GTC (Gran Telescopio Canarias)
GTC (Gran Telescopio Canarias) - Observatorio del Roque de los Muchachos La Palma
GTC is an ambitious Spanish project with the aim of constructing and operating one of the largest and most advanced telescopes in the world. With the leadership of the Instituto de Astrofísica de Canarias (IAC), its First Light Ceremony was celebrated in the early morning of 14th July, 2007. Scientific production of the telescope started in March of 2009, once the telescope optics and its control system was sufficiently well developed, and the first science instrument, OSIRIS, had been installed. 1)
The Observatorios de Canarias (OOCC), which consists of the Observatorio del Roque de los Muchachos (ORM) on La Palma and the Observatorio del Teide (OT) on Tenerife, contain jointly the telescopes and instruments of about 60 institutions from more than 20 countries. These are the most important collection of observational facilities for optical and infrared astrophysics inside the EU. Other experiments for high-energy astrophysics and the study of the cosmic microwave background complete the battery of facilities available. The excellent astronomical quality of the sky over the Canary Islands – comprehensively characterized and protected by Law – makes these observatories an ‘astronomy reserve’ that has been opened by Spain to the international scientific community since the establishment of the International Treaty on Cooperation in Astrophysics in 1979.
In 1994, the public limited company GRANTECAN, S.A. was founded with the aim to design and construct the Gran Telescopio CANARIAS, or GTC. This company was supported by both the Local Government from the Canary Islands and the Spanish Government. GTC also has an international recognition through the agreements signed with the Mexican Government to participate in the project through the Instituto de Astronomía de la Instituto de Astronomía de la Universidad Nacional Autónoma de México y del Instituto Nacional de Astrofísica, Óptica y Electrónica de Puebla. In addition, participation from the United States is through collaboration with the University of Florida.
The ultimate aim of the GTC is to facilitate world-class science observations. Being the largest telescope in the world and thanks to its location at the Roque de los Muchachos Observatory, the telescope will allow the study of key questions in astrophysics such as the nature of black holes, the formation history of stars and galaxies in the early universe, the physics of distant planets around other stars, and the nature of dark matter and dark energy in the universe.
At Roque de los Muchachos Observatory (ORM), on the rim of the Taburiente National Park, at 2396 meters above sea level in the municipality of Garafía (La Palma) stands one of the largest arrays of telescopes in the world. 2)
Because of the sky above La Palma, this observatory enjoys exceptional conditions for astronomical research, for this reason, it continues to attract giant telescopes of the future, as well as the new generation of Cherenkov telescopes, designed to study the Universe in very high energy gamma rays.
The site currently hosts the largest optical-infrared telescope in the world, along with twenty other telescopes and instruments for various kinds of studies, including nocturnal observations, robotic observing, solar physics, and high energy astrophysics.
Great advances in the study of the Universe have been made with these telescopes, ranging from the detection of the most distant galaxy to confirmation of the existence of black holes and the accelerated expansion of the Universe.
Aside from its scientific activities, the Instituto de Astrofísica de Canarias carries out numerous outreach tasks in an effort to ensure that astronomical knowledge reaches the public at large. For this purpose, at various times of the year school and group visits are arranged to its observing facilities at Roque de los Muchachos Observatory and Teide Observatory.
The Roque de los Muchachos Observatory Residence has a number of facilities (diurnal and nocturnal dormitories, kitchen, dining room, reception, lounges, games, etc.) to fulfil the needs of all the scientific and technical staff link to the Observatory.
Geographic coordinates of GTC : Latitude: 28°45'22" N, Longitude: 17°53'31" W.
The GTC is currently the largest and one of the most advanced optical and infra-red telescopes in the world. Its primary mirror consists of 36 individual hexagonal segments that together act as a single mirror. The light collecting mirror surface area of GTC is equivalent to that of a telescope with a 10.4 m diameter single monolithic mirror. Thanks to its huge collecting area and advanced engineering the GTC classes amongst the best performing telescopes for astronomical research.
The GTC has also a secondary mirror and a tertiary mirror that together with the primary mirror produce the telescope focal plane in the focal station of choice. The scientific instruments that are placed in the focal station then analyze and detect the light, and store the final data.
Figure 1: The telescope mount is a large mechanical steel structure that holds the mirrors, allows rotational movements of the telescope along a horizontal and vertical axis. This movement has to be extremely precise in order to keep the stars projected stably onto the detector. The telescope is designed so that it is able to observe the optical and infrared light ranges (image credit: IAC)
GTC is the largest telescope thanks to its huge light collecting surface of 75.7 m2 (73 m2 effective area). Apart from its large collecting surface another key feature is the exquisite image quality that the telescope delivers and therefore it can exploit the good sky quality to its maximum. The good image quality is made possible thanks to the active adjustment of the optics. This active optics allows the alignment, deformation and movement the individual segments that form the primary mirror, as well as the alignment of the secondary mirror so as to always keep their optimal position independently of the external conditions (climate, temperature, gravity, manufacture faults, etc...).
In the future GTC will also make use of a technique called "adaptive optics" that will allow the telescope to correct for atmospheric turbulence and hence reach the best possible imaging performance possible, opening up new frontiers for science. For all large telescopes the Earth's atmosphere disturbs the light and degrades the image quality drastically, but thanks to adaptive optics this negative effect can be counteracted by applying very fast corrections in real time (some 1000 times per second) making use of a deformable mirror. This is a very demanding technique, but the improvements in image quality and thus for science, are important.
Observing with GTC
The telescope itself is enclosed by a dome that protects it from the elements. At the same time the dome is designed to minimize the turbulence of the air close to the telescope. When an observing night commences than first the dome is opened, allowing the light from the stars to strike the telescope.
Control of the telescope and the instruments is done remotely from the control room and highly automated. The available observing time is a valuable commodity. To optimize its use, the observations are scheduled in a way that optimizes the use of the telescope according to the prevailing sky conditions. This so-called queue-schedule observing implies that many programs are simultaneously active and executed according to their scientific priority and taking into account their requirements in terms of observing conditions.
The GTC also makes use of an advanced control system and has a high reliability of operation through a preventive maintenance program designed to locate potential malfunctions before they occur, ensuring that downtime caused by these failures in the system are kept to a minimum.
Table 1: GTC parameters
Figure 2: Roque de los Muchachos Observatory. At the edge of the Caldera de Taburiente National Park, at 2,400 meters above sea level, on the island of La Palma, there are some of the best telescopes in the world, among them the Gran Telescopio Canarias (GTC), image credit: IAC
GTC started its operational phase with its first scientific observations on March 16th, 2009. Gradually, as the telescope and the instrumentation suite developed, more time is being dedicated to scientific activities.
News and events
• November 24, 2021: A team of researchers at the Instituto de Astrofísica de Canarias (IAC) and the Instituto Nacional de Astrofísica, Óptica y Electrónica (INAOE), Mexico, has discovered lithium in the oldest and coldest brown dwarf where the presence of this valuable element has been confirmed so far. This substellar object, called Reid 1B, preserves intact the earliest known lithium deposit in our cosmic neighborhood, dating back to a time before the formation of the binary system to which it belongs. The discovery was made using the OSIRIS spectrograph on the Gran Telescopio Canarias (GTC), at the Roque de los Muchachos Observatory (Garafía, La Palma), in the Canary Islands. The study has just been published in the journal Monthly Notices of the Royal Astronomical Society. 3) 4) 5)
Figure 3: Comparison between different objects, showing the different levels of preservation and destruction of lithium [image credit: Gabriel Pérez Díaz, SMM (IAC)]
- Brown dwarfs, also known as “coffee colored dwarfs” or “failed stars” are the natural link between stars and planets. They are more massive than Jupiter but now sufficiently to burn hydrogen, which is the fuel the stars use to shine. For that reason these substellar objects were not observed until observers detected them in the mid 1990’s. They are particularly interesting because it was predicted that some of them could preserve intact their content of lithium, sometimes known as “white petroleum” because of its rarity and its relevance.
- In the past twenty years astronomers have detected, and followed the orbital motions of binaries formed by brown dwarfs in the solar neighborhood. They have determined their masses dynamically using Kepler’s laws, the mathematical formulae produced in the XVII century by Johannes Kepler to describe the motions of astronomical bodies moving under the effects of their mutual gravitation, such as the system formed by the Earth and the Sun. In some of these systems the primary component has a mass sufficient to burn lithium while the secondary may not have this mass. However until now the theoretical models had not been put to the test.
- Using the OSIRIS spectrograph on the Gran Telescopio Canarias (GTC, or Grantecan) currently the largest optical and infrared telescope in the world, at the Roque de los Muchachos Observatory (ORM), a team of researchers at the Instituto de Astrofísica de Canarias (IAC) and the Instituto Nacional de Astrofísica, Óptica y Electrónica (INAOE) made high sensitivity spectroscopic observations, between February and August this year, of two binaries whose components are brown dwarfs.
- They did not detect lithium in three of them, but they did find it in Reid 1B, the faintest and coolest of the four. Doing this they made a remarkable discovery, a deposit of cosmic lithium which is not destroyed, whose origin dates back before the formation of the system to which Reid 1B belongs. It is, in fact, the coolest, faintest extrasolar object where lithium has been found, in a quantity 13 thousand times greater than the amount there is on Earth. This object, which has an age of 1.100 million years, and a dynamical mass 41 times bigger than that of Jupiter (the largest planet in the Solar System), is 16.9 light years away from us.
A chest of hidden treasure
- Observations of lithium in brown dwarfs allow us to estimate their masses with a degree of accuracy, based on nuclear reactions. The thermonuclear masses found this way must be consistent with the dynamical masses found, with less uncertainty, from orbital analysis. However the researchers have found that the lithium is preserved up to a dynamical mass which is 10% lower than that predicted by the most recent theoretical models. This discrepancy seems to be significant, and suggests that there is something in the behavior of brown dwarfs that we still don’t understand.
- “We have been following the trail of lithium in brown dwarfs for three decades” says Eduardo Lorenzo Martín Guerrero de Escalante, Research Professor of the Higher Council for Scientific Research (CSIC) at the IAC who is the first author of the article, “and finally we have been able to make a precise determination of the boundary in mass between its preservation and its destruction, and compare this with the theoretical predictions". The researcher adds that "there are thousands of millions of brown dwarfs in the Milky Way. The lithium contained in brown dwarfs is the largest known deposit of this valuable element in our cosmic neighborhood”.
- Carlos del Burgo Díaz co-author of the article, a researcher at the INAOE, a public research center of the Mexican CONACYT, explains that “although primordial lithium was created 13.800 million years ago, together with hydrogen and helium, as a result of he nuclear reactions in the primordial fireball of the Big Bang, now there is as much as four times more lithium in the Universe”. According to this researcher “although this element can be destroyed, it is also created in explosive events such as novae and supernovae, so that brown dwarfs such as Reid 1B can wrap it up and protect it as if it was a chest of hidden treasure”.
- This research has been financed by funding from the Spanish Ministry of Economic Affairs and Digital Transformation (MINECO) and by the European Fund for Regional Developomente (FEDER) via project PID2019-109522GB-C53.
- The Gran Telescopio Canarias, and the Observatories of the Instituto de Astrofísica de Canarias (IAC) are part of the network of Singular Scientific and Technical Infrastructures (ICTS) of Spain.
• July 6, 2021: Historically most scientists thought that once a satellite galaxy has passed close by its higher mass parent galaxy its star formation would stop because the larger galaxy would remove the gas from it, leaving it shorn of the material it would need to make new stars. However, for the first time, a team led by the researcher at the Instituto de Astrofísica de Canarias (IAC), Arianna di Cintio, has shown using numerical simulations that this is not always the case. The results of the study were recently published in the journal Monthly Notices of the Royal Astronomical Society (MNRAS). 6)
- Using sophisticated simulations of the whole of the Local Group of galaxies, including the Milky Way, the Andromeda galaxy and their respective satellite galaxies, the researchers have shown that the satellites not only can retain their gas but can also experience many new episodes of star formation just after passing close to the pericenter of their parent galaxy (the minimum distance they reach from its center).
- The satellite galaxies of the Local Group show a wide variety of star formation histories, whose origin has not previously been fully understood. Using hydrodynamic simulations within the project Constrained Local UniversE (CLUES) the authors studied the star formation histories of satellite galaxies similar to those of the Milky Way in a cosmological context.
- While in the majority of the cases the gas of the satellite is sucked out by the parent galaxy due to gravitational action and transfers itself to the larger galaxy, interrupting star formation in the satellite, in a process known as accretion; in some 25% of the sample they found that star formation was clearly enhanced by this interactive process.
Figure 4: Image of the simulated local group used for the article. Left, image of dark matter; on the right, gas distribution. The three main galaxies of the Local Group (MW, M31 and M33) are indicated (image credit: CLUES simulation team)
- The results show that the peaks of star formation are correlated with the close pass of the satellite around the parent galaxy, and occasionally by the interaction of two satellites. The researchers identified two key features to the star formation: the satellite must enter the parent galaxy with a large reserve of cold gas, and a minimum distance not too small, so that stars may form due to compression of the gas. On the contrary, galaxies which pass too close to the parent galaxy, or to a parent galaxy with little gas, are stripped of their gas and thereby lose the possibility of forming new stars.
- “The passage of satellites also coincide with peaks in the star formation of their parent galaxies, which suggests that this mechanism causes bursts of stars equally in both parent galaxies and satellites, in agreement with recent studies of the history of star formation in our own Galaxy”, explains Arianna di Cintio, the lead author on the paper. 7)
- “This is very important when we try to understand how star formation is produced in the smaller dwarf galaxies of our Local Group, an unresolved question”, she adds.
- This finding will shed light on the episodes of star formation which are observed in the dwarf galaxies of the Local Group, such as Carina and Fornax, giving an attractive explanation of their existence. It also requires a revision of the theoretical models used to explain the formation of stars in dwarf galaxies.
• November 22, 2021: A white dwarf star that completes a full rotation once every 25 seconds is the fastest spinning confirmed white dwarf, according to a team of astronomers led by the University of Warwick. 8)
Figure 5: Artist impression of LAMOST J024048.51+195226.9, the fastest spinning confirmed white dwarf and only second ever magnetic propeller known. Material is being pulled from the companion and flung into space at high speed. A small fraction of it is accreted, gathering in bright spots that rotate in and out of view, which allowed the detection of the rotation period (image credit: University of Warwick/Mark Garlick)
- They have established the spin period of the star for the first time, confirming it as an extremely rare example of a magnetic propeller system: the white dwarf is pulling gaseous plasma from a nearby companion star and flinging it into space at around 3000 km/s.
- Reported today (22 November) in the journal Monthly Notices of the Royal Astronomical Society: Letters, it is only the second magnetic propeller white dwarf to have been identified in over seventy years thanks to a combination of powerful and sensitive instruments that allowed scientists to catch a glimpse of the speeding star. 9)
- The study was led by the University of Warwick with the University of Sheffield, and funded by the Science and Technology Facilities Council (STFC), part of UK Research and Innovation, and the Leverhulme Trust.
- A white dwarf is a star that has burnt up all of its fuel and shed its outer layers, now undergoing a process of shrinking and cooling over millions of years. The star that the Warwick team observed, named LAMOST J024048.51+195226.9 – or J0240+1952 for short, is the size of the Earth but is thought to be at least 200,000 times more massive. It is part of a binary star system and its immense gravity is pulling material from its larger companion star in the form of plasma.
- In the past, this plasma was falling onto the white dwarf’s equator at high speed, providing the energy that has given it this dizzyingly fast spin. Put into context, one rotation of the planet Earth takes 24 hours, while the equivalent on J0240+1952 is a mere 25 seconds. That’s almost 20% faster than the confirmed white dwarf with the most comparable spin rate, which completes a rotation in just over 29 seconds.
- However, at some point in its evolutionary history J0240+1952 developed a strong magnetic field. The magnetic field acts a protective barrier, causing most of the falling plasma to be propelled away from the white dwarf. The remainder will flow towards the star’s magnetic poles. It gathers in bright spots on the surface of the star and as these rotate in and out of view they cause pulsations in the light that the astronomers observe from Earth, which they then used to measure the rotation of the entire star.
- Lead author Dr Ingrid Pelisoli of the University of Warwick Department of Physics said: “J0240+1952 will have completed several rotations in the short amount of time that people take to read about it, it is really incredible. The rotation is so fast that the white dwarf must have an above average mass just to stay together and not be torn apart.
- “It is pulling material from its companion star due to its gravitational effect, but as that gets closer to the white dwarf the magnetic field starts to dominate. This type of gas is highly conducting and picks up a lot of speed from this process, which propels it away from the star and out into space.”
- J0240+1952 is one of only two stars with this magnetic propeller system discovered in over past seventy years. Although material being flung out of the star was first observed in 2020, astronomers had not been able to confirm the presence of a rapid spin that is a main ingredient of a magnetic propeller, as the pulsations are too fast and dim for other telescopes to observe.
- To visualise the star at that speed for the first time, the University of Warwick team used the highly sensitive HiPERCAM instrument, jointly operated by Warwick and the University of Sheffield with funding from the European Research Council. This was specially mounted on the largest functioning optical telescope in the world, the 10 m diameter Gran Telescopio Canarias (GTC) in La Palma, to capture as much light as possible.
- “These kinds of studies are possible thanks to the unique combination of the fast imaging capability of HiPERCAM with the largest collecting area in the world provided by GTC,” said Antonio Cabrera, Head of GTC Science Operations.
- Co-author Professor Tom Marsh from the University of Warwick Department of Physics adds: “It’s only the second time that we have found one of these magnetic propeller systems, so we now know it’s not a unique occurrence. It establishes that the magnetic propeller mechanism is a generic property that operates in these binaries, if the circumstances are right.
- Co-author Professor Tom Marsh from the University of Warwick Department of Physics adds: “It’s only the second time that we have found one of these magnetic propeller systems, so we now know it’s not a unique occurrence. It establishes that the magnetic propeller mechanism is a generic property that operates in these binaries, if the circumstances are right.
- “The second discovery is almost as important as the first as you develop a model for the first and with the second you can test it to see if that model works. This latest discovery has shown that the model works really well, it predicted that the star had to be spinning fast, and indeed it does.”
• October 21, 2021: One of the most interesting questions for astrophysicists for the past few decades is how and when did the first galaxies form. One of the possible answers to “how” is that star formation in the first galaxies took place at a steady rate, building up a system with increasing mass. Another possibility is that the formation was more violent and discontinuous, with intense bursts of star formation, on short timescales, triggered by events such as galaxy mergers and strong concentrations of gas. 10)
- An international research team, led from the Centre of Astrobiology (CAB, CSIC-INTA) with participation from the Instituto de Astrofísica de Canarias (IAC), in collaboration with researchers form the United Kingdom, Mexico and Chile, have investigated the origin of the first stars and structures in the Universe. They analyzed data from the Frontier Fields program, the most ambitious project carried out with the Hubble Space Telescope (HST) and the Gran Telescope Can arias (GTC or GRANTECAN), the largest optical and infrared telescope in the world, sited at the Roque de los Muchachos Observatory (Garafía, La Palma). The results are published today in the journal Monthly Notices of the Royal Astronomical Society (MNRAS). 11)
- “The first galaxies might have added new stars slowly but continually, without much acceleration, systematically converting gas into relatively small stars over long periods of time. Or the formation could have been in bursts, with short periods of formation producing very big stars, which could shape the whole galaxy and cause it to stop its activity for a while or permanently”, explains Pablo G. Pérez-González, a researcher at the CAB, a co-author of the article, and leader of the international collaboration working on the study. “Each of the scenarios is linked to different processes, such as the mergers of galaxies or the influence of supermassive black holes, and have an effect on when and how different elements were formed, such as carbon and oxygen, which are essential for life”, he adds.
Figure 6: Image of the galaxy cluster Abell 370, one of the regions of the sky observed in the SHARDS Frontier Fields project. This is the deepest image ever taken to detect galaxies with emission lines, which are actively forming stars (image credit: GTC or GRANTECAN)
- In an article published recently about this subject, the astronomers looked for nearby analogues to the first galaxies formed in the Universe so that they could study them in much greater detail. Alex Griffiths, a researcher at Nottingham University and first author on the paper says: “Until we have the new James Webb Space Telescope we will not be able to observe the first galaxies formed in the Universe, they are too faint. So we look for similar objects in the nearby Universe and we analyze them with the most powerful telescopes we have at present”.
- The way this work was done was to combine the power of the most advanced telescopes, such as the HST and the GTC, with the help of “natural telescopes”. Chris Conselice, a co-author of the article, and supervisor of the doctoral thesis of Griffiths, comments on this strategy: “Some galaxies are found in large groups, which we call clusters, which contain a large amount of matter in the form of stars, but also in the form of gas and of dark matter. This mass is so big, that it can curve space-time, and the clusters act as “natural telescopes”. These, known as gravitational lenses, let us observe distant, faint galaxies more brightly and with better spatial resolution, it is as if we were using a lens created by the Universe itself”. Observations of some of these clusters acting as gravitational telescopes are the basis of the Frontier Fields project, the most ambitious program of the Hubble Space Telescope.
Figure 7: This image compares the center of the cluster as seen with the GTC (left) and with the Hubble Space Telescope (right). The data from the HST have better spatial resolution because they are not affected by the turbulence in the atmosphere. The data from the GTC are even deeper, showing the existence of some galaxies previously unknown and not detected by the HST (image credit: GTC/HST)
- In the study published in MNRAS the authors combined the power of gravitational lensing by some of the most massive clusters in the Universe with very deep images from the GTC taken in the SHARDS project (Survey for high-z Red and Dead Sources) with the aim of finding and studying some of the smallest and faintest galaxies in the local Universe.
- The SHARDS project consisted in taking with the GTC the very deepest images of the field observed with the Hubble, using 25 intermediate passband filters which together cover the wavelength range from 500 to 940 nanometers. “These selective images allow us to analyze how the light of very faint galaxies is distributed in the different colors of the visible wavelength range. And this allows us to detect the gas heated by newly formed stars, which emit at specific wavelengths (emission lines) in a process similar to that in a neon lamp”, explains Romano Corradi, the director of GTC/GRANTECAN.
- “To obtain these images the SHARDS project needed 120 hours of observation with the GTC. The images, which can be combined into a single very impressive image in pseudo color, are a real mine of information about the thousands of galaxies detected”, stresses Antonio Cabrera, head of Scientific Operations of GRANTECAN.
- “Our main result is that the start of galaxy formation is irregular, with very violent periods of star formation followed by periods when the galaxy is dormant”, adds Griffiths. “It is not likely that galaxy mergers played a major role in triggering those bursts of star formation; it is more probable that this was due to other causes which caused the pile-up of gas, we need to investigate further”, he concluded.
- The Gran Telescopio Canarias and the Observatories of the Instituto de Astrofísica de Canarias (IAC) are part of the network of Singular Scientific and Technical Infrastructures of Spain.
• August 23, 2021: After twelve years of a very successful operation at GTC, OSIRIS was definitely removed from Nasmyth-B focal station on August 23, 2021. This was the first step in the instrument migration to Cassegrain focus, that is expected to be completed before the end of the year, with the on-sky commissioning currently scheduled for January 2022. 12)
Figure 8: The OSIRIS instrument, once dismounted from Nasmyth-B focal station, is being transferred to GTC lab (image credit: IAC)
- In the coming months, some maintenance works and preparation activities will be conducted inside the instrument, to make this ready for the operation at its new location. OSIRIS has been the workhorse instrument of GTC for years (nearly 80% of the scientific data produced so far with GTC were obtained with OSIRIS), so this activity has been carefully planned and all the possible risks have been properly mitigated in order to make the instrument available to the users as soon as possible.
• July 26, 2021: On 26 August 2020, NASA's Fermi space telescope detected a pulse of high-energy radiation that, with a duration of only one second, broke a record: it was the shortest gamma-ray burst (GRB) caused by the death of a massive star ever seen. Its study, in which the Institute of Astrophysics of Andalusia (IAA-CSIC) participates, shows that the classification of these bursts according to their duration does not entirely correspond to reality and opens up new scenarios in the death of stars. 13)
Figure 9: The massive star that barely shone upon death (image credit: IAA-CSIC)
- GRBs are the most energetic phenomena in the universe, detectable even if they occur in galaxies billions of light years away. They are classified as short or long depending on whether the event lasts longer than two seconds, and their duration is associated with their origin: long bursts occur with the death of massive stars, while short bursts have been linked to the merger of two compact objects, such as neutron stars.
- "We already knew that some GRBs produced by massive stars could be recorded as short GRBs, but we thought that this was due to instrumental limitations", says Bin-bin Zhang, from Nanjing University (China) and the University of Nevada, Las Vegas. This outburst is special because it is a short GRB, but its properties point to a collapsing star as the origin: we now know that dying stars can also produce short outbursts”.
- Named GRB 200826A after the date it occurred, this outburst is the subject of two papers published today in Nature Astronomy. The first, led by Zhang, explores the gamma-ray data. The second, led by Tomás Ahumada of the University of Maryland and NASA's Goddard Space Flight Center, describes the fading of the GRB's multiwavelength glow and the emerging light from the supernova explosion that followed.
- “We think this event was effectively a fizzle, one that was close to not happening at all,” Ahumada said. “Even so, the burst emitted 14 million times the energy released by the entire Milky Way galaxy over the same amount of time, making it one of the most energetic short-duration GRBs ever seen.”
Massive Stars Also Produce Short GRBs When Dying
- When a very massive star exhausts its hydrogen fuel, its core collapses and a black hole forms. As matter swirls around the black hole, some of it escapes through two powerful jets that rush outward at almost the speed of light in opposite directions. Each jet pierces the star, producing a gamma-ray signal that can last for up to several minutes, while the jet moves away and interacts with the surrounding gas. After the outburst, the star's envelope rapidly expands into a supernova. A GRB is only detected when one of these jets happens to point almost directly toward Earth.
Figure 10: Artist's conception of the formation of a black hole after the collapse of the star's core (central black dot) and the launch of two jets that pass through the envelope and produce, if the alignment is correct, a GRB [image credit: Goddard Space Flight Center (NASA)]
- The groups behind the two papers propose different scenarios to explain this strange outburst. For example, GRB 200826A could have been driven by jets that barely left the star before going out, rather than the more typical case where jets emerge from the star and travel long distances to produce a long-lived outburst.
- “This outburst could even belong to a class of short GRBs involving new scenarios, such as the merger of a normal star and a neutron star, or magnetic bubbles induced by differential rotation (different rotation speeds of the equator and the poles of a star) as a mechanism for producing gamma-ray emissions –says Alberto Castro-Tirado, a researcher at the IAA-CSIC who participates in the two publications–. More generally, this result clearly shows that the duration of an outburst does not indicate its origin”.
Figure 11: The jet at the time of passing through the star after forming the black hole in the center of it [image credit: Goddard Space Flight Center (NASA)]
Multiple Observations From Space And From The Ground
- The GRB 200826A constituted a strong high-energy explosion that was detected by the Fermi space telescope, as well as the Wind mission (NASA), Mars Odyssey (NASA) and the INTEGRAL satellite of the European Space Agency (ESA), participating in a GRBs location system called Interplanetary Network (IPN). Since the burst reaches each detector at different times, any pair of them can be used to narrow down where in the sky it occurred. About seventeen hours after the GRB, the IPN narrowed it down to a relatively small area of the sky in the Andromeda constellation.
- Using the Palomar Observatory's Zwicky Transient Facility (ZTF), the team scanned the sky for changes in visible light that could be related to the GRB's afterglow fading. Of the more than 28,000 ZTF alerts from the first night, only one met all the search criteria. One day after the blast, X-ray emission was found in the same region and two days later in radio waves. Thanks to measurements with the Gran Telescopio Canarias (La Palma), the team showed that the light from the GRB had taken 6.6 billion years to reach us (this represents 48% of the current age of the universe, which is 13.8 billion years).
- But to show that this brief burst came from a collapsing star, it was necessary to also capture the glow of the emerging supernova. Observations with the Gemini North telescope made it possible to detect, starting 28 days after the explosion, a source in the near infrared: the supernova.
• July 7, 2021: MIRADAS, the next-generation near-infrared multi-object spectrograph for the GTC, which is being developed by a consortium led by the University of Florida, has obtained its Laboratory First Light on July 7th 2021 in Gainesville. While the instrument is not yet in its final configuration and there is work ahead, it is an important accomplishment and milestone for the project, as the instrument prepares for its shipment to La Palma within the next few months, when it will be integrated and commissioned at the GTC, in collaboration with GRANTECAN staff. 14)
- This first light happened coinciding and despite the passage of the tropical storm Elsa, and is the result of years of hard work from an international team of engineers and scientists to make MIRADAS a reality. Professor Steve Eikenberry, the principal investigator of MIRADAS, highlighted the importance of this achievement: "Our team here at the University of Florida, along with our collaborators at the Instituto de Astrofisica de Canarias and the University of Barcelona, are very pleased to have reached this important milestone of the first full system cooldown of MIRADAS. While we still have a number of tasks ahead of us, the system performance so far is excellent, and we look forward to bringing MIRADAS to the GTC soon!"
Figure 12: Laboratory First Light spectrum of MIRADAS, using a 1064nm laser (image credit: IAC)
- Even though, this first image was saturated (the calibration light source was too bright), it demonstrated that all the different subsystems were working correctly and were ready for further adjustments and tests. Some other images are shown below:
Figure 13: Left: Non-saturated image of an Argon lamp line through the optical fiber. Right: the extracted 1D spectrum showing the different emission lines produced by the arc lamp (image credit: IAC)
- MIRADAS has been co-financed by the European Regional Development Fund (ERDF), within the framework of the "Programa Operativo FEDER CANARIAS 2014-2020", project "Ampliación del equipamiento del Gran Telescopio de Canarias, Fase 2" and within the framework "Programa Operativo Plurirregional de España 2014-2020", project "Mejora de la ICTS Gran Telescopio CANARIAS (2016-2020)".
Figure 14: The Echellogram using the cross-dispersion grating (for the highest spectral resolution and coverage) of a continuum source (image credit: IAC)
• June 9, 2021: Fast radio bursts (FRBs) are one of the greatest mysteries of modern astronomy. These are highly intense pulses of radio emissions coming from far away distances and last only a few thousandths of a second. Despite the fact that over 500 FRBs have been detected to date, their origins remain a mystery, owing to a small sample of FRBs with known host galaxies. Therefore, identifying the host galaxy of FRBs is critical. Moreover, in order to resolve the FRB origin conundrum and test different proposed models of their origin, Local Universe FRBs are specially important. Moreover, since some FRBs repeat, finding repeating FRBs in the Local Universe would make their multi-wavelength follow-up studies feasible, and hence, finding nearby repeating FRBs is extremely useful. 15)
- In the study led by Mohit Bhardwaj, a PhD student at McGill University and a member of the Canadian Hydrogen Intensity Mapping Experiment (CHIME) / FRB team, in collaboration with Dr. Aida Kirichenko at the National Autonomous University of Mexico (UNAM) and Dr. Divakara Mayya at the National Institute of Astrophysics, Optics and Electronics (INAOE) in Mexico, the authors have identified the host of a nearby repeating FRB 20181030A. The FRB was first reported by the CHIME/FRB collaboration in 2019. The authors used the Director's Discretionary Time of the GTC and conclusively showed that the FRB source is located within our home supercluster, Laniakea, at a distance of 65 million light years in a galaxy, NGC 3252. This makes FRB 20181030A the second closest extragalactic FRB localized to date! NGC 3252 is a spiral galaxy like our own Milky Way which is actively converting its gas into stars. It is yet to be conclusively shown if such galaxies preferentially host FRBs.
- One of the popular proposed models to explain FRBs invokes fast spinning highly magnetized young neutron stars that are thought to be remnants of some of the Universe's most powerful explosions. However, the authors showed that the occurrence rate of such catastrophic events is significantly low to explain the observed number of repeating FRBs found in the Local Universe. This suggests that we might need multiple FRB channels to form FRB sources. As the number of nearby FRBs with known hosts grows, it will be possible to understand the nature of FRB progenitors.
Figure 15: The ellipse shows the boundary within which the FRB emission originated. The GTC was used to obtain the redshifts of the 7 marked sources, which enabled the authors to identify the source#4, a spiral galaxy known as NGC 3252, as the only candidate within the maximum allowed distance to the FRB source, and also to study the star formation and chemical abundance of this galaxy (image credit: IAC)
- Association of a repeating FRB with NGC 3252 is a very promising result for another reason. As the host galaxy is practically in our backyard, it is an excellent target for multi-wavelength follow-up observations, especially in X-rays and gamma-rays where the telescopes have limited sensitivity to detect proposed FRB counterparts. Although challenging, detection of multi-wavelength counterparts of FRBs will be a monumental step towards understanding the origin of these perplexing cosmic phenomena.
- The results of the study were announced in the press release at the 238th American Astronomical Society Meeting on June 9, 2021, and the paper will appear in Astrophysical Journal Letters. 16)
• June 7, 2021: An international team of scientists led from the Centre for Astrobiology (CAB, CSIC-INTA), with participation from the Instituto de Astrofísica de Canarias (IAC), has used the Gran Telescopio Canarias (GTC) to study a representative sample of galaxies, both disc and spheroidal, in a deep sky zone in the constellation of the Great Bear to characterize the properties of the stellar populations of galactic bulges. The researchers have been able to determine the mode of formation and development of these galactic structures. The results of this study were recently published in The Astrophysical Journal. 17) 18)
Figure 16: An example of a nearby spiral galaxy, M81, where the bulge and the disc are easily identified (image credit: NASA/JPL-Caltech/ESA/Harvard-Smithsonian CfA)
- The researchers focused their study on massive disc and spheroidal galaxies, using imaging data from the Hubble Space Telescope and spectroscopic data from the SHARDS (Survey for High-z Absorption Red and Dead Sources) project, a program of observations over the complete GOODS-N (Great Observatories Origins Deep Survey – North) region through 25 different filters taken with the OSIRIS instrument on the Gran Telescopio Canarias (GTC), the largest optical and infrared telescope in the world, at the Roque de los Muchachos Observatory (Garafía, La Palma, Canary Islands).
- Analysis of the data allowed the researchers to discover something unexpected: the bulges of the disc galaxies were formed in two waves. One third of the bulges in disc galaxies were formed at redshift 6.2, which corresponds to an early epoch in the Universe, when it was only 5% of its present age, around 900 million years old. “These bulges are the relics of the first structures formed in the Universe, which we have found hidden in local disc galaxies”, explains Luca Costantin, a researcher at the CAB within a program of Attracting Talent of the Community of Madrid, and the first author on the paper.
- But in contrast, almost two thirds of the bulges observed show a mean value of redshift of around 1.3, which means that they were formed much more recently, corresponding to an age of four thousand million years, or almost 35% of the age of the Universe.
Figure 17: Images of some of the galaxies studied in the present work, much further away and fainter, so that studying their structures is more complex and is possible only with very precise data provided by the GTC and Hubble. The galaxy on the left, and the central one are two disc galaxies, while the one on the right is spheroidal. (image credit: Luca Costantin, et al.)
- A peculiar characteristic which permits the distinction between the two waves is that the central bulges of the first wave, the older bulges, are more compact and dense than those formed in the second, more recent wave. In addition, the data from the spheroidal galaxies in the sample show a mean redshift value of 1.1, which suggests that they formed in the same general time as the bulges of the second wave.
- For Jairo Méndez Abreu, a researcher at the University of Granada (UGR) and a co-author of the article, who was formerly a Severo Ochoa postdoctoral researcher at the IAC, “the idea behind the technique used to observe the stars in the central bulge is fairly simple, but it has not been possible to apply it until the recent development of methods which have allowed us to separate the light from the stars in the central bulge from those in the disc, to be specific the GASP2D and C2D algorithms, which we have developed recently and which have enabled us to achieve unprecedented accuracy”.
- Another important result of the study is that the two waves of bulge formation differ not only in terms of the ages of their stars, but also in terms of their star formation rates. The data indicate that the stars in the bulges of the first wave formed quickly, on timescales of typically 200 million year. On the contrary, a significant fraction of the stars in the bulges of the second wave required formation times five times longer, some thousand million years.
- “We have found that the Universe has two ways of forming the central zones of galaxies like our own: starting early and performing very quickly, or taking time to start, but finally forming a large number of stars in what we know as the bulge”, comments Pablo G. Pérez González, a researcher at the CAB, and Principal Investigator of the SHARDS project, which gave essential data for this study. In the words of Antonio Cabrera, the Head of Science Operations at the GTC, “SHARDS is a perfect example of what is possible due to the combination of the huge collecting capacity of the GTC and the extraordinary conditions at the Roque de los Muchachos Observatory, to produce 180 hours of data with such excellent image quality, essential for the detection of the objects analyzed here”.
Figure 18: Image of the deep sky study by the Hubble Space Telescope, called GOODS-N (Great Observatories Origins Deep Survey - North) [image credit: NASA, ESA, G. Illingworth (University of California, Santa Cruz), P. Oesch (University of California, Santa Cruz; Yale University), R. Bouwens and I. Labbé (Leiden University), and the scientific team]
- As described by Paola Dimauro, a researcher at the National Observatory of Brazil and a co-author of this article, “this study has allowed us to explore the morphological evolution and the history of the assembly of the structural components of the galaxies, analogous to archaeological studies, analyzing the information encoded in the millions of stars of each galaxy. The interesting point was to find that not all the structures were formed at the same time, or in the same way”.
- The results of this study have allowed the observers to establish a curious parallel between the formation and the evolution through time of the disc galaxies studies and the creation and development of a large city during the centuries. Just as we find that some large cities have historic centers, which are older and house the oldest buildings in cluttered narrow streets, the results of this work suggest that some of the centers of massive disc galaxies harbor some of the oldest spheroids formed in the Universe, which have continued to acquire material, forming discs more slowly, the new city outskirts in our analogy.
- The Gran Telescopio Canarias and the Observatories of the Instituto de Astrofísica de Canarias (IAC) form part of the network of Singular Scientific and Technical Infrastructures (ICTS) of Spain.
• March 10, 2021: All stars with a mass less than eight times that of the Sun will end their lives as planetary nebulae, formed by a central star -the "bare" core of the star after the expulsion of its outer layers- surrounded by a fluorescent envelope. These nebulae can have spherical, bipolar or highly complex shapes and, although it is still unknown why one shape or another develops, the indications point to the participation of bipolar jets of material launched by the action of a companion star. A group of astronomers led by the IAA-CSIC has traced the bipolar jet of the planetary nebula NGC 2392 to its central star, thus demonstrating that the jet launch process is still active. 19) 20)
Figure 19: Thanks to MEGARA instrument of the Gran Telescopio Canarias, researchers from the Institute of Astrophysics of Andalusia (IAA-CSIC) have observed and analyzed the jet of NGC 2392, which points to the existence of a companion star (image credit: IAA-CSIC)
- After exhausting their fuel, low and intermediate mass stars shed their outer layers, forming an envelope of ionized gas around a white dwarf star: a planetary nebula. "Until just a couple of decades ago it was believed that the morphologies of planetary nebulae were due to the interaction of stellar winds launched in two different evolutionary phases, a model that did not explain the asymmetric or multipolar forms of some of them -points out Martín A. Guerrero, researcher at the Institute of Astrophysics of Andalusia (IAA-CSIC) who is leading the study-. Now we know that very fast and collimated jets of material, which are formed at the end of the star's life, could interact with the envelope expelled in previous stages and draw different morphologies”.
- The origin of this paradigm shift dates back to the mid-1980s, when what was called a high-speed “bipolar flow” was discovered precisely in NGC 2392, the nebula object of this study, and which represented the first indication of a jet of material in a planetary nebula. And, although the speed of the material could even be measured, the brightness of the nebula (especially the inner shell) made it impossible to obtain a direct image of the jet.
Figure 20: Today we have a technique known as integral field spectroscopy, capable of resolving previously unattainable details and used by state-of-the-art instruments such as MEGARA, which operates at the Gran Telescopio Canarias (GTC). "The extraordinary tomographic capacity of MEGARA has allowed us to separate the terribly weak emission of the jet from the bright nebular emission," says Sara Cazzoli, a researcher at the Institute of Astrophysics of Andalusia (IAA-CSIC) who is participating in the work (image credit: IAA-CSIC)
- Thus, almost four decades after the discovery of the jet in NGC 2392, researchers have discovered that it consists of two large globules (and some fainter nodules) emerging from the central star and extending beyond the outer shell of the nebula. The material in the jet shows a velocity of about 206 km/s, an age of about 2600 years and a linear size twice that of the nebula itself.
- According to the results, the jet passes through the inner bright shell and, since the jet and the shell show similar speeds, everything indicates that it is the jet that accelerates the gas of the shell and shapes it, and not the weak stellar wind of the star. Furthermore, the MEGARA 3D tomography of the jet reveals that it is currently being collimated, unlike the fossil jets, already inactive, detected in other evolved planetary nebulae.
- “Finally, this work supports a result that we obtained in 2019 and that analyzed the high-energy X-rays emanating from the central star. These provide indirect evidence for the existence of an invisible companion revolving around the central star. In this scenario, the jet would emerge from the companion star, quite possibly another white dwarf, and the X-ray emission of an accretion disk around the latter”, concludes Martín A. Guerrero (IAA-CSIC).
• February 26, 2021: A study, led by researchers at the Instituto de Astrofísica de Canarias (IAC) and carried out with OSIRIS, an instrument on the Gran Telescopio Canarias (GTC), has found the most densely populated galaxy cluster in formation in the primitive universe. The researchers predict that this structure, which is at a distance of 12.5 billion light years from us, will have evolved becoming a cluster similar to that of Virgo, a neighbor of the Local Group of galaxies to which the Milky Way belongs. The study is published in the specialized journal Monthly Notices of the Royal Astronomical Society (MNRAS). 21) 22)
- Clusters of galaxies are groups of galaxies which remain together because of the action of gravity. To understand the evolution of these “cities of galaxies” scientists look for structures in formation, the so-called galaxy protoclusters, in the early universe.
- In 2012 an international team of astronomers made an accurate determination of the distance of the galaxy HDF850.1, known as one of the galaxies with the highest rate of star formation in the observable universe. To their surprise, the scientists also discovered that this galaxy, which is one of the most studied regions on the sky, known as the Hubble Deep Field/GOODS-North, is part of a group of around a dozen protogalaxies which had formed during the first thousand million years of cosmic history. Before its discovery only one other similar primordial group was known.
- Now, thanks to a new piece of research with the OSIRIS instrument on the Gran Telescopio Canarias (GTC, or GRANTECAN), the team has shown that it is one of the most densely populated regions populated with galaxies in the primitive Universe, and have for the first time carried out a detailed study of the physical properties of this system. ”Surprisingly we have discovered that all the members of the cluster studied up to now, around two dozen, are galaxies with normal star formation, and that the central galaxy appears to dominate the production of stars in this structure” explains Rosa Calvi, formerly a postdoctoral researcher at the IAC and first author of the article.
Witnesses to the infancy of the local Universe
- This recent study shows that this cluster of galaxies in formation is made up of various components, or “zones” with differences in their evolution. The astronomers predict that this structure will change gradually until it becomes a galaxy cluster similar to Virgo, the central region of the supercluster of the same name in which is situated the Local Group of galaxies to which the Milky Way belongs. “We see this city in construction just as it was 12,500 million years ago, when the Universe had less than 10% of its present age, so we are seeing the childhood of a cluster of galaxies like those which are typical in the local Universe” notes Helmut Dannerbauer, an IAC researcher who is co-author of this article.
- The distance measured to these studied sources agrees perfectly with the predictions based on photometric observations taken previously on GRANTECAN by Pablo Arrabal Haro, formerly a doctoral student at the IAC, supervised by José Miguel Rodríguez Espinosa, an IAC researcher and Assistant General Secretary of the International Astronomical Union (IAU), and Casiana Muñoz-Tuñón, a researcher and Deputy Director of the IAC, all of them co-authors of the present article. Arrabal developed a method for selecting galaxies with normal star formation rates, based on the photometric survey SHARDS (Survey for High-z Absorption Red and Dead Sources), a Large Program of the European Southern Observatory (ESO) carried out on the GTC. “I am very happy to see that the method developed during my doctoral thesis works so well in finding and confirming a region highly populated with galaxies in the distant Universe” states Arrabal.
- The SHARDS program has been led by Pablo Pérez-González, researcher at the Centro de Astrobiología (CAB, CSIC-INTA) and also author of the paper. As Pérez-González explains, "measuring exactly how these structures are forming, especially at the beginning of the Universe, is not easy, and we need exceptional data such as those we are taking with the GTC telescope as part of the SHARDS and SHARDS Frontier Fields projects, which allow us to determine distances to galaxies and between galaxies at the edge of the Universe with a precision never achieved before."
Figure 21: Image of the studied galaxy cluster in formation, 12.5 billion light years from us. The circles indicate the new members discovered with the GTC; 4 of them are shown in detail (image credit: NASA/ESA/GOODS-N+3DHST+CANDELS Team/Daniel López/IAC)
- In addition, Stefan Geier, GTC support astronomer and co-author of the paper points out that “this highly surprising result would not have been possible without the extraordinary capacity of OSIRIS together with the large collecting area of the GRANTECAN, the largest optical and infrared telescope in the world."
- The Gran Telescopio Canarias and the Observatories of the Instituto de Astrofísica de Canarias (IAC) are part of the network of Singular Scientific and Technical Infrastructures of Spain.
Figure 22: Photo of the GTC (Gran Telescopio Canarias), Photo credit: Daniel López/IAC
• November 26, 2020: The small fraction of dark matter in the galaxy NGC1052-DF4 has worried the astronomical community for several years. Now a team of researchers from the Instituto de Astrofísica de Canarias (IAAC) the University of La Laguna (ULL) the University of New South Wales, the Insituto de Astrofísica de Andalucia, and NASA’S Ames Research Center have found a mechnism which can esplain it. This finding, which is to be published in the scientific journal The Astrophysical Journal, manages to make this phenomenon fit with accepted models of formation and evolution of galaxies. 23)
- Astronomers were not able to explain the lack of dark matter in the galaxy NGC1052-DF4 without violating accepted cosmological models. While in this type of ancient galaxies the stella mass usually makes up only 1% of the dark matter, in this case it had been observed that dark matter is less than 50% of the mass. But finally the mystery has been solved.
- The astronomers have detected strong changes in the distribution of the material in NGC1052-DF4 due to tides caused by the interaction of a massive neighbouring galaxy: NGC1935.
- According to this study, massive galactic systems can interact gravitationally with their neighbour galaxies, changing their structure strongly, and even destroying them.
- These forces first affect the dark matter “because the stars are more concentrated and are affected later, when almost all the dark matter has been eliminated” explains Mireia Montes, an astrophysicist who took her doctorate at the IAC, and who has led the research from the University of New South Wales, in Australia.
- What we observe is similar to what occurs on Earth due to the Moon’s graviational pull. “The mechanism was known previously but it had not been observed in this type of galaxies where the stellar density is extremely low” notes Ignacio Trujillo, an astrophysicist at the IAC and one of the authors of the article.
- “And this is just what this study has managed to do “to detect characteristics which are 1000 times fainter than the night sky visible from the ground, in galaxies which are 65 million lihg years away” adds Trujillo.
- This type of research is known as “Low surface brightness science” and to obtain the images those involved have made a very careful observation with the Hubble Space Telescope, the Gran Telescopio Canarias (GTC) at the Roque de los Muchachos Observatory (Garafía, La Palma) and at the IAC-80 telescope, at the Teide Observatory (Izaña, Tenerife). But no in the traditional way.
- Although astronomers usually work with exposure times of order half an hour, this work needed images with 60 hours of exposre which is “pretty complicated” we are assured by Raúl Infante-Sainz, who specializes in low surface brightness regions, and is another of those involved at the IAC. As well as needing these very long time exposures needed to reach the very low stellar surface densities, afterwards “we need to reduce the data satisfactorily so as to obtain the low surface brightness structures which are hidden below the noise levels in the original images.
- This very careful research explains the relative absence of dark matter in NGC1052-DF4, and in a way which is consistent with the models of formation and evolution of galaxies which are most widely accepated in the international astronomical community. 24)
Figure 23: This image presents the region around the galaxy NGC 1052-DF4, taken by the IAC80 telescope at the Teide Observatory. The figure highlights the main galaxies in the field-of-view, including NGC 1052-DF4 (center), and its neighbor NGC 1035 (center left), image credit: IAC
• October 27, 2020: An international team of astronomers has identified one of the rarest known classes of gamma-ray emitting galaxies, called BL Lacertae, within the first 2 billion years of the age of the Universe. The team, that has used one of the largest optical telescope in the world, Gran Telescopio Canarias (GTC), located at the Observatorio del Roque de los Muchachos (Garafía, La Palma), consists of researchers from the Universidad Complutense de Madrid (UCM, Spain), DESY (Germany), University of California Riverside and Clemson University (USA). The finding is published in The Astrophysical Journal Letters. 25) 26)
- Only a small fraction of the galaxies emits gamma rays, which is the most extreme form of light. Astronomers believe that these highly energetic photons originate from the vicinity of a supermassive black hole residing at the centers of these galaxies. When this happens, they are known as active galaxies. The black hole swallows matter from its surroundings and emits jets or, in other words, collimated streams of matter and radiation. Few of these active galaxies (less than 1%) have their jets pointing by chance toward Earth. Scientists call them blazars and are one of the most powerful sources of radiation in the universe.
- Blazars come in two flavors: BL Lacertae (BL Lac) and flat-spectrum radio-quasars (FSRQs). Our current understanding about these mysterious astronomical objects is that FSRQs are relatively young active galaxies, rich in dust and gas that surround the central black hole. As time passes, the amount of matter available to feed the black hole is consumed and the FSRQ evolves to become a BL Lac object. "In other words, BL Lacs may represent the elderly and evolved phase of a blazar's life, while FSRQs resemble an adult," explains Vaidehi Paliya, a DESY researcher who participated in this program.
- Now, the team of international scientists has discovered a new BL Lac object, named 4FGL J1219.0+3653, much farther away than the previous record holder. "We have discovered a BL Lac existing even 800 million years earlier, this is when the Universe was less than 2 billion years old," states Cristina Cabello, a graduate student at IPARCOS-UCM. "This finding challenges the current scenario that BL Lacs are actually an evolved phase of FSRQ," adds Nicolás Cardiel, a professor at IPARCOS-UCM. Jesús Gallego, also a professor at the same institution and a co-author of the study concludes: “This discovery has challenged our knowledge of the cosmic evolution of blazars and active galaxies in general.”
- The researchers have used the OSIRIS and EMIR instruments, designed and built by the Instituto de Astrofísica de Canarias (IAC) and mounted on GTC, also known as Grantecan. "These results are a clear example of how the combination of the large collecting area of GTC, the world's largest optical-infrared telescope, together with the unique capabilities of complementary instruments installed in the telescope are providing breakthrough results to improve our understanding of the Universe,” underlines Romano Corradi, director of Grantecan.
- The Observatories of the Instituto de Astrofísica de Canarias (IAC) are part of the network of Singular Scientific and Technical Infrastructures (ICTS) of Spain.
Figure 24: Artist's impression of a blazar, a rare class of active galaxy characterized by a relativistic jet that is pointing in the general direction of the Earth (image credit: M. Weiss/CfA)
• In January 2020, the equipment for the Main Cassegrain Focal Station has been received at GTC. This component, developed by the basque company IDOM, has been produced thanks to funds and support from both Spanish and Canary Governments (this latter through European Regional Development Funds), and was shipped to GTC once it successfully passed the corresponding factory acceptance tests on December 2019. 27)
- With this component, that includes an instrument rotator and an adquisition & guiding system, all the current available focal stations at the telescope are ready for the installation of different instruments. This enhances the scientific capabilities of the telescope in order to continue producing high level science in the upcoming decade. In fact, instrumentation plan of the telescope already includes the migration of OSIRIS instrument, -the first light instrument in operation since 2009-, to this new focal station on early 2021.
Figure 25: IDOM and Grantecan staff during factory acceptance tests at IDOM (Bilbao) on December 2019.
Figure 26: Arrival of Main Cassegrain Focal Station at GTC in January 2020. (image credit: IAC)
GTC instruments (OSIRIS, EMIR, MEGARA)
A defining aspect of the scientific success of any telescope installation is its ability to deliver cutting-edge data through novel instrumentation. An exciting and extensive instrumentation development program exists for GTC. The telescope can currently host up to two instruments for its Nasmyth foci. Further instruments may be installed in the two folded-Cassegrain foci that are currently being prepared, and ultimately also in the main Cassegrain focus. 28)
The first two instruments were delivered to GTC to populate the Nasmyth-A and -B focal stations. The very first instrument for scientific use was OSIRIS, which started operation when the telescope commenced its scientific life, in March 2009. OSIRIS works in the optical wavelength range and can be used for high-quality imaging and longs-slit as well as multi-object spectroscopy. The arrival of GTCAO by mid-2022 will occupy the Nasmyth-B focal station and will move OSIRIS to Cassegrain focus some time before (estimated by late-2021).
The second instrument CanariCam came on-line in 2012, after a long period of preparing the telescope for it (in particular the chopping motion of the secondary mirror and achieving getting the primary mirror segments in phase). CanariCam is a thermal infrared camera and spectrograph with polarimetry and coronography capabilities. CanariCam was in operation up to April 2016, when it was removed from the Nasmyth A focus to be placed in one of the Folded Cass focal stations later, or share it with another instrument. After a productive period of operation at Folded Cass-E between 2019 and 2020, CanariCam was finally decommissioned in February 2021.
OSIRIS (Optical System for Imaging and low-Intermediate-Resolution Integrated Spectroscopy)
OSIRIS is an imager and spectrograph for the optical wavelength range, located in the Nasmyth-B focus of GTC. Apart from the standard broad-band imaging and long-slit spectroscopy, it provides additional capabilities such as the narrow-band tunable filters imaging, charge-shuffling and multi-object spectroscopy. 29)
OSIRIS covers the wavelength range from 0.365 to 1.05 µm with a total field of view of 7.8 x 8.5 arcmin (7.8 x 7.8 arcmin unvignetted), and 7.5 x 6.0 arcmin, for direct imaging and multi-object spectroscopy respectively. The OSIRIS User Manual can be found here.
Table 2: Summary of the available modes and features for imaging and spectroscopic observations with OSIRIS
Table 3: Overview of OSIRIS instrument features
EMIR (Espectrógrafo Multiobjeto Infra-rojo) — Multi-object Infrared Spectrograph)
EMIR is the first second-generation GTC instrument to enter regular operations in 2017. It is a near-infrared (0.9 - 2.5 µm) wide-field imager and medium-resolution multi-object spectrograph installed at the Nasmyth-A focal station. The center piece of the instrument is the CSU (Configurable Slit Unit) allowing to configure and observe in real time up to 55 slits over the 4' x 6.67' spectroscopic field of view. Long slits with different dimensions could be configured as well. The disperser elements are formed by combining high-quality diffraction gratings, manufactured by photo-resistive procedures with large conventional prisms. In imaging mode the 6.67' x 6.67' field of view could be observed through 11 narrow and broad-band filters (including the standard 2MASS JHKs). The detector is a 2048 x 2048 Teledyne HAWAII-2 HgCdTe near-infrared optimized chip with a pixel scale in imaging mode 0.2"/pixel. 30)
The EMIR project is led by the IAC with the participation of the Laboratoire d'Astrophysique - Observatoire Midi-Pyrenees (France), Universidad Complutense de Madrid and the Laboratoire d'Astrophysique - Observatoire de Marselle (France).
Table 4: EMIR instrument features
Figure 27: Illustration of the instrument optics (image credit: IAC)
Figure 28: EMIR attached to the Nasmyth A focal station of the GTC telescope (image credit: IAC)
EMIR is equipped with a HAWAII-2 IR detector manufactured by Teledyne. It is a HgCdTe array of 2048 x 2048 pixels (18 µm square each), operating between 0.9 and 2.5 µm and optimized for the K-band atmospheric transmission window (~ 2.1 µm) at cryogenic temperatures. The detector is divided into 4 quadrants (1024 x 1024 pixels each). Individual quadrants are read out through 8 channels, permitting a full frame rate of slightly over one frame per second. The read out of the 32 channels is performed simultaneously. The following table summarize some detector parameters of interest.
Table 5: EMIR detector specification
MEGARA (Multi-Espectrógrafo en GTC de Alta Resolución para Astronomía)
MEGARA is an optical integral-field Unit (IFU) and multi-object spectrograph (MOS) designed for the GTC. The MEGARA IFU mode will offer a fiber bundle covering 12.5 arcsec x 11.3 arcsec with a spaxel size of 0.62 arcsec, which makes use of 100 µm-core optical fibers. The MEGARA MOS will allow observing up to 100 objects in a region of 3.5 arcmin x 3.5 arcmin around the IFU bundle. Eight of these bundles will be devoted to the determination of the sky during the observation with the IFU, so only 92 of these positioners will be available for MOS observations. Both the IFU and MOS capabilities of MEGARA will provide intermediate-to-high spectral resolutions (R~5,500, 12,000 and 20,000 respectively for the LR, MR and HR modes).
Figure 29: An infographic of the PseudoSlit, Collimator, dispersion elements (VPHs) on the wheel and the set Cryostat+Camera (image credit: IAC)
Figure 30: Left: MEGARA focal plane component attached to the Folded-Cass F focal station of GTC. Right: MEGARA spectrograph at the Nasmyth-A focal station (image credit: IAC)
MEGARA has two different bundles of fibers distribution: the Large Compact Bundle IFU and the Multi-Object Spectrograph (MOS) mode.
With MEGARA, spatially spread individual targets could be observed in MOS mode, as well as compact or extended targets with fiber-limited spatial resolution in the center of the instrument (IFU mode).
In table 6 we provide a summary of the main characteristics of the two MEGARA modes (IFU and MOS) and the corresponding spectral resolutions yield for each set of VPHs. Also, the current VPHs available in MEGARA can be found here.
Figure 31 shows the distribution of the VPHs in the resolving power versus wavelength coverage plane for all MEGARA VPHs in the case of the 100 µm-core fibers (LCB IFU and MOS modes) when theoretically projected at designing stage (in different colors) and black/grey after empirical estimates at lab. Average resolutions at midpoint of range are above expectations.
Figure 32: Current timeline for GTC instruments in the period 2018-2024 (image credit: IAC)
MIRADAS (Mid-resolution InfRAreD Astronomical Spectrograph)
MIRADAS is an intermediate resolution infrared spectrograph for the GTC telescope. It will operate in the infrared range of 1 to 2.5 µm with a spectral resolution of 20,000. It is a multi-object spectrograph capable of observing up to 20 objects simultaneously, by means of a robot with 20 arms that can patrol a 5 arcminutes field. As of 2021, NIRPS is indevelopment.
Apart from the scientific matters, the IAC contribution is focused in the development of the instrument control system, where other institutions are also participating. MIRADAS follows the GTC control system standards, assuring a total integration with the telescope. The control system is based in a distributed architecture, according to the component model of GTC, developed in C++ and running in different computers by means of the CORBA middleware.
The consortium is lead by the University of Florida (USA) with the participation of Universidad de Barcelona (UB), Universidad Complutense de Madrid (UCM), Instituto de Astrofísica de Canarias (IAC), Institut de Física d’Altes Energies (IFAE) and Institut d’Estudis Espacials de Catalunya (IEEC, as technical support to UB). Additionally, several individual researchers from the Universidad Nacional Autónoma de México (UNAM) are also participating.
Figure 33: Layour of the MIRADAS instrument (image credit: IAC)
HiPERCAM is a portable, quintuple-beam optical imager that saw first light on the 10.4-m Gran Telescopio Canarias (GTC) in 2018. The instrument uses re-imaging optics and 4 dichroic beamsplitters to record us gs rs is zs (320 -1060 nm) images simultaneously on its five CCD cameras, each of 3.1 arcmin (diagonal) field of view. The detectors in HiPERCAM are frame-transfer devices cooled thermo-electrically to 183 K, thereby allowing both long-exposure, deep imaging of faint targets, as well as high-speed (over 1000 windowed frames per second) imaging of rapidly varying targets. A comparison-star pick-off system in the telescope focal plane increases the effective field of view to 6.7 arcmin for differential photometry. Combining HiPERCAM with the world’s largest optical telescope enables the detection of astronomical sources to gs ~23 in 1 s and gs ~28 in 1 h. In this paper we describe the scientific motivation behind HiPERCAM, present its design, report on its measured performance, and outline some planned enhancements. 31)
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The information compiled and edited in this article was provided by Herbert J. Kramer from his documentation of: ”Observation of the Earth and Its Environment: Survey of Missions and Sensors” (Springer Verlag) as well as many other sources after the publication of the 4th edition in 2002. - Comments and corrections to this article are always welcome for further updates (firstname.lastname@example.org).