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  • richardmitnick 2:24 pm on December 12, 2017 Permalink | Reply
    Tags: Astrobites, , , , , Exploding stars and sleight of hand: A case of magnetic misdirection   

    From astrobites: “Exploding stars and sleight of hand: A case of magnetic misdirection” 

    Astrobites bloc

    astrobites

    Title: When Disorder Looks Like Order: A New Model to Explain Radial Magnetic Fields in Young Supernova Remnants
    Authors: J. L. West, T. Jaffe, G. Ferrand, S. Safi-Harb, and B. M. Gaensler
    First Author’s Institution: Dunlap Institute for Astronomy and Astrophysics at the University of Toronto, Canada

    Status: Published in The Astrophysical Journal Letters, open access on arXiv

    In the roiling outer layers of exploding stars, electrons are accelerated to near light speed. These relativistic electrons have a habit of causing glitches in orbiting spacecraft and sparking showers of secondary particles. Striking the retinae of in-orbit astronauts, they generate flashes of phantom light.

    How do these electrons reach their enormously high velocities? The exact mechanism isn’t known, but it’s thought to depend upon the magnetic fields threaded throughout the expanding shells of young supernova remnants. Curiously, as shown in Figure 1, many young supernova remnants appear to have well-ordered radial magnetic fields, pointing neatly away from or toward the center of the explosion. While it’s not impossible for the magnetic field to be orderly, it’s reasonable to expect that the explosion of a dying star, which creates swirling knots and curlicues of hot plasma, would impart some turbulence and randomness to its magnetic field. Could the neat, radial pattern that we observe belie the true, messy magnetic field? If so, how can we tell?

    1
    Figure 3. Simulated polarized intensity (color scale) and simulated magnetic field orientations (black lines) for a turbulent intrinsic field and three different acceleration mechanisms. Although the isotropic electron acceleration mechanism (left) yields an apparently random magnetic field, the quasi-parallel (center) and quasi-perpendicular (right) acceleration mechanisms generate apparently ordered magnetic fields. Adapted from Figure 4 in the paper.

    See the full article here .

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    What do we do?

    Astrobites is a daily astrophysical literature journal written by graduate students in astronomy. Our goal is to present one interesting paper per day in a brief format that is accessible to undergraduate students in the physical sciences who are interested in active research.
    Why read Astrobites?

    Reading a technical paper from an unfamiliar subfield is intimidating. It may not be obvious how the techniques used by the researchers really work or what role the new research plays in answering the bigger questions motivating that field, not to mention the obscure jargon! For most people, it takes years for scientific papers to become meaningful.
    Our goal is to solve this problem, one paper at a time. In 5 minutes a day reading Astrobites, you should not only learn about one interesting piece of current work, but also get a peek at the broader picture of research in a new area of astronomy.

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  • richardmitnick 12:02 pm on December 11, 2017 Permalink | Reply
    Tags: Astrobites, , , , , Flux tubes   

    From astrobites: “Flux Tube Bundles in Neutron Star Super-Mixture” 

    Astrobites bloc

    astrobites

    Dec 11, 2017
    Lisa Drummond

    Title: Flux tubes and the type-I/type-II transition in a superconductor coupled to a superfluid
    Authors: Mark G. Alford, Gerald Good

    Status: Published Phys. Rev. B, open access

    Physicists are fascinated by neutron stars because their dense interior acts as a laboratory for exotic materials beyond what we find on Earth. Today’s paper suggests that flux tubes, which are quantum objects that exist in superconductors, could form bundles inside a neutron star – this unusual behaviour challenges the standard picture we have of terrestrial superconductors.

    1
    Figure 1. Interior structure of a neutron star. In particular, observe the superfluid-superconductor mixture in the core of the star. Image taken from http://slideplayer.com/slide/4522702/

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    What do we do?

    Astrobites is a daily astrophysical literature journal written by graduate students in astronomy. Our goal is to present one interesting paper per day in a brief format that is accessible to undergraduate students in the physical sciences who are interested in active research.
    Why read Astrobites?

    Reading a technical paper from an unfamiliar subfield is intimidating. It may not be obvious how the techniques used by the researchers really work or what role the new research plays in answering the bigger questions motivating that field, not to mention the obscure jargon! For most people, it takes years for scientific papers to become meaningful.
    Our goal is to solve this problem, one paper at a time. In 5 minutes a day reading Astrobites, you should not only learn about one interesting piece of current work, but also get a peek at the broader picture of research in a new area of astronomy.

     
  • richardmitnick 12:06 pm on December 8, 2017 Permalink | Reply
    Tags: Astrobites, , , , , Paperscape   

    From astrobites: “A Map of Astronomy” 

    Astrobites bloc

    astrobites

    Title: Paperscape
    Authors: Damien George and Rob Knegjens
    First author’s institution: Department of Applied Mathematics and Theoretical Physics, University of Cambridge, UK

    Status: Website with accompanying explanatory blog post [open access]

    The nice thing about studying the Kepler exoplanets, as I do, is that they’re more or less all in one place. Sometimes I go outside and look up at them, or, more accurately, the place I know them to be: all 5000 or so, spilling off the edge of the Summer Triangle. The source of most of our knowledge of worlds beyond the solar system is neatly contained in that tiny patch of sky. Seeing it all at once makes me feel like someday I might understand it. (An added bonus is that if my research is going poorly, I can hold up my hand and pretend it’s not there.)

    Today’s bite is for those of you who, like me, like to see everything all in one place. It’s not a paper this time–rather, it’s a map of papers, everything written and published on the arXiv since its founding in 1991. Behold: physics.

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    Figure 1. The arXiv landscape. Astronomy (pink, upper right) drifts in the vast sea of the unknown, among the continents of other physics sub-fields, beset by sea monsters that I in no way photoshopped in.

    See the full article here .

    Please help promote STEM in your local schools.

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    What do we do?

    Astrobites is a daily astrophysical literature journal written by graduate students in astronomy. Our goal is to present one interesting paper per day in a brief format that is accessible to undergraduate students in the physical sciences who are interested in active research.
    Why read Astrobites?

    Reading a technical paper from an unfamiliar subfield is intimidating. It may not be obvious how the techniques used by the researchers really work or what role the new research plays in answering the bigger questions motivating that field, not to mention the obscure jargon! For most people, it takes years for scientific papers to become meaningful.
    Our goal is to solve this problem, one paper at a time. In 5 minutes a day reading Astrobites, you should not only learn about one interesting piece of current work, but also get a peek at the broader picture of research in a new area of astronomy.

     
  • richardmitnick 3:09 pm on December 5, 2017 Permalink | Reply
    Tags: , Astrobites, , , , ,   

    From astrobites : “Planet Frequencies in the Galactic Bulge” 

    Astrobites bloc

    astrobites

    5 December 2017
    Elisabeth Matthews

    1
    Artist’s impression of an icy exoplanet found via gravitational microlensing. [ESO]

    Title: Towards a Galactic Distribution of Planets. I: Methodology & Planet Sensitivities of the 2015 High-Cadence Spitzer Microlens Sample
    Authors: Wei Zhu, A. Udalski, S. Calchi Novati et al.
    First Author’s Institution: Ohio State University

    Status: Published in ApJ

    I don’t know if you’ve heard, but astronomers have found quite a few exoplanets in the last couple of decades. However, most of these are clustered in our tiny corner of the galaxy. For the 2,043 planets with stellar distance listed on exoplanets.org today (yes, I know this article will be out of date in a week…) the average distance from to the host star from Earth is 624 pc. The center of the galaxy, meanwhile, is ~8,000 pc away. That’s further than even the furthest known exoplanet, OGLE-05-390L b, which is 6,500 pc from us.

    And we’d really like to have a better understanding of the exoplanets in the galactic bulge, because their presence — or lack thereof — helps us to understand planet formation. Planet formation is believed to be affected by several external factors such as the host star’s metallicity, the stellar mass, the stellar multiplicity, and the stellar environment. That final category is what we’re going to consider today: does the presence of a large number of nearby stars interrupt the formation of planets? The galactic bulge, as the part of the galaxy with the highest number density of stars, is an ideal place to test this — if only we could detect enough planets out there…


    1.3 meter OGLE Warsaw Telescope at the Las Campanas Observatory in Chile, over 2,500 m (8,200 ft) high,

    Any readers particularly clued-up on exoplanet surveys might have recognised the phrase ‘OGLE’ in the name of planet ‘OGLE-05-390L b’. OGLE is the Optical Gravitational Lensing Experiment, a microlensing project run by Warsaw University. Although the mission was initially designed for dark-matter surveys, it has also made several serendipitous exoplanet discoveries. This astrobite describes microlensing for exoplanet detection in more detail, but for today all we really need to know is that sometimes nearby stars and distant stars happen to be really well aligned on the sky for a short time.

    Gravitational microlensing, S. Liebes, Physical Review B, 133 (1964): 835

    See the full article here .

    Please help promote STEM in your local schools.

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    What do we do?

    Astrobites is a daily astrophysical literature journal written by graduate students in astronomy. Our goal is to present one interesting paper per day in a brief format that is accessible to undergraduate students in the physical sciences who are interested in active research.
    Why read Astrobites?

    Reading a technical paper from an unfamiliar subfield is intimidating. It may not be obvious how the techniques used by the researchers really work or what role the new research plays in answering the bigger questions motivating that field, not to mention the obscure jargon! For most people, it takes years for scientific papers to become meaningful.
    Our goal is to solve this problem, one paper at a time. In 5 minutes a day reading Astrobites, you should not only learn about one interesting piece of current work, but also get a peek at the broader picture of research in a new area of astronomy.

     
  • richardmitnick 12:35 pm on November 30, 2017 Permalink | Reply
    Tags: Astrobites, , , , , , Red clump (RC) stars   

    From astrobites: “Gaia and the Red Clump” 

    Astrobites bloc

    astrobites

    Nov 30, 2017
    Philipp Plewa

    Title: Red clump stars and Gaia: Calibration of the standard candle using a hierarchical probabilistic model
    Authors: K. Hawkins, B. Leistedt, J. Bovy, D. W. Hogg
    First Author’s Institution: Department of Astronomy, Columbia University, New York
    1
    Status: Published in MNRAS, open access

    Red clump (RC) stars are common stars, once similar to the sun, that have evolved into red giants now supported by helium fusion in their cores. Independent of their exact age or composition, all RC stars end up having about the same absolute luminosity. This is why they tend to “clump” in a particular spot in a color-magnitude or Hertzsprung–Russell diagram, and what makes them standard candles: The apparent brightness of RC stars is directly related to their distance.

    2
    Red clump stars and Gaia, MNRAS
    3
    Hertzsprung-Russell diagram. A plot of luminosity (absolute magnitude) against the colour of the stars ranging from the high-temperature blue-white stars on the left side of the diagram to the low temperature red stars on the right side. “This diagram below is a plot of 22000 stars from the Hipparcos Catalogue together with 1000 low-luminosity stars (red and white dwarfs) from the Gliese Catalogue of Nearby Stars. The ordinary hydrogen-burning dwarf stars like the Sun are found in a band running from top-left to bottom-right called the Main Sequence. Giant stars form their own clump on the upper-right side of the diagram. Above them lie the much rarer bright giants and supergiants. At the lower-left is the band of white dwarfs – these are the dead cores of old stars which have no internal energy source and over billions of years slowly cool down towards the bottom-right of the diagram.”

    Next year’s second Gaia data release is expected to provide a significantly larger sample of RC reference stars.

    ESA/GAIA satellite

    In particular, this will allow a closer study of the impact of such effects as stellar age and metallicity, helium abundance, or binarity on the RC distance calibration, and thus make RC stars even better standard candles.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    What do we do?

    Astrobites is a daily astrophysical literature journal written by graduate students in astronomy. Our goal is to present one interesting paper per day in a brief format that is accessible to undergraduate students in the physical sciences who are interested in active research.
    Why read Astrobites?

    Reading a technical paper from an unfamiliar subfield is intimidating. It may not be obvious how the techniques used by the researchers really work or what role the new research plays in answering the bigger questions motivating that field, not to mention the obscure jargon! For most people, it takes years for scientific papers to become meaningful.
    Our goal is to solve this problem, one paper at a time. In 5 minutes a day reading Astrobites, you should not only learn about one interesting piece of current work, but also get a peek at the broader picture of research in a new area of astronomy.

     
  • richardmitnick 8:42 am on November 28, 2017 Permalink | Reply
    Tags: All-sky spectroscopy with SDSS-V, Astrobites, , , ,   

    From astrobites: “All-sky spectroscopy with SDSS-V” 

    Astrobites bloc

    astrobites

    Title: SDSS V: Pioneering Panoptic Spectroscopy
    Authors: Juna A. Kollmeier, Gail Zasowski, Hans-Walter Rix, et al.
    First Author’s Institution: Carnegie Institution for Science, Washington, DC

    Status: submitted to arXiv, open access

    “Our human eyes are the tools that peek at the secrets of the night sky”, so said the ancient Chinese astronomers who witnessed the supernova of the Crab Nebula in 1054 AD. But the heavens only truly light up through the lenses of telescopes, allowing us not only to peer into, but also to peel away, the mysteries of our Universe. We started out in 1609 with Galileo’s 37 mm refracting telescope, proceeded to Newton’s 150 mm reflecting telescope in 1668, and leapfrogged to William Herschel’s 49 inch (125 cm) reflector in 1789, which held the record as the world’s largest telescope for the next 50 years. Two hundred years later, not only do we have artificial eyes in space constantly staring deeper into the infancy of the Universe, we also have all sky maps in various wavelengths of light and larger telescopes from the ground, with bigger and more ambitious programs already lined up for the next five to ten years. As an astronomer in training, I never fail to be amazed by the giant leaps we have made over the course of human history.

    Even so, we are still only scratching the surface.

    Astronomers are not strangers to sky surveys. Among the tens of sky surveys, the Sloan Digital Sky Survey (SDSS) is probably the king of them all, having been in operation since 2000, with WISE and ROSAT chasing its tail for being truly all-sky.

    SDSS Telescope at Apache Point Observatory, NM, USA, Altitude 2,788 meters (9,147 ft)

    NASA/WISE Telescope

    DLR/NASA ROSAT satellite

    However, all surveys to date, both full- and partial-sky, have been imaging surveys. There is no yet a full-sky spectroscopic survey — at least not until SDSS-V.

    2
    Figure 1: A schematic of SDSS-V, an all-sky spectroscopic survey. The main science programs are the Milky Way Mapper, the Black Hole Mapper, and the Local Volume Mapper. Observations will be carried out in both hemispheres using telescopes at the Apache Point and Las Campanas Observatories. [Figure 1 in paper]

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    What do we do?

    Astrobites is a daily astrophysical literature journal written by graduate students in astronomy. Our goal is to present one interesting paper per day in a brief format that is accessible to undergraduate students in the physical sciences who are interested in active research.
    Why read Astrobites?

    Reading a technical paper from an unfamiliar subfield is intimidating. It may not be obvious how the techniques used by the researchers really work or what role the new research plays in answering the bigger questions motivating that field, not to mention the obscure jargon! For most people, it takes years for scientific papers to become meaningful.
    Our goal is to solve this problem, one paper at a time. In 5 minutes a day reading Astrobites, you should not only learn about one interesting piece of current work, but also get a peek at the broader picture of research in a new area of astronomy.

     
  • richardmitnick 6:59 pm on November 27, 2017 Permalink | Reply
    Tags: Astrobites, , , , , Extinction events from giant space explosions: a cosmological perspective,   

    From astrobites: “Extinction events from giant space explosions: a cosmological perspective” 

    Astrobites bloc

    astrobites

    Nov 27, 2017
    Christopher Lovell

    Title: Exploring the Cosmic Evolution of Habitability with Galaxy Merger Trees
    Authors: E. R. Stanway, M. J. Hoskin, M. A. Lane, G. C. Brown, H. J. T. Childs, S. M. L. Greis and A. J. Levan
    First Author’s Institution: University of Warwick

    Status: Submitted to MNRAS, Open Access

    We’re still unsure how life began, but we have plenty of ideas for how to snuff it out completely. From global warming to an asteroid collision, rogue AI to a supervolcano explosion, we have a morbid ability to imagine our own demise (and dramatic rescue, if you have a Bruce Willis with a thermonuclear weapon). But the cosmos has far more powerful means of sterilising planets beyond the solar system, and depending on how common they are, the chances of life lasting elsewhere in the cosmos could be slim indeed.

    1
    Figure 1: Illustration of a Gamma Ray Burst (GRB). Most of the energy is emitted along the jet axis. Courtesy of the Chandra X-ray Observatory.

    NASA/Chandra Telescope

    Explosions in the sky

    Massive stars end their lives in massive explosions known as a supernovae (SNe), and if they are rotating rapidly enough can lead to gamma ray bursts (GRBs). GRBs can also occur during the collision of two neutron stars. Both SNe and GRBs release massive amounts of hard, ionising radiation that can dissociate complex molecules, or strip the atmosphere of a planet completely, killing any complex life on the surface. Such extinction events are not purely hypothetical – at least one mass extinction event in the history of life on Earth, in the late Ordivician period, has been attributed to a GRB. The supermassive black holes at the center of every galaxy can also release huge amounts of radiation when they’re accreting matter (hence the name, Active Galactic Nuclei, or AGN), which can irradiate any nearby stellar system in a similar way to a SNe or GRB.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    What do we do?

    Astrobites is a daily astrophysical literature journal written by graduate students in astronomy. Our goal is to present one interesting paper per day in a brief format that is accessible to undergraduate students in the physical sciences who are interested in active research.
    Why read Astrobites?

    Reading a technical paper from an unfamiliar subfield is intimidating. It may not be obvious how the techniques used by the researchers really work or what role the new research plays in answering the bigger questions motivating that field, not to mention the obscure jargon! For most people, it takes years for scientific papers to become meaningful.
    Our goal is to solve this problem, one paper at a time. In 5 minutes a day reading Astrobites, you should not only learn about one interesting piece of current work, but also get a peek at the broader picture of research in a new area of astronomy.

     
  • richardmitnick 6:49 pm on November 24, 2017 Permalink | Reply
    Tags: Astrobites, , , ,   

    From astrobites: “How many stars have companions?” 

    Astrobites bloc

    astrobites

    Nov 23, 2017
    Ingrid Pelisoli

    SDSS APOGEE spectrograph

    SDSS Telescope at Apache Point Observatory, NM, USA, Altitude 2,788 meters (9,147 ft)

    3

    Title: Stellar Multiplicity Meets Stellar Evolution And Metallicity: The APOGEE View
    Authors: Carles Badenes, Christine Mazzola, Todd A. Thompson et al.
    First Author’s Institution: Department of Physics and Astronomy and Pittsburgh Particle Physics, Astrophysics and Cosmology Center (PITT PACC), University of Pittsburgh, USA
    1
    Status: Submitted to to AAS journals [open access]

    Have you ever tried to count the stars in the sky? I remember doing that as a kid, and always giving up even before I got to a hundred. Little did I know that I would never get the right number. As we’ve talked before here on Astrobites, one plus one is not always two when it comes to stars. The process of stellar formation occurs in dense molecular clouds, where many stars form at the same time. As a result, many of them end up in multiple systems (binaries, ternary, etc.). But how many?

    This may seem like a naive question, but it has implications in different fields of astronomy. Multiple systems host many interesting astronomical sources, such as X-ray binaries and cataclysmic variables. Interacting binaries are progenitors of Type Ia supernovae, which ultimately led us to infer that the Universe was expanding at an increasing rate. Moreover, they are sources of gravitational waves. Therefore we have plenty of reasons to ask how many stars have companions, and that’s exactly what the authors of today’s paper did.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    What do we do?

    Astrobites is a daily astrophysical literature journal written by graduate students in astronomy. Our goal is to present one interesting paper per day in a brief format that is accessible to undergraduate students in the physical sciences who are interested in active research.
    Why read Astrobites?

    Reading a technical paper from an unfamiliar subfield is intimidating. It may not be obvious how the techniques used by the researchers really work or what role the new research plays in answering the bigger questions motivating that field, not to mention the obscure jargon! For most people, it takes years for scientific papers to become meaningful.
    Our goal is to solve this problem, one paper at a time. In 5 minutes a day reading Astrobites, you should not only learn about one interesting piece of current work, but also get a peek at the broader picture of research in a new area of astronomy.

     
  • richardmitnick 8:38 pm on November 22, 2017 Permalink | Reply
    Tags: Astrobites, , , , , No Missing Satellites?   

    From astrobites: “No Missing Satellites?” 

    Astrobites bloc

    astrobites

    Nov 22, 2017
    Gourav Khullar

    Title: There is no missing satellites problem
    Authors: S.Y. Kim, A.G.H. Peters, and J.R. Hargis
    First Author’s Institution: Dept. of Astronomy, The Ohio State University, USA

    Status: Submitted to The Astrophysical Journal Letters (ApJL) (open source)

    Dark Matter : Structure in the Universe

    It can be said with tremendous confidence that the Lambda Cold Dark Matter (LCDM) model of the universe is doing a fantastic job so far as THE model of the universe that explains most of its phenomena – the cosmic microwave background [CMB], the formation and evolution of objects in the universe, cosmic accelerated expansion, the evolution of various particle species, and even gravitational waves!

    Lambda-Cold Dark Matter, Accelerated Expansion of the Universe, Big Bang-Inflation (timeline of the universe) Date 2010 Credit: Alex MittelmannColdcreation

    CMB per ESA/Planck

    Gravitational waves. Credit: MPI for Gravitational Physics/Werner Benger

    Both simulations and observations that incorporate LCDM to make predictions have been consistent with each other. That being said, there are a few areas in the field of astrophysics where LCDM is falling a little short of convincing; this is a cause for worry.

    Structure formation has been an exciting field for the past few decades, keeping astrophysicists busy with the mysteries of how objects like galaxies and galaxy clusters evolve from the primordial perturbations in the universe. Simulations of large-scale structure from the early universe to now (e.g. Bolshoi, Millenium, Illustris), and large sky surveys that observe billions of objects (e.g. SDSS, DES), indicate the presence of massive dark matter halos whose gravitational potential wells attract matter to form galaxies and eventually galaxy clusters.

    SDSS Telescope at Apache Point Observatory, NM, USA, Altitude 2,788 meters (9,147 ft)


    Universe map Sloan Digital Sky Survey (SDSS) 2dF Galaxy Redshift Survey

    Dark Energy Survey


    Dark Energy Camera [DECam], built at FNAL


    NOAO/CTIO Victor M Blanco 4m Telescope which houses the DECam at Cerro Tololo, Chile, housing DECam at an altitude of 7200 feet

    Moreover, natural product of this is the presence of low mass and low brightness dwarf galaxies on the peripheries of larger galaxies, known as satellites. These are galaxies that are influenced by the gravitational potential of their host galaxies, but are stable astrophysical entities in themselves. The above described paradigm and its products are the centerpiece of an ongoing debate (one of the major LCDM issues), called the ‘Missing Satellites Problem’.

    3
    Figure 1. Dwarf/Satellite galaxies seen in (left) a simulation with a Milky Way sized halo, and (right) observations of the Milky Way from sky surveys. The circles on the left are the highest mass satellite halos seen in simulations, and there are far too many similar-sized halos in the simulation than in observations. This is the MSP (From Weinberg et al. 2013).

    What is the problem?

    The ‘Missing Satellites Problem’ (MSP) is the discrepancy between the number of satellite galaxies seen when a Milky-Way type galaxy is simulated, and the dwarf galaxies observed around our own Milky Way – we aren’t seeing enough satellites around us. A Milky Way type galaxy is made of 10^10.5 Msolar worth of stars, 10^11 Msolar worth of gas, and 10^11.5 Msolar worth of a dark matter halo that contain the Milky Way and its satellite dwarf galaxies. While we are still in the process of discovering faint dwarf galaxies, astrophysicists wonder if there are indeed enough satellites to confirm simulation predictions.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    What do we do?

    Astrobites is a daily astrophysical literature journal written by graduate students in astronomy. Our goal is to present one interesting paper per day in a brief format that is accessible to undergraduate students in the physical sciences who are interested in active research.
    Why read Astrobites?

    Reading a technical paper from an unfamiliar subfield is intimidating. It may not be obvious how the techniques used by the researchers really work or what role the new research plays in answering the bigger questions motivating that field, not to mention the obscure jargon! For most people, it takes years for scientific papers to become meaningful.
    Our goal is to solve this problem, one paper at a time. In 5 minutes a day reading Astrobites, you should not only learn about one interesting piece of current work, but also get a peek at the broader picture of research in a new area of astronomy.

     
  • richardmitnick 4:23 pm on November 21, 2017 Permalink | Reply
    Tags: Astrobites, , , , , What were globular clusters doing during reionization?   

    From astrobites: “What were globular clusters doing during reionization?” 

    Astrobites bloc

    astrobites

    Nov 21, 2017
    Joshua Kerrigan

    Title: The Little Engines That Could? Globular Clusters Contribute Significantly to Reionization-era Star Formation
    Authors: Michael Boylan-Kolchin
    First Author’s Institution: Dept. of Astronomy, The University of Texas at Austin, Austin, TX

    Status: Submitted to MNRAS, open access

    1
    The Messier 80 globular cluster in the constellation Scorpius is located about 30,000 light-years from the Sun and contains hundreds of thousands of stars

    In the past we’ve covered a few potential sources for the reionization of the universe, such as AGN or supernovae. It is believed that the primary contributor of UV radiation during reionization was from the earliest formed galaxies (think redshift z ~ 12). Therefore it can be really informative to understand how these galaxies are producing their UV flux. So for today’s astrobite we look into what ancient globular clusters were doing during the epoch of reionization (z ~ 6-10).

    What are globular clusters?

    To understand how globular clusters (GCs) can contribute to reionization, we need to understand some background about them. Globular clusters are gravitationally tightly-bound, spherical, ex-star-forming regions within galaxies. These very dense stellar clusters orbit fairly close to the galactic center, and usually contain some of the earliest formed stars in that galaxy. This means that in the early stages of galaxy formation globular clusters should have contributed a sizable amount to the high redshift UV luminosity output.

    Learning from the GC luminosity function

    Now we have a basic idea of what GCs are, but how can we use this knowledge to predict how important they were during reionization? By using the GC UV luminosity function of course! The GC UV luminosity function (or GC UVLF) gives the number of GCs per volume per luminosity and this function evolves with redshift. They use the UV luminosity function in particular because the majority of photons that re-ionize neutral hydrogen will have UV wavelengths.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    What do we do?

    Astrobites is a daily astrophysical literature journal written by graduate students in astronomy. Our goal is to present one interesting paper per day in a brief format that is accessible to undergraduate students in the physical sciences who are interested in active research.
    Why read Astrobites?

    Reading a technical paper from an unfamiliar subfield is intimidating. It may not be obvious how the techniques used by the researchers really work or what role the new research plays in answering the bigger questions motivating that field, not to mention the obscure jargon! For most people, it takes years for scientific papers to become meaningful.
    Our goal is to solve this problem, one paper at a time. In 5 minutes a day reading Astrobites, you should not only learn about one interesting piece of current work, but also get a peek at the broader picture of research in a new area of astronomy.

     
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