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  • richardmitnick 6:03 pm on December 17, 2018 Permalink | Reply
    Tags: , HAWC High Altitude Cherenkov Experiment, ,   

    From U Wisconsin IceCube Collaboration: “IceCube and HAWC unite efforts to dissect the cosmic-ray anisotropy” 

    U Wisconsin ICECUBE neutrino detector at the South Pole

    IceCube employs more than 5000 detectors lowered on 86 strings into almost 100 holes in the Antarctic ice NSF B. Gudbjartsson, IceCube Collaboration

    Lunar Icecube

    IceCube DeepCore annotated

    IceCube PINGU annotated


    DM-Ice II at IceCube annotated

    From From U Wisconsin IceCube Collaboration

    17 Dec 2018
    Sílvia Bravo

    HAWC High Altitude Cherenkov Experiment, located on the flanks of the Sierra Negra volcano in the Mexican state of Puebla at an altitude of 4100 meters(13,500ft), at WikiMiniAtlas 18°59′41″N 97°18′30.6″W. searches for cosmic rays

    It was only a few years ago that IceCube provided the first view of the arrival direction distribution of cosmic rays in the Southern Hemisphere. Observations in the Northern Hemisphere, including those from the HAWC gamma-ray observatory earlier this year, had already shown that the number of cosmic rays hitting the atmosphere varied depending on their direction and energy. The anisotropy patterns found in the Southern Hemisphere supported models that pointed to the local interstellar magnetic field as the origin of the dominant effects of this observation.

    In an attempt to better understand the anisotropy, the IceCube Neutrino Observatory and HAWC have united their efforts to study cosmic-ray arrival directions in both hemispheres at the same primary energy. The goal of this combined observation was to get a nearly full-sky coverage to study the propagation of cosmic rays with median energy of 10 TeV through our local interstellar medium as well as the interactions between interstellar and heliospheric magnetic fields. Results have just been accepted for publication in The Astrophysical Journal and include measurements on how the anisotropy modulations are distributed over different angular scales.

    1
    he all-sky distribution in relative intensity of 10 TeV cosmic rays (CR) obtained with the HAWC and IceCube observation. Blue means deficit with respect to the mean CR flux and red excess. On the left, the white arrow indicates the direction of motion of the solar system through the local interstellar medium; the black lines indicate the local interstellar magnetic field lines outside of the heliosphere. On the right, the view of the opposite side of the sky.

    Cosmic rays swirling through space constantly bombard Earth from every direction. Out of every 1,000 cosmic rays there is at most one cosmic ray with a preferred (nonrandom) arrival direction. We refer to this as anisotropy, and this tiny 0.1% effect is what scientists would like to decipher.

    The variations are small but significant and show two different amplitude scales, a large-scale anisotropy with variations of one per mille and a small-scale anisotropy with variations of one per ten thousand.

    The cosmic-ray anisotropy is associated with the distribution of the cosmic ray sources and with the properties of the magnetic fields through which the cosmic rays propagate. However, the limited field of view of any ground-based experiment prevents us from capturing the anisotropy features that are wider than the observable sky.

    The angular variations of this anisotropy support the contribution of two different mechanisms: the mean propagation along the turbulent interstellar magnetic field, which is expected to isotropically diffuse cosmic rays, and the deflection in nearby magnetic fields—the local interstellar magnetic field (LIMF) and the heliosphere—whose relative contribution depends on energy.

    Ground-based experiments typically require averaging the number of cosmic rays along each declination band, to estimate its response to a perfectly isotropic flux. This has the effect of washing out the vertical (north-south) component of the anisotropy. On the other hand, the heliospheric deflections induced on the cosmic-ray particle distribution by the long interstellar propagation are partially aligned along the LIMF and not significantly affected by the north-south blindness.

    In this study, IceCube and HAWC joined efforts to get a full-sky coverage that captures for the first time a full, unbiased picture of the cosmic-ray anisotropy. The work used five years of IceCube data, from May 2011 to May 2016, and two years of HAWC data, from May 2015 and May 2017.

    The fit of the IceCube-HAWC observed anisotropy at 10 TeV shows the expected alignment with the LIMF. Researchers then used this deviation to derive the north-south component of the dipole anisotropy.

    Previous studies of the anisotropy have shown that the dominant dipole variation starts to decrease around 10 TeV and then to abruptly increase again at energies around 100 TeV. This had been explained as a possible effect of the heliosphere, which has a much larger impact for lower energy cosmic rays.

    Deviations of the anisotropy from the LIMF could be due to the motion of the observer and/or to the effects of the heliosphere on the LIMF. However, only a full-sky study of the cosmic-ray anisotropy at different energies will make it possible to distinguish between these or other possible effects, thus enabling a deeper understanding of the properties of the LIMF and the heliosphere.

    See the full article here .

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    IceCube is a particle detector at the South Pole that records the interactions of a nearly massless sub-atomic particle called the neutrino. IceCube searches for neutrinos from the most violent astrophysical sources: events like exploding stars, gamma ray bursts, and cataclysmic phenomena involving black holes and neutron stars. The IceCube telescope is a powerful tool to search for dark matter, and could reveal the new physical processes associated with the enigmatic origin of the highest energy particles in nature. In addition, exploring the background of neutrinos produced in the atmosphere, IceCube studies the neutrinos themselves; their energies far exceed those produced by accelerator beams. IceCube is the world’s largest neutrino detector, encompassing a cubic kilometer of ice.

     
  • richardmitnick 2:44 pm on October 4, 2018 Permalink | Reply
    Tags: , , , , For the first time an international collaboration of scientists has detected highly energetic light coming from the outermost regions of an unusual star system within our own galaxy. The source is a m, HAWC High Altitude Cherenkov Experiment, microquasars SS 433, , UMD-University of Maryland   

    From University of Maryland: “Mountaintop Observatory Sees Gamma Rays from Exotic Milky Way Object” 

    U Maryland bloc

    From University of Maryland

    October 3, 2018
    Emily Edwards
    301-405-2291
    eedwards@umd.edu
    University of Maryland
    College of Computer, Mathematical, and Natural Sciences

    Space jets accelerate particles and send a high-energy signal to Earth.

    HAWC High Altitude Cherenkov Experiment, located on the flanks of the Sierra Negra volcano in the Mexican state of Puebla at an altitude of 4100 meters (13,500 feet), at WikiMiniAtlas 18°59′41″N 97°18′30.6″W. searches for cosmic rays

    The night sky seems serene, but telescopes tell us that the universe is filled with collisions and explosions. Distant, violent events signal their presence by spewing light and particles in all directions. When these messengers reach Earth, scientists can use them to map out the action-packed sky, helping to better understand the volatile processes happening deep within space.

    For the first time, an international collaboration of scientists has detected highly energetic light coming from the outermost regions of an unusual star system within our own galaxy. The source is a microquasar—a black hole that gobbles up stuff from a nearby companion star and blasts out two powerful jets of material. The team’s observations, described in the October 4, 2018 issue of the journal Nature, strongly suggest that electron acceleration and collisions at the ends of the microquasar’s jets produced the powerful gamma rays. Scientists think that studying messengers from this microquasar may offer a glimpse into more extreme events happening at the centers of distant galaxies.

    The team gathered data from the High-Altitude Water Cherenkov Gamma-Ray Observatory (HAWC), which is a detector designed to look at gamma-ray emission coming from astronomical objects such as supernova remnants, quasars and rotating dense stars called pulsars. Now, the team has studied one of the most well-known microquasars, named SS 433, which is about 15,000 light years away from Earth. Scientists have seen about a dozen microquasars in our galaxy and only a couple of them appear to emit high-energy gamma rays. With SS 433’s close proximity and orientation, scientists have a rare opportunity to observe extraordinary astrophysics.

    “SS 433 is right in our neighborhood and so, using HAWC’s unique wide field of view, we were able to resolve both microquasar particle acceleration sites,” said Jordan Goodman, a Distinguished University Professor of Physics at the University of Maryland and U.S. lead investigator and spokesperson for the HAWC collaboration. “By combining our observations with multi-wavelength and multi-messenger data from other telescopes, we can improve our understanding of particle acceleration in SS 433 and its giant, extragalactic cousins, called quasars.”

    Quasars are massive black holes that suck in material from the centers of galaxies, rather than feeding on a single star. They actively expel radiation, which can been seen from across the universe. But they are so far away that most known quasars have been detected because their jets are aimed at Earth—like having a flashlight aimed directly at one’s eyes. In contrast, SS 433’s jets are oriented away from Earth and HAWC has detected similarly energetic light coming from the microquasar’s side.

    Regardless of where they originate, gamma rays travel in a straight line to their destination. The ones that arrive at Earth collide with molecules in the atmosphere, creating new particles and lower-energy gamma rays. Each new particle then smashes into more stuff, creating a particle shower as the signal cascades toward the ground.

    HAWC, located roughly 13,500 feet above sea level near the Sierra Negra volcano in Mexico, is perfectly situated to catch the fast-moving rain of particles. The detector is composed of more than 300 tanks of water, each of which is about 24 feet in diameter. When the particles strike the water they are moving fast enough to produce a shock wave of blue light called Cherenkov radiation. Special cameras in the tanks detect this light, allowing scientists to determine the origin story of the gamma rays.

    The HAWC collaboration examined 1,017 days’ worth of data and saw evidence that gamma rays were coming from the ends of the microquasar’s jets, rather than the central part of the star system. Based on their analysis, the researchers concluded that electrons in the jets attain energies that are about a thousand times higher than can be achieved using earthbound particle accelerators, such as the city-sized Large Hadron Collider, located along the border between France and Switzerland. The jets’ electrons collide with the low-energy microwave background radiation that permeates space, resulting in gamma ray emission. This is a new mechanism for generating high-energy gamma rays in this type of system and is different than what scientists have observed when an object’s jets are aimed at Earth.

    Ke Fang, a co-author of the study and former postdoctoral researcher at the Joint Space-Science Institute, a partnership between UMD and NASA’s Goddard Space Flight Center, said that this new measurement is critical to understanding what is going on in SS 433.

    “Looking at only one kind of light coming from SS 433 is like seeing only the tail of an animal,” said Fang, who is currently an Einstein Fellow at Stanford University. “Thus, we combine all of its signals, from low energy radio to X-ray, with new high-energy gamma ray observations, to find out what kind of beast SS 433 really is.”

    Until now, instruments had not observed SS 433 emitting such highly energetic gamma rays. But HAWC is designed to be very sensitive to this extreme part of the light spectrum. The detector also has a wide field of view that looks at the entire overhead sky all of the time. The collaboration used these capabilities to resolve the microquasar’s structural features.

    “SS 433 is an unusual star system and each year something new has come out about it,” said Segev BenZvi, another co-author of the study and an assistant professor of physics at the University of Rochester. “This new observation of high-energy gamma rays builds on almost 40 years of measurements of one of the weirdest objects in the Milky Way. Every measurement gives us a different piece of the puzzle, and we hope to use our knowledge to learn about the quasar family as a whole.”

    ###

    In addition to Goodman and Fang, UMD Department of Physics co-authors of the paper include graduate students Kristi Engel and Israel Martinez-Castellanos; postdoctoral researcher Colas Rivière; and research scientist Andrew Smith.

    For more information about the HAWC Observatory:
    https://www.hawc-observatory.org/
    http://jqi.umd.edu/news/podcast/jqi-podcast-episode-12

    The HAWC collaboration is funded by the US National Science Foundation (NSF); the US Department of Energy Office of High-Energy Physics; the Laboratory Directed Research and Development program of Los Alamos National Laboratory; Consejo Nacional de Ciencia y Tecnología, México (grants 271051, 232656, 260378, 179588, 239762, 254964, 271737, 258865, 243290, 132197, and 281653) (Cátedras 873, 1563); Laboratorio Nacional HAWC de rayos gamma; L’OREAL Fellowship for Women in Science 2014; Red HAWC, México; DGAPA-UNAM (Dirección General Asuntos del Personal Académico-Universidad Nacional Autónoma de México; grants IG100317, IN111315, IN111716-3, IA102715, 109916, IA102917); VIEP-BUAP (Vicerrectoría de Investigación y Estudios de Posgrado-Benemérita Universidad Autónoma de Puebla); PIFI (Programa Integral de Fortalecimiento Institucional) 2012 and 2013; PRO-FOCIE (Programa de Fortalecimiento de la Calidad en Instituciones Educativas) 2014 and 2015; the University of Wisconsin Alumni Research Foundation; the Institute of Geophysics, Planetary Physics, and Signatures at Los Alamos National Laboratory; Polish Science Centre grant DEC-2014/13/B/ST9/945 and DEC-2017/27/B/ST9/02272; and Coordinación de la Investigación Científica de la Universidad Michoacana. The content of this article does not necessarily reflect the views of these organizations.

    See the full article here .

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    Driven by the pursuit of excellence, the University of Maryland has enjoyed a remarkable rise in accomplishment and reputation over the past two decades. By any measure, Maryland is now one of the nation’s preeminent public research universities and on a path to become one of the world’s best. To fulfill this promise, we must capitalize on our momentum, fully exploit our competitive advantages, and pursue ambitious goals with great discipline and entrepreneurial spirit. This promise is within reach. This strategic plan is our working agenda.

    The plan is comprehensive, bold, and action oriented. It sets forth a vision of the University as an institution unmatched in its capacity to attract talent, address the most important issues of our time, and produce the leaders of tomorrow. The plan will guide the investment of our human and material resources as we strengthen our undergraduate and graduate programs and expand research, outreach and partnerships, become a truly international center, and enhance our surrounding community.

    Our success will benefit Maryland in the near and long term, strengthen the State’s competitive capacity in a challenging and changing environment and enrich the economic, social and cultural life of the region. We will be a catalyst for progress, the State’s most valuable asset, and an indispensable contributor to the nation’s well-being. Achieving the goals of Transforming Maryland requires broad-based and sustained support from our extended community. We ask our stakeholders to join with us to make the University an institution of world-class quality with world-wide reach and unparalleled impact as it serves the people and the state of Maryland.

     
  • richardmitnick 10:48 am on December 11, 2017 Permalink | Reply
    Tags: 3ML-Multi-Mission Maximum Likelihood framework, An abundance of positrons has been found near Earth, , , , , HAWC High Altitude Cherenkov Experiment, , Software in development at Stanford advances the modeling of astronomical observations,   

    From Stanford University: “Software in development at Stanford advances the modeling of astronomical observations” 

    Stanford University Name
    Stanford University

    December 7, 2017
    Taylor Kubota

    A recent study in Science cast doubt on one formerly favored explanation for why an abundance of positrons – the antimatter counterparts of electrons – has been found near Earth. Two nearby collapsed stars, it turns out, aren’t likely to blame because their positrons couldn’t have traveled as far as the Earth.

    1
    Observations of the Geminga pulsar, shown in this illustration, made by the High-Altitude Water Cherenkov Observatory in Mexico indicate that it and another nearby pulsar are unlikely to be the origin of excess antimatter near Earth. (Image credit: Nahks TrEhnl)

    HAWC High Altitude Cherenkov Experiment, located on the flanks of the Sierra Negra volcano in the Mexican state of Puebla at an altitude of 4100 meters, at WikiMiniAtlas 18°59′41″N 97°18′30.6″W.

    This finding, which reopens a debate about a possible role for dark matter in creating those anomalous positrons, required piecing together complex data from the High Altitude Water Cherenkov Observatory (HAWC) in Mexico. HAWC, which looks like an array of giant, corrugated steel water tanks, can precisely reconstruct the direction and energy of incoming light – in the form of high-energy gamma-rays – by recording the particle shower that the gamma-ray photons generate when they enter the atmosphere above the detector.

    In order to analyze that complex dataset, the HAWC collaboration turned to a software designed by Giacomo Vianello, a research scientist in the lab of Peter Michelson at Stanford University and a co-author of the study. The software, called the Multi-Mission Maximum Likelihood (3ML) framework, was originally designed to combine the data of the Fermi gamma-ray space telescope with the data from other instruments.

    NASA/Fermi Telescope


    NASA/Fermi LAT

    Its ability to handle data in multiple formats and the unprecedented flexibility of its modeling tools allowed the HAWC team to question the pulsars’ role in generating the unexpected positrons.

    “My collaborators and I spent many hours designing and developing 3ML for our research but also for other people to use,” Vianello said. “It is very exciting to see that some researchers find it so useful that they decide to use it for high-impact science like what HAWC published.”

    Vianello and the rest of the 3ML team plan to continue improving the software. In addition to working across wavelengths and instruments, they hope it can be used with messengers other than light, such as polarization of electromagnetic radiation, cosmic rays and neutrinos.

    The inspiration to create 3ML came from Vianello’s own work with the Fermi gamma-ray space telescope. Fermi has two main instruments, the Gamma-Ray Burst Monitor and the Large Area Telescope (LAT), which is led by Michelson, professor and chair of physics at Stanford.

    NASA Fermi Gamma-ray Space Telescope Gamma-ray Burst Monitor (GBM)

    Even though these instruments exist on the same telescope, bringing their data together meant lengthy and cumbersome operations that often sacrificed some of the sensitivity of the LAT.

    The situation worsens when the data come from completely different experiments and collaborations.

    “It’s like completing a puzzle, where each instrument contributes a piece,” Michelson said. “However, the different pieces of the puzzle are very difficult and sometimes impossible to put together because they have different formats and require very different analysis methods and software.”

    Scientists at Fermi have used 3ML for studying gamma-ray bursts. The project has also grown, now including 15 collaborators from the United States and Europe.

    “Other missions and instruments have expressed the desire to join the effort and develop plug-ins for their data, so we’ve started working with them toward that,” Vianello said. “Some of them are even joining the development team, which is a very good thing because there is still a lot that can be done to improve 3ML.”

    Michelson said he believes that, as it continues to improve, the software could be particularly useful for studying faint sources across multiple wavelengths. It could even play a vital role in solving the mystery of the excess antimatter.

    “When completed, 3ML will, for the first time, allow for a powerful combination of Fermi, HAWC and other instruments for detailed analysis of extended sources, such as the one analyzed in the Science paper,” Michelson said.

    See the full article here .

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