Quench Boost: A How-To-Guide, Part 2

It was amazing how quickly the new Quench classifications were completed. We posted them on Friday and you were already done by Sunday morning. Wow, that’s awesome! This means we can turn our full attention to making sense of the data. And we need your help!

In Part 1 of this How-To-Guide to data analysis within Quench, you learned how to use Tools, our analysis platform, and were inspired (or so I hope) about ways to play with the data as you read the background literature about post-quenched galaxies and galaxy evolution.

In Part 2 of this How-To-Guide, we’re going to help you navigate using Tools to compare results from galaxies *you* classified with the rest of the post-quenched galaxy sample.

You’re 12 small steps away from your first comparison plot between your galaxies and the full sample… let’s get started!

Step 1: Enter Tools and log in using your Zooniverse login information.

Step 2: Choose ‘Quench’ in the pull-down menu in the upper-left, next to the words ‘zootools’. Now click ‘Create Dashboard*’ in the upper-right, and give it a name, like: ‘My Data in Context’.

Step 3: Click ‘Data’ in the upper-left and choose ‘Zooniverse’ in the pop-up options.

Step 4: In the window that pops up, choose ‘Recents’ or ‘Collections’. Your choice.

If you classified galaxies in quench.galaxyzoo.org, they’ll be accessible through ‘Recents’. Choose the max number possible. If you created a Collection of interesting galaxies in Quench Talk or want to look at someone else’s Collection, you can access them by clicking ‘Collections’.

I’ve created a Dashboard* in Tools called ‘Example: My Data in Context’. Take a look and, if you’d like, you can even make edits by copying it into your Tools environment.

In my Dashboard ‘Example: My Data in Context’, I chose ‘Collections’. I love #Quencher SUMO_2011’s Collection of ‘Blue’ galaxies from Quench. If you go to that URL, the Collection ID is listed after the final ‘/’ in the URL. In this case, the Collection ID is CGSS00000x. I inputted that ID into the pop-up window in Tools, in the box next to ‘Enter Collection Id:”. I then clicked on ‘Import Data’.

Step 5: Now that you have your galaxies’ information imported into the Dashboard, it’s time to play with them. Click on ‘Tools’ in the upper-left and choose ‘Table’ in the pop-up options.

Step 6: In your Table window, choose ‘Zooniverse-1’ in the pull-down menu under ‘Data Source’. Now the Table knows to work with that set of data.

Step 7: As in Part 1 of this How-To-Guide (https://blog.galaxyzoo.org/2013/08/23/quench-boost-a-how-to-guide-part-1/), you’ll make a new column that has color information about your galaxies. You do this by subtracting the brightness of your galaxy in one filter from the brightness of your galaxy in another filter.

In the open space under ‘Prompt’ in your Table, write: field ‘My Galaxies Color u-r’, .u-.r

If you scroll to the right in your table, you’ll see that you created a new column of information, called ‘My Galaxies Color u-r’.

Step 8: Click ‘Tools’ in the upper-left and choose ‘Scatterplot’ in the pop-up options.

Step 9: In your Scatterplot window, choose ‘Table-2’ in the pull-down menu under ‘Data Source’. Now the Scatterplot knows to work with the Table, which includes your new column with Color information.

Step 10: Choose ‘log_mass’ for the X-axis and ‘My Galaxies Color u-r’ for the Y-axis. Recent star formation is seen strongly in the u-band while older stars dominate the r-band. The color, u-r, tells you about the star formation history for each of your galaxies. Check out this post for more details.

Step 11: How do your galaxies compare with the full sample of post-quenched galaxies? To answer this, we redo the steps 3-10 above, but for the post-quenched galaxy sample.

  • Click on ‘Data’ in the upper-left and choose ‘Quench’ in the pop-up options.
  • Click on ‘Quench Sample’ in the pop-up window.
  • Click on ‘Tools’ in the upper-left and choose ‘Table’ in the pop-up options.
  • In the new Table window, choose ‘Quench-4’ in the pull-down menu under ‘Data Source’. This loads the Quench Sample into that Table.
  • In the open space under ‘Prompt’ in your Table, write: field ‘Quench Galaxies Color u-r’, .u-.r
  • Click on ‘Tools’ in the upper-left and choose ‘Scatterplot’ in the pop-up options.
  • In the new Scatterplot window, choose ‘Table-5’ in the pull-down menu under ‘Data Source’.
  • Choose ‘log_mass’ for the X-axis and ‘Quench Galaxies Color u-r’ for the Y-axis.
  • Zoom in on the data, for example, choosing Xmin: 7, Xmax: 12, Ymin: 1, and Ymax: 4.

Step 12: Place your two scatterplots side by side. For a fair comparison, make sure the x- and y-axis range is the same for both plots, otherwise the stretch might skew your analysis. I tend to make the axes ranges in the plot showing My Galaxies match the plot showing the Quench Sample.

What do you notice about your subsample of post-quenched galaxies compared to the full sample? Do they occupy a particle sub-space within the plot? Or are they randomly distributed throughout the quench space?

The figure below shows what you’ll see if, like me, you uploaded SUMO_2011’s Collection of blue galaxies. You’ll notice that all of the blue-collection galaxies are way bluer (closer to the bottom of the plot, near values u-r = 1.5) than the full post-quenched galaxy sample (which spread from u-r values of 1 to u-r values of 3.5 and higher). This is a reassuring reality check given what you see visually when you look at the color of the galaxies. The plot also tells us that since these blue galaxies have such low values of ‘u-r’, they’ve had more recent star formation than most of the post-quenched galaxies.

In looking at these two plots side-by-side, I wondered: Why are there so few massive post-quenched galaxies (log_mass > 11) with bluer colors (u-r < 2.0)? If we compare our post-quenched galaxies with our control galaxies, do I see any difference? Specifically, are there massive (log_mass > 11) control galaxies with bluer colors (u-r < 2.0)? If there are, what might that be telling me about our post-quenched galaxy sample? 

Stay tuned for Part 3 of our How-To-Guide for taking part in the analysis phase of the research process. If you have suggestions for what you’d like to learn more about, please post here. Thank you all, and keep on Quenching!

*Dashboard is the place within Tools (tools.zooniverse.org) for volunteers to observe, collect, and analyze data from Zooniverse citizen science projects.

Comparing SUMO_2011's Quench Galaxies with the Full Sample

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4 responses to “Quench Boost: A How-To-Guide, Part 2”

  1. Jean Tate says :

    Tools is very powerful, and has great potential!

    There are, however, some tips and traps; it can all go wrong – sometimes horribly – if you don’t know about them.

    For example, the “greater than” and “less than” characters – I dare not use them in my comment, because their use may really mess it up! – are ‘control characters’, and using one or the other can produce unpredictable results (Laura’s copy/paste of part of the blog post, into Talk, is an example; check out page two of thread/discussion called “Mass-driven star formation quenching?”, or click on this link:
    http://quenchtalk.galaxyzoo.org/#/boards/BGS0000008/discussions/DGS00001xe?page=2&comment_id=521fb1d58ff909040300014f )

    Be aware, too, that Tools is still under development, and you may encounter bugs. For example, I could not get my axes to have Max or Min values beyond the range of the data I was (scatter)plotting … but somehow Laura was able to! So be sure to use Talk to call for help, and post anything that you think might be a bug.

  2. Chris Lloyd says :

    Really enjoying working through this tutorial. Zooniverse Tools is fairly intuitive and, so far, stable on my old macbook.

Trackbacks / Pingbacks

  1. Quench Boost: A How-To-Guide, Part 3 | Galaxy Zoo - September 13, 2013
  2. Quench Boost: A How-To-Guide, Part 4 | Galaxy Zoo - September 15, 2013

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