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