Using the NASA/ESA/CSA James Webb Space Telescope, an international team of astronomers have found new galaxies in the Spiderweb protocluster. Because Webb can see infrared light very well, scientists used it to observe regions of the Spiderweb that were previously hidden to us by cosmic dust, and to find out to what degree this dust obscures them. This image shows the Spiderweb protocluster as seen by Webb’s NIRCam (Near-InfraRed Camera). Image Credit: ESA/Webb, NASA & CSA, H. Dannerbauer
As a species, we’ve come to the awareness that we’re a minuscule part of a vast Universe defined by galaxy superclusters and the large-scale structure of the Universe. Driven by a healthy intellectual curiosity, we’re examining our surroundings and facing the question posed by Nature: how did everything get this way?
We only have incremental answers to that huge, almost infinitely-faceted question. And the incremental answers are unearthed by our better instruments, including space telescopes, which get better and more capable as time passes.
This image from Farhanul Hansan’s paper in the Astrophysical Journal shows the large-scale matter distribution and cosmic “filaments” of the universe are more faithfully captured by the slime mold model than the existing standard framework. (Image courtesy Farhanul Hasan)
Computers truly are wonderful things and powerful but only if they are programmed by a skilful mind. Check this out… there is an algorithm that mimics the growth of slim mold but a team of researchers have adapted it to model the large scale structure of the Universe. Since the Big Bang, the universe has been expanding while gravity concentrates matter into galaxies and clusters of galaxies. Between them are vast swathes of empty space called voids. The structure, often referred to as the cosmic web.
A simulation of the cosmic web, diffuse tendrils of gas that connect galaxies across the universe. Credit: Illustris Collaboration
What can slime molds tell us about the large-scale structure of the Universe and the evolution of galaxies? These things might seem incongruous, yet both are part of nature, and Earthly slime molds seem to have something to tell us about the Universe itself. Vast filaments of gas threading their way through the Universe have a lot in common with slime molds and their tubular networks.
New research has imaged the Cosmic Web of cold dark gas that interconnects the Universe's galaxies. Image Credit: Martin et al. 2023.
One hundred years ago, we didn’t know there was anything outside of our own galaxy, the Milky Way. Now we know that our puny planet Earth, and everything else, is part of a vast structure called the Cosmic Web. Its scale is difficult to comprehend in any concrete way, and the system’s complexity and magnitude brings our most powerful supercomputers to their knees.
Astronomers have known about the Cosmic Web for some time, as they’ve caught glimpses of it. But a new instrument has given us our most complete view of it yet.
A composite image showing the magnetic fields of the cosmic web. Credit: Vernstrom et al
The universe is filled with magnetic fields. Although the universe is electrically neutral, atoms can be ionized into positively charged nuclei and negatively charged electrons. When those charges are accelerated, they create magnetic fields. One of the most common sources of magnetic fields on large scales comes from the collisions between and within interstellar plasma. This is one of the major sources of magnetic fields for galactic-scale magnetic fields.
Simulation of dark matter and gas. Credit: Illustris Collaboration (CC BY-SA 4.0)
Since it was first theorized in the 1970s, astrophysicists and cosmologists have done their best to resolve the mystery that is Dark Matter. This invisible mass is believed to make up 85% of the matter in the Universe and accounts for 27% of its mass-energy density. But more than that, it also provides the large-scale skeletal structure of the Universe (the cosmic web), which dictates the motions of galaxies and material because of its gravitational influence.
Unfortunately, the mysterious nature of Dark Matter means that astronomers cannot study it directly, thus prevented them from measuring its distribution. However, it is possible to infer its distribution based on the observable influence its gravity has on local galaxies and other celestial objects. Using cutting-edge machine-learning techniques, a team of Korean-American astrophysicists was able to produce the most detailed map yet of the local Universe that shows what the “cosmic web” looks like.
Left: section of cerebellum, with magnification factor 40x, obtained with electron microscopy (Dr. E. Zunarelli, University Hospital of Modena); right: section of a cosmological simulation, with an extension of 300 million light-years on each side (Vazza et al. 2019 A&A).
“Science is not only compatible with spirituality; it is a profound source of spirituality. When we recognize our place in an immensity of light years and in the passage of ages, when we grasp the intricacy, beauty and subtlety of life, then that soaring feeling, that sense of elation and humility combined, is surely spiritual.” – Carl Sagan “The Demon-Haunted World.”
Learning about the Universe, I’ve felt spiritual moments, as Sagan describes them, as I better understand my connection to the wider everything. Like when I first learned that I was literally made of the ashes of the stars – the atoms in my body spread into the eternal ether by supernovae. Another spiritual moment was seeing this image for the first time:
The structure of the universe at the largest scale. Credit: NASA, ESA, and E. Hallman (University of Colorado, Boulder)
For decades, the predominant cosmological model used by scientists has been based on the theory that in addition to baryonic matter – aka. “normal” or “luminous” matter, which we can see – the Universe also contains a substantial amount of invisible mass. This “Dark Matter” accounts for roughly 26.8% of the mass of the Universe, whereas normal matter accounts for just 4.9%.
While the search for Dark Matter is ongoing and direct evidence is yet to be found, scientists have also been aware that roughly 90% of the Universe’s normal matter still remained undetected. According to twonew studies that were recently published, much of this normal matter – which consists of filaments of hot, diffuse gas that links galaxies together – may have finally been found.
Based on cosmological simulations, the predominant theory has been that the previously-undetected normal matter of the Universe consists of strands of baryonic matter – i.e. protons, neutrons and electrons – that is floating between galaxies. These regions are what is known as the “Cosmic Web”, where low density gas exists at a temperatures of 105 to 107 K (-168 t0 -166 °C; -270 to 266 °F).
For the sake of their studies, both teams consulted data from the Planck Collaboration, a venture maintained by the European Space Agency that includes all those who contributed to the Planck mission (ESA). This was presented in 2015, where it was used to create a thermal map of the Universe by measuring the influence of the Sunyaev-Zeldovich (SZ) effect.
This effect refers to a spectral distortion in the Cosmic Microwave Background, where photons are scattered by ionized gas in galaxies and larger structures. During its mission to study the cosmos, the Planck satellite measured the spectral distortion of CMB photons with great sensitivity, and the resulting thermal map has since been used to chart the large-scale structure of the Universe.
IR map of the whole Galaxy showing the plane and bulge of the Galaxy full of stars and dust. Credit: SDSS
However, the filaments between galaxies appeared too faint for scientists to examine at the time. To remedy this, the two teams consulted data from the North and South CMASS galaxy catalogues, which were produced from the 12th data release of the Sloan Digital Sky Survey (SDSS). From this data set, they then selected pairs of galaxies and focused on the space between them.
They then stacked the thermal data obtained by Planck for these areas on top of each other in order to strengthen the signals caused by SZ effect between galaxies. As Dr. Hideki told Universe Today via email:
“The SDSS galaxy survey gives a shape of the large-scale structure of the Universe. The Planck observation provides an all-sky map of gas pressure with a better sensitivity. We combine these data to probe the low-dense gas in the cosmic web.”
While Tanimura and his team stacked data from 260,000 galaxy pairs, de Graaff and her team stacked data from over a million. In the end, the two teams came up with strong evidence of gas filaments, though their measurements differed somewhat. Whereas Tanimura’s team found that the density of these filaments was around three times the average density in the surrounding void, de Graaf and her team found that they were six times the average density.
“We detect the low-dense gas in the cosmic web statistically by a stacking method,” said Hideki. “The other team uses almost the same method. Our results are very similar. The main difference is that we are probing a nearby Universe, on the other hand, they are probing a relatively farther Universe.”
This illustration shows the evolution of the Universe, from the Big Bang on the left, to modern times on the right. Image: NASA
This particular aspect of particularly interesting, in that it hints that over time, baryonic matter in the Cosmic Web has become less dense. Between these two results, the studies accounted for between 15 and 30% of the total baryonic content of the Universe. While that would mean that a significant amount of the Universe’s baryonic matter still remains to be found, it is nevertheless an impressive find.
As Hideki explained, their results not only support the current cosmological model of the Universe (the Lambda CDM model) but also goes beyond it:
“The detail in our universe is still a mystery. Our results shed light on it and reveals a more precise picture of the Universe. When people went out to the ocean and started making a map of our world, it was not used for most of the people then, but we use the world map now to travel abroad. In the same way, a map of the entire universe may not be valuable now because we do not have a technology to go far out to the space. However, it could be valuable 500 years later. We are in the first stage of making a map of the entire Universe.”
It also opens up opportunities for future studies of the Comsic Web, which will no doubt benefit from the deployment of next-generation instruments like James Webb Telescope, the Atacama Cosmology Telescope and the Q/U Imaging ExperimenT (QUIET). With any luck, they will be able to spot the remaining missing matter. Then, perhaps we can finally zero in on all the invisible mass!
Comparison of Lyman alpha blob observed with Cosmic Web Imager and a simulation of the cosmic web based on theoretical predictions.
Credit: Christopher Martin, Robert Hurt
- See more at: http://www.caltech.edu/content/intergalactic-medium-unveiled-caltechs-cosmic-web-imager-directly-observes-dim-matter#sthash.3bs0Xl3d.dpuf
An international team of astronomers has taken unprecedented images of intergalactic space — the diffuse and often invisible gas that connects and feeds galaxies throughout the Universe.
Until now, the structure of intergalactic space has mostly been a matter for theoretical speculation. Advanced computer simulations predict that primordial gas from the Big Bang is distributed in a vast cosmic web — a network of filaments that span galaxies and flow between them.
This vast network is impossible to see alone. In the past astronomers have looked at distant quasars — supermassive black holes at the centers of galaxies which are rapidly accreting material and shining brightly — to indicate the otherwise invisible matter along their lines of sight.
While distant quasars may reveal the otherwise invisible gas, there’s no information about how that gas is distributed across space. New images, however, from the Cosmic Web Imager are revealing the webs’ filaments directly, allowing them to be seen across space.
The first filaments observed by the Cosmic Web Imager are in the vicinity of two ancient but bright objects: the quasar QSO 1549+19 and a so-called Lyman alpha blob (yes, this is a technical term for a huge concentration of hydrogen gas) in the emerging galaxy cluster SSA22. These objects are bright, lighting up the intervening galactic space and boosting the detectable signal.
Image of quasar (QSO 1549+19) taken with Caltech’s Cosmic Web Imager, showing surrounding gas (in blue) and direction of filamentary gas inflow. Image Credit: Christopher Martin, Robert Hurt
Both objects date back to two billion years after the Big Bang, in a time of rapid star formation in galaxies. Observations show a narrow filament, about one million light-years across flowing into the quasar, which is likely fueling the growth of the host galaxy.
There are three filaments flowing into the Lyman alpha blob. “I think we’re looking at a giant protogalactic disk,” said lead author Christopher Martin from the California Institute of Technology in a press release. “It’s almost 300,000 light-years in diameter, three times the size of the Milky Way.”
The Cosmic Web Imager on board the Hale 200 inch telescope is a spectrographic imager, taking pictures at many different wavelengths simultaneously. This allows astronomers to learn about objects’ composition, mass and velocity.
“The gaseous filaments and structures we see around the quasar and the Lyman alpha blob are unusually bright,” said Martin. “Our goal is to eventually be able to see the average intergalactic medium everywhere. It’s harder, but we’ll get there.”
A simulation of the "cosmic web" believed to connect galaxies. A galaxy can move into and out of this web throughout its lifetime. A void is visible in the center of the image, a spot where researchers found galaxy "tendrils." Credit: Cunnama, Power, Newton and Cui (ICRAR).
Engage! This video shows some results of the the Galaxy and Mass Assembly catalogue, including the real positions of galaxies. The simulated flythrough, with galactic bodies whizzing by, appears like the view from the Starship Enterprise going at high speed.
Unlike that science fiction series, however, the data you’re seeing has charted information in it (although the galaxies have been biggified for our “viewing pleasure.”)
It’s all part of new research showing that galaxies in “vast empty regions” of the Universe are “aligned into delicate strings,” stated the International Centre for Radio Astronomy Research.
“The spaces in the cosmic web are thought to be staggeringly empty,” stated Mehmet Alpaslan, a Ph.D. candidate at St Andrews University, Scotland who led the research. “They might contain just one or two galaxies, as opposed to the hundreds that are found in big clusters.”
His team discovered faint galaxies lined up in areas of space believed to hold practically nothing. The work is part of an emerging set of research looking at voids in the “cosmic web”, or the filaments that are believed to hold galaxies together across great distances.
Alpaslan’s team used a galaxy census — the biggest ever — of the skies in the south created with observations of Australia’s Anglo-Australian Telescope. The arrangement of galaxies in these voids was surprising to researchers.
“We found small strings composed of just a few galaxies penetrating into the voids, a completely new type of structure that we’ve called ‘tendrils’,” stated Alpaslan.
It will be interesting to see what further research reveals. As the press release accompanying this news states, “These aren’t the voids you’re looking for.”
