Galaxy Zoo Talk

CANDELS Visual Classifications: Scheme, Data Release, and First Results - makes GZ CANDELS irrelevant?

  • JeanTate by JeanTate

    "CANDELS Visual Classifications: Scheme, Data Release, and First Results" is the title of arXiv:1401.2455 (link is to the abstract), an astro-ph preprint posted on 10 Jan, 2014. The lead author is Jeyhan S. Kartaltepe.

    Here's the abstract:

    We have undertaken an ambitious program to visually classify all galaxies in the five CANDELS fields down to H<24.5 involving the dedicated efforts of 65 individual classifiers. Once completed, we expect to have detailed morphological classifications for over 50,000 galaxies up to z<4 over all the fields. Here, we present our detailed visual classification scheme, which was designed to cover a wide range of CANDELS science goals. This scheme includes the basic Hubble sequence types, but also includes a detailed look at mergers and interactions, the clumpiness of galaxies, k-corrections, and a variety of other structural properties. In this paper, we focus on the first field to be completed -- GOODS-S. The wide area coverage spanning the full field includes 7634 galaxies that have been classified by at least three different people. In the deep area of the field, 2534 galaxies have been classified by at least five different people at three different depths. With this paper, we release to the public all of the visual classifications in GOODS-S along with the GUI that we developed to classify galaxies. We find that the level of agreement among classifiers is good and depends on both the galaxy magnitude and the galaxy type, with disks showing the highest level of agreement and irregulars the lowest. A comparison of our classifications with the Sersic index and rest-frame colors shows a clear separation between disk and spheroid populations. Finally, we explore morphological k-corrections between the V-band and H-band observations and find that a small fraction (84 galaxies in total) are classified as being very different between these two bands. These galaxies typically have very clumpy and extended morphology or are very faint in the V-band.

    At first read, it seems that the classifications being done here, in this part of Galaxy Zoo, will be irrelevant (or at least relatively marginal), unless GZ:CANDELS is published in the next month or so.

    What do you think?

    Posted

  • vrooje by vrooje admin, scientist

    Hi Jean,

    Sorry I missed this earlier.

    The short answer is that no, I don' t think it will make GZ-CANDELS irrelevant. Two examples of why not:

    • First, as you are aware, there's nothing irrelevant about two pieces of work verifying each other. That would be true even if the CANDELS team used an exact replica of our classification tree (or we theirs), which is not so. The classification structure the CANDELS team uses is different from what we use (e.g., our treatment of clumpy galaxies is different), and Jeyhan and I and others are planning to collaborate to compare and contrast the results from the two methods.
    • Second, the 65 individual classifiers did not each classify all 7,634 galaxies; their target is to have at least 3 independent classifications of each galaxy, which is achieved by spreading the work among their 65 classifiers. As you know, our numbers are different. The first GZ-CANDELS paper will publish results that are based on typically between 40 and 80 independent classifications of each galaxy. I'll leave it up to you to decide whether the contributions of those extra 77 volunteers per galaxy (or our thousands of volunteers total) are irrelevant or not; personally I believe they are extremely valuable.

    Cheers,

    -Brooke

    Posted

  • JeanTate by JeanTate in response to vrooje's comment.

    Hi Brooke.

    Thanks for the explanation.

    Over in the GZ forum, zutopian posted a link to a 2012 paper by Carol Christian, Chris Lintott, Arfon Smith, Lucy Fortson, and Steven Bamford, "Citizen Science: Contributions to Astronomy Research" (arXiv abstract here). I know I'd read it, probably not long after it was posted, but I'd forgotten that it said something very interesting about Talk:

    In addition to the main site, tools which encourage communication between the volunteers and the project scientists and developers are of vital importance in attracting and sustaining a community. Much of the serendipitous science from Galaxy Zoo came from a basic forum, and a new ‘Talk’ tool that can be more closely integrated with the process of classification
    itself has been developed and released 21 . The ultimate goal of such tools should be to bring questions and interesting discoveries to the scientists’ attention only when expert input is necessary, reducing the time needed for appropriate mentoring while still ensuring nothing gets lost. For more one way communication, most citizen science projects use blogs to keep the community informed about the progress of research.

    21 https://github.com/zooniverse/Talk

    Els has been doing a simply astonishingly fantastic job of answering questions about particular objects (can we clone her?)! 😄 I'm keen to do my part, and encourage more communication between the zooites and project scientists and developers, in a way that complements what Els does.

    C'mon you other zooites, it's your community too! 😃

    Posted

  • zutopian by zutopian

    New GZ paper related to the classification of the CANDELS images:

    Galaxy Zoo: CANDELS Barred Disks and Bar Fractions

    Future comparison with independent morphologies of the same galaxies (e.g., Kartaltepe et al. 2014) as well as additional simulations will help provide a more nuanced understanding of the underlying physical causes of this apparently stable bar fraction.

    B. D. Simmons, Thomas Melvin, Chris Lintott, Karen L. Masters, Kyle W. Willett, William C. Keel, R. J. Smethurst, Edmond Cheung, Robert C. Nichol, Kevin Schawinski, Michael Rutkowski, Jeyhan S. Kartaltepe, Eric F. Bell, Kevin R. V. Casteels, Christopher J. Conselice, Omar Almaini, Henry C. Ferguson, Lucy Fortson, William Hartley, Dale Kocevski, Anton M. Koekemoer, Daniel H. McIntosh, Alice Mortlock, Jeffrey A. Newman, Jamie Ownsworth, Steven Bamford, Tomas Dahlen, Sandra M. Faber, Steven L. Finkelstein, Adriano Fontana, Audrey Galametz, N. A. Grogin, Ruth Grutzbauch, Yicheng Guo, Boris Haussler, Kian J. Jek, Sugata Kaviraj, Ray A. Lucas, Michael Peth, Mara Salvato, Tommy Wiklind, Stijn Wuyts
    (Submitted on 3 Sep 2014)
    http://arxiv.org/abs/1409.1214

    Posted

  • ElisabethB by ElisabethB moderator in response to zutopian's comment.

    Congratulations Brooke et al ! 😄

    Posted

  • Capella05 by Capella05 moderator

    Excellent work, Brooke and company! 😄

    Posted

  • zutopian by zutopian

    @galaxyzoo (twitter) information: There is following Sky&Telescope article about the paper "Galaxy Zoo: CANDELS Barred Disks and Bar Fractions".:

    Citizen Scientists Probe Early Galaxies By: Shannon Hall | September 29, 2014
    http://www.skyandtelescope.com/astronomy-news/citizen-scientists-probe-early-galaxies-09292014/#sthash.3ihR3Xxs.dpuf

    Posted