Astronomy Cmarchesin: May 2020

Sunday, May 31, 2020

MAXI J1820+070: Black Hole Outburst Caught on Video

MAXI J1820+070
Credit: X-ray: NASA/CXC/Université de Paris/M. Espinasse et al.; Optical/IR:PanSTARRS

JPEG (728.1 kb) - Large JPEG (6.7 MB) - Tiff (34.2 MB) - More Images

A Tour of a Star Survives Close Call with a Black Hole - More Animations

Astronomers have caught a black hole hurling hot material into space at close to the speed of light. This flare-up was captured in a new movie from NASA's Chandra X-ray Observatory.

The black hole and its companion star make up a system called MAXI J1820+070, located in our Galaxy about 10,000 light years from Earth. The black hole in MAXI J1820+070 has a mass about eight times that of the Sun, identifying it as a so-called stellar-mass black hole, formed by the destruction of a massive star. (This is in contrast to supermassive black holes that contain millions or billions of times the Sun's mass.)

The companion star orbiting the black hole has about half the mass of the Sun. The black hole's strong gravity pulls material away from the companion star into an X-ray emitting disk surrounding the black hole.

While some of the hot gas in the disk will cross the "event horizon" (the point of no return) and fall into the black hole, some of it is instead blasted away from the black hole in a pair of short beams of material, or jets. These jets are pointed in opposite directions, launched from outside the event horizon along magnetic field lines. The new footage of this black hole's behavior is based on four observations obtained with Chandra in November 2018 and February, May, and June of 2019, and reported in a paper led by Mathilde Espinasse of the Université de Paris.

The main panel of the graphic is a large optical and infrared image of the Milky Way galaxy from the PanSTARRS optical telescope in Hawaii, with the location of MAXI J1820+070 above the plane of the galaxy marked by a cross. The inset shows a movie that cycles through the four Chandra observations, where "day 0" corresponds to the first observation on November 13th, 2018, about four months after the jet's launch. MAXI J1820+070 is the bright X-ray source in the middle of the image and sources of X-rays can be seen moving away from the black hole in jets to the north and south. MAXI J1820+070 is a point source of X-rays, although it appears to be larger than a point source because it is much brighter than the jet sources. The southern jet is too faint to be detected in the May and June 2019 observations.

Just how fast are the jets of material moving away from the black hole? From Earth's perspective, it looks as if the northern jet is moving at 60% the speed of light, while the southern one is traveling at an impossible-sounding 160% of light speed!

This is an example of superluminal motion, a phenomenon that occurs when something travels towards us near the speed of light, along a direction close to our line of sight. This means the object travels almost as quickly towards us as the light it generates, giving the illusion that the jet's motion is more rapid than the speed of light. In the case of MAXI J1820+070, the southern jet is pointing towards us and the northern jet is pointing away from us, so the southern jet appears to be moving faster than the northern one. The actual velocity of the particles in both jets is greater than 80% of the speed of light.

Illustration of a Black Hole Accreting Matter from a Companion Star and Producing Jets

Credit: NASA/CXC/M.Weiss

Only two other examples of such high-speed expulsions have been seen in X-rays from stellar-mass black holes.

MAXI J1820+070 has also been observed at radio wavelengths by a team led by Joe Bright from the University of Oxford, who previously reported the detection of superluminal motion of compact sources based on radio data alone that extended from the launch of the jets on July 7, 2018 to the end of 2018.

Because the Chandra observations approximately doubled the length of time the jets were followed, a combined analysis of the radio data and the new Chandra data by Espinasse and her team gave more information about the jets. This included evidence that the jets are decelerating as they travel away from the black hole.

Most of the energy in the jets is not converted into radiation, but is instead released when particles in the jets interact with surrounding material. These interactions might be the cause of the jets' deceleration. When the jets collide with surrounding material in interstellar space, shock waves — akin to the sonic booms caused by supersonic aircraft — occur. This process generates particle energies that are higher than that of the Large Hadron Collider.

The researchers estimate that about 400 million billion pounds of material was blown away from the black hole in these two jets launched in July 2018. This amount of mass is comparable to what could be accumulated on the disk around the black hole in the space of a few hours, and is equivalent to about a thousand Halley's Comets or about 500 million times the mass of the Empire State Building.

Studies of MAXI J1820+070 and similar systems promise to teach us more about the jets produced by stellar-mass black holes and how they release their energy once their jets interact with their surroundings.

Radio observations conducted with the Karl G. Jansky Very Large Array and the MeerKAT array were also used to study MAXI J1820+070's jets.

A paper describing these results is published in the latest edition of The Astrophysical Journal Letters and is available online. The authors of the paper are Mathilde Espinasse and Stéphane Corbel (Université de Paris, Paris, France), Philip Kaaret (University of Iowa, Iowa City, Iowa), Evangelia Tremou (Université de Paris , Paris, France), Giulia Migliori (Institute of Radio Astronomy of Bologna, Bologna, Italy), Richard M. Plotkin (University of Nevada, Reno, Nevada), Joe Bright (University of Oxford, Oxford, UK), John Tomsick (University of California, Berkeley, California), Anastasios Tzioumis (Australia Telescope National Facility, CSIRO, Epping, Australia), Rob Fender (University of Oxford, Oxford, UK), Jerome A. Orosz (San Diego State University, San Diego, California), Elena Gallo (University of Michigan, Ann Arbor, Michigan), Jeroen Homan (Eureka Scientific, Oakland, California), Peter G. Jonker (Radboud University, Nijmegen, the Netherlands), James C. A. Miller-Jones (Curtin University, Perth, Australia), David M. Russell (New York University Abu Dhabi, Abu Dhabi, UAE), and Sara Motta (University of Oxford, Oxford, UK).

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

A Quick Look at a Black Hole Outburst Caught on Video

Fast Facts for MAXI J1820+070:

Scale: Optical/infrared image is about 44.5 degrees (8,000 light years) across. X-ray inset image is about 30 arcsec (1.5 light years) across.
Category: Black Holes
Coordinates (J2000): RA 18h 20m 21.9s | Dec 07° 11´ 7.2"
Constellation: Ophiuchus
Observation Date: 5 pointings from November 13, 2018 to June 11, 2019
Observation Time: 39 hours 50 minutes (1 day 15 hours 50 minutes)
Obs. ID: 20207, 20208, 22080, 21203, 21205
Instrument: ACIS

References: Espinasse, M., et al. 2020, ApJ Letters. arXiv:2004.06416
Color Code: X-ray: purple; Optical/IR: red, green, blue

Distance Estimate: About 10,000 light years

Source: NASA’s Chandra X-ray Observatory

Saturday, May 30, 2020

Hubble Finds that "Distance" From the Brightest Stars is Key to Preserving Primordial Discs

PR Image heic2009a

The star cluster Westerlund 2

PR Image heic2009b

Westerlund 2 — Hubble’s 25th anniversary image

PR Image heic2009c

Wide-field image of Westerlund 2 (ground-based image)

Videos

The NASA/ESA Hubble Space Telescope was used to conduct a three-year study of the crowded, massive and young star cluster Westerlund 2. The research found that the material encircling stars near the cluster’s centre is mysteriously devoid of the large, dense clouds of dust that would be expected to become planets in a few million years. Their absence is caused by the cluster’s most massive and brightest stars that erode and disperse the discs of gas and dust of neighbouring stars. This is the first time that astronomers have analysed an extremely dense star cluster to study which environments are favourable to planet formation.

This time-domain study from 2016 to 2019 sought to investigate the properties of stars during their early evolutionary phases and to trace the evolution of their circumstellar environments [1]. Such studies had previously been confined to the nearest, low-density, star-forming regions. Astronomers have now used the Hubble Space Telescope to extend this research to the centre of one of the few young massive clusters in the Milky Way, Westerlund 2, for the first time.

Astronomers have now found that planets have a tough time forming in this central region of the cluster. The observations also reveal that stars on the cluster’s periphery do have immense planet-forming dust clouds embedded in their discs. To explain why some stars in Westerlund 2 have a difficult time forming planets while others do not, researchers suggest this is largely due to location. The most massive and brightest stars in the cluster congregate in the core. Westerlund 2 contains at least 37 extremely massive stars, some weighing up to 100 solar masses. Their blistering ultraviolet radiation and hurricane-like stellar winds act like blowtorches and erode the discs around neighbouring stars, dispersing the giant dust clouds.

“Basically, if you have monster stars, their energy is going to alter the properties of the discs,” explained lead researcher Elena Sabbi, of the Space Telescope Science Institute in Baltimore, USA. “You may still have a disc, but the stars change the composition of the dust in the discs, so it’s harder to create stable structures that will eventually lead to planets. We think the dust either evaporates away in 1 million years, or it changes in composition and size so dramatically that planets don’t have the building blocks to form.”

Westerlund 2 is a unique laboratory in which to study stellar evolutionary processes because it’s relatively nearby, is quite young, and contains a rich stellar population. The cluster resides in a stellar breeding ground known as Gum 29, located roughly 14 000 light-years away in the constellation of Carina (The Ship’s Keel). The stellar nursery is difficult to observe because it is surrounded by dust, but Hubble’s Wide Field Camera 3 can peer through the dusty veil in near-infrared light, giving astronomers a clear view of the cluster. Hubble’s sharp vision was used to resolve and study the dense concentration of stars in the central cluster.

“With an age of less than about two million years, Westerlund 2 harbours some of the most massive, and hottest, young stars in the Milky Way,” said team member Danny Lennon of the Instituto de Astrofísica de Canarias and the Universidad de La Laguna. “The ambient environment of this cluster is therefore constantly bombarded by strong stellar winds and ultraviolet radiation from these giants that have masses of up to 100 times that of the Sun.”

Sabbi and her team found that of the nearly 5000 stars in Westerlund 2 with masses between 0.1 and 5 times the Sun’s mass, 1500 of them show dramatic fluctuations in their luminosity, which is commonly accepted as being due to the presence of large dusty structures and planetesimals. Orbiting material would temporarily block some of the starlight, causing fluctuations in brightness. However, Hubble only detected the signature of dust particles around stars outside the central region. They did not detect these dips in brightness in stars residing within four light-years of the centre.

“We think they are planetesimals or structures in formation,” Sabbi explained. “These could be the seeds that eventually lead to planets in more evolved systems. These are the systems we don’t see close to very massive stars. We see them only in systems outside the centre.”

Thanks to Hubble, astronomers can now see how stars are accreting in environments that are like the early Universe, where clusters were dominated by monster stars. So far, the best known nearby stellar environment that contains massive stars is the starbirth region in the Orion Nebula. However, Westerlund 2 is a richer target because of its larger stellar population.

“Westerlund 2 gives us much better statistics on how mass affects the evolution of stars, how rapidly they evolve, and we see the evolution of stellar discs and the importance of stellar feedback in modifying the properties of these systems,” said Sabbi. “We can use all of this information to inform models of planet formation and stellar evolution.”

This cluster will also be an excellent target for follow-up observations with the upcoming NASA/ESA/CSA James Webb Space Telescope, an infrared observatory. Hubble has helped astronomers identify the stars that have possible planetary structures. With the Webb telescope, researchers will be able to study which discs around stars are not accreting material and which discs still have material that could build up into planets. Webb will also study the chemistry of the discs in different evolutionary phases and watch how they change, to help astronomers determine what role the environment plays in their evolution.

“A major conclusion of this work is that the powerful ultraviolet radiation of massive stars alters the discs around neighbouring stars,” said Lennon. “If this is confirmed with measurements by the James Webb Space Telescope, this result may also explain why planetary systems are rare in old massive globular clusters.”

Notes

[1] These observations were made under Hubble observing programs #14087, #15362, and #15514.

More Information

The Hubble Space Telescope is a project of international cooperation between ESA and NASA.

The international team of astronomers in this study consists of E. Sabbi, M. Gennaro, J. Anderson, V. Bajaj, N. Bastian, J. S. Gallagher, III, M. Gieles, D. J. Lennon, A. Nota, K. C. Sahu, and P. Zeidler.

Image credit: NASA, ESA, the Hubble Heritage Team (STScI/AURA), A. Nota (ESA/STScI), and the Westerlund 2 Science Team

Links

Contacts

Elena Sabbi
Space Telescope Science Institute
Baltimore, MD, USA
Email: sabbi@stsci.edu

Bethany Downer
ESA/Hubble, Public Information Officer
Garching, Germany
Email: Bethany.Downer@partner.eso.org

Source: ESA/Hubble/News

Friday, May 29, 2020

Cosmic bursts unveil Universe’s missing matter

CSIRO’s ASKAP telescope continues to detect new FRBs, adding to the catalogue of these mysterious objects.
Credit: ICRAR and CSIRO/Alex Cherney

The FRB leaves its host galaxy as a bright burst of radio waves.
Credit: ICRAR

The FRB travels from its host galaxy to Earth.
Credit: ICRAR

When travelling through completely empty space, all wavelengths of the FRB travel at the same speed, but when travelling through the missing matter, some wavelengths are slowed down. Credit: ICRAR.

CSIRO’s ASKAP measures the delay between the wavelengths of the FRB, allowing astronomers to calculate the density of the missing matter. Credit: ICRAR and CSIRO/Alex Cherney

The density of the missing matter is calculated using the distance of the FRB from Earth and the delay between the wavelengths of the FRB. Credit: ICRAR

A network of FRBs was used to measure the density of the missing matter.
Credit: ICRAR

A Hubble Space Telescope image of an FRB host galaxy, with the location of the FRB marked in red. This FRB was one of the network used to find the missing matter. Credit: J. Xavier Prochaska/UC Santa Cruz, Jay Chittidi (Maria Mitchell Observatory), and Alexandra Mannings (UC Santa Cruz)

Astronomers have used mysterious fast radio bursts to solve a decades-old mystery of ‘missing matter’, long predicted to exist in the Universe but never detected—until now.

The researchers have now found all of the missing ‘normal’ matter in the vast space between stars and galaxies, as detailed today in the journal Nature.

Lead author Associate Professor Jean-Pierre Macquart, from the Curtin University node of the International Centre for Radio Astronomy Research (ICRAR), said astronomers have been searching for the missing matter for almost thirty years.

“We know from measurements of the Big Bang how much matter there was in the beginning of the Universe,” he said.

“But when we looked out into the present Universe, we couldn’t find half of what should be there. It was a bit of an embarrassment.”

“Intergalactic space is very sparse,” he said. “The missing matter was equivalent to only one or two atoms in a room the size of an average office.”

“So it was very hard to detect this matter using traditional techniques and telescopes.”

The researchers were able to directly detect the missing matter using the phenomenon known as fast radio bursts—brief flashes of energy that appear to come from random directions in the sky and last for just milliseconds.

Scientists don’t yet know what causes them but it must involve incredible energy, equivalent to the amount released by the Sun in 80 years. They have been difficult to detect as astronomers don’t know when and where to look for them.

Associate Professor Macquart said the team detected the missing matter by using fast radio bursts as “cosmic weigh stations”.

“The radiation from fast radio bursts gets spread out by the missing matter in the same way that you see the colours of sunlight being separated in a prism,” he said.

“We’ve now been able to measure the distances to enough fast radio bursts to determine the density of the Universe,” he said. “We only needed six to find this missing matter.”

The missing matter in this case is baryonic or ‘normal’ matter—like the protons and neutrons that make up stars, planets and you and me.

It’s different from dark matter, which remains elusive and accounts for about 85 per cent of the total matter in the Universe.

Co-author Professor J. Xavier Prochaska, from UC Santa Cruz, said we have unsuccessfully searched for this missing matter with our largest telescopes for more than 20 years.

“The discovery of fast radio bursts and their localisation to distant galaxies were the key breakthroughs needed to solve this mystery,” he said.

Associate Professor Ryan Shannon, another co-author from Swinburne University of Technology, said the key was the telescope used, CSIRO’s Australian Square Kilometre Array Pathfinder (ASKAP) radio telescope.

“ASKAP both has a wide field of view, about 60 times the size of the full Moon, and can image in high resolution,” he said. “This means that we can catch the bursts with relative ease and then pinpoint locations to their host galaxies with incredible precision.”

“When the burst arrives at the telescope, it records a live action replay within a fraction of a second,” said Dr Keith Bannister from Australia’s national science agency, CSIRO, who designed the pulse capture system used in this research.

“This enables the precision to determine the location of the fast radio burst to the width of a human hair held 200m away,” he said.

Associate Professor Macquart said the research team had also pinned down the relationship between how far away a fast radio burst is and how the burst spreads out as it travels through the Universe.

“We’ve discovered the equivalent of the Hubble-Lemaitre Law for galaxies, only for fast radio bursts,” he said.

“The Hubble-Lemaitre Law, which says the more distant a galaxy from us, the faster it is moving away from us, underpins all measurements of galaxies at cosmological distances.”

The fast radio bursts used in the study were discovered using ASKAP, which is located at the Murchison Radio-astronomy Observatory in outback Western Australia. The international team involved in the discovery included astronomers from Australia, the United States and Chile.

ASKAP is a precursor for the future Square Kilometre Array (SKA) telescope.

The SKA could observe large numbers of fast radio bursts, giving astronomers greater capability to study the previously invisible structure in the Universe.

Astronomers have used a network of mysterious fast radio bursts (FRBs) to detect half of the Universe’s normal matter, missing until now. Credit: ICRAR with some footage supplied by CSIRO/Alex Cherney, ESO/y. Beletsky and ESO/R. Wesson

Chinese Language version of the FRB animation.

Publication

‘Localized fast radio bursts complete the baryon census of the Universe’ published in Nature on May 28th, 2020.

Contacts

A/Prof Jean-Pierre Macquart (ICRAR / Curtin University)
Ph: +61 9266 9248
Email: jean-pierre.macquart@icrar.org

Kirsten Gottschalk (Media Contact, ICRAR)
Ph: +61 438 361 876
Email: kirsten.gottschalk@icrar.org

April Kleer (Media Contact, Curtin University)
Ph: +61 9266 3353

Email: april.kleer@curtin.edu.au

Source: International Centre for Radio Astronomy Research (ICRAR)

Thursday, May 28, 2020

Astronomers See ‘Cosmic Ring of Fire,’ 11 Billion Years Ago

An artist's impression of the ring galaxy.

Credit: James Josephides, Swinburne Astronomy Productions

Unusual Galaxy Prompts Researchers to Rethink How Structures in the Universe Form

Maunakea, Hawaii – Astronomers have captured an image of a super rare type of galaxy – described as a “cosmic ring of fire” – as it existed 11 billion years ago.

The galaxy, which has roughly the mass of the Milky Way, is circular with a hole in the middle, like a titanic doughnut; its discovery is set to shake up theories about the earliest formation of galactic structures and how they evolve.

The study, which includes data from W. M. Keck Observatory on Maunakea in Hawaii, is published in today’s issue of the journal Nature Astronomy.

“It is a very curious object that we’ve never seen before,” said lead researcher Tiantian Yuan, from Australia’s ARC Centre of Excellence for All Sky Astrophysics in 3 Dimensions (ASTRO 3D). “It looks strange and familiar at the same time.”

The galaxy, named R5519, is 11 billion light-years from the Solar System. The hole at its center is truly massive, with a diameter two billion times longer than the distance between the Earth and the Sun. To put it another way, it is three million times bigger than the diameter of Pōwehi, the supermassive black hole in the galaxy Messier 87, which in 2019 became the first ever to be directly imaged.

“It is making stars at a rate 50 times greater than the Milky Way,” said Yuan, who is an ASTRO 3D Fellow based at the Centre for Astrophysics and Supercomputing at Swinburne University of Technology, in the state of Victoria. “Most of that activity is taking place on its ring – so it truly is a ring of fire.”

An animation showing how the ring galaxy formed
Credit: James Josephides, Swinburne Astronomy Productions

To identify the unusual structure, Yuan worked with colleagues from around the U.S., Australia, Canada, Belgium and Denmark, using Keck Observatory’s adaptive optics combined with its OH-Suppressing Infrared Imaging Spectrograph (OSIRIS), as well as the Observatory’s Multi-Object Spectrograph for Infrared Exploration (MOSFIRE) to gather spectroscopic data of the ring galaxy. The team also used images recorded by NASA’s Hubble Space Telescope.

The evidence suggests R5519 is a type known as a “collisional ring galaxy,” making it the first one ever located in the early universe. There are two kinds of ring galaxies. The more common type forms because of internal processes. The other type forms from immense and violent collisions with other galaxies.

In the nearby “local” universe, collisional ring galaxies are 1000 times rarer than the internally created type. Images of the much more distant R5519 stem from about 10.8 billion years ago, just three billion years after the Big Bang. They indicate that collisional ring galaxies have always been extremely uncommon.

A composite image of the ring galaxy R5519 compiled from single-color images taken by the Hubble Space Telescope.

Credit: Tiantian Yuan/Hubble Space Telescope

ASTRO 3D co-author Ahmed Elagali, who is based at the International Centre for Radio Astronomy Research in Western Australia, said studying R5519 would help determine when spiral galaxies began to develop.

“Further, constraining the number density of ring galaxies through cosmic time can also be used to put constraints on the assembly and evolution of local-like galaxy groups,” said Elagali.

Another co-author, Kenneth Freeman, Duffield Professor of Astronomy at the Australian National University, said the discovery has implications for understanding how galaxies like the Milky Way formed.

“The collisional formation of ring galaxies requires a thin disk to be present in the ‘victim’ galaxy before the collision occurs,” he explained. “The thin disk is the defining component of spiral galaxies: before it assembled, the galaxies were in a disorderly state, not yet recognizable as spiral galaxies.”

Freeman added, “In the case of this ring galaxy, we are looking back into the early universe by 11 billion years, into a time when thin disks were only just assembling. For comparison, the thin disk of our Milky Way began to come together only about nine billion years ago. This discovery is an indication that disk assembly in spiral galaxies occurred over a more extended period than previously thought.”

Source: W. M. Keck Observatory

About Adaptive Optics

W. M. Keck Observatory is a distinguished leader in the field of adaptive optics (AO), a breakthrough technology that removes the distortions caused by the turbulence in the Earth’s atmosphere. Keck Observatory pioneered the astronomical use of both natural guide star (NGS) and laser guide star adaptive optics (LGS AO) and current systems now deliver images three to four times sharper than the Hubble Space Telescope at near-infrared wavelengths. AO has imaged the four massive planets orbiting the star HR8799, measured the mass of the giant black hole at the center of our Milky Way Galaxy, discovered new supernovae in distant galaxies, and identified the specific stars that were their progenitors. Support for this technology was generously provided by the Bob and Renee Parsons Foundation, Change Happens Foundation, Gordon and Betty Moore Foundation, Mt. Cuba Astronomical Foundation, NASA, NSF, and W. M. Keck Foundation.

About OSIRIS

The OH-Suppressing Infrared Imaging Spectrograph (OSIRIS) is one of W. M. Keck Observatory’s “integral field spectrographs.” The instrument works behind the adaptive optics system, and uses an array of lenslets to sample a small rectangular patch of the sky at resolutions approaching the diffraction limit of the 10-meter Keck Telescope. OSIRIS records an infrared spectrum at each point within the patch in a single exposure, greatly enhancing its efficiency and precision when observing small objects such as distant galaxies. It is used to characterize the dynamics and composition of early stages of galaxy formation. Support for this technology was generously provided by the Heising-Simons Foundation and the National Science Foundation.

About MOSFIRE

The Multi-Object Spectrograph for Infrared Exploration (MOSFIRE), gathers thousands of spectra from objects spanning a variety of distances, environments and physical conditions. What makes this large, vacuum-cryogenic instrument unique is its ability to select up to 46 individual objects in the field of view and then record the infrared spectrum of all 46 objects simultaneously. When a new field is selected, a robotic mechanism inside the vacuum chamber reconfigures the distribution of tiny slits in the focal plane in under six minutes. Eight years in the making with First Light in 2012, MOSFIRE’s early performance results range from the discovery of ultra-cool, nearby substellar mass objects, to the detection of oxygen in young galaxies only two billion years after the Big Bang. MOSFIRE was made possible by funding provided by the National Science Foundation. It is currently the most in-demand instrument at Keck Observatory.

About W. M. Keck Observatory

The W. M. Keck Observatory telescopes are among the most scientifically productive on Earth. The two, 10-meter optical/infrared telescopes on the summit of Maunakea on the Island of Hawaii feature a suite of advanced instruments including imagers, multi-object spectrographs, high-resolution spectrographs, integral-field spectrometers, and world-leading laser guide star adaptive optics systems.

Some of the data presented herein were obtained at Keck Observatory, which is a private 501(c) 3 non-profit organization operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation.

The authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Maunakea has always had within the Native Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain.

Wednesday, May 27, 2020

Astronomers Discover New Class of Cosmic Explosions

Artist's conception illustrates the differences in phenomena resulting from an "ordinary" core-collapse supernova explosion, an explosion creating a gamma-ray burst, and one creating a Fast Blue Optical Transient. Details in text. Credit: Bill Saxton, NRAO/AUI/NSF. Hi-Res File

Artist's conception illustrates the phenomena that make up the new class of cosmic explosions called Fast Blue Optical Transients. Credit: Bill Saxton, NRAO/AUI/NSF. Hi-Res File

Astronomers have found two objects that, added to a strange object discovered in 2018, constitute a new class of cosmic explosions. The new type of explosion shares some characteristics with supernova explosions of massive stars and with the explosions that generate gamma-ray bursts (GRBs), but still has distinctive differences from each.

The saga began in June of 2018 when astronomers saw a cosmic blast with surprising characteristics and behavior. The object, dubbed AT2018cow (“The Cow”), drew worldwide attention from scientists and was studied extensively. While it shared some characteristics with supernova explosions, it differed in important aspects, particularly its unusual initial brightness and how rapidly it brightened and faded in just a few days.

In the meantime, two additional blasts — one from 2016 and one from 2018 — also showed unusual characteristics and were being observed and analyzed. The two new explosions are called CSS161010 (short for CRTS CSS161010 J045834-081803), in a galaxy about 500 million light-years from Earth, and ZTF18abvkwla (“The Koala”), in a galaxy about 3.4 billion light-years distant. Both were discovered by automated sky surveys (Catalina Real-time Transient Survey, All-Sky Automated Survey for Supernovae, and Zwicky Transient Facility) using visible-light telescopes to scan large areas of sky nightly.

Two teams of astronomers followed up those discoveries by observing the objects with the National Science Foundation’s Karl G. Jansky Very Large Array (VLA). Both teams also used the Giant Metrewave Radio Telescope in India and the team studying CSS161010 used NASA’s Chandra X-ray Observatory. Both objects gave the observers surprises.

Anna Ho, of Caltech, lead author of the study on ZTF18abvkwla, immediately noted that the object’s radio emission was as bright as that from a gamma-ray burst. “When I reduced the data, I thought I had made a mistake,” she said.

Deanne Coppejans, of Northwestern University, led the study on CSS161010, which found that the object had launched an “unexpected” amount of material into interstellar space at more than half the speed of light. Her Northwestern co-author Raffaella Margutti, said, “It took almost two years to figure out what we were looking at just because it was so unusual.”

In both cases, the follow-up observations indicated that the objects shared features in common with AT2018cow. The scientists concluded that these events, called Fast Blue Optical Transients (FBOTs), represent, along with AT2018cow, a type of stellar explosion significantly different from others. The scientists reported their findings in papers in the Astrophysical Journal and the Astrophysical Journal Letters.

FBOTs probably begin, the astronomers said, the same way as certain supernovae and gamma-ray bursts — when a star much more massive than the Sun explodes at the end of its “normal” atomic fusion-powered life. The differences show up in the aftermath of the initial explosion.

In the “ordinary” supernova of this type, called a core-collapse supernova, the explosion sends a spherical blast wave of material into interstellar space. If, in addition to this, a rotating disk of material briefly forms around the neutron star or black hole left after the explosion and propels narrow jets of material at nearly the speed of light outward in opposite directions, these jets can produce narrow beams of gamma rays, causing a gamma-ray burst.

The rotating disk, called an accretion disk, and the jets it produces, are called an “engine” by astronomers.

FBOTs, the astronomers concluded, also have such an engine. In their case, unlike in gamma-ray bursts, it is enshrouded by thick material. That material probably was shed by the star just before it exploded, and may have been pulled from it by a binary companion.

When the thick material near the star is struck by the blast wave, it causes the bright visible-light burst soon after the explosion that initially made these objects appear so unusual. That bright burst also is why astronomers call these blasts “fast blue optical transients.” This is one of the characteristics that distinguished them from ordinary supernovae.

As the blastwave from the explosion collides with the material around the star as it travels outwards, it produces radio emission. This very bright emission was the important clue that proved that the explosion was powered by an engine.

The shroud of dense material “means that the progenitor star is different from those leading to gamma-ray bursts,” Ho said. The astronomers said that in the Cow and in CSS161010, the dense material included hydrogen, something never seen in in gamma-ray bursts.

Using the W.M. Keck Observatory, the astronomers found that both CSS 161010 and ZTF18abvkwla, like the Cow, are in small, dwarf galaxies. Coppejans said that the dwarf galaxy properties “might allow some very rare evolutionary paths of stars” that lead to these distinctive explosions.

Although a common element of the FBOTs is that all three have a ‘central engine,’ the astronomers caution that the engine also could be the result of stars being shredded by black holes, though they consider supernova-type explosions to be the more likely candidate.

“Observations of more FBOTs and their environments will answer this question,” Margutti said.

To do that, the scientists say they will need to use telescopes covering a wide range of wavelengths, as they have done with the first three objects. “While FBOTs have proven rarer and harder to find than some of us were hoping, in the radio band they’re also much more luminous than we’d guessed, allowing us to provide quite comprehensive data even on events that are far away,” said Daniel Perley, of the Liverpool John Moores University.

The National Radio Astronomy Observatory is a facility of the National Science Foundation, operated under cooperative agreement by Associated Universities, Inc. The study of CSS161010 was partially supported by the Heising-Simons Foundation, NASA, and the National Science Foundation.

Source: National Radio Astronomy Observatory (NRAO)/News

Media Contact:

Dave Finley, Public Information Officer
(575) 835-7302
dfinley@nrao.edu

Coppejans et al. 2020, ApJL, 895, L23
DOI: 10.3847/2041-8213/ab8cc

Ho et al. 2020, ApJ, 895, 49
DOI:10.3847/1538-4357/ab8bcf

Tuesday, May 26, 2020

Galactic crash may have triggered Solar System formation

Credit:ESA

The formation of the Sun, the Solar System and the subsequent emergence of life on Earth may be a consequence of a collision between our galaxy, the Milky Way, and a smaller galaxy called Sagittarius, discovered in the 1990s to be orbiting our galactic home.

Astronomers have known that Sagittarius repeatedly smashes through the Milky Way’s disc, as its orbit around the galaxy’s core tightens as a result of gravitational forces. Previous studies suggested that Sagittarius, a so called dwarf galaxy, had had a profound effect on how stars move in the Milky Way. Some even claim that the 10 000 times more massive Milky Way’s trademark spiral structure might be a result of the at least three known crashes with Sagittarius over the past six billion years.

A new study, based on data gathered by ESA’s galaxy mapping powerhouse Gaia, revealed for the first time that the influence of Sagittarius on the Milky Way may be even more substantial. The ripples caused by the collisions seem to have triggered major star formation episodes, one of which roughly coincided with the time of the formation of the Sun some 4.7 billion years ago.

“It is known from existing models that Sagittarius fell into the Milky Way three times – first about five or six billion years ago, then about two billion years ago, and finally one billion year ago,” says Tomás Ruiz-Lara, a researcher in Astrophysics at the Instituto de Astrofísica de Canarias (IAC) in Tenerife, Spain, and lead author of the new study published in Nature Astronomy.

“When we looked into the Gaia data about the Milky Way, we found three periods of increased star formation that peaked 5.7 billion years ago, 1.9 billion years ago and 1 billion years ago, corresponding with the time when Sagittarius is believed to have passed through the disc of the Milky Way.”

Ripples on the Water

Sagittarius collisions trigger star formation in Milky Way

Credit:ESA

The researchers looked at luminosities, distances and colours of stars within a sphere of about 6500 light years around the Sun and compared the data with existing stellar evolution models. According to Tomás, the notion that the dwarf galaxy may have had such an effect makes a lot of sense.

“At the beginning you have a galaxy, the Milky Way, which is relatively quiet,” Tomás says. “After an initial violent epoch of star formation, partly triggered by an earlier merger as we described in a previous study, the Milky Way had reached a balanced state in which stars were forming steadily. Suddenly, you have Sagittarius fall in and disrupt the equilibrium, causing all the previously still gas and dust inside the larger galaxy to slosh around like ripples on the water.”

In some areas of the Milky Way, these ripples would lead to higher concentrations of dust and gas, while emptying others. The high density of material in those areas would then trigger the formation of new stars.

“It seems that not only did Sagittarius shape the structure and influenced the dynamics of how stars are moving in the Milky Way, it has also led to a build-up of the Milky Way,” says Carme Gallart, a co-author of the paper, also of the IAC. “It seems that an important part of the Milky Way’s stellar mass was formed due to the interactions with Sagittarius and wouldn’t exist otherwise.”

The Birth of the Sun

Dwarf galaxy collisions make stars form in Milky Way
Access the video

In fact, it seems possible that even the Sun and its planets would not have existed if the Sagittarius dwarf had not gotten trapped by the gravitational pull of the Milky Way and eventually smashed through its disc.

“The Sun formed at the time when stars were forming in the Milky Way because of the first passage of Sagittarius,” says Carme. “We don’t know if the particular cloud of gas and dust that turned into the Sun collapsed because of the effects of Sagittarius or not. But it is a possible scenario because the age of the Sun is consistent with a star formed as a result of the Sagittarius effect.”

Every collision stripped Sagittarius of some of its gas and dust, leaving the galaxy smaller after each passage. Existing data suggest that Sagittarius might have passed through the Milky Way’s disc again quite recently, in the last few hundred million years, and is currently very close to it. In fact, the new study found of a recent burst of star formation, suggesting a possible new and ongoing wave of stellar birth.

According to ESA Gaia project scientist Timo Prusti, such detailed insights into the Milky Way’s star formation history wouldn’t be possible before Gaia, the star-mapping telescope launched in late 2013, whose two data releases in 2016 and 2018 revolutionised the study of the Milky Way.

“Some determinations of star formation history in the Milky Way existed before based on data from ESA’s early 1990s Hipparcos mission,” says Timo. “But these observations were focused on the immediate neighbourhood of the Sun. It wasn’t really representative and so it couldn’t uncover those bursts in star formation that we see now.

“This is really the first time that we see a detailed star formation history of the Milky Way. It’s a testament to the scientific power of Gaia that we have seen manifest again and again in countless ground-breaking studies in a period of only a couple of years.”

More information:

“The recurrent impact of the Sagittarius dwarf on the Milky Way star formation history” by T. Ruiz-Lara et al is published in Nature Astronomy.

For more information, please contact:

Tomás Ruiz-Lara
Instituto de Astrofísica de Canarias
San Cristóbal de La Laguna, Tenerife, Spain
Email: tomasruizlara@gmail.com

Carme Gallart
Instituto de Astrofísica de Canarias
San Cristóbal de La Laguna, Tenerife, Spain
Email: carme.gallart@iac.es

ESA Media Relations
Email: media@esa.int

Source: ESA

Monday, May 25, 2020

ALMA Discovers Massive Rotating Disk in Early Universe

Artist impression of the Wolfe Disk, a massive rotating disk galaxy in the early, dusty universe. The galaxy was initially discovered when ALMA examined the light from a more distant quasar (top left). Credit: NRAO/AUI/NSF, S. Dagnello. Hi-Res File

ALMA radio image of the Wolfe Disk, seen when the universe was only ten percent of its current age.

Credit: ALMA (ESO/NAOJ/NRAO), M. Neeleman; NRAO/AUI/NSF, S. Dagnello. Hi-Res File

Video Press Release Brief video (1:20) explaining this research result.

Credit: NRAO/AUI/NSF, S. Dagnello. Download Video

The Wolfe Disk as seen with ALMA (right - in red), VLA (left - in green) and the Hubble Space Telescope (both images - blue). In radio light, ALMA looked at the galaxy’s movements and mass of atomic gas and dust and the VLA measured the amount of molecular mass. In UV-light, Hubble observed massive stars. The VLA image is made in a lower spatial resolution than the ALMA image, and therefore looks larger and more pixelated. Credit: ALMA (ESO/NAOJ/NRAO), M. Neeleman; NRAO/AUI/NSF, S. Dagnello; NASA/ESA Hubble.Hi-Res File

In our 13.8 billion-year-old universe, most galaxies like our Milky Way form gradually, reaching their large mass relatively late. But a new discovery made with the Atacama Large Millimeter/submillimeter Array (ALMA) of a massive rotating disk galaxy, seen when the universe was only ten percent of its current age, challenges the traditional models of galaxy formation. This research appears on 20 May 2020 in the journal Nature.

Galaxy DLA0817g, nicknamed the Wolfe Disk after the late astronomer Arthur M. Wolfe, is the most distant rotating disk galaxy ever observed. The unparalleled power of ALMA made it possible to see this galaxy spinning at 170 miles (272 kilometers) per second, similar to our Milky Way.

“While previous studies hinted at the existence of these early rotating gas-rich disk galaxies, thanks to ALMA we now have unambiguous evidence that they occur as early as 1.5 billion years after the Big Bang,” said lead author Marcel Neeleman of the Max Planck Institute for Astronomy in Heidelberg, Germany.

How did the Wolfe Disk form?

The discovery of the Wolfe Disk provides a challenge for many galaxy formation simulations, which predict that massive galaxies at this point in the evolution of the cosmos grew through many mergers of smaller galaxies and hot clumps of gas.

“Most galaxies that we find early in the universe look like train wrecks because they underwent consistent and often ‘violent’ merging,” explained Neeleman. “These hot mergers make it difficult to form well-ordered, cold rotating disks like we observe in our present universe.”

In most galaxy formation scenarios, galaxies only start to show a well-formed disk around 6 billion years after the Big Bang. The fact that the astronomers found such a disk galaxy when the universe was only ten percent of its current age, indicates that other growth processes must have dominated.

“We think the Wolfe Disk has grown primarily through the steady accretion of cold gas,” said J. Xavier Prochaska, of the University of California, Santa Cruz and coauthor of the paper. “Still, one of the questions that remains is how to assemble such a large gas mass while maintaining a relatively stable, rotating disk.”

Star formation

The team also used the National Science Foundation’s Karl G. Jansky Very Large Array (VLA) and the NASA/ESA Hubble Space Telescope to learn more about star formation in the Wolfe Disk. In radio wavelengths, ALMA looked at the galaxy’s movements and mass of atomic gas and dust while the VLA measured the amount of molecular mass – the fuel for star formation. In UV-light, Hubble observed massive stars. “The star formation rate in the Wolfe Disk is at least ten times higher than in our own galaxy,” explained Prochaska. “It must be one of the most productive disk galaxies in the early universe.”

A ‘normal’ galaxy

The Wolfe Disk was first discovered by ALMA in 2017. Neeleman and his team found the galaxy when they examined the light from a more distant quasar. The light from the quasar was absorbed as it passed through a massive reservoir of hydrogen gas surrounding the galaxy – which is how it revealed itself. Rather than looking for direct light from extremely bright, but more rare galaxies, astronomers used this ‘absorption’ method to find fainter, and more ‘normal’ galaxies in the early universe.

“The fact that we found the Wolfe Disk using this method, tells us that it belongs to the normal population of galaxies present at early times,” said Neeleman. “When our newest observations with ALMA surprisingly showed that it is rotating, we realized that early rotating disk galaxies are not as rare as we thought and that there should be a lot more of them out there.”

“This observation epitomizes how our understanding of the universe is enhanced with the advanced sensitivity that ALMA brings to radio astronomy,” said Joe Pesce, astronomy program director at the National Science Foundation, which funds the telescope. “ALMA allows us to make new, unexpected findings with almost every observation.”

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

Source: National Radio Astronomy Observatory (NRAO)/News

Media contact:

Iris Nijman
News and Public Information Manager
National Radio Astronomy Observatory (NRAO)
inijman@nrao.edu
+1 (434) 249-3423

This research was presented in a paper titled “A Cold, Massive, Rotating Disk 1.5 Billion Years after the Big Bang,” by Marcel Neeleman & J. Xavier Prochaska, et al., appearing in the journal Nature. DOI: 10.1038/s41586-020-2276-y

The Atacama Large Millimeter/submillimeter Array (ALMA), an international astronomy facility, is a partnership of the European Organisation for Astronomical Research in the Southern Hemisphere (ESO), the U.S. National Science Foundation (NSF) and the National Institutes of Natural Sciences (NINS) of Japan in cooperation with the Republic of Chile. ALMA is funded by ESO on behalf of its Member States, by NSF in cooperation with the National Research Council of Canada (NRC) and the Ministry of Science and Technology (MOST) and by NINS in cooperation with the Academia Sinica (AS) in Taiwan and the Korea Astronomy and Space Science Institute (KASI).

ALMA construction and operations are led by ESO on behalf of its Member States; by the National Radio Astronomy Observatory (NRAO), managed by Associated Universities, Inc. (AUI), on behalf of North America; and by the National Astronomical Observatory of Japan (NAOJ) on behalf of East Asia. The Joint ALMA Observatory (JAO) provides the unified leadership and management of the construction, commissioning and operation of ALMA.

Saturday, May 23, 2020

ALMA Spots Twinkling Heart of Milky Way

Artist’s impression of the gaseous disk around the supermassive black hole. Hot spots circling around the black hole could produce the quasi-periodic millimeter emission detected with ALMA. Credit: Keio University

The variation of millimeter emission from Sgr A* detected with ALMA. The different color dots show the flux at different frequencies (blue: 234.0 GHz, green: 219.5 GHz, red: 217.5 GHz). Variations with about a 30-minute period are seen in the diagram. Credit: Y. Iwata et al./Keio University

Astronomers using the Atacama Large Millimeter/submillimeter Array (ALMA) found quasi-periodic flickers in millimeter-waves from the center of the Milky Way, Sagittarius (Sgr) A*. The team interpreted these blinks to be due to the rotation of radio spots circling the supermassive black hole with an orbit radius smaller than that of Mercury. This is an interesting clue to investigate space-time with extreme gravity.

“It has been known that Sgr A* sometimes flares up in millimeter wavelength,” tells Yuhei Iwata, the lead author of the paper published in the Astrophysical Journal Letters and a graduate student at Keio University, Japan. “This time, using ALMA, we obtained high-quality data of radio-wave intensity variation of Sgr A* for 10 days, 70 minutes per day. Then we found two trends: quasi-periodic variations with a typical time scale of 30 minutes and hour-long slow variations.”

Astronomers presume that a supermassive black hole with a mass of 4 million suns is located at the center of Sgr A*. Flares of Sgr A* have been observed not only in millimeter wavelength, but also in infrared light and X-ray. However, the variations detected with ALMA are much smaller than the ones previously detected, and it is possible that these levels of small variations always occur in Sgr A*.

The black hole itself does not produce any kind of emission. The source of the emission is the scorching gaseous disk around the black hole. The gas around the black hole does not go straight to the gravitational well, but it rotates around the black hole to form an accretion disk.

The team focused on short timescale variations and found that the variation period of 30 minutes is comparable to the orbital period of the innermost edge of the accretion disk with the radius of 0.2 astronomical units (1 astronomical unit corresponds to the distance between the Earth and the Sun: 150 million kilometers). For comparison, Mercury, the solar system’s innermost planet, circles around the Sun at a distance of 0.4 astronomical units. Considering the colossal mass at the center of the black hole, its gravity effect is also extreme in the accretion disk.

“This emission could be related with some exotic phenomena occurring at the very vicinity of the supermassive black hole,” says Tomoharu Oka, a professor at Keio University. Their scenario is as follows. Hot spots are sporadically formed in the disk and circle around the black hole, emitting strong millimeter waves. According to Einstein’s special relativity theory, the emission is largely amplified when the source is moving toward the observer with a speed comparable to that of light. The rotation speed of the inner edge of the accretion disk is quite large, so this extraordinary effect arises. The astronomers believe that this is the origin of the short-term variation of the millimeter emission from Sgr A*.

The team supposes that the variation might affect the effort to make an image of the supermassive black hole with the Event Horizon Telescope. “In general, the faster the movement is, the more difficult it is to take a photo of the object,” says Oka. “Instead, the variation of the emission itself provides compelling insight for the gas motion. We may witness the very moment of gas absorption by the black hole with a long-term monitoring campaign with ALMA.” The researchers aim to draw out independent information to understand the mystifying environment around the supermassive black hole.

Additional Information

These observation results were presented in Y. Iwata et al. “Time Variations in the Flux Density of Sgr A* at 230 GHz Detected with ALMA” in the Astrophysical Journal Letters published on April 2, 2020.

The research team members are:

Yuhei Iwata (Keio University), Tomoharu Oka (Keio University), Masato Tsuboi (Japan Space Exploration Agency/The University of Tokyo), Makoto Miyoshi (National Astronomical Observatory of Japan/SOKENDAI), and Shunya Takekawa (National Astronomical Observatory of Japan)

This research was supported by the Japan Society for the Promotion of Science (JSPS) Grant-in-Aid for JSPS Fellows Grant Number JP18J20450.

The original press release was published by the National Astronomical Observatory of Japan (NAOJ), an ALMA partner on behalf of East Asia.

The Atacama Large Millimeter/submillimeter Array (ALMA), an international astronomy facility, is a partnership of the European Southern Observatory (ESO), the U.S. National Science Foundation (NSF) and the National Institutes of Natural Sciences (NINS) of Japan in cooperation with the Republic of Chile. ALMA is funded by ESO on behalf of its Member States, by NSF in cooperation with the National Research Council of Canada (NRC) and the National Science Council of Taiwan (NSC) and by NINS in cooperation with the Academia Sinica (AS) in Taiwan and the Korea Astronomy and Space Science Institute (KASI).

Contacts:

Nicolás Lira
Education and Public Outreach Coordinator
Joint ALMA Observatory, Santiago - Chile
Phone: +56 2 2467 6519
Cell phone: +56 9 9445 7726
Email: nicolas.lira@alma.cl

Masaaki Hiramatsu
Education and Public Outreach Officer, NAOJ Chile
Observatory , Tokyo - Japan
Phone: +81 422 34 3630
Email: hiramatsu.masaaki@nao.ac.jp

Iris Nijman
News and Public Information Manager
National Radio Astronomy Observatory Charlottesville, Virginia - USA
Cell phone: +1 (434) 249 3423
Email: inijman@nrao.edu

Bárbara Ferreira
ESO Public Information Officer
Garching bei München, Germany
Phone: +49 89 3200 6670
Email: pio@eso.org

Source: Atacama Large Millimeter/submillimeter Array (ALMA)

Friday, May 22, 2020

UH REU student helps reveal how galaxies and black holes grow together

Image of a galaxy interaction (left) and a schematic (right) showing how galaxy interactions can produce shocks across an entire galaxy, enhancing molecular hydrogen emission. This component of the interstellar medium can be directly observed only in special circumstances, such as when it changes angular momentum through interactions with high energy photons or collisions with other particles. Credit: Guillard et al. 2009/B. Bays. High-res JPG

Over the past two decades, astronomers have concluded that most, if not all, galaxies host massive black holes at their centers - and the masses of a black hole and its host galaxy are correlated. But how are the two connected? Now, a University of Hawaiʻi at Mānoa Institute for Astronomy (IfA) student participating in the National Science Foundation's (NSF) Research Experiences for Undergraduates (REU) program, may have revealed part of the answer.

Undergraduate Rebecca Minsley, participated in IfA's 2019 REU program, working for ten weeks with her mentor Maunakea Spectroscopic Explorer Deputy Project Scientist Andreea Petric. Sifting meticulously though hundreds of images of galaxies, Minsley began to define a clearer picture of galaxy evolution. "Galaxy growth may be shaped by interactions with other galaxies which contributes to supermassive black holes (SMBH) that grow within the galaxy's center," Minsley explained.

Gas and dust between stars, called the interstellar medium (ISM), is the fuel for both SMBH growth and the formation of new stars. But recent work shows that the ISM may have different properties - especially being warmer - in galaxies that host a growing supermassive black hole in their nuclei, compared to those galaxies that do not. Warmer gas is less likely to collapse into new stars, so this finding may suggest that a growing central SMBH diminishes a galaxy's ability to make new stars.

What might be responsible for heating the ISM? Starlight, especially from hot stars, can do this. But interactions between galaxies - when they collide or even just pass close to each other - can produce large-scale shock waves that compress less dense gas, making it more likely to form stars. Minsley studied the shapes of 630 galaxies using images from the Pan-STARRS survey. She classified the galaxies into mergers, early mergers, and non-mergers. And then compared the shapes to the light output of the same galaxies at longer mid-infrared wavelengths, where she could study the properties of the ISM.

"When galaxies get close enough they go through a sort of galactic dance until they eventually coalesce into a singular entity. These interactions have well documented signatures that allowed me to categorize our set of galaxies." Minsley said. "This project gave me a greater appreciation for the complexity and entanglement of all the processes taking place inside galaxies and the research being done to deconstruct galactic systems is fascinating."

Minsley and collaborators found that within galaxies with active black holes, the ISM is warmer, the ratios of warm molecular gas to other coolants are larger, and other features from dust particles have a wider range of values than in galaxies where the black holes are dormant.

"In the nearby universe we find that the warm ISM of galaxies which host growing supermassive black holes at their centers differs from those that do not," explains Petric. "We speculate that the same processes that funnel fuel to the SMBH also allow us to detect the energy transfer back into the galaxy's ISM." Petric adds that future, more detailed observations, will allow researchers confirm these energy transfer processes.

IfA has been part of the prestigious REU program for almost 20 years, training over 130 students, some of whom are now leaders in different fields of astronomy. Because of this unique opportunity to work in Hawaii with world class facilities and scientists, the IfA receives over 500 applications each term. The focus of their REU program is on identifying students who have potential to succeed in research, but may not have the opportunity and resources.

Nader Haghighipour, the Principal Investigator of IfA's REU program, noted "With our mentors among the world leaders in their respective fields, our REU students are engaged in cutting edge research. Rebecca's work is a prime example of this. We are very proud of our REU students, as almost all of them continued their studies in graduate school, and many of them have gained national recognition."

During the 2020 fall semester, Petric and UH Mānoa undergraduate Diana Castaneda will continue to investigate the ISM of galaxies hosting some of the most luminous growing SMBH in the nearby universe, using a spectrometer aboard the Stratospheric Observatory for Infrared Astronomy (SOFIA) aircraft. The SOFIA observations will allow Castaneda and Petric to gain more insight into the processes by which energy is being transferred between the growing SMBH and the ISM.

This work is published in the May 10th issue of the Astrophysical Journal and is available in preprint form on ArXiv.

Pan-STARRS images of NGC 4088, NGC 0520, NGC 5218, NGC 4922 NED02, illustrating the different features used to classify galaxy mergers, including galaxy asymmetry, tidal tails, galactic shells, multiple nuclei and early/possible mergers for galaxies of similar brightness within 50 kpc of each-other. Credit: A. Petric/B. Bays. Hi-res image

Contacts:

Dr. Andreea Petric
apetric@hawaii.edu
Office +1 808-885-7944

Dr. Roy Gal
Media Contact
+1 808-956-6235
cell: +1 808-388-8690
roygal@hawaii.edu

Source: Institute for Astronomy - University of Hawaii

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