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  • richardmitnick 3:13 pm on October 20, 2016 Permalink | Reply
    Tags: , , Dragonfly telescope array,   

    From Symmetry: “99 percent invisible” 

    Symmetry Mag

    Laura Dattaro

    Dragonfly. Pieter van Dokkum

    With a small side project, astronomers discover a new type of galaxy.

    In 2011, astronomers Pieter van Dokkum and Roberto “Bob” Abraham found themselves in a restaurant in Toronto nursing something of a mid-life crisis. Abraham, a professor at the University of Toronto, and van Dokkum, at Yale, had become successful scientists, but they discovered that often meant doing less and less science and more and more managing large, complex projects.

    “They’re important and they’re great and you feel this tremendous obligation once you’ve reached a certain age to serve on these committees because you have to set things up for the next generation,” Abraham says. “At the same time, it was no longer very much fun.”

    The two friends fantasized about finding a small, manageable project that might still have some impact. By the time a few hours had passed, they picked an idea: using new camera lenses to find objects in the sky that emit very little light.

    They had no way of knowing then that within the next five years, they’d discover an entirely new class of galactic object.

    From the handmade telescopes of Galileo to spacefaring technological marvels like Hubble, all telescopes are designed for one basic task: gathering light. Telescope technology has advanced far enough that Hubble can pick up light from stars that were burning just 400 million years after the universe first popped into existence.

    But telescopes often miss objects with light that’s spread out, or diffuse, which astronomers describe as having low surface brightness. Telescopes like Hubble have large mirrors that scatter light from bright objects in the sky, masking anything more diffuse. “There’s this bit of the universe that’s really quite unexplored because our telescope designs are not good at detecting these things,” Abraham says.

    When van Dokkum and Abraham sat down at that bar, they decided to try their hands at studying these cosmic castaways. The key turned out to be van Dokkum’s hobby as an amateur insect photographer. He had heard of new camera lenses developed by Canon that were coated with nanoparticles designed to prevent light scattering. Although they were intended for high-contrast photography—say, snapping a photo of a boat in a sunny bay—van Dokkum thought these lenses might be able to spot diffuse objects in the sky.

    Abraham was skeptical at first: “Yeah, I’m sure the Canon corporation has come up with a magical optical coating,” he recalls thinking. But when the pair took one to a parking lot in a dark sky preserve in Quebec, they were sold on its capabilities. They acquired more and more lenses—not an easy task, at $12,000 a pop—eventually gathering 48 of them, and arranged them in an ever-growing honeycomb shape to form what can rightly be called a telescope. They named it Dragonfly.

    In 2014, both van Dokkum and Abraham were at a conference in Oxford when van Dokkum examined an image that had come in from Dragonfly. (At the time, it had just eight lenses.) It was an image of the Coma Cluster, one of the most photographed galaxy clusters in the universe, and it was dotted with faint smudges that didn’t match any objects in Coma Cluster catalogs.

    Van Dokkum realized these smudges were galaxies, and that they were huge, despite their hazy light. They repeated their observations using the Keck telescope, which enabled them to calculate the velocities of the stars inside their mysterious galaxies. One was measured at 50 kilometers per second, 10 times the speed the galaxy should be moving based on the mass of its stars alone.

    “We realized that for these extremely tenuous objects to survive as galaxies and not be ripped apart by their movement through space and interactions with other galaxies, there must be much more than meets the eye,” van Dokkum says.

    The galaxy, dubbed Dragonfly 44, has less than 1 percent as many stars as the Milky Way, and yet it has to be just as massive.

    Dragonfly 44

    That means that the vast majority of its matter is not the matter that makes up stars and planets and people—everything we can see—but dark matter, which seems to interact with regular matter through gravity alone.

    Astronomers have known for decades that galaxies can be made almost entirely of dark matter. But those galaxies were always small, a class known as dwarf galaxies, which have between 100 million and a few billion stars. A dark-matter-dominated galaxy as large as the Milky Way, with its 200 billion or more stars, needed an entirely new category. Van Dokkum and Abraham coined a term for them: ultradiffuse.

    “You look at a galaxy and you see this beautiful spiral structure and they’re gorgeous. I love galaxies,” Abraham says. “But what you see is really just kind of the frosting on the cake. The cake is the dark matter.”

    No one knows how many of these galaxies might exist, or whether they can have an even larger percentage of dark matter than Dragonfly 44. Perhaps there are galaxies that have no luminous matter at all, simply massive dark blobs hurtling through empty space. Though such galaxies have thus far evaded observation, evidence of their existence may be lurking in unexamined data from the past.

    And Dragonfly could be the key for finding them. “When people knew they were real and that these things could exist and could be part of these galaxy clusters, suddenly they turned up in large numbers,” van Dokkum says. “They just escaped attention for all these decades.”

    See the full article here .

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    Symmetry is a joint Fermilab/SLAC publication.

  • richardmitnick 1:57 pm on August 25, 2016 Permalink | Reply
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    From Keck: “Scientists Discover Massive Galaxy Made of 99.99 Percent Dark Matter” 

    Keck Observatory

    August 25, 2016

    Pieter van Dokkum
    Yale University
    New Haven, Connecticut, USA
    Tel: +1-203-432-3000
    E-mail: pieter.vandokkum@yale.edu


    Steve Jefferson
    W. M. Keck Observatory
    (808) 881-3827

    Keck Observatory.
    Keck, with Subaru and IRTF (NASA Infrared Telescope Facility). Vadim Kurland

    Keck Observatory

    The dark galaxy Dragonfly 44. The image on the left is a wide view of the galaxy taken with the Gemini North telescope using the Gemini Multi-Object Spectrograph (GMOS). The close-up on the right is from the same very deep image, revealing the large, elongated galaxy, and halo of spherical clusters of stars around the galaxy’s core, similar to the halo that surrounds our Milky Way Galaxy. Dragonfly 44 is very faint for its mass, and consists almost entirely of Dark Matter. Credit: Pieter van Dokkum, Roberto Abraham, Gemini; Sloan Digital Sky Survey.

    Using the world’s most powerful telescopes, an international team of astronomers has discovered a massive galaxy that consists almost entirely of Dark Matter. Using the W. M. Keck Observatory and the Gemini North telescope – both on Maunakea, Hawaii – the team found a galaxy whose mass is almost entirely Dark Matter. The findings are being published in The Astrophysical Journal Letters today.

    Gemini/North telescope at Manua Kea, Hawaii, USA
    Gemini/North telescope at Manua Kea, Hawaii, USA; GEMINI/North GMOS

    Even though it is relatively nearby, the galaxy, named Dragonfly 44, had been missed by astronomers for decades because it is very dim. It was discovered just last year when the Dragonfly Telephoto Array observed a region of the sky in the constellation Coma.

    U Toronto Dunlap Dragonfly telescope Array
    U Toronto Dunlap Dragonfly telescope Array

    Upon further scrutiny, the team realized the galaxy had to have more than meets the eye: it has so few stars that it quickly would be ripped apart unless something was holding it together.

    To determine the amount of Dark Matter in Dragonfly 44, astronomers used the DEIMOS instrument installed on Keck II to measure the velocities of stars for 33.5 hours over a period of six nights so they could determine the galaxy’s mass.


    The team then used the Gemini Multi-Object Spectrograph (GMOS) on the 8-meter Gemini North telescope on Maunakea in Hawaii to reveal a halo of spherical clusters of stars around the galaxy’s core, similar to the halo that surrounds our Milky Way Galaxy.

    “Motions of the stars tell you how much matter there is, van Dokkum said. “They don’t care what form the matter is, they just tell you that it’s there. In the Dragonfly galaxy stars move very fast. So there was a huge discrepancy: using Keck Observatory, we found many times more mass indicated by the motions of the stars, then there is mass in the stars themselves.”

    The mass of the galaxy is estimated to be a trillion times the mass of the Sun – very similar to the mass of our own Milky Way galaxy. However, only one hundredth of one percent of that is in the form of stars and “normal” matter; the other 99.99 percent is in the form of dark matter. The Milky Way has more than a hundred times more stars than Dragonfly 44.

    Finding a galaxy with the mass of the Milky Way that is almost entirely dark was unexpected. “We have no idea how galaxies like Dragonfly 44 could have formed,” Roberto Abraham, a co-author of the study, said. “The Gemini data show that a relatively large fraction of the stars is in the form of very compact clusters, and that is probably an important clue. But at the moment we’re just guessing.”

    “This has big implications for the study of Dark Matter,” van Dokkum said. “It helps to have objects that are almost entirely made of Dark Matter so we don’t get confused by stars and all the other things that galaxies have. The only such galaxies we had to study before were tiny. This finding opens up a whole new class of massive objects that we can study.

    “Ultimately what we really want to learn is what Dark Matter is,” van Dokkum said. “The race is on to find massive dark galaxies that are even closer to us than Dragonfly 44, so we can look for feeble signals that may reveal a Dark Matter particle.”

    Additional co-authors are Shany Danieli, Allison Merritt, and Lamiya Mowla of Yale, Jean Brodie of the University of California Observatories, Charlie Conroy of Harvard, Aaron Romanowsky of San Jose State University, and Jielai Zhang of the University of Toronto.

    The W. M. Keck Observatory operates the largest, most scientifically productive telescopes on Earth. The two, 10-meter optical/infrared telescopes near the summit of Maunakea on the Island of Hawaii feature a suite of advanced instruments including imagers, multi-object spectrographs, high-resolution spectrographs, integral-field spectrographs and world-leading laser guide star adaptive optics systems.

    DEIMOS (DEep Imaging Multi-Object Spetrograph) boasts the largest field of view (16.7 arcmin by 5 arcmin) of any of the Keck Observatory instruments, and the largest number of pixels (64 Mpix). It is used primarily in its multi-object mode, obtaining simultaneous spectra of up to 130 galaxies or stars. Astronomers study fields of distant galaxies with DEIMOS, efficiently probing the most distant corners of the universe with high sensitivity.

    See the full article here .

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    To advance the frontiers of astronomy and share our discoveries with the world.

    The W. M. Keck Observatory operates the largest, most scientifically productive telescopes on Earth. The two, 10-meter optical/infrared telescopes on the summit of Mauna Kea on the Island of Hawaii feature a suite of advanced instruments including imagers, multi-object spectrographs, high-resolution spectrographs, integral-field spectrometer and world-leading laser guide star adaptive optics systems. Keck Observatory is a private 501(c) 3 non-profit organization and a scientific partnership of the California Institute of Technology, the University of California and NASA.

    Today Keck Observatory is supported by both public funding sources and private philanthropy. As a 501(c)3, the organization is managed by the California Association for Research in Astronomy (CARA), whose Board of Directors includes representatives from the California Institute of Technology and the University of California, with liaisons to the board from NASA and the Keck Foundation.
    Keck UCal

    Keck NASA

    Keck Caltech

  • richardmitnick 5:56 pm on March 9, 2016 Permalink | Reply
    Tags: , , Dragonfly telescope array, ,   

    From UC Riverside: “Dark Matter Satellites Trigger Massive Birth of Stars” 

    UC Riverside bloc

    UC Riverside

    March 9, 2016
    Sean Nealon

    Dwarf Galaxies with Messier 101  Allison Merritt  Dragonfly Telephoto Array
    Dwarf Galaxies with Messier 101 Allison Merritt Dragonfly Telephoto Array

    U Toronto Dunlap Dragonfly telescope Array
    U Toronto Dunlap Dragonfly telescope Array

    One of the main predictions of the current model of the creation of structures in the universe, known at the Lambda Cold Dark Matter model, is that galaxies are embedded in very extended and massive halos of dark matter that are surrounded by many thousands of smaller sub-halos also made from dark matter.

    Around large galaxies, such as the Milky Way, these dark matter sub-halos are large enough to host enough gas and dust to form small galaxies on their own, and some of these galactic companions, known as satellite galaxies, can be observed. These satellite galaxies can orbit for billions of years around their host before a potential merger. Mergers cause the central galaxy to add large amount of gas and stars, triggering violent episodes of new star formation −known as starbursts− due to the excess gas brought in by the companion. The host’s shape or morphology can also be disturbed due to the gravitational interaction.

    Smaller halos form dwarf galaxies, which at the same time will be orbited by even smaller satellite sub-halos of dark matter which are now far too tiny to have gas or stars in them. These dark satellites therefore are invisible to telescopes, but readily appear in theoretical models run in computer simulations. A direct observation of their interaction with their host galaxies is required to prove their existence.

    Laura Sales, an assistant professor at the University of California, Riverside’s Department of Physics and Astronomy, collaborated with Tjitske Starkenburg and Amina Helmi, both of the Kapteyn Astronomical Institute in The Netherlands, to present a novel analysis of computer simulations, based on theoretical models, that study the interaction of a dwarf galaxy with a dark satellite.

    The findings were outlined in a just-published paper, Dark influences II: gas and star formation in minor mergers of dwarf galaxies with dark satellites, in the journal Astronomy & Astrophysics.

    The researchers found that during a dark satellite’s closest approach to a dwarf galaxy, through gravity it compresses the gas in the dwarf, triggering significant episodes of starbursts. These star forming episodes may last for several billions of years, depending on the mass, orbit and concentration of the dark satellite.

    This scenario predicts that many of the dwarf galaxies that we readily observe today should be forming stars at a higher rate than expected —or should be experiencing a starburst— which is exactly what telescope observations have found.

    Furthermore, similarly to mergers between more massive galaxies, the interaction between the dwarf galaxy and the dark satellite triggers morphological disturbances in the dwarf, which can completely change its structure from mainly disk-shaped to a spherical/elliptical system. This mechanism also offers an explanation to the origin of isolated spheroidal dwarf galaxies, a puzzle that has remained unsolved for several decades.

    See the full article here .

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    UC Riverside Campus

    The University of California, Riverside is one of 10 universities within the prestigious University of California system, and the only UC located in Inland Southern California.

    Widely recognized as one of the most ethnically diverse research universities in the nation, UCR’s current enrollment is more than 21,000 students, with a goal of 25,000 students by 2020. The campus is in the midst of a tremendous growth spurt with new and remodeled facilities coming on-line on a regular basis.

    We are located approximately 50 miles east of downtown Los Angeles. UCR is also within easy driving distance of dozens of major cultural and recreational sites, as well as desert, mountain and coastal destinations.

  • richardmitnick 1:03 pm on July 11, 2014 Permalink | Reply
    Tags: , , , , Dragonfly telescope array,   

    From ScienceDaily: “Hi-ho! Astronomers discover seven dwarf galaxies with new telescope” 

    ScienceDaily Icon


    Date: July 10, 2014
    Source: Yale University. The original article was written by Jim Shelton

    Meet the seven new dwarf galaxies.

    Yale University astronomers, using a new type of telescope made by stitching together telephoto lenses, recently discovered seven celestial surprises while probing a nearby spiral galaxy. The previously unseen galaxies may yield important insights into dark matter and galaxy evolution, while possibly signaling the discovery of a new class of objects in space.

    For now, scientists know they have found a septuplet of new galaxies that were previously overlooked because of their diffuse nature: The ghostly galaxies emerged from the night sky as the team obtained the first observations from the “homemade” telescope.

    This image shows the field of view from the Dragonfly Telephoto Array, centered on M101. Inset images highlight the seven newly discovered galaxies.
    Credit: Image courtesy of Yale University

    The discovery came quickly, in a relatively small section of sky. “We got an exciting result in our first images,” said Allison Merritt, a Yale graduate student and lead author of a paper about the discovery in The Astrophysical Journal Letters. “It was very exciting. It speaks to the quality of the telescope.”

    Pieter van Dokkum, chair of Yale’s astronomy department, designed the robotic telescope with University of Toronto astronomer Roberto Abraham. Their Dragonfly Telephoto Array uses eight telephoto lenses with special coatings that suppress internally scattered light. This makes the telescope uniquely adept at detecting the very diffuse, low surface brightness of the newly discovered galaxies.

    “These are the same kind of lenses that are used in sporting events like the World Cup. We decided to point them upward instead,” van Dokkum said. He and Abraham built the compact, oven-sized telescope in 2012 at New Mexico Skies, an observatory in Mayhill, N.M. The telescope was named Dragonfly because the lenses resemble the compound eye of an insect.

    Dragonfly telescope Array
    Dragonfly Telescope Array

    “We knew there was a whole set of science questions that could be answered if we could see diffuse objects in the sky,” van Dokkum said. In addition to discovering new galaxies, the team is looking for debris from long-ago galaxy collisions.

    “It’s a new domain. We’re exploring a region of parameter space that had not been explored before,” van Dokkum said.

    The Yale scientists will tackle a key question next: Are these seven newly found objects dwarf galaxies orbiting around the M101 spiral galaxy, or are they located much closer or farther away, and just by chance are visible in the same direction as M101?

    If it’s the latter, Merritt said, these objects represent something entirely different. “There are predictions from galaxy formation theory about the need for a population of very diffuse, isolated galaxies in the universe,” Merritt said. “It may be that these seven galaxies are the tip of the iceberg, and there are thousands of them in the sky that we haven’t detected yet.”

    Merritt stressed that until they collect more data and determine the distances to the objects, researchers won’t know their true nature. But the possibilities are intriguing enough that the team has been granted the opportunity to use the Hubble Space Telescope for further study.

    “I’m confident that some of them will turn out to be a new class of objects,” van Dokkum said. “I’d be surprised if all seven of them are satellites of M101.”

    Meanwhile, there is also more work to be done with the new telescope. “We are collecting new data with the Dragonfly telescope every clear night. We’re all curious to see what other surprises the night sky has in store for us,” Merritt said.

    See the full article here.

    ScienceDaily is one of the Internet’s most popular science news web sites. Since starting in 1995, the award-winning site has earned the loyalty of students, researchers, healthcare professionals, government agencies, educators and the general public around the world. Now with more than 3 million monthly visitors, ScienceDaily generates nearly 15 million page views a month and is steadily growing in its global audience.

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