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  • richardmitnick 11:31 am on August 20, 2015 Permalink | Reply
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    From Symmetry: Q&A: Marcelle Soares-Santos 


    August 20, 2015
    Leah Hesla

    Scientist Marcelle Soares-Santos talks about Brazil, neutron stars and a love of discovery.

    Photo by Reidar Hahn, Fermilab

    Marcelle Soares-Santos has been exploring the cosmos since she was an undergraduate at the Federal University of Espirito Santo in southeast Brazil. She received her PhD from the University of São Paulo and is currently an astrophysicist on the Dark Energy Survey based at Fermi National Accelerator Laboratory outside Chicago.

    Soares-Santos has worked at Fermilab for only five years, but she has already made a significant impact: In 2014, she was bestowed the Alvin Tollestrup Award for postdoctoral research. Now she is embarking on a new study to measure gravitational waves from neutron star collisions.

    S: You recently attended the LISHEP conference, a high-energy physics conference held annually in Brazil. This year it was held in the region of Manaus, near your childhood home. What was it like to grow up there?

    MS: Manaus is very different from the region that I think most foreigners know, Rio or São Paulo, but it’s very beautiful, very interesting. When I was four, my father worked for a mining company, and they found a huge reserve of iron ore in the middle of the Amazon forest. All over Brazil, people got offers from that company to get some extra benefits, which was very good for us because one of the benefits was a chance to go a good school there.

    S: When did you get interested in physics?

    MS: That was very early on, when I was a little kid. I didn’t know that it was physics I wanted to do, but I knew I wanted to do science. I tend to say that I lacked any other talents. I could not play any sport, I wasn’t good in the arts. But math and science, that was something I was good at.

    These days I look back and feel that, had I known what I know today, I might not have had this confidence, because I understand now how lots of people are not encouraged to view physics as a topic they can handle. But back then I had a little bit of blind faith in the school system.

    S: You work on the Dark Energy Survey. When did the interest in astrophysics kick in?

    MS: I did an undergraduate research project. In Brazil, there is a program of research initiation where undergraduates can work for an entire year on a particular topic. My supervisor’s research was related to dark energy and gravitational waves. It’s interesting, because today I work on those two topics from a completely different perspective.

    Dark Energy Icon
    Dark Energy Camera
    Dark Energy camera (DECam) built at FNAL and housed in the CTIO Victor M Blanco 4 meter telescope in Chile
    CTIO Victor M Blanco 4m Telescope
    CTIO Victor M Blanco 4m Telescope interior
    CTIO Victor M Blanco telescope

    S: You’re also starting on a new project to study gravitational waves. What’s that about?

    MS: For the first time we are building detectors that will be able to detect gravitational waves, not from cosmological sources, but from colliding neutron stars. These events are very rare, but we know they occur, and we can calculate how much gravitational wave emission there will be. The detectors are now reaching the sensitivity that they can see that. There’s LIGO in the United States and Virgo collaboration in Europe.

    Caltech LIGO
    LIGOVIRGO interferometer EGO Campus

    Relying solely on gravitational waves, it’s possible only to roughly localize in the sky where the star collision happens. But we also have the Dark Energy Camera, so we can use it to find the optical counterpart—lots and lots of photons—and pinpoint the event picked up by the gravitational wave detector.

    If we see the collision, we will be the first ones to see it based on a gravitational wave signal. That will be really cool.

    S: How did the project get started? What is it called?

    MS: I saw an announcement that LIGO was going to start operating this year, and I thought, “DECam would be great for this.” I talked to Jim Annis [at Fermilab] and said, “Look, look at this. It would be cool.” And he said, “Yeah, it would.”

    It’s called the DES-GW project. It will start up in September. Groups from Fermilab, the University of Chicago, University of Pennsylvania and Harvard are participating.

    S: What’s your favorite thing about what you do?

    MS: Building these crazy ideas to become a reality. That’s the fun part of it. Of course, it’s not always possible, and we have more ideas than we can actually realize, but if you get to do one, it’s really cool. Part of the reason I moved from theory [as a graduate student] to experiment is that I wanted to do something where you actually get to close the loop of answering a question.

    S: Has anything about being a scientist surprised you?

    MS: In the beginning I thought I’d never be the person doing hands-on work on detector. I thought of myself more as someone who would be sitting in front of a computer. And it’s true that I spend most of my time sitting in front of the computer, but I also get a chance to go to Chile [where the Dark Energy Camera is located] and take data, be at the lab and get my hands dirty. Back then I thought that was more the role of an engineer than a scientist. I learned it doesn’t matter the label. It is a part of the job, and it’s a fun part.

    S:In June 2014 Fermilab posted a Facebook post about you winning the Alvin Tollestrup Award. It received by far more likes than any Fermilab post up to that point, and most were pouring in from Brazil. What was behind its popularity?

    MS:That was surprising for me. Typically whenever there is something on Facebook related to what I do, my parents will be excited about it and repost, so I get a few likes and reposts from relatives and friends. This one, I don’t know what happened. I think in part there was a little bit of pride, people seeing a Brazilian being successful abroad.

    I got lots of friend requests from people I’ve never met before. I got questions from high schoolers about physics and how to pursue a physics education. It’s a big responsibility to say something. What do you say to people? I tried to answer reasonably and tell them my experience. It was my 15 minutes of fame in social media.

    See the full article here.

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    Symmetry is a joint Fermilab/SLAC publication.

  • richardmitnick 12:33 pm on June 4, 2015 Permalink | Reply
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    From Symmetry: “The universe at your fingertips” 


    June 04, 2015
    Manuel Gnida

    Courtesy of DECam Legacy Survey

    Raw images from the DECam Legacy Survey’s new image archive will appear online the day after they are taken.

    When it was time to celebrate the 20th anniversary of the Star Wars trilogy, director George Lucas was prompted by technological leaps in the filmmaking industry to produce a digitally remastered special edition.

    Today scientists of the DECam Legacy Survey released their own version of a special edition. They published the first in a series of catalogs that offer an update to images of the night sky originally taken with the 15-year-old camera of the Sloan Digital Sky Survey [SDSS].

    SDSS Telescope
    SDSS telescope at Apache Point, NM, USA

    In the spirit of the new information age, the survey will share frequent updates on its public website. With its Sky Viewer, users can explore the contents of the universe, whose busyness might surprise anyone accustomed to bland skies polluted by city lights.

    Site visitors can choose whether they want to look at false-color images or theoretical models of the sky, or see the difference between the two. The website also contains a map of dust emissions in the Milky Way based on data first reported in one of the most cited journal articles of all astrophysics.

    Similar exploration tools exist for the image archives of SDSS and the Hubble telescope. However, these data became publicly available only after a period of restricted use by a limited group of researchers.

    “The Legacy Survey is unique in that it doesn’t have any proprietary restrictions,” says David Schlegel of Lawrence Berkeley National Laboratory, who initiated the new project together with Arjun Dey, a staff astronomer at the National Optical Astronomy Observatory. “Raw images will appear the day after they were taken, and we plan on releasing processed versions every three to six months.”

    The Legacy Survey’s image archive will eventually cover one third of the sky. Hopes are that it will serve scientists around the world in a multitude of studies, from explorations of the structure of our Milky Way galaxy to analyses of our universe’s mysterious dark energy that accelerates the cosmic expansion.

    Today’s data release is the outcome of the survey’s first observations with the 520-megapixel Dark Energy Camera, or DECam, which is mounted on the Blanco telescope in Chile.

    Dark Energy Camera
    DECam, built at FNAL

    CTIO Victor M Blanco 4m Telescope
    CTIO Victor M Blanco 4m Telescope interior
    CTIO Victor M Blanco 4 meter telescope in Chile

    Additional snapshots will be also taken with cameras of the Bok and Mayall telescopes in Arizona. The experiments began last fall and will take place on a total of over 500 nights spread out over three years.

    Bok Telescope U Arizona Stewrad Observatory
    U Arizona Steward Observatory Bok Telescope

    NOAO Mayall 4 m telescope exterior
    NOAO Mayall Telescope

    Processing mixed-quality data from three different telescopes collected under varying observation conditions will be a big challenge for the scientists.

    “Given the large area of the sky we want to cover and the limited experimental time we have been assigned, we can only take three images of each part of the sky,” says Legacy Survey member Dustin Lang of Carnegie Mellon University, who developed new image processing techniques that describe the observations with theoretical models. “We need to make the most of our data, no matter whether the observation conditions are good or bad on a given night.”

    Researchers want to link the images of stars, galaxies and other cosmic objects to complementary information they collect with spectroscopy, the analysis of light emissions. This includes, for instance, redshifts that measure how fast objects are moving relative to us, information crucial for dark energy studies.

    After three years are up, the Legacy Survey should live up to its name. The information it gathers will live on as a guide for a new surveyor, the Dark Energy Spectroscopic Instrument, whose redshift measurements will chart the expansion history of the universe over the last 10 billion years of cosmic time.

    See the full article here.

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    Symmetry is a joint Fermilab/SLAC publication.

  • richardmitnick 1:05 pm on April 30, 2015 Permalink | Reply
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    From Symmetry: “DECam’s far-out forays” 


    April 30, 2015
    Liz Kruesi

    Photo by Reidar Hahn, Fermilab

    The Dark Energy Camera does even more than its name would lead you to believe.

    The Dark Energy Survey, which studies the accelerating expansion of our universe, uses one of the most sensitive observing tools that astronomers have: the Dark Energy Camera.

    Built at Fermi National Accelerator Laboratory and situated on the Victor Blanco 4-meter telescope in Chile, the camera spends 30 percent of each year collecting light from clusters of galaxies for DES.

    CTIO Victor M Blanco 4m Telescope
    CTIO Victor M Blanco 4m Telescope interior
    CTIO Victor Blanco 4-meter telescope

    Another chunk of time goes to engineering and upgrades. The remaining one-third is split up among dozens of other observing projects.

    A recent symmetry article looked at some of those projects—the ones that are studying objects within our solar system. In this follow-up, we give a sampling of how DECam has been used to reach even farther into the universe.

    Studying stellar oddballs

    The sun is a “normal” star, humming along, fusing hydrogen to helium in its core. Most of the stars in the universe produce energy this way. But the cosmos contains a whole collection of stranger stellar objects, such as white dwarfs, brown dwarfs and neutron stars. They also include exploding stars called supernovae. Ten projects use the DECam to study these stellar varieties.

    Armin Rest, an astronomer at the Space Telescope Science Institute in Baltimore, Maryland, leads two of those projects. In the past two years, he has spent 28 nights at the Blanco Telescope looking for supernovae.

    In both projects, Rest looks for light released during stellar explosions that has bounced off dust clouds on its way to our night sky. These “light echoes” preserve information about the blasts that caused them—for example, what type of star exploded and how it exploded.

    “It is as if we have a time machine with which we can travel back in time and take a spectrum with modern instrumentation of an event that was seen on Earth hundreds of years ago,” Rest says.

    DECam’s expertise in taking fast pictures of big areas makes this search much more efficient than it would be with other instruments, Rest says.

    Following streams of stars

    Astronomers have found many streams of stars winding tens of degrees across our sky. These streams are the telltale signs of galaxies interacting with one another. The gravity of one galaxy can rip the stars out of another.

    Yale University’s Ana Bonaca is working on a project that uses DECam to map the stars in one such stream. It extends from Palomar 5, a conglomeration of thousands of stars at the outskirts of our galaxy. Palomar 5 is one of the lowest-mass objects being torn apart by the Milky Way, “which means that its streams are very narrow and preserve a better record of past interactions,” Bonaca says.

    Palomar 5

    Scientists are hoping to tease out of these observations information about dark matter, which accounts for some 80 to 90 percent of our galaxy’s mass.

    Scientists expect that in a narrow stellar stream, clumps of dark matter will create density variations. If you can map the density variations in such a stream, you can learn how the dark matter is distributed. This is where DECam’s strength comes in: The sensitive instrument collects light from deep imaging across large fields speckled with long, narrow stellar streams.

    Ten other projects are using the instrument for similar research.

    Bonaca and colleagues expect to publish their findings later this year. “Our preliminary maps of the Palomar 5 stream show tantalizing evidence for density variations along the stream,” she says.

    Digging for galaxies

    Our galaxy is just one of at least 100 billion galaxies in the universe. Those other galaxies are the focus of eight projects using the Dark Energy Camera.

    The DECam Legacy Survey, for one, is currently imaging all of the galaxies in 6700 square degrees of sky. The plan, says David Schlegel of the Lawrence Berkeley National Laboratory, is to combine the information gathered from DECam and two telescopes located at Arizona’s Kitt Peak National Observatory with the images, spectral data and distance measurements collected via the long-running Sloan Digital Sky Survey.

    “The combination of the Legacy Survey imaging plus SDSS spectroscopy will be used for studying the evolution of galaxies, the halo of our Milky Way and other things we’ve likely not thought of yet,” Schlegel says.

    SDSS Telescope
    SDSS Telescope at Apache Moint, NM, USA

    The other goal of the survey is to identify some 30 million targets to study with the Dark Energy Spectroscopic Instrument [DESI}, a recently approved instrument that will be installed on the Mayall 4-meter telescope at Kitt Peak.

    NOAO Mayall 4 m telescope exterior
    NOAO Mayall 4 m telescope interior
    Mayall 4-meter telescope

    Dark Energy Spectroscopic Instrument

    Members of the Legacy Survey team have been releasing their observations nearly immediately to other researchers and the public. They have much more observing time ahead of them: In total, the project was awarded 65 nights on the Blanco telescope and DECam. So far they’ve used only 22.

    Weighing the clusters

    Most of the galaxies in our universe are gathered in groups and clusters, drawn together by the gravity of the clumps of dark matter in which they formed. Scientists are using DECam to study how matter (including dark matter) is distributed within clusters holding hundreds to thousands of galaxies.

    When you observe a galaxy cluster, you also collect light from objects that lie behind that cluster. In the same way an old, imperfect window warps the light from a streetlamp, a cluster’s galaxies, gas, and dark matter shear and stretch any background light that passes through. Astronomers analyze this bending of light from background galaxies, an effect called “gravitational lensing,” to map the mass distribution of a galaxy cluster and even measure its total mass.

    Seven projects use the DECam for such studies. Ian Dell’Antonio of Brown University leads one of them. He and colleagues study the 10 largest galaxy clusters that fit within the DECam field of view; all of them are between about 500 million and 1.4 billion light-years from Earth.

    The researchers are about halfway through their dozen observing nights. They have so far differentiated between gravitational lensing by galaxy cluster Abell 3128 and gravitational lensing by another background cluster. They estimate the mass of Abell 3128 is about 1000 trillion times the mass of our sun, and they have identified several clumps of dark matter, Dell’Antonio says.

    The Dark Energy Camera’s large field of view is crucial to this research, but so is the camera’s design, Dell’Antonio says. “DECam was designed to have an unusually uniform focus across the field of view and with special detectors to keep the camera in focus throughout the night. Put all these things together, and you’ve got an excellent camera for gravitational lensing studies.”

    And, it seems, for just about any other type of astronomical imaging scientists can think of.

    See the full article here.

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    Symmetry is a joint Fermilab/SLAC publication.

  • richardmitnick 2:08 pm on January 22, 2015 Permalink | Reply
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    From Symmetry: “DECam’s nearby discoveries” 


    January 22, 2015
    Liz Kruesi

    The Dark Energy Camera does more than its name would lead you to believe.

    DECam, built at FNAL

    CTIO Victor M Blanco 4m Telescope
    CTIO Victor M Blanco 4m Telescope interior
    CTIO Victor M Blanco 4m Telescope which houses the DECam

    The Dark Energy Camera, or DECam, peers deep into space from its mount on the 4-meter Victor Blanco Telescope high in the Chilean Andes.

    Thirty percent of the camera’s observing time—about 105 nights per year—go to the team that built it: scientists working on the Dark Energy Survey.

    Another small percentage of the year is spent on maintenance and upgrades to the telescope. So who else gets to use DECam? Dozens of other projects share its remaining time.

    Many of them study objects far across the cosmos, but five of them investigate ones closer to home.

    Overall, these five groups take up just 20 percent of the available time, but they’ve already taught us some interesting things about our planetary neighborhood and promise to tell us more in the future.

    Far-out asteroids

    Stony Brook University’s Aren Heinze and the University of Western Ontario’s Stanimir Metchev used DECam for four nights in early 2014 to search for unknown members of our solar system’s main asteroid belt, which sits between Mars and Jupiter.

    To detect such faint objects, one needs to take a long exposure. However, the paths of these asteroids lie close enough to Earth that taking an exposure longer than a few minutes results in blurred images. Heinze and Metchev’s fix was to stack more than 100 images taken in less than two minutes each.

    With this method, the team expects to measure the positions, motions and brightnesses of hundreds of main belt asteroids not seen before. They plan to release their survey results in late 2015, and an early partial analysis indicates they’ve already found hundreds of asteroids in a region smaller than DECam’s field of view—about 20 times the area of the full moon.
    Whole new worlds

    Scott Sheppard of the Carnegie Institution for Science in Washington DC and Chad Trujillo of Gemini Observatory in Hilo, Hawaii, use DECam to look for distant denizens of our solar system. The scientists have imaged the sky for two five-night stretches every year since November 2012.

    Every night, the DECam’s sensitive 570-megapixel eye captures images of an area of sky totaling about 200 to 250 times the area of the full moon, returning to each field of view three times. Sheppard and Trujillo run the images from each night through software that tags everything that moves.

    “We have to verify everything by eye,” Sheppard says. So they look through about 60 images a night, or 300 total from a perfect five-night observing run, a process that gives them a few dozen objects to study at Carnegie’s Magellan Telescope.

    The scientists want to find worlds beyond Pluto and its brethren—a region called the Kuiper Belt, which lies some 30 to 50 astronomical units from the sun (compared to the Earth’s 1). On their first observing run, they caught one.

    Kuiper Belt

    This new world, with the catalog name of 2012 VP113, comes as close as 80 astronomical units from the sun and journeys as far as 450. Along with Sedna, a minor planet discovered a decade ago, it is one of just two objects found in what was once thought of as a complete no man’s land.

    The discovery images of 2012 VP113, as made by the Cerro Tololo Inter-American Observatory [read DECam at Blanco]. The image is a merger of three images with three colored dots pinpointing the image of 2012 VP113. The three images were taken 2 hours apart each. The red dot represents 2012 VP113’s location on the first image, the second represents its location on the second image, and the blue dot representing its location on the third.

    Sheppard and Trujillo also have discovered another dwarf planet that is one of the top 10 brightest objects beyond Neptune, a new comet, and an asteroid that occasionally sprouts an unexpected tail of dust.

    Mythical creatures

    Northern Arizona University’s David Trilling and colleagues used the DECam for three nights in 2014 to look for “centaurs”—so called because they have characteristics of both asteroids and comets. Astronomers believe centaurs could be lost Kuiper Belt objects that now lie between Jupiter and Neptune.

    Trilling’s team expects to find about 50 centaurs in a wide range of sizes. Because centaurs are nearer to the sun than Kuiper Belt objects, they are brighter and thus easier to observe. The scientists hope to learn more about the size distribution of Kuiper Belt objects by studying the sizes of centaurs. The group recently completed its observations and plan to report them later in 2015.

    Next-door neighbors

    Lori Allen of the National Optical Astronomy Observatory outside Tucson, Arizona, and her colleagues are looking for objects closer than 1.3 astronomical units from the sun. These near-Earth objects have orbits that can cross Earth’s—creating the potential for collision.

    Allen’s team specializes in some of the least-studied NEOs: ones smaller than 50 meters across.

    Even small NEOs can be destructive, as demonstrated by the February 2013 NEO that exploded above Chelyabinsk, Russia. The space rock was just 20 meters wide, but the shockwave from its blast shattered windows, which caused injuries to more than 1000 people.

    In 2014, Allen’s team used the DECam for 10 nights. They have 20 more nights to use in 2015 and 2016.

    They have yet to release specific findings from the survey’s first year, but the researchers say they have a handle of the distribution of NEOs down to just 10 meters wide. They also expect to discover about 100 NEOs the size of the one that exploded above Chelyabinsk.

    Space waste

    Most surveys looking for “space junk”—inactive satellites, parts of spacecraft and the like in orbit around the Earth—can see only pieces larger than about 20 centimeters. But there’s a lot more material out there.

    How much is a question Patrick Seitzer of the University of Michigan and colleagues hope to answer. They used DECam to hunt for debris smaller than 10 centimeters, or the size of a smartphone, in geosynchronous orbit.

    The astronomers need to capture at least four images of each piece of debris to determine its position, motion and brightness. This can tell them about the risk from small debris to satellites in geosynchronous orbit. Their results are scheduled for release in mid-2015.

    See the full article here.

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    Symmetry is a joint Fermilab/SLAC publication.

  • richardmitnick 10:39 am on October 15, 2014 Permalink | Reply
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    From FNAL: “From the Center for Particle Astrophysics – Big eyes” 

    Fermilab is an enduring source of strength for the US contribution to scientific research world wide.

    Wednesday, Oct. 15, 2014

    Craig Hogan, head of the Center for Particle Astrophysics, wrote this column.

    To create small things you need particles with lots of energy, and to learn about them you need to capture and study lots of particles. So it is not surprising that the worldwide physics community is in the business of building giant accelerators and detectors..

    We also find out about new physics without using accelerators by studying the biggest system of all — the cosmos. Such experiments also need big detectors, in particular, giant cameras to make deep, wide-field maps of cosmic structure. For example, Fermilab’s Dark Energy Camera (DECam) is now collecting data for the Dark Energy Survey, using light from distant galaxies gathered by the 4-meter Blanco telescope on Cerro Tololo in Chile. Designed for depth, speed, sensitivity and scientific precision, it’s a behemoth compared to the camera in your phone. By the time you add up all the parts — the detectors, the lenses, the cooling systems, the electronics and the structure to hold them precisely in place 50 feet up in the telescope beam — you have a machine that weighs about 10 tons. That may not seem very big compared to the Tevatron or the thousand-ton telescope the camera is mounted on, but it’s a lot for a digital camera — the biggest ever built.

    CTIO Victor M Blanco 4m Telescope
    CTIO Victor M Blanco 4m Telescope interior
    CTIO Victor M Blanco 4 meter telescope



    The giant telescope simulator used to test DECam has recently been removed from the Fermilab building where the camera was put together. In the same space, another giant camera will soon start to take shape. This one will study the cosmic microwave background — the primordial light from the big bang. That light has been cooled by the cosmic expansion to microwave wavelengths, so the camera detectors and even its lenses must be cold to match. About 15,000 advanced superconducting detectors from Argonne National Laboratory will be integrated into a camera system about as big as DECam and then shipped for an experiment to take place under the thin, cold, crystalline skies at the South Pole.

    Cosmic Background Radiation Planck
    CMB from ESA/Planck

    ESA Planck
    ESA Planck schematic

    This machine — the SPT-3G camera — will also be the largest of its kind ever built. When it is finished, it will be installed on the South Pole Telescope, where it will map the faint ripples of polarization imprinted on the light since it was created almost 14 billion years ago.

    South Pole Telescope
    South Pole Telescope

    The SPT-3G experiment will advance cosmic mapping by an order of magnitude, but it is also a stepping stone along a path to an even larger Stage 4 CMB project in the following decade. That project, endorsed by the P5 report and supported by a nationwide collaboration of labs and university groups now forming, will carry out a comprehensive survey of the primordial radiation over much of the sky and teach us about new physics ranging from neutrino masses to dark energy.

    See the full article here.

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  • richardmitnick 9:23 am on July 10, 2014 Permalink | Reply
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    From Fermilab- “The sky is not the limit: DES gets time on Gemini telescope” 

    Fermilab is an enduring source of strength for the US contribution to scientific research world wide.

    Thursday, July 10, 2014
    Hanae Armitage

    In an ambitious five-year mission, the Dark Energy Survey team has devoted itself to mapping the southern sky in unprecedented detail, ultimately hoping to decipher what may stand as the most bewildering phenomenon of our expanding universe.

    In March, DES applied to the Large and Long Program at the Gemini Observatory, a program meant to foster scientific exploration through global collaboration. Although the Gemini Observatory has existed since 2000, the Large and Long Program launched just last year as another means to probe the shrapnel of the big bang. It offers time on two of the world’s finest telescopes, one located atop an 8,900-foot mountain in the Chilean Andes (Gemini South) and the other on Mauna Kea, Hawaii (Gemini North).

    Gemini North telescope
    Gemini North

    Gemini South telescope
    Gemini South

    Just last month, co-leader of the Strong Lensing Science Working Group at DES, Liz Buckley-Geer, received the email she’d been waiting for: Spread over the next three years, DES had been awarded a lofty total of 276 hours on Gemini South.

    “Because we were asking for such a big block of time I really didn’t think we had much of a chance,” Buckley-Geer said. “I was pretty gobsmacked when I got the email two weeks ago.”

    With a hefty 8.1-meter mirror, the Gemini telescope is twice as large as the telescope on which DECam is currently mounted. But DES scientists don’t plan to take new images with Gemini South. DECam images are plenty clear and show high-quality snapshots of galaxies and galaxy clusters. Instead of imaging, DES scientists will use an instrument called a spectrograph to further inspect the images and, in some cases, confirm a rare phenomenon called strong lensing.


    One of five methods DES uses to explore dark energy, strong lensing is the bending of light from a distant galaxy, or source, due to the gravitational influence of a massive foreground object, or lens. Lensing changes the observed shape of the distant galaxy and intensifies brightness. To find these strong lensing systems in the DECam images, DES scientists look for objects that look distorted, often appearing as long bright arcs, multiple blue knots or, in the rarest cases, an Einstein ring. DES will focus on certain classes of strong lenses that can be used to study dark energy.

    “The strong lenses provide a kind of peephole to the more distant, fainter universe that wouldn’t be available if the lenses weren’t there,” said DES Operations Scientist Tom Diehl.

    But what appear to be strong lenses are not always so. To separate the lenses from the impostors, scientists measure the redshifts of both the lens and the source. A true strong lens is one in which the source redshift is larger than the lens redshift.

    A redshift occurs when light wavelengths increase, or shift toward the red side of the electromagnetic spectrum. The measured redshift of a galaxy is related to the expansion of the universe as a function of time, and it allows DES scientists to calculate the distance to the object.

    To determine the redshift of a galaxy, the scientists will compare the spectrum of the obtained light with known features in the spectrum of various chemical compounds found on Earth. If the same features are seen in an observed spectrum from a distant source but occur at shifted wavelengths, then the redshift can be calculated.

    “The observations with Gemini will give us the redshifts of all these objects, and armed with that information we can move on to the next step,” Buckley-Geer said. “It’s not all the information we need, but it’s one piece of the jigsaw puzzle closer to understanding these system in relation to dark energy.”

    See the full article here.

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  • richardmitnick 1:30 pm on May 30, 2014 Permalink | Reply
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    From Fermilab- “Frontier Science Result: DES The Dark Energy Survey looks at massive galaxy clusters – and finds filaments” 

    Fermilab is an enduring source of strength for the US contribution to scientific research world wide.

    Friday, May 30, 2014
    Peter Melchior, Ohio State University

    Galaxy clusters — accumulations of hundreds of galaxies — are said to be the largest gravitationally bound structures in the universe. While this statement is correct as such, it easily conveys an incorrect picture: that of clusters as static, isolated spheres that have swallowed every galaxy within reach at some time in the cosmic past. Nothing could be further from reality.

    Galaxy clusters are not isolated but dynamic environments that actively accrete material from their surroundings. The preferred mode of accretion proceeds along so-called filaments, the connecting links between the central hubs of the cosmic web. The existence of filaments is a prediction of the cold dark matter model we use to describe the formation of structures in the universe, revealed in large cosmological simulations and spectroscopic surveys.

    The new Dark Energy Camera was built by the 300-member Dark Energy Survey (DES) collaboration to carry out a five-year survey to probe the origin of cosmic acceleration. The camera is mounted on the Blanco 4-meter telescope at the Cerro Tololo Inter-American Observatory in Chile and saw first light in September 2012.

    Dark Energy Camera

    NOAO 4m Blanco telescope
    NOAO 4m Blanco Telescope at Cerro Tololo

    Shortly after the camera was commissioned, we proposed a program to target several massive galaxy clusters as part of a process called science verification, a rigorous test of the new instrument. The prospects for this project were mixed. After the overhaul of the telescope control system and with the new camera, nobody could guarantee that the images we were going to obtain would have the necessary quality for accurate studies of these clusters. But if it worked, we could exploit DECam’s massive field of view of more than 3 square degrees (roughly 15 times the area of the full moon) to study not only the clusters themselves, but also the environments from which they accrete.

    It worked. Over the course of 18 months, I led a team that ultimately involved more than 90 DES scientists from 37 institutions worldwide. In our recently submitted paper, the first based upon DES data, we demonstrated that the new camera and revamped telescope worked together as expected. This data and our careful analysis allowed us to determine the distributions of so-called red-sequence galaxies, whose red color is a reliable tracer of the dynamical processes in clusters. Furthermore, we exploited an effect called gravitational lensing to infer the mass distributions of these clusters, an analysis with exceptionally stringent requirements on image quality.

    Everything lines up. The visible orientation of the brightest cluster galaxies sitting at the cluster centers; the mass distribution tracing hundreds of cluster galaxies (shown in the image below); the large-scale distribution of red-sequence galaxies far beyond the gravitational reach of the actual clusters: All these probes show that clusters are indeed interwoven with the cosmic web, the structure of which DES will reveal in unprecedented detail.

    See the full article here.

    Fermilab Campus

    Fermi National Accelerator Laboratory (Fermilab), located just outside Batavia, Illinois, near Chicago, is a US Department of Energy national laboratory specializing in high-energy particle physics.

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  • richardmitnick 1:10 pm on May 5, 2014 Permalink | Reply
    Tags: , , , , DECam, DESI,   

    From Symmetry: “Scientists to map universe in 3-D HD” 


    May 05, 2014
    Fermilab Leah Hesla
    This article was writen by Leah Hesla

    The Dark Energy Spectroscopic Instrument will create the clearest three-dimensional map yet of one-third of the sky.

    DESI Dark Energy Spectroscopic Instrument

    Maps do more than tell us where we are. Rich with information elegantly arranged, they give us a way to assimilate our vast world. The clearer the map, the more confidently we set out to explore, looking for something it doesn’t show.

    In a few years, scientists will come out with a new map of a third of the sky, one that will go deeper and bring that depth into sharper focus than any survey has yet achieved. It will pinpoint in three dimensions the locations of 25 million galaxies and quasars, pulling back the curtains on the history of the universe’s expansion over more than half of the age of the universe.

    Armed with this detailed picture, scientists will be better equipped to search for something the map can’t show but whose effects will likely be all over it—dark energy. The researchers’ cartographic tool will be the Dark Energy Spectroscopic Instrument, or DESI.

    “We have very precise measurements of positions and shapes of galaxies and galaxy clusters in the lateral dimensions, but the resolution in the distance away from us is much worse,” says Fermilab’s Brenna Flaugher, one of the leading scientists on DESI. “With DESI, you get the really fine measurements in depth. Your map of the universe suddenly gets clearer.”

    The DESI project, managed at Lawrence Berkeley National Laboratory, is one of a number of surveys looking to get a handle on how dark energy operates.

    “We’re going to try to understand what dark energy is,” says Berkeley Lab’s Michael Levi, DESI project director. “We don’t know if it’s something having to do with gravity that we don’t understand or some new form of energy that we just haven’t gotten our heads around yet.”

    Whatever it is, it leaves its trace in the growth and structure of the universe.

    DESI will model the universe’s expansion using two approaches. One is to precisely measure the spectra of the light coming from galaxies to determine their distance from us. The redder the light is, the farther away the galaxy.

    The other approach is to measure the distances between galaxies. Galaxies arose from areas left dense with matter when the universe cooled down from the rapid expansion of the Big Bang. These peaks in density are known as baryon acoustic oscillations. Back when the peaks formed, they corresponded to a separation of about 490 million light-years. Since then the expansion of the universe has stretched them apart. Comparing the standard ruler against the distances between galaxies as the universe developed to its current state, scientists will be able to measure how space has stretched since the early times.

    Together, the measurements will tell scientists how and how fast the universe is growing.

    “Being able to make those two measurements at the same time—one about the expansion rate of the universe and the other about how structure is growing—allows you to test the theory of general relativity on this huge length and time scale,” says SLAC National Accelerator Laboratory’s Risa Wechsler, DESI co-spokesperson.

    DESI will be the first survey to make measurements accurate to less than 1 percent of the expansion rate of the universe over the last 11 billion years.

    The Dark Energy Spectrographic Instrument is designed to attach to the Mayall 4-Meter Telescope (2 pictures below) in Arizona. Once construction is completed, it will have 5000 fibers for collecting the spectra of galaxy light.

    NOAO Mayall 4 m telescope exterior
    NOAO/Mayall 4m telescope exterior

    NOAO Mayall 4 m telescope interior
    NOAO/Mayall 4m telescope interior

    Using data from the Dark Energy Camera in Chile, which is currently focused on taking imaging data for the Dark Energy Survey, DESI will point each of those 5000 fibers at a galaxy. Once the fibers get what they need, they will move on to the next set of 5000 celestial objects.
    Dark Energy Camera

    “It’s like a big pincushion that wiggles at every image,” Flaugher says. “Every 20 minutes you take an image, and then you reposition each of these little fibers onto new targets.” It will keep doing that until it hits 25 million galaxies.

    DESI grew out of two separate proposals to develop a spectroscopic instrument to explore dark energy. The DESI collaboration is made of 180 scientists from 45 institutions around the world, including five DOE laboratories.

    Scientists expect to finish DESI’s construction in 2018. The experiment will then run for five years.

    “The other cosmic surveys that are going on now and over the next 10 years—the Dark Energy Survey, LSST—are spectacular, and they’ll take images of a lot more galaxies than DESI will measure, but they’re making a 2- or 2.5-dimensional measurement of the universe.” Wechsler says.

    “DESI is really making a 3-D map. You get a lot of additional power because you can say what the universe looks like in three dimensions over this long history.”

    See the full article here.

    Symmetry is a joint Fermilab/SLAC publication.

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  • richardmitnick 1:14 pm on February 25, 2014 Permalink | Reply
    Tags: , , , , , DECam, ,   

    From Fermilab: “To catch a falling asteroid: Dark Energy Camera scientists locate object passing Earth” 

    Fermilab is an enduring source of strength for the US contribution to scientific research world wide.

    Tuesday, Feb. 25, 2014
    Leah Hesla

    For seven minutes earlier this month, two Fermilab physicists moonlighted as astronomers who, like the Men in Black, were positioned to protect the Earth from the scum of the universe.

    On Feb. 3, Alex Drlica-Wagner and Steve Kent were in Chile taking data for the Dark Energy Survey when they received an email stating that a satellite telescope had picked up signs of a potentially hazardous asteroid, one whose orbit might soon meet with Earth’s.

    This Dark Energy Survey observing team was on shift at the Dark Energy Camera in Chile when they got the call to check out a potentially hazardous asteroid. From left: Steve Kent (Fermilab and University of Chicago), Alex Drlica-Wagner (Fermilab) and Hernan Tirado, telescope operator at the Cerro-Tololo Inter-American Observatory, where DECam is housed. Photo: Sara Barber, University of Oklahoma

    The message had come from a scientist at the Jet Propulsion Laboratory. Bad weather in the northern hemisphere had foiled attempts by JPL’s two go-to cameras to photograph the asteroid, hindering the lab’s ability to predict its orbit. Could the Dark Energy Camera take a bit of time off from its usual task of imaging distant galaxies to take pictures of this near-Earth object?


    “We know about thousands of these asteroids,” said Kent, SCD. “Of course, one we didn’t know about hit Russia last year, so there’s a lot of interest.”

    Since the asteroid was new on the orbital block, astronomers had only a rough idea of where it was headed. They did know it would soon pass in line with the sun and thus be difficult to spot in photographs.

    “If we didn’t follow up on it within two days, they weren’t going to be able to follow it up anytime soon,” said Drlica-Wagner of Fermilab’s Center for Particle Astrophysics. “Because of the weather and the uncertainty of the predictions, DECam was the only thing that could pull it off.”

    Given Chile’s clear skies and DECam’s large field of view, Drlica-Wagner and Kent were fairly confident they could catch the asteroid on camera in five takes, even if its predicted location was only an estimate. They punched in the coordinates JPL gave them and took their shots. Seven minutes later, they had photos.

    The asteroid turned up in all five, though it wasn’t immediately apparent. The images had to be processed by the National Optical Astronomy Observatory in Tucson, Ariz., and coordinates submitted to the Minor Planet Center in Cambridge, Mass., to figure out the orbit. The results were then sent to JPL.

    The asteroid looked just like the faint stars that it shared the photos with, except for one characteristic — it appeared in different positions in the five images, just the way a cartoon dot would move in a flipbook.

    After combining the pictures with the satellite data, the asteroid-tracking crew brought good news.

    “People shouldn’t be particularly worried,” Drlica-Wagner said. At its closest approach to Earth on March 1, newly discovered Apollo-class asteroid 2014 BE63 will be 18 million miles away.

    The Dark Energy Camera scientists were glad to come to the aid of fellow astronomers.

    “In astronomy there are always things that are time-critical in nature. People will say, ‘You’re at the telescope. Can you do something for me?'” Kent said. “It’s a bit of a tradition to help when you can.”

    He added jokingly, “In this case, saving the Earth was an extra factor, so we thought it was generous.”

    See the full article here.

    Fermilab Campus

    Fermi National Accelerator Laboratory (Fermilab), located just outside Batavia, Illinois, near Chicago, is a US Department of Energy national laboratory specializing in high-energy particle physics.

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  • richardmitnick 1:31 pm on January 28, 2014 Permalink | Reply
    Tags: , , , DECam,   

    From Fermilab: “Toward a new dark-energy detector” 

    Fermilab is an enduring source of strength for the US contribution to scientific research world wide.

    Tuesday, Jan. 28, 2014
    Leah Hesla

    The power of the 570-megapixel Dark Energy Camera lies in its ability to capture celestial objects millions of light-years away. Scientists are now working toward developing an instrument for characterizing these stars and galaxies in greater detail.


    Scientist Juan Estrada, PPD, is currently leading a Fermilab team to develop a large instrument using detectors called MKIDs, short for microwave kinetic inductance detectors. In the coming years, they’ll use it to obtain more information about the astronomical objects already detected by the Dark Energy Camera, pointing it into the night sky to capture more information about those objects’ light.

    The team builds on the work of a University of California, Santa Barbara group, led by Ben Mazin, which developed MKIDs for the visible and infrared spectrum.

    “These are small detectors,” Estrada said. “We’d like to convert this technology into something for a large instrument for cosmology.”

    The Dark Energy Camera is outfitted with 74 charge-coupled devices, better known as CCDs, and its optical filters divide the light from far-off galaxies or stars into one of five spectral ranges. When a CCD gets a hit from one of the photons from the split-off light, it sends a small signal saying that the light in that filter’s range of wavelengths has come through. The data from the five filters are then reassembled into a color picture of the galaxy or star, much the way your computer monitor layers red, green and blue pixels to generate full-color images.

    Thus DECam’s filter-and-CCD system gives scientists the rough spectral make-up of an astronomical object.

    A prototype of the Dark Energy Survey camera, DECam. The front ring holds the detecting CCDs and is 45cm in diameter. (Credit: Fermilab)

    An MKID, however, would enhance that five-color rendering many times over. When struck by a visible photon, it produces a flood of so-called quasiparticles, allowing the wavelength for every single photon hitting the MKID to be precisely measured. That, in turn, leads to color images of astronomical objects without the use of optical filters. The higher the photon’s energy — or the more towards the violet end of the spectrum it is — the more particles it produces.

    MKIDs, which use superconducting material, must be very cold to be able to detect photons. In testing the current MKID-based prototype instrument, Estrada’s team recently brought it to a temperature of 33 millikelvin — the lowest temperature ever achieved on site at Fermilab.

    Over the next several years, the team hopes to create an MKID prototype instrument that can be installed in a telescope on a mountaintop next to DECam for testing. This means assembling it with a compatible mechanical design and high-bandwidth digital processing system.

    If all goes well, they can look realistically to constructing instruments installed with MKIDs and, conceivably, with 100,000 light channels. That’s 20 times more channels than the next-generation technology represented by the Dark Energy Spectroscopic Instrument, a future spectrograph that Fermilab is now helping to construct.

    “We are still some distance away from having a full-on instrument,” Estrada said. “But we are taking the initial steps that would put us closer to this very ambitious goal.”

    See the full article here.

    Fermilab Campus

    Fermi National Accelerator Laboratory (Fermilab), located just outside Batavia, Illinois, near Chicago, is a US Department of Energy national laboratory specializing in high-energy particle physics.

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