Category Archives: Cosmology

Mapping the Local Cosmic Web (Cosmology)

Dark matter map reveals hidden bridges between galaxies

A new map of dark matter in the local universe reveals several previously undiscovered filamentary structures connecting galaxies. The map, developed using machine learning by an international team including a Penn State astrophysicist, could enable studies about the nature of dark matter as well as about the history and future of our local universe.

Dark matter is an elusive substance that makes up 80% of the universe. It also provides the skeleton for what cosmologists call the cosmic web, the large-scale structure of the universe that, due to its gravitational influence, dictates the motion of galaxies and other cosmic material. However, the distribution of local dark matter is currently unknown because it cannot be measured directly. Researchers must instead infer its distribution based on its gravitational influence on other objects in the universe, like galaxies.

“Ironically, it’s easier to study the distribution of dark matter much further away because it reflects the very distant past, which is much less complex,” said Donghui Jeong, associate professor of astronomy and astrophysics at Penn State and a corresponding author of the study. “Over time, as the large-scale structure of the universe has grown, the complexity of the universe has increased, so it is inherently harder to make measurements about dark matter locally.”

Previous attempts to map the cosmic web started with a model of the early universe and then simulated the evolution of the model over billions of years. However, this method is computationally intensive and so far has not been able to produce results detailed enough to see the local universe. In the new study, the researchers took a completely different approach, using machine learning to build a model that uses information about the distribution and motion of galaxies to predict the distribution of dark matter.

The researchers built and trained their model using a large set of galaxy simulations, called Illustris-TNG, which includes galaxies, gasses, other visible matter, as well as dark matter. The team specifically selected simulated galaxies comparable to those in the Milky Way and ultimately identified which properties of galaxies are needed to predict the dark matter distribution.

“When given certain information, the model can essentially fill in the gaps based on what it has looked at before,” said Jeong. “The map from our models doesn’t perfectly fit the simulation data, but we can still reconstruct very detailed structures. We found that including the motion of galaxies–their radial peculiar velocities–in addition to their distribution drastically enhanced the quality of the map and allowed us to see these details.”

The research team then applied their model to real data from the local universe from the Cosmicflow-3 galaxy catalog. The catalog contains comprehensive data about the distribution and movement of more than 17 thousand galaxies in the vicinity of the Milky Way–within 200 megaparsecs. The resulting map of the local cosmic web is published in a paper appearing online May 26 in the Astrophysical Journal.

The map successively reproduced known prominent structures in the local universe, including the “local sheet”–a region of space containing the Milky Way, nearby galaxies in the “local group,” and galaxies in the Virgo cluster–and the “local void”–a relatively empty region of space next to the local group. Additionally, it identified several new structures that require further investigation, including smaller filamentary structures that connect galaxies.

“Having a local map of the cosmic web opens up a new chapter of cosmological study,” said Jeong. “We can study how the distribution of dark matter relates to other emission data, which will help us understand the nature of dark matter. And we can study these filamentary structures directly, these hidden bridges between galaxies.”

For example, it has been suggested that the Milky Way and Andromeda galaxies may be slowly moving toward each other, but whether they may collide in many billions of years remains unclear. Studying the dark matter filaments connecting the two galaxies could provide important insights into their future.

“Because dark matter dominates the dynamics of the universe, it basically determines our fate,” said Jeong. “So we can ask a computer to evolve the map for billions of years to see what will happen in the local universe. And we can evolve the model back in time to understand the history of our cosmic neighborhood.”

The researchers believe they can improve the accuracy of their map by adding more galaxies. Planned astronomical surveys, for example using the James Web Space Telescope, could allow them to add faint or small galaxies that have yet to be observed and galaxies that are further away.

In addition to Jeong, the research team includes Sungwook Hong at the University of Seoul/Korea Astronomy and Space Science Institute in Korea, Ho Seong Hwang at the Seoul National University in Korea, and Juhan Kim at the Korea Institute for Advanced Study.

This research was supported in part by the National Research Foundation of Korea funded by the Korean Ministry of Education, the Korean Ministry of Science, the U.S. National Science Foundation, the U.S. National Aeronautics and Space Administration Astrophysics Theory program, and the Center for Advanced Computation at the Korea Institute for Advanced Study.

Featured image: An international team of researchers has produced a map of the dark matter within the local universe, using a model to infer its location due to its gravitational influence on galaxies (black dots). These density maps–each a cross section in different dimensions–reproduce known, prominent features of the universe (red) and also reveal smaller filamentary features (yellow) that act as hidden bridges between galaxies. The X denotes the Milky Way galaxy and arrows denote the motion of the local universe due to gravity. © Hong et. al., Astrophysical Journal


Provided by Penn State

Does The Milky Way Move Like A Spinning Top? (Cosmology)

An investigation carried out by the astrophysicists of the Instituto de Astrofísica de Canarias (IAC) Žofia Chrobáková, a doctoral student at the IAC and the University of La Laguna (ULL), and Martín López Corredoira, questions one of the most interesting findings about the dynamics of the Milky Way in recent years: the precession, or the wobble in the axis of rotation of the disc warp is incorrect. The results have just been published in The Astrophysical Journal.

The Milky Way is a spiral galaxy, which means that it is composed, among other components, of a disc of stars, gas and dust, in which the spiral arms are contained. At first, it was thought that the disc was completely flat, but for some decades now it is known that the outermost part of the disc is distorted into what is called a “warp”: in one direction it is twisted upwards, and in the opposite direction downwards. The stars, the gas, and the dust are all warped, and so are not in the same plane as the extended inner part of the disc, and an axis perpendicular to the planes of the warp defines their rotation.

In 2020, an investigation announced the detection of the precession of the warp of the Milky Way disc, which means that the deformation in this outer region is not static, but that just like a spinning top the orientation of its axis is itself rotating with time. Furthermore, these researchers found that it was quicker than the theories predicted, a cycle every 600-700 million years, some three times the time it takes the Sun to travel once round the centre of the Galaxy.

Precession is not a phenomenon which occurs only in galaxies, it also happens to our planet. As well as its annual revolution around the Sun, and its rotation period of 24 hours, the axis of the Earth precesses, which implies that the celestial pole is not always close to the present pole star, but that (as an example) 14,000 years ago it was close to the star Vega.

Now, a new study by Žofia Chrobáková and Martín López Corredoira has taken into account the variation of the amplitude of the warp with the ages of the stars. The study concludes that, using the warp of the old stars whose velocities have been measured, it is possible that the precession can disappear, or at least become slower than what is presently believed. To arrive at this result the researchers have used data from the Gaia Mission of the European Space Agency (ESA), analysing the positions and velocities of hundreds of millions of stars in the outer disc.

“In previous studies it had not been noticed”, explains Žofia Chrobáková, a predoctoral  researcher at the IAC and the first author of the article, “that the stars which are a few tens of millions of years old, such as the Cepheids, have a much larger warp than that of the stars visible with the Gaia mission, which are thousands of millions of years old”.

“This does not necessarily mean that the warp does not precess at all, it could do so, but much more slowly, and we are probably unable to measure this motion until we obtain better data”, concludes Martín López Corredoira, and IAC researcher and co-author of the article.

Article: Žofia Chrobáková & Martín López Corredoira. “A case against a significant detection of precession in the Galactic warp”. The Astrophysical Journal. DOI: https://iopscience.iop.org/article/10.3847/1538-4357/abf356

– Arxiv: https://arxiv.org/abs/2105.04348

Featured image: Graphic representation of the precessing warp of the Milky Way disc. Credit: Gabriel Pérez Díaz, SMM (IAC).


Provided by IAC

Are You From The Solar District If … (Cosmology)

A catalog to be released on Astronomy & Astrophysics – compiled also taking into account the most recent data collected by the Gaia space mission of ESA – lists the main objects present within a radius of 10 parsecs (30 light years) from the Sun: 541 stars, dwarfs brunettes and exoplanets spread over 339 star systems

Who are our neighbors in the solar system? To answer this, a team of researchers led by astrophysics Céline Reylé of the French CNRS has ideally traced a sphere with the Sun in the center and a radius of 10 parsecs – corresponding to about 30 light years, therefore a volume of just over a hundred thousand light years. cubes. And consulting the astronomical catalogs he compiled a list of all the main objects present in it. Result: 373 stars (including twenty white dwarfs), about ninety brown dwarfs and about eighty exoplanets. For a total of 541 objects distributed in 339 star systems – many of them with two or more stars.

The new list, illustrated in an article to be published in Astronomy & Astrophysics , in addition to the data already present in the literature, also takes into account – for about two thirds of the stars – the high-precision photometric and astrometric measurements provided by the recent Gaia Early Data Release 3 . A complete census of known objects within a radius of 10 parsecs, therefore, which also includes parameters such as the spectral class and the radial velocity of the stars, as well as a list of references to facilitate future studies.

“This sample represents a cardinal point for many areas of star and galactic research. At the lowest level, ”observes Richard Smart, researcher at INAF in Turin and co-author of the study, «any model or process proposed must be able to describe the local population». With its 541 objects, the catalog highlights the richness and variety of our “solar quarter” – populated by stars of very different types, masses, sizes, temperatures and ages. Objects that are mostly stars – largely red dwarfs (61 percent), the most common type of star in the Milky Way – but also, in surprising numbers, brown dwarfs and exoplanets. This updated census also shows a percentage of 28 percent of multiple systems – therefore formed by more than one object.

Animated gif with all objects within 10 parsecs (click to enlarge). Credits: galaxymap.org (on Twitter: @galaxy_map)

Thanks to their proximity, and therefore to the possibility of precise observations, the stars closest to us constitute a unique laboratory for understanding stellar physics and the galaxy. By reporting the current state of our knowledge of the solar quarter and providing reference stars that can be used as calibration samples for detailed observations with current and future instruments, this list has great potential for professional astronomers, but also for amateur astronomers and the general public. .

Finally, the study takes into consideration how the list could evolve with the entry into operation of the great space and ground-based telescopes of the future. “Between reality and science fiction, the exoplanetary systems closest to the Sun will be the highest-profile targets for the research, with future tools, of biomarkers in their atmospheres”, concludes another of the study’s co-authors, Alessandro Sozzetti of INAF of Turin. . “And they could one day become the first destinations of future human interstellar travel.”

Featured image: Zoomable map (click to access) of objects within 10 parsecs. Credits: galaxymap.org (on Twitter: @galaxy_map)


To know more:

  • Read on Astronomy & Astrophysics the article ” The 10 parsec sample in the Gaia era “, by Céline Reylé, Kevin Jardine, Pascal Fouqué, Jose A. Caballero, Richard L. Smart and Alessandro Sozzetti

Provided by INAF

There is Ethanolamine in the Heart of the Milky Way (Cosmology)

An international group of astrochemists has discovered the presence of ethanolamine, a molecular species involved in the formation of cell membranes, in an interstellar cloud of our galaxy. The abundance of ethanolamine with respect to water detected in the interstellar medium shows that this molecule formed in space and that it was probably transported to Earth subsequently with meteorite impacts

Using the Spanish radio telescopes Iram of 30 meters and Yebes of 40 meters, a group of researchers led by Víctor M. Rivilla , of the Centro de Astrobiología ( Cab, Csic-Inta) d i Madrid and associated with Inaf, has identified an additional prebiotic molecule – in addition to those already known – in the interstellar cloud G + 0.693-0.027, located in the heart of the Milky Way about 30 thousand light years from Earth. This is the chemical compound called ethanolamine ( NH 2 CH 2 CH 2 OH), the simplest “head” of phospholipids, that is, the building blocks of cell membranes that may have given rise to life on Earth. The results of the study were published in the journal Proceedings of the National Academy of Sciences and “indicate that ethanolamine forms efficiently in interstellar space, specifically in molecular clouds where new stars and planetary systems are born,” explains Rivilla, the first author of the article.

The emergence of cell membranes represents a crucial step in the origin and early evolution of life on Earth , as they hold together the genetic material and the metabolic system. The origin of these molecules, however, is still an enigma today. The abundance of ethanolamine with respect to water found in the interstellar medium (the “reservoir” that powers the formation of stars and planets in the Universe) shows that this molecule formed in space and was probably transported to Earth subsequently. 

“We know that a large repertoire of prebiotic molecules may have been delivered to the early Earth through the bombardment of comets and meteorites,” says Izaskun Jiménez-Serra , one of the work’s co-authors and researcher at the CAB (Csic-Inta). “We estimate that around one million billion liters of ethanolamine may have been transported to primitive Earth by meteorite impacts. The volume is equal to all the water present in Lake Victoria, the largest African lake by extension, ”adds Jiménez-Serra.

Experiments simulating the chemical constraints of the primitive Earth confirm that ethanolamine could have produced phospholipids in those early stages. Carlos Briones , a biochemist from Cab (Csic-Inta) and co-author of the paper, comments: ‘The availability of ethanolamine on primitive Earth, along with amphiphilic fatty acids or alcohol, may have contributed to the assembly and early evolution of cell membranes. primordial and this would have important implications not only for the study of the origin of life on Earth, but also on other habitable planets and satellites in the Universe ».

This molecule on Earth is a noxious and irritating colorless liquid with an ammonia-like odor. Transformed into other compounds, it functions as a cleaning agent in the surfactant category, and is also used in personal care products and cosmetics.

The hunt for new prebiotic molecules in the interstellar medium does not stop there. “Thanks to the improved sensitivity of the current and next generation of radio telescopes, we will be able to detect molecules of increasing complexity in space, direct precursors of the three fundamental components of life: lipids (which form membranes), nucleotides of Rna and DNA (which contain genetic information), and proteins (which are responsible for metabolic activity), ”Rivilla emphasizes. “Are there these prebiotic seeds distributed all over the Galaxy, and also in other galaxies? We will know relatively soon », he concludes.

Featured image: Graphical representation of the chemical compound called ethanolamine (NH2CH2CH2OH), the simplest head of phospholipids, building blocks of cell membranes. The molecule was identified in the molecular cloud G + 0.693-0.027, located in the center of the Milky Way. Credits: Víctor M. Rivilla & Carlos Briones (Centro de Astrobiología, Csic-Inta) / Nasa Spitzer Space Telescope, Irac4 camera (8 micron)

To know more:

  • Read on Proceedings of the National Academy of Sciences the article ” Discovery in space of ethanolamine, the simplest phospholipid head group ” , by Víctor M. Rivilla, Izaskun Jiménez-Serra, Jesús Martín-Pintado, Carlos Briones, Lucas F. Rodríguez- Almeida, Fernando Rico-Villas, Belén Tercero, Shaoshan Zeng, Laura Colzi, Pablo de Vicente, Sergio Martín and Miguel Requena-Torres, was published in the magazine 

Provided by INAF

Is there Another Solution To S8 Tension? (Cosmology)

Matteo lucca proposed dark energy-dark matter interactions as a possible solution to the S8 tension

Matteo Lucca investigated dark energy-dark matter interaction as a possible solution to the S8 tension. In particular, in order to address S8 tension, he proposed a scenario in which dark energy is a dynamical fluid, whose energy density can be transferred to the dark matter via a coupling function proportional to the energy density of the dark energy. Their study recently appeared in Arxiv.

Not just dark energy-dark matter interaction, several researchers also considered dark matter-dark energy interaction scenario. But, the cosmological features of both interactions are diametrically differ from each other depending on whether the energy density is flowing from the DE to the DM or vice versa.

In dark energy-dark matter interaction (iDEDM), because of the additional energy injected from the DE into the DM over the cosmic history, there has an overall suppression of the DM energy density with respect to the ΛCDM scenario. As a consequence, this results on the one hand in a decreased value of the Hubble parameter at late times, worsening the Hubble tension, and on the other hand in a delay of the radiation-matter equality from which follows a suppression of the matter power spectrum, which can alleviate the S8 tension. The opposite is true for the dark matter-dark energy interaction (iDMDE) case.

For these reasons, great attention has been dedicated to the iDMDE model in the context of the Hubble tension, although it has been explicitly shown by Lucca and Hooper in their previous study that, also this particular interacting DE scenario is unable to address the Hubble tension due to the no-go theorem that arises when Baryon Acoustic Oscillation (BAO) and SNIa data are accounted for. However, surprisingly, to his knowledge the iDEDM scenario has never been thoroughly investigated as a possible solution to the S8 tension. Thus, this inspired him to undertake this task in this study.

He found that, against data from Planck, BAO and Pantheon, the model

  • can significantly reduce the significance of the tension,
  • does so without exacerbating nor introducing any other tension (such as the H0 tension) and,
  • without worsening the fit to the considered data sets with respect to the ΛCDM model.

He also tested the model against data from weak lensing surveys such as KiDS and DES, and found that the model’s ability to address the S8 tension further improves, without a significant impact on any other parameter nor statistical measure.


Reference: Matteo Lucca, “Dark energy-dark matter interactions as a solution to the S8 tension”, Arxiv, pp. 1-7, 2021. https://arxiv.org/abs/2105.09249


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What Leads To Pair Production Process In Pulsar’s Magnetospheres? (Cosmology)

Zaza Osmanov and his collaborators studied the possibility of efficient pair production in a pulsar’s magnetosphere. They showed that, the electrostatic field exponentially amplifies, by means of the relativistic centrifugal force. As a result, the field approaches to Schwinger limit¹, leading to pair creation process in the light cylinder (LC) area². Their study recently appeared in Arxiv.

In 1969, Thomas Gold suggested that, since pulsars are rotating neutron stars, centrifugal effects might be very important. This is because, these can energise the pulsar’s magnetospheric particles to energies enough for producing high energy electromagnetic radiation.

Later, it has been shown by Z. Osmanov and colleagues that the centrifugal force in the LC area is different for different species of particles (magnetospheric electrons and positrons). This in turn, might lead to charge separation creating the Langmuir waves. On the other hand, since the centrifugal force is time dependent, it acts as a parameter, amplifying the electrostatic field, and after it inevitably reach the Schwinger limit, it results in a pair production process.

Now, Z. Osmanov and his collaborators, studied this completely new mechanism of pair creation in the pulsar magnetosphere.

“We consider the normal period pulsars and study the possibility of pair production by means of the centrifugally driven electrostatic fields.”, told Z. Osmanov, professor at Free University of Tbilisi and lead author of the study.

Considering the typical pulsar parameters they showed that the electric field exponentially increases and gradually reaches the Schwinger limit, when efficient pair creation might occur.

They also analysed constraints imposed on the process and found that the process is so efficient that the number density of electron-positron pairs exceeds the Goldreich-Julian density by five orders of magnitude.

In addition, it has been shown that, this novel mechanism of pair production not only changes the number density of electron-positron plasmas in pulsar’s magnetospheres but also, it significantly influences the physical processes there. In particular, it is evident that the processes of particle acceleration strongly depends on the plasma density.

Finally, they showed that, the emission spectral pattern will be influenced as well by the efficient pair creation. This in turn, might give rise to coherent radio emission, which seems to be quite promising in the light of modern enigma – fast radio bursts.

“Since all these problems are beyond the intended scope of the paper we are going to consider them very soon.”, concluded authors of the study.


Note:
1) Schwinger limit is a scale above which the electrostatic field is expected to become nonlinear.
2) Light Cylinder area is a hypothetical area where the linear velocity of rotation coincides with the speed of light.


Reference: Z. Osmanov, G. Machabeli, N. Chkheidze, “The novel mechanism of pair creation in pulsar magnetospheres”, Arxiv, pp. 1-5, 2021. https://arxiv.org/abs/2105.09351


Note for editors of other websites: To reuse this article fully or partially kindly give credit either to our author/editor S. Aman or provide a link of our article

Milky Way Not Unusual, Astronomers Find (Cosmology)

Detailed cross-section of another galaxy reveals surprising similarities to our home

The first detailed cross-section of a galaxy broadly similar to the Milky Way, published today, reveals that our galaxy evolved gradually, instead of being the result of a violent mash-up. The finding throws the origin story of our home into doubt.

The galaxy, dubbed UGC 10738, turns out to have distinct ‘thick’ and ‘thin’ discs similar to those of the Milky Way. This suggests, contrary to previous theories, that such structures are not the result of a rare long-ago collision with a smaller galaxy. They appear to be the product of more peaceful change.

And that is a game-changer. It means that our spiral galaxy home isn’t the product of a freak accident. Instead, it is typical.

The finding was made by a team led by Nicholas Scott and Jesse van de Sande, from Australia’s ARC Centre of Excellence for All Sky Astrophysics in 3 Dimensions (ASTRO 3D) and the University of Sydney.

“Our observations indicate that the Milky Way’s thin and thick discs didn’t come about because of a gigantic mash-up, but a sort-of ‘default’ path of galaxy formation and evolution,” said Dr Scott.

“From these results we think galaxies with the Milky Way’s particular structures and properties could be described as the ‘normal’ ones.”

This conclusion – published in The Astrophysical Journal Letters– has two profound implications.

“It was thought that the Milky Way’s thin and thick discs formed after a rare violent merger, and so probably wouldn’t be found in other spiral galaxies,” said Dr Scott.

“Our research shows that’s probably wrong, and it evolved ‘naturally’ without catastrophic interventions. This means Milky Way-type galaxies are probably very common.

“It also means we can use existing very detailed observations of the Milky Way as tools to better analyse much more distant galaxies which, for obvious reasons, we can’t see as well.”

The research shows that UGC 10738, like the Milky Way, has a thick disc consisting mainly of ancient stars – identified by their low ratio of iron to hydrogen and helium. Its thin disc stars are more recent and contain more metal.

(The Sun is a thin disc star and comprises about 1.5% elements heavier than helium. Thick disc stars have three to 10 times less.)

Although such discs have been previously observed in other galaxies, it was impossible to tell whether they hosted the same type of star distribution – and therefore similar origins. Scott, van de Sande and colleagues solved this problem by using the European Southern Observatory’s Very Large Telescope in Chile to observe UGC 10738, situated 320 million light years away.

The galaxy is angled “edge on”, so looking at it offered effectively a cross-section of its structure.

“Using an instrument called the multi-unit spectroscopic explorer, or MUSE, we were able to assess the metal ratios of the stars in its thick and thin discs,” explained Dr van de Sande.

“They were pretty much the same as those in the Milky Way – ancient stars in the thick disc, younger stars in the thin one. We’re looking at some other galaxies to make sure, but that’s pretty strong evidence that the two galaxies evolved in the same way.”

Dr Scott said UGC 10738’s edge-on orientation meant it was simple to see which type of stars were in each disc.

“It’s a bit like telling apart short people from tall people,” he said. “It you try to do it from overhead it’s impossible, but it if you look from the side it’s relatively easy.”

Co-author Professor Ken Freeman from the Australian National University said, “This is an important step forward in understanding how disk galaxies assembled long ago. We know a lot about how the Milky Way formed, but there was always the worry that the Milky Way is not a typical spiral galaxy. Now we can see that the Milky Way’s formation is fairly typical of how other disk galaxies were assembled”.

ASTRO 3D director, Professor Lisa Kewley, added: “This work shows how the Milky Way fits into the much bigger puzzle of how spiral galaxies formed across 13 billion years of cosmic time.”

Other co-authors are based at Macquarie University in Australia and Germany’s Max-Planck-Institut fur Extraterrestrische Physik.

Featured image: Galaxy UGC 10738, seen edge-on through the European Southern Observatory’s Very Large Telescope in Chile, revealing distinct thick and thin discs. © Jesse van de Sande/European Southern Observatory


Reference: Nicholas Scott, Jesse van de Sande et al., “Identification of an [α/Fe]—Enhanced Thick Disk Component in an Edge-on Milky Way Analog”, The Astrophysical Journal Letters, 913(1), 2021. Link to paper


Provided by ASTRO-3D

36 Dwarf Galaxies Had Simultaneous “Baby Boom” of New Stars (Cosmology)

Surprising finding challenges current theories on how galaxies grow

Three dozen dwarf galaxies far from each other had a simultaneous “baby boom” of new stars, an unexpected discovery that challenges current theories on how galaxies grow and may enhance our understanding of the universe.

Galaxies more than 1 million light-years apart should have completely independent lives in terms of when they give birth to new stars. But galaxies separated by up to 13 million light-years slowed down and then simultaneously accelerated their birth rate of stars, according to a Rutgers-led study published in the Astrophysical Journal.

“It appears that these galaxies are responding to a large-scale change in their environment in the same way a good economy can spur a baby boom,” said lead author Charlotte Olsen, a doctoral student in the Department of Physics and Astronomy in the School of Arts and Sciences at Rutgers University–New Brunswick.

“We found that regardless of whether these galaxies were next-door neighbors or not, they stopped and then started forming new stars at the same time, as if they’d all influenced each other through some extra-galactic social network,” said co-author Eric Gawiser, a professor in the Department of Physics and Astronomy.

Rutgers’ unexpected discovery challenges current theories on how galaxies grow and may enhance our understanding of the universe. © Rutgers University-New Brunswick

The simultaneous decrease in the stellar birth rate in the 36 dwarf galaxies began 6 billion years ago, and the increase began 3 billion years ago. Understanding how galaxies evolve requires untangling the many processes that affect them over their lifetimes (billions of years). Star formation is one of the most fundamental processes. The stellar birth rate can increase when galaxies collide or interact, and galaxies can stop making new stars if the gas (mostly hydrogen) that makes stars is lost.

Star formation histories can paint a rich record of environmental conditions as a galaxy “grew up.” Dwarf galaxies are the most common but least massive type of galaxies in the universe, and they are especially sensitive to the effects of their surrounding environment.

The 36 dwarf galaxies included a diverse array of environments at distances as far as 13 million light-years from the Milky Way. The environmental change the galaxies apparently responded to must be something that distributes fuel for galaxies very far apart. That could mean encountering a huge cloud of gas, for example, or a phenomenon in the universe we don’t yet know about, according to Olsen.

The scientists used two methods to compare star formation histories. One uses light from individual stars within galaxies; the other uses the light of a whole galaxy, including a broad range of colors.

“The full impact of the discovery is not yet known as it remains to be seen how much our current models of galaxy growth need to be modified to understand this surprise,” Gawiser said. “If the result cannot be explained within our current understanding of cosmology, that would be a huge implication, but we have to give the theorists a chance to read our paper and respond with their own research advances.”

“The James Webb Space Telescope, scheduled to be launched by NASA this October, will be the ideal way to add that new data to find out just how far outwards from the Milky Way this ‘baby boom’ extended,” Olsen added.

Rutgers co-authors include Professor Kristen B. W. McQuinnGrace Telford, a postdoctoral associate; and Adam Broussard, a doctoral student. Scientists at the University of Toronto, the Harvard-Smithsonian Center for Astrophysics, Johns Hopkins University and NASA’s Goddard Space Flight Center contributed to the study.

Featured image: The Milky Way-like galaxy NGC 1232 (center) shows the Milky Way’s location and relative size. Images of dwarf galaxies are centered close to their true locations but have been magnified for visibility. Credit: Charlotte Olsen


Reference: Charlotte Olsen, Eric Gawiser et al., “Star Formation Histories from Spectral Energy Distributions and Color–magnitude Diagrams Agree: Evidence for Synchronized Star Formation in Local Volume Dwarf Galaxies over the Past 3 Gyr”, Astrophysical Journal, 913(1), 2021.


Provided by Rutgers University

Plasma Jets Reveal Magnetic Fields Far, Far Away (Cosmology)

Radio telescope images enable a new way to study magnetic fields in galaxy clusters millions of light years away.

For the first time, researchers have observed plasma jets interacting with magnetic fields in a massive galaxy cluster 600 million light years away, thanks to the help of radio telescopes and supercomputer simulations. The findings, published in the journal Nature, can help clarify how such galaxy clusters evolve.

Galaxy clusters can contain up to thousands of galaxies bound together by gravity. Abell 3376 is a huge cluster forming as a result of a violent collision between two sub-clusters of galaxies. Very little is known about the magnetic fields that exist within this and similar galaxy clusters.

“It is generally difficult to directly examine the structure of intracluster magnetic fields,” says Nagoya University astrophysicist Tsutomu Takeuchi, who was involved in the research. “Our results clearly demonstrate how long-wavelength radio observations can help explore this interaction.”

An international team of scientists have been using the MeerKAT radio telescope in the Northern Cape of South Africa to learn more about Abell 3376’s huge magnetic fields. One of the telescope’s very high-resolution images revealed something unexpected: plasma jets emitted by a supermassive black hole in the cluster bend to form a unique T-shape as they extend outwards for distances as far as 326,156 light years away. The black hole is in galaxy MRC 0600-399, which is near the centre of Abell 3376.

The team combined their MeerKAT radio telescope data with X-ray data from the European Space Agency’s space telescope XXM-Newton to find that the plasma jet bend occurs at the boundary of the subcluster in which MRC 0600-399 exists.

“This told us that the plasma jets from MRC 0600-399 were interacting with something in the heated gas, called the intracluster medium, that exists between the galaxies within Abell 3376,” explains Takeuchi.

To figure out what was happening, the team conducted 3D ‘magnetohydrodynamic’ simulations using the world’s most powerful supercomputer in the field of astronomical calculations, ATERUI II, located at the National Astronomical Observatory of Japan.

The simulations showed that the jet streams emitted by MRC 0600-399’s black hole eventually reach and interact with magnetic fields at the border of the galaxy subcluster. The jet stream compresses the magnetic field lines and moves along them, forming the characteristic T-shape.

“This is the first discovery of an interaction between cluster galaxy plasma jets and intracluster magnetic fields,” says Takeuchi.

An international team has just begun construction of what is planned to be the world’s largest radio telescope, called the Square Kilometre Array (SKA).

“New facilities like the SKA are expected to reveal the roles and origins of cosmic magnetism and even to help us understand how the universe evolved,” says Takeuchi. “Our study is a good example of the power of radio observation, one of the last frontiers in astronomy.”

The study, “Jets from MRC 0600-399 bent by magnetic fields in the cluster Abell 3376,” was published in the journal Nature on May 5, 2021, at https://www.nature.com/articles/s41586-021-03434-1.

Authors:

James O. Chibueze, Haruka Sakemi, Takumi Ohmura, Mami Machida, Hiroki Akamatsu, Takuya Akahori, Hiroyuki Nakanishi, Viral Parekh, Ruby van Rooyen, and Tsutomu T. Takeuchi*  (* Graduate School of Science, Nagoya University)

Video (Credit: Takumi Ohmura, Mami Machida, Hirotaka Nakayama, 4D2U Project, NAOJ)

Featured image: A black hole (marked by the red x) at the centre of galaxy MRC 0600-399 emits a jet of particles that bends into a ‘double-scythe’ T-shape that follows the magnetic field lines at the galaxy subcluster’s boundary. (Image Credit: Modified from Chibueze, Sakemi, Ohmura et al. (2021) Nature Fig. 1(b))


Provided by Nagoya University