Citizen Scientists Probe Early Galaxies

New data collected by Galaxy Zoo show early galaxies with central bars, providing implications about how galaxies grow.

The NASA/ESA Hubble Space Telescope has taken a picture of the barred spiral galaxy NGC 1073, which is found in the constellation of Cetus (The Sea Monster). Our own galaxy, the Milky Way, is a similar barred spiral, and the study of galaxies such as NGC 1073 helps astronomers learn more about our celestial home. The Hubble Space Telescope is a project of international cooperation between ESA and NASA. NASA, ESA

The barred spiral galaxy NGC 1073, which is found in the constellation of Cetus (The Sea Monster).
NASA, ESA

The Hubble Space Telescope peers across the universe — imaging everything from the exquisite details of “nearby” galaxies millions of light-years away, to the blurry galaxies that formed only a few hundred million years after the Big Bang. Imaging the whole shebang allows astronomers to study the origin and evolution of galaxies, gaining insight into our own Milky Way Galaxy.

But many mysteries remain. Most spiral galaxies in the nearby universe, for example, have a bar in their center, with the spiral arms coming off it like streamers off the ends of a twirling baton. Although astronomers agree that these bars form when a galaxy passes from youth into adulthood, they disagree on the point in cosmic history at which this typically happens.

Now, astronomers using data collected by Galaxy Zoo — a crowd-sourced astronomy project that invites the public to analyze fuzzy images of distant galaxies — are peering deeper into the universe in search of these barred galaxies.

“Galaxy Zoo works because spotting features in galaxies is a task well suited to humans. We as a species are great at pattern recognition,” says project astronomer Brooke Simmons (Oxford, U.K.). “And you don't need to be an astrophysicist to recognize a boxy shape inside a rounded disk.”

The first disk galaxies were puffy and “hot,” with the gas and dust inside moving in highly turbulent ways. But gradually they “cooled” and the contents settled down, flattening into a thinner shape. At this point the thin disks grow magnificent spiral arms or barred features.

But astronomers remain unsure about when this settling occurs. Nearly 10 years ago astronomer Kartik Sheth (now at the National Radio Astronomy Observatory in Charlottesville, Virginia) found that the fraction of barred galaxies dropped from 50–70% in the nearby universe to 10% when the universe was only 6 billion years old. Further studies found roughly the same gradient.

So Simmons and her colleagues used Galaxy Zoo to probe even deeper. Extending the previous trend farther back in time, they expected the fraction of barred galaxies to drop to zero when the universe was 5 or 6 billion years old. Instead, they found that the number of barred galaxies when the universe was only 3 billion years old was still as high as 10%. The surprising results suggest that the young universe churned out bars relatively quickly.

Sheth worries about using volunteers’ eyes to determine the number of barred galaxies, instead of using statistical analyses. “Like Richard Dawkins says, we all see the patterns we want to,” he says. But he does agree that whatever the exact number, there are certainly some barred galaxies in the early universe, and this is unexpected.

These results are “new and fresh because no one really looks that hard,” says astronomer Bruce Elmegreen (IBM Corporation). These early barred galaxies might have formed either because they settled down earlier than expected, or because they were the result of two galaxies colliding.

Understanding the exact mechanisms that helped these galaxies grow their striking structures will shed light on how our own Milky Way became a starry behemoth with spiral arms and a central bar.

Reference:

B. D. Simmons et al. “Galaxy Zoo: CANDELS Barred Disks and Bar Fractions.” Monthly Notices of the Royal Astronomical Society, Accepted.


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3 thoughts on “Citizen Scientists Probe Early Galaxies

  1. adiom111@gmail.com

    Hi!
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    (An abridged version)

    Contents of a Book

    The Introduction
    The Prologue

    Part I. A Cosmic Intelligent Being’s Fundamental Rights

    I.1. About A Cosmic Intelligent Being’s Inalienable Fundamental Rights
    I.2. Political, Civil and Individual Rights’ Articles
    I.3. The Intercivilizational Magna Carta of a Cosmic Intelligent Being’s Rights and Freedoms
    I.4. «The Elite Races»
    I.5. Rights of Plants and Minerals
    I.6. The Eternal Transmigration

    Part II. About Cosmic Planetary Races and Planetary Communities of Living Beings’ Some Principal Rights

    II.1. The Cosmic Life Hierolevels
    II.2. On Cosmic Races Certain Inalienable Fundamental Freedoms and Rights
    II.3. The Introduction to the Declaration of Independence or about an Independent Cosmic Race

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    III.1. The Missions of the UCO or the United Civilizations Organization
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  2. Edward Schaefer

    Here is an alternate view of what is being seen in that above picture: The later stages of a galaxy merger.

    Look for instance at the central area of the Antenna galaxies (http://hubblesite.org/gallery/album/entire/pr2006046a/large_web/). There is a bridge of gas and dust connecting the centers of the galaxies. This is not a tidal tail: Look carefully and you can see the smaller counterparts to the large tidal tails that make the “antennae”. I believe that this type of structure forms for all interacting galaxies. When the galaxies are passing quickly, this structure will stretch out and break. (See http://apod.nasa.gov/apod/ap100702.html.)

    However, if the galactic centers come close enough and are slow enough, the bridge builds up into a gravitationally significant entity in its own right. Once that happens, it can affect the central objects, pulling them in towards the center of the bridge. Their moving towards the center of course reinforces the bridge which pulls them together even more. So in a fairly short period of time, you end up with a structure like NGC 1073 above.

    The arm start at the ends of the bar, and go clockwise. They are weak until you get 70 degrees around, at which point they get much stronger and branch. I believe that this first part of the each arm is the remains of the central parts of the original galaxies. Then at the branch you get a stronger spiral arm which is closer to the center and a weaker one which is further away. I believe that the stronger arms are the remains of each of the original galaxies stretched out by the tides created as their centers headed down the bridge and merged. The weaker arms are the original tidal tails created at the start of the interaction. Structure in the spiral arms is from the stretched out remains of the spiral arms in the original galaxies.

    After this, it seems that the spiral arms will wind up and the bar will contract until you get a grand design spiral. One upshot of this is that the Milky Way must have undergone a fairly recent merger given that it has a bar. This can also explain why Andromeda has two central objects, although what allowed them to stay separate is a good question.

    The connecting bridge is a structure that the current models of galaxy mergers to not have. Another article show one proposed way that a galaxy merger can produce a spiral (http://www.skyandtelescope.com/astronomy-news/mergers-create-disk-galaxies-10022014/), but in that model you get just one spiral arm instead of two branching ones. So look at other spiral galaxies. In general, you should find two main spiral arms and two lesser arm in between them. The Milky Way has this structure: See http://www.eso.org/public/images/eso1339e/. Another example is the central regions of the Whirlpool galaxy: See http://hubblesite.org/newscenter/archive/releases/2005/12/image/a/format/large_web/.

    So in my view, galactic mergers created barred spiral galaxies that eventually settle down into grand design spiral galaxies. Exactly how this happens is yet to be modeled. For now what is needed are pictures of galaxies in the intermediate stages of the pulling together of the central objects. That will tell us much, including how galaxy merger models should look.

  3. Bijay_Kumar-SharmaBijay_Kumar-Sharma

    In my opinion, all galaxies, clusters and superclusters have a Monarch.
    Galaxies have Supermassive Black Hole at the center,
    Clusters have QUASERS at the center of the cluster and as the Monarch and
    Superclusters have a Great Attractor at the center as has been found in our case i.e. Milky Way.
    These Monarchs through tidal interaction influence the evolution of their host system.
    In this light, a comprehensive model can be developed which will explain the different stages of the Galaxies.

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