From DOE’s Fermi National Accelerator Laboratory(US) : “Scientists move a step closer to understanding the “cold spot” in the cosmic microwave background”

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FNAL Art Image by Angela Gonzales

From DOE’s Fermi National Accelerator Laboratory(US) , an enduring source of strength for the US contribution to scientific research world wide.

January 11, 2022
Maxwell Bernstein

After the Big Bang, the universe, glowing brightly, was opaque and so hot that atoms could not form. Eventually cooling down to about minus 454 degrees Fahrenheit (-270 degrees Celsius), much of the energy from the Big Bang took the form of light. This afterglow, known as the cosmic microwave background [CMB], can now be seen with telescopes at microwave frequencies invisible to human eyes. It has tiny fluctuations in temperature that provide information about the early universe.

CMB per European Space Agency(EU) Planck.

Now scientists might have an explanation for the existence of an especially cold region in the afterglow, known as the CMB Cold Spot. Its origin has been a mystery so far but might be attributed to the largest absence of galaxies ever discovered.

Scientists used data collected by the Dark Energy Survey to confirm the existence of one of the largest supervoids known to humanity, the Eridanus supervoid, as reported in a paper published in December 2021 [MNRAS]. This once-hypothesized but now-confirmed void in the cosmic web might be a possible cause for the anomaly in the CMB.
Dark Energy Survey

Dark Energy Camera [DECam] built at DOE’s Fermi National Accelerator Laboratory(US).
NOIRLab National Optical Astronomy Observatory(US) Cerro Tololo Inter-American Observatory(CL) Victor M Blanco 4m Telescope which houses the Dark-Energy-Camera – DECam at Cerro Tololo, Chile at an altitude of 7200 feet.

NOIRLab(US)NSF NOIRLab NOAO (US) Cerro Tololo Inter-American Observatory(CL) approximately 80 km to the East of La Serena, Chile, at an altitude of 2200 meters.

Timeline of the Inflationary Universe WMAP.

The Dark Energy Survey (DES) is an international, collaborative effort to map hundreds of millions of galaxies, detect thousands of supernovae, and find patterns of cosmic structure that will reveal the nature of the mysterious dark energy that is accelerating the expansion of our Universe. DES began searching the Southern skies on August 31, 2013.

According to Einstein’s theory of General Relativity, gravity should lead to a slowing of the cosmic expansion. Yet, in 1998, two teams of astronomers studying distant supernovae made the remarkable discovery that the expansion of the universe is speeding up. To explain cosmic acceleration, cosmologists are faced with two possibilities: either 70% of the universe exists in an exotic form, now called dark energy, that exhibits a gravitational force opposite to the attractive gravity of ordinary matter, or General Relativity must be replaced by a new theory of gravity on cosmic scales.

DES is designed to probe the origin of the accelerating universe and help uncover the nature of dark energy by measuring the 14-billion-year history of cosmic expansion with high precision. More than 400 scientists from over 25 institutions in the United States, Spain, the United Kingdom, Brazil, Germany, Switzerland, and Australia are working on the project. The collaboration built and is using an extremely sensitive 570-Megapixel digital camera, DECam, mounted on the Blanco 4-meter telescope at Cerro Tololo Inter-American Observatory, high in the Chilean Andes, to carry out the project.

Over six years (2013-2019), the DES collaboration used 758 nights of observation to carry out a deep, wide-area survey to record information from 300 million galaxies that are billions of light-years from Earth. The survey imaged 5000 square degrees of the southern sky in five optical filters to obtain detailed information about each galaxy. A fraction of the survey time is used to observe smaller patches of sky roughly once a week to discover and study thousands of supernovae and other astrophysical transients.

The Eridanus supervoid

The cosmic web is made of clusters and superclusters of galaxies. They are pulled together by the attractive force of gravity and accelerated away from each other by the repulsive force of a mysterious, not-yet-understood phenomenon called dark energy.

Between these clusters of galaxies are voids: vast regions of space that contain fewer galaxies, and thus less ordinary matter, and less dark matter than exists within the galaxy clusters.

Among the largest structures known to humanity, the supervoid in the constellation Eridanus is a massive, elongated, cigar-shaped void in the cosmic web that’s 1.8 billion lightyears wide and has been observed to contain about 30% less matter than the surrounding galactic region. Its center is located 2 billion lightyears from Earth, making it the dominant underdensity of matter in our galactic neighborhood.

Mapping Dark Matter

To make this discovery, scientists used Dark Energy Survey data to create a map of Dark Matter in the same direction as the CMB Cold Spot, by observing the effect of gravitational lensing.

Gravitational Lensing Gravitational Lensing National Aeronautics Space Agency (US) and European Space Agency [Agence spatiale européenne][Europäische Weltraumorganisation](EU).

It’s a phenomenon that occurs when the paths of light are warped by the gravitational influence of Dark Matter.

The Cold Spot resides in the constellation Eridanus in the southern galactic hemisphere. The inset shows the microwave temperature map of this patch of sky, as mapped by the European Space Agency Planck satellite. The main figure depicts the map of the Dark Matter distribution created by the Dark Energy Survey team. Image: Gergö Kránicz and András Kovács.

“This map of Dark Matter is the largest ever such map that’s been created,” said Niall Jeffrey, the scientist who worked on the construction of a dark matter map. “We have been able to map out Dark Matter over a quarter of the Southern Hemisphere.”

Scientists previously counted the number of galaxies visible in the location of the CMB Cold Spot and found an underdensity of galaxies in that region. The new map shows there is a matching underdensity of invisible Dark Matter.

Using voids to understand dark energy

The Dark Energy Survey is an international effort to understand the effect dark energy has on the acceleration of the universe. It involves 300 scientists from 25 institutions in seven countries.

The Dark Energy Survey documents hundreds of millions of galaxies, supernovae and patterns within the cosmic web, using a 570-Megapixel digital camera, called the DECam, high in the Chilean Andes. This camera’s construction and integration of components was led by the U.S. Department of Energy’s Fermi National Accelerator Laboratory.

“We were thinking many years ago, a decade and a half at least, how would voids affect the present acceleration of the universe,” said Juan Garcia-Bellido, a cosmologist from IFT-Madrid and co-author of the paper.

At the largest scales of the universe, there is a tug-of-war between the gravitational forces and the expansion of the universe from dark energy, making some of the voids between galactic clusters deeper.

“Photons or particles of light enter into a void at a time before the void starts deepening and leave after the void has become deeper,” said Garcia-Bellido. “This process means that there is a net energy loss in that journey; that’s called the Integrated Sachs-Wolfe effect. When photons fall into a potential well, they gain energy, and when they come out of a potential well, they lose energy. This is the gravitational redshift effect.”

Open questions

Although the new result confirms that the Eridanus supervoid is gigantic, it still is not sufficient to explain the discrepancy between the predictions of the current standard cosmological model used to predict the behavior of dark energy—known as the Lambda Cold Dark Matter model—and the observed change in temperature in the Cold Spot that can be attributed to the supervoid’s effect on photons from the CMB.

“Having the coincidence of these two individually rare structures in the cosmic web and in the CMB is basically not enough to prove causality with the scientific standard,” said András Kovács, the lead researcher on this project.

“It is enough of a new element in the long history of the CMB Cold Spot problem that after this, people will at least be sure that there is a supervoid, which is a good thing because some people have debated that,” said Kovács.

In short, there are two ways to think about this problem: Either the Lambda-CDM model is correct, and the CMB Cold Spot is an extreme anomaly that coincidentally has a massive supervoid in front of it, or the Lambda-CDM model is incorrect, and the Integrated Sachs-Wolfe effect is stronger in supervoids than expected.

The latter would indicate a greater influence of dark energy on the universe and possibly faster cosmic expansion. Interestingly, this possibility is backed up by evidence from other, more distant supervoids. Moreover, the Dark Energy Survey team observed that the lensing signal from the Eridanus supervoid is slightly weaker than expected.

“The trouble is that typical alternative models cannot explain this discrepancy either, so if true, it might mean that we do not understand something very deep about dark energy,” said Kovács.

Dark Matter Background
Fritz Zwicky discovered Dark Matter in the 1930s when observing the movement of the Coma Cluster., Vera Rubin a Woman in STEM, denied the Nobel, some 30 years later, did most of the work on Dark Matter.

Fritz Zwicky.
Coma cluster via NASA/ESA Hubble, the original example of Dark Matter discovered during observations by Fritz Zwicky and confirmed 30 years later by Vera Rubin.
In modern times, it was astronomer Fritz Zwicky, in the 1930s, who made the first observations of what we now call dark matter. His 1933 observations of the Coma Cluster of galaxies seemed to indicated it has a mass 500 times more than that previously calculated by Edwin Hubble. Furthermore, this extra mass seemed to be completely invisible. Although Zwicky’s observations were initially met with much skepticism, they were later confirmed by other groups of astronomers.

Thirty years later, astronomer Vera Rubin provided a huge piece of evidence for the existence of dark matter. She discovered that the centers of galaxies rotate at the same speed as their extremities, whereas, of course, they should rotate faster. Think of a vinyl LP on a record deck: its center rotates faster than its edge. That’s what logic dictates we should see in galaxies too. But we do not. The only way to explain this is if the whole galaxy is only the center of some much larger structure, as if it is only the label on the LP so to speak, causing the galaxy to have a consistent rotation speed from center to edge.

Vera Rubin, following Zwicky, postulated that the missing structure in galaxies is dark matter. Her ideas were met with much resistance from the astronomical community, but her observations have been confirmed and are seen today as pivotal proof of the existence of dark matter.
Astronomer Vera Rubin at the Lowell Observatory in 1965, worked on Dark Matter (The Carnegie Institution for Science).

Vera Rubin, with Department of Terrestrial Magnetism (DTM) image tube spectrograph attached to the Kitt Peak 84-inch telescope, 1970.

Vera Rubin measuring spectra, worked on Dark Matter(Emilio Segre Visual Archives AIP SPL).
Dark Matter Research

LBNL LZ Dark Matter Experiment (US) xenon detector at Sanford Underground Research Facility(US) Credit: Matt Kapust.

Lamda Cold Dark Matter Accerated Expansion of The universe http the-cosmic-inflation-suggests-the-existence-of-parallel-universes. Credit: Alex Mittelmann.

DAMA at Gran Sasso uses sodium iodide housed in copper to hunt for dark matter LNGS-INFN.

Yale HAYSTAC axion dark matter experiment at Yale’s Wright Lab.

DEAP Dark Matter detector, The DEAP-3600, suspended in the SNOLAB (CA) deep in Sudbury’s Creighton Mine.

The LBNL LZ Dark Matter Experiment (US) Dark Matter project at SURF, Lead, SD, USA.

DAMA-LIBRA Dark Matter experiment at the Italian National Institute for Nuclear Physics’ (INFN’s) Gran Sasso National Laboratories (LNGS) located in the Abruzzo region of central Italy.

DARWIN Dark Matter experiment. A design study for a next-generation, multi-ton dark matter detector in Europe at The University of Zurich [Universität Zürich](CH).

PandaX II Dark Matter experiment at Jin-ping Underground Laboratory (CJPL) in Sichuan, China.

Inside the Axion Dark Matter eXperiment U Washington (US) Credit : Mark Stone U. of Washington. Axion Dark Matter Experiment.

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DOE’s Fermi National Accelerator (US) Laboratory Wilson Hall .

Fermi National Accelerator Laboratory(US), located just outside Batavia, Illinois, near Chicago, is a Department of Energy (US) national laboratory specializing in high-energy particle physics. Since 2007, Fermilab has been operated by the Fermi Research Alliance, a joint venture of the University of Chicago, and the Universities Research Association (URA). Fermilab is a part of the Illinois Technology and Research Corridor.

Fermilab’s Tevatron was a landmark particle accelerator; until the startup in 2008 of the Large Hadron Collider(CH) near Geneva, Switzerland, it was the most powerful particle accelerator in the world, accelerating antiprotons to energies of 500 GeV, and producing proton-proton collisions with energies of up to 1.6 TeV, the first accelerator to reach one “tera-electron-volt” energy. At 3.9 miles (6.3 km), it was the world’s fourth-largest particle accelerator in circumference. One of its most important achievements was the 1995 discovery of the top quark, announced by research teams using the Tevatron’s CDF and DØ detectors. It was shut down in 2011.

In addition to high-energy collider physics, Fermilab hosts fixed-target and neutrino experiments, such as MicroBooNE (Micro Booster Neutrino Experiment), NOνA (NuMI Off-Axis νe Appearance) and SeaQuest.

Completed neutrino experiments include MINOS (Main Injector Neutrino Oscillation Search), MINOS+, MiniBooNE and SciBooNE (SciBar Booster Neutrino Experiment).

The MiniBooNE detector was a 40-foot (12 m) diameter sphere containing 800 tons of mineral oil lined with 1,520 phototube detectors. An estimated 1 million neutrino events were recorded each year. SciBooNE sat in the same neutrino beam as MiniBooNE but had fine-grained tracking capabilities. The NOνA experiment uses, and the MINOS experiment used, Fermilab’s NuMI (Neutrinos at the Main Injector) beam, which is an intense beam of neutrinos that travels 455 miles (732 km) through the Earth to the Soudan Mine in Minnesota and the Ash River, Minnesota, site of the NOνA far detector.

In 2017, the ICARUS neutrino experiment was moved from CERN to Fermilab.

In the public realm, Fermilab is home to a native prairie ecosystem restoration project and hosts many cultural events: public science lectures and symposia, classical and contemporary music concerts, folk dancing and arts galleries. The site is open from dawn to dusk to visitors who present valid photo identification.
Asteroid 11998 Fermilab is named in honor of the laboratory.
Weston, Illinois, was a community next to Batavia voted out of existence by its village board in 1966 to provide a site for Fermilab.

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After Wilson stepped down in 1978 to protest the lack of funding for the lab, Leon M. Lederman took on the job. It was under his guidance that the original accelerator was replaced with the Tevatron, an accelerator capable of colliding protons and antiprotons at a combined energy of 1.96 TeV. Lederman stepped down in 1989. The science education center at the site was named in his honor.
The later directors include:

John Peoples, 1989 to 1996
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Fermilab continues to participate in the work at the Large Hadron Collider (LHC); it serves as a Tier 1 site in the Worldwide LHC Computing Grid.

DOE’s Fermi National Accelerator Laboratory(US) campus.

DOE’s Fermi National Accelerator Laboratory(US)/MINERvA. Photo Reidar Hahn.

DOE’s Fermi National Accelerator Laboratory(US)DAMIC | Fermilab Cosmic Physics Center.

DOE’s Fermi National Accelerator Laboratory(US) Muon g-2 studio. As muons race around a ring at the Muon g-2 studio, their spin axes twirl, reflecting the influence of unseen particles.

DOE’s Fermi National Accelerator Laboratory(US) Short-Baseline Near Detector under construction.

DOE’s Fermi National Accelerator Laboratory(US) Mu2e solenoid.

Dark Energy Camera [DECam], built at DOE’s Fermi National Accelerator Laboratory(US).

Fermi National Accelerator Laboratory DUNE/LBNF experiment (US) Argon tank at Sanford Underground Research Facility(US).

FNAL Dune Far Detector.

DOE’s Fermi National Accelerator Laboratory(US)/MicrobooNE.

FNAL Don Lincoln.

DOE’s Fermi National Accelerator Laboratory(US)/MINOS.

DOE’s Fermi National Accelerator Laboratory(US) Cryomodule Testing Facility.

DOE’s Fermi National Accelerator Laboratory(US) MINOS Far Detector.

FNAL DUNE LBNF (US) from FNAL to SURF Lead, South Dakota, USA.

European Organization for Nuclear Research [Organisation européenne pour la recherche nucléaire] (CH) ProtoDune.

DOE’s Fermi National Accelerator Laboratory(US)/NOvA experiment map .

DOE’s Fermi National Accelerator Laboratory(US) NOvA Near Detector at Batavia IL, USA.

DOE’s Fermi National Accelerator Laboratory(US)/ICARUS.

DOE’s Fermi National Accelerator Laboratory(US) Holometer.

DOE’s Fermi National Accelerator Laboratory(US)LArIAT.

DOE’s Fermi National Accelerator Laboratory(US) ICEBERG particle detector.