR just completed a yearlong pulsar timing study using two upgraded radio telescopes in Argentina that previously lay unused for 15 years. The results will be published in ‘The Astrophysical Journal.’ © RIT

The scientists are releasing observations from the first year in a new study to be published in The Astrophysical Journal. Over the course of the year, they studied the bright millisecond pulsar J0437−4715. Pulsars are rapidly rotating neutron stars with intense magnetic fields that regularly emit radio waves, which scientists study to look for gravitational waves caused by the mergers of supermassive black holes.

Professor Carlos Lousto, a member of RIT’s School of Mathematical Sciences and the Center for Computational Relativity and Gravitation (CCRG), said the first year of observations proved to be very accurate and provided some bounds to gravitational waves, which can help increase the sensitivity of existing pulsar timing arrays. He said that over the course of the next year they plan to study a younger, less stable pulsar that is more prone to glitches. He hopes to leverage machine learning and artificial intelligence to better understand the individual pulses emitted by pulsars and predict when glitches occur.

“Every second of observation has 11 pulses and we have thousands of hours of observation, so it is a lot of data,” said Lousto. “What we hope to accomplish is analogous to monitoring the heartbeat one by one to learn to predict when someone is going to have a heart attack.”

Lousto said Ph.D. students from RIT’s programs in astrophysical sciences and technology, mathematical modeling, and computer science are at the forefront of the analysis. RIT has a remote station called the Pulsar Monitoring in Argentina Data Enabling Network (PuMA-DEN) to control the radio telescopes and store the data collected. He said the opportunities presented by the collaboration are important for the students from the College of Science and Golisano College of Computing and Information Sciences because “the careers in astronomy are changing very quickly, so you have to keep up with new technology and new ideas.”

In the longer term, Lousto said RIT and IAR are seeking out other radio telescopes that can be upgraded for pulsar timing studies, further filling the gap left behind by Arecibo. RIT and IAR’s observations seek to contribute to the larger efforts of the North American Nanohertz Observatory for Gravitation Waves (NANOGrav) and the International Pulsar Timing Array, an collaboration of scientists working to detect and study the impact of low frequency gravitational waves passing between the pulsars and the Earth.

For more information, you can read the study that will be published in The Astrophysical Journal on the arXiv preprint server.

Provided by Rochester Institute of Technology

Graduate Student’s BADASS Code Has Astronomical Benefits (Planetary Science)

Open-source code developed at UC Riverside is free, versatile, and easy to use.

An astro-statistics course University of California, Riverside, graduate student Remington O. Sexton took three years ago taught him techniques that led him to develop free, open-source code benefiting astronomers everywhere.

Remington Sexton earned his doctoral degree in September 2020 from UC Riverside. © Remington Sexton, UC Riverside.

Called BADASS, which stands for Bayesian AGN Decomposition Analysis for SDSS Spectra, the code in its current form fits astronomical spectra of active galactic nuclei, or AGNs, from the Sloan Digital Sky Survey, or SDSS, using advanced statistical methods.

“The code is unique in that it finally provides a way for astronomers to fit the stellar motions of stars simultaneously with many other components, is written in the popular programming language Python, and is versatile enough to fit not just AGNs, but normal galaxies as well,” said Sexton, who earned his doctoral degree in physics and astronomy in September 2020.

Sexton’s breakthrough work is published in the January 2021 issue of the Monthly Notices of the Royal Astronomical Society.

AGN is the general term used to describe a supermassive black hole in the center of a galaxy that is actively accreting material, usually in the form of interstellar gas, using its strong gravitational influence. AGNs are common; but not all galaxies have them at their centers. Each galaxy’s center is believed, however, to have a supermassive black hole. Normal galaxies, such as the Milky Way, lack actively accreting black holes.

Different celestial objects produce different types of spectra. An object’s spectrum helps astronomers identify what type of object it is. Light from a celestial body with no intervening matter produces a spectrum that appears as a continuum. A challenge in astronomy has been separating the contribution of stellar light and the contribution of AGN light from each other in the galaxy’s main spectral continuum.

“The challenge is separating the two from each other, that is, isolating the stellar component from the AGN light contribution,” Sexton said. “Aside from being versatile enough to fit many kinds of astronomical objects, which many codes aren’t designed for, BADASS simultaneously fits stellar kinematics simultaneously with all other components in the spectra. Codes in the past used a two-step process of fitting stellar kinematics and other components independently. But this could introduce biases or uncertainties. The best way to perform spectral decomposition is to fit all components simultaneously. This is what BADASS does.”

Sexton designed BADASS also to detect and fit ionized gas outflows typically seen in optical emission line features and is the first to incorporate a set of specific criteria for their detection. Ionized gas outflow refers to the bulk motion of interstellar gas capable of escaping the gravitational influence of its host galaxy and the blackhole.

“Ionized gas outflows have become a hot topic in the past decade and could explain how supermassive black holes and galaxies co-evolve with each other over cosmic time,” said coauthor Gabriela Canalizo, a professor of physics and astronomy at UC Riverside and Sexton’s doctoral advisor.

Currently, BADASS is only being used to fit AGN objects. Sexton emphasized, however, that the code is versatile, easy to use, and can fit other objects such as normal galaxies.

“BADASS can be used for fitting normal non-AGN host galaxies, and even individual stars,” he said. “Currently, its usage is strictly for astronomical spectra, but the statistical framework BADASS is built on can be generalized for any kind of spectroscopy. That makes it extraordinarily versatile and useful.”

One motivation Sexton had to develop BADASS was to phase out the need for proprietary software — IDL programming language — and replace it with a free open-source language such as Python.

“Now anyone can download BADASS for free and use it,” he said. “It is ready to be run as long as you can install Python and all the packages it requires. Because this code can also detect and fit ionized gas outflows in optical spectra, it could greatly assist in the heightened interest in astronomy now in studying ionized gas outflows by creating larger samples for analysis.”

Sexton and Canalizo were joined in the research by William Matzko of George Mason University in Virginia; Nicholas Darden of UCR; and Varoujan Gorjian of the Jet Propulsion Laboratory in California.

The research was supported partially by the National Science Foundation and the NASA MIRO program through the Fellowships and Internships for Extremely Large Data Sets (FIELDS) in the form of a graduate student fellowship.

The research paper is titled, “Bayesian AGN Decomposition Analysis for SDSS spectra: a correlation analysis of [O III] λ5007 outflow kinematics with AGN and host galaxy properties.”

Provided by University of California Riverside

Odd X-ray Flares From a SMBH Pair Tearing Star (Astronomy)

Using data from NASA’s Swift and ESA’s XMM-Newton satellites, a team of Chinese researchers from Anhui Normal University, National Astronomical Observatories of CAS (NAOC), University of Science and Technology of China, Guangzhou University, Shanghai Astronomical Observatory of CAS, Sun Yat-Sen University, and Peking University found new evidence for the existence of two close supermassive black holes (SMBH) in the center of a normal galaxy. They were discovered because they ripped apart a star, producing flaring X-ray emission, and these X-rays were seen by Swift and XMM-Newton. It is the second stellar tidal disruption event by a candidate supermassive black hole binary known to date, strongly implying that such a phenomenon may not be as rare as we thought before. The discovery provides the smoking gun that galaxies grow through mergers, and most massive galaxies in the Universe harbour at least one supermassive black hole at their center. The research result was recently published on Nature Communications.

Fig.1: A cartoon of a pair of black holes, with the one on top accreting material from a dying star, while the one on bottom breaks the stream of debris. (Credit: ESA/C. Carreau)

On 2 Jan 2016, the Optical Gravitational Lensing Experiment (OGLE) detected a bright optical transient, called OGLE16aaa, coincident with the nucleus of a normal galaxy. Following the optical outburst, Swift observed it frequently but did not detect any X-rays for at least 140 days. Between days 141 and 153 since optical peak, the X-rays appeared and were caught by both Swift and XMM-Newton with a brightening in the flux by a factor of more than 60. Such a rapid X-ray flaring within only two weeks is unusual, which has been confirmed by an independent study led by Jari J.Kajava at Centro de Astrobiologia, Spain. But follow-up observations by Swift showed a remarkable thing: the X-ray flux from this event seems to disappear for some time after the start of the flare. Most surprisingly, about 150 days later, its X-rays reappeared. Then the X-rays fell below detectable levels and appeared again after another 150 days.

Fig.2: Left: X-ray light curve (blue data points) modeled with stellar tidal disruption by a supermassive black hole binary. Right: An artist’s render of the supermassive black hole binary tearing and heating the debris of disrupted stellar materials. (Credit: Shu et.al)

“The overall X-ray evolution follows the t^-5/3 power-law if nothing had happened, well consistent with the expected fading rate from a tidal disruption event (TDE) caused by a SMBH”, said Xinwen Shu, the lead author of the paper from Anhui Normal University.

The puzzling drop-outs in the X-ray light curve had been sparsely seen after other TDEs. “The behavior is exactly the same as the galaxy SDSS J120136.02+330305.5, which can be best explained by a pair of supermassive black holes in the process of swallowing a star”, said Fukun Liu, co-author on the paper from Peking University, China.

The sudden drop-outs and then recoveries of X-rays are because the gravitational tug of one of the black holes disrupted the flow of gas onto the other, which could temporarily deprive it to fuel the X-ray emission. These two black holes should eventually spiral together and merge, as they move in their orbits. “The eventual merger may produce the strongest source of gravitational radiation in the Universe which could be the main target of next generation gravitational wave detectors such as LISA,” said Shuo Li, a researcher from NAOC and co-author of the paper.

If the interpretation of the TDE by a SMBH binary is correct, the X-ray non-detections in the early phase could be due to the obscuration by a dense column of gas, implying that the reprocessing may be a viable mechanism to account for the optical emission. “This is important to understand the difference between the TDE optical and X-ray emission”, said co-author Tinggui Wang, from University of Science and Technology of China.

The paper can be accessed at https://www.nature.com/articles/s41467-020-19675-z.

Provided by NAOC

Hubble Captured Mysterious Dark Rays (Astronomy)

Some of the most stunning views of our sky occur at sunset, when sunlight pierces the clouds, creating a mixture of bright and dark rays formed by the clouds’ shadows and the beams of light scattered by the atmosphere. Astronomers studying the nearby galaxy IC 5063 are tantalized by a similar effect in this new image from the NASA/ESA Hubble Space Telescope. In this case, a collection of narrow bright rays and dark shadows is seen beaming out of the blazingly bright center of the active galaxy, shooting across at least 36,000 light-years.

Credit: NASA, ESA, and W.P. Maksym (CfA)

Astronomers have traced the rays back to the galaxy’s core, the location of an active supermassive black hole. The black hole is feeding on infalling material, producing a powerful gusher of light from superheated gas near it. Although the researchers have developed several plausible theories for the lightshow, the most intriguing idea suggests that the shadows are being cast into space by an inner tube-shaped ring, or torus, of dusty material surrounding the black hole.

IC 5063 resides 156 million light-years from Earth.

Provided by Hubble/ESA