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NVO DEMONSTRATION

PART I: ACQUIRE DATA

1. Go to the NVO website at http://us-vo.org/index.cfm

2. Open the Data Scopewindow, approximately half way down the page, by entering M51.

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NOTE:It should take approximately 5 minutes for Data Scope to check all possible sources ofinformation (n=435).

The green bar at the top of the Data Scope page should make note of 362 sources found out of apossible 435. The progress for data sources containing information on M51 can be seen at thebottom of the page.

NOTE:You can select and retrieve the needed data prior to Data Scope completing its searchof all 435 sources. As well, if another individual at STScI has selected the data set in the pastweek, the search will be cached, reducing the retrieval time.

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3. Click on SDSSDR3-I(0/8) [ I band SDSS image], and click okin the confirmation box. Apreview of the image can be viewed by clicking on the ?for each entry. From this, you willsee that image 2 is the best.

4. Click in the box next to image 2 to select the image, and then click on Return to summarypage.

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5. Click on Save locally as TAR file, and choose a directory to save the file in.

6. It will then be necessary to go to the directory where you saved the file to untar and unzip it.Untarring and unzipping the file will vary from one operating system to the next.

In UNIX/LINUXit will be necessary to untar datascope-4267.tar (number will vary),

change directories to SDSSDR3-I, and then unzip the .fits file.

In Windows, it will be necessary to use WinZip by double-clicking the file,"datascope_4267.tar", select the listed file "SDSSDR3-I.1.2.fits", answer yesin thecaution window. This will open a new window allowing you to save the .fits file by using theextractbutton. Use My Documents to locate the file, and then rename it if you like (e.g.,SDSSDR3_M51_feb15) (5.82 MB).

PART II: PHOTOMETRY & DATA CROSS-MATCH

1.

Go back to the NVO home page, http://us-vo.org/index.cfm, and select the link PerformSource Extraction and Object Identification", approximately2/3of the way down the page.

This will take you to the WESIX main page.

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2. Under Step 1: Specify the file, click on the Browse button, locate the .fits file in yourdirectory structure, and select it.

NOTE: Do Nothit the first here near the top of the WESIX main page. This will take 20+minutes to download and will not provide a useable image.

3. Under Step 2: Select the catalog, click on "TWOMASS".

4. Under Step 3: Choose whether you want, click in the box.

5.

Under Step 4: Submit your file, click submit.

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6. Under Step 5: Select the output, select NUMBER.

NOTE:To make multiple selections, use ctrl-left click simultaneously to make n selections.For MAC users, use the apple button-left click to make your selections. For some reason, itseams as though WESIX will select all variables regardless of the ones that you specify.However, it is necessary to choose at least one for the software to run correctly.

7. Under Step 6: Choose the columns, select objID, j_m, and h_m.NOTE:j_m looks more like i_m on screen.

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8. Under Step 7: SExtractor params, change the Detection Thresholdand Analysis

Thresholdboth, from 1.5 to 10.

9. Under Step 8Click "Go do it!".

NOTE:A common error message encountered at this point suggests that outputmight be too large. It will sometimes help to use a higher S/N in the previous step.

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10.Click on the link, "Here is the matched file"to view the cross-matched catalog. You can alsoview the SExtractor catalog at, Here is the source catalog file, and the 2MASS catalog at,Here are the sources from OpenSkyQuery.net in the region of your image..

11.To view the cross-matched image data, you can either click herein the sentence, To beginvisualizing your data, click here, or you could simply click the link to Aladinin theWESIX toolbar at the top of the page.

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NOTE:Please be patient as it make take a few minutes for Aladin to display all cross-matchedlayers.

12.If you click on the histbutton in the vertical toolbar just to the right of the display, you canmove the center triangle to adjust the contrast of the image display.

13.

You can use the zoombutton to zoom in and to adjust the position of the object in thedisplay.

14.Click on the colored labels, just above the zoom screen (bottom right), to turn various cross-match image layers on and off.

PART III: PLOTTING & CLASSIFICATION

1. To view a plot of the cross-matched data, begin by going back to the previous screen (from Part

II, Step 11).

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2. You can either click herein the sentence, To plot your data, click here, or you couldsimply click the link to Plotterin the WESIX toolbar at the top of the page.

3. From the top two pull-down menus located to the right of the plot grid (both of which areinitially set to RA), select twomass_j_mfor the y-axis variable, and twomass_h_mforthe x-axis variable, and then click on the plotbutton.

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4. Try clicking on the histogrambutton.

5. Create a new column to plot by clicking on the Functionspull-down menu in the toolbar justabove the plot grid, and select Create New Columns.

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6. By clicking on the individual cells in the Column Idcolumn and clicking the buttons in theOperator Calculator menu, enter the following expression in the Enter expression:window: $11 - $7.

7. Enter a name for the new column, Aper-Iso, and click Add,and then Close.

8. As before, use the pull-down menus to the right of the plot grid to plot Aper-Isoversusmydata_mag_aper.

9. Confirm that the modein the bottom right of the plot screen is set to "Select", and click-and-drag to select points on the plot.

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10.Using the Data in Table Formaticon near the bottom right corner of the screen, you canview the table of selected points.