Tagged: Dark Energy Survey Toggle Comment Threads | Keyboard Shortcuts

  • richardmitnick 3:20 pm on June 3, 2016 Permalink | Reply
    Tags: , , Dark Energy Survey, Einstein ring,   

    From Dark Energy Survey via Universe Today: “New ‘Einstein Ring’ Discovered By Dark Energy Camera” 

    Dark Energy Icon
    The Dark Energy Survey

    1
    2

    2 Jun , 2016
    Evan Gough, Universe Today

    A rare object called an Einstein Ring has been discovered by a team in the Stellar Populations group at the Instituto de Astrofísica de Canarias (IAC) in Spain. An Einstein Ring is a specific type of gravitational lensing.

    IAC

    Einstein’s Theory of General Relativity predicted the phenomena of gravitational lensing. Gravitational lensing tells us that instead of travelling in a straight line, light from a source can be bent by a massive object, like a black hole or a galaxy, which itself bends space time.

    Einstein’s General Relativity was published in 1915, but a few years before that, in 1912, Einstein predicted the bending of light. Russian physicist Orest Chwolson was the first to mention the ring effect in scientific literature in 1924, which is why the rings are also called Einstein-Chwolson rings.

    Gravitational lensing is fairly well-known, and many gravitational lenses have been observed. Einstein rings are rarer, because the observer, source, and lens all have to be aligned. Einstein himself thought that one would never be observed at all. “Of course, there is no hope of observing this phenomenon directly,” Einstein wrote in 1936.

    The team behind the recent discovery was led by PhD student Margherita Bettinelli at the University of La Laguna, and Antonio Aparicio and Sebastian Hidalgo of the Stellar Populations group at the Instituto de Astrofísica de Canarias (IAC) in Spain. Because of the rarity of these objects, and the strong scientific interest in them, this one was given a name: The Canarias Einstein Ring.

    5
    The “Canarias Einstein Ring.” The green-blue ring is the source galaxy, the red one in the middle is the lens galaxy. The lens galaxy has such strong gravity, that it distorts the light from the source galaxy into a ring. Because the two galaxies are aligned, the source galaxy appears almost circular. Image: This composite image is made up from several images taken with the DECam camera on the Blanco 4m telescope at the Cerro Tololo Observatory in Chile.

    There are three components to an Einstein Ring. The first is the observer, which in this case means telescopes here on Earth. The second is the lens galaxy, a massive galaxy with enormous gravity. This gravity warps space-time so that not only are objects drawn to it, but light itself is forced to travel along a curved path. The lens lies between Earth and the third component, the source galaxy. The light from the source galaxy is bent into a ring form by the power of the lens galaxy.

    When all three components are aligned precisely, which is very rare, the light from the source galaxy is formed into a circle with the lens galaxy right in the centre. The circle won’t be perfect; it will have irregularities that reflect irregularities in the gravitational force of the lens galaxy.

    4
    Another Einstein Ring. This one is named LRG 3-757. This one was discovered by the Sloan Digital Sky Survey, but this image was captured by Hubble’s Wide Field Camera 3. Image: NASA/Hubble/ESA

    The objects are more than just pretty artifacts of nature. They can tell scientists things about the nature of the lens galaxy. Antonio Aparicio, one of the IAC astrophysicists involved in the research said, “Studying these phenomena gives us especially relevant information about the composition of the source galaxy, and also about the structure of the gravitational field and of the dark matter in the lens galaxy.”

    Looking at these objects is like looking back in time, too. The source galaxy is 10 billion light years from Earth. Expansion of the Universe means that the light has taken 8.5 billion light years to reach us. That’s why the ring is blue; that long ago, the source galaxy was young, full of hot blue stars.

    The lens itself is much closer to us, but still very distant. It’s 6 billion light years away. Star formation in that galaxy likely came to a halt, and its stellar population is now old.

    The discovery of the Canarias Einstein Ring was a happy accident. Bettinelli was pouring over data from what’s known as the Dark Energy Camera (DECam) of the 4m Blanco Telescope at the Cerro Tololo Observatory, in Chile. She was studying the stellar population of the Sculptor dwarf galaxy for her PhD when the Einstein Ring caught her attention. Other members of the Stellar Population Group then used OSIRIS spectrograph on the Gran Telescopio CANARIAS (GTC) to observe and analyze it further.

    Gran Telescopio de Canarias exterior

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    DECam, built at FNAL
    NOAO/CTIO Victor M Blanco 4m Telescope which houses the DECam at Cerro Tololo, Chile
    DECam, built at FNAL; NOAO/CTIO Victor M Blanco 4m Telescope which houses the DECam at Cerro Tololo, Chile

    The Dark Energy Survey (DES) is designed to probe the origin of the accelerating universe and help uncover the nature of dark energy by measuring the 14-billion-year history of cosmic expansion with high precision. More than 120 scientists from 23 institutions in the United States, Spain, the United Kingdom, Brazil, and Germany are working on the project. This collaboration [has built] an extremely sensitive 570-Megapixel digital camera, DECam, and [has mounted] it on the Blanco 4-meter telescope at Cerro Tololo Inter-American Observatory high in the Chilean Andes. Started in Sept. 2012 and continuing for five years, DES will survey a large swath of the southern sky out to vast distances in order to provide new clues to this most fundamental of questions.

     
  • richardmitnick 9:00 pm on April 29, 2016 Permalink | Reply
    Tags: , , Dark Energy Survey, DEScientist of the Week: Ting Li   

    From DES: “DEScientist of the Week: Ting Li” 

    Dark Energy Icon

    The Dark Energy Survey

    April 29, 2016

    Meet Ting Li, Graduate Student at Texas A&M University!

    1

    Ting’s main research interest is to study the stellar substructure in our own Milky Way — dwarf galaxies and stellar streams. These features in the Milky Way can help us understand the nature of dark matter. She helps the team discover these stellar associations using DES data, and also follows them spectroscopically using the world’s largest optical telescopes, including Magellan Telescopes, the Vary Large Telescope, etc.

    6.5 meter Magellan Telescopes located at Carnegie’s Las Campanas Observatory, Chile.
    6.5 meter Magellan Telescopes located at Carnegie’s Las Campanas Observatory, Chile

    ESO/VLT at Cerro Paranal
    ESO/VLT at Cerro Paranal, Chile

    Apart from the scientific research, Ting also works on the DES infrastructures. Specifically, she works on the atmospheric transmission monitoring camera and the spectrophotometric calibration system for DECam. These two auxiliary systems will help DES to achieve high precision photometry, which is crucial for DES scientist to understand the nature of dark energy.

    We asked Ting a few more questions — here’s what she had to say:

    If you weren’t a scientist, what would your dream job be?

    I would want to be an astronaut, or more specifically, a job that can take me to space. Even if I could not go to space, I still hope that an instrument I build could go to space sometime in the future. I’m probably not physically strong enough to be qualified as a astronaut, but I’m good at astrophysics and instrumentation. I also speak many languages (English, Chinese, Japanese, little French and poor Spanish…). I still hope one day the dream would come true🙂

    What is your secret talent?

    Ting-quisition: my graduate peers made this word for me, it means that Ting asks someone questions until that person “dies”. I’m not sure if that’s a talent or not, but I do like to ask questions and I learn a lot from asking.

    What do you think has been the most exciting advance in physics / astronomy in the last 10 years?

    Sky survey with CCDs, starting from SDSS.

    SDSS Telescope at Apache Point, NM, USA
    SDSS Telescope at Apache Point, NM, USA

    Astronomy has been significantly changed since the birth of CCDs and sky surveys. The progress is huge and revolutionary in the past 10 years. That’s why I joined DES and I think it will be the next revolution (before LSST starts).

    Thinking back to when you were an undergrad in physics (if applicable), was there anything you were taught then that is not taught now?

    I wish I had learned more about python and more about statistics.

    Any advice for aspiring scientists?

    This is the advice I would give to the students who might be considering going to graduate school and pursuing a career in scientific research.
    I would say that graduate school is tough, so make sure that’s what you want before you decide to go that route. If you decide to take it, then enjoy it. Graduate school is much more independent, compared to the undergraduate program. Instead of professors telling you what to do in your undergraduate study, you are the one who needs to make the decisions about yourself most of the time. You also have to learn a lot of new things by yourself and solve the problems by yourself. So make sure you pick a field that you like and you are interested in.
    The difficulties can sometimes be incredibly frustrating. However, part of getting closer to becoming a qualified Ph.D. is dealing with setbacks and experiencing failure. Maybe you don’t feel that you are gaining new knowledge every day, or maybe you feel that you are standing still after many days of hard work. But after several months or even years, you will know that you have already made a huge improvement in your research ability. You won’t see the changes every day, but be patient and persistent, and you will succeed.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition
    DECam, built at FNAL
    DECam, built at FNAL
    CTIO Victor M Blanco 4m Telescope
    CTIO Victor M Blanco 4m Telescope interior
    CTIO Victor M Blanco Telescope at Cerro Tololo which houses the DECAm

    The Dark Energy Survey (DES) is designed to probe the origin of the accelerating universe and help uncover the nature of dark energy by measuring the 14-billion-year history of cosmic expansion with high precision. More than 120 scientists from 23 institutions in the United States, Spain, the United Kingdom, Brazil, and Germany are working on the project. This collaboration [has built] an extremely sensitive 570-Megapixel digital camera, DECam, and [has mounted] it on the Blanco 4-meter telescope at Cerro Tololo Inter-American Observatory high in the Chilean Andes. Started in Sept. 2012 and continuing for five years, DES will survey a large swath of the southern sky out to vast distances in order to provide new clues to this most fundamental of questions.

     
  • richardmitnick 3:01 pm on April 29, 2016 Permalink | Reply
    Tags: , , Dark Energy Survey, Superluminous Supernova   

    From DES- “From the DArchive: A Newly Discovered Superluminous Supernova” 

    Dark Energy Icon

    The Dark Energy Survey

    April 29, 2016
    Mathew Smith
    Edited by R.C. Wolf & R. Cawthon

    Science paper:
    DES14X3taz: A Type I Superluminous Supernova Showing a Luminous, Rapidly Cooling Initial Pre-Peak Bump

    In this paper we present DES14X3taz, a newly discovered superluminous supernova (SLSN). This particular SLSN is very unusual – if you look at the evolution of its brightness over time, or its light curve, there are two peaks (most only have one)! In our analysis, we attempt to explain what physical process might cause such an occurrence and determine if this is truly a unique event or common to all SLSNe.

    Although the initial DECam data was fairly indicative that this was a particularly interesting object, we had to use additional information to confirm our discovery. By combining optical light-curve data from DES and its sister survey, the Survey Using Decam for Superluminous Supernovae (SUDSS), we were able to plot the evolution of brightness over time (light-curve) of DES14X3taz and find its brightest point. We then used spectra obtained on the Gran Telescopino Canarias (GTC) in La Palma, Spain to estimate the distance to this event, and thus its peak brightness, and unambiguously confirmed that it is a SLSNe.

    Gran Telescopino Canarias exterior
    Gran Telescopino de Canaries interior
    Gran Telescopino de Canaries

    What really distinguishes DES14X3taz from previously discovered SLSNe is the presence of an early “bump” in the light curve prior to the main light-curve. The figure below shows these features for DES14X3taz.

    1

    In addition to detecting this bump, we were lucky to have observed this SLSN before explosion and to have observed it at many points during its lifetime; most other observed SLSNe have been discovered post-explosion or do not have such a large a sample of measurements.

    Our observations with DECam allowed us to obtain colour information, from observations in several filters, of the bump. This enabled us to probe the physical processes driving these super-luminous events by comparing our data to pre-existing theoretical models. In the figure below, the colored-circle points are real data, and the dashed lines represent theoretical observations for different physical processes that we think might be motivating this behavior.

    2

    Fitting models to the main curve show that the physical mechanism driving the explosion is consistent with a magnetar, a rapidly rotating neutron star (as seen in the match to the Extended Material Around the Star). In the figure, this is consistent with the solid lines. Fitting black-body curves to the DES data of DES14X3taz, we show that the initial peak cools rapidly, before a period of reheating, which drives the main part of the light-curve. Using chi-squared statistics, we compare photometric data of the initial peak with various models of shock-cooling and find that shock from material at an extended radius is consistent with observations. We also find a sample of previously discovered SLSNe that also exhibit this early bump in their light curves; therefore, we believe our findings suggest a unified physical interpretation for all SLSNe.

    SLSNe are a new class of transient event, with potentially exciting consequences for cosmology. Recent work (Inserra & Smartt 2014) has suggested that these events may even be “standardisable candles”, and thus useful to measure distances to the high redshift Universe. As these events are more luminous than traditional Type Ia supernovae they have the potential to extend SN cosmology to larger distances than currently possible. However, little is well-understood about the explosion mechanism driving these events and we will need to understand more about the origin of SLSNe as we explore utilizing them as cosmological probes.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition
    DECam, built at FNAL
    DECam, built at FNAL
    CTIO Victor M Blanco 4m Telescope
    CTIO Victor M Blanco 4m Telescope interior
    CTIO Victor M Blanco Telescope at Cerro Tololo which houses the DECAm

    The Dark Energy Survey (DES) is designed to probe the origin of the accelerating universe and help uncover the nature of dark energy by measuring the 14-billion-year history of cosmic expansion with high precision. More than 120 scientists from 23 institutions in the United States, Spain, the United Kingdom, Brazil, and Germany are working on the project. This collaboration [has built] an extremely sensitive 570-Megapixel digital camera, DECam, and [has mounted] it on the Blanco 4-meter telescope at Cerro Tololo Inter-American Observatory high in the Chilean Andes. Started in Sept. 2012 and continuing for five years, DES will survey a large swath of the southern sky out to vast distances in order to provide new clues to this most fundamental of questions.

     
  • richardmitnick 7:46 pm on April 22, 2016 Permalink | Reply
    Tags: , , Dark Energy Survey, DEScientist of the Week: Boris Leistedt   

    From DES: “DEScientist of the Week: Boris Leistedt” 

    Dark Energy Icon

    The Dark Energy Survey

    April 22, 2016
    The Dark Energy Survey

    1

    Meet Boris Leistedt, Postdoc at New York University!

    Boris’ primary research interest is data analysis.

    We asked Boris a few more questions — here’s what he had to say:

    What is your favorite part about being a scientist?

    The people. Physics and astronomy are fascinating topics, but the job wouldn’t be the same without all the amazing people working in universities, research labs and institutes around the world. I feel lucky to know and collaborate with so many exceptional scientists who come from an incredible variety of backgrounds. Sharing a passion like physics with so many colleages (who sometimes become good friends!) is very precious and this is clearly what I enjoy the most in my job.

    When did you know you wanted to be a scientist?

    I’ve always been into sciences, maths and physics in particular, but I clearly remember the day I realized all my favourite topics converged in astronomy. I first studied electrical engineering at university but I eventually returned to physics by the end of my undergraduate curriculum, and it is a research internship that crystalized my interest in observational cosmology and pushed me to pursue a PhD.

    What motivates / inspires you?

    What motivates me most is to work on hard problems involving complicated data sets and interesting physics. In that respect cosmology is perfect because it currently has a unique position at the intersection of physics, mathematics, and computer science. To answer profound questions about the Universe, for example to know its age or dynamics, cosmologists analyse very large data sets gathered by telescope and satellites, and confront them to mathematical predictions. We typically use very advanced methods from other fields such as statistics and computer science. Knowing that pretty much any topic trending in these fields might be relevant to my work is very exciting.

    Any advice for aspiring scientists?

    Follow your dreams and never give up. You are clever enough to do whatever you want in life. The world is full of great people who will give you advice and support you. You just need to be vocal about your goals and to be ready to gather all the help you can. Don’t worry, you will have tons of opportunities to give it back and support others too in due course!

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition
    DECam, built at FNAL
    DECam, built at FNAL
    CTIO Victor M Blanco 4m Telescope
    CTIO Victor M Blanco 4m Telescope interior
    CTIO Victor M Blanco Telescope at Cerro Tololo which houses the DECAm

    The Dark Energy Survey (DES) is designed to probe the origin of the accelerating universe and help uncover the nature of dark energy by measuring the 14-billion-year history of cosmic expansion with high precision. More than 120 scientists from 23 institutions in the United States, Spain, the United Kingdom, Brazil, and Germany are working on the project. This collaboration [has built] an extremely sensitive 570-Megapixel digital camera, DECam, and [has mounted] it on the Blanco 4-meter telescope at Cerro Tololo Inter-American Observatory high in the Chilean Andes. Started in Sept. 2012 and continuing for five years, DES will survey a large swath of the southern sky out to vast distances in order to provide new clues to this most fundamental of questions.

     
  • richardmitnick 5:13 pm on March 25, 2016 Permalink | Reply
    Tags: , , Dark Energy Survey, Meet Jörg Dietrich   

    From DES: “DEScientist of the Week: Jörg Dietrich” 

    Dark Energy Icon

    The Dark Energy Survey

    March 25, 2016

    Meet Jörg Dietrich, Postdoc at Ludwig-Maximilians-Universität München!

    1

    Jörg mostly works on galaxy clusters and gravitational lensing. He coordinates the work of like-minded people in the Cluster Lensing Science analysis group.

    It is one of the predictions of Einstein’s theory of General Relativity that light is bent when it passes massive objects. Galaxy clusters are the most massive objects in the Universe. By studying how light is deflected when it encounters such an object as it travels from distant galaxies to our telescope.

    This enables us to measure how heavy these clusters are (up to 1,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000 kg) and in turn tells us something about the history of the Universe.

    We asked Jörg a few more questions — here’s what he had to say:
    What is your favorite part about being a scientist?

    I get to work with a lot very smart people from whom I have learned so much.

    Do you have kids? Do they want to be scientists too?

    I have a 6 months old son. Currently his interests are limited to fluid dynamics.
    What do you think has been the most exciting advance in physics / astronomy in the last 10 years?

    The discovery of gravitational waves, of course!

    Gravitational waves. Credit: MPI for Gravitational Physics/W.Benger-Zib
    Credit: MPI for Gravitational Physics/W.Benger-Zib

    Black holes merging Swinburne Astronomy Productions
    Black holes merging Swinburne Astronomy Productions

    Cornell SXS teamTwo merging black holes simulation
    Cornell SXS team. Two merging black holes simulation

    MIT/Caltech Advanced aLIGO Hanford Washington USA installation
    MIT/Caltech Advanced aLIGO Hanford Washington USA installation

    It open a whole new window to the Universe and it is very hard to overstate the significance of it.

    Any advice for aspiring scientists?

    Do what you love. Work hard. Science takes more hard work than genius.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    DECam, built at FNAL
    DECam, built at FNAL

    CTIO Victor M Blanco 4m Telescope
    CTIO Victor M Blanco 4m Telescope interior
    CTIO Victor M Blanco Telescope at Cerro Tololo which houses the DECAm

    The Dark Energy Survey (DES) is designed to probe the origin of the accelerating universe and help uncover the nature of dark energy by measuring the 14-billion-year history of cosmic expansion with high precision. More than 120 scientists from 23 institutions in the United States, Spain, the United Kingdom, Brazil, and Germany are working on the project. This collaboration [has built] an extremely sensitive 570-Megapixel digital camera, DECam, and [has mounted] it on the Blanco 4-meter telescope at Cerro Tololo Inter-American Observatory high in the Chilean Andes. Started in Sept. 2012 and continuing for five years, DES will survey a large swath of the southern sky out to vast distances in order to provide new clues to this most fundamental of questions.

     
  • richardmitnick 11:02 am on March 8, 2016 Permalink | Reply
    Tags: , Dark Energy Survey, ,   

    From Symmetry: “Art of Darkness” 

    Symmetry

    03/08/16
    Rashmi Shivni

    The Dark Energy Survey’s art show offers a glimpse of the expanding universe.

    Imagine a clear night in the mountains, away from glaring city lights. In the sky, gleaming speckles from distant stars cascade into the bright streams of the Milky Way. Almost everything in sight is part of our home galaxy.

    To provide a glimpse beyond our galaxy and into an ever-expanding universe, the Department of Energy’s Fermilab is hosting the Art of Darkness, an exhibition by Dark Energy Survey collaborators. The exhibit opened Feb. 19 in the Fermilab Art Gallery and showcases images from celestial objects from DES’ Dark Energy Camera, DECam.

    Dark Energy Icon
    Dark Energy Camera
    CTIO Victor M Blanco 4m Telescope
    Dark Energy Survey, DECam, and the Victor M Blanco telescope in Chile, which houses DECam

    “We see so much information in the artwork that ends up being a small part of the whole DES footprint,” says Brian Nord, an astrophysicist and contributor to the DES art exhibit. “This showcase highlights the depth of a universe we don’t completely see with the naked eye.”

    DES is a five-year survey that covers one-eighth of the sky to better describe dark energy–the force driving the universe’s accelerated expansion. The collaboration has more than 400 scientists from around 30 institutions. It uses the 570-megapixel DECam, one of the largest digital cameras in the world, perched atop the Blanco Telescope at the Cerro Tololo Inter-American Observatory in Chile.

    The select few galaxies in the exhibit are from a narrow swath of the sky survey. Creating these photographs for the gallery requires an image-processing pipeline, a method of “cleaning up” the images by removing artifacts such as satellites, airplane or cosmic ray trails, or defects from the camera hardware, says Nikolay Kuropatkin, a DES computational physics software developer.

    “We use this pipeline for our scientific surveys, but it turns out to be a good tool for artwork as well,” says Kuropatkin.

    DECam in action
    Watching DECam in action

    DECam is a monochromatic camera. Part of the exhibit process required Marty Murphy, an operations specialist in Fermilab’s Accelerator Division, and Nord to add color and further edit the images with an artistic eye.

    Five different filters are individually placed between the telescope and camera to gather color information about the galaxy in view. Each filter corresponds to a different bandwidth, or a range of frequencies, on the electromagnetic spectrum. Those single-filter images are then combined to produce a full-color photo.

    “A lot of the information in the initial pictures is lost because lots of light emits from the invisible ends of the electromagnetic spectrum,” Murphy says. “We try to bring out colors from the visible spectrum that somewhat represent what’s there and fix any discrepancies between reality and the artwork.”

    This close-to-reality representation also helps scientists understand the properties of the galaxies in view. For instance, small clusters that appear red or warmer in color tell us that they are further away from us due to the expansion of the universe, says Brian Yanny, a DES data management project scientist.

    “From that we can figure out how big space is and how dark energy might be affecting the size of the universe from the redshift of the object,” he says.

    But the art gallery is made of more than just galaxy images. There’s a 3D print of the cosmic web derived from a computer simulation. There’s also a colorful dark matter map of the actual cosmic web that DES observes made using gravitational lensing, a distortion seen when light from background galaxies bends from a massive foreground object.

    Universe map  2MASS Extended Source Catalog XSC
    Universe map 2MASS Extended Source Catalog XSC

    “Once you know the explanations behind the workings of the cosmos, you realize there are forces out there that make the universe beautiful,” Yanny says. “We’ve come to understand that dark matter holds the shape of spiral galaxies, which have a rapid and unstable spin. Without dark matter, we would not experience the cosmos the way we do now.”

    Alongside the DECam photos are images and time-lapse videos from the Blanco Telescope and the surrounding landscapes that provide another perspective of how the very act of research helps bring out the beauty of the universe. The images (on display at Fermilab through April) come from 11 DES collaborators and were collected over the first three seasons of observations, which ended in February. DES will take data for two more years, from August to February.

    “I hope the images from the camera combined with the pictures from the site can somehow merge two perspectives,” Nord says. “In essence, it’s humans looking out to the cosmos and the universe looking back at us.”

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    Symmetry is a joint Fermilab/SLAC publication.


     
  • richardmitnick 6:22 pm on February 8, 2016 Permalink | Reply
    Tags: , , Dark Energy Survey   

    From DES: “Dark Energy Camera Legacy Survey Announces Second Data Release” 

    Dark Energy Icon

    The Dark Energy Survey

    The Dark Energy Camera Legacy Survey (DECaLS) announced its second data release (DR2) on 15 January 2016. DECaLS (PIs: David Schlegel and Arjun Dey) is in the middle of mapping 6200 square degrees of the extragalactic sky in g, r and z using the Dark Energy Camera on the Blanco 4-m telescope at the Cerro Tololo Inter-American Observatory. The project is designed to investigate a broad range of astrophysical questions, ranging from studies of Milky Way structure and galaxy evolution to large-scale structure and cosmology. The survey goals and the first data release were described in an earlier issue of Currents.

    DECaLS DR2 includes reduced images and source catalogs covering approximately 2100 square degrees of sky in g- and r-band and 5300 square degrees in z-band. Roughly 1800 square degrees has been imaged in all three bands. The area covered can be visualized using the project’s Imagine Sky Viewer built by Dr. Dustin Lang. An Image Gallery of Large Galaxies constructed by Dr. John Moustakas is also available.

    DR2 includes not only all the data taken by DECaLS from August 2014 through June 2015, but also all public DECam g-, r-, and z-band data within the DECaLS footprint obtained by other projects. The latter include data (now public) from the Dark Energy Survey in the “Stripe 82” region.

    Mapping the Sky. DECaLS is one of three surveys that will jointly image 14,000 square degrees—nearly one-third of the sky—to provide targets for the Dark Energy Spectroscopic Instrument cosmology project. The other two projects are the Mayall z-band Legacy Survey (MzLS), which begins in February 2016, and the Beijing-Arizona Sky Survey (BASS), which is underway at the Bok Telescope on Kitt Peak. MzLS and BASS will provide g- ,r-, and z- band imaging at declinations north of +34 degrees.

    Making it Public. All three surveys are being run as public projects, with no proprietary period for the raw data. Reduced images are available as soon as the pipeline processing at NOAO is complete, and official data releases are scheduled every 6 months. All of the data will be served by the NOAO Science Archive and the National Energy Research Scientific Computing Center at the Lawrence Berkeley National Laboratory. For further details, please see legacysurvey.org.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition
    Dark Energy Camera
    DECam, built at FNAL

    CTIO Victor M Blanco 4m Telescope
    CTIO Victor M Blanco 4m Telescope interior
    CTIO Victor M Blanco Telescope at Cerro Tololo which houses the DECAm

    The Dark Energy Survey (DES) is designed to probe the origin of the accelerating universe and help uncover the nature of dark energy by measuring the 14-billion-year history of cosmic expansion with high precision. More than 120 scientists from 23 institutions in the United States, Spain, the United Kingdom, Brazil, and Germany are working on the project. This collaboration [has built] an extremely sensitive 570-Megapixel digital camera, DECam, and [has mounted] it on the Blanco 4-meter telescope at Cerro Tololo Inter-American Observatory high in the Chilean Andes. Started in Sept. 2012 and continuing for five years, DES will survey a large swath of the southern sky out to vast distances in order to provide new clues to this most fundamental of questions.

     
  • richardmitnick 2:25 pm on February 5, 2016 Permalink | Reply
    Tags: , , Dark Energy Survey, David Parkinson Interview   

    From DES: “DEScientist of the Week: David Parkinson” 

    Dark Energy Survey

    The Dark Energy Survey

    February 5, 2016
    No writer credit found

    Meet David Parkinson, Postdoc at the University of Queensland!

    DES David Parkinson
    David Parkinson

    At the University of Sussex, David was part of the DES supernova project, looking at predicted constraints on the dark energy from using supernovae as standard candles. Now at the University of Queensland, he is part of the OzDES survey, making follow-up observations of DES galaxies using the AAOmega spectrograph on the 3.9m Anglo-Australian Telescope.

    ANU AAOmega spectrograph Anglo Australian Telescope
    AAO AAOmega spectrograph on the Anglo-Australian Telescope

    Anglo Australian Telescope Exterior
    Anglo Australian Telescope Interior
    AAO Anglo-Australian Telescope

    We asked David a few more questions — here’s what he had to say:

    What is your favorite part about being a scientist?

    My favorite part of being a scientist is thinking about the big questions of why the Universe is the way it is. Why do we think our theory of gravity is the correct one? Why does the Universe have only three spatial dimensions, not two or forty-seven? And I enjoy the process of finding things out, of using my mind to learn something new, based on logic and mathematics.

    When did you know you wanted to be a scientist?

    I grew up learning about space travel and astronomy from my Dad, who worked as a rocket engineer. But I didn’t actually want to be a scientist growing up. Originally I wanted to be an archaeologist! But learning about modern physics (cosmology, quantum mechanics) as a teenager I changed my mind, and went into astrophysics instead.

    Do you have any hobbies or play any sports?

    I play a lot of board games. One of my favourites is “Ticket to Ride” (where the aim is to build as many train lines as possible), which me and my wife play a lot. Board games have come a long way, and are a lot more fun than the fairly dull games I remember from my childhood.

    If you weren’t a scientist, what would your dream job be?

    I can’t really imagine not being a scientist, but if I wasn’t I would like to be a writer. Fiction or non-fiction, books or screenplays, it doesn’t matter – it would be great to be a professional writer.

    Any other fun facts we should know?

    I was observing at the Anglo-Australian Telescope during the bush fires that threatened Siding Spring Observatory in January 2013 [http://www.space.com/19254-australi…. ].

    Siding Spring Campus
    Siding Spring Observatory

    They actually had to evacuate us from the site! It is scary to be told “The mountain you are standing on is on fire. Please leave as quickly as you can.”

    Any advice for aspiring scientists?

    Science is a hard field to work in, and requires a high degree of dedication. If you’re very interested in science, but happy just to read about it in the newspaper, maybe think about a different career. But if you need to find things out for yourself, then science can be an incredibly rewarding and satisfying career path.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition
    Dark Energy Camera

    The Dark Energy Survey (DES) is designed to probe the origin of the accelerating universe and help uncover the nature of dark energy by measuring the 14-billion-year history of cosmic expansion with high precision. More than 120 scientists from 23 institutions in the United States, Spain, the United Kingdom, Brazil, and Germany are working on the project. This collaboration [has built] an extremely sensitive 570-Megapixel digital camera, DECam, and [has mounted] it on the Blanco 4-meter telescope at Cerro Tololo Inter-American Observatory high in the Chilean Andes. Started in Sept. 2012 and continuing for five years, DES will survey a large swath of the southern sky out to vast distances in order to provide new clues to this most fundamental of questions.

     
  • richardmitnick 10:44 am on January 19, 2016 Permalink | Reply
    Tags: , , Dark Energy Survey,   

    From FNAL: “Dark Energy Survey releases early data” 

    FNAL II photo

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

    Dark Energy Icon

    January 19, 2016
    Andre Salles

    Dark Energy Camera
    CTIO Victor M Blanco 4m Telescope
    DECam, the Dark Energy camera, built at FNAL, and the CTIO/Victor M Blanco 4 meter telescope in Chile in which it is housed.

    The Dark Energy Survey is now in its third year of capturing eye-popping images of the cosmos with its primary instrument, the Dark Energy Camera. Before the survey proper began in August 2013, however, scientists spent months testing the camera, putting it through its paces.

    Now, catalogs of galaxies and stars derived from the data collected during that Science Verification season (November 2012 to February 2013) have been released to the public. Astronomers and astronomy buffs can download the data from the website for the National Center for Supercomputing Applications at the University of Illinois, which manages the processing of all the images taken for the Dark Energy Survey.

    This is good news for the astronomy community, as the catalogs released last week contain measurements of more than 25 million objects. Scientists on the Dark Energy Survey have used this data to, among other things, create the largest-yet dark matter mass map. The Science Verification data covers only 3 percent of the survey area (itself roughly one-eighth of the sky), so there is much more to come.

    The Dark Energy Survey is a five-year effort to map that survey area in unprecedented detail. Scientists will use the data collected to probe the phenomenon of dark energy, the mysterious force that makes up about three-quarters of the universe. The Dark Energy Camera was built and tested at Fermilab and is mounted on the Blanco telescope at the National Optical Astronomy Observatory’s Cerro Tololo Inter-American Observatory in Chile.

    The Dark Energy Survey is a collaboration of more than 300 scientists from 25 institutions in six countries. Funding for DES projects is provided by the U.S. Department of Energy Office of Science, the National Science Foundation, and other funding agencies.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    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. Fermilab is America’s premier laboratory for particle physics and accelerator research, funded by the U.S. Department of Energy. Thousands of scientists from universities and laboratories around the world
    collaborate at Fermilab on experiments at the frontiers of discovery.

     
  • richardmitnick 8:41 am on January 16, 2016 Permalink | Reply
    Tags: A New Method to Measure Galaxy Bias, , , Dark Energy Survey   

    From DES: “A New Method to Measure Galaxy Bias by Combining the Density and Weak Lensing Fields” 

    Dark Energy Icon
    The Dark Energy Survey

    January 15, 2016
    A New Method to Measure Galaxy Bias by Combining the Density and Weak Lensing Fields (http://arxiv.org/abs/1601.00160)
    Galaxy Bias From the DES Science Verification Data: Combining Galaxy Density Maps and Weak Lensing Maps (http://arxiv.org/abs/1601.00405)

    We can study the large scale structures of matter that form in the Universe from the distribution of the galaxies that we observe with telescopes. However, most of the matter in the Universe is made of dark matter, which does not interact with light, and hence it cannot be directly observed. Because of this, it is very important to understand the relation between the dark matter distribution and the galaxy distribution. The densest areas of dark matter will pull together visible matter, like stars and gas, eventually forming galaxies. Conversely, areas with less dark matter may not host galaxies.

    In these papers, we develop and apply a method to make a direct measurement of galaxy bias, a parameter that quantifies the relation between the dark matter and galaxy densities in the Universe. With a very good knowledge of galaxy bias, we would be able to infer the dark matter distribution form the distribution of galaxies with a very high precision.

    Our method uses measurements of gravitational lensing. According to [Albert] Einstein’s theory of [general relativity], when light travels from a source, its trajectory is distorted due to the presence of mass around the trajectory. When the light traveling to us from distant ‘background’ galaxies gets distorted in this way, the shapes of the galaxies appear to change very slightly, but in a recognizable pattern. This effect is called weak gravitational lensing. By studying weak lensing, we can measure the projected total mass between us and the ‘background’ galaxies and generate maps of this mass distribution (which is mostly dark matter).

    It’s important to note note that the ‘background’ galaxies are different than the galaxies [of which] we are measuring the distribution . As seen in the example figure below, the galaxies [of which] we measure the distribution (shaded in yellow) are closer, and we measure how they differ in their distribution compared to dark matter. The ‘background’ galaxies are further away, and their only use in this paper is to see how their shapes are distorted, which tells us there is closer dark matter causing gravitational lensing.

    Temp 1
    Image credit: https://upload.wikimedia.org/wikipedia/commons/b/b9/Gravitational-lensing-3d.png

    We study the relation between the galaxy distribution and the dark matter distribution (the galaxy bias) by comparing the distribution of mass inferred from weak lensing with the distribution of the galaxies in the same region. In particular, we calculate the weak lensing effect that we would detect if the distribution of galaxies and matter were the same. Then, we compare this calculated weak lensing field with the real one, that we obtain from the distortions in the shape of the ‘background’ galaxies. We obtain the galaxy bias parameter from comparing the calculated and the real weak lensing fields, which represent the galaxy and matter distributions respectively.

    Key to our analysis was the use of simulations. Simulations are fake data that we use to test analysis techniques in a controlled way. The properties of these simulated universes are calculated according to the laws of [general relativity] and include the effects of dark matter and dark energy close to what we observe in the real Universe. In the simulation, we produce galaxy catalogues and weak lensing effects that can be used to test our analysis techniques. Since we know the “true” galaxy bias in our simulations, we can examine how different measurement errors can cause our measurements to deviate from the true answer. Potential errors due to the area of the sky we use, and the uncertainty of the distance to the ‘background’ galaxies are especially important effects we check for in the simulations.

    Temp 2

    Above is a plot of our weak lensing maps from DES science verification data. Red indicates a higher density of matter in that direction. Blue indicates an area under-dense in matter.

    The figure below shows our measurement of how galaxy bias changes with redshift (or equivalently, how it changes through the history of the Universe), and compares our results with other studies from DES science verification data. The differences may be due to errors, or intrinsic differences of how the galaxy bias is measured by these different techniques. More data from DES should give us greater insight on galaxy bias from multiple techniques.

    Temp 3
    Chang+ 2016, Figure 6

    We find that our results are comparable with other studies of galaxy bias in this DES dataset, with some differences. Based on studies with simulations, we find that our technique’s accuracy improves greatly with area of the survey. Given that science verification data is only 3% of the full DES area (150 out of 5000 square degrees), the full benefits of our technique can be applied with future DES data.
    Galaxy bias is an unknown quantity that affects many attempts to understand cosmology from direct observations of the distribution and evolution of galaxies. Measurements of galaxy bias will allow us to infer the dark matter distribution and study the evolution of structure in the Universe more precisely, which is crucial for understanding the nature of dark energy.

    About the DArchive Authors:

    5
    Arnau Pujol graduated in Physics in Barcelona (Universitat Autònoma de Barcelona). After obtaining a Masters in high energy physics, astrophysics and cosmology, he started to work in the Institut de Ciències de l’Espai (ICE) from Barcelona as a PhD student. He is currently finishing his PhD thesis, where he has been focused on the study of galaxy clustering and bias.

    6
    After finishing undergraduate in Taiwan (National Taiwan University), Chihway Chang graduated from Stanford University as a PhD, where she worked on LSST image simulations and weak gravitational lensing. She then moved to the beautiful country of Switzerland as a postdoc at ETH Zurich, where she joined DES and began exploring the exciting dataset from DES. She works mainly in weak lensing, generating mass maps and experimenting on different ways of using them together with other cosmological probes.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition
    Dark Energy Camera

    The Dark Energy Survey (DES) is designed to probe the origin of the accelerating universe and help uncover the nature of dark energy by measuring the 14-billion-year history of cosmic expansion with high precision. More than 120 scientists from 23 institutions in the United States, Spain, the United Kingdom, Brazil, and Germany are working on the project. This collaboration [has built] an extremely sensitive 570-Megapixel digital camera, DECam, and [has mounted] it on the Blanco 4-meter telescope at Cerro Tololo Inter-American Observatory high in the Chilean Andes. Started in Sept. 2012 and continuing for five years, DES will survey a large swath of the southern sky out to vast distances in order to provide new clues to this most fundamental of questions.

     
c
Compose new post
j
Next post/Next comment
k
Previous post/Previous comment
r
Reply
e
Edit
o
Show/Hide comments
t
Go to top
l
Go to login
h
Show/Hide help
shift + esc
Cancel
Follow

Get every new post delivered to your Inbox.

Join 597 other followers

%d bloggers like this: