Galaxy Zoo Starburst Talk

Core Questions for GZ Quench

  • mzevin1 by mzevin1 scientist, moderator

    Hello everyone!

    In this thread, it would be great if we could put together a list of core questions we would like to address with this project and our data. A good jumping-off point would be to look at the questions that were addressed in related research projects, such as the ones summarized here. We can address things that have been touched on in previous research projects, but it is also important to attack questions that are still unanswered, questions we may be able to probe with our data.

    Let's start by compiling a list on this thread, and once we get a substantial list we can pick out a handful of questions we would like to be the primary focus of this project.


  • JeanTate by JeanTate in response to mzevin1's comment.

    This is a great idea, mzevin! 😃

    One suggestion:

    such as the ones summarized here.

    As far as I know, I am the only zooite who even reads this Talk - let alone is still actively posting to it - who is currently in China. Be that as it may, I strongly urge you - or someone else on the Science or Development Teams - to move it away from Blogger. Why? Because blogspots cannot be seen, by zooites in China. Wordpress (WP) is OK - the Galaxy Zoo blog ( is WP-based and visible, as are the other Zooniverse ones - but only if they are re-named ... Science Blog from the SDSS-III ( uses WP in its name, and is, as a result, unobtainable1

    One can live without FB and Twitter; losing the videos of the Hangouts (etc) - they're saved in YouTube, which is also unobtainable here - is disappointing but not central to doing science. However, the blogspot summaries are not only excellent (IMHO) but essential to the Quench project.

    1 I haven't yet written to the SDSS team, telling them about this


  • zutopian by zutopian

    Which topics are related to/relavent/useful for this new topic?

    I guess following ones:

    Science Board / Background Information

    • Popular science articles about galaxy evolution and/or post-quenched galaxies

    • Scientific Articles about Galaxy Evolution and Post-quenched Galaxies

    • Interested in Learning About the Science Context for GZ Quench? Start Here.

    • Websites with information about galaxy evolution and/or post-quenched galaxies

    • Beyond background information

    The following ones combined are same as this new topic, aren't they?

    • Science goals
    • Questions inspired by or about the background literature.

    Framework and suggestions for Data Analysis Phase

    Are there any further ones?


  • mlpeck by mlpeck

    Here's what I think is a key result, and a few questions that follow: as discussed here and here ~35-50% of the quench sample objects have experienced recent strong starbursts based on their position in the Hδ - D4000 plane (the range is based on the criterion used, not uncertainty about the index values). Many of those objects have AGN/LINER spectra.


    1. Can we quantify the burst strength and burst age? Not with the currently available tools, but in principle yes.

    2. Did mergers play a role? A preliminary look using the original classifications suggested possibly yes. Obviously this needs to be looked at again.

    3. I mentioned somewhere that I saw hints of support for an idea of Schawinski et al. (2007) that galaxies evolve through the BPT diagram. Is this worth following up?

    More later, perhaps.


  • mlpeck by mlpeck

    30% of the quench sample objects are classified as starforming by their position in the classic BPT diagram. See here and here. This is almost identical to the percentage of starforming objects in the control sample.

    This gets directly to the sample selection. Does this mean that the selection criteria resulted in a significant fraction of false positives? Or are the quenched starformers actually quenched relative to _______ (fill in the blank here)?

    I see some evidence that the quench sample starformers are in fact edging their way into the "green valley" -- scroll down through the second thread and also see here.


  • JeanTate by JeanTate in response to mzevin1's comment.

    From this post, I think the key question is something like this:

    How are post-quenched galaxies different, morphologically, from (non-post-quenched) galaxies of the same stellar mass and redshift?


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

    I copied your comment to the "Sample Selection" topic.:

    This gets directly to the sample selection. (...)