Galaxy Zoo Talk

Recent Galaxy Zoo related submissions to arXiv (and elsewhere)

  • mlpeck by mlpeck

    I'll start with Galaxy Zoo:Hubble and GZ2 papers, in reverse chronological order:

    Posted

  • mlpeck by mlpeck

    New on arxiv 30 Sep. 2014:

    Kuminski, E. et al. 2014: Combining human and machine learning for morphological analysis of galaxy images.

    They're looking at using GZ classifications as training data for machine learning algorithms:

    Here we propose to use citizen science data for training machine
    learning systems, and show experimental results demonstrating that
    machine learning systems can be trained with citizen science data. Our
    findings show that the performance of machine learning depends on the
    quality of the data, which can be improved by using samples that have
    a high degree of agreement between the citizen scientists.

    The authors appear to be completely independent of the Zooniverse team.

    Posted

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

    Melvin, T. et al. 2014: Galaxy Zoo: An independent look at the evolution of the bar fraction over the last eight billion years from HST-COSMOS. Published in MNRAS 438, 2882.

    GZ forum thread on this paper; and a GZ blog post on it.

    Cheung, E. et al. 2013: Galaxy Zoo: Observing Secular Evolution Through Bars. Published in ApJ 779, 162.

    GZ Talk thread on this paper; and (at least) two GZ blog posts, here, and here.

    Posted

  • zutopian by zutopian

    Corresponding topic in the old Galaxy Zoo forum:

    Galaxy Zoo papers and papers that build upon our results

    http://www.galaxyzooforum.org/index.php?topic=275570.0

    Posted

  • mlpeck by mlpeck

    For anyone not following along on github, the submitted version of Marshall, Lintott & Fletcher 2015: "Ideas for Citizen Science in Astronomy" was posted earlier this week. I haven't done a detailed comparison with version 1, but the authors clearly responded to feedback left on the "issues" section of github and the end result looks like a considerable improvement to me. I still have quibbles with the discussion of the one project where I have a fair amount of first hand knowledge, but I'll save that for elsewhere.

    Anyway, it's well worth reading and not at all technical.

    GZ Talk thread here. And there's a bit of discussion on Quench Talk here.

    Posted

  • zutopian by zutopian

    Paper about Hubble Telescope imaging of eight voorwerpjes aka ionized gas clouds:

    HST Imaging of Fading AGN Candidates I: Host-Galaxy Properties and Origin of the Extended Gas
    William C. Keel, W. Peter Maksym, Vardha N. Bennert, Chris J. Lintott, S. Drew Chojnowski, Alexei Moiseev, Aleksandrina Smirnova, Kevin Schawinski, C. Megan Urry, Daniel A. Evans, Anna Pancoast, Bryan Scott, Charles Showley, Kelsi Flatland
    (Submitted on 21 Aug 2014)
    http://arxiv.org/abs/1408.5159

    Talk topic about the paper.:
    http://talk.galaxyzoo.org/#/boards/BGZ0000001/discussions/DGZ0000ynf

    Posted

  • mlpeck by mlpeck

    I probably would have missed this if the lead author hadn't been introduced on the GZ blog recently:

    Mao, M. et al. 2014: J1649+26: A Grand-Design Spiral with a Large Double-Lobed Radio Source.

    The selection as a spiral was based on the "superclean" GZ1 database.

    I question whether this is a true "grand design" spiral. I think it's more likely to be an ETG that got a recent injection of fuel and the spiral structure is transient. This is the second of three possible scenarios they consider. The SDSS nuclear spectrum is typical for a "red and dead" galaxy, except there are some emission lines with line ratios compatible with a low excitation AGN.

    Here is the decimal position of the host galaxy for anyone who might want to check in Navigate (I recommend DR10) -- (ra, dec) = (252.35, +26.5839).

    Posted

  • mlpeck by mlpeck

    Not quite a galaxy zoo paper, but it's in the same zooniverse. New on arxiv 22 January 2015:

    Johnson, L.C. et al. 2015: PHAT Stellar Cluster Survey. II. Andromeda Project Cluster Catalog.

    Accepted by ApJ according to the comments accompanying the abstract.

    Posted

  • Capella05 by Capella05 moderator

    Galaxy Zoo: Evidence for Diverse Star Formation Histories through the Green Valley

    R. J. Smethurst, C. J. Lintott, B. D. Simmons, K. Schawinski, P. J. Marshall, S. Bamford, L. Fortson, S. Kaviraj, K. L. Masters, T. Melvin, R. C. Nichol, R. A. Skibba, K. W. Willett

    Abstract: Does galaxy evolution proceed through the green valley via
    multiple pathways or as a single population? Motivated by recent
    results highlighting radically different evolutionary pathways between
    early- and late-type galaxies, we present results from a simple
    Bayesian approach to this problem wherein we model the star formation
    history (SFH) of a galaxy with two parameters, [t, τ ] and compare the
    predicted and observed optical and near-ultraviolet colours. We use a
    novel method to investigate the morphological differences between the
    most probable SFHs for both disc-like and smooth-like populations of
    galaxies, by using a sample of 126, 316 galaxies (0.01 < z < 0.25)
    with probabilistic estimates of morphology from Galaxy Zoo. We find a
    clear difference between the quenching timescales preferred by smooth-
    and disc-like galaxies, with three possible routes through the green
    valley dominated by smooth- (rapid timescales, attributed to major
    mergers), intermediate- (intermediate timescales, attributed to minor
    mergers and galaxy interactions) and disc-like (slow timescales,
    attributed to secular evolution) galaxies. We hypothesise that
    morphological changes occur in systems which have undergone quenching
    with an exponential timescale τ < 1.5 Gyr, in order for the evolution
    of galaxies in the green valley to match the ratio of smooth to disc
    galaxies observed in the red sequence. These rapid timescales are
    instrumental in the formation of the red sequence at earlier times;
    however we find that galaxies currently passing through the green
    valley typically do so at intermediate timescales.

    Published today (27/01) on arXiv - Congratulations Becky and co!

    Edit to add: Although it was not in the paper summary - It was accepted by MNRAS last week - so a double congratulation! 😃

    Posted

  • mlpeck by mlpeck

    This one has both a GZ and RGZ connection. Posted on arxiv 2 Feb 2015 and according to the comment line accepted to MNRAS:

    Wong, O. Ivy, et al. 2015, "Misalignment between cold gas and stellar components in early-type galaxies."

    This describes a pilot radio study of 4 "blue ellipticals" from Schawinski's compilation.

    Posted

  • JeanTate by JeanTate

    Gravitational lens modelling in a citizen science context

    By: Rafael Küng, Prasenjit Saha, Anupreeta More, Elisabeth Baeten, Jonathan Coles, Claude Cornen, Christine Macmillan, Phil Marshall, Surhud More, Jonas Odermatt, Aprajita Verma, Julianne K. Wilcox

    Ref: arXiv:1502.00008

    Abstract:

    We develop a method to enable collaborative modelling of gravitational lenses and lens candidates, that could be used by non-professional lens enthusiasts. It uses an existing free-form modelling program (glass), but enables the input to this code to be provided in a novel way, via a user-generated diagram that is essentially a sketch of an arrival-time surface. We report on an implementation of this method, SpaghettiLens, which has been tested in a modelling challenge using 29 simulated lenses drawn from a larger set created for the Space Warps citizen science strong lens search. We find that volunteers from this online community asserted the image parities and time ordering consistently in some lenses, but made errors in other lenses depending on the image morphology. While errors in image parity and time ordering lead to large errors in the mass distribution, the enclosed mass was found to be more robust: the model-derived Einstein radii found by the volunteers were consistent with those produced by one of the professional team, suggesting that given the appropriate tools, gravitational lens modelling is a data analysis activity that can be crowd-sourced to good effect. Ideas for improvement are discussed, these include (a) overcoming the tendency of the models to be shallower than the correct answer in test cases, leading to systematic overestimation of the Einstein radius by 10 per cent at present, and (b) detailed modelling of arcs.

    The following have their institution listed as "Zooniverse, c/o Astrophysics Department, University of Oxford, Oxford OX1 3RH, UK":

    • Elisabeth Baeten
    • Claude Cornen
    • Christine Macmillan
    • Julianne K. Wilcox

    Congratulations one and all! 😄

    Posted

  • mlpeck by mlpeck

    New on arxiv 5 Feb 2015:

    Galloway, M.A. et al., "Galaxy Zoo: the effect of bar-driven fueling on the presence of an active galactic nucleus in disc galaxies."

    Here's the abstract in full:

    We study the influence of the presence of a strong bar in disc galaxies which host an active galactic nucleus (AGN). Using data from
    the Sloan Digital Sky Survey and morphological classifications from
    the Galaxy Zoo 2 project, we create a volume-limited sample of 19,756
    disc galaxies at 0.01<z<0.05 which have been visually examined for the
    presence of a bar. Within this sample, AGN host galaxies have a higher
    overall percentage of bars (51.8%) than inactive galaxies exhibiting
    central star formation (37.1%). This difference is primarily due to
    known effects; that the presence of both AGN and galactic bars is
    strongly correlated with both the stellar mass and integrated colour
    of the host galaxy. We control for this effect by examining the
    difference in AGN fraction between barred and unbarred galaxies in
    fixed bins of mass and colour. Once this effect is accounted for,
    there remains a small but statistically significant increase that
    represents 16% of the average barred AGN fraction. Using the
    L[OIII]/MBH ratio as a measure of AGN strength, we show that barred AGN
    do not exhibit stronger accretion than unbarred AGN at a fixed mass
    and colour. The data are consistent with a model in which bar-driven
    fueling does contribute to the probability of an actively growing
    black hole, but in which other dynamical mechanisms must contribute to
    the direct AGN fueling via smaller, non-axisymmetric perturbations.

    My immediate reaction on a quick skim through is to wonder if no astronomer has ever heard of logit or probit regression.

    Posted

  • JeanTate by JeanTate

    Galaxy Zoo: the dependence of the star formation-stellar mass relation on spiral disk morphology

    By: Kyle W. Willett, Kevin Schawinski, Brooke D. Simmons, Karen L. Masters, Ramin A. Skibba, Sugata Kaviraj, Thomas Melvin, O. Ivy Wong, Robert C. Nichol, Edmond Cheung, Chris J. Lintott, Lucy Fortson

    Ref: arXiv:1502.03444

    Abstract:

    We measure the stellar mass-star formation rate relation in star-forming disk galaxies at z<0.085, using Galaxy~Zoo morphologies to examine different populations of spirals as classified by their kiloparsec-scale structure. We examine the number of spiral arms, their relative pitch angle, and the presence of a galactic bar in the disk, and show that both the slope and dispersion of the M-SFR relation is constant when varying all the above parameters. We also show that mergers (both major and minor), which represent the strongest conditions for increases in star formation at a constant mass, only boost the SFR above the main relation by ~0.3 dex; this is significantly smaller than the increase seen in merging systems at z>1. Of the galaxies lying significantly above the M-SFR relation in the local Universe, more than 50% are mergers. We interpret this as evidence that the spiral arms, which are imperfect reflections of the galaxy's current gravitational potential, are either fully independent of the various quenching mechanisms or are completely overwhelmed by the combination of outflows and feedback. The arrangement of the star formation can be changed, but the system as a whole regulates itself even in the presence of strong dynamical forcing.

    Posted

  • mlpeck by mlpeck

    Not exactly a Galaxy Zoo paper, but this will interest GZ Forum old-timers. New on arxiv 2 March 2015:

    Davies, Schirmer, and Turner 2015: The "Green Bean" Galaxy SDSS J224024.1--092748: Unravelling the emission signature of a quasar ionization echo.

    Posted

  • Capella05 by Capella05 moderator

    The Red Radio Ring: a gravitationally lensed hyperluminous infrared radio galaxy at z=2.553 discovered through citizen science

    J. E. Geach, A. More, A. Verma, P. J. Marshall, N. Jackson, P.-E. Belles, R.Beswick, E. Baeten, M. Chavez, C. Cornen, B. E. Cox, T. Erben, N. J. EricksonS. Garrington, P. A. Harrison, K. Harrington D. H. Hughes, R. J. Ivison,C. Jordan, Y.-T. Lin, A. Leauthaud, C. Lintott, S. Lynn, A. Kapadia, J.-P.Kneib, C. Macmillan, M. Makler, G. Miller, A. Montana
    , R. Mujica, T.Muxlow, G. Narayanan, D. O Briain ´ , T. O’Brien, M. Oguri, E. Paget, M.Parrish, N. P. Ross, E. Rozo, E. Rusu, E. S. Rykof, D. Sanchez-Arguelles ¨,
    R. Simpson, C. Snyder, F. P. Schloerb, M. Tecza, L. Van Waerbeke, J. Wilcox,M. Viero, G. W. Wilson, M. S. Yun, M. Zeballos

    We report the discovery of a gravitationally lensed hyperluminous infrared galaxy (LIR ≈
    1013L⊙) with strong radio emission (L1.4GHz ≈ 1025 W Hz−1
    ) at z = 2.553. The source was
    identified in the citizen science project SPACE WARPS through the visual inspection of tens of
    thousands of iJKs colour composite images of Luminous Red Galaxies (LRGs), groups and
    clusters of galaxies and quasars. Appearing as a partial Einstein ring (re ≈ 3
    ′′) around an LRG
    at z = 0.2, the galaxy is extremely bright in the sub-millimetre for a cosmological source,
    with the thermal dust emission approaching 1 Jy at peak.

    Edited 24/03/2015 20:15: More importantly here is a full list of all the contributors! Congrats everyone 😃

    Posted

  • c_cld by c_cld

    Rotation-invariant convolutional neural networks for galaxy morphology prediction

    Sander Dieleman, Kyle W. Willett, Joni Dambre

    Measuring the morphological parameters of galaxies is a key requirement for studying their formation and evolution. Surveys such as the Sloan Digital Sky Survey (SDSS) have resulted in the availability of very large collections of images, which have permitted population-wide analyses of galaxy morphology. Morphological analysis has traditionally been carried out mostly via visual inspection by trained experts, which is time-consuming and does not scale to large (≳10 4 ) numbers of images.
    Although attempts have been made to build automated classification systems, these have not been able to achieve the desired level of accuracy. The Galaxy Zoo project successfully applied a crowdsourcing strategy, inviting online users to classify images by answering a series of questions. Unfortunately, even this approach does not scale well enough to keep up with the increasing availability of galaxy images.
    We present a deep neural network model for galaxy morphology classification which exploits translational and rotational symmetry. It was developed in the context of the Galaxy Challenge, an international competition to build the best model for morphology classification based on annotated images from the Galaxy Zoo project.
    For images with high agreement among the Galaxy Zoo participants, our model is able to reproduce their consensus with near-perfect accuracy (>99% ) for most questions. Confident model predictions are highly accurate, which makes the model suitable for filtering large collections of images and forwarding challenging images to experts for manual annotation. This approach greatly reduces the experts' workload without affecting accuracy. The application of these algorithms to larger sets of training data will be critical for analysing results from future surveys such as the LSST.

    Accepted for publication in MNRAS arXiv:1503.07077 [astro-ph.IM]

    Posted

  • JeanTate by JeanTate

    Double congrats to Sander ... he was the one (or at least first) to find a flaw in the classification data originally posted in the Kaggle Challenge (if memory serves). Kyle had to withdraw the data (and initial training set), fix it; resulting in a restart. I do not know if this also necessitated a revision of the public GZ2 dataset, to fix the flaw Sander found, or whether this error was limited to just the classification data used in the Kaggle Challenge.

    The paper makes only the most oblique of references to this hiccup: "The final training set of data consisted of 61,578 JPEG colour images of galaxies, ..."; "final" implies there was more than one training set ...

    From memory, Sander was also one of the competitors who asked the most interesting questions about GZ2, our classifications, etc.

    Posted

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

    This is a very cool paper; I recommend zooites who like reading GZ-related papers to take the time to read this one (it's quite different from the usual GZ papers).

    For me, the money plot is Figure 9, "Level of agreement (red circles) and model confidence (blue squares) versus classification accuracy for all questions (see Table 1), computed on the real-time evaluation set. The overall classification accuracy is indicated as a thick horizontal line. The dotted and dashed horizontal lines indicate the maximal accuracy of 100% and the chance-level accuracy respectively. The number of images that were included in the analysis and the overall classification accuracy for each question are indicated above the graphs." One translation: "after being trained, a machine can do just as well as GZ zooites, collectively, in galaxy morphology". A machine, no less, that's essentially just an ordinary desktop PC.

    I think it's well worth re-reading some of the GZ and Zooniverse blog posts on machine learning in astronomy, to see what this implies for future Zoos. For example (I think they're all by Chris Lintott):

    Also well worth re-reading - especially the presentations - is Wrap-Up from the Workshop on Citizen Science in Astronomy.

    Of course, GIGO still applies ... Sander's winning Kaggle Challenge entry did a wonderful job of faithfully classifying the 'odd feature', 'disturbed':

    The unit visualized in Figure 13b detects imaging artifacts: black lines running across the centre of the images, which are the result of dead pixels in the SDSS camera. This is interesting because such (known) artifacts are not morphological features of the depicted galaxies. It turns out that the network is trying to replicate the behaviour of the Galaxy Zoo participants, who tend to classify images featuring such artifacts as disturbed galaxies (answer A8.3 in Table 1), even though this is not the intended meaning of this answer. Most likely this is because the button for this answer in the Galaxy Zoo 2 web interface seems to feature
    such a black line.

    Or, in Kyle's words from a conference (the one in Sydney Australia?), 'be careful what you ask for'.

    Perhaps another take-away might be 'be sure to invite experienced, oldbie zooites to join the team; conduct a proper beta'. What do you think?

    Posted

  • mlpeck by mlpeck

    New on arxiv 30 March 2015: Carpineti, A. et al., "An infrared study of local galaxy mergers." The authors used the original GZ's merger classifications to identify merger candidates that they confirmed with their own visual inspection. This is a followup to Darg et al. (2010).

    A couple of noteworthy oddities: their source of IR data was a catalog derived from IRAS, which operated for 10 months way back in 1983. The paper is mercifully short, and it was submitted to A&A instead of MNRAS, the usual favorite of GZ related authors.

    Posted

  • mlpeck by mlpeck

    New Space Warps paper on arxiv 23 April 2015:

    More, A. et al. 2015: "Space Warps II. New Gravitational Lens Candidates from the CFHTLS Discovered through Citizen Science."

    From the intro:

    Galaxy Zoo was the first citizen science project in astronomy...

    Seriously?? That's one of the more absurdly ahistorical claims I've read recently.

    Posted

  • Capella05 by Capella05 moderator in response to mlpeck's comment.

    I think that is just a typo - 'and' should be substituted with 'that' - as in:

    Galaxy Zoo was the first citizen science project in astronomy,
    that addressed the problem of how to classify large numbers of galaxies by their morphology (Lintott et al. 2008).

    I will get Anu to have a look. Thanks!

    Posted

  • ElisabethB by ElisabethB moderator

    And a second one. Actually it is the first one ! 😉

    Space Warps: I. Crowd-sourcing the Discovery of Gravitational Lenses

    Posted

  • mlpeck by mlpeck

    This was new on arxiv 13 May 2015 -- I'd call it a semi-independent use of GZ data rather than a GZ paper as such, although several members of the core GZ science team are co-authors.

    Cheung, E. et al. 2015, "Stellar Populations of Barred Quiescent Galaxies."

    The authors used spectroscopic data + GZ2 classifications to select a sample of barred quiescent (i.e. no detected emission lines) galaxies and a control sample of non-barred quiescent disks. They also used GZ2 classifications to exclude probable mergers.

    The main objective of the paper was to look for differences in gradients of stellar population properties (ages, metallicity, Mg/Fe) between barred and non-barred galaxies. They didn't find any.

    Posted

  • Capella05 by Capella05 moderator

    Radio Galaxy Zoo:

    Radio Galaxy Zoo: host galaxies and radio morphologies derived from visual inspection

    We present results from the first twelve months of operation of Radio Galaxy Zoo, which upon completion will enable visual inspection of over 170,000 radio sources to determine the host galaxy of the radio emission and the radio morphology. Radio Galaxy Zoo uses 1.4GHz radio images from both the Faint Images of the Radio Sky at Twenty Centimeters (FIRST) and the Australia Telescope Large Area Survey (ATLAS) in combination with mid-infrared images at 3.4μm from the {\it Wide-field Infrared Survey Explorer} (WISE) and at 3.6μm from the {\it Spitzer Space Telescope}. We present the early analysis of the WISE mid-infrared colours of the host galaxies. For images in which there is >75% consensus among the Radio Galaxy Zoo cross-identifications, the project participants are as effective as the science experts at identifying the host galaxies. The majority of the identified host galaxies reside in the mid-infrared colour space dominated by elliptical galaxies, quasi-stellar objects (QSOs), and luminous infrared radio galaxies (LIRGs). We also find a distinct population of Radio Galaxy Zoo host galaxies residing in a redder mid-infrared colour space consisting of star-forming galaxies and/or dust-enhanced non star-forming galaxies consistent with a scenario of merger-driven active galactic nuclei (AGN) formation. The completion of the full Radio Galaxy Zoo project will measure the relative populations of these hosts as a function of radio morphology and power while providing an avenue for the identification of rare and extreme radio structures. Currently, we are investigating candidates for radio galaxies with extreme morphologies, such as giant radio galaxies, late-type host galaxies with extended radio emission, and hybrid morphology radio sources.

    J.K. Banfield, O.I. Wong, K.W. Willett, R.P. Norris, L. Rudnick, S.S. Shabala, B.D. Simmons, C. Snyder, A. Garon, N. Seymour, E. Middelberg, H. Andernach, C.J. Lintott, K. Jacob, A.D. Kapinska, M.Y. Mao, K.L. Masters, M.J. Jarvis, K. Schawinski, E. Paget, R. Simpson, H.R. Klockner, S. Bamford, T. Burchell, K.E. Chow, G. Cotter, L. Fortson, I. Heywood, T.W. Jones, S. Kaviraj, A.R. Lopez-Sanchez, W.P. Maksym, K. Polsterer, K. Borden, R.P. Hollow, L. Whyte

    Posted

  • mlpeck by mlpeck

    Kind of an interesting juxtaposition of papers on arxiv today (21 Sep 2015):

    http://arxiv.org/abs/1509.05430: Ferrari, de Carvalho, & Trevisan (2015): "Morfometryka -- A New Way of Establishing Morphological Classification of Galaxies"

    and right next to it:

    http://arxiv.org/abs/1509.05429: Huertas-Company et al. (2015): "A catalog of visual-like morphologies in the 5 CANDELS fields using deep-learning"

    The first group used GZ1 classifications and a fairly standard classical statistical procedure to train a quantitative morphogical classification system.

    The second doesn't really have a direct GZ connection, but they did use the method (and perhaps the code -- that's not quite clear to me) of the winner of the Kaggle galaxy zoo competition from a year or so ago. Their training set was the catalog of visual classifications of CANDELS galaxies by Kartaltepe et al. (2014).

    Posted

  • mlpeck by mlpeck

    Another independent use of GZ data posted on arxiv 22 March 2016: de Souza, R.S. et al.: "Is the cluster environment quenching the Seyfert activity in elliptical and spiral galaxies?" (1603.06256) They used GZ1 to select samples of spirals and ellipticals.

    I haven't fully read the paper yet but I noticed a couple of interesting things in it. For one, they used a technique called "propensity score matching" to pick a sample of inactive galaxies that were matched as closely as possible on several parameters to their Seyfert sample. A couple of years ago I used a very similar technique to produce a volume limited control sample matched to what would have been the final study sample in the Quench project. Had that project led to a publication I think it would have been the first published example in the astronomical literature of using a well defined optimization model to produce matched control and active samples.

    The other interesting thing here is a really sophisticated statistical analysis that's, um, light years ahead of most astronomy literature. The presentation is really nice too.

    Posted

  • JeanTate by JeanTate

    Galaxy Zoo: Mergers - Dynamical Models of Interacting Galaxies, Holincheck+ (2016); here's the abstract:

    The dynamical history of most merging galaxies is not well understood. Correlations between galaxy interaction and star formation have been found in previous studies, but require the context of the physical history of merging systems for full insight into the processes that lead to enhanced star formation. We present the results of simulations that reconstruct the orbit trajectories and disturbed morphologies of pairs of interacting galaxies. With the use of a restricted three-body simulation code and the help of Citizen Scientists, we sample 10^5 points in parameter space for each system. We demonstrate a successful recreation of the morphologies of 62 pairs of interacting galaxies through the review of more than 3 million simulations. We examine the level of convergence and uniqueness of the dynamical properties of each system. These simulations represent the largest collection of models of interacting galaxies to date, providing a valuable resource for the investigation of mergers. This paper presents the simulation parameters generated by the project. They are now publicly available in electronic format at this http URL Though our best-fit model parameters are not an exact match to previously published models, our method for determining uncertainty measurements will aid future comparisons between models. The dynamical clocks from our models agree with previous results of the time since the onset of star formation from star burst models in interacting systems and suggests that tidally induced star formation is triggered very soon after closest approach.

    Posted

  • JeanTate by JeanTate

    Galaxy Zoo: comparing the demographics of spiral arm number and a new method for correcting redshift bias, Hart+ (2016); here's the abstract:

    The majority of galaxies in the local Universe exhibit spiral structure with a variety of forms. Many galaxies possess two prominent spiral arms, some have more, while others display a many-armed flocculent appearance. Spiral arms are associated with enhanced gas content and star-formation in the disks of low-redshift galaxies, so are important in the understanding of star-formation in the local universe. As both the visual appearance of spiral structure, and the mechanisms responsible for it vary from galaxy to galaxy, a reliable method for defining spiral samples with different visual morphologies is required. In this paper, we develop a new debiasing method to reliably correct for redshift-dependent bias in Galaxy Zoo 2, and release the new set of debiased classifications. Using these, a luminosity-limited sample of ~18,000 Sloan Digital Sky Survey spiral galaxies is defined, which are then further sub-categorised by spiral arm number. In order to explore how different spiral galaxies form, the demographics of spiral galaxies with different spiral arm numbers are compared. It is found that whilst all spiral galaxies occupy similar ranges of stellar mass and environment, many-armed galaxies display much bluer colours than their two-armed counterparts. We conclude that two-armed structure is ubiquitous in star-forming disks, whereas many-armed spiral structure appears to be a short-lived phase, associated with more recent, stochastic star-formation activity.

    Posted

  • mlpeck by mlpeck

    If you missed the announcement on twitter there are two Galaxy Zoo papers on arxiv this morning, 12 October 2016:

    Simmons, B.D. et al. 2016, "Galaxy Zoo: Quantitative Visual Morphological Classifications for 48,000 galaxies from CANDELS"

    Willett, K.W. et al. 2016, "Galaxy Zoo: Morphological Classifications for 120,000 Galaxies in HST Legacy Imaging."

    Catalogs appear to be up at data.galaxyzoo.org as well.

    Posted

  • ElisabethB by ElisabethB moderator

    Tx mlpeck for posting the links ! 😄

    Posted

  • klmasters by klmasters scientist, admin

    Kyle and Brooke also did blog posts explaining the papers a bit more: blog.galaxyzoo.org. 😃

    Posted

  • zutopian by zutopian

    New paper related to GZ, but the authors aren't GZ astronomers.:

    On the nature and correction of the spurious S-wise spiral galaxy winding bias in Galaxy Zoo 1
    Authors: Wayne Hayes, Darren Davis, Pedro Silva

    The Galaxy Zoo 1 catalog displays a bias towards the S-wise winding direction in spiral galaxies which has yet to be explained. The lack of an explanation confounds our attempts to verify the Cosmological Principle, and has spurred some debate as to whether a bias exists in the real universe. The bias manifests not only in the obvious case of trying to decide if the universe as a whole has a winding bias, but also in the more insidious case of selecting which galaxies to include in a winding direction survey. While the former bias has been accounted for in a previous image-mirroring study, the latter has not. Furthermore, the bias has never been corrected in the GZ1 catalog, as only a small sample of the GZ1 catalog was re-examined during the mirror study.
    We show that the existing bias is a human selection effect rather than a human chirality bias. (...)

    (Submitted on 22 Oct 2016)
    https://arxiv.org/abs/1610.07060

    Posted

  • mlpeck by mlpeck

    Serendipitous (and directed) discoveries by GZ volunteers continue to pay dividends: Keel, W.. et al. (2017?), "Fading AGN Candidates: AGN Histories and Outflow Signatures."

    A couple of highlights from the abstract:

    We consider energy budgets and radiative history of 8 fading AGN,
    identified from mismatch between the ionizion of very extended (>10
    kpc) ionized clouds and the luminosity of the nucleus viewed directly.
    All show significant fading on ~50,000-year timescales.

    ...

    We present Gemini integral-field optical spectroscopy, which shows a
    very limited role for outflows in these ionized structures. While rings
    and loops of emission, morphologically suggestive of outflow, are
    common, their kinematic structure shows some to be in regular
    rotation. UGC 7342 exhibits local signatures of outflows < 300 km s−1,
    largely associated with very diffuse emission, and possibly entraining
    gas in one of the clouds seen in HST images. Only in the Teacup AGN do
    we see outflow signatures of order 1000 km s−1. In contrast to the
    extended emission regions around many radio-loud AGN, the clouds
    around these fading AGN consist largely of tidal debris being
    externally illuminated but not displaced by AGN outflows.

    Added:

    Blog post by Bill Keel: https://blog.galaxyzoo.org/2016/12/20/new-hubblegemini-results-history-of-fading-agn/

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  • mlpeck by mlpeck

    Found 24 April 2017 on arxiv: Smethurst et al. 2017, "Galaxy Zoo: The interplay of quenching mechanisms in the group environment."

    Too long; didn't read, but here's the abstract:

    Does the environment of a galaxy directly influence the quenching
    history of a galaxy? Here we investigate the detailed morphological
    structures and star formation histories of a sample of SDSS group
    galaxies with both classifications from Galaxy Zoo 2 and NUV
    detections in GALEX. We use the optical and NUV colours to infer the
    quenching time and rate describing a simple exponentially declining
    SFH for each galaxy, along with a control sample of field galaxies. We
    find that the time since quenching and the rate of quenching do not
    correlate with the relative velocity of a satellite but are correlated
    with the group potential. This quenching occurs within an average
    quenching timescale of ∼2.5 Gyr from star forming to complete
    quiescence, during an average infall time (from ∼10R200 to 0.01R200)
    of ∼2.6 Gyr. Our results suggest that the environment does play a
    direct role in galaxy quenching through quenching mechanisms which are
    correlated with the group potential, such as harassment, interactions
    or starvation. Environmental quenching mechanisms which are correlated
    with satellite velocity, such as ram pressure stripping, are not the
    main cause of quenching in the group environment. We find that no
    single mechanism dominates over another, except in the most extreme
    environments or masses. Instead an interplay of mergers, mass &
    morphological quenching and environment driven quenching mechanisms
    dependent on the group potential drive galaxy evolution in groups.

    I wonder if astronomers spend much time worrying about replicability.

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  • mlpeck by mlpeck

    This is pretty cool (at the top of the arxiv for 21 July 2017):

    Buta, R.J. 2017, "Galactic Rings Revisited. I. CVRHS Classifications of 3962 Ringed Galaxies from the Galaxy Zoo 2 Database."

    Here's the abstract in full:

    Rings are important and characteristic features of disc-shaped
    galaxies. This paper is the first in a series which re-visits galactic
    rings with the goals of further understanding the nature of the
    features and for examining their role in the secular evolution of
    galaxy structure. The series begins with a new sample of 3962 galaxies
    drawn from the Galaxy Zoo 2 citizen science database, selected because
    zoo volunteers recognized a ring-shaped pattern in the morphology as
    seen in Sloan Digital Sky Survey colour images. The galaxies are
    classified within the framework of the Comprehensive de Vaucouleurs
    revised Hubble-Sandage (CVRHS) system. It is found that zoo volunteers
    cued on the same kinds of ring-like features that were recognized in
    the 1995 Catalogue of Southern Ringed Galaxies (CSRG). This paper
    presents the full catalogue of morphological classifications,
    comparisons with other sources of classifications, and some histograms
    designed mainly to highlight the content of the catalogue. The
    advantages of the sample are its large size and the generally good
    quality of the images; the main disadvantage is the low physical
    resolution which limits the detectability of linearly small rings such
    as nuclear rings. The catalogue includes mainly inner and outer disc
    rings and lenses. Cataclysmic ("encounter-driven") rings (such as ring
    and polar ring galaxies) are recognized in less than 1% of the
    sample.

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  • JeanTate by JeanTate

    Submitted last Thursday, but appeared only today, arXiv:1711.06270, "Joint NuSTAR and Chandra analysis of the obscured quasar in IC 2497 - Hanny's Voorwerp system", by Lia F. Sartori, Kevin Schawinski, Michael J. Koss, Claudio Ricci, Ezequiel Treister, Daniel Stern, George Lansbury, W. Peter Maksym, Mislav Balokovic, Poshak Gandhi, William C. Keel, and David R. Ballantyne. Here's the abstract:

    NH∼2×1024 cm−2, current intrinsic luminosity Lbol∼2−5×1044 erg s−1) whose luminosity dropped by a factor ∼50 within the last ∼100 kyr. This corresponds to a change in Eddington ratio from λEdd∼0.06 to λEdd∼0.001. We argue that the AGN in IC 2497 should not be classified as a changing-look AGN, but rather we favour the interpretation where the AGN is undergoing a change in accretion state (from radiatively efficient to radiatively inefficient). In this scenario the observed drop in luminosity and Eddington ratio corresponds to the final stage of an AGN accretion phase. Our results are consistent with previous studies in the optical, X-ray and radio although the magnitude of the drop is lower than previously suggested. In addition, we discuss a possible analogy between X-ray binaries and AGN.

    Very nice paper! 😃

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  • JeanTate by JeanTate

    Submitted, and posted, yesterday, arXiv:1711.07297, "Models of gravitational lens candidates from Space Warps CFHTLS", by Rafael Küng, Prasenjit Saha, Ignacio Ferreras, Elisabeth Baeten, Jonathan Coles, Claude Cornen, Christine Macmillan, Phil Marshall, Anupreeta More, Lucy Oswald, Aprajita Verma, and Julianne K. Wilcox. Here's the abstract:

    We report modelling follow-up of recently-discovered gravitational-lens candidates in the Canada France Hawaii Telescope Legacy Survey. Lens modelling was done by a small group of specially-interested volunteers from the SpaceWarps citizen-science community who originally found the candidate lenses.
    Models are categorised according to seven diagnostics indicating (a) the image morphology and how clear or indistinct it is, (b) whether the mass map and synthetic lensed image appear to be plausible, and (c) how the lens-model mass compares with the stellar mass and the abundance-matched halo mass.
    The lensing masses range from ~10^11 Msun to >10^13 Msun. Preliminary estimates of the stellar masses show a smaller spread in stellar mass (except for two lenses): a factor of a few below or above ~10^11 Msun. Therefore, we expect the stellar-to-total mass fraction to decline sharply as lensing mass increases.
    The most massive system with a convincing model is J1434+522 (SW05). The two low-mass outliers are J0206-095 (SW19) and J2217+015 (SW42); if these two are indeed lenses, they probe an interesting regime of very low star-formation efficiency. Some improvements to the modelling software (SpaghettiLens), and discussion of strategies regarding scaling to future surveys with more and frequent discoveries, are included.

    Well done, Elisabeth, Claude, Christine, and Julianne! 😃

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

    Tx Jean ! 😄

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  • JeanTate by JeanTate

    "Galaxy Zoo: Morphological classification of galaxy images from the Illustris simulation", by Hugh Dickinson, Lucy Fortson, Chris Lintott, Claudia Scarlata, Kyle Willett, Steven Bamford, Melanie Beck, Carolin Cardamone, Melanie Galloway, Brooke Simmons, William Keel, Sandor Kruk, Karen Masters, Mark Vogelsberger, Paul Torrey, Gregory F. Snyder. To be published in The Astrophysical Journal. Appeared on arXiv today (astro-ph link). Abstract:

    Modern cosmological simulations model the universe with increasing sophistication and at higher spatial and temporal resolutions. These enhancements permit detailed comparisons between the simulation outputs and real observational data. Recent projects such as Illustris are capable of producing simulated images that are comparable to those obtained from local surveys. This paper tests how well Illustris achieves this goal across a diverse population of galaxies using visual morphologies derived from Galaxy Zoo citizen scientists. Morphological classifications provided by volunteers for simulated galaxies are compared with similar data for a compatible sample of images drawn from the SDSS Legacy Survey. This paper investigates how simple morphological characterization by human volunteers asked to distinguish smooth from featured systems differs between simulated and real galaxy images. Differences are identified, which are likely due to the limited resolution of the simulation, but which could be revealing real differences in the dynamical evolution of populations of galaxies in the real and model universes. Specifically, for stellar masses M⋆≲1011M⊙, a larger proportion of Illustris galaxies that exhibit disk-like morphology or visible substructure, relative to their SDSS counterparts. Toward higher masses, simulated and observed galaxies converge and exhibit similar morphology distributions. The stellar mass threshold indicated by this divergent behavior confirms recent works using parametric measures of morphology from Illustris simulated images. When M⋆≳1011M⊙, the Illustris dataset contains fewer galaxies that classifiers regard as unambiguously featured. These results suggest that comparison between the detailed properties of observed and simulated galaxies, even when limited to reasonably massive systems, may be misleading.

    Clearly, cosmological simulations of galaxies have a long way to go before they produce realistic-looking galaxies across the full range of known, local, real galaxies ...

    ... and maybe one day such simulations will also produce realistic Green Peas, voorwerpjies, SDRAGNs, even post-starburst (E+A) galaxies, ...

    UPDATE: GZ blogpost about this paper, today, by the lead author

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