Einstein Probe Uncovers Rare X-ray Binary System

The figure shows the Nova Outburst which was monitored by Einstein Probe WXT
© C. Maitra, Haonan Yang / MPE

---

Einstein Probe satellite, a collaboration of, among others, the Max Planck Institute for Extraterrestrial Physics (MPE) and the Chinese Academy of Sciences (CAS), has captured an extraordinary celestial event: an X-ray outburst from a rare binary system. This discovery sheds new light on the evolution of massive stars and demonstrates the unique capabilities of Einstein Probe in detecting transient X-ray sources.

On 27 May 2024, the satellite’s Wide-field X-ray Telescope (WXT) detected an unusual X-ray source in the Small Magellanic Cloud (SMC). Follow-up observations, including those from NASA’s Swift and NICER telescopes and ESA’s XMM-Newton, confirmed the discovery: a rare pairing of a massive Be-type star and a dense white dwarf. This dynamic duo defies conventional expectations—while the Be star is still burning brightly, its companion has already collapsed into a white dwarf.

"This discovery uncovers an elusive class of object called Be white dwarf binaries (BeWDs). Binary evolution models predict that BeWDs should be about seven times more common than Be-neutron star (BeNS) systems. However, its detection is difficult due to the supersoft nature of the X-ray emission, which can be absorbed by the circumstellar disc of the Be star”, explains MPE scientist Chandreyee Maitra, who contributed to the interpretation of the results.

Haonan Yang, a PhD student at MPE and CAS who led the Einstein Probe data analysis of this object, adds: "The large Field of View of Einstein Probe’s Follow-up X-ray Telescope (EP FXT) allows efficient monitoring of the Magellanic Clouds, where such objects are expected to be detected in plentiful. Moreover, in collaboration with WXT, FXT can turn to a transient source within as little as 3 minutes after a new discovery, with a positioning accuracy better than 10 arcsec. FXT’s large effective area also ensures high sensitivity to low-energy photons, which is critical for probing supersoft sources."

His work highlights FXT’s capabilities in monitoring the nearby galaxies like the Magellanic Clouds, where such objects are expected to be abundant.

“The discovery of this source highlights the importance of soft X-ray surveys with EP FXT and WXT to uncover supersoft X-ray sources and novae. Moreover, the nova outburst from this system indicates the presence of a massive white dwarf close its maximum possible value, i.e., the Chandrasekhar limit. This can be instrumental in solving the debate on the progenitors of Supernova 1a”, says Chandreyee Maitra.

Source: Max Planck Institute for Extraterrestrial Physics (MPE)/News

---

About Einstein Probe

MPE played a key role in the development of Einstein Probe’s Follow-up X-ray Telescope (FXT), contributing advanced optics and detector technology. The institute provided one of the FXT’s mirror modules, repurposing a spare from its eROSITA X-ray telescope, and collaborated with ESA and industry partners to supply the second. MPE also developed the state-of-the-art pnCCD detector modules, leveraging its expertise in high-precision X-ray spectroscopy.

---

Contact:

Dr. Chandreyee Maitra
Researcher in High-Energy Astrophysics Group
cmaitra@mpe.mpg.de
Max Planck Institute for Extraterrestrial Physics

Haonan Yang
PhD-student Highenergy group
tel: +49 89 30000-3347
hnyang@mpe.mpg.de
Max-Planck-Institut für extraterrestrische Physik, Garching

---

A. Marino, H. N. Yang, F. Coti Zelati, N. Rea, S. Guillot, G. K. Jaisawal, C. Maitra, et al.
Einstein Probe Discovery of EP J005245.1−722843: A Rare Be–White Dwarf Binary in the Small Magellanic Cloud?

ApJL 980 L36

Source | DOI

---

Einstein Probe detects puzzling cosmic explosion

January 23, 2025

Einstein Probe has opened a new window onto the distant X-ray Universe, promising new views of the most faraway explosions in the cosmos. Less than three months after launch, the spacecraft already discovered a puzzling blast of X-rays that could require a change the way we explain the extraordinary explosions known as gamma-ray bursts.

---

New discovery in the sky: Largest superstructure in the nearby universe unveiled

Distribution of galaxies (colour coding) and galaxy clusters (black dots) in a spherical shell with a distance of 416 to 826 million light years surrounding us. The five superstructures are marked: 1 Quipu, 2 Shapley, 3 Serpens-Corona Borealis and Hercules (overlapping in the sky), 4 Sculptor-Pegasus. The area enclosed by white lines is shadowed by the disk of the Milky Way. © MPE

---

A team of scientists has found the largest superstructure ever reliably characterised in the universe. The discovery was made while mapping the nearby universe using galaxy clusters detected by the ROSAT X-ray satellite's survey of the sky. With a length of about 1.4 billion lightyears, the new structure, which consists mainly of dark matter, is the largest known structure to date. Researchers at the Max Planck Institute for Extraterrestrial Physics (MPE) and the Max Planck Institute for Physics (MPP) led the study in collaboration with colleagues in Spain and South Africa.

Averaged over very large volumes, the universe appears almost homogeneous. On scales smaller than about a billion lightyears and in our cosmic neighbourhood, it is characterised by condensations of matter in superclusters and by voids. Precise knowledge of these structures is very important for cosmological research and the main motivation for mapping the nearby Universe.

“If you look at the distribution of the galaxy clusters in the sky in a spherical shell with a distance of 416 to 826 million light-years, you immediately notice a huge structure that stretches from high northern latitudes to almost the southern end of the sky,” explains Hans Böhringer, the project leader. It consists of 68 clusters of galaxies and has an estimated total mass of 2.4 1017 solar masses with a length of around 1.4 billion light years. This breaks the size record of all reliably measured cosmic structures. The largest of them so far, the “Sloan Great Wall”, for example, has a length of around 1.1 billion light years and it is located much further away.

An ATLAS of galaxy clusters

For their study, the scientists used an almost complete atlas of galaxy clusters in the nearby universe. “The catalogue was created with the help of the ROSAT X-ray satellite, built by MPE. In 1990, the satellite mapped the entire sky using a high-resolution X-ray telescope for the first time,” explains Joachim Trümper, the ROSAT project leader and emeritus Director of the MPE.

In the decades that followed, researchers worked to identify the galaxy clusters more precisely and to determine their distances. This resulted in a three-dimensional image of their distribution, in which the galaxy clusters precisely trace the structure of the large-scale distribution of matter in the universe, much like lighthouses trace a coastline. The catalogue covers the entire cosmic volume out to a distance of one billion light-years. In this region, the new structure appears much larger than all other structures.

Three-dimensional representation of the Quipu superstructure
© MPE

Importance for science: cosmography and cosmology

This finding is crucial for mapping the universe, but also for cosmological measurements. The researchers have shown how the presence of these structures affects the measurement of the Hubble constant or the microwave background. The cosmic background radiation was created shortly after the Big Bang and gives us important clues about the structure and evolution of the universe. The Hubble constant indicates the current expansion rate of the universe. “Even if these are only corrections of a few percent, they become increasingly important as the accuracy of cosmological observations increases,” emphasizes Gayoung Chon from the MPP.

The scientists have named their remarkable discovery “Quipu”, a term from the language of the Incas. The Incas used bundles of strings with knots for their bookkeeping and as letters. The superstructure resembles this ancient script, appearing as a long fibre with side strands woven into it. The scientists also chose the name because most of the distance measurements of the galaxy clusters were made at the European Southern Observatory (ESO) in Chile. The earthly quipus are on display at the Archaeological Museum in the capital Santiago de Chile - bringing us back to Earth from the far reaches of the cosmos.

Source: Max Planck Institute for Extraterrestrial Physics (MPE)/Press Releases

---

Contact:

Prof. Dr. Joachim Trümper
Direktor emeritus MPE
tel: +49 89 30000-3559
jtrumper@mpe.mpg.de
Max Planck Institute for Extraterrestrial Physics, Garching

Prof. Dr. Hans Böhringer
tel: +49 89 30000-3830
hxb@mpe.mpg.de
Max Planck Institute for Extraterrestrial Physics, Garching

---

Original publication

Hans Böhringer Gayoung Chon, Joachim Trümper, Renee C. Kraan-Korteweg, and Norbert Schartel
Unveiling the largest structures in the nearby Universe: Discovery of the Quipu superstructure

accepted for publication in Astronomy and Astrophysis

Source

---

Asteroid Bennu Sample Reveals a Broth of Life’s Ingredients

This mosaic image of asteroid Bennu is composed of 12 PolyCam images collected on Dec. 2 by the OSIRIS-REx spacecraft from a range of 15 miles (24 kilometers). The image was obtained at a 50° phase angle between the spacecraft, asteroid and the Sun, and in it, Bennu spans approximately 1,500 pixels in the camera’s field of view. Instrument Used: OCAMS (PolyCam). © NASA/Goddard/University of Arizona

Picture of the asteroid Bennu sample that was analyzed by the CAS group, with overlayed spectra taken by CAS Raman Microscope and in Helmholtz laboratories. © T. Grassi / B. Giuliano

---

Studies of rock and dust from asteroid Bennu delivered to Earth by NASA’s OSIRIS-REx spacecraft and analyzed by, among others, researchers from MPE’s Center of Astrochemistry (CAS), have revealed molecules that, on our planet, are key to life, as well as a history of saltwater that could have served as the “broth” for these compounds to interact and combine.

The findings do not show evidence for life itself, but they do suggest the conditions necessary for the emergence of life were widespread across the early solar system, increasing the odds life could have formed on other planets and moons.

"NASA’s OSIRIS-REx mission already is rewriting the textbook on what we understand about the beginnings of our solar system," said Nicky Fox, associate administrator, Science Mission Directorate at NASA Headquarters in Washington. “Asteroids provide a time capsule into our home planet’s history, and Bennu’s samples are pivotal in our understanding of what ingredients in our solar system existed before life started on Earth."

In research papers published Wednesday in the journals Nature and Nature Astronomy, scientists from NASA and other institutions, including MPE, shared results of the first in-depth analyses of the minerals and molecules in the Bennu samples, which OSIRIS-REx delivered to Earth in 2023.

“The CAS group is very proud to have contributed to analyzing the sample from asteroid Bennu using the CAS Raman Microscope. The Bennu sample from the OSIRIS-Rex mission was given to us by our long-term visiting scientist, Prof. Dr. Philippe Schmitt-Kopplin (Helmholtz Zentrum, München)”, says Paola Caselli, director at the Center for Astrochemical Studies (CAS), which contributed to the study. The work done at CAS has been part of the Master’s Thesis of Anique Shahid, under the supervision of Dr. Michela Giuliano, Dr. Tommaso Grassi, Paola Caselli (all CAS) and Prof. Schmitt-Kopplin (Helmholtz).

Detailed in the Nature Astronomy paper, among the most compelling detections were amino acids – 14 of the 20 that life on Earth uses to make proteins – and all five nucleobases that life on Earth uses to store and transmit genetic instructions in more complex terrestrial biomolecules, such as DNA and RNA, including how to arrange amino acids into proteins.

Source:  Max Planck Institute for Extraterrestrial Physics (MPE)/News

---

About NASA’s OSIRIS-REx

NASA Goddard provided overall mission management, systems engineering, and the safety and mission assurance for NASA’s OSIRIS-REx (Origins, Spectral Interpretation, Resource Identification and Security–Regolith Explorer). Dante Lauretta of the University of Arizona, Tucson, is the principal investigator. The university leads the science team and the mission’s science observation planning and data processing. Lockheed Martin Space in Littleton, Colorado, built the spacecraft and provided flight operations. NASA Goddard and KinetX Aerospace were responsible for navigating the OSIRIS-REx spacecraft. Curation for OSIRIS-REx takes place at NASA’s Johnson Space Center in Houston. International partnerships on this mission include the OSIRIS-REx Laser Altimeter instrument from CSA (Canadian Space Agency) and asteroid sample science collaboration with JAXA’s (Japan Aerospace Exploration Agency) Hayabusa2 mission. OSIRIS-REx is the third mission in NASA’s New Frontiers Program, managed by the agency’s Marshall Space Flight Center in Huntsville, Alabama, for the agency’s Science Mission Directorate in Washington.

---

Contacts:

Prof. Dr. Paola Caselli
Director of the CAS group at MPE
tel:+49 89 30000-3400
fax:+49 89 30000-3399
caselli@mpe.mpg.de
Max Planck Institute for Extraterrestrial Physics, Garching

Dr. Barbara Michela Giuliano
scientist in CAS group
tel:+49 89 30000-3317
giuliano@mpe.mpg.de
Max Planck Institute for Extraterrestrial Physics

Dr. Tommaso Grassi
Wissenschaftlicher Mitarbeiter, IT
tel:+49 89 30000-3639
tgrassi@mpe.mpg.de

Prof. Dr. Dr. Philippe Schmitt-Kopplin
Director of the Research Unit Analytical Biogeochemistry
tel:+49 89 3187-3246
philippe.schmittkopplin@helmholtz-munich.de
https://www.helmholtz-munich.de/en/bgc/pi/philippe-schmitt-kopplin
Helmholtz Munich

---

Further Information

Official Press release of NASA about analysis of Bennu asteroid.

---

Unveiling the 'Ghost' Baryonic Matter

This image shows the 3D structure of the over 7,000 cosmic filaments identified through SDSS optical surveys and the corresponding eRASS X-ray map in the same part of the sky. The colors of the filaments indicate the redshifts. © Xiaoyuan Zhang, Nicola Malavasi / MPE

The stacked 0.3—1.2 keV surface brightness profile of the 7817 cosmic filaments. Based on the knowledge of X-rays from extragalactic galaxies, the team estimated that a 40% of the stacked signal is contaminated by halo gas, active galactic nuclei, and X-ray binaries associated with galaxies in filaments. The remaining 60% is from the diffuse WHIM. © MPE/Xiaoyuan Zhang

---

A team of scientists from the Max Planck Institute for Extraterrestrial Physics has shed light on one of the most elusive components of the universe: the warm-hot intergalactic medium (WHIM). This "ghost" form of ordinary matter, long hypothesized but rarely detected, is thought to account for a significant portion of the universe's missing baryons — the matter that makes up stars, planets, and galaxies.

Led by Dr. Xiaoyuan Zhang, a postdoctoral fellow at the Max Planck Institute for Extraterrestrial Physics (MPE), the team of scientists revealed the existence of high-temperature, high-density regions of the WHIM by utilizing data from the eROSITA All-Sky Survey (eRASS). Over the course of two years, eROSITA, a powerful X-ray telescope aboard the Spektr-RG spacecraft, observed weak X-ray emission from the WHIM. To amplify these faint signals, the researchers employed a technique known as stacking, analyzing X-ray data at the locations of more than 7,000 cosmic filaments identified through the optical Sloan Digital Sky Survey (SDSS).

Due to its extremely low density (10 particles per cubic meter on average), the WHIM is notoriously difficult to observe. "Numerous studies have attempted to detect the WHIM using X-ray absorption, emission through X-rays, and the Sunyaev-Zeldovich effect. While some have yielded modestly positive results, they are often questioned due to potential contamination and systematic uncertainties. Now, with the eROSITA All-Sky Survey providing the deepest all-sky X-ray data, we have a unique opportunity to detect WHIM X-ray emission associated with large-scale cosmic structure." remarks Esra Bulbul, who is leading the clusters and cosmology group at the Max Planck Institute for Extraterrestrial Physics (MPE).

Tracing Cosmic Filaments

Cosmic filaments, the largest structures in the universe, form part of the intricate network of the cosmic web, which connects galaxies and galaxy clusters. Up to half of the matter in the Universe resides in filaments, which occupy less than 10% of its volume. Due to their anisotropic geometry and low density, filaments are difficult to detect in any of their components, such as gas or galaxies. “The most immediate way to achieve this is through the galaxy distribution. A breakthrough was accomplished when large-scale spectroscopic surveys such as SDSS became accessible and were coupled with complex algorithms to detect the filaments. This is the approach that we followed, which allowed us to trace the position of filaments to then allow for their stacking analysis.” says Dr. Nicola Malavasi, a Marie Skłodowska-Curie fellow at MPE, who performed the filament finding. Within these filaments resides the WHIM, a diffuse gas that emits only weak X-rays, making it nearly impossible to detect directly. However, the team’s sophisticated stacking method has allowed for a clearer picture of this emission, revealing the presence of WHIM and a measurement of its average temperature and density. This discovery brings scientists closer to resolving the long-standing puzzle of the universe's missing baryons and offers new insights into the structure and evolution of the cosmic web.

“Surprisingly, we had a strong X-ray detection (9σ) of the cosmic web. This was not the end of the story. We also needed to carefully model the contamination from the undetected galactic sources, which was the key to disclosing how much of our signal is from the WHIM.” said Xiaoyuan Zhang, the study's leading author. The study introduces an innovative method for estimating contamination from unmasked X-ray halos, active galactic nuclei, and X-ray binaries associated with filament galaxies. The analysis revealed an approximate 40% contamination fraction, indicating that around 60% of the detected signal may originate from the WHIM, with a detection significance of 5.4σ.

The team looked deeper into the properties of the recently detected WHIM, which allows them to gather critical insights into its nature. Their findings of the state-of-the-art numerical simulation indicate that the observed X-ray signal likely originates from WHIM regions with temperatures in the range of several million Kelvin and densities of approximately 100 particles per cubic meter.

Next-Generation Galaxy Surveys

Dr. Zhang adds, “Our new results demonstrate the immense potential of eROSITA’s survey data in detecting extremely faint diffuse cosmic plasmas.” Their work not only confirms the existence of the elusive WHIM but also opens new avenues for studying the role of these ghostly baryons in shaping the universe’s large-scale structure. This discovery marks a significant step forward in understanding the universe’s composition and the hidden ordinary matter that weaves the vast cosmic web together.

Andrea Merloni, Principal Investigator of the eROSITA project at MPE, ventures a look into the future: “Over the next few years, new large-scale spectroscopic galaxy surveys such as DESI and 4MOST will provide larger, more detailed galaxy and filament maps. The much larger overlap of these surveys with the eROSITA all-sky data will ensure a more refined analysis of the stacked X-ray data and bring to light new pieces of information on the WHIM physical state”.

Source: Max Planck Institute for Extraterrestrial Physics (MPE)/News

---

This project has received funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (grant agreement No 101002585)

---

Contact:

Dr. Xiaoyuan Zhang
Postdoc Highenergy Group
tel:+49 89 30000-3807
xzhang@mpe.mpg.de
Max Planck Institute for Extraterrestrial Physics

Dr. Esra Bulbul
Head of galaxy clusters group
tel:+49 89 30000-3502
ebulbul@mpe.mpg.de
Max Planck Institute for Extraterrestrial Physics

Nicola Malavasi
Marie Sklodowska-Curie EU Research Fellow High-Energy Group
tel:+49 89 30000-3040
malavasi@mpe.mpg.de
Max Planck Institute for Extraterrestrial Physics

---

Original Publication

Zhang, X.; Bulbul, E.; Malavasi, N.; Ghirardini, V. ; et al.
The SRG/eROSITA all-sky survey. X-ray emission from the warm-hot phase gas in long cosmic filaments.
A&A, 691, A234 (2024)

DOI

---

Further Information

ERC Project DarkQuest
Webpages of the ERC funded project led by Esra Bulbul

Cosmic dance of the ‘Space Clover’
April 30, 2024

A group led by MPE has, for the first time, detected X-ray gas at the location of the cloverleaf ORC, an odd radio circle (ORC). The origin of ORCs is unknown; in the case of the cloverleaf ORC, the combined data from different wavelengths indicate that the emission is due to a merger of two small galaxy groups.

eROSITA relaxes cosmological tension
February 14, 2024

Results from the first X-ray sky survey resolve the previous inconsistency between competing measurements of the structure of the Universe

eROSITA Cosmology Team

The Cluster and Cosmology working group is led by Dr. Esra Bulbul from MPE and consists of other researchers from MPE as well as from the Institute for Astro- and Particle Physics of Innsbruck University (IAPP).

---

eROSITA unveils asymmetries in temperature and shape of our Local Hot Bubble

3D model of the solar neighbourhood. The colour bar represents the temperature of the LHB as coloured on the LHB surface. The direction of the Galactic Centre (GC) and Galactic North (N) is shown in the bottom right. The link to the interactive version can be found at the bottom of the page. © Michael Yeung / MPE

Our Solar System dwells in a low-density environment called the Local Hot Bubble (LHB), filled by a tenuous, million-degree hot gas emitting dominantly in soft X-rays. A team led by scientists at the Max Planck Institute for Extraterrestrial Physics (MPE) used the eROSITA All-Sky Survey data and found a large-scale temperature gradient in this bubble, possibly linked with past supernova explosions that expanded and reheated the bubble. The wealth of the eROSITA data also allowed the team to create a new 3D model of the hot gas in the solar neighbourhood. The highlight of this work features the discovery of a new interstellar tunnel towards the constellation Centaurus, potentially joining our LHB with a neighbouring superbubble.

The idea of the Local Hot Bubble has been around for about half a century, first developed to explain the ubiquitous X-ray background below 0.2 keV. Photons of such energies cannot travel very far in the interstellar medium before they are absorbed. In conjunction with the observation that there is almost no interstellar dust in our immediate environment, the scenario where a soft X-ray emitting plasma displaces the neutral materials in the solar neighbourhood, forming the ‘Local Hot Bubble’, was put forth.

This understanding of our immediate environment was not without its challenges, especially after the discovery of the solar wind charge exchange process in 1996 — an interaction between the solar wind ions and neutral atoms within the Earth’s geocorona and the heliosphere that emits X-rays at similar energies as the LHB. After years of analysis, the consensus now is that both contribute to the soft X-ray background, and the LHB must exist to explain the observations.

The eROSITA telescope is the first X-ray observatory to observe the sky from an orbit completely external to the Earth’s geocorona, avoiding the latter’s contamination. Also, the timing of the first eROSITA All-Sky Survey (eRASS1) coincided with the solar minimum, significantly reducing the heliospheric solar wind charge exchange contamination. ‘In other words, the eRASS1 data released to the public this year provides the cleanest view of the X-ray sky to date, making it the perfect instrument for studying the LHB, ‘says Michael Yeung from MPE, the lead author of this work.

3D structure of the LHB with colours indicating its temperature. The two surfaces indicate the measurement uncertainty of the LHB extent: the most probable extent most likely lies between the two. The location of the Sun and a sphere of 100 parsec radius are marked for comparison. © Michael Yeung / MPE

eROSITA’s Unparalleled X-ray Observations

The team divided the western Galactic hemisphere into about 2000 regions, and extracted and analysed the spectra from each one. They also leveraged data from ROSAT, the predecessor of eROSITA built also by MPE, which complements the eROSITA spectra at energies lower than 0.2 keV. They found a clear temperature dichotomy in the LHB, with the Galactic South (0.12 keV; 1.4 MK) slightly hotter than the Galactic North (0.10 keV; 1.2 MK). This feature could be explained by the latest numerical simulations of the LHB caused by supernova explosions in the last few million years.

Diffuse X-ray background spectra inform scientists not just of the temperature but also of the 3D structure of the hot gas. Previous work by the same team has established that the density of the LHB is relatively uniform, calibrating the density of the hot gas with sight lines to giant molecular clouds located on the surface of the LHB. Relying on this assumption, they generated a new 3D model of the LHB from the measured intensity of the LHB emission in each sight line. They found the LHB has a larger extent towards the Galactic poles as expected, as the hot gas prefers to expand towards directions of the least resistance, away from the Galactic disc.

‘This is not surprising, as was already found by the ROSAT survey’, pointed out by Michael Freyberg, a core author of this work and was a part of the pioneering work in the ROSAT era three decades ago. ‘What we didn’t know was the existence of an interstellar tunnel towards Centaurus, which carves a gap in the cooler interstellar medium (ISM). This region stands out in stark relief thanks to the much-improved sensitivity of eROSITA and a vastly different surveying strategy compared to ROSAT,’ added Freyberg. The authors of this work suggest the Centaurus tunnel may just be a local example of a wider hot ISM network sustained by stellar feedback across the Galaxy — a popular idea proposed in the 70s that remains difficult to prove.

Temperature map of the LHB in the western Galactic hemisphere in zenithal equal-area projection. The high-latitude region in the northern and southern hemispheres exhibits a clear temperature dichotomy. © Michael Yeung / MPE

A 3D Model of the Solar Neighbourhood

In addition to the 3D LHB model, the team compiled a list of known supernova remnants, superbubbles, and 3D dust information from the literature and created an interactive 3D model of the solar neighbourhood. Some features of the LHB could be easily appreciated from such representation, for instance, the well-known Canis Majoris tunnel on the Galactic disc, possibly connecting the LHB to the Gum nebula or another superbubble (called GSH238+00+09), as well as dense molecular clouds (in orange) lying close to the surface of the LHB in the direction of the Galactic Centre (GC). Recent works found that these clouds possess velocities in the radial direction (away from us). The location and the velocity of the clouds could be explained if they were formed from the condensation of swept-up materials during the early stage of the LHB formation. ‘Another interesting fact is that the Sun must have entered the LHB a few million years ago, a short time compared to the age of the Sun, remarked Gabriele Ponti, a co-author of this work. ‘It is purely coincidental that the Sun seems to occupy a relatively central position in the LHB as we continuously move through the Milky Way.’

3D interactive view of the LHB and the solar neighbourhood

Source: Max Planck Institute for Extraterrestrial Physics (MPE)/News ’

---

Contacts:

Michael Yeung
PhD Student Highenergy-Group
tel:+49 89 30000-3899
mjf@mpe.mpg.de
Max Planck Institute for Extraterrestrial Physics

Dr. Michael Freyberg
Scientist Highenergy Group
tel:+49 89 30000-3849
myeung@mpe.mpg.de
Max Planck Institute for Extraterrestrial Physics

Dr. Gabriele Ponti
Visiting Scientist Highenergy Group
tel:+49 89 30000-3572
ponti@mpe.mpg.de
Max Planck Institute for Extraterrestrial Physics

Dr. Andrea Merloni
Senior Scientist Highenergy Group; PI eROSITA
tel:+49 89 30000-3893
am@mpe.mpg.de
Max Planck Institute for Extraterrestrial Physics

---

Original Publication

M. C. H. Yeung, G. Ponti, M. J. Freyberg et al.
The SRG/eROSITA diffuse soft X-ray background. I. The local hot bubble in the western Galactic hemisphere
A&A, 690, A399

Source

---

Further Information

eROSITA website of the MPE

eROSITA finds hot gas all around the Milky Way – closer than expected

December 14, 2023

A new all-sky map by the eROSITA telescope reveals X-rays emitted by million-degree hot plasma in and around the Milky Way. This discovery sheds light on the shape and size of a large portion of the Milky Way circumgalactic medium, providing a large reservoir of gas to fuel future star formation.

Massive black holes in low-mass galaxies: what happened to the X-ray Corona?

June 11, 2024

Identifying massive black holes in low-mass galaxies is crucial for understanding black hole formation and growth over cosmic time but challenging due to their low accretion luminosities. Astronomers at MPE, led by Riccardo Arcodia, used the eROSITA X-ray telescope's all-sky survey to study massive black hole candidates selected based on variability in other wavelength ranges.

The X-ray sky opens to the world

January 31, 2024
First eROSITA sky-survey data release makes public the largest ever catalogue of high-energy cosmic sources

---

The cosmic-ray ionization rate in the local Milky Way is ten times lower than previously thought

This figure illustrates the spatial distribution of gas density obtained from the high-resolution 3D dust extinction map. Shown is the cross section of one of molecular clouds where the CRIR was measured, the line of sight toward a background star is indicated by the dashed line. The individual pixels reflect the 1-parsec spatial resolution provided by the map. © M. Obolontseva et al.

Shown are re-evaluated values of the CRIR (ζH2 , blue bullets) obtained from the analysis of observations toward different stars (indicated by their HD catalogue numbers), and earlier results for these sight lines. The gray curve represents the CRIR derived from the Voyager data. The horizontal axis indicates the gas column density of molecular clouds where the CRIR was measured. © M. Obolontseva et al.

---

An international group of astrophysicists, led by MPE scientists Marta Obolentseva, Alexei Ivlev, Kedron Silsbee, and Paola Caselli, have revisited the long-standing problem of evaluating the rate at which cosmic rays ionize gas in the interstellar medium. By combining available observational data for diffuse molecular clouds with novel developments in understanding the dust and gas distribution in these regions and applying numerical modeling, the scientists were able to compute the cosmic-ray ionization rate (or its upper limit) for a dozen nearby clouds. They showed that earlier estimates were a factor of ten too high.

Galactic cosmic rays (CRs) play a crucial role in the evolution of molecular clouds, governing multiple physical and chemical processes that accompany practically all stages of star formation. The impact of CRs on these processes is quantified in terms of the CR ionization rate (CRIR), which is the number of ionization events produced by CRs per gas molecule in unit time. The value of this fundamentally important parameter has been debated by the star formation community for over half a century. The principal difficulty here originates from the fact that the CRIR in the interstellar medium is determined by a relatively small population of non-relativistic CRs. In contrast to the well-constrained ultra-relativistic population, there are no robust direct methods to detect such “low-energy” particles in space – nor can they be measured on Earth, because of their efficient exclusion from the heliosphere by the Solar wind.

The only direct method to measure the CR energy spectra and thus to derive the CRIR would be to use spacecraft that are able to reach beyond the heliosphere. Such measurements have indeed been performed a decade ago by the Voyager probes 1 and 2 when they crossed the outmost edge of the heliosphere – the heliopause. Nevertheless, this unique direct sampling of CRs still represents the very local interstellar medium in the immediate proximity of the Sun, at a distance of only about 120 au.

For this reason, indirect methods have been widely used to estimate the CRIR in numerous molecular clouds surrounding us in the Milky Way. Such methods typically rely on measuring light absorption due to specific ions produced by CRs, accumulated along the line of sight that connects the observer to the background star (acting as the emission source). Much attention has been given to absorption observations of H₃⁺ ions (molecular hydrogen, H₂, with an extra proton attached), often considered the most reliable method to measure the CRIR in diffuse molecular clouds – thanks to the particularly simple formation and destruction routes of these ions and the fact that they involve the most abundant molecule in the universe, H₂. It turned out, however, that typical CRIR values inferred from these measurements are more than a factor of ten higher than those derived from the Voyager data!

This dramatic discrepancy has been a major puzzle in the cosmic-ray community over the last decade. At the same time, the so-called 3D dust extinction maps have changed our understanding of the three-dimensional dust and gas distribution in the surrounding molecular clouds. These maps have been constructed using distances to over a billion stars, based on parallax measurements by the Gaia satellite. Recently, the high-resolution maps developed by our neighbors at MPA in the group of Dr. Torsten Enßlin reached sufficient accuracy to allow a reconstruction of the gas distribution down to parsec scales. This breakthrough made it possible to identify the individual clouds where H₃⁺ absorption actually occurred in each observation, and thus to pinpoint precisely the positions of individual CRIR measurements in 3D space.

Motivated by this staggering development, the scientists revisited the analysis of available H₃⁺ observations. They performed 3D simulations of the identified clouds, with the CRIR being the only unconstrained parameter of the model. By comparing their results with observations, this made it possible for the first time to self-consistently reconstruct the physical structure of the individual clouds and derive the respective CRIR.

“One of the astonishing outcomes of our analysis is that the re-evaluated values of CRIR are an order of magnitude lower than the previous estimates, which actually brings our results into agreement with the CR spectrum measured by the Voyager probes”, says Alexei Ivlev, one of the main authors of the study. “While we of course cannot claim the very local Voyager spectrum to be representative of a typical Galactic spectrum of CRs, it is certainly no longer an outlier – as it has been considered for many years.”

“In addition to the impressive results on the CRIR, this work represents a major step forward in the realism of astrochemical modeling. These are the first simulations to incorporate the actual gas density distribution. I anticipate that combining astrochemical simulations with accurate determinations of the density structure and the radiation field will result in many more exciting advances in the coming years”, Kedron Silsbee adds.

The work that has discovered the drastic reduction in the CRIR also led to a remarkable “byproduct” discovery: it was found that all earlier estimates of the gas density in diffuse molecular clouds, where the H₃⁺ measurements are typically conducted, strongly exceed the values derived from the extinction maps. In order to identify the origin of this discrepancy, one of the group’s collaborators, Prof. David Neufeld from the Johns Hopkins University, has revisited the method commonly used to estimate gas densities. This method is based on observations of excited rotational states of molecular carbon (C₂) and therefore depends on the rates of C₂ excitation in collisions with gas molecules. It turned out that the rates assumed for the earlier estimates were considerably lower than the accurate values obtained recently, with the result that the inferred densities were too high. In the companion paper led by David Neufeld, the scientists presented revised gas densities that are now in good agreement with those from the extinction maps.

“Initially, I had been quite skeptical of the lower density estimates that emerged from the dust extinction maps, because they were inconsistent with what we thought we knew. But when I looked more closely at the methods used previously to evaluate the gas density from observations of C₂, I found that they had yielded density estimates that were far too high”, says Neufeld.

Ultimately, the dramatically reduced gas densities as well as the reduction in the CRIR have profound and diverse implications. Not only does this affect the chemical composition of diffuse and translucent molecular clouds, but also changes the evolution of their physical structure, which finally has a broad impact on the initial stages of star formation.

“CRs are fundamental ingredients for the dynamical evolution of interstellar molecular clouds, where stars and planets form, and for chemical evolution in space, where the precursors of pre-biotic molecules form. It is thus crucial for astrophysics and astrochemistry to know the CRIR, making this one of our long-standing scientific goals”, says Paola Caselli, director at the Center for Astrochemical studies at MPE. “I am very proud that our study, also involving scientists from MPA and international colleagues in a truly interdisciplinary effort, has achieved this goal”, she adds.

These studies also have important consequences for all available CRIR measurements utilizing various ionization tracers. The presented results show that a careful re-evaluation of previously published estimates of CRIR in molecular clouds would be useful, in particular by considering the recent revolutionary changes in our understanding of the diffuse gas distribution in the Milky Way.

Source: Max Planck Institute for Extraterrestrial Physics (MPE)/News

---

Contact:

Priv. Doz. Dr. habil. Alexei Ivlev
scientist in CAS group
Tel:++49 89 30000-3356
ivlev@mpe.mpg.de
Max Planck Institute for extraterrestrial Physics , Garching

Marta Obolentseva
PhD-student CAS group
marta@mpe.mpg.de
Max Planck Institute for extraterrestrial Physics

Prof. Dr. Paola Caselli
Director of the CAS group at MPE
Tel:+49 89 30000-3400
Fax:+49 89 30000-3399
caselli@mpe.mpg.de
Max Planck Institute for Extraterrestrial Physics, Garching

---

Original Publications

1. M. Obolentseva, A. Ivlev et al.
Re-evaluation of the cosmic-ray ionization rate in diffuse clouds
The Astrophysical Journal (2024), Vol. 973, A142

DOI

2. D. Neufeld, D. Welty, A. Ivlev et al.
The densities in diffuse and translucent molecular clouds: estimates from observations of C2 and from 3-dimensional extinction maps
The Astrophysical Journal 2024, Vol. 973, A143

DOI

---

Further Information

Cosmic rays in molecular gas
One of the principal aims of the CAS-Theory group is to understand the physics of low-energy CRs in molecular gas, by combining advanced methods of the kinetic theory and plasma physics and applying available observational constraints. More

3. Edenhofer, C. Zucker, P. Fran et al.
A parsec-scale Galactic 3D dust map out to 1.25 kpc from the Sun★
A&A, Vol. 685, A82 (2024)

Source | DOI

JWST sheds Light on the Journey of Cosmic Icy Grains
July 04, 2024

Using the JWST, a team of researchers including Paola Caselli and Michela Giuliano from MPE, have probed deep into dense cloud cores, revealing details of interstellar ice that were previously unobservable. The study focuses on the Chamaeleon I region, using JWST’s NIRCam to measure spectroscopic lines towards hundreds of stars behind the cloud. More

---

JWST sheds Light on the Structure of interstellar Water Ice

Illustration of the various OH bonding scenarios observed in the dark cloud Cha I with JWST. Three spectral features corresponding to three OH bonding environments are revealed in spectra along lines of sight towards Cha I. In the interstellar icy dust grain represented here, each OH bonding environment is represented by a “cutout” in the ice and its corresponding spectral absorption feature indicated. Environment one (right hand side) corresponds to OH stretches of H2O molecules fully bound to neighbouring H2O molecules in the ice, predominantly responsible for the intense H2O absorption feature at ∼3 μm. Environments two (left hand side) and three (centre) correspond to OH stretches of H2O molecules not fully bound to neighbouring water molecules i.e. dangling OH. Environment two (left hand side) illustrates dangling OH in a predominantly water ice environment, but not fully bound to the surrounding water molecules (2.703 μm), while environment three (centre) illustrates dangling OH in interaction with other molecular species in the ice (2.753 μm). This cartoon is intended to be illustrative of the various possible ice environments that contribute to the observed dangling OH absorption features, and we do not sketch the full distribution of chemical composition between grains nor the homogeneity of grains along the observed line of sight. Background image of Cha I. 

 

© NASA, ESA, CSA, and M. Zamani (ESA/Webb); Science: M. K. McClure (Leiden University), F. Sun (Steward Observatory), Z. Smith (Open University), and the Ice Age ERS Team.

---

Using the JWST, a team of researchers including Paola Caselli, Barbara Michela Giuliano and Basile Husquinet from MPE, have probed deep into dense cloud cores, revealing details of interstellar ice that were previously unobservable. The study focuses on the Chamaeleon I region, using JWST’s NIRCam to measure spectroscopic lines toward hundreds of stars behind the cloud. For the first time, weak spectroscopic features known as ‘dangling OH’ have been detected, indicating water molecules are not fully bound in the ice. These features could trace the porosity and modification of icy grains as they evolve from molecular clouds to protoplanetary disks. This discovery enhances our understanding of ice grain structure and its role in planet formation.

Thanks to the unprecedented sensitivity of the JWST, we are able to probe ices deep within dense cloud cores, where extinction is so high that they eluded previous observatories. These lines of sight are the missing link between the initial formation of ices on dust grain surfaces in molecular clouds and the aggregation of icy grains into icy planetesimals, a still little-understood process that occurs in the protoplanetary disk surrounding a new star. Peeking deep into the birthplace of stars will give new clues to these modifications of icy grains.

In the Ice Age program targeting the Chamaeleon I region, a dense cloud region close to us in the Milky Way, observations of the densest part of the cloud with JWST’s NIRCam instrument have allowed simultaneous spectroscopic measurements of lines of sight towards hundreds of stars behind the cloud. The light emitted by these stars interacts with icy grains as it cross the cloud before being captured by the JWST’s large mirror and detected. Up until now, we have been able to measure the major, intense absorption features linked with major species in the ice, namely water, carbon dioxide, carbon monoxide, methanol, and ammonia. Thanks to the large size of the telescope’s mirror, we can now measure much weaker features. In-depth studies of the positions and profiles of weak spectroscopic features reveal some of the physical conditions of the object. Here, we have made the first detection of a particular set of very weak bands linked to only a small fraction of the water molecules in the ice. The spectroscopic features, named ‘dangling OH’ by laboratory astrophysicists who have measured them in laboratory ices for decades, correspond to water molecules that are not fully bound into the ice, and could trace surfaces and interfaces within the icy grains, or when the water is intimately mixed with other molecular species in the ice.

The ‘dangling OH’ features lie in a spectral region that is inaccessible from the ground and so, while they have been actively searched for since the 1990s, the previous space observatories covering that spectral range lacked the combination of spectral resolution and sensitivity required to detect them providing only upper limits. Now in the JWST era, we can use these signatures to trace icy grain modification on the journey to planet formation. It has long been anticipated that, if detected, these signatures could be used to trace the porosity of the ices, i.e. their presence would signal ‘fluffy’ grains with high porosity while their absence would signal compaction and aggregation. Although this simple interpretation remains under debate, the successful detection of these signatures now means that we can search for them in different environments and at different times during the star formation process to determine whether or not they can be used as a tracer of how the ice evolves under different conditions.

"The detection of the water dangling bond feature in the ice mantles demonstrates the importance of laboratory astrophysics to interpret JWST data”, says Barbara Michela Giuliano, one of the authors. “Detailed information on the physical properties of the observed ices still requires extensive support from the laboratory to disentangle the spectral properties observed within dense regions of the interstellar medium and protoplanetary disks. Here at CAS we are happy to provide such support.”, she adds.

“The high sensitivity of JWST, together with impressive advancements in laboratory astrophysics, is finally allowing us to study in detail the physical structure and chemical composition of interstellar ices. This is crucial to provide stringent constraints on chemical/dynamical modeling, needed to reconstruct our astrochemical history, from interstellar clouds to protoplanetary disks to stellar systems like our own. It is exciting to be part of this endeavor.”, says Paola Caselli, who - together with her PhD student Basile Husquinet - also contributed to the paper.

This study shows that, in the cloud, potentially ‘fluffy’ icy grains are present, impacting the chemistry that can occur in these regions and thus the degree of chemical complexity that can build up. The discovery also opens a new window on studying planet formation since, ultimately, these spectral features allow us to build up an idea of the spatial distribution and variation of ices as well as how they evolve on their journey from molecular clouds to protoplanetary disks to planets.

Source: Max Planck Institute for Extraterrestrial Physics (MPE)/News

---

Contact:

Prof. Dr. Paola Caselli
Director of the CAS group at MPE
tel:+49 89 30000-3400
Fax:+49 89 30000-3399
caselli@mpe.mpg.de
Max Planck Institute for Extraterrestrial Physics, Garching

Dr. Barbara Michela Giuliano
scientist in CAS group
tel:+49 89 30000-3317
giuliano@mpe.mpg.de
Max Planck Institute for Extraterrestrial Physics

Basile Husquinet
PhD-student CAS group
tel:+49 89 30000-3553
bhusquin@mpe.mpg.de
Max Planck Institute for Extraterrestrial Physics

---

Original Publication

Noble et al.
Detection of the elusive dangling OH ice features at ∼ 2.7 μm in Chamaeleon I with JWST NIRCam.
Nature Astronomy 2024

Source

---

Further Information

Webb Finds Plethora of Carbon Molecules Around Young Star

An international team of astronomers have used the NASA/ESA/Webb James Webb Space Telescope to study the disc around a young and very low-mass star. The results reveal the richest hydrocarbon chemistry seen to date in a protoplanetary disc (including the first extrasolar detection of ethane) and contribute to our evolving understanding of the diversity of planetary systems. (June 07, 2024)

---

Massive black holes in low-mass galaxies: what happened to the X-ray Corona?

Two examples of X-ray-detected MBH candidates. On the top we show the eROSITA eRASS-4 X-ray images centered at the input optical coordinates, while on the bottom the optical image with overlayed X-ray contours. For the vast majority of MBH candidates, X-ray counterparts such those shown here were not found. © Legacy Surveys/D. Lang (Perimeter Institute); R. Arcodia.

Illustration of accretion disk corona.
Nahks Tr'Ehnl and Niel Brandt, Penn State University

---

Identifying massive black holes in low-mass galaxies is crucial for understanding black hole formation and growth over cosmic time but challenging due to their low accretion luminosities. Astronomers at MPE, led by Riccardo Arcodia, used the eROSITA X-ray telescope's all-sky survey to study massive black hole candidates selected based on variability in other wavelength ranges. Surprisingly, despite being flagged as accreting MBHs, the X-rays were weak and didn't match predictions from more massive AGN scaling relations. This discrepancy suggests either the absence of a canonical X-ray corona or the presence of unusual accretion modes and spectral energy distributions in these dwarf galaxy MBHs.

The centre of the Milky Way harbours a supermassive black hole – as do basically all galaxies of similar size and bigger than our Milky Way. But what about small galaxies? There is a hot debate in the astronomy community on whether all, or only some, low-mass galaxies are populated by “massive black holes”, anything between a few thousands to a few million solar masses. If these could be found and analysed, we could also learn something about the galaxies in the early Universe and how black holes grow over cosmic times, as the local dwarf galaxies closely resemble these first galaxies. So far, about 500 massive black holes have been found in the nearby Universe, as they need to be active and luminous enough to discern emission from their immediate vicinity from the host galaxy’s overall emission.

A team of astronomers has now used the all-sky survey with the eROSITA X-ray telescope to study massive black hole candidates selected by their variability in other wavelength ranges. “The variability at optical or infrared wavelengths indicates that there is some activity in the galactic nucleus. So, if there is a massive black hole accreting material, it should emit X-rays,” explains Riccardo Arcodia, who led the study at the Max Planck Institute for Extraterrestrial Physics (MPE) and is now working at the MIT Kavli Institute for Astrophysics and Space Research.

The only selection criterion for the sample was a cut on stellar mass to single out low-mass galaxies, leading to about 200 sources/MBHs. The team then looked for X-ray emission at the positions of these galaxies in the eROSITA all-sky survey and found only 17 sources, four of which had never been seen in X-rays before.

“The predicted X-ray luminosity of most of these candidates should be well above the detection limit of the eROSITA all-sky survey,” points out Andrea Merloni, eROSITA’s principal investigator. “Moreover, our stacking analysis of the non-detected sources shows that their emission is consistent with predictions for the X-ray emission of the galaxy alone.” While a possible X-ray weakness of massive black holes in dwarf galaxies was reported before for a few cases, this is the first confirmation on a large sample of homogeneous X-ray observations.

This means that the massive black holes in dwarf galaxies most likely behave differently than their supermassive counterparts. High-energy X-rays are typically produced in a region of hot plasma in the immediate vicinity of the black hole called the corona. In low-mass galaxies, the gravitational pull towards the centre is less strong and their interstellar medium is clumpier than in more massive ones, which might lead to differences in the magnetic field or the interplay between the accretion disk and the black hole corona. “This could be the reason why a classical corona was not found in these low-mass black holes”, says first author Riccardo Arcodia. “A different accretion mode in low-mass galaxies would also imply that selection techniques at different wavebands do not offer the same agreement seen at higher masses”, he adds. Future multi-wavelength studies on large samples are needed to test whether this is the case, or whether the X-ray emission alone is unusually low.

“This work serves as a pilot study for future synergies between eROSITA and VRO/LSST, which will perform a 10-year optical survey of the southern sky,” explains Mara Salvato, eROSITA Spokesperson and chair of the eROSITA followup working group. “We expect to find hundreds of LSST’s massive black hole candidates in eROSITA data, and hopefully learn a lot more about what is going on with the less-massive black holes at the centers of dwarf galaxies.”

Source: Max Planck Institute for Extraterrestrial Physics/News

---

Contact:

Riccardo Arcodia
Postdoc
tel:+49 (0)89 30000-3643
arcodia@mpe.mpg.de
Max Planck Institute for Extraterrestrial Physics, Garching

Dr. Andrea Merloni
tel:+49 89 30000-3893
am@mpe.mpg.de

Max Planck Institute for Extraterrestrial Physics, Garching

---

Original Publication

R. Arcodia, A.Merloni, J.Comparat et al
O Corona, where art thou? eROSITA’s view of UV-optical-IR variability-selected massive black holes in low-mass galaxies.
A&A, 681, A97 (2024)
Source | DOI

---

Further Information

eROSITA witnesses the awakening of massive black holes
April 29, 2021

Using the SRG/eROSITA all-sky survey data, scientists at the MPE have found two previously quiescent galaxies that now show quasi-periodic eruptions.

more

The X-ray sky opens to the world
January 31, 2024
First eROSITA sky-survey data release makes public the largest ever catalogue of high-energy cosmic sources

more

---

ESA's Euclid celebrates first science with sparkling cosmic views

This image of the spiral galaxy NGC 6744 is released as part of the Early Release Observations from ESA’s Euclid space mission. It’s a typical example of the type of galaxy currently forming most of the stars in the nearby Universe, making it a wonderful archetype to study with Euclid. © Credit: ESA/Euclid/Euclid Consortium/NASA, image processing by J.-C. Cuillandre (CEA Paris-Saclay), G. Anselmi; CC BY-SA 3.0 IGO or ESA Standard Licence.

In this image the faint diffuse emission around the center of the Perseus galaxy cluster has been highlighted in black and white. Even though this ‘intra-cluster light’ is much fainter than the bright cluster galaxies it contributes 20% to the overall luminosity. © Euclid consortium, MPE

Some dwarf galaxies survive the strong tidal forces in the Perseus galaxy cluster, shown here as zoom-ins. In total, the Euclid researchers found 1100 dwarf galaxies, many are much fainter than ever seen before in the Perseus galaxy cluster. © Euclid consortium, LMU, MPE

---

Analysis of the early release observations provides insights into the evolution of the Perseus galaxy cluster

Today, ESA’s Euclid space mission releases five unprecedented new views of the Universe. The never-before-seen images demonstrate Euclid’s ability to unravel the secrets of the cosmos and enable scientists to hunt for rogue planets, use lensed galaxies to study mysterious matter, and explore the evolution of the Universe. The new images accompany the mission’s first scientific data, also made public today, and several science papers, including one led by the Max Planck Institute for Extraterrestrial Physics in Garching, with an unprecedented analysis of the faint intra-cluster light of the Perseus cluster of galaxies.

The full set of Euclid’s early observations targeted 17 astronomical objects, from nearby clouds of gas and dust to distant clusters of galaxies, ahead of Euclid’s main survey. Euclid will trace the hidden web-like foundations of the cosmos, map billions of galaxies across more than one-third of the sky, explore how our Universe formed and evolved over cosmic history, and study the most mysterious of its fundamental components: dark energy and dark matter.

While visually stunning, the images are far more than beautiful snapshots; they reveal new physical properties of the Universe thanks to Euclid’s novel and unique observing capabilities. These scientific secrets are detailed further in a number of accompanying papers released by the Euclid collaboration, together with five key reference papers about the Euclid mission (see link to the ESA press release on the left). Euclid produced this early catalogue in just a single day, revealing over 11 million objects in visible light and 5 million more in infrared light.

Euclid’s image of the Perseus cluster of galaxies was published as one of the first images of the space telescope, just six months ago. Perseus is one of the most spectacular objects in our cosmic neighborhood: It is located at a distance of “only” 240 million light years (at a redshift of z = 0.018) and is the brightest X-ray cluster. With its high total mass of 650 trillion solar masses, its gravity ties thousands of galaxies together.

For the first time, a team led by the Max Planck Institute for Extraterrestrial Physics (MPE) has now been able to analyze the diffuse light from the Perseus galaxy cluster to far-out regions. “The high sensitivity at optical and near-infrared wavelengths over a huge field of view allows us to capture the extended faint light in the Perseus cluster,” says Matthias Kluge, lead author of the study, which is now being published together with 14 other papers. “This light is more than 100,000 times fainter in the infrared than the darkest night sky on Earth. Nevertheless, due to its large volume, it accounts for about 20% of the luminosity of the entire cluster.”

In addition, the team also used Euclid's excellent visible light imaging capabilities - comparable to the Hubble Space Telescope - to detect 50,000 free-flying globular clusters. The characteristics of the globular clusters and the bluish color of the diffuse light indicate their common origin: On the one hand, they originate from the low-metallicity outer regions of massive cluster galaxies that have been stripped away by the tidal forces of the cluster. On the other hand, there is an increasing contribution of dwarf galaxies, which were also completely torn apart by the strong tidal forces, with increasing distance from the cluster center.

In a further study, numerous surviving dwarf galaxies were detected in the Perseus cluster. Raphael Zöller from MPE and LMU was significantly involved in the measurements: “Euclid is located at the second Lagrange point far outside the Earth's atmosphere. Thanks to the dark image background, the excellent image resolution and the large field of view, we were able to detect 1100 dwarf galaxies, including hundreds with much fainter luminosity than ever before in the Perseus galaxy cluster.”

Background information

Euclid is a space mission of the European Space Agency (ESA) with contributions from the National Aeronautics and Space Administration (NASA). It is the second M-class mission in ESA's Cosmic Vision programme.

VIS and NISP were developed and built by a consortium of scientists and engineers from 17 countries, many from Europe, but also from the USA, Canada and Japan. From Germany, the Max Planck Institute for Astronomy (MPIA) in Heidelberg, the Max Planck Institute for Extraterrestrial Physics (MPE) in Garching, the Ludwig Maximilian University (LMU) in Munich, the University of Bonn (UB), the Ruhr University Bochum (RUB) and the German Space Agency at the German Aerospace Centre (DLR) in Bonn are participating. As partner of the Euclid project, MPE is responsible for the optical components of the NISP instrument as well as for the optical design and modelling of the image quality and is hosting one of Euclid's nine Science Data Centers.

The German Space Agency at DLR coordinates the German ESA contributions and also provides funding of 60 million euros from the National Space Programme for the participating German research institutes.

With around 21%, Germany is the largest contributor to the ESA science programme.

Source: Max Planck Institute for Extraterrestrial Physics (MPE)

---

Contacts:

Matthias Kluge
postdoc
tel:+49 89 30000-3576
fax:+49 89 30000-
mkluge@mpe.mpg.de

Raphael Zöller
phd student
fax:+49 89-
rzoeller@mpe.mpg.de

Ralf Bender
director
tel:+49 89 30000-3702
fax:+49 89 30000-3351
bender@mpe.mpg.de

---

Original publications with main contributions from authors at MPE

(public on 24.05.2024)

1. M. Kluge et al.
Euclid: Early Release Observations – The intracluster light and intracluster globular clusters of the Perseus cluster
submitted

Source

2. Marleau et al.
Euclid: Early Release Observations – Dwarf galaxies in the Perseus galaxy cluster
submitted

Source

3. Cuillandre et al.
Euclid: Early Release Observations – Programme overview and pipeline for compact- and diffuse-emission photometry
submitted

Source

4. Cuillandre et al.

Euclid: Early Release Observations – Overview of the Perseus cluster and analysis of its luminosity & stellar mass functions submitted

Source:

5. Atek et al.
Euclid: Early Release Observations – A preview of the Euclid era through a magnifying lens
submitted

Source

---

More Information

Euclid @ MPE

Information on Euclid at ESA

ESA's Euclid celebrates first science with sparkling cosmic views

ESA Press Release with further images, information and Iinks

LMU Press Release

---

Weighing a Black Hole in the early universe

Illustration of the GRAVITY+ observations of a quasar in the early universe. The background image shows the evolution of the universe since the Big Bang, with the quasar J0920 (artist’s impression) at a lookback time of 11 billion years. The observations now were possible by combining all four VLT telescopes to obtain velocity measurements of matter close to the central, supermassive black hole. © T. Shimizu; background image: NASA/WMAP; quasar illustration: ESO/M. Kornmesser; VLT array: ESO/G. Hüdepohl.

With the upgraded GRAVITY-instrument at the ESO VLTI, a team of astronomers led by the Max Planck Institute for Extraterrestrial Physics has determined the mass of a Black Hole in a galaxy only 2 billion years after the Big Bang. With 300 million solar masses, the black hole is actually under-massive compared to the mass of its host galaxy, indicating that at least for some systems there might be a delay between the growth of the galaxy and its central black hole.

In the more local universe, astronomers have observed tight relationships between the properties of galaxies and the mass of the supermassive black holes residing at their centers, suggesting that galaxies and black holes co-evolve. A crucial test would be to probe this relationship at early cosmic times, but for these far-away galaxies traditional direct methods of measuring the black hole mass are either impossible or extremely difficult. Even though these galaxies often shine very brightly (they were dubbed “quasars” or “quasi-stellar objects” when they were first discovered in the 1950s), they are so far away that they cannot be resolved with most telescopes.

“In 2018, we did the first breakthrough measurements of a quasar’s black hole mass with GRAVITY,” says Taro Shimizu, staff scientist at MPE and the corresponding author of the new study now published in Nature. “This quasar was very nearby, however. Now, we have pushed all the way out to a redshift of 2.3, corresponding to a lookback time of 11 billion years.” GRAVITY+ now opens a new and precise way to study black hole growth at this critical epoch, often called “cosmic noon”, when both black holes and galaxies were rapidly growing.

“This is really the next revolution in astronomy – we can now get images of black holes in the early universe, 40 times sharper than possible with the James Webb telescope,” points out Frank Eisenhauer, the MPE director who leads the group developing the GRAVITY instrument and the GRAVITY+ improvements.

GRAVITY combines all four 8-metre-telescopes of the ESO Very Large Telescope interferometrically, essentially creating one giant virtual telescope with a diameter of 130 metres. With the latest upgrades using a new wide-field, off-axis fringe-tracking mode, GRAVITY-Wide was now able to observe the central region of the galaxy SDSS J092034.17+065718.0, one of the most luminous quasars in the early universe.

The team was able to spatially resolve the so-called ‘broad line region’, observing the motion of gas clouds around the central black hole as they rotate in a thick disk. This allows a direct, dynamical measurement of the mass of the black hole. With 320 million solar masses, the black hole mass turns out to be actually underweight compared to its host galaxy which has a mass of about 60 billion solar masses. This suggests that the host galaxy grew faster than the supermassive black hole, indicating a delay between galaxy and black hole growth for some systems.

“The likely scenario for the evolution of this galaxy seems to be strong supernova feedback, where these stellar explosions expel gas from the central regions before it can reach the black hole at the galactic center,” says Jinyi Shangguan, postdoc in the MPE IR group. “The black hole can only start to grow rapidly – and to catch up to the galaxy’s growth overall – once the galaxy has become massive enough to retain a gas reservoir in its central regions even against supernova feedback.” To determine whether this scenario is also the dominant mode of the co-evolution for other galaxies and their central black holes, the team will follow-up with more high-precision mass measurements of black holes in the early universe are needed. Stay tuned for more quasar observations with GRAVITY+!

Source: Max Planck Institute for Extraterrestrial Physics/Press Releases

---

Contact:

Taro Shimizu
scientist
+49 89 30000-3392
+49 89 30000-3569
shimizu@mpe.mpg.de

Frank Eisenhauer
director
+49 89 30000-3100
+49 89 30000-3102
eisenhau@mpe.mpg.de

Hannelore Hämmerle
press officer
+49 89 30000-3980
+49 89 30000-3569
hanneh@mpe.mpg.de

---

Original publication 

Abuter, Allouche, Amorim, et al.
A dynamical measure of the black hole mass in a quasar 11 billion years ago
Nature, 29 January 2024

Source

---