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  • richardmitnick 1:51 pm on March 2, 2019 Permalink | Reply
    Tags: "Discovery of Many New Ultra-Diffuse Galaxies in Galaxy Clusters", , , , , Galaxies like our Milky Way can live in large groups with many others the so-called galaxy clusters, , KIWICS-The Kapteyn IAC WEAVE INT Clusters Survey, , Local Group   

    From Isaac Newton Group of Telescopes: “Discovery of Many New Ultra-Diffuse Galaxies in Galaxy Clusters” 

    Isaac Newton Group of Telescopes Logo
    From Isaac Newton Group of Telescopes

    In preparation for the new multi-object survey spectrograph, WEAVE, on the 4.2m William Herschel Telescope, the astronomical community is working on deep imaging surveys to identify the astronomical objects which will be studied later in more detail with WEAVE.

    WEAVE will allow astronomers to take optical spectra of up to ~1000 targets at the same time in a single exposure, or to carry out integral-field spectroscopy using 20 deployable mini integral-field units or one large integral-field unit.

    Galaxies, like our Milky Way, can live in large groups with many others, the so-called galaxy clusters.

    Milky Way NASA/JPL-Caltech /ESO R. Hurt

    Local Group. Andrew Z. Colvin 3 March 2011

    Laniakea supercluster. From Nature The Laniakea supercluster of galaxies R. Brent Tully, Hélène Courtois, Yehuda Hoffman & Daniel Pomarède at http://www.nature.com/nature/journal/v513/n7516/full/nature13674.html. Milky Way is the red dot.

    Such associations contain a potpourri of galaxies with many different properties such as colours, ages, morphologies and brightness. Among this broad diversity there exists a bewildering population of large but extremely faint galaxies, called “ultra diffuse galaxies” (see e.g., news release “The Puzzle of Ultra-Diffuse Galaxies”), and understanding their properties is important to understand how the environment of galaxies affects their evolution. Since they are so faint, they are easily perturbed by the cluster environment, and therefore are ideal probes to study what happens with galaxies in the dense cluster environment.

    Using the capabilities of the WFC at the Isaac Newton Telescope (INT) to explore large areas of the sky and detect faint ultra-diffuse galaxies (UDGs), a collaboration of astronomers in the Netherlands and Spain performed a study to investigate these galaxies in detail, the Kapteyn IAC WEAVE INT Clusters Survey (KIWICS).

    ING Wide Field Camera on the Isaac Newton Telescope

    2
    Figure 1. Map of the sky showing the clusters surveyed in KIWICS, and the eight clusters that have been already analysed. Credit: Pavel Mancera Piña.

    When finished, the KIWICS survey will contain 48 X-ray selected clusters. The results for 8 clusters have recently been published in the journal Monthly Notices of the Royal Astronomical Society, and Monthly Notices of the Royal Astronomical Society

    By analysing the general properties of about 500 newly-found UDGs at different distances from the centres of the clusters the researchers found several signs of environmental effects. The first result was that the larger clusters show a lack of UDGs in their centres. This is proof that the enormous gravitational forces present there are tearing these fluffy galaxies apart.

    Moreover they also found that UDGs away from the cluster centre are generally younger and have less concentrated stellar distributions, showing that the gravitational potential of the cluster, which is stronger close to the cluster centre, is changing the structure of galaxies, and is removing the interstellar gas, so that no new stars are being formed in the centres of clusters.

    In addition, they see that, as UDGs approach the centres of their host clusters, their morphologies are transformed from irregular discs to more spheroidal systems. In fact, for dwarf galaxies, which are similar to UDGs, but much smaller, observations in the literature give the same results.

    3
    Figure 2. Left panel: Example of UDGs found in different clusters, the white lines show a scale of 5 arcsec. Upper right panel: The Sérsic index distribution (a measure of the light concentration of a galaxy) for central (red) and outer (blue) UDGs, showing that the galaxies in the central regions are more concentrated. Lower right panel: Axis ratio distribution of the two samples, showing that galaxies in the central regions are rounder. Credit: Pavel Mancera Piña.

    It is expected that the whole KIWICS survey will be finished at the end of 2019, just before WEAVE will be installed on the William Herschel Telescope.

    See the full article here .

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    Isaac Newton Group of Telescopes located at Roque de los Muchachos Observatory on La Palma in the Canary Islands, Altitude 2,344 m (7,690 ft)

    Isaac Newton Group telescopes


    ING 4 meter William Herschel Telescope at Roque de los Muchachos Observatory on La Palma in the Canary Islands, 2,396 m (7,861 ft)


    ING Isaac Newton 2.5m telescope at Roque de los Muchachos Observatory on La Palma in the Canary Islands, Spain, Altitude 2,344 m (7,690 ft)

    ING Isaac Newton 2.5m telescope at Roque de los Muchachos Observatory on La Palma in the Canary Islands, Spain, Altitude 2,344 m (7,690 ft)

     
  • richardmitnick 1:53 pm on December 16, 2018 Permalink | Reply
    Tags: , , , , , Local Group, ,   

    From EarthSky: “What is the Local Group?” 

    1

    From EarthSky

    How many galaxies are now known to lie within our Local Group of galaxies? How does our Milky Way rank, size-wise? And what about the vast superclusters beyond?

    1
    One view of the Local Group- a bit to constricted.The 3 largest galaxies in the Local Group are, in descending order, Messier 31 the Andromeda galaxy, the Milky Way, and Messier 33 also known as the Triangulum Galaxy

    Iconic view of the Local Group. Andrew Z. Colvin 3 March 2011

    We know where our galaxy is located, but only locally speaking. The Milky Way galaxy is one of more than 54 galaxies known as the Local Group. The three largest members of the group are our Milky Way (second-biggest), the Andromeda galaxy (biggest) and the Triangulum Galaxy. The other galaxies in the Local Group are dwarf galaxies, and they’re mostly clustered around the three larger galaxies.

    The Local Group does have a gravitational center. It’s somewhere between the Milky Way and the Andromeda Galaxy.

    The Local Group has a diameter of about 10 million light-years.

    Astronomers have also discovered that our Local Group is on the outskirts of a giant supercluster of galaxies, known as the Virgo Supercluster.

    Virgo Supercluster NASA

    Virgo Supercluster, NASA, Wikipedia

    At least 100 galaxy groups and clusters are located within the Virgo Supercluster. Its diameter is thought to be about 110 million light-years.

    The Virgo Supercluster may be part of an even-larger structure that astronomers call the Laniakea Supercluster.

    Laniakea supercluster. From Nature The Laniakea supercluster of galaxies R. Brent Tully, Hélène Courtois, Yehuda Hoffman & Daniel Pomarède at http://www.nature.com/nature/journal/v513/n7516/full/nature13674.html. Milky Way is the red dot.

    It consists of perhaps 100,000 galaxies stretched out over some 520 million light-years.

    See the full article here .


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    Please help promote STEM in your local schools.

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    Deborah Byrd created the EarthSky radio series in 1991 and founded EarthSky.orgin 1994. Today, she serves as Editor-in-Chief of this website. She has won a galaxy of awards from the broadcasting and science communities, including having an asteroid named 3505 Byrd in her honor. A science communicator and educator since 1976, Byrd believes in science as a force for good in the world and a vital tool for the 21st century. “Being an EarthSky editor is like hosting a big global party for cool nature-lovers,” she says.

     
  • richardmitnick 10:25 am on December 11, 2017 Permalink | Reply
    Tags: Astronomers chart galaxy orbits in our Local Supercluster, , , , , , Local Group,   

    From EarthSky: “Astronomers chart galaxy orbits in our Local Supercluster” 

    1

    EarthSky

    December 10, 2017
    Deborah Byrd

    4
    In the [interactive in the full article, image above], you’ll notice the galaxies are moving toward something, a gravitational attractor represented by the big red dot more or less in the center of the mapped area (and in purple in the still graphic just above). This attractor is the Virgo Cluster, a large cluster of galaxies at the heart of the Virgo Supercluster (all located in the direction to the constellation Virgo in our sky; hence their names).

    Our home Milky Way galaxy (MW, yellow) and our companion Andromeda galaxy (M31, red) are participating in a downward flow away from a vast underdense region called the Local Void and toward the Virgo Cluster, represented by the large purple dot in this image. Most galaxies between us and the Virgo Cluster will eventually fall into the cluster but we lie slightly beyond the capture zone. Image via R. Brent Tully/ Institute for Astronomy, U Hawaii.

    “For the first time, we are not only visualizing the detailed structure of our Local Supercluster of galaxies, but we are also seeing how the structure developed over the history of the universe.”

    Look at the [above] graphic, for the yellow letters marked MW. Our Milky Way is part of what’s called the Local Group, which spans about 10 million light-years and contains several dozen galaxies. The Local Group, in turn, is part of the Virgo Supercluster, which spans just over 100 million light-years and is thought to contain at least 100 galaxy groups and clusters. [The work] is part of a study by a team of astronomers from Maryland, Hawaii, Israel, and France. They say it’s the most detailed map ever of the orbits of galaxies in our extended local neighborhood. It shows the past motions of some 1,400 galaxies within 100 million light-years of our Milky Way.

    Local Group. Andrew Z. Colvin 3 March 2011

    Virgo Supercluster, Wikipedia

    The Virgo Cluster alone – which is about 50 million light-years from us, or in the midst of the Virgo Supercluster’s 100 million light-years – has 600 trillion times the mass of our sun. These astronomers explained in their statement that the Virgo Cluster is pulling other galaxies toward itself, and absorbing them:

    Over a thousand galaxies have already fallen into the Virgo Cluster, while in the future all galaxies that are currently within 40 million light-years of the cluster will be captured. Our Milky Way galaxy lies just outside this capture zone. However the Milky Way and Andromeda galaxies, each with 2 trillion times the mass of the sun, are destined to collide and merge [with each other] in 5 billion years.

    3
    This series of photo illustrations shows the predicted merger between our Milky Way galaxy and the neighboring Andromeda galaxy. Via NASA; ESA; Z. Levay and R. van der Marel, STScI; T. Hallas, and A. Mellinger

    The study [The Astrophysical Journal] [is] based on the measurement of 18,000 galaxy distances. The astronomers’ statement explained the interactive this way:

    “With the interactive model [in the full aticle], a viewer can pan, zoom, rotate, and pause/activate the time evolution of movement along orbits. The orbits are shown in a reference frame that removes the overall expansion of the universe.”

    The lead author of this study is Ed Shaya of the University of Maryland in collaboration with Brent Tully of University of Hawaii, Yehuda Hoffman of Hebrew University in Israel, and Daniel Pomarede of University of Paris-Saclay in France. These scientists used what they said is a novel method for determining galaxy orbits, which they called numerical action. Brent Tully said:

    “For the first time, we are not only visualizing the detailed structure of our Local Supercluster of galaxies but we are seeing how the structure developed over the history of the universe. An analogy is the study of the current geography of the Earth from the movement of plate tectonics.”

    The astronomers’ statement also explained:

    “These dramatic merger events are only part of a larger show. There are two overarching flow patterns within this volume of the universe. All galaxies in one hemisphere of the region – including our own Milky Way – are streaming toward a single flat sheet. In addition, essentially every galaxy over the whole volume is flowing, as a leaf would in a river, toward gravitational attractors at far greater distances …”

    Representations of the orbits in the Virgo Supercluster can also be seen in the video [in the full article]:

    Bottom line: A team of astronomers has made the most detailed map ever of the orbits of galaxies in our local supercluster. It shows the past motions of some 1,400 galaxies within 100 million light-years of our Milky Way.

    See the full article here .

    Please help promote STEM in your local schools.

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    Stem Education Coalition

    Deborah Byrd created the EarthSky radio series in 1991 and founded EarthSky.org in 1994. Today, she serves as Editor-in-Chief of this website. She has won a galaxy of awards from the broadcasting and science communities, including having an asteroid named 3505 Byrd in her honor. A science communicator and educator since 1976, Byrd believes in science as a force for good in the world and a vital tool for the 21st century. “Being an EarthSky editor is like hosting a big global party for cool nature-lovers,” she says.

     
  • richardmitnick 2:14 pm on January 30, 2017 Permalink | Reply
    Tags: Cosmic Void “Pushes” Milky Way, Great Attractor, Local Group, ,   

    From Sky & Telescope: “Cosmic Void “Pushes” Milky Way” 

    SKY&Telescope bloc

    Sky & Telescope

    January 30, 2017
    Camille M. Carlisle

    Astronomers have discovered a giant cosmic void that explains why our Local Group of galaxies is moving through the universe as fast as it is.

    Local Group. Andrew Z. Colvin 3 March 2011
    Local Group. Andrew Z. Colvin 3 March 2011

    1
    This visualization is a slice of the local cosmic structure, roughly centered on the Local Group. The black arrows show the “flow” matter follows in this gravitational watershed. Analysis of these flow patterns has revealed that there’s probably a large, unseen void (gray-brown at right) that is “pushing” us toward the Shapley Supercluster (green), which is in turn gravitationally pulling us toward it. The yellow arrow is the direction of the so-called cosmic dipole.
    Yehuda Hoffman

    The Milky Way Galaxy is one of the biggest galaxies in the Local Group, a modest cluster of stellar metropolises. The Local Group, in turn, lies in a filament of the much larger cosmic structure. The galaxy clusters in this cosmic web don’t stay still, but rather slowly gravitate (literally) toward the largest clusters.

    Astronomers have known since the 1980s that the Local Group is moving toward what’s called the Great Attractor, a dense collection in the vicinity of the Centaurus, Norma, and Hydra clusters about 160 million light-years away. They’ve also found another, equally influential attractor called the Shapley Supercluster, a huge structure along roughly the same line of sight but four times farther away.

    In 2006, when Dale Kocevski and Harald Ebeling (both then of University of Hawai’i) confirmed Shapley’s influence on the Local Group by mapping out how clusters clump together on the sky, they also saw hints of a void in the opposite direction.

    Now, using the Cosmicflows-2 catalog of galaxies, Yehuda Hoffman (Hebrew University, Jerusalem) and colleagues have mapped out the movements of more than 8,000 galaxies and confirmed that, yes, the two titans that determine how local galaxies flow through the cosmic web are Shapley and this single, as-yet unmapped void.

    Think of the local cosmic structure as a gravitational water park: the twisty slides start high (where the void is) and end up low (where the cluster is), with the natural motion always being down — that is, with gravity. Galaxies toboggan along the gravitational slides.

    But how fast the galaxies go depends on how tall the slides are. In the same way, the fact that there’s a big, “high” void in one part of the gravitational landscape makes the Local Group flow faster toward the dense, “low-lying” regions in the other direction than it would otherwise. The net effect is as though the void is pushing in the same direction as the supercluster is pulling. It may even be that the void, which the team labels the dipole repeller in their January 30th Nature Astronomy paper, has more of an effect on the Local Group’s motion than the Shapley region does on its own.

    This discovery actually may solve a longstanding cosmic conundrum. Astronomers knew that the Local Group moves with respect to the cosmic microwave background (CMB), the ocean of photons suffusing the universe that is left over from the Big Bang. This motion is called the CMB dipole. But the velocity (630 km/s, or 1.4 million mph) was about double what it should be, if Shapley and the other clusters were responsible. The repeller’s effect essentially doubles Shapley’s pull, explaining why the Local Group moves as fast as it does.

    Below, you’ll find a movie explaining the result. Don’t mind the jargon: if it fazes you, the illustrations should carry you through. Credit: Yehuda Hoffman


    Access mp4 video here .

    See the full article here .

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    Sky & Telescope magazine, founded in 1941 by Charles A. Federer Jr. and Helen Spence Federer, has the largest, most experienced staff of any astronomy magazine in the world. Its editors are virtually all amateur or professional astronomers, and every one has built a telescope, written a book, done original research, developed a new product, or otherwise distinguished him or herself.

    Sky & Telescope magazine, now in its eighth decade, came about because of some happy accidents. Its earliest known ancestor was a four-page bulletin called The Amateur Astronomer, which was begun in 1929 by the Amateur Astronomers Association in New York City. Then, in 1935, the American Museum of Natural History opened its Hayden Planetarium and began to issue a monthly bulletin that became a full-size magazine called The Sky within a year. Under the editorship of Hans Christian Adamson, The Sky featured large illustrations and articles from astronomers all over the globe. It immediately absorbed The Amateur Astronomer.

    Despite initial success, by 1939 the planetarium found itself unable to continue financial support of The Sky. Charles A. Federer, who would become the dominant force behind Sky & Telescope, was then working as a lecturer at the planetarium. He was asked to take over publishing The Sky. Federer agreed and started an independent publishing corporation in New York.

    “Our first issue came out in January 1940,” he noted. “We dropped from 32 to 24 pages, used cheaper quality paper…but editorially we further defined the departments and tried to squeeze as much information as possible between the covers.” Federer was The Sky’s editor, and his wife, Helen, served as managing editor. In that January 1940 issue, they stated their goal: “We shall try to make the magazine meet the needs of amateur astronomy, so that amateur astronomers will come to regard it as essential to their pursuit, and professionals to consider it a worthwhile medium in which to bring their work before the public.”

     
  • richardmitnick 5:16 am on September 4, 2014 Permalink | Reply
    Tags: , , , , Local Group, Local Supercluster,   

    From SPACE.com: “New Galactic Supercluster Map Shows Milky Way’s ‘Heavenly’ Home “ 

    space-dot-com logo

    SPACE.com

    September 03, 2014
    Charles Q. Choi

    A new cosmic map is giving scientists an unprecedented look at the boundaries for the giant supercluster that is home to Earth’s own Milky Way galaxy and many others. Scientists even have a name for the colossal galactic group: Laniakea, Hawaiian for “immeasurable heaven.”

    The scientists responsible for the new 3D map suggest that the newfound Laniakea supercluster of galaxies may even be part of a still-larger structure they have not fully defined yet.

    “We live in something called ‘the cosmic web,’ where galaxies are connected in tendrils separated by giant voids,” said lead study author Brent Tully, an astronomer at the University of Hawaii at Honolulu.

    laniakea

    Scientists have created the first map of a colossal supercluster of galaxies known as Laniakea, the home of Earth’s Milky Way galaxy and many other. This computer simulation, a still from a Nature journal video, depicts the giant supercluster, with the Milky Way’s location shown as a red dot.

    super
    This computer-generated depiction of the Laniakea Supercluster of galaxies, which includes the Milky Way galaxy containing Earth’s solar system, shows a view of the supercluster as seen from the supergalactic equatorial plane.
    Credit: SDvision interactive visualization software by DP at CEA/Saclay, France Galactic structures in space

    Galaxies are not spread randomly throughout the universe. Instead, they clump in groups, such as the one Earth is in, the Local Group, which contains dozens of galaxies. In turn, these groups are part of massive clusters made up of hundreds of galaxies, all interconnected in a web of filaments in which galaxies are strung like pearls. The colossal structures known as superclusters form at the intersections of filaments.

    local

    The giant structures making up the universe often have unclear boundaries. To better define these structures, astronomers examined Cosmicflows-2, the largest-ever catalog of the motions of galaxies, reasoning that each galaxy belongs to the structure whose gravity is making it flow toward.

    “We have a new way of defining large-scale structures from the velocities of galaxies rather than just looking at their distribution in the sky,” Tully said.

    two
    Two views of the Laniakea Supercluster, a massive collection of galaxies that contains Earth’s Milky Way galaxy and many others, are shown in these computer-generated images.
    Credit: SDvision interactive visualization software by DP at CEA/Saclay, France

    The new 3D map developed by Tully and colleagues shows that the Milky Way galaxy resides in the outskirts of the Laniakea Supercluster, which is about 520 million light-years wide. The supercluster is made up of about 100,000 galaxies with a total mass about 100 million billion times that of the sun.

    The name Laniakea was suggested by Nawa’a Napoleon, who teaches Hawaiian language at Kapiolani Community College in Hawaii. The name is meant to honor Polynesian navigators who used their knowledge of the heavens to make long voyages across the immensity of the Pacific Ocean.

    “We live in the Local Group, which is part of the Local Sheet next to the Local Void — we wanted to come up with something a little more exciting than ‘Local,'” Tully told Space.com.

    This supercluster also includes the Virgo cluster and Norma-Hydra-Centaurus, otherwise known as the Great Attractor. These new findings help clear up the role of the Great Attractor, which is a problem that has kept astronomers busy for 30 years. Within the Laniakea Supercluster, the motions of galaxies are directed inward, as water flows in descending paths down a valley, and the Great Attractor acts like a large flat-bottomed gravitational valley with a sphere of attraction that extends across the Laniakea Supercluster.

    Universe map
    Panoramic view of the entire near-infrared sky reveals the distribution of galaxies beyond the Milky Way. The image is derived from the 2MASS Extended Source Catalog (XSC)—more than 1.5 million galaxies, and the Point Source Catalog (PSC)–nearly 0.5 billion Milky Way stars. The galaxies are color coded by redshift (numbers in parentheses) obtained from the UGC, CfA, Tully NBGC, LCRS, 2dF, 6dFGS, and SDSS surveys (and from various observations compiled by the NASA Extragalactic Database), or photo-metrically deduced from the K band (2.2 μm). Blue/purple are the nearest sources (z < 0.01); green are at moderate distances (0.01 < z < 0.04) and red are the most distant sources that 2MASS resolves (0.04 < z < 0.1). The map is projected with an equal area Aitoff in the Galactic system (Milky Way at center).
    2004
    Author IPAC/Caltech, by Thomas Jarrett

    Tully noted Laniakea could be part of an even larger structure.
    “We probably need to measure to another factor of three in distance to explain our local motion”, Tully said. “We might find that we have to come up with another name for something larger than we're a part of — we're entertaining that as a real possibility.”

    The scientists detailed their findings in the Sept. 4 issue of the journal Nature.

    See the full article here.

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