Rings and things Rings and things

MCG+07-07-072

A glowing bar stretching across its core; from the ends of the bar, thin spiral arms wrap around the galaxy to form a closed disc. The arms are fuzzy from the dust and stars they contain. The galaxy is on a black, mostly-empty background. A few foreground stars with cross-shaped diffraction spikes can be seen, as well as some distant galaxies in the background. Credit: ESA/Hubble & NASA, I. Chilingarian

The subject of this week’s circular Hubble Picture of the Week is situated in the Perseus Cluster, also known as Abell 426, 320 million light-years from Earth. It’s a barred spiral galaxy known as MCG+07-07-072, seen here among a number of photobombing stars that are much closer to Earth than it is.

MCG+07-07-072 has quite an unusual shape, for a spiral galaxy, with thin arms emerging from the ends of its barred core to draw a near-circle around its disc. It is classified, using a common extension of the basic Hubble scheme, as an SBc(r) galaxy: the c denotes that its two spiral arms are loosely wound, each only performing a half-turn around the galaxy, and the (r) is for the ring-like structure they create. Rings in galaxies come in quite a few forms, from merely uncommon, to rare and astrophysically important!

Lenticular galaxies are a type that sit between elliptical and spiral galaxies. They feature a large disc, unlike an elliptical galaxy, but lack any spiral arms. Lenticular means lens-shaped, and these galaxies often feature ring-like shapes in their discs. Meanwhile, the classification of “ring galaxy” is reserved for peculiar galaxies with a round ring of gas and star formation, much like spiral arms look, but completely disconnected from the galactic nucleus - or even without any visible nucleus! They’re thought to be formed in galactic collisions. Finally, there are the famous gravitational lenses, where the ring is in fact a distorted image of a distant, background galaxy, formed by the ‘lens’ galaxy bending light around it. Ring-shaped images, called Einstein rings, only form when the lensing and imaged galaxies are perfectly aligned.

Source: ESA/Hubble/potw

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Chandra Data Tests "Theory of Everything"

Perseus Cluster

Credit: NASA/CXC/Univ. of Cambridge/C. Reynolds et al.

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A Tour of Chandra Data Tests "Theory of Everything" - More Animations 

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Astronomers using NASA's Chandra X-ray Observatory have made one of the first experimental tests of string theory, a set of models intended to tie together all known forces, particles, and interactions. As described in our latest press release, researchers used Chandra to look for signs of an as-yet undetected particle predicted by string theory. The lack of a detection in these Chandra observations helps rule out some versions of string theory.

The team looked for extraordinarily low-mass "axion-like" particles in the Perseus galaxy cluster, shown in a Chandra image in the main panel of this graphic (red, green and blue colors are low, medium and high X-ray energies respectively). Galaxy clusters, the largest structures in the Universe held together by gravity, offer an excellent opportunity to search for these particles. In a galaxy cluster, X-ray photons from an embedded or a background source can travel through a large amount of hot gas permeated with magnetic field lines. Some of the X-ray photons may undergo conversion into axion-like particles, or the other way around, along this journey. A simplified illustration shows this process, with shorter wavelength X-ray photons (in blue) converting into axion-like particles (yellow) and back to photons, as they travel across magnetic field lines (grey) in the cluster. Longer wavelength X-ray photons (red) are converting into axion-like particles, but not back into photons. Such conversions would cause a distortion in the X-ray spectrum (the amount of X-rays at different energies) of a bright or embedded source of X-rays.

Photon/Particle Illustration

Credit: Amanda Smith/Institute of Astronomy/University of Cambridge 

Astronomers obtained a long Chandra observation, lasting over five days, of the central supermassive black hole in the center of the Perseus galaxy cluster (shown in the inset.) The spectrum of the region around the black hole showed no distortions, allowing the team to rule out the presence of most types of axion-like particles in the relatively low mass range their search was sensitive to.

Here the Chandra spectrum (red) of Perseus' central black hole shows the intensity of X-rays as a function of X-ray energy, along with an example (black) of a model X-ray spectrum predicted if axion-like particles were actually being converted from and into photons. To highlight the distortions that could have been detected, the data divided by the example model are also shown.

Chandra Spectrum

Credit: NASA/CXC/Univ. of Cambridge/C. Reynolds et al. 

One possible interpretation of this work is that axion-like particles do not exist. Another possible interpretation is that the particles undergo conversion from and into photons less easily than some particle physicists have expected. They also could have higher masses than probed with the Chandra data.

There has been a surge of interest in studies of these particles in recent years for three reasons: First, despite a lot of work, there continues to be no detection of Weakly Interacting Massive Particles (WIMPs), either with gamma-ray observations, or earth-based experiments that could explain the nature of dark matter. These particles are predicted to interact with normal matter only via the weak force, and have been considered to be one of the strongest candidates for dark matter. Secondly, scientists have realized that axions and axion-like particles are predicted by string theory. Finally, there are a large number of experiments or observations that can be done to search for these particles.

A paper describing these results appeared in the February 10th, 2020 issue of The Astrophysical Journal and is available online. The authors are Christopher Reynolds (University of Cambridge, UK), David Marsh (Stockholm University, Sweden), Helen Russell (University of Nottingham, UK), Andrew C. Fabian (University of Cambridge), Robyn Smith (University of Maryland in College Park, Francesco Tombesi (University of Rome, Italy), and Sylvain Veilleux (University of Maryland).

NASA's Marshall Space Flight Center manages the Chandra program. The Smithsonian Astrophysical Observatory's Chandra X-ray Center controls science and flight operations from Cambridge and Burlington, Massachusetts.

A Quick Look at Chandra Data Tests "Theory of Everything"

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Fast Facts for Perseus Cluster:


Scale: Main image is about 8 arcmin (550,000 light years) across. Inset image is about 11 arcsec (13,000 light years) across.
Category: Groups & Clusters of Galaxies, Black Holes
Coordinates (J2000): RA 03h 19m 47.60s | Dec +41° 30´ 37.00"
Constellation: Perseus

Observation Date: Main image: 25 pointings between Sep 1999 and Dec 2009; Inset: 15 pointings between Jun 2017 and Dec 2017

Observation Time: Main Image: 17 days 8 hours 37 minutes; Inset: 5 days 16 hours 30 minutes

Obs. ID: Main Image: 502, 503, 1513, 3209, 3404, 4289, 4946-4953, 6139, 6145, 6146, 11713-11716, 12025, 12033, 12036, 12037; Inset: 20449-20451, 20823-20827, 20837-20844

Instrument: ACIS
Also Known As: Abell 426
References: Reynolds, C.S., et. al., 2020, ApJ, 890, 59; arXiv:1907.05475
Color Code: Red = 0.5-1.2 keV, Green = 1.2-2.0 keV, Blue = 2.0-7.0 keV
Distance Estimate: About 240 million light years

Source: NASA’s Chandra X-ray Observatory

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Perseus Cluster: Scientists Surprised by Relentless Cosmic Cold Front

Perseus Cluster

Credit NASA/CXC/GSFC/S. Walker, ESA/XMM, ROSAT

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A Tour of the cold front in Perseus - More Animations

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A gigantic and resilient "cold front" hurtling through the Perseus galaxy cluster has been studied using data from NASA's Chandra X-ray Observatory. This cosmic weather system spans about two million light years and has been traveling for over 5 billion years, longer than the existence of our Solar System.

This graphic shows the cold front in the Perseus cluster. The image above contains X-ray data from Chandra — for regions close to the center of the cluster —along with data from ESA's XMM-Newton and the now-defunct German Roentgen (ROSAT) satellite for regions farther out. The Chandra data have been specially processed to brighten the contrast of edges to make subtle details more obvious.

The cold front is the long vertical structure on the left side of the image (rollover the image above to view labels). It is about two million light years long and has traveled away from the center of the cluster at about 300,000 miles per hour.

The inset below shows a close-up view of the cold front from Chandra. This image is a temperature map, where blue represents relatively cooler regions (30 million degrees) while the red is where the hotter regions (80 million degrees) are.

Close-up view of the cold front; 

Credit: NASA/CXC/GSFC/S.Walker, ESA/XMM, ESA/ROSAT

The cold front has not only survived for over a third of the age of the Universe, but it has also remained surprisingly sharp and split into two different pieces. Astronomers expected that such an old cold front would have been blurred out or eroded over time because it has traveled for billions of years through a harsh environment of sound waves and turbulence caused by outbursts from the huge black hole at the center of Perseus.

Instead, the sharpness of the Perseus cold front suggests that the structure has been preserved by strong magnetic fields that are wrapped around it. The comparison of the Chandra X-ray data to theoretical models also gives scientists an indication of the strength of the cold front's magnetic field for the first time.

Perseus Cluster Temperature Animation (Labeled)
Credit: John ZuHone

While cold fronts in the Earth's atmospheres are driven by rotation of the planet, those in the atmospheres of galaxy clusters like Perseus are caused by collisions between the cluster and other clusters of galaxies. These collisions typically occur as the gravity of the main cluster pulls the smaller cluster inward towards its central core. As the smaller cluster makes a close pass by the central core, the gravitational attraction between both structures causes the gas in the core to slosh around like wine swirled in a glass. The sloshing produces a spiral pattern of cold fronts moving outward through the cluster gas.

Aurora Simionescu and collaborators originally discovered the Perseus cold front in 2012 using data from ROSAT (the ROentgen SATellite), ESA's XMM-Newton Observatory, and Japan's Suzaku X-ray satellite. Chandra's high-resolution X-ray vision allowed this more detailed work on the cold front to be performed.

The results of this work appear in a paper that will be published in the April issue of Nature Astronomy and is available online. The authors of the paper are Stephen Walker (Goddard Space Flight Center), John ZuHone (Harvard-Smithsonian Center for Astrophysics), Jeremy Sanders (Max Planck Institute for Extraterrestrial Physics), and Andrew Fabian (Institute of Astronomy, Cambridge, England.)

NASA's Marshall Space Flight Center in Huntsville, Alabama, manages the Chandra program for NASA's Science Mission Directorate in Washington. The Smithsonian Astrophysical Observatory in Cambridge, Massachusetts, controls Chandra's science and flight operations.

A Quick Look at the Cold Front in the Perseus Cluster

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Fast Facts for Perseus Cluster:


Scale: Image is about 42 arcmin (about 3 million light years) across.
Category: Groups & Clusters of Galaxies, Cosmology/Deep Fields/X-ray Background
Coordinates (J2000): RA 03h 19m 47.60s | Dec +41° 30´ 37.00"
Constellation: Perseus
Observation Date: Nov 13, 2016
Observation Time: 25 hours 50 min (1 day 1 hour 60 minutes)
Obs. ID: 19565, 19938
Instrument: ACIS
Also Known As: Abell 426
References: S. Walker et al., 2018, Nature Astronomy, arXiv:1803.00898
Color Code: X-ray (intensity)
Distance Estimate: About 250 million light years

Source: NASA’s Chandra X-ray Observatory

Perseus Cluster: A New Twist in the Dark Matter Tale A Quick Look at the Perseus Cluster

Perseus Cluster

Credit: X-ray: NASA/CXO/Oxford University/J. Conlon et al. Radio: NRAO/AUI/NSF/Univ. of Montreal/Gendron-Marsolais et al.

Optical: NASA/ESA/IoA/A. Fabian et al.; DSS

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Tour of Perseus Cluster - More Animations

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An innovative interpretation of X-ray data from a galaxy cluster could help scientists understand the nature of dark matter, as described in our latest press release. The finding involves a new explanation for a set of results made with NASA's Chandra X-ray Observatory, ESA's XMM-Newton and Hitomi, a Japanese-led X-ray telescope. If confirmed with future observations, this may represent a major step forward in understanding the nature of the mysterious, invisible substance that makes up about 85% of matter in the Universe.

The image shown here contains X-ray data from Chandra (blue) of the Perseus galaxy cluster, which has been combined with optical data from the Hubble Space Telescope (pink) and radio emission from the Very Large Array (red). In 2014, researchers detected an unusual spike of intensity, known as an emission line, at a specific wavelength of X-rays (3.5 keV) in the hot gas within the central region of the Perseus cluster. They also reported the presence of this same emission line in a study of 73 other galaxy clusters.

In the subsequent months and years, astronomers have tried to confirm the existence of this 3.5 keV line. They are eager to do so because it may give us important clues about the nature of dark matter. However, it has been debated in the astronomical community exactly what the original and follow-up observations have revealed.

Credit: NASA/CXC/M. Weiss

A new analysis of Chandra data by a team from Oxford University, however, is providing a fresh take on this debate. The latest work shows that absorption of X-rays at an energy of 3.5 keV is detected when observing the region surrounding the supermassive black hole at the center of Perseus. This suggests that dark matter particles in the cluster are both absorbing and emitting X-rays (see our artist's impression above for a diagram helping to explain this behavior, where 3.5 keV X-rays are shown). If the new model turns out to be correct, it could provide a path for scientists to one day identify the true nature of dark matter. For next steps, astronomers will need further observations of the Perseus cluster and others like it with current X-ray telescopes and those being planned for the next decade and beyond.

A paper describing these results was published in Physical Review D on December 19, 2017 and a preprint is available online. The authors of the paper are Joseph Conlon, Francesca Day, Nicolas Jennings, Sven Krippendorf and Markus Rummel, all from Oxford University in the UK. NASA's Marshall Space Flight Center in Huntsville, Alabama, manages the Chandra program for NASA's Science Mission Directorate in Washington. The Smithsonian Astrophysical Observatory in Cambridge, Massachusetts, controls Chandra's science and flight operations. 

A Quick Look at the Perseus Cluster

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Fast Facts for Perseus Cluster:

Scale: Image is 3.87 arcmin (about 280,000 light years) across
Category:   Groups & Clusters of Galaxies, Cosmology/Deep Fields/X-ray Background
Coordinates (J2000): RA 03h 19m 47.60s | Dec +41° 30´ 37.00"
Constellation: Perseus
Observation Date: 2009
Observation Time: 55 hours 33 minutes (2 days 7 hours 33 minutes)
Obs. ID: 11713,12025,12044, 12036
Instrument: ACIS
Also Known As: Abell 426
References: Conlon et al. 2017 Physical Review D, 90, 123009; arXiv: 1086.01684
Color Code: X-ray (Blue); Optical (Pink); Radio (Red)
Distance Estimate: About 250 million light years

Source: NASA’s Chandra X-ray Observatory

Perseus Cluster: Scientists Find Giant Wave Rolling through the Perseus Galaxy Cluster

 Perseus Cluster/Abell 426
Credit  NASA/CXC/GSFC/S.A.Walker, et al.

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Combining data from NASA's Chandra X-ray Observatory with radio observations and computer simulations, scientists have found a vast wave of hot gas in the Perseus galaxy cluster. Spanning some 200,000 light years, the wave is about twice the size of the Milky Way galaxy.

Researchers think the wave formed billions of years ago after a small galaxy cluster grazed Perseus and caused its vast supply of gas to slosh around in an enormous volume of space.

Galaxy clusters are the largest structures bound by gravity in the universe today. Some 11 million light years across and located about 240 million light years away, the Perseus galaxy cluster is named after its host constellation. Like all galaxy clusters, most of its observable matter takes the form of a pervasive gas averaging tens of millions of degrees — so hot it only glows in X-rays.

Chandra data have revealed a variety of structures in this gas, from vast bubbles blown by the supermassive black hole in the cluster's central galaxy, NGC 1275, to an enigmatic concave feature known as the "bay."

To investigate the bay, researchers combined a total of 10.4 days of high-resolution Chandra data with 5.8 days of wide-field observations at energies between 700 and 7,000 electron volts. This X-ray image of the hot gas (above) in the Perseus galaxy cluster was made from those observations. Researchers then filtered the data in a way that brightened the contrast of edges in order to make subtle details more obvious. An oval highlights the location of the enormous wave, centered around 7 o'clock, found to be rolling through the gas.

Next, the researchers compared the edge-enhanced Perseus image to computer simulations of merging galaxy clusters run on the Pleiades supercomputer at NASA's Ames Research Center.

Credit: John ZuHone/Harvard-Smithsonian Center for Astrophysics. 

One simulation seemed to explain the formation of the bay. This simulation is shown above. In it, gas in a large cluster similar to Perseus has settled into two components: a "cold" central region with temperatures around 54 million degrees Fahrenheit (30 million degrees Celsius) and a surrounding zone where the gas is three times hotter. Then a small galaxy cluster containing about a thousand times the mass of the Milky Way skirts the larger cluster, missing its center by about 650,000 light years.

The flyby creates a gravitational disturbance that churns up the gas like cream stirred into coffee, creating an expanding spiral of cold gas. After about 2.5 billion years, when the gas has risen nearly 500,000 light years from the center, vast waves form and roll at its periphery for hundreds of millions of years before dissipating.

These waves are giant versions of Kelvin-Helmholtz waves, which show up whenever there's a velocity difference across the interface of two fluids, such as wind blowing over water. They can be found in the ocean, in cloud formations on Earth and other planets, in plasma near Earth, and even on the sun.

A paper describing the findings appears in the June 2017 issue of the journal Monthly Notices of the Royal Astronomical Society and is available online. NASA's Marshall Space Flight Center in Huntsville, Alabama, manages the Chandra program for NASA's Science Mission Directorate in Washington. The Smithsonian Astrophysical Observatory in Cambridge, Massachusetts, controls Chandra's science and flight operations.

Source:  NASA’s Chandra X-ray Observatory

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Fast Facts for Perseus Cluster:

Scale: Image is 18.6 arcmin wide (about 1.3 million light years)

Category: Groups & Clusters of Galaxies

Coordinates (J2000): RA 03h 19m 47.60s | Dec +41° 30' 37.00"

Constellation: Perseus

Observation Date: 13 pointings between Aug 2002 and Oct 2004

Observation Time: 388 hours 53 minutes

Obs. ID: 3209, 4289, 4946-4953, 6139, 6145, 6146

Instrument: ACIS

Also Known As: Abell 426
References: Walker, S. A. et al., 2017, MNRAS [in press]; arXiv:1705.00011

Distance Estimate: About 250 million light years

Perseus Cluster and Virgo Cluster: NASA's Chandra Observatory Identifies Impact of Cosmic Chaos on Star Birth

 Galaxy Clusters - Perseus e Virgo Cluster

Credit: NASA/CXC/Stanford/I.Zhuravleva et al

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Tour of Perseus Cluster and Virgo Cluster

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These two Chandra images of galaxy clusters - known as Perseus and Virgo - have provided direct evidence that turbulence is helping to prevent stars from forming. These new results could answer a long-standing question about how these galaxy clusters keep their enormous reservoirs of hot gas from cooling down to form stars, as discussed in our latest press release [link to PR].

Galaxy clusters are the largest objects in the Universe held together by gravity. They contain hundreds or thousands of individual galaxies that are immersed in gas with temperatures of millions of degrees. This hot gas, which is the heftiest component of the galaxy clusters aside from dark matter, glows brightly in X-ray light. Over time in the centers of clusters, this gas should cool enough so that stars form at prodigious rates. This, however, is not what astronomers have observed in many galaxy clusters.

A team of researchers have found evidence that the heat is generated by turbulent motions, which they identified from signatures in the Chandra data. Previously, other scientists have shown the key role of supermassive black holes in the centers of large galaxies in the middle of galaxy clusters. These black holes pump vast quantities of energy into the volumes around them through powerful jets of energetic particles. Chandra and other X-ray telescopes have detected giant cavities created in the hot cluster gas by the jets.

The latest research provides insight into just how energy can be transferred from the cavities to the surrounding gas. The interaction of the cavities with the gas may be generating turbulence, or chaotic motion similar to that on a bumpy airplane ride, which then dissipates to keep the gas hot for billions of years.

The scientists targeted Perseus and Virgo because they are both extremely large and relatively bright, thus providing an opportunity to see details that would be very difficult to detect in other clusters. The evidence for turbulence can be seen most clearly in the ripple-like structures in the Chandra image of Perseus. When combined with careful analysis of the data with theoretical models, this new result provides the clearest evidence to date that turbulence is the mechanism that prevents the hot gas in these clusters from cooling.

The paper describing these results is available online.

These results appeared online in the journal Nature on October 26, 2014. The authors were Irina Zhuravleva (Stanford University), Eugene Churazov (Max Planck Institute for Astrophysics), Alexander Schekochinhin (University of Oxford), Steve Allen (Stanford), Patricia Arevalo (Pontificia Universidad Catolica de Chile), Andy Fabian (University of Cambridge), William Forman (Harvard-Smithsonian Center for Astrophysics), Jeremy Sanders (Max Planck Institute for Extraterrestrial Physics), Aurora Simionescu (JAXA), Rasheed Sunayev (Max Planck Institute for Astrophysics), Alexey Vikhlinin (Harvard-Smithsonian Center for Astrophysics), and Norbert Werner (Stanford).

NASA's Marshall Space Flight Center in Huntsville, Alabama, manages the Chandra program for NASA's Science Mission Directorate in Washington, DC. The Smithsonian Astrophysical Observatory in Cambridge, Massachusetts, controls Chandra's science and flight operations.

Fast Facts for Perseus Cluster: 


Release: Date October 27, 2014
Scale: Image is 20 arcmin across (about 1.5 million light years).
Category: Groups & Clusters of Galaxies
Coordinates (J2000): RA 03h 19m 47.60s | Dec +41° 30' 37.00"
Constellation: Perseus
Observation Dates: 25 pointings between Sep 1999 and Dec 2009
Observation Time: 416 hours 32 min (17 days 8 hours 32 min)
Obs. IDs: 502, 503, 1513, 3209, 3404, 4289, 4946-4953, 6139, 6145, 6146, 11713-11716, 12025, 12033, 12036, 12037
Instrument: ACIS
Also Known As: Abell 426
References: Zhuravleva, I. et al, 2014, Nature (in press); arXiv:1410.6485
Color Code: X-ray: Purple X-ray
Distance Estimate: About 250 million light years

Fast Facts for Virgo Cluster:


Release Date: October 27, 2014  
Scale: Image is 22 arcmin across (about 320,000 light years).  
Category: Groups & Clusters of Galaxies  
Coordinates (J2000): RA 12h 30m 49.40s | Dec +12° 23' 28.00"  
Constellation: Virgo
Observation Dates: 2 pointings in Jul 2002, and 7 between Jan and Nov 2005 
Observation Time: 159 hours (6 days 15 hours) 
Obs. IDs: 2707, 3717, 5826-5828, 6186, 7210-7212 
Instrument: ACIS  
References: Zhuravleva, I. et al, 2014, Nature (in press); arXiv:1410.6485 
Color Code: X-ray: Purple
Distance Estimate: About 55 million light years 

Source: NASA’s Chandra X-ray Observatory