Try to finish this hunt by 5:15pm on Tuesday afternoon

Those people who are not going on the platform tour should work on this scavenger hunt Tuesday morning and be ready to help others go through it quickly. We also suggest that groups may want to have different members work on the different sections and then share results.



Useful links:
  • Using Arecibo for ALFALFA
  • Using ALFALFA for science
  • AO telescope schedule
  • A2010 observer's page
  • Observing checklist for LBW observing
  • L-band wide (LBW) observing for ALFALFA followup
  • Standard ALFALFA LBW followup observing modes
  • Instructions on reducing LBW data using IDL_LBW

  • TOPCAT
  • ALFALFA data release page


    Rules of the scavenger hunts: You may consult any source anywhere but please be sure to indicate where you got your information. And watch out for bad websites!


    UAT14.01 Scavenger Hunt #2:   Introduction to more useful tools to use ALFALFA for science!

    This scavenger hunt will provide an introduction to our SKYD utility to generate links to public databases and the TOPCAT, the Tool for OPerations on Catalogues And Tables. Then we'll look at some more LBW spectra to investigate some of the objects observed by the awesome UAT over the past few years.


    A2010 observers' favorite quote
    "A hypothesis or theory is clear, decisive, and positive, but it is believed by no one but the [person] who created it. Experimental findings, on the other hand, are messy, inexact things, which are believed by everyone except the [person] who did the work."
    -- Harlow Shapley, "Through Rugged Ways to the Stars"



    2.0   Introduction to SKYD and SKYDEG to generate links to public databases

    We have developed some simple IDL utilities which you can use to generate a set of links to public databases, notably the Sloan Digital Sky Survey (SDSS), SkyView/the Digital Sky survey (DSS) and the NASA Extragalactic Database (NED). SKYD and SKYDEG are similar routines which take input coordinates (RA and Dec). Both of them generate an output file called skylinks.html in the directory in which you run IDL (... so you need to pay attention). There is an option to append the file or start a new one but the file always has the same name, so take that into account. There are also small differences in their usage, so learn which is better for what application. In either case, the input coordinates must always be in epoch J2000.0; the difference between them is whether the input format is in decimal degrees (SKYDEG) or as given in the ASCII version of the AGC (SKYD). SKYD can also read a list of positions from an input file in standard AGC format.

    SKYD: Works on single entries from the command line or alternatively an AGC-style input file. The format for input is hhmmsss+ddmmss just as in the ASCII version of the AGC.
    SKYDEG: Works on single entries from the command line where the positions are given in decimal degrees.

    Here are links to the front pages of the SDSS, SkyView/DSS and the NED: If you are not already familiar with these really useful websites, we suggest that you should become more familiar with them tonight, tomorrow or after you return from the workshop. Here, we'll hope that someone in your group knows enough to use them to answer the questions below about some of our favorite galaxies.

    a.   Start up IDL as you did yesterday through to running @lbwinit. Be sure to work in the directory assigned to your team!

    b.   Use SKYDEG to generate the links to the object whose LBW spectrum we reduced at in yesterday's Scavenger Hunt under 1.4. Then copy the HTML file with the links to your local machine (ask for help if you need it). The use FIREFOX or your favorite browser to examine the links to answer the remaining questions in this section.

    c.   What is the SDSS name of the spectroscopic target?

    d.   What is the recessional velocity given by the SDSS spectrum?

    e.   How does the SDSS velocity compare with the one you measured from the LBW spectrum yesterday? Is the difference significant?

    f.   What does the SDSS spectrum tell you about star formation in this galaxy?


    Now that you know how to use SKYDEG, use it in the future to learn more about interesting ALFALFA galaxies.


    2.1   Exploring the universe with TOPCAT: the Tool for OPerations on Catalogues And Tables, an interactive java graphical program which has been developed by astronomers at the Virtual Astronomical Observatory.

    We hope that many of you will have already experimented with TOPCAT and that everyone with a laptop has already installed it, as suggested in Scavenger Hunt #0.

        a.   Do you have access to the UAT groups Google sites page?.   Hint: Find it at: https://sites.google.com/site/alfalfaugradgroups/. If you do, go there and log in. If not, send email to Becky or David's gmail account. David's is jblxdwc@gmail.com. They can add you to the site. When you reach the site, look the bar on the left. Under **Programs** you will see UAT TOPCAT Docs, click there. If you have not visited this site recently (or at all), briefly review the documents there; refer to them as needed as we proceed.

        b.   Start up TOPCAT on your machine.   If you have not installed TOPCAT on your laptop or local machine, follow the steps in **Installing and Getting Started** for your system. Java web start is generally the easiest, or Mac disk images, but TOPCAT is also easy to install on Windows machines.

        c.   In the latter part of the **Installing and getting started** on the UAT wiki, read section on the 2.1 **Loading data from a CSV file**. What does "CSV" stands for?

        d.   Go to the public ALFALFA catalog release page. If you have not already committed it to perfect memory, peruse the α.40 paper. You will find detailed information on the content and format of the three data files in the header of the ASCII versions of the data files. What does "ASCII" stand for?

        e.   Right-click (or whatever) to download the .csv file associated with Table 1 of the α.40 paper to you computer using the **CSV** link. Be sure you know where it is located on your disk. Then, using TOPCAT, load the .csv file into a table. How do you let TOPCAT know that it is a .csv file?

        f.   Review the column headers in the Table within TOPCAT. They should match the descriptions in the header of its ASCII file. At what resolution is the rms calculated?

    We will use this file in the next section.

    There are lots of other things you can do with TOPCAT. We encourage you to learn how to exploit its capability and of course, to use it further at the workshop!



    2.2   The AGC, α.40 and TOPCAT

    As discuss in Hunt #0, members of the ALFALFA team are granted access to the AGC, a private compilation of information about galaxies in the local universe maintained by Martha and Riccardo. The AGC includes not only the galaxies detected by ALFALFA but also many others contained in optical catalogs including those whose redshifts have been measured by the SDSS. It is important to keep in mind that the AGC is a "living" database, constantly being updated to improve its use; this version was generated on December 30th, 2013. At the same time, it is important to remember that the α.40 catalog contains only those objects detected by ALFALFA over a limited region of the (larger) survey area.

        a.   For the purpose of this activity, download the CSV version of a subset of the AGC called agcvels.hunt14.csv. This is a big file, so it might take a minute to download. This version contains galaxies in the region of the sky ALFALFA was intended to survey and is up to date as of Dec 30, 2013. Note also that objects flagged as "High Velocity Clouds" (ALFALFA code 9 detections) are not included in this version.

    Use TOPCAT, this AGC file and the file with Table 1 of the α.40 paper (which you downloaded in 2.1) to answer the remaing questions in this section.

        b.   How many entries are there in the agcvels.hunt14.csv file? In the α.40 file?

        c.   Use the "Sky" Spherical Plot capability to overplot the α.40 catalog points on the agcvels.hunt14.csv entries. Comment on your result.

        d.   Make a histogram of the heliocentric velocities ("vhelagc") in the agcvels.hunt14.csv catalog. Then superpose on it the histogram of the heliocentric velocities ("Vhelio") in the α.40 catalog. Comment on your result.

        e.   Run a "pair match" (under "Joins") using a sky matching criterion between the two catalogs. Hint: this isn't a trivial process.... you'll need to think about how to do this! How many matches do you find?

        f.   Run a "pair match" (under "Joins") using a "Exact Value" matching criterion between the two catalogs. How many matches do you find? Compare the answer you get here to the one you got in "e". What do you conclude?

        g.   Use the "Row Subset" capability on the agcvels.hunt14.csv file with the skyDistanceDegrees function to find the AGC number of the galaxy at RA = 226.6217, Decl = 1.605. What is it?

        h.   Use TOPCAT to get the SDSS color image of that galaxy using the Activation Action (last row under Current Table Properties in main control window) and selecting Display Cutout Image from the popup window, then selecting SDSS Color images from the pulldown menu. To see the image, you can click on a table row.

        i.   To learn more, use the SKYDEG IDL utility to generate the links for this object. Why does Becky care about this galaxy?



    2.3   The color-magnitude diagram and how galaxy color correlates with morphology

    Probably you are familiar with the Hertzsprung-Russell diagram for stellar classification. We can make a similar "color-magnitude" diagram for galaxies using TOPCAT and the photometric data from the SDSS. For nearby galaxies, there are problems with the standard SDSS photometric pipeline, so we use the ones available through the NASA-Sloan Atlas (N-S Atlas). We can also look at the morphological classification provide by the citizen science project Galaxy Zoo.

    For this exercise, we have put together a useful dataset in CSV format from a combination of the N-S Atlas and the Galaxy Zoo 1 data release. It does not cover the whole sky because each galaxy has to be included in both catalogs. The file contains the basic information plus we have calculated a color (called "gminusi") and an absolute magnitude ("absmagi") as well as an indicator of morphology. Note that the way the morphological type is identified is by having a flag set to "1" according to whether the galaxy was classified as "spiral", "elliptical" or "uncertain". In fact, most galaxies are typed "uncertain".

        a.   Why do we call the difference between the magnitude measured in the SDSS-g band and that in the SDSS-i band a "color"?

        b.   Because we wanted to keep things simple, using only the raw data as they are included in the compilations, we have limited this subset to galaxies which are viewed face-on. Why does that make things simpler?

        c.   First, using the N-S Atlas magnitudes, make a color-magnitude diagram using the absolute magnitude and color given here. Be sure that luminosity increases from left to right and that blue galaxies are towards the botton, red towards the top. What do you notice about the distribution of galaxies?   (Note: this diagram will be useful to some of the teams in SH#3).

    Next, let's add the information about morphology from the GZ.

        d.   Use the "column statistics" capability to figure out quickly the fraction of the galaxies which are classified as ellipticals? As spirals? As uncertain?

        e.   Using the TOPCAT subsets capability, plot the spirals and ellipticals separately, using different symbols/colors. Superpose the spirals on the ellipticals (be sure to do it in that order). What do you conclude?



    2.4   Interesting LBW targets!

    In this part, you should investigate some interesting LBW spectra observed in the our various LBW observing runs in the last couple of years. As in yesterday's exercise, you are given the filename corresponding to the LBW spectrum. Your job is to use whatever methods you can to explore the LBW data and measure its line properties but you should also try to determine the nature of the extragalactic source detected by LBW. What can you tell us about the objects assigned to your team? At the end of the day, each team will present its results (in 3 minutes or less total.... so SUMMARIZE!)

    Team filename AGC number LBW Spectral Measurements Optical Counterpart Other notable information
    A /proj/a2669/corfile.22mar12.a2669.52    
     
     
    		 
     
     
    		 
     
     
      /proj/a2752/corfile.22mar13.a2752.17    
     
     
    		 
     
     
    		 
     
     
    B /proj/a2707/corfile.13jan13.a2707.32    
     
     
    		 
     
     
    		 
     
     
      /proj/a2752/corfile.20mar13.a2752.6    
     
     
    		 
     
     
    		 
     
     
    C /proj/a2752/corfile.25mar13.a2752.32    
     
     
    		 
     
     
    		 
     
     
      /proj/a2669/corfile.18jan12.a2669.16    
     
     
    		 
     
     
    		 
     
     
    D /proj/a2669/corfile.18jan12.a2669.36    
     
     
    		 
     
     
    		 
     
     
      /proj/a2752/corfile.27mar13.a2752.9    
     
     
    		 
     
     
    		 
     
     
    E /share/olcor/corfile.29nov13.a2811.7    
     
     
    		 
     
     
    		 
     
     
      /proj/a2707/corfile.15jan13.a2707.28    
     
     
    		 
     
     
    		 
     
     
    F /proj/a2752/corfile.22mar13.a2752.10    
     
     
    		 
     
     
    		 
     
     
      /share/olcor/corfile.25nov13.a2811.6    
     
     
    		 
     
     
    		 
     
     




    2.4   (Important) questions about the Arecibo staff

    a.   Which Arecibo staff member spent 8 years with the Klamath Indians in Oregon (rustling cattle, so the rumor goes) before moving to Puerto Rico?

    b.   Who is perfecting a new drink called the "avocalada"?

    c.   What was the traditional sumptuous delicacy made by Martha and savored by Willy during late night observing runs over the Christmas and New Year's holidays?

    d.   Who played Carl Sagan wandering around the observatory during the filming of the Cosmos series, when Carl did not make the trip to Arecibo?

    e.   What former Arecibo atmospheric scientist is the author of the (classic) mystery novel "Murder at Arecibo"?



    Last updated Sun Jan 12 14:08:34 EST 2013 by martha