1	Cooking with Sloan: CASCA 2007 Pat Hall (York), Jordan Raddick, Ani Thakar (JHU) Alex Szalay, Maria Nieto-Santisteban, Nolan Li, Wil O’Mullane, Adrian Pope, Tamas Budavari, George Fekete, Sam Carliles JHU Brian Yanny, Svetlana Lebedeva FermiLab Jim Gray Microsoft Research
2	SDSS-I is now SDSS-II, with 3 subsurveys: Legacy Continuation of SDSS-I (completion of 8500 sq.deg.) Completeness is same as for SDSS-I Flux limits are the same Target all galaxies with r_petro < 17.77, plus LRGs, quasars, … SEGUE Sparse-sampled 3-d map of the Galaxy Spectra of 240,000 stars in the disk and spheroid Age, composition and phase space distribution CAS component cataloged in SegueDRx DB Supernova Survey Repeated scans of SDSS Southern Stripe over 3 months/yr Data not available in CAS yet, will be on DAS soon
3	SDSS Data Overview Data Archive Server (DAS) FITS files (raw data) Images, spectra, corrected frames, atlas images, binned images, masks Online form-based access Rsync and wget file retrieval
4	CAS Datasets (databases) BestDRx (DR5 now, DR6 later this summer) Latest, greatest calibration of the data Photometric and spectroscopic objects The default and most accessed (by far) dataset TargDRx The calibration from which spectroscopic targets were chosen RUNS All the runs (processings) other than Best, Target SegueDRx New with DR6 (SDSS-II)
5	Data Access http://www.sdss.org Click on `Data Products’ – has someone already done your work for you? If not, click on ‘Data Access’ for links to both CAS and DAS: http://www.sdss.org/dr5/access/ Or CAS SkyServer: http://cas.sdss.org/astro/ Search Tools Advanced Tools, including visual tools & CasJobs Help and Tutorials
6	CAS Data Access SkyServer Web browser is all you need Meant to support several levels of users: http://cas.sdss.org/astro/ \| http://skyserver.sdss.org/ Visual tools to browse image and catalog data Command-line application programming interfaces: emacs, sqlcl …also see http://cas.sdss.org/astro/en/help/docs/api.asp Strict limits on execution time and output size … always test-drive your query (‘quick’ or ‘top 100’)!
7	Navigating SkyServer Major sections linked from main page http://cas.sdss.org/astro/
8	Cooking with Sloan website tutorials http://cas.sdss.org/astro/en/help/cooking/ How do I get an image, spectrum, and other info for my favorite object in the SDSS area? http://cas.sdss.org/astro/en/help/cooking/general/getimage.asp Are the SDSS data for a given object reliable? Consult the object’s flags to find out. http://cas.sdss.org/astro/en/help/cooking/general/flags.asp
9	Searching for data meeting certain criteria Search for data that meets certain criteria Return matching data, and only matching data Example: search for galaxies with spectra in Abell 168 RA = 18.84, Dec = 0.26, radius = 3 arcmin Limit to galaxies g < 18 Return RA, Dec, magnitudes, redshift
10	Query with Imaging Constraints http://cas.sdss.org/astro/en/tools/search/IQS.asp Tools -> Imaging Query Constraints by position or imaging Get data as HTML or CSV For actual images, save as CSV & upload to DAS retrieval form
11	SQL SQL – computer language for searching databases Advantages You get longer queries and more results returned You can write more complex queries You can use command-line tools
12	SQL Concepts Data are stored in a database Similar data types are stored in tables: photoObj (photometry), specObj (spectroscopy), etc. A request to a database to return data is called a query Queries usually request data that meets certain constraints
13	SQL as a foreign language Languages have grammar and vocabulary Dutch grammar In sub-clause, verb goes at the end English: I think that astronomy is fun. Dutch: Ik denk dat het sterrenkunde leuk is.
14	SQL Grammar Select – choose which columns of data you want to see From – choose the table(s) from which you want to retrieve data Where – set constraints on the search
15	SQL vocabulary Go to Help -> Schema Browser http://cas.sdss.org/astro/en/help/browser/browser.asp
16	Learning SQL Go to Help -> Sample SQL Queries Go to Search Tools -> SQL Search Copy, paste, modify
17	Visual search results http://cas.sdss.org/dr5/en/tools/chart/list.asp Go to Advanced Tools -> Image List ‘Use query to fill form’ Query must have: select x, ra, dec from … [where …]
18	CasJobs Go to Search Tools -> CasJobs Best method for long or complex queries
19	CasJobs Register and log in Quick mode: 1 minute Submit: 24 hours Results stored in MyDB
20	CasJobs: other features MyDB database to save results of your queries Define your own functions, procedures too Share your tables with collaborators (groups) History of Output data as FITS/CSV/VOTable Plot data in browser Table Import (upload) for your own data Groups to share your results with collaborators Command-line access Java tool also downloadable
21	CasJobs help Shares SQL Intro, Schema Browser with SkyServer Has its own FAQ page Lists differences between CasJobs and SkyServer due to distributed query execution Advanced CasJobs Queries page Neighbor searches with fixed and variable search radii Cursors Compound queries
22	CAS Dos and Don’ts Do not submit a query unless you have some idea how long it will take! It could tie up the server for hours (even days)! Use “select count(*)” or “select top 10” instead Or try “quick” first, to see if it can be done quickly Do use predefined views for commonly-used objects and parameters PhotoObj, PhotoPrimary for photometry PhotoTag if you only need popular fields SpecObj for spectra
23	SkyServer help Schema Browser FAQ Glossary – of SDSS terms Algorithms Helpdesk (use contact link, not direct e-mail)
24	Educational Resources Extensive education content in SkyServer Use Projects link on the menu at the top K-12 and college level student exercises and teacher resources Go to public site – http://cas.sdss.org Go to Projects Great as labs for intro classes
25	I want specific objects When you want to browse images, or when you know a position… ToolsÞVisual ToolsÞ Find images and data: Navigate Browse objects one at a time: Explore Find objects on a frame, compare your own observations: Finding Chart View multiple objects or thumbnail search results: Image List
26	I want a class of objects When you don’t know specific objects… ToolsÞSearchÞ Find objects in a patch of sky: Radial or Rectangular Simple search for imaging data: Imaging Query Form Simple search for spectral data: Spectro Query form More sophisticated searches: SQL Long, complex queries: CasJobs
27	What does SDSS know about my objects? When you have a list of objects, and you want to see what SDSS knows about them… ToolsÞObject CrossidÞ Imaging crossid: Upload Spectro crossid: SpecList
28	References & Tutorials When in doubt, consult website or publications: http://www.sdss.org/publications/#technical http://www.sdss.org/publications/#data%20release … especially EDR paper (Stoughton et al) The SDSS can function as a data pipeline, but not as a science pipeline. You will have to decide what magnitudes are best for your science, what flag values to use to accept or reject objects, etc. Try the queries on the next few pages, or at http://cas.sdss.org/astro/en/help/cooking/