Exploring the Slower Side of Neutron-Star Bow Shocks

This false-color infrared image from the Spitzer Space Telescope shows the arched bow shock generated as blue supergiant Kappa Cassiopeiae hurtles through the interstellar medium. Credit: NASA/JPL-Caltech

Title: Probing the Low-Velocity Regime of Nonradiative Shocks with Neutron Star Bow Shocks
Authors: Stella Koch Ocker and Maren Cosens
First Author’s Institution: California Institute of Technology and Observatories of the Carnegie Institution for Science
Status: Published in ApJL

Neutron stars are fascinating remnants of massive stars that have undergone a supernova explosion. These stellar remnants often move at incredible speeds through space, producing bow shocks, the regions where the fast-moving neutron star collides with interstellar gas. Imagine a cosmic wind so powerful that it creates a shock wave in space, much like a speedboat cutting through water. These powerful shock waves hold clues to study non-radiative shocks, which play an important role in heating plasma and accelerating particles, such as cosmic rays. Today’s article took a closer look at the properties of three neutron-star bow shocks in unprecedented detail, revealing new insights into the hidden physics behind these cosmic collisions.

Figure 1: Image of the LL Orionis bow shock taken with the Hubble Space Telescope.
Credit: NASA and The Hubble Heritage Team (STScI/AURA); Acknowledgment: C. R. O’Dell (Vanderbilt University)

What Are Bow Shocks?

A bow shock forms when a fast-moving object, like a neutron star, passes through a medium — in this case, the interstellar medium, the gas and dust that fills the space between stars. The interaction between the neutron star’s wind and the interstellar medium causes form a shock wave, which resembles the bow wave that forms at the front of a boat moving through water (for example, see Figure 1).

In the context of neutron stars, the bow shock is non-radiative, meaning it does not emit much in the form of light or heat. However, the shock does produce a particular type of emission called Hα (hydrogen alpha), which occurs when neutral hydrogen atoms in the interstellar medium are excited and emit light at a specific wavelength in the optical wavelength range. Observing this Hα emission is one of the main ways astronomers can study neutron-star bow shocks.

Figure 2: KCWI data of the three neutron-star bow shocks, showing the morphologies of each bow shock at different velocity slices. Credit: Ocker & Cosens 2024

Understanding the Shock’s Velocity and Structure

Today’s authors focused on three known neutron-star bow shocks (see Figure 2): J0742−2822, J1741−2054, and J2225+6535 (also known as the “Guitar Nebula”). Using integral field spectroscopy, a technique that captures both the spatial and spectral information of an object, they were able to observe these bow shocks in detail. For their observations, they used the Keck Cosmic Web Imager (KCWI) on the Keck II Telescope in Hawaii. Unlike traditional spectroscopy, which provides a one-dimensional spectrum of light from a single region, integral field spectroscopy collects spectra across a two-dimensional field, allowing the astronomers to map the shock properties. This allows astronomers to study the shock shape, velocity structure, and Hα emission intensity in exquisite detail, giving a more complete picture of how these shocks behave.

Studying the relative contributions to the Hα emission is crucial to unlocking the detailed shock physics. There are two main components to the Hα emission: a narrow line that represents the ambient gas in the interstellar medium and a broad line produced by the shock itself. The ratio between these two lines, the broad-to-narrow line intensity ratio (Ib/In), provides crucial information about the velocity of the shock and the processes occurring within it, including the electron-ion temperature and the particle energy distribution.

The study revealed that the Ib/In values for all three neutron-star bow shocks indicated low shock velocities, all below 200 kilometers per second. This is notably different from the much higher velocities seen in supernova remnants, where shocks can exceed 1,000 kilometers per second. These results suggest that neutron-star bow shocks operate in a distinct low-velocity regime, and current models, which are designed for higher-velocity shocks, may not fully capture the behavior of these slower shocks. To better understand the temperature ratios between electrons and ions, as well as how particles are accelerated in this regime, new models are needed.

Why Is the Low-Velocity Regime Important?

Understanding the low-velocity regime of non-radiative shocks is important for several reasons:

• Cosmic-Ray Acceleration: Non-radiative shocks are believed to accelerate particles to very high speeds, contributing to the population of cosmic rays — high-energy charged particles that travel through space. Studying how these shocks operate at different velocities helps scientists understand how cosmic rays are produced and what role neutron stars might play in this process.
• Energy Transfer in Shocks: Non-radiative shocks are also key to understanding how energy is transferred between different types of particles, such as electrons and protons. In faster shocks, the temperature of electrons and protons can differ significantly, but in slower shocks, like those studied here, the temperatures might be more equal. Understanding this balance provides insight into the physics of shock waves and how they heat and accelerate particles.
• Astrophysical Modeling: Most models of non-radiative shocks are based on high-velocity shocks in supernova remnants. However, the findings from this study suggest that these models need to be expanded to include slower shocks, which behave differently and require new theoretical approaches.

This study provides critical new insights into the enigmatic nature of neutron-star bow shocks, particularly in the unexplored low-velocity regime. By probing these slow shocks, we unlock a deeper understanding of how astrophysical plasmas are heated and how particles are accelerated to cosmic-ray speeds — shedding light on some of the most powerful processes in the universe. The findings challenge existing models of non-radiative shocks, emphasizing the need for new theory to capture the unique behavior of these slower shocks. As a result, this research not only reshapes our understanding of cosmic rays but also paves the way for exciting new directions in astrophysics, with potential breakthroughs on the horizon.

Original astrobite edited by Megan Masterson.

Source: American Astronomical Society/AA-Nova

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About the author, Janette Suherli:

Janette is a PhD student at University of Manitoba in Winnipeg, Canada. Her research focuses on the utilization of integral field spectroscopy for the studies of supernova remnants and their compact objects in the optical. She is also the current chair of Graduate Student Committee for the Canadian Astronomical Society (CASCA). She grew up in Indonesia where it is summer all year round! Before pursuing her PhD in astrophysics, Janette worked as a data analyst for a big Indonesian tech company, combating credit card fraud.

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Editor’s Note:  Astrobites is a graduate-student-run organization that digests astrophysical literature for undergraduate students. As part of the partnership between the AAS and astrobites, we occasionally repost astrobites content here at AAS Nova. We hope you enjoy this post from astrobites; the original can be viewed at astrobites.org.

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Cosmic Web Lights Up in the Darkness of Space

A mosaic of images captured using W. M. keck Observatory's keck cosmic web imager showing the filaments of gas that make up the cosmic web. the green dots mark known galaxies the filaments connect to. Credit: C. Martin et al./Caltech/W. M. Keck Observatory

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Keck Cosmic Web Imager Offers Best Glimpse Yet of the Filamentous Network That Connects Galaxies

Maunakea, Hawaiʻi Like rivers feeding oceans, streams of gas nourish galaxies throughout the cosmos. But these streams, which make up a part of the so-called cosmic web, are very faint and hard to see. While astronomers have known about the cosmic web for decades, and even glimpsed the glow of its filaments around bright cosmic objects called quasars, they have not directly imaged the extended structure in the darkest portions of space—until now.

New results from the Keck Cosmic Web Imager, or KCWI, which was designed by Caltech’s Edward C. Stone Professor of Physics Christopher Martin and his team, are the first to show direct light emitted by the largest and most hidden portion of the cosmic web: the crisscrossing wispy filaments that stretch across the darkest corners of space between galaxies. The KCWI instrument is based at the W. M. Keck Observatory atop Maunakea in Hawaiʻi.

“We chose the name Keck Cosmic Web Imager for our instrument because we were hoping it would directly detect the cosmic web,” says Martin, who is also the director of the Caltech Optical Observatories, which includes Caltech’s portion of Keck Observatory; other Keck Observatory partners are the University of California and NASA. “I’m very happy it worked out.”

Galaxies in our universe condense out of swirling clouds of gas. That gas then further condenses into stars that light up the galaxies, making them visible to telescopes in a range of wavelengths of light. Astronomers think that cold, dark filaments in deep space snake their way to the galaxies, supplying them with gas, which is fuel for making more stars. In 2015, Martin and his colleagues found “smoking-gun evidence,” as Martin describes it, for this so-called cold-flow model of galaxy formation: a long filament funneling gas into a large galaxy. For this work, they used a prototype instrument to KCWI, the Cosmic Web Imager, which was based at Caltech’s Palomar Observatory.

In that case, the filament was being lit up by a nearby quasar, the bright nucleus of a young galaxy. But most of the cosmic web lies in the desolate territory between galaxies and is hard to image.

“Before this latest finding, we saw the filamentary structures under the equivalent of a lamppost,” says Martin. “Now we can see them without a lamp.”

The new findings appear in a paper published in Nature Astronomy on September 28.

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Detecting the Cosmic Web

This animation reveals a 3-D slice through a network of hydrogen gas filaments that crisscross the spaces between galaxies. The data were collected by the Keck Cosmic Web Imager, or KCWI, which was designed to reveal the structure of this previously hidden component of the universe. The region covered in this observation is about 10.5 billion light-years away. The volume depicted here spans an area of 2.3 by 3.2 million light-years and extends across a depth of 600 million light-years (50 million per segment). Credit: Caltech/R. Hurt (IPAC)

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Martin has been driven to reveal the cosmic web in its full glory ever since he was a graduate student. This detailed imaging of the web, he says, will provide astronomers with missing information they need to understand the details of how galaxies form and evolve. It can also help astronomers map the distribution of dark matter in our universe (dark matter makes up about 85 percent of all matter in the universe, but scientists still don’t know what it is made of).

“The cosmic web delineates the architecture of our universe,” he says. “It’s where most of the normal, or baryonic, matter in our galaxy resides and directly traces the location of dark matter.”

The Feeble Glow of Filaments

The best way to see the cosmic web directly is to pick up signatures of its main component, hydrogen gas, using instruments called spectrometers, which spread light out into a multitude of wavelengths, also known as a spectrum. Hydrogen gas can be identified within these spectra via its strongest emission line, called the Lyman alpha line. Martin and his colleagues designed KCWI to find these faint Lyman alpha signatures across a two-dimensional (2D) image of the cosmos (hence KCWI is known as an imaging spectrometer). The instrument’s first installment covers the “blue” portion of the visible-light spectrum, spanning wavelength ranges from 350 to 560 nanometers. (The second part of the instrument, called the Keck Cosmic Reionization Mapper, or KCRM, which sees the red, or longer-wavelength portion, of the visible spectrum, was recently installed at Keck Observatory).

KCWI’s precise spectrometers can look for the Lyman alpha signatures of the cosmic web across a range of wavelengths. Because of the expansion of the universe, which stretches light to longer wavelengths, gas that is located farther away from Earth has a redder Lyman alpha signature. The 2D images captured by KCWI at each wavelength of light can be stacked together to make a three-dimensional (3D) map of the emission from the cosmic web. For this observation, KCWI observed a region of space between 10 and 12 billion light-years away.

“We are basically creating a 3D map of the cosmic web,” Martin explains. “We take spectra for every point in an image at range of wavelengths, and the wavelengths translate to distance.”

Confusion with the Diffuse Light of Space

One challenge in detecting the cosmic web is that its dim light can be confused with nearby background light that suffuses the skies above Maunakea, including the glow from the atmosphere, zodiacal light from the solar system (generated when sunlight scatters off interplanetary dust), and even our own galaxy’s light.

To solve this problem, Martin came up with a new strategy to subtract this background light from the images of interest.

“We look at two different patches of sky, A and B. The filament structures will be at distinct distances in the two directions in the patches, so you can take the background light from image B and subtract it from A, and vice versa, leaving just the structures. I ran detailed simulations of this in 2019 to convince myself that this method would work,” he says.

The result is that astronomers now have “a whole new way to study the universe,” as Martin says.

“With KCRM, the newly deployed red channel of KCWI, we can see even farther into the past,” says senior instrument scientist Mateusz Matuszewski. “We are very excited about what this new tool will help us learn about the more distant filaments and the era when the first stars and black holes formed.”

Speaking of new ways to view the universe, Martin teamed up with artist Matt Schumaker to translate data from the cosmic web into music for a project called “Spiral, supercluster, filament, wall (after Michael Anderson).” The project celebrates the life of Anderson, who perished along with his fellow astronauts in the Space Shuttle Columbia accident in 2003. Martin, who “pretended the filaments were giant violin strings,” translated the filaments’ masses to frequencies based around the note middle C. The piece can be heard here.

The Nature Astronomy study, titled “Extensive diffuse Lyman alpha emission correlated with cosmic structure,” was funded by the National Science Foundation and Caltech.

Source: W.M.Keck Observatory

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About KCWI

The Keck Cosmic Web Imager (KCWI) is designed to provide visible band, integral field spectroscopy with moderate to high spectral resolution formats and excellent sky-subtraction. The astronomical seeing and large aperture of the telescope enables studies of the connection between galaxies and the gas in their dark matter halos, stellar relics, star clusters, and lensed galaxies. KCWI covers the blue side of the visible spectrum; the instrument also features the Keck Cosmic Reionization Mapper (KCRM), extending KCWI’s coverage to the red side of the visible spectrum. The combination of KCWI-blue and KCRM provides simultaneous high-efficiency spectral coverage across the entire visible spectrum. Support for KCWI was provided by the National Science Foundation, Heising-Simons Foundation, and Mt. Cuba Astronomical Foundation. Support for KCRM was provided by the National Science Foundation and Mt. Cuba Astronomical Foundation.

About W. M. Keck Observatory

The W. M. Keck Observatory telescopes are among the most scientifically productive on Earth. The two 10-meter optical/infrared telescopes atop Maunakea on the Island of Hawaii feature a suite of advanced instruments including imagers, multi-object spectrographs, high-resolution spectrographs, integral-field spectrometers, and world-leading laser guide star adaptive optics systems. Some of the data presented herein were obtained at Keck Observatory, which is a private 501(c) 3 non-profit organization operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation. The authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Maunakea has always had within the Native Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain..

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First Ever 3D Map of Messier 87 Galaxy Assembled

An image of the M87 galaxy captured with nasa's hubble space telescope.

Credit: NASA, ESA, Hubble Heritage Team (STScI/AURA); Acknowledgment: P. Cote (Herzberg Institute of Astrophysics), E. Baltz (Stanford University)

Maunakea, Hawaiʻi – A UC Berkeley-led team of astronomers has for the first time measured the three-dimensional shape of Messier 87 (M87), one of the biggest and closest elliptical galaxies to us. New data from W. M. Keck Observatory on Maunakea in Hawaiʻi show M87 isn’t perfectly symmetrical after all, but rather triaxial – similar to the uneven shape of a potato.

The study is published in The Astrophysical Journal Letters.

Located about 55 million light-years away from Earth in the constellation Virgo, M87 is close enough to see using binoculars or a small telescope. As with most celestial objects viewed from our vantage point, M87 appears flat.

The galaxy’s true form revealed itself through the lens of Keck Observatory’s cutting-edge instrument called the Keck Cosmic Web Imager (KCWI), which captures 3D data as opposed to the traditional 2D image or spectrum from conventional instruments.

The researchers used KCWI along with star brightness measurements of M87 from NASA’s Hubble Space Telescope to assemble a 3D view of the motion of stars orbiting M87’s supermassive black hole, named Pōwehi by Larry Kimura, a Hawaiian language professor at the University of Hawaiʻi at Hilo. This provided fresh insight into the galaxy’s shape and allowed the team to calculate with higher precision Pōwehi’s mass, which came out to about 5.4 billion times the mass of the Sun. Previous measurements taken in 2017 when the Event Horizon Telescope (EHT) snapped a direct image of Pōwehi found its mass to be about 6.5 billion solar masses.

Pōwehi means ‘embellished dark source of unending creation’ in Hawaiian and is the world’s first black hole to have its picture taken using EHT’s network of telescopes around the planet, including two Maunakea Observatories – the James Clerk Maxwell Telescope and the Submillimeter Array.

A photo of the huge elliptical galaxy M87 [left] is compared to its three-dimensional shape as gleaned from meticulous observations made with the Hubble and Keck telescopes [right]. Because the galaxy is too far away for astronomers to employ stereoscopic vision, they instead followed the motion of stars around the center of M87, like bees around a hive. This created a three-dimensional view of how stars are distributed within the galaxy. Credit: NASA, ESA, Joseph Olmsted (STScI), Frank Summers (STScI), Chung-Pei Ma (UC Berkeley)

While KCWI was unable to resolve the individual stars due to M87’s great distance from Earth, it was able to obtain spectra that revealed the range of the stars’ velocities as they whizzed around Pōwehi.

“It’s sort of like looking at a swarm of 100 billion bees that are going around in their own happy orbits,” said Chung-Pei Ma, a UC Berkeley professor of astronomy and of physics who led the research team. “Though we are looking at them from a distance and can’t discern individual bees, we are getting very detailed information about their collective velocities. It’s really the superb sensitivity of this spectrograph that allowed us to map out M87 so comprehensively.”

Ma, UC Berkeley graduate student and lead author of the study Emily Liepold, and Jonelle Walsh at Texas A&M University pointed the Keck II telescope at 62 locations across the galaxy and captured KCWI spectra of stars covering a region spanning 70,000 light years across. Gravity in the central 3,000 light-years of this region is largely dominated by Pōwehi. This marked the first time KCWI has been used to reconstruct the geometry of a distant galaxy.

“The Keck data are so good that we can measure the intrinsic shape of M87 along with the black hole at the same time,” said Ma. “We made the first measurement of the actual 3D shape of the galaxy. And since we allowed the swarm of bees to have a more general shape than just a sphere or disk, we have a more robust dynamical measurement of the mass of the central black hole that is governing the bees’ orbiting velocities.”

Ma’s team was also able to measure M87’s rotation, which clocks in at a relatively sedate 25 kilometers per second.

The new findings pave the way for an exciting investigation into M87 that wasn’t possible before – determining Pōwehi’s spin.

“Now that we know the direction of the net rotation of stars in M87 and have an updated mass of the black hole, we can combine this information with the amazing data from the EHT team to constrain the spin,” said Ma. “This may point toward a certain direction and range of spin for the black hole, which would be remarkable.”

Source: W. M. Keck Observatory

 

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Learn more:

• “3D Picture of Galaxy M87 Helps Pin Down Mass of the Black Hole at its Core” – UC Berkeley Press Release April 13, 2023
• “Giant Galaxy Seen in 3D by NASA’s Hubble Space Telescope and Keck Observatory” – STScI Press Release, April 13, 2023

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About KCWI

The Keck Cosmic Web Imager (KCWI) is designed to provide visible band, integral field spectroscopy with moderate to high spectral resolution formats and excellent sky-subtraction. The astronomical seeing and large aperture of the telescope enables studies of the connection between galaxies and the gas in their dark matter halos, stellar relics, star clusters, and lensed galaxies. Support for this project was provided by the National Science Foundation, Heising-Simons Foundation, and Mt. Cuba Astronomical Foundation.

About W. M. Keck Observatory

The W. M. Keck Observatory telescopes are among the most scientifically productive on Earth. The two 10-meter optical/infrared telescopes atop Maunakea on the Island of Hawaii feature a suite of advanced instruments including imagers, multi-object spectrographs, high-resolution spectrographs, integral-field spectrometers, and world-leading laser guide star adaptive optics systems. Some of the data presented herein were obtained at Keck Observatory, which is a private 501(c) 3 non-profit organization operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation. The authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Maunakea has always had within the Native Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain.

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Spiraling Filaments Feed Young Galaxies

Artist's impression of a growing galaxy shows gas spiraling in toward the center. new observations from the keck cosmic web imager provide the best evidence yet that cold gas spirals directly into growing galaxies via filamentous structures. much of the gas ends up being converted into stars. Image credit: Adam Makarenko/W. M. Keck Observatory

New data from W. M. Keck Observatory show gas directly spiraling into growing galaxies 

Maunakea, Hawaii – Galaxies grow by accumulating gas from their surroundings and converting it to stars, but the details of this process have remained murky. New observations, made using the Keck Cosmic Web Imager (KCWI) at W. M. Keck Observatory in Hawaii, now provide the clearest, most direct evidence yet that filaments of cool gas spiral into young galaxies, supplying the fuel for stars.

“For the first time, we are seeing filaments of gas directly spiral into a galaxy. It’s like a pipeline going straight in,” says Christopher Martin, a professor of physics at Caltech and lead author of a new paper appearing in the July 1 issue of the journal Nature Astronomy. “This pipeline of gas sustains star formation, explaining how galaxies can make stars on very fast timescales.”

For years, astronomers have debated exactly how gas makes its way to the center of galaxies. Does it heat up dramatically as it collides with the surrounding hot gas? Or does it stream in along thin dense filaments, remaining relatively cold? 

“Modern theory suggests that the answer is probably a mix of both, but proving the existence of these cold streams of gas had remained a major challenge until now,” says co-author Donal O’Sullivan (MS ’15), a PhD student in Martin’s group who built part of KCWI.

KCWI, designed and built at Caltech, is a state-of-the-art spectral imaging camera. Called an integral-field unit spectrograph, it allows astronomers to take images such that every pixel in the image contains a dispersed spectrum of light. Installed at Keck Observatory in early 2017, KCWI is the successor to the Cosmic Web Imager (CWI), an instrument that has operated at Palomar Observatory near San Diego since 2010. KCWI has eight times the spatial resolution and 10 times the sensitivity of CWI. 

“The main driver for building KCWI was understanding and characterizing the cosmic web, but the instrument is very flexible, and scientists have used it, among other things, to study the nature of dark matter, to investigate black holes, and to refine our understanding of star formation,” says co-author Mateusz (Matt) Matuszewski (MS ’02, PhD ’12), a senior instrument scientist at Caltech.

The question of how galaxies and stars form out of a network of wispy filaments in space—what is known as the cosmic web—has fascinated Martin since he was a graduate student. To find answers, he led the teams that built both CWI and KCWI. In 2017, Martin and his team used KCWI to acquire data on two active galaxies known as quasars, named UM 287 and CSO 38, but it was not the quasars themselves they wanted to study.

Nearby each of these two quasars is a giant nebula, larger than the Milky Way and visible thanks to the strong illumination of the quasars. By looking at light emitted by hydrogen in the nebulas—specifically an atomic emission line called hydrogen Lyman-alpha—they were able to map the velocity of the gas. From previous observations at Palomar, the team already knew there were signs of rotation in the nebulas, but the Keck Observatory data revealed much more.

“When we used Palomar’s CWI previously, we were able to see what looked like a rotating disk of gas, but we couldn’t make out any filaments,” says O’Sullivan. “Now, with the increase in sensitivity and resolution with KCWI, we have more sophisticated models and can see that these objects are being fed by gas flowing in from attached filaments, which is strong evidence that the cosmic web is connected to and fueling this disk.”

Martin and colleagues developed a mathematical model to explain the velocities they were seeing in the gas and tested it on UM287 and CSO38 as well as on a simulated galaxy.

“It took us more than a year to come up with the mathematical model to explain the radial flow of the gas,” says Martin. “Once we did, we were shocked by how well the model works.”

The findings provide the best evidence to date for the cold-flow model of galaxy formation, which basically states that cool gas can flow directly into forming galaxies, where it is converted into stars. Before this model came into popularity, researchers had proposed that galaxies pull in gas and heat it up to extremely high temperatures. From there, the gas was thought to gradually cool, providing a steady but slow supply of fuel for stars.

In 1996, research from Caltech’s Charles (Chuck) Steidel, the Lee A. DuBridge Professor of Astronomy and a co-author of the new study, threw this model into question. He and his colleagues showed that distant galaxies produce stars at a very high rate—too fast to be accounted for by the slow settling and cooling of hot gas that was a favored model for young galaxy fueling.

“Through the years, we’ve acquired more and more evidence for the cold-flow model,” says Martin. “We have nicknamed our new version of the model the ‘cold-flow inspiral,’ since we see the spiraling pattern in the gas.”

“These type of measurements are exactly the kind of science we want to do with KCWI,” says John O’Meara, Keck Observatory chief scientist. “We combine the power of Keck’s telescope size, powerful instrumentation, and an amazing astronomical site to push the boundaries of what’s possible to observe. It’s very exciting to see this result in particular, since directly observing inflows has been something of a missing link in our ability to test models of galaxy formation and evolution. I can’t wait to see what’s coming next.”

The new study, titled, “Multi-Filament Inflows Fuel Young Star Forming Galaxies,” was funded by the National Science Foundation (NSF), Keck Observatory, Caltech, and the European Research Council. The galaxy simulations were performed at NASA Advanced Supercomputing at NASA Ames Research Center. Other Caltech authors include former postdoc Erika Hamden, now at the University of Arizona; Patrick Morrissey, a visitor in space astrophysics who also works at JPL, which is managed by Caltech for NASA; and research scientist James D. (Don) Neill.

Source:  W.M. Keck Observatory

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About KCWI

The Keck Cosmic Web Imager (KCWI) is designed to provide visible band, integral field spectroscopy with moderate to high spectral resolution formats and excellent sky-subtraction. The astronomical seeing and large aperture of the telescope will enable studies of the connection between galaxies and the gas in their dark matter halos, stellar relics, star clusters, and lensed galaxies. Support for this project was provided by Caltech, Gordon and Betty Moore Foundation, the Heising-Simons Foundation, Mt. Cuba Astronomical Foundation, NSF, and other Friends of Keck Observatory.

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About W.M.Keck Observatory

The W. M. Keck Observatory telescopes are the most scientifically productive on Earth. The two, 10-meter optical/infrared telescopes atop Maunakea on the Island of Hawaii feature a suite of advanced instruments including imagers, multi-object spectrographs, high-resolution spectrographs, integral-field spectrometers, and world-leading laser guide star adaptive optics systems. The data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation. The authors recognize and acknowledge the very significant cultural role that the summit of Maunakea has always had within the Native Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain.

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