Tag Archives: #galaxycluster

Abell’s Orphan Cloud 1367 (Cosmology)

It is an immense cloud of hot gas first discovered in 2017 by the Japanese Subaru telescope in the intergalactic medium of the Abell 1367 cluster. It is an isolated cloud, not associated with any galaxy in the cluster. New observations conducted with the Subaru telescope, with the Vlt and Xmm-Newton have now made it possible to measure different properties, to identify its origin and the mechanism that allowed it to fluctuate between galaxies, making its existence surprising. All details in Monthly Notices of the Royal Astronomical Society

The galaxy clusters are among the largest celestial objects of the universe: they can contain from tens to thousands of galaxies held together by gravity and extend for millions of light years. Abell 1367 is one of them. It is a young cluster of about 70 galaxies located 300 million light years from Earth in the constellation of Leo . In 2017, using data obtained from the Japanese Subaru telescope in Mauna Kea, Hawaii, a team of astronomers discovered something strange inside: a small cloud of hot gas isolated and not associated with any galaxy in the cluster. In short, an orphan cloud.

Now, thanks to new observations made using the ESA Xmm-Newton X-ray telescope , the same Subaru telescope and ESO ‘s Very Large Telescope (Vlt), a team of astronomers led by the University of Alabama at Huntsville ( Usa) has measured some salient features, discovering that the cloud is actually larger than the Milky Way and that the gas it is made of has a different origin from that of the medium in which it is located. These are the first observations of a mass of intracluster hot gas detected both in X-rays and in visible light.

The cloud in question is the umbrella-shaped structure you see in the opening image highlighted in blue, the color associated with the energy of the X radiation emitted by the gas in the cloud and captured by Xmm-Newton. In the article published in Monthly Notice of the Royal Astronomical Society, the authors describe it as a cloud with a mass equal to about 10 billion times that of the Sun, made of interstellar gas torn away from a galaxy of the cluster and “stranded” in the space between galaxies permeated by intracluster medium – plasma superheated to millions of degrees.

Its temperature suggests that the gas comes from intragalactic. The interstellar medium is much colder than the intergalactic medium, the researchers explain, and the temperature of the orphan cloud matches that of the interstellar gas. Gas that may have been blown out of the galaxy as it moved through the cluster, then floated for a long time in the space between galaxies, making its simple survival surprising, the researchers note.

And speaking of survival, the authors of the study were also able to determine what allowed the orphan cloud to last for so long: the merit would be of its magnetic field, able to counteract instabilities caused by differences in speed and density of the interstellar hot gas versus intracluster plasma . As for the mother galaxy that originated the cloud, considering the enormous mass of gas it is made of, according to the researchers it is probably a massive galaxy, whose name could be discovered with future observations.

This study paves the way for the search for intracluster clusters , the researchers conclude, as future hot gas investigations can now be aimed at looking for other orphan clouds.

Featured image: Three-color composite image of the X-band and visible emission of the region around the Abell 1367 orphan cloud. In blue, the X-ray emission of the cloud. In red the emission of hot gas. In white the optical emission of some of the galaxies in the cluster. Credits: Chong Ge et al., 2021

To know more:

  • Read on Monthly Notices of the Royal Astronomical Society the article ” An H α / X-ray orphan cloud as a signpost of intracluster medium clumping ” by Chong Ge, Rongxin Luo, Ming Sun, Masafumi Yagi, Pavel Jáchym, Alessandro Boselli, Matteo Fossati, Paul EJ Nulsen, Craig Sarazin, Tim Edge, Giuseppe Gavazzi, Massimo Gaspari, Jin Koda, Yutaka Komiyama and Michitoshi Yoshida

Provided by INAF

Hubble Observed Rings Of Relativity (Astronomy /Cosmology)

The narrow galaxy elegantly curving around its spherical companion in this image is a fantastic example of a truly strange and very rare phenomenon. This image, taken with the NASA/ESA Hubble Space Telescope, depicts GAL-CLUS-022058s, located in the southern hemisphere constellation of Fornax (The Furnace). GAL-CLUS-022058s is the largest and one of the most complete Einstein rings ever discovered in our Universe. The object has been nicknamed by the Principal Investigator and his team who are studying this Einstein ring as the “Molten Ring”, which alludes to its appearance and host constellation.

GAL-CLUS-022058s Credit:ESA/Hubble & NASA, S. Jha

First theorised to exist by Einstein in his general theory of relativity, this object’s unusual shape can be explained by a process called gravitational lensing, which causes light shining from far away to be bent and pulled by the gravity of an object between its source and the observer. In this case, the light from the background galaxy has been distorted into the curve we see by the gravity of the galaxy cluster sitting in front of it. The near exact alignment of the background galaxy with the central elliptical galaxy of the cluster, seen in the middle of this image, has warped and magnified the image of the background galaxy around itself into an almost perfect ring. The gravity from other galaxies in the cluster is soon to cause additional distortions.

Objects like these are the ideal laboratory in which to research galaxies too faint and distant to otherwise see.

Provided by ESA/Hubble

The Universe Is Getting Hot, Hot, Hot, A New Study Suggests (Astronomy)

Temperature has increased about 10 times over the last 10 billion years.

The universe is getting hotter, a new study has found.

The study, published Oct. 13 in the Astrophysical Journal, probed the thermal history of the universe over the last 10 billion years. It found that the mean temperature of gas across the universe has increased more than 10 times over that time period and reached about 2 million degrees Kelvin today — approximately 4 million degrees Fahrenheit.

A new study has found that the universe is getting hotter. Credit: Greg Rakozy on Unsplash.

“Our new measurement provides a direct confirmation of the seminal work by Jim Peebles — the 2019 Nobel Laureate in Physics — who laid out the theory of how the large-scale structure forms in the universe,” said Yi-Kuan Chiang, lead author of the study and a research fellow at The Ohio State University Center for Cosmology and AstroParticle Physics.

The large-scale structure of the universe refers to the global patterns of galaxies and galaxy clusters on scales beyond individual galaxies. It is formed by the gravitational collapse of dark matter and gas.

“As the universe evolves, gravity pulls dark matter and gas in space together into galaxies and clusters of galaxies,” Chiang said. “The drag is violent — so violent that more and more gas is shocked and heated up.”

The findings, Chiang said, showed scientists how to clock the progress of cosmic structure formation by “checking the temperature” of the universe.

The researchers used a new method that allowed them to estimate the temperature of gas farther away from Earth — which means further back in time — and compare them to gases closer to Earth and near the present time. Now, he said, researchers have confirmed that the universe is getting hotter over time due to the gravitational collapse of cosmic structure, and the heating will likely continue.

To understand how the temperature of the universe has changed over time, researchers used data on light throughout space collected by two missions, Planck and the Sloan Digital Sky Survey. Planck is the European Space Agency mission that operates with heavy involvement from NASA; Sloan collects detailed images and light spectra from the universe.

As the universe evolves, matter concentrations are surrounded by gas halos getting hotter and bigger. (Credit: D. Nelson / Illustris Collaboration)

They combined data from the two missions and evaluated the distances of the hot gases near and far via measuring redshift, a notion that astrophysicists use to estimate the cosmic age at which distant objects are observed. (“Redshift” gets its name from the way wavelengths of light lengthen. The farther away something is in the universe, the longer its wavelength of light. Scientists who study the cosmos call that lengthening the redshift effect.)

The concept of redshift works because the light we see from objects farther away from Earth is older than the light we see from objects closer to Earth — the light from distant objects has traveled a longer journey to reach us. That fact, together with a method to estimate temperature from light, allowed the researchers to measure the mean temperature of gases in the early universe — gases that surround objects farther away — and compare that mean with the mean temperature of gases closer to Earth — gases today.

Those gases in the universe today, the researchers found, reach temperatures of about 2 million degrees Kelvin — approximately 4 million degrees Fahrenheit, around objects closer to Earth. That is about 10 times the temperature of the gases around objects farther away and further back in time.

The universe, Chiang said, is warming because of the natural process of galaxy and structure formation. It is unrelated to the warming on Earth. “These phenomena are happening on very different scales,” he said. “They are not at all connected.”

References : Chiang, Yi-Kuan; Makiya, Ryu; Ménard, Brice; Komatsu, Eiichiro, “The Cosmic Thermal History Probed by Sunyaev-Zeldovich Effect Tomography”, The Astrophysical Journal, Volume 902, Issue 1, id.56, 17 doi:10.3847/1538-4357/abb403 https://ui.adsabs.harvard.edu/abs/2020ApJ.902.56C/abstract

Provided by Ohio state University

Hubble Captured Snapshot Of Distorted Galaxy LRG-3-817 (Astronomy)

This NASA/ESA Hubble Space Telescope image features the galaxy LRG-3-817, also known as SDSS J090122.37+181432.3. The galaxy, its image distorted by the effects of gravitational lensing, appears as a long arc to the left of the central galaxy cluster.

Credit: ESA/Hubble & NASA, S. Allam et al.

Gravitational lensing occurs when a large distribution of matter, such as a galaxy cluster, sits between Earth and a distant light source. As space is warped by massive objects, the light from the distant object bends as it travels to us and we see a distorted image of it. This effect was first predicted by Einstein’s general theory of relativity.

Strong gravitational lenses provide an opportunity for studying properties of distant galaxies, since Hubble can resolve details within the multiple arcs that are one of the main results of gravitational lensing. An important consequence of lensing distortion is magnification, allowing us to observe objects that would otherwise be too far away and too faint to be seen. Hubble makes use of this magnification effect to study objects beyond the sensitivity of its 2.4-metre-diameter primary mirror, showing us the most distant galaxies humanity has ever encountered.

This lensed galaxy was found as part of the Sloan Bright Arcs Survey, which discovered some of the brightest gravitationally lensed high-redshift galaxies in the night sky.

Provided by ESA/Hubble

Fast-Rotating Stars At The Centre Of The Milky Way Could Have Migrated From The Outskirts Of The Galaxy (Astronomy)

A newly discovered group of stars at the centre of our galaxy could have migrated from a star cluster or dwarf galaxy located more than 320,000 light-years away, reports a new ground-breaking study.

This is an artist’s concept of the fastest rotating star found to date. The massive, bright young star, called VFTS 102, rotates at a million miles per hour, or 100 times faster than our Sun does. Centrifugal forces from this dizzying spin rate have flattened the star into an oblate shape and spun off a disk of hot plasma, seen edge on in this view from a hypothetical planet. Image Credit: NASA, ESA, and G. Bacon (STScI)

In a research paper published by The Astrophysical Journal Letters, an international team of astrophysicists, including scientists from the University of Surrey, detail how they discovered a group of stars with different characteristics than their neighbours found in the Milky Way’s Nuclear Star Cluster (NSC).

The team used state-of-the-art high-resolution computer simulations to explain how this group of metal-poor and fast-rotating stars came to be located at the centre of our galaxy.

Their calculations found that it is likely that this group of stars are leftovers from the migration of a massive star cluster that formed a few light-years away from the Milky Way’s centre. Alternatively, while not as likely as the cluster scenario, the team also noted that the group of stars could possibly have originated from a dwarf galaxy located up to 320,000 light-years away from the galactic centre.

All evidence points towards an accretion event that happened 3-5 billion years ago during which a massive cluster migrated towards the centre of the Milky Way and was disrupted by the strong tidal forces of the NSC, a region of high stellar density. Cluster stars were deposited in the region and were discovered based on their peculiar velocities and low metal content.

Dr Alessia Gualandris, Senior Lecturer in Physics from the University of Surrey, added: “This discovery may be the ‘smoking gun’ evidence that the Milky Way has been accreting star clusters or dwarf galaxies over its lifetime. Its past was much more active than we previously thought.”

Dr Tuan Do, Assistant Research Scientist at UCLA, said: “It is remarkable how these new observations of the NSC can reveal so much about the history of the whole galaxy.”

Dr Manuel Arca-Sedda, a Humboldt Fellow at the Astronomisches Rechen-Institut, Heidelberg, concluded: “A close collaboration between observers and theorists has been key in this study. Combining new exquisite observations with state-of-the-art computer models has allowed us to uncover the birthplace of these peculiar stars”.

References: (1) Tuan Do et al. Revealing the Formation of the Milky Way Nuclear Star Cluster via Chemo-dynamical Modeling, The Astrophysical Journal (2020). DOI: 10.3847/2041-8213/abb246 (2) Manuel Arca Sedda et al. On the Origin of a Rotating Metal-poor Stellar Population in the Milky Way Nuclear Cluster, The Astrophysical Journal (2020). DOI: 10.3847/2041-8213/abb245

Provided by University Of Surrey

Five New Giant Radio Galaxies Discovered (Astronomy)

With the help of citizen scientists, astronomers have detected five new giant radio galaxies (GRGs). The new GRGs have sizes ranging from 2.3 to 2.6 million light years, and have been identified at redshift between 0.28 and 0.43.

One of new GRGs described in the study. The figure shows radio-near infrared overlay of this source, using SDSS i-band image rather than WISE, given its better angular resolution. Credit: Tang et al., 2020

GRGs are radio galaxies with an overall projected linear length exceeding at least 2.28 million light years. They are rare objects grown in low-density environments. GRGs are important for astronomers to study the formation and the evolution of radio sources.

Now, a team of astronomers led by Hongming Tang of the University of Manchester, UK, reports the finding of five previously unknown GRGs. The detection is based on the Data Release 1 (DR1) of the Radio Galaxy Zoo (RGZ) citizen science project. RGZ DR1 is a manually cross-matched radio galaxy catalog using the efforts of more than 12,000 citizen scientist volunteers.

In their paper, they presented the identification of five previously unknown giant radio galaxies (GRGs) using Data Release 1 of the Radio Galaxy Zoo citizen science project and a selection method appropriate to the training and validation of deep-learning algorithms for new radio surveys.

The newly identified GRGs are designated J0941+3126, J1331+2557, J1402+2442, J1421+1016 and J1646+3627. They all have comparatively high radio luminosities and are likely to be either elliptical or intermediate disk galaxies.

J1402+2442 (also known as B2 1400+24) is the largest out of the newly found GRGs. It has a redshift of approximately 0.337 and its host is a close pair of galaxies, designated SDSS J140224.25+244224.3 and SDSS J140224.31+244226.8. At a redshift of about 0.28, J0941+3126 (or B2 0938+31A) is the smallest GRG from the five reported in the study. This source is hosted by SDSS J094103.62+312618.7.

In the case of J1646+3627, a GRG with a size of at least 2.46 million light years, at a redshift of 0.43, the researchers found that this object is also the brightest cluster galaxy (BCG) in the galaxy cluster GMBCG J251.67741+36.45295. This finding motivated Tang’s team to conduct further study of BCGs. They report that 13 previously known GRGs could be classified as BCG candidates. If confirmed, this would increase the number of known BCG GRGs by more than 60 percent.

The remaining two giant radio galaxies described in the study, namely J1331+2357 and J1421+1016, have sizes of about 2.62 and 2.49 million light years, respectively. J1331+2357 has a redshift of 0.33 and its host galaxy is identified as SDSS J133118.01+235700.4, while J1421+1016, at a redshift of 0.37, has a host galaxy known as SDSS J142142.68+101626.2.

References: Tang et al., Radio Galaxy Zoo: New Giant Radio Galaxies in the RGZ DR1 catalog, arXiv:2009.03583 [astro-ph.GA]. arxiv.org/abs/2009.03583 link: https://arxiv.org/abs/2009.03583