SkyServer, Web page, Data limited to 1000 galaxies
http://skyserver.sdss.org/en/tools/search/sql.asp
SkyServer, Web page, Data limited to 10,000 galaxies
http://skyserver.pha.jhu.edu/dr1/en/tools/search/sql.asp
Plots using SkyServer data are inferior to those made from sdssQA, for unknown reasons.
DR1 (Data Release 1), Unlimited data
Catalog Archive Server accessed at
http://skyserver.pha.jhu.edu/dr1/en/
Use the following to access data from the SkyServer:
http://skyserver.pha.jhu.edu/dr1/en/tools/search/sql.asp
Choose the HTML format. Copy and paste the following Structured Query Language (SQL):
SELECT z, ra, dec
FROM specObj
WHERE specClass=2 AND z BETWEEN 0 and 0.05 AND dec BETWEEN -3 AND 3 AND ra BETWEEN 0 and 360
The result is the z, ra, and dec of 7095 galaxies (as of July 2, 2003). Use Select All to copy and paste the data to a spreadsheet. Delete the SQL instructions, leaving just the column labels and the data.
You need to convert the polar coordinates z and ra to the Cartesian coordinates x and y. In a new column labeled x, use the formula (in Excel): =z*COS(PI()*ra/180), where the cell labels replace z and ra. The List Wizard (in Excel) will help you to replicate the formula in all the other rows without dragging.
In a new column labeled y, use the formula (in Excel): =z*SIN(PI()*ra/180), where the cell labels replace z and ra. Again use the List Wizard to avoid dragging through the large number of rows.
Click above the x column to select it (cursor becomes a down arrow). Then hold shift as you press Control-End (Mac) to add the y column to the selection. Now click on the Chart Wizard, choosing the x-y scatter plot. After plotting, double click on one of the points to bring up the menu that allows you to change point size and shape. Choose the 2pt short dash (-), then re-plot.
Start to make the random plot by first copying and pasting the ra values to a new worksheet. Head a new empty column z on the worksheet, then insert the formula =RAND()*(0.05) to create random values of z between 0 and 0.05. After using the AutoFill feature for a few rows, you should be prompted by the List Wizard to fill out the remaining rows (7095 total) with the formula. Compute x and y as before, then plot as before.
2D Plot in Mathematica: Data from Web (10,000 Galaxy Limit)
Use the following to access data from the SkyServer (10,000 row limit):
http://skyserver.pha.jhu.edu/dr1/en/tools/search/sql.asp
Choose the CSV format. Copy and paste the following Structured Query Language (SQL):
SELECT z, ra, dec
FROM specObj
WHERE specClass=2 AND z BETWEEN 0 and 0.05 AND dec BETWEEN -3 AND 3 AND ra BETWEEN 0 and 360
The result is the z, ra, and dec of 7095 galaxies (as of July 2, 2003). Use Select All to copy and paste the data to a word processor (e.g., Notepad or Word). Record the heading in the exact order that it appears (z, ra, dec) for reference, then delete the heading leaving the data. Save the file as text.
Read the data into Mathematica by using the OpenRead command. See the Mathematica notebook galPlot2D.nb (right click, Win; ctrl click, Mac) for details in plotting in x-y format or polar format. Polar plotting requires the package PolarListPlot that can be downloaded along with a tutorial from
http://library.wolfram.com/infocenter/MathSource/2061/
Install the query tool, available on the web site
http://skyserver.pha.jhu.edu/dr1/en/
Copy and paste the the following Structured Query Language (SQL) in the window:
SELECT z, ra, dec
FROM specObj
WHERE specClass=2 AND z BETWEEN 0 and 0.05 AND dec BETWEEN -3 AND 3 AND ra BETWEEN 0 and 360
To save this SQL for later use, give the file a .sql suffix. Clicking on the arrow of the sdssQA tool generates the data. Save the data in a file with the .csv suffix. Although the sdssQA tool allows acquisition of data limited only by hard drive capacity, Excel accepts data for only 65,535 galaxies. Import data into Excel by the FileĞ>Open sequence, then follow the procedure above.
Start to make the random plot by first copying and pasting the ra values to a new worksheet. Head a new empty column z on the worksheet, then insert the formula =RAND()*(0.05) to create random values of z between 0 and 0.05. After using the AutoFill feature for a few rows, you should be prompted by the List Wizard to fill out the remaining rows (7095 total) with the formula. Compute x and y as before, then plot as before.
Install the query tool, available on the web site
http://skyserver.pha.jhu.edu/dr1/en/
Copy and paste the the following Structured Query Language (SQL) in the window:
SELECT z, ra, dec
FROM specObj
WHERE specClass=2 AND z BETWEEN 0 and 0.05 AND dec BETWEEN -3 AND 3 AND ra BETWEEN 0 and 360
To save this SQL for later use, give the file a .sql suffix. Clicking on the arrow of the sdssQA tool generates the data. Save the data in a file with the .csv suffix.
Read the data into Mathematica by using the OpenRead command. See the Mathematica notebook galPlot2D.nb (right click, Win; ctrl click, Mac) for details in plotting in x-y format or polar format. The csv data saved here under sdssQA is different from the csv data saved above under SkyServer for unknown reasons. Polar plotting requires the package PolarListPlot that can be downloaded along with a tutorial from
http://library.wolfram.com/infocenter/MathSource/2061/
Copy and paste the following SQL in the sdssQA window:
SELECT S.z, G.ra, G.dec, G.u-G.r, G.g
FROM Galaxy G, SpecObj S
WHERE S.bestObjID=G.ObjID AND S.z BETWEEN 0 AND 0.1 AND G.dec BETWEEN -3 AND 3
The result is 25,871 galaxies (as of August 5, 2003). Early-types (ellipticals) are separated from late-types (spirals) by first plotting u-r versus g. Note that the data cluster into two clumps with a split at ~2.2. (Strateva, et. al. astro-ph/0107201). Make the x-y plot using the conversion from polar coordinates given above. Separate the data according to uĞr>2.22 (ellipticals), and uĞr<2.22 (spirals). Make two new plots, one for spirals, the other for ellipticals, and note the difference between them.
Install the query tool, available on the web site
http://skyserver.pha.jhu.edu/dr1/en/
Copy and paste the the following Structured Query Language (SQL) in the window:
SELECT z, ra, dec
FROM specObj
WHERE specClass=2 AND dec BETWEEN -90 AND 90 AND ra BETWEEN 0 AND 360 AND z<0.1
To save this SQL for later use, give the file a .sql suffix. Clicking on the arrow of the sdssQA tool generates the data. Save the data in a file with the .csv suffix.
Read the data into Mathematica by using the OpenRead command. See the Mathematica notebook galPlot3D.nb (right click, Win; ctrl click, Mac) for details. The csv data saved here under sdssQA is different from the csv data saved above under SkyServer for unknown reasons.