LAM wishes you a happy new year 2025, with, for the first time, an interactive card: https://doc.lam.fr/carte_de_voeux/2025/
English
End-of-year celebration at LAM: review of projects, retreats and festivities
On Friday 13th, LAM staff were invited to a series of presentations on four projects in which LAM is involved and which have reached or will soon reach operation: Euclid, PFS, SVOM-Colibri, and the CASAA-Saat nanosat to be launched on December 26 (more on that here)! The day was also an opportunity to celebrate the retirement of Pascal Landerecthe and Françoise Maxant, and to celebrate the end of the year.
The LAM wishes you happy holidays too!
Discovery of molecular gas in the giant galaxy Malin 1 for the first time.
In a study accepted in “The Astrophysical Journal”, an international team including several LAM researchers report the detection, for the first time, of molecular gas in the Malin 1 galaxy. Malin 1, discovered in the 1980s by David Malin, lies just 366 Mega-Parsec away and is as massive as our galaxy. It is the largest galactic disk (over 200 kiloparsec in diameter). Its late discovery is due to the fact that this extended disk is also very faint, because the galaxy is “diffuse”, with low densities. It had been established that stars form in this giant diffuse disk, but despite several attempts, molecular gas had never been detected. This has now been achieved thanks to Alma, which has made it possible to measure its density in the central part without any doubt (see illustration). Previous attempts had failed because, relative to the size of the galaxy, only a small fraction of it is detected. Alma’s resolution therefore played an important role in this detection. Malin 1 has recently been the subject of renewed interest thanks to instrumental advances that allow us to study diffuse galaxies, such as ALMA for CO, or recently MUSE for ionized gas (Johnson et al. 2024, Junais et al. 2024). The authors received a message from David Malin himself following this publication! The team is now looking forward to successful observations on JWST…
Cracking a Comet Cold Case: Rediscovering Blue Comet C/1908 R1 (Morehouse)
A century-old mystery has been solved by an international collaboration including researchers from LAM (Sarah Anderson), UTINAM institute, and the STAR Institute. By reanalyzing historical plates from the Meudon Observatory with modern tools, scientists have revealed that comet C/1908 R1 (Morehouse) shares unique compositional features with the unusual blue comet C/2016 R2 (PanSTARRS). This rare combination of high N2+ and CO+ levels and low dust content, along with periodic tail disruptions linked to solar activity, has positioned Morehouse as the first comet of its kind, predating C/2016 R2 by over a century.
Reference: Anderson et al. “A Comparative Study of the Blue Comets C/1908 R1 (Morehouse) and C/2016 R2 (PanSTARRs)”,
Laboratory General Assembly on Nov 13
On November 13, LAM director Stéphane Arnouts presented a progress report on the laboratory’s current mandate, in particular its objectives, with contributions to three major projects in the discipline, as recognized in recent INSU and CNES forecasts: HARMONI, MOSAIC and PRIMA. Many other aspects of laboratory life were also discussed, including an update on psycho-social risks which is about to be launched, arrivals, departures and forthcoming events, as well as a presentation of new arrivals.
A look back at the 2024 “Fête de la science”
For this year’s fête de la science, the laboratory was involved in the CNRS’s unusual tours. On Wednesday 9, we welcomed two groups who were able to admire the polishing workshop, see a comet nucleus in 3D, and enter the LAM’s large integration hall. On Friday, we were able to reach a large school audience on the stand at the Marseille science festival (on the old port), where on Saturday and Sunday, visitors from the general public passed by our stand. More than 10,000 visitors came to see us! We also answered children’s questions as part of the ‘Dis-Moi-Pourquoi’ operation organised by the newspaper ‘La Marseillaise’. Finally, we were present on Friday and Sunday at the ‘Femmes et Sciences’ stand.
Opening of the “La science taille XX’Elles” exhibition at the LAM
LAM staff were invited to the opening of the ‘La science taille XX’Elles’ exhibition, created by the CNRS and the Femmes et Sciences association to showcase women scientists from local research laboratories. The inauguration was attended by Annie Zavagno, a member of the laboratory featured in the exhibition, and was an opportunity to stress the importance for everyone of a fair representation of the diversity present in the laboratory, and of being concerned about related issues. It was also an opportunity to get together over a cup of coffee and start new discussions.
LAM participation in the science festival “fête de la science”
Each year, LAM staff take part in the “Fête de la Science” (national science festival). A lucky few will be able to take one of the CNRS’s unusual tours to discover how we are trying to unravel the mysteries of the universe at Chateau-Gombert:
https://visitesinsolites.cnrs.fr/visite/comment-percer-les-mysteres-de-lunivers/
For the rest of you, visit our stand at the Marseille Science Village on October 12 and 13. Our experts in all fields (solar system, exoplanets, instrumentation for astronomy, galaxies, stars, cosmology) will be on hand to answer (almost) all your questions.
https://www.fetedelascience.fr/decouvrir-l-univers-du-systeme-solaire-la-cosmologie-avec-le-lam-2
You’re sure to see other LAM staff at other events, and in the media… As with other LAM public events, you can find them in the LAM public calendar: https://www.lam.fr/events/list/?tribe_eventcategory%5B0%5D=236
Happy fête de la science!
The influence of Ganymede’s magnetosphere observed in its auroral footprint on Jupiter
Jupiter exhibits the brightest auroras in the Solar System. One of the peculiarities of this planet, which it shares with Saturn, is that it also possesses auroral emissions caused by three of its largest moons: Io, Europa, and Ganymede. These distinct emissions, called ‘auroral footprints,’ are locally visible in several wavelength domains. They are created by charged particles, predominantly electrons, that propagate along magnetic field lines connecting the moons to Jupiter. As these electrons precipitate into the giant planet’s atmosphere, they induce characteristic auroras, which have been studied since the 2000s, notably through observations from the Hubble Space Telescope in the ultraviolet domain.
Since July 2016, the Juno probe has been flying over Jupiter’s poles at just a few thousand kilometers altitude, allowing for a detailed characterization of the moons’ auroral footprint structures. The combined analysis of data obtained by Juno’s UVS spectrograph and JADE spectrometer enables probing both the properties of these emissions and those of the charged particles that induce them.
Focusing their study on the auroral footprint of Ganymede, the largest moon in the solar system and the only one generating its own magnetic field, a team of scientists from IRAP in Toulouse and LAM, in close collaboration with Juno mission teams (SwRI, Princeton University), has, among other things, demonstrated the influence of Ganymede’s mini-magnetosphere on its auroral footprint. They confirmed that the size of the flux tubes, these tubular-shaped magnetic field lines connecting the moons to Jupiter’s atmosphere through which electromagnetic waves and charged particles propagate, is significantly larger than those reported for Io and Europa in previous studies. Juno’s observations of the auroral footprint thus provide a new method for studying Ganymede’s mini-magnetosphere, which will be explored in situ in an unprecedented manner by ESA’s JUICE mission currently en route to Jupiter, in which LAM and IRAP are also involved.
Link to the INSU press release :
Publication : Rabia, J., Hue, V., André, N., Nénon, Q., Szalay, J. R., Allegrini, F., et al. (2024). Properties of electrons accelerated by the Ganymede-magnetosphere interaction: Survey of Juno high-latitude observations. Journal of Geophysical Research: Space Physics, 129, e2024JA032604. https://doi.org/10.1029/2024JA032604
Contact at LAM : Vincent Hue vincent.hue@lam.fr Professeur à Aix-Marseille Université / Institut Origines / Laboratoire d’Astrophysique de Marseille
The French Astronomy Week in Marseille
LAM is delighted to have organised the French Astronomy Week from 4 to 7 June, with the support of Aix-Marseille University, the OSU Pythéas, the Institute Origines and the City of Marseille. The event attracted a record number of participants, over 500, and the LOC from LAM was responsible for setting up and providing technical assistance for 22 scientific and societal workshops in addition to the plenary sessions, covering all the key issues for our community. The participants came away very satisfied with their stay in Marseille!
The SF2A awards ceremony took place at Marseille’s Espace Bargemon during a convivial evening. The prizes awarded were the Young Researcher prize, the thesis prize, the school prizes in the Discover the Universe competition (with prizes for pupils donated by the SF2A, the Andromède association and the Vaonis company), and the Flammarion prize for scientific dissemination (with prizes donated by the SF2A and a telescope donated by the Unistellar company). A public lecture was organised to mark Astrophysics Week at the Artplèxe-Canebière cinema. P-O Lagage and V. Buat presented the first results of the JWST to the public in Marseille.
Auroras seen across France on the night of 10 May
On the night of the 10th May 2024, observers of the night sky were treated to an exceptional spectacle: intense aurora borealis illuminated all of France (Figure 1) for the first time in nearly 20 years. This auroral storm, which lasted almost 20 hours, could be admired by those in North America as the night progressed.
More than just a poetic spectacle, the auroras are the visible part of a chain of fascinating physical processes, which can occur throughout the solar system and beyond. Understanding such processes inspires a large community of researchers, but they are also often the object of reductive simplifications and confusion, particularly in the press.
Figure 1 : Images of the aurora observed on the night of 10-11 May 2024 in Touraine (left, credits : N. Biver) or at Mont Ventoux (right: credits : K en B photography).
The lights in the upper atmosphere
The polar aurora, borealis in the North and australis in the South, are luminous emissions which are produced in the high atmosphere, between 80 km and several hundreds of km above sea level. The aurora are found neighbouring the magnetic poles, hence the use of the adjective “polar”. Seen from space, they are concentrated along two magnetically connected high-latitude ovals with an average position of between 60° and 70°. The aurora are produced by the influx of energetic, electricaly charged particles – electrons and ions – into the magnetosphere, the magnetic cavity which surrounds the Earth (a schematic is seen in Figure 2). When these particles reach the atmosphere – the more energy they have, the lower they penetrate – they transfer a part of their kinetic energy to the local atoms and molecules which re-emit it in the form of light. The observed colours in the visible range and their altitude are thus characteristic of the chemical composition of our atmosphere: the green and red emissions are produced by atomic oxygen at both low and high altitudes, the red and blue/purple emissions by neutrall or ionised molecular Nitrogen at lower altitudes (Table 1).
Table 1 : Main lines and bands of visible aurora (taken from Mottez, 2017).
Figure 2 : Artist’s representation of the terrestrial magnetosphere. The blue lines show the magnetic field lines which connect the Northern and Southern magnetic poles.
A proxy of solar-terrestrial interactions
Let’s now look at the origin of the particles which produce the aurora, which has only been understood since the dawn of the space era. It is often said that the aurora are produced directly by solar wind (see below) particles, but this is not exactly true (see this compilation of misconceptions on the aurora by F. Mottez) As discussed above, they come directly from the magnetosphere. This cavity is produced by the interaction between the Earth’s magnetic field and the solar wind, this magnetised stream of charged particles that constantly flows throughout the solar system. As shown in Figure 2, it is compressed on the dayside, where it extends to more than 10 Earth radii, and is elongated on the nightside. Charged particles enter the magnetosphere from two reservoirs; the lesser being the upper, ionised part of the terrestrial atmosphere (the ionosphere), and the larger being the solar wind. Depending on its configuration, the solar wind can provide more or less particles, as we will see below. As these particles circulate around the magnetosphere, they can easily acquire sufficient energy to enter the atmosphere. The aurorae are therefore produced almost permanently, but their low intensity and/or high altitude renders them generally poorly visible to an observer on the ground. Nevertheless, the auroral activity periodically intensifies with bright, intense arcs during events known as “substorms”; the triggering of which depends on a principal ingredient: the orientation of the solar magnetic field as seen from the position of Earth.
Figure 3 : An auroral substorm photographed by the POLAR spacecraft on the 12 March 2014. The aurora, here observed in the UV domain, intensify on the nightside (in the upper-right of each image) of the magnetosphere. Crédits : NASA.
The terrestrial magnetosphere provides a shield that protects us against the solar wind. The solar wind has a magnetic field however, and when it is oriented towards the South the shield of the magnetosphere becomes less effective. Under such circumstances, a magnetic connection is established and permits solar wind particles to enter the magnetosphere. These particles are transported over the poles and accumulate at the equator on the nightside of the magnetosphere where they are accelerated in bursts towards the Earth, producing intense aurorae on the nightside which have a wide extent in latitude. The substorm cycle, described here in only a few lines, is a complex physical phenomenon that has been studied by researchers for more than half a century. The understanding of such events has been the objective of numerous space missions, most recently including the satellite constellations of Themis and MMS. Figure 3 shows an example of aurora during the development of a substorm.
Figure 4 : Animation of the aurora borealis (top) and aurora australis (bottom) observed on the 10th May 2024 by the DMSP spacecraft. The transition between a thin oval around +65° of latitude to a wide, intense oval reaching latitudes < 50° is spectacular and quite rare. Credits : JhuAPL, NOAA. https://ssusi.jhuapl.edu/gallery_AUR
The solar wind can also, but a lot more occasionally, produce particularly intense aurorae when it violently compresses the terrestrial magnetosphere. This is known as a geomagnetic storm, which induces substorms and bright auroral features that reach low latitudes. This is what occurred on the 10th May, when spacecraft measured the auroral morphology seen in figure 4, showing bright aurora reaching latitudes below 50°. Two days earlier, the sun had emitted a series of six coronal mass ejections, bubbles of dense, rapid plasma which coalesced and reached the Earth near midday on 10th May and triggered a major (G5 class) geomagnetic storm, the most intense since 2003.
Happy as Ulysses
These auroral storms are therefore directly linked to solar activity, and the next two years, corresponding to the next peak in solar activity, should bring their share of major solar flares. This should present plenty of opportunities to observe the manifestations of interactions between the magnetic field of our planet and the plasma emitted by our star, including such auroral displays. Amateurs can follow the solar and auroral activity in real time on the dedicated websites such as https://www.spaceweatherlive.com
Auroral emission can also be observed in other wavelength ranges on Earth (from radio to X-rays) and, more generally, on magnetised planets and stars, making it possible to study their magnetospheres. These auroral processes have been analysed in detail on the giant planets using polar probes such as Cassini/Juno or the Hubble space telescope and on distant stars with large ground-based radio telescopes. Their study is one of the LAM’s research priorities.
A risk for industry
A more tangible consequence of the compression of the magnetosphere is the impact that the solar activity can have on us on the ground at Earth. The observation and prediction of solar activity and the consequences at Earth have given birth to the discipline of space weather, defined thus by the European space agency: “Space weather studies the environmental conditions of the thermosphere, ionosphere, and terrestrial magnetosphere caused by the Sun and the solar wind, which can affect the operation and reliability of systems or services on the ground or in space, or endanger human health or property.”. Various French research bodies are involved in these aspects, which are beyond the scope of this article, including the French organisation for space weather applications research.
L. Lamy
Astronome-adjoint, LAM/Aix-Marseille Université et LESIA/Observatoire de Paris.
J. Waters
Chercheur post-doctoral CNES, LAM/Aix-Marseille Université
References : Aurores polaires, la Terre sous le vent du soleil, F. Mottez, Belin, 2017.
Navigate the VESTIGE data
VESTIGE (a Virgo Environmental Survey Tracing Ionised Gas Emission) is a CFHT large programme to observe the Virgo cluster in the r-band and in a narrow Hα filter. Alessandro Boselli is the PI.
VESTIGE has published its first data. This first publication contains JPG images of all the galaxies detected in Hα, together with FITS images for galaxies whose data have been validated in a publication. This data is available at this address https://mission.lam.fr/vestige/data.html
VESTIGE also provides the community with an all-sky view of the Virgo cluster in four versions
Virgo cluster in four versions:
– The r-band image : https://mission.lam.fr/vestige/data/HiPS/LAM_P_VESTIGE_r
– The image of the narrow filter Hα : https://mission.lam.fr/vestige/data/HiPS/LAM_P_VESTIGE_Halpha
– The image of the net flux Hα calculated by the project : https://mission.lam.fr/vestige/data/HiPS/LAM_P_VESTIGE_Halpha_net
– An RGB image combining these three images (start with this one): https://mission.lam.fr/vestige/data/HiPS/LAM_P_VESTIGE_RGB
Note that you can enter these URLs in the desktop version of Aladin.
Nicolas Laporte, winner of the Trophée Cned Éducation 2024
On March 19, Nicolas Laporte received one of the six “Français à l’Etranger” Trophies, in the “Education” category, at the Ministry of Foreign Affairs in Paris, in the presence of Minister Franck Riester (see picture below). Nicolas was rewarded for his work in research and popularization while a senior fellow at the Kavli Institute for Cosmology at Cambridge University (UK). Since then, Nicolas Laporte has joined the LAM where is pursuing his excellent work in research and science outreach!
Installation of the last modules of the PFS spectrograph in Hawaii
The SUBARU Prime Focus Spectrograph (PFS) is a wide-field multi-object spectrograph based on an international collaboration. PFS will carry out three major spectroscopic surveys with scientific objectives in cosmology, galaxy evolution and galactic archaeology.
Each of the international partners is making a contribution under a framework agreement, with the aim of building a 2400-fibre multi-object spectrograph (https://pfs.ipmu.jp/index.html). This new instrument exploits the wide field of the primary focus of the Subaru telescope, which houses the fibre positioner. The 60 m long fibres feed the spectrograph, which is located in a room heated to 5°C on one of the Nasmyth platforms. There are in fact 4 strands of 600 fibres each connected to the 4 spectrograph modules. Each module has 4 spectral channels from 380 to 1260 nm (https://pfs.ipmu.jp/research/parameters.html).
The LAM is responsible for the integration and testing of all the spectrographs, a task carried out within the laboratory. The Assemblies, Integrations and Tests (AIT) adventure, which began in 2015 and has been fraught with pitfalls, will come to an end in 2024 with the installation of all the modules at the Subaru telescope on the summit of Mauna Kea.
Two spectrograph modules with their Blue, Red and Near Infrared cameras had been installed and already tested on the sky before spring 2023. The two remaining spectrograph modules were shipped in 2023 and installed by a team from the LAM.
Performance tests have been carried out on the sky since 2023 and have shown the excellent functionality of all parts of the PFS instrument. However, an anomaly in the spectro-photometric transmission on the sky expected from the instrument has been detected, and after extensive analysis by a ‘tiger team’, the LAM’s PFS team has hypothesised that the PFS optical dispersive gratings may be misaligned, shifting and reducing the peak absolute transmission per band.
A spectrograph module has four channels, i.e. four gratings: three for the low-resolution channels (LR ~2000) in the blue, red and near infrared, and one for the medium-resolution mode (MR ~4500) in the red only.
Additional analyses, studies and tests have been carried out at JHU Baltimore, Bertin Winlight, IPMU Tokyo and at the LAM in 2023 to confirm this hypothesis and then to develop, test and validate a method and tooling that can change the orientation of gratings bonded to their support by 180 degrees. These reversals required special tools to handle the 50kg of optics. The consortium worked together to come up with the best solution in time.
The LAM team intervened in two stages, firstly to turn over the simple (low-resolution) 20kg gratings in the 3 spectral channels of each module in November 2023, and then to turn over the gratings in the 4th medium-resolution spectral channel (50kg optics) in February 2024.
The spectrograph is now almost complete.
The LAM has delivered, installed, aligned and validated the optical performance of all the spectrograph modules in collaboration with the Subaru team on site. However, two of the four near-infrared cameras need work to correct the inefficiency of their detectors. These operations are underway under the responsibility of JHU and Subaru. The telescope is once again operational after a shutdown period of several months, and tests on the PFS sky were carried out at the beginning of March 2024.
Some photographs of the team:
The JWST identifies a transition in the star formation mode of young galaxies.
Most galaxies follow a tight relation between their stellar mass and their star formation rate, implying that they form their stars gradually rather than through violent episodes of starbursts. Constrained up to z=6, when the Universe was 1 billion years old, this relation, called the galaxy main sequence, seems difficult to reconcile with the stochastic star formation of the very first galaxies predicted by simulations. Thanks to JWST data from the JADES extragalactic survey, researchers from LAM have highlighted a transition between these two modes of star formation when the Universe was about 700 million years old. They have used a new approach to reconstruct the star formation history of galaxies in order to study the establishment of the galaxy main sequence in the primordial Universe. In this study, they also showed that the stochasticity of the star formation they measure is not sufficient to explain the excess of very bright UV galaxies at z>10 observed in several studies of the earliest galaxies.
These results are part of a publication in press in A&A and are available in open access (https://arxiv.org/pdf/2309.15720.pdf).
LAM researchers involved in this study are Laure Ciesla, Olivier Ilbert, Véronique Buat, and Rafael Arango-Toro.
Best wishes 2024
All the teams at Laboratoire d’Astrophysique de Marseille would like to wish you the very best for 2024.
Training session for teachers at LAM
As part of the Year of Physics 2023-2024, the LAM welcomed some 50 teachers to the laboratory, in a training session organized with the Aix-Marseille education authority and the CNRS.
The program included introductory remarks by director Stéphane Arnouts, lectures by Stéphanie Escoffier, Alexandre Santerne and Annie Zavagno, and an afternoon tour of the laboratory to help participants discover the scientific themes, latest news and instrumental resources that enable us to push back the frontiers of astrophysical knowledge!
Webb reveals that galaxy mergers are the solution to early Universe mystery
One of the key missions of the NASA/ESA/CSA James Webb Space Telescope is to probe the early Universe. Now, the unmatched resolution and sensitivity of Webb’s NIRCam instrument have revealed, for the first time, what lies in the local environment of galaxies in the very early Universe. This has solved one of the most puzzling mysteries in astronomy — why astronomers detect light from hydrogen atoms which should have been entirely blocked by the pristine gas that formed after the Big-Bang. These new Webb observations have found small, faint objects surrounding the very galaxies that show the ‘inexplicable’ hydrogen emission. In conjunction with state-of-the-art simulations of galaxies in the early Universe, the observations have shown that the chaotic merging of these neighbouring galaxies is the source of this hydrogen emission.
Light travels at a finite speed (300 000 kilometres per second), which means that the further away a galaxy is, the longer it has taken the light from it to reach our Solar System. As a result, not only do observations of the most distant galaxies probe the far reaches of the Universe, but they also allow us to study the Universe as it was in the past. In order to study the very early Universe, astronomers require exceptionally powerful telescopes that are capable of observing very distant — and therefore very faint — galaxies. One of Webb’s key capabilities is its ability to observe those very distant galaxies, and hence to probe the early history of the Universe. An international team of astronomers have put Webb’s amazing capacity to excellent use in solving a long-standing mystery in astronomy.
The very earliest galaxies were sites of vigorous and active star formation, and as such were rich sources of a type of light emitted by hydrogen atoms called Lyman-α emission. However, during the epoch of reionisation an immense amount of neutral hydrogen gas surrounded these areas of active star formation (also known as stellar nurseries). Furthermore, the space between galaxies was filled by more of this neutral gas than is the case today. The gas can very effectively absorb and scatter this kind of hydrogen emission, so astronomers have long predicted that the abundant Lyman-α emission released in the very early Universe should not be observable today. This theory has not always stood up to scrutiny, however, as examples of very early hydrogen emission have previously been observed by astronomers. This has presented a mystery: how is it that this hydrogen emission — that should have long since been absorbed or scattered — is being observed? Researcher at the University of Cambridge and principal investigator on the new study Callum Witten elaborates:
“One of the most puzzling issues that previous observations presented was the detection of light from hydrogen atoms in the very early Universe, which should have been entirely blocked by the pristine neutral gas that was formed after the Big-Bang. Many hypotheses have previously been suggested to explain the great escape of this ‘inexplicable’ emission.”
The team’s breakthrough came thanks to Webb’s extraordinary combination of angular resolution and sensitivity. The observations with Webb’s NIRCam instrument were able to resolve smaller, fainter galaxies that surround the bright galaxies from which the ‘inexplicable’ hydrogen emission had been detected. In other words, the surroundings of these galaxies appear to be a much busier place than we previously thought, filled with small, faint galaxies. Crucially, these smaller galaxies were interacting and merging with one another, and Webb has revealed that galaxy mergers play an important role in explaining the mystery emission from the earliest galaxies. Nicolas Laporte, team member from Aix-Marseille University, adds:
“Where Hubble was seeing only a large galaxy, Webb sees a cluster of smaller interacting galaxies, and this revelation has had a huge impact on our understanding of the unexpected hydrogen emission from some of the first galaxies.”
The team then used state-of-the-art computer simulations to explore the physical processes that might explain their results. They found that the rapid build-up of stellar mass through galaxy mergers both drove strong hydrogen emission and facilitated the escape of that radiation via channels cleared of the abundant neutral gas. So the high merger rate of the previously unobserved smaller galaxies presented a compelling solution to the long-standing puzzle of the ‘inexplicable’ early hydrogen emission.
The team are planning follow up observations with galaxies at various stages of merging, in order to continue to develop their understanding of how the hydrogen emission is ejected from these changing systems. Ultimately, this will enable them to improve our understanding of galaxy evolution.
These findings have been published today in Nature Astronomy.
New Astronomy Finding Uncovers the Mystery of Star Formation at the Edge of Galaxies
International research team led by Stony Brook Professor Jin Koda and including Samuel Boissier from LAM uncovers the Mystery of star formation at the edge of Galaxies
The mystery of star formation in galaxies continues to intrigue astronomers worldwide. Yet a key question remains just how and why and where do stars form in the Universe? A new discovery from an international team of astronomers
provides a significant clue to star formation.
The research team used the Atacama Large Millimeter/submillimeter Array (ALMA) and investigated the far edge of the spiral galaxy M83, at a distance of 15 million light years from earth. They uncovered 23 concentrations of a dense molecular gas called “molecular clouds,” which are evidence of the birthing region of stars.
Molecular clouds are a typical site for star formation in the inner parts of galaxies. When it comes to the far edges of many galaxies, scientists had yet to understand how and why stars form because they could not pinpoint their formation sites. Yet, a surprising number of very young stars are known to exist at the far edges of many galaxies. The discovery of these 23 molecular clouds appears different from their counterparts in the typical star-forming sites in
galaxies. The large bodies of these clouds were not visible like “normal” molecular clouds—only their star-forming dense cores, the “hearts” of the clouds, were observed. This new research finding opens the door to a better understanding of the process of star formation in the Universe in general.
Additionally, the molecular cloud discovery uncovered a key link to the large reservoir of the diffuse atomic gas within the clouds. Normally, the atomic gas condenses into dense molecular clouds, where even denser cores develop and form stars. This process of conversion from atomic to molecular gas occurs even at the galaxy edges, but the conversion turned out to be very inefficient.
Koda and colleagues presented their findings in the 243rd meeting of the American Astronomical Society (AAS) in New Orleans on January 8. The AAS presentation included a confirmation of the hypothesis presented in a 2022 paper, titled “First Detection of the Molecular Cloud Population in the Extended Ultraviolet Disk of M83,” published in The Astrophysical Journal , along with new findings by way of the Jansky Very Large Array (VLA) and Green Bank Telescope (GBT).
Samuel Boissier contributed to the discovery of star formation at galaxy edges 18 years ago by the NASA’s GALEX satellite in so-called XUV galaxies, such as M83 . “This type of star formation at galaxy edges have been a nagging mystery since their discovery” says Koda, lead researcher. “Astronomers are eager to understand how stars form, and our discovery provides a clue to star formation processes.” Koda and co-authors write that “these molecular clouds are likely the main drivers of the star formation activity in galaxy edges.” They further explain: “We hypothesized that these clouds share, on average, the same common structure (mass distribution) as molecular clouds in the Milky Way, such as Orion, and have star-forming dense cores embedded in thick layers of bulk molecular gas. However, their envelopes are invisible.”
The revelation of these molecular clouds uncovered a link to a large reservoir of diffuse atomic gas, another discovery by this research. Normally, atomic gas condenses into dense molecular clouds, within which even denser cores develop and form stars. This process is in operation even at galaxy edges, but the conversion of this atomic gas to molecular clouds was not evident, for reasons that are unresolved.
Koda and colleagues came to their conclusion by using data collected using several instruments including the Atacama Large Millimeter/submillimeter Array (ALMA), the Karl G. Jansky Very Large Array (VLA), and the Green Bank Telescope (GBT), as well as with the National Astronomical Observatory of Japan’s (NAOJ) Subaru Telescope and the NASA Galaxy Evolution Explorer (GALEX).
Amanda Lee, who was an undergraduate student on Koda’s research team at Stony Brook University, processed GBT & VLA data for these findings. Through this, she discovered the atomic gas reservoir at the galaxy edge.
“We still do not understand why this atomic gas does not efficiently become dense molecular clouds and form stars,” adds Lee, who is now pursuing her Ph.D. in astronomy at UMass Amherst. “As often is the case in astronomy, pursuing answers to one mystery can often lead to another. That’s why research in astronomy is exciting.”
The research that led to team’s findings was supported in part by National Science Foundation grant AST-20006600 and by NASA grant NNX14AF74G.
LAM women in the spotlight
Because they represent the LAM and make science shine, whether they are researchers, teacher-researchers, engineers, technicians or administrators, we have decided to honor them through a mosaic in which a number of women have agreed to take part.
This panorama illustrates that an astronomy laboratory is open to all. A particularly important message for young girls wondering about their future! At the LAM, women make up around a quarter of the workforce, and are present in all the professions that make up astronomy: female researchers study the solar system, planets, galaxies or astronomical instrumentation. But there are also women engineers and technicians working in all fields: optics, mechanics, administration, IT… Some of them have also won prestigious prizes and are helping to spread a taste for science among the younger generation. Well done, and thank you.
The LAM prepares for the launch of Euclid, carrying the NISP instrument made in Marseille
On Saturday July 1, the Euclid satellite will be launched at 5:11 pm (Marseille time) and propelled towards its trajectory to reach the Lagrange L2 point one month later. Lift-off will take place from Cape Canaveral, aboard the SpaceX/Falcon 9 rocket. After ten years of development in which the LAM has played a leading role, as prime contractor for one of the two instruments, the NISP, this is a key phase in the project. You can find out more about this instrument on the project’s dedicated web page: https://www.lam.fr/projets/euclid-nisp/
Work on Euclid at the LAM is not yet finished. We will continue to work on data processing, and finally in a few months’ time on scientific analysis. Euclid will map the distribution of galaxies on large scales, giving us crucial new information on dark matter and dark energy in the universe.
You can follow the event live on several of the sites listed below.
SPACE X (English):
Space X broadcast: https://www.spacelaunchschedule.com/launch/falcon-9-block-5-euclid/
ESA (English only):
ESA broadcast: https://www.youtube.com/watch?v=1zcmH5aESHo
CNES/CNRS with the Stardust channel (in French)
Stardust : https://www.youtube.com/watch?v=rxczLEzzKrE
A new Tatooine-type multi-planetary system identified
An international team of astronomers has announced the second discovery of a multi-planetary circumbinary system. Circumbinary systems are unusual in that they contain planets that orbit two central stars rather than just one, as in our own solar system. The researchers involved in this team come from the University of Birmingham and the Laboratoire d’Astrophysique de Marseille (OSU Institut Pythéas / CNRS, AMU, CNES). This discovery is presented in the Monday 12 June 2023 issue of the journal Nature Astronomy.
Astronomy Festival of Provence : the end !
The 1st edition of the Festival of Astronomy of Provence was held as planned from May 6 to 12, 2023. At the end of a week rich in events, and in spite of the climatic hazards, we were able to ensure the almost integrality of the scientific program, except for the final evening of open air observations (cancelled because of rain). With about 40 astrophysicists from the LAM and about 30 volunteers from partner associations, supported by the CNRS, Aix-Marseille University and the French Astronomy and Astrophysics Society, the organizing committee welcomed more than 1500 people on the sites of the Historical Astronomical Observatory of Longchamp and of the LAM at Chateau-Gombert, as well as in the conference rooms lent by the cities of Marseille, Allauch and Plan-de-Cuques. Thanks to all and see you soon for new adventures!
Laure Ciesla, price for young researcher from SF2A 2023.
The SF2A board has awarded the 2023 young researcher prize to Laure Ciesla from the LAM. Laure Ciesla has been a researcher at the LAM since 2018. Her research focuses on the evolution of galaxies, guessing their history by using their spectral energy distribution and modelling it with the CIGALE code, in which she integrates, for example, the emission of supermassive black holes at the centre of galaxies, or is interested in the contribution of artificial intelligence to this subject. She is very involved in the PRIMA project (Probe far-infrared mission for Astrophysics), under discussion between NASA and CNES. She is also co-leader of the GECO team, and has organised a meeting at the LAM between young students and women in astrophysics, to fight against gender bias.
New Results for PAPYRUS at OHP!
PAPYRUS is an Adaptive Optics bench developed and put on sky by the LAM and ONERA at the Observatoire de Haute Provence (OHP). Since its release in June 2022, it has successfully corrected turbulence on multiple objects: single stars, double stars and extended object (Mars). These data feed abundantly the research in Adaptive Optics in order to provide better performing instruments to the community. Thus PAPYURS is a unique platform in France and in Europe allowing to test on the sky the new ideas and the new components developed by the scientific teams.
The Papyrus project allows to prepare and validate technological bricks which will come to equip the future instruments of the VLT and the ELT.
At the beginning of January, all the PAPYRUS team was gathered at the OHP for a week of observations and tests.
Among all the tested novelties, one of them concerned the acceleration of the Adaptive Optics loop to correct the effects of the turbulence up to 1500 times per second! The results are convincing as you can see on the attached animation.
Without the correction provided by PAPYRUS, the image of a star (on the left) is about 3 arcseconds, but thanks to the Adaptive Optics of PAPYRUS, the light is concentrated on less than 0.1 arcseconds. A gain of a factor 30 on the angular resolution! And above all a demonstration of the robustness of PAPYRUS to « erase » the effects of the atmosphere.
Congratulations to all the teams involved, and stay tuned for more great results to come!
Workshop on tele-work at LAM
On 30 January, a “co-construction workshop” was held on telework at the LAM, and more specifically on “how to respond to the problems raised by the results of the survey sent to staff on this subject”. Several topics were discussed (how to welcome a newcomer in hybrid mode, how to encourage inter-service and inter-team exchanges, how to maintain group cohesion, etc.). The objective was to draft a telework charter and to put in place effective actions to improve this system, using a “Word café” method (a creative process which aims to facilitate constructive dialogue and the sharing of knowledge and ideas) around several questions to be addressed, a reflection on our values, and a brainstorming session on the actions to be developed and the ideas to be included in the charter.
All staff were involved, ensuring that there was at least one teleworker and one non-teleworker per team and department. The participants were all motivated and there were many relevant ideas. This will lead to the drafting of a charter and the study of possible actions by the laboratory council.
LAM general assembly
On 16 January, the LAM’s traditional general meeting took place, an opportunity for all the staff to discover the Henri Fabre trophy, awarded by the Marseille Academy of Sciences, Arts and Letters to the whole laboratory, but also to thank Jean-Luc Beuzit, director of the LAM since 2018, who will now be the director of the OSU Pythéas. Samuel Boissier, formerly deputy director, is now acting director of the LAM until 1 January 2024.
It was also an opportunity to enjoy a piece “galette” in a good mood and in a friendly atmosphere
Click to know the new graduate students at LAM
The new graduate students starting their thesis this autumn are listed here:
Brieuc COLLET, started September 1st in GSP (ED 352 funds),
Supervisor: Laurent Lamy.
Title: In situ analysis of Jovian auroral decametric emissions with Juno
Lisa ALTINIER, starting October 1st in GRD (ERC funds).
Supervisors: Arthur Vigan and Elodie Choquet.
Title: Development of image processing methods for the detection of exoplanets in reflected light with the NASA Roman Space Telescope.
Alizée AMSLER, starting October 1st in GSP (AMU funds).
Supervisors: Olivier Mousis and Alexis Bouquet.
Title: Physico-chemical evolution of ice moon hydrospheres.
Rafael ARANGO-TORO, starting October 1st in GECO (ED 352 funds).
Supervisors: Laure Ciesla and Olivier Ilbert.
Title: Star Formation Histories of galaxies from deep multi-color images.
Houda BELLAHSENE, starting October 1st in GRD (LabCom NanoPTov ANR funds).
Supervisors: Yannick Guari (Institut Charles Gerhardt Montpellier, Montpellier) and Marc Ferrari.
Title: Optimization of surface chemistry processes for hyper-polished mirrors.
Loris BERTHELOT, starting Dec 1st in the GECO at LAM and QARMA at LIS (Interdisciplinary, CNRS 80PRIME fellowship).
Supervisors: Annie Zavagno (LAM) et Thierry Artières (LIS)
Title: Big Data et Apprentissage automatique pour l’étude de la formation stellaire Galactique
Salomé GROUFFAL, starting October 1st in GSP (CNES – Institut Origines funds).
Supervisor: Alexandre Santerne.
Title: Characterization of transiting exoplanets in the habitable zone.
Ny-Avo RAKOTONDRAINIBE, starting October 1st in GECO (AMU funds).
Supervisor: Véronique Buat.
Title: Multi-wavelength analysis from X-rays to the optical domain for the characterization of gamma-ray bursts and the galaxies that host them: the SVOM/COLIBRI synergy.
Théo SIEG-LETESSIER, starting October 1st in GRD (LabCom NanoPTov ANR funds).
Supervisors: Marc Ferrari and Ray Barret (European Synchrotron Radiation Facility, Grenoble)
Title: Metrology of large optical components with sub-nanometric accuracy.
Paolo SUIN, starting October 1st in GECO (ED 352 funds).
Supervisor: Annie Zavagno.
Title: High mass stars’ feedback impact on star formation properties.
Simon HANS, Starting November 1st in GRD (CNES – Thales Alenia Space funds)
Supervisors: Frédéric Zamkotsian and Guillaume Demésy (Institut Fresnel)
Title: Nanostructured blazed gratings for efficient and compact spectro-imagers in space.
Romain MAYER, Starting November 1st at Laboratoire Lagrange & LAM-GRD (Region Sud and ACRI-ST funds).
Supervisors: David Mary (Lagrange) & Elodie Choquet.
Title: Detection of exoplanets in high-contrast images using statistical learning.
Arnaud STRIFFLING, Starting November 1st in GRD.
Supervisors: Jeff Sauvage and Alexis Carlotti (IPAG)
Title: .Coupling adaptive optics and a high contrast instrument: ultimate performance of the pyramid analyzer.
Tom BENEST, will start in December 1st in GSP,
Supervisor: Olivier Mousis
Title: Study of the formation conditions of the Jupiter system.
Francisco OYAZUN, Starting December 1st in GRD.
Supervisors: Benoit Neichel, Thierry Fusco & Jean-Luc Gach
Title: Innovative detectors for high-performance Adaptive Optics. Application to exoplanet detection.
Jordi ROUBICHOU, starting December. 1st in GRD (CIFRE Thales Land & Air Systems funds).
Supervisor: Jean-Luc Beuzit; Advisors: Jean-Luc Gach (LAM) & Jean-Luc Reverchon (TLAS)
Title: Study of new types of SWIR detectors: extension of the operating band beyond 1.7μm
Crédit illustration: Image by pch.vector on Freepik
When a star metamorphoses into a black hole
On Sunday 9 October 2022, at precisely 13:16:50, the most energetic flare ever observed on Earth was detected by the US satellites FERMI and SWIFT. This flare, called GRB 221009A (GRB stands for Gamma Ray Burst), is the signature of the gravitational collapse of a very massive star (over 20 to 30 times the mass of the Sun) into a black hole.
But this gamma-ray burst is absolutely exceptional because it released photons with an energy of 18 teraelectronvolts (an 18 followed by 12 zeros!), even leading to a disruption of long-range communications on Earth. Considering that this event was emitted at a distance of 1.9 billion light-years from Earth, in a galaxy located in the constellation of the Arrow, this makes GRB 221009A one of the most violent astrophysical phenomena since the formation of the Universe.
This phenomenon immediately triggered a rather remarkable observation campaign, involving considerable resources. Researchers from the Laboratoire d’Astrophysique de Marseille (LAM) actively contributed to this campaign, in particular thanks to the observation facilities of the Observatoire de Haute-Provence (OHP), the T193 with the MISTRAL instrument and the T120. Thanks to excellent coordination between the LAM and OHP teams, it was possible to follow this remarkable phenomenon for several days.
This observation prefigures the many discoveries to come from the SVOM satellite and its follow-up telescope, COLIBRI. The latter will have the task of detecting and studying these remarkable objects, namely the super gamma-ray bursts, from the middle of 2023. The LAM and the OHP, as co-leaders of SVOM and COLIBRI, will thus be able to continue to play a key role in this hunt, in which the MISTRAL instrument of T193 will naturally have its place.
Contacts :
Stéphane BASA : stephane.basa@lam.fr
Christophe ADAMI: christophe.adami@lam.fr
“Fête de la Science” event
Staff from the LAM participated extensively in this year’s science festival. In particular, the laboratory hosted “unusual visits” from the CNRS on October 12th. A video report by a journalist from La Provence who followed the visit is available here: https://www.laprovence.com/actu/en-direct/6931020/video-au-coeur-du-laboratoire-dastrophysique-de-marseille.html
The laboratory also had a stand on the site of the Marseille Science Festival which welcomed nearly 7000 visitors during the weekend. We were able to discuss with the public, show models, one of the first images of the James Web Space Telescope, or even make a model of a comet nucleus live in front of young and old. And we made some great encounters!
