Thursday, November 11, 2021

Near-Earth Asteroid Might be a Lost Fragment of the Moon

 A team of UArizona-led researchers think that the near-Earth asteroid Kamo`oalewa might actually be a miniature moon.

A near-Earth asteroid named Kamo`oalewa could be a fragment of our moon, according to a new paper published in Nature Communications Earth and Environment by a team of astronomers led by the University of Arizona.

Kamo`oalewa is a quasi-satellite – a subcategory of near-Earth asteroids that orbit the sun but remain relatively close to Earth. Little is known about these objects because they are faint and difficult to observe. Kamo`oalewa was discovered by the PanSTARRS telescope in Hawaii in 2016, and the name – found in a Hawaiian creation chant – alludes to an offspring that travels on its own. The asteroid is roughly the size of a Ferris wheel – between 150 and 190 feet in diameter – and gets as close as about 9 million miles from Earth.

Due to its orbit, Kamo`oalewa can only be observed from Earth for a few weeks every April. Its relatively small size means that it can only be seen with one of the largest telescopes on Earth. Using the UArizona-managed Large Binocular Telescope on Mount Graham in southern Arizona, a team of astronomers led by planetary sciences graduate student Ben Sharkey found that Kamo`oalewa's pattern of reflected light, called a spectrum, matches lunar rocks from NASA's Apollo missions, suggesting it originated from the moon.

The team can't yet be sure how it may have broken loose. The reason, in part, is because there are no other known asteroids with lunar origins.

"I looked through every near-Earth asteroid spectrum we had access to, and nothing matched," said Sharkey, the paper's lead author.

The debate over Kamo`oalewa's origins between Sharkey and his adviser, UArizona associate professor Vishnu Reddy, led to another three years of hunting for a plausible explanation.

"We doubted ourselves to death," said Reddy, a co-author who started the project in 2016. After missing the chance to observe it in April 2020 due to a COVID-19 shutdown of the telescope, the team found the final piece of the puzzle in 2021.

"This spring, we got much needed follow-up observations and went, 'Wow it is real,'" Sharkey said. "It's easier to explain with the moon than other ideas."

Kamo`oalewa's orbit is another clue to its lunar origins. Its orbit is similar to the Earth's, but with the slightest tilt. Its orbit is also not typical of near-Earth asteroids, according to study co-author Renu Malhotra, a UArizona planetary sciences professor who led the orbit analysis portion of the study.

"It is very unlikely that a garden-variety near-Earth asteroid would spontaneously move into a quasi-satellite orbit like Kamo`oalewa's," she said. "It will not remain in this particular orbit for very long, only about 300 years in the future, and we estimate that it arrived in this orbit about 500 years ago," Malhotra said. Her lab is working on a paper to further investigate the asteroid's origins.

An artist impression of Earth quasi-satellite Kamo`oalewa near the Earth-Moon system. Astronomers using the Large Binocular Telescope have shown that it might be a lost fragment of the moon.
Credit: Addy Graham/University of Arizona

Kamo`oalewa is about 4 million times fainter than the faintest star the human eye can see in a dark sky.

"These challenging observations were enabled by the immense light gathering power, of the twin 8.4-meter telescopes of the Large Binocular Telescope," said study co-author Al Conrad, a staff scientist with the telescope.

The study also included data from the Lowell Discovery Telescope in Flagstaff, Arizona. Other co-authors on the paper include Olga Kuhn, Christian Veillet, Barry Rothberg and David Thompson from the Large Binocular Telescope; Audrey Thirouin from Lowell Observatory and Juan Sanchez from the Planetary Science Institute in Tucson. The research was funded by NASA's Near-Earth Object Observations Program.

Tuesday, October 26, 2021

Astronomers Discover a Massive Galaxy 'Shipyard' in the Distant Universe

Even galaxies don't like to be alone. While astronomers have known for a while that galaxies tend to congregate in groups and in clusters, the process of going from formation to friend groups has remained an open question in cosmology.

In a paper published in the Astronomy & Astrophysics Journal, an international team of astronomers reports the discovery of objects that appear to be an emerging accumulation of galaxies in the making – known as a protocluster. 

"This discovery is an important step toward reaching our ultimate goal: understanding the assembly of galaxy clusters, the most massive structures that exist in the universe," said Brenda Frye, an associate professor of astronomy at the University of Arizona's Steward Observatory and a co-author of the study. 

To cite a local analog, the Milky Way, the galaxy that is home to our solar system, belongs to a galaxy cluster known as the Local Group, which in turn is a part of the Virgo supercluster.  But what did a supercluster such as Virgo look like 11 billion years ago?  

Want to know more, follow this link!

The pair of LUCI spectrographs, on the LBT, was one of the ground-based instruments used for this work.


Saturday, December 12, 2020

That young but already evolved entirely self-made galaxy

So young and already so evolved: thanks to observations obtained at the Large Binocular Telescope, an international team of researchers coordinated by Paolo Saracco of the Istituto Nazionale di Astrofisica (INAF, Italy) was able to reconstruct the wild evolutionary history of an extremely massive galaxy that existed 12 billions years ago, when the Universe was only 1,8 billions years old, less than 13% of the present age. This galaxy, dubbed C1-23152, formed in "just" 500 million years, an incredibly short time to give rise to a mass of about 200 billion suns. To do so, it produced as many as 450 stars per year, more than one per day, a star formation rate almost 300 times higher than the current rate in our galaxy, the Milky Way.  The information obtained from this study will be fundamental for galaxy formation models for which the nature of objects such as C1-23152 is still difficult to account for.

Color image of the galaxy C1-23152 at redshift z=3.352, when the Universe was 1.8 billion years old. The image is the sum of 3 images at different wavelengths taken with the Hubble Space Telescope.  C1-23152 appears a regular spheroidal galaxy, its light profile matches exactly those of typical elliptical galaxies in the local Universe. Its stellar mass is about 200 billions of stars like sun and it is formed in less than 500 million years.


The most massive galaxies that we observe in the Universe reach masses several hundred billion times that of the Sun and although they are numerically just one third of all galaxies, they contain more than 70% of the stars in the Universe. For this reason, how and how rapidly these galaxies formed are among the most debated questions of modern astrophysics. The current model of galaxy formation - the so-called hierarchical model - predicts that smaller galaxies formed earlier, while more massive systems formed later, through subsequent mergers of the pre-existing smaller galaxies. On the other hand, some of the properties of the most massive galaxies observed in the local Universe, such as the age of their stellar populations, suggest instead that they were formed at early epochs. Unfortunately, the variety of evolutionary phenomena that galaxies can undergo during their lives does not allow us to uniquely define, through studies conducted in the nearby Universe, the way in which they formed, leaving large margins of uncertainty. However, an answer to these questions can come from the study of the properties of massive galaxies in the early Universe, as close as possible to the time when they formed most of their mass.

Seventeen hours of spectroscopic observations with the Large Binocular Telescope (LBT) of the elliptical galaxy C1-23152, previously identified at a distance at which the Universe age was less than 13% of its current age, allowed Saracco’s team to reconstruct its evolutionary history. “The data show that the formation time of C1-23152, that is the time elapsed between the formation of the first stars from the pre-existing gas to the moment when the star formation has almost completely ceased, is less than 500 million of years” says Paolo Saracco, researcher at INAF in Milan and first author of the article published in The Astrophysical Journal. “Also, from the data collected with LBT we were able to establish that in this short time, corresponding to less than 4 hundredths of the age of the Universe, the galaxy formed a mass equal to about 200 billion stars like the Sun, that is about 450 suns per year. Our galaxy, the Milky Way, now forms no more than two a year", adds Danilo Marchesini, full professor at Tufts University and second author of the article. But that is not all. The large amount of information collected allowed the team to quantify for the first time in a galaxy so distant the abundance of chemical elements heavier than helium (the so-called metallicity): the stars of this galaxy have, surprisingly, a higher metallicity than that of the Sun, similar to that observed in the most massive galaxies in the Universe today.

Spectrum of galaxy C1-23152. The top panel shows the atmospheric transmission in the wavelength range of observations. In the middle panel the one-dimensional spectrum of galaxy C1-23152 is shown in the original form (dark-gray curve) and smoothed by a boxcar filter over three pixels (black curve) corresponding to the instrumental resolution. The main absorption and emission lines are marked by solid and dashed lines, respectively. The red curve is the best-fitting composite model obtained with STARLIGHT. The shaded gray regions are those masked in the fitting because of bad sky transmission or the presence of emission lines. For comparison, the bottom panel shows the observed spectrum of a typical post-starburst galaxy in the local Universe selected from the Sloan Digital Sky Survey (SDSS).

“These observations showed that the formation of the most massive galaxies in the Universe can occur extremely quickly, through an extremely intense star formation process in the early Universe, as for C1-23152", underlines Francesco La Barbera, researcher at INAF in Naples, in the team that conducted the study. "Understanding whether the scenario that describes the formation of C1-23152 is a particular case or whether, on the contrary, it is what happens for most of the most massive galaxies in the Universe is of fundamental importance since this would require a profound revision of the galaxy formation models”, adds Adriana Gargiulo, also a researcher at INAF in Milan and co-author of the study.


Likely formation scenario of massive elliptical galaxies like C1-23152. Massive primordial gas clouds, falling in the same region under the effect of gravitational force, collide triggering violent and massive star formation processes. The starburst phase is expected to last few hundreds of million years during which hundreds to thousands stars per year are formed, as for C1-23152. The resulting massive elliptical galaxy will then evolve with time, possibly experiencing different evolutionary phenomena. 

The formation of stellar masses as high as for C1-23152 requires both high masses of gas to convert into stars and particular physical conditions. A possible scenario hypothesized by the researchers is that massive primordial gas clouds, falling under the effect of gravitational force in the same region, collide, triggering violent and massive star formation processes. From the observational point of view, the precursors of the most massive galaxies could therefore be remote galaxies with a very high rate of star formation.

This image shows an example of starburst galaxies forming about a thousand of stars per year at the time of observation. This phase is most likely the formation phase of massive galaxies in the early Universe, like C1-23152.

"To test our hypotheses, the observations that the next generation of instrumentations will allow us to carry out will be decisive, in particular the James Webb Space Telescope (JWST) which will be launched in orbit at the end of 2021, and the Extremely Large Telescope (ELT) the largest ground-based telescope ever built, with a main mirror of 39 meters in diameter, which will be operational in 2026”, concludes Saracco.

Science Contacts:

INAF Press Release     https://www.media.inaf.it/2020/12/10/galassia-vega/

Publication: “The Rapid Build-up of Massive Early-type Galaxies. Supersolar Metallicity, High Velocity Dispersion and Young Age for an ETG at z=3.35”, di Paolo Saracco, Danilo Marchesini, Francesco La Barbera, Adriana Gargiulo, Marianna Annunziatella, Ben Forrest, Daniel J. Lange Vagle, Z. Cemile Marsan, Adam Muzzin, Mauro Stefanon, Gillian Wilson

Thursday, October 1, 2020

The web of the Giant: spectroscopic confirmation of a Large Scale Structure around the z=6.31 quasar SDSS J1030+0524

Using three of the largest telescopes around the world - namely, the Large Binocular Telescope (LBT), the ESO Very Large Telescope (VLT), and the W.M. Keck Observatory Telescope - astronomers found a Large Scale Structure made of six galaxies lying around a massive galaxy harboring a supermassive black hole (SMBH), the first time such a close grouping has been seen within the first billion years of the Universe. The finding helps us better understand how supermassive black holes, one of which exists at the center of our Milky Way, formed and grew to their enormous sizes. It supports the theory that black holes can grow quickly within large web-like structures, which contain plenty of gas to fuel them.

The Large Scale Structure with six galaxies around the Quasar/SMBH (Artist view - Credit: ESO)

“This research was mainly driven by the desire to understand some of the most challenging astronomical objects — supermassive black holes in the early Universe. These are extreme systems and, to date, we have no good explanation for their existence,” says Marco Mignoli, an astronomer at the National Institute for Astrophysics (INAF) in Bologna, Italy and lead-author of the new research published today in Astronomy & Astrophysics Letters.

The new observations revealed multiple galaxies surrounding a supermassive black hole, lying in a cosmic ‘spider web’ of gas and galaxies extending over 300 times the size of the Milky Way. “The cosmic web filaments are like spider-web threads,” explains Mignoli. “The galaxies stand and grow where the filaments cross, and streams of gas — available to fuel the galaxies and the central supermassive black hole — can flow along the filaments”.

Mignoli and his team found this large web-like structure with a black hole of one billion solar masses at a time when the Universe was only 0.9 billion years old. “Our work has placed an important piece in the largely incomplete puzzle that is the formation and growth of such extreme, yet relatively abundant, objects so quickly after the Big Bang,” says co-author Roberto Gilli, also an astronomer at INAF in Bologna.

The very first black holes, thought to have formed from the collapse of the first stars, must have grown very fast to reach masses of a billion Suns within the first 0.9 billion years of the Universe’s life. But astronomers have struggled to explain how sufficiently large amounts of ‘black hole fuel’ could be available to help these objects grow to such enormous sizes in a short time. The newfound structure offers a likely explanation: the large amounts of gas in it provide the fuel the central black hole needs to quickly become a supermassive giant.

But how did such large web-like structures form in the first place? Astronomers think giant halos of mysterious dark matter are key. These large areas of invisible matter are thought to attract huge amounts of gas in the early Universe; together, the gas and invisible matter form the web-like structures where galaxies and black holes can evolve.

“Our finding lends support to the idea that the most distant and massive black holes form and grow within massive dark matter halos in large-scale structures, and that the absence of earlier detections of such structures was likely due to observational limitations,” says Colin Norman of Johns Hopkins University in Baltimore, US, also a co-author on the study.

The galaxies now detected are some of the faintest that current astronomical instruments can observe. This discovery required observations from the largest optical telescopes available. The hunt started eight years ago, when the team - using the superb imaging quality of the Large Binocular Camera (LBC) mounted on the LBT - selected about twenty galaxies with peculiar photometric colors that could be possible neighbors of the central black hole. In the following years, using spectrographs mounted on the LBT Observatory (MODS), the ESO VLT (FORS2), and the Keck Observatory (DEIMOS), the team actually confirmed that six galaxies are located around the black hole.

“We expect to discover further, fainter galaxies around this supermassive black hole. We may have just seen the tip of the iceberg" says co-author Felice Cusano, an astronomer at INAF in Bologna and observer for the LBT-Italy team.

These results contribute to our understanding of how supermassive black holes and large cosmic structures formed and evolved. The future ESO’s Extremely Large Telescope will be able to build on this research by observing higher numbers of fainter galaxies around massive black holes in the early Universe using its powerful spectroscopic instruments.


More Information

This research was presented in the paper “Web of the Giant: Spectroscopic confirmation of a Large Scale Structure around the z=6.31 quasar SDSS J1030+0524” to appear in Astronomy & Astrophysics.

The team is composed of M. Mignoli (INAF, Bologna, Italy), R. Gilli (INAF, Bologna, Italy), R. Decarli (INAF, Bologna, Italy), E. Vanzella (INAF, Bologna, Italy), B. Balmaverde (INAF, Pino Torinese, Italy), N. Cappelluti (Department of physics, University of Miami, Florida, USA), L. Cassarà (INAF, Milano, Italy), A. Comastri (INAF, Bologna, Italy), F. Cusano (INAF, Bologna, Italy), K. Iwasawa (ICCUB, Universitat de Barcelona & ICREA, Barcelona, Spain), S. Marchesi (INAF, Bologna, Italy), I. Prandoni (INAF, Istituto di Radioastronomia, Bologna, Italy), C. Vignali (Dipartimento di Fisica e Astronomia, Università degli Studi di Bologna, Bologna, Italy & INAF, Bologna, Italy), F. Vito (Scuola Normale Superiore, Pisa, Italy), G. Zamorani (INAF, Bologna, Italy), M. Chiaberge (Space Telescope Science Institute, Maryland, USA), C. Norman (Space Telescope Science Institute & Johns Hopkins University, Maryland, USA).

INAF Press Release

Contacts

Marco Mignoli
INAF Bologna
Bologna, Italy
Tel: +39 051 6357 382
Email: marco.mignoli@inaf.it

Roberto Gilli
INAF Bologna
Bologna, Italy
Tel: +39 051 6357 383
Email: roberto.gilli@inaf.it

Barbara Balmaverde
INAF Torino
Pino Torinese, Italy
Email: barbara.balmaverde@inaf.it

Colin Norman
Johns Hopkins University
Baltimore, USA
Email: norman@stsci.edu

Friday, March 6, 2020

Where there's one, there's one hundred more

Although it may have a difficult designation to remember, PSO J030947.49+271757.31, its importance is unique.  It is the most distant Blazar observed to date.  The light we see from it began its journey when the Universe was less than 1 billion years old, almost 13 billion years ago

PSO J0309 + 27 – in short - was discovered by a team of researchers led by Silvia Belladitta, a PhD student at the University of Insubria, working for the Italian National Institute for Astrophysics (INAF) in Milan, under the supervision of Alberto Moretti and Alessandro Caccianiga. While it was suspected that the object was distant, and observations from the Swift Space Telescope (of which INAF is a major contributor) showed its X-ray power matched that of other Blazars, it was the observations obtained with the optical Multi-Double Object Spectrographs (MODS) at the Large Binocular Telescope (LBT) that confirmed it indeed broke the record as the most distant Blazar in the known Universe. 

Blazars are one of the brightest of a class of objects called AGN - or Active Galactic Nuclei - which are supermassive black holes (SMBHs) in the centers of galaxies.  They are active due to the presence of a disk or sphere of ionized gas around them which "fuels" the emission seen at many wavelengths.  Blazars emit powerful relativistic jets bright enough to be seen across the known Universe.  The beam of a Blazar is only visible along a narrow line of sight.  If the Earth is not within that line of sight, it would not be easily recognizable. Thus detecting objects can be extremely difficult (and fortuitous).  But more importantly, this Blazar is one of the earliest, most distant SMBHs seen that is not obscured by dust (unlike most AGN). This allows astronomers to study this object across the entire electromagnetic spectrum and build a complete picture of its properties.

"The spectrum that appeared before our eyes confirmed first that PSO J0309 + 27 is actually an AGN, or a galaxy whose central nucleus is extremely bright due to the presence, in its center, of a supermassive black hole fed by the gas and the stars it engulfs, ”says Belladitta. "In addition, the data obtained by LBT also confirmed that PSO J0309 + 27 is really far away from us using the shift of the color of its light towards red or redshift with a record value of 6.1, never measured before for a similar object," adds Belladitta, first author of the paper describing the discovery, published today in the journal Astronomy & Astrophysics Letters.

PSO J0309 + 27 has therefore proved to be, at the moment, the most powerful persistent radio source in the primordial universe, within the first billion years since its formation. Observations taken by the XRT telescope on board the Swift satellite - a mission with a fundamental contribution by INAF and the Italian Space Agency - have also made it possible to establish that, even in X-rays, PSO J0309 + 27 is the brightest cosmic source ever observed at these distances.

MODS/LBT discovery spectrum of PSO J0309+27 at z=6.10±0.03. The O[VI]λ1033Å, the Ly-αλ1216Å the OIλ1304Å and the CIIλ1336Å lines are marked. The red-dashed line is the quasar template from Vanden Berk et al. (2001) at the redshift of the object for comparison.
Belladitta notes further,  “Observing a blazar is extremely important, for every discovered source of this type, we know that there must be a hundred similar, but oriented differently and therefore too weak to be seen directly". Therefore, the discovery of PSO J0309 + 27 allows astronomers to quantify, for the first time the number of AGN with powerful relativistic jets present in the primordial universe. The Blazars at these early epochs represent the "seeds" for all SMBHs that exist in the Universe today.

“From these new LBT observations, still under development, we also estimate that the central engine that powers PSO J0309 + 27 is a black hole with a mass equal to about a billion times the mass of our Sun. Thanks to our discovery, we are able to say that already in the first billion years of life of the universe, there existed a large number of very massive black holes emitting powerful relativistic jets. This result places tight constraints on the theoretical models that try to explain the origin of these huge black holes in our universe" concludes Belladitta.

Science contact     Silvia Belladitta    silvia.belladitta@inaf.it
Media contact at INAF (Italy)        ufficiostampa@inaf.it
Media contact at LBT (Arizona)    pr_officer@lbto.org

INAF press release: https://www.media.inaf.it/2020/03/06/blazar-da-record/

Publication:
S. Belladitta, A. Moretti, A. Caccianiga, C. Spingola, P. Severgnini, R. Della Ceca, G. Ghisellini, D. Dallacasa, T. Sbarrato, C. Cicone, L. P. Cassarà,  and M. Pedani.    link to the pdf version
A&A 635, L7 (2020) 

Monday, March 2, 2020

Total lunar eclipse: observing the Earth as a transiting planet

Astronomers succeeded in recording sunlight shining through the Earth’s atmosphere in a manner similar to the study of distant exoplanets. During the extraordinary occasion of a lunar eclipse, the Large Binocular Telescope observed the light that was filtered by the Earth’s atmosphere and reflected by the Moon in unique detail. In addition to oxygen and water, atomic spectral lines of sodium, calcium and potassium were detected in our atmosphere in this way first time.

Total lunar eclipse: observing the Earth as a transiting planet
The Sun as seen from the Tycho crater on the Moon during a total lunar eclipse on Earth. When the Sun sets behind the northern Pacific, its disk completely disappears behind Earth. Credit: AIP/Strassmeier/Fohlmeister
When an exoplanet transits in front of its host star, astronomers may be able to record both the dimming of the starlight that the planet blocks and also the starlight that shines through the planet’s atmosphere. While it is only a tiny signal, it contains the imprint of the planet’s chemical and physical signature and provides the principal possibility to measure the planet’s atmospheric constituents. In astrophysics, this technique is called transmission spectroscopy, and is a relatively young technique booming since many exoplanet transits were detected from space. “While, so far, only applicable to super-sized Jupiters, that is oversized Jupiter-like planets orbiting close to their host star, we are most interested in Earth-like planets and whether we could detect more complex molecular signatures in an exo-Earth transmission spectrum possibly even hinting for life”, explains Klaus Strassmeier from the Leibniz Institute for Astrophysics in Potsdam (AIP), the leading author of the now published study. „While not yet doable for any Earth-like exoplanet transit, a total lunar eclipse, which is a total solar eclipse when seen from our own Moon, is nothing else than a transit of our own Earth, and indirectly observable.”

The sunlight that passes through the Earth’s atmosphere before it reaches the Moon and back reflects to Earth is called the Earthshine. The Earth’s atmosphere contains many by-products of biological activity, such as oxygen and ozone in association with water vapor, methane and carbon dioxide. These biogenic molecules present attractive narrow molecular bands at optical and near infrared wavelengths for detection in atmospheres of other planets. Taking the Earth as the prototype of a habitable planet, Earthshine observations provide the possibility to verify biogenic and related chemical elemental presence with the same techniques that otherwise are being used for observing stars with super Jupiter planets. Earthshine is thus an ideal test case for future exo-Earth detections with the new generation of extremely large telescopes.

January 2019 featured a total lunar eclipse. The Moon dimmed by a factor of 20,000 during totality which is the reason why the light gathering capability of the 11.8 m Large Binocular Telescope (LBT) in Arizona was needed for the observations. Additionally, the high spectral resolution of the Potsdam Echelle Polarimetric and Spectroscopic Instrument (PEPSI) was necessary to separate the expected tiny spectral-line absorptions of the Earth’s atmosphere from the normal solar spectrum at unprecedented spectral resolution and in polarized light.

“PEPSI has already made significant contributions to the study of exoplanets through the observation of their transit in front of their sun.” adds Christian Veillet, LBT Observatory's Director. “Looking at the Earth as an exoplanet thanks to a total lunar eclipse well-suited to LBT's location in Arizona, and adding polarimetry to the exquisite resolution of the PEPSI spectrograph, resulted in the detection of sodium, calcium, and potassium in Earth's atmosphere."
Snapshot spectra of terrestrial molecular oxygen and water vapor absorption. Intensity is plotted versus wavelength in Angstroem. Time increases from bottom up as indicated in UT hh:mm:ss. Immediately noticeable is the dramatic increase of O2 and H2O absorption during eclipse (central four spectra) with respect to outside eclipse (other spectra). Oxygen molecules create the so-called A-band at 7600 Å, H2O is seen as myriads of individual absorption lines in the range 7850–9100 Å. Credit: AIP/Strassmeier. 
Detailed look at the wavelengths around the potassium line at 7699 Å. Time increases bottom up and is again indicated as UT. The bottom spectrum is a comparison spectrum of the full moon outside of eclipse. Red color denotes times of totality, black times of partiality, and blue out of eclipse. Note that the spectral lines flanking the potassium line are from two terrestrial water vapor absorptions. Credit: AIP/Strassmeier.



More information on PEPSI and the LBT: https://pepsi.aip.de | http://www.lbto.org


Science contact: 
        Prof. Dr. Klaus G. Strassmeier, 0331-7499-223, kstrassmeier@aip.de

Media contacts: 
        Dr. Janine Fohlmeister (Potsdam, Germany)  0331-7499-803, presse@aip.de
        Dr. Christian Veillet (Tucson, USA)   1-520-349-4576, pr_officer@lbto.org



Publication:

Klaus G. Strassmeier, Ilya Ilyin, Engin Keles, Matthias Mallonn, Arto Järvinen, Michael Weber, Felix Mackebrandt, and John M. Hill, 2020, Astronomy & Astrophysics, in press


Friday, September 27, 2019

Found: Three Black Holes on Collision Course


A team of astronomers, led by Graduate Student Ryan Pfeifle of George Mason University (GMU) in Fairfax Virginia, used observations spanning the electro-magnetic spectrum to provide the strongest evidence to-date of the existence of three Active Galactic Nuclei (AGN) residing in a merging galaxy.  

Beginning with a sample of hundreds of likely merging galaxies identified by the Galaxy Zoo Citizen Science Program and using thermal infrared observations from NASA's Wide-field Infrared Survey Explorer (WISE), Pfeifle and his team identified a few dozen candidate systems which were thought to host two Active Galactic Nuclei (AGN).   AGN are supermassive black holes at least 1 million times more massive than our Sun which are energized by the presence of vast quantities of gas drawn into them by gravitational forces. 

Space-based X-ray observations obtained with the Chandra Observatory Nuclear Spectroscopic Telescope Array (NuStar) found evidence to support the presence of two AGN in most of the merging galaxies.  However, one system appeared to be significantly more unusual than the rest, SDSS J084905.51+111447.2 (shortened to SDSS J0849+1114). Here, the team found X-ray evidence to suggest three AGN resided in this merging galaxy.

In order to provide more definitive support, and rule out competing astrophysical explanations, the team turned to the Large Binocular Telescope Observatory (LBT), currently the world's largest optical/infrared telescope.  Led by Dr. Barry Rothberg, who is a staff astronomer at LBT and holds a concurrent affiliate faculty position at GMU, optical and infrared spectroscopic observations of SDSS J0849+1114 were obtained using the Multi-Object Double Spectrographs (MODS), and the LBT Utility Camera in the Infrared (LUCIs).

The spectroscopic observations allow optical and near-infrared light to be separated so that atomic and molecular species can be identified.  The MODS and LUCI LBT observations conclusively demonstrated the presence of atomic species which can only exist in conditions found in AGN, as well as the presence of fast flowing gas that could only be powered by these monsters.  Moreover, the spectroscopic data allowed the team to determine the ages of the stars in the host galaxy, further ruling out competing astrophysical explanations for the presence of the three X-ray detections.  

Recent work by the team has expanded their study of this object to radio wavelengths.  "The use of multi-wavelength space- and ground-based observatories shows the synergies needed to discover such unusual, but important astrophysical phenomenon.  There is no way we could have confirmed the existence of a Triple AGN without contributions from all of these observatories," says Dr Rothberg.

However, the team's work is far from finished.  Pfiefile notes that the team's new multi-wavelength technique will allow them to extend their work to finding more triples.  "We already have more candidates that we are actively pursuing. I look forward to LBT once again demonstrating its importance in finding the optical and near-infrared signatures that either confirm or reject the presence of AGN in merging galaxies."


More details on the findings here with pictures and videos here.