Using Data from the Sloan Digital Sky Survey In the Classroom Jordan Raddick (Johns Hopkins University) Visualization of Astrophysical Data workshop Kavli Institute for Cosmological Physics May 25, 2005

Goals of the SDSS Map sky down from ~9 th to ~23 rd magnitude Images in 5 color bands form 3800Å to 9200Å Obtain spectra for 1 million galaxies and 100,000 quasars Create a detailed 3D map of the universe

The Telescope 2.5 meter F/5 reflector Very wide (~3 degree) field of view Alt-az mount Drift scanning

The Spectrographs Two fiber-fed spectrographs Each can record 320 spectra simultaneously (640 total) Determine redshifts, spectral types, chemical compositions

The Data of the SDSS Photometric Data Spectroscopic Data

Photometric Data Tri-color images (g-r-i images) FITS files (single-wavelength B/W images) Magnitudes through each filter Object type (star or galaxy) Status (i.e. good seeing, cosmic rays, etc.) Flags (i.e. saturated pixels, moving object, etc) Photometric redshifts

Spectral Data Moderate resolution (~1.3 Angstroms/pixel) from 3800 to 9200 Angstroms GIF files with prominent lines marked FITS files available Detailed line widths and strengths

Online Access to the Data All data will be made available online, free New data added in six chunks Currently Data Release 3 –Released October 2004

Introduction to SkyServer Data Release 3 (DR3) SkyServer

Introduction to DR3 ~5,200 square degrees –(Full moon is 0.25 square degrees) Images of ~140 million objects –~60 million stars ~350,000 spectra –~46,000 quasar spectra Science quality data Where in the sky?

DR3 Imaging Coverage (Aitoff projection of equitorial coordinates)

DR3 Spectral Coverage (Aitoff projection of equitorial coordinates)

SkyServer A public interface to SDSS data Servers donated by Hewlett-Packard Software, expertise donated by Microsoft –Jim Gray, Curtis Wong

SkyServer Funds from –NSF –STSci (IDEAS grant) –Maryland Space Grant First light: 6/4/2001

Goals for SkyServer Make high-quality astronomy data available to everyone –Create easy-to-use tools to access data Allow amateurs to conduct professional- quality research Promote the use of real science data in the classroom

SkyServer Tools Simple tools for accessing data Focus often on single objects Prioritize information –First listed should be most important Most tools are web service-based –Work should be done on server Most written by A. Szalay et al at JHU

Example: Navigation tool Main window: Displays images Data Close up Change RA/Dec Display Options Controls

SkyServer Projects Make the data useful in formal ed settings Teach specific topics, tied to curriculum –Broader than just astronomy (e.g. spectra in chemistry) Need clear logic for student to follow Make it as easy as possible for teachers Written by J. Raddick (science writer) and R. Sparks (high school teacher)

Example: Scavenger Hunt Students go on a scavenger hunt of sky Find stars, galaxies, quasars, meteor trails Look for specific magnitudes Introduces students to SkyServer tools Teaches night sky objects, quantitative reasoning

Scavenger Hunt Teacher Notes Lesson Plan –Goals –Prerequisites –Vocabulary –Procedure Background reading Assessment –Sample solutions (password protected) –Rubrics

Scavenger Hunt Teacher Notes Correlated to Teaching Standards –National Science Education Standards –AAAS Project 2061 –NCTM (Mathematics) –NETS Indicators (Technology Ed)

Current & Future Work Combining SkyServer with other projects –Hands-On Universe for follow-up observations –NU Collaboratory for online mentoring and collaboration Apply same design methods to National Virtual Observatory (NVO) education

Contact Information Jordan Raddick (410)

The rest of this presentation… Is adapted from a SkyServer workshop from an AAPT meeting Gives more detail about how to use SkyServer

Retrieving Data with SkyServer A.Navigation Tool B.Explore Tool C.Get Spectra and Get Plates

Pan and zoom through the sky Click on star/galaxy for summary of photo data Online notebook to save objects Create telescope finding charts Navigation Tool

Information on single objects –Photometric and spectroscopic Look up by object ID, position, Correlations to data from other sky surveys Object Explorer

Search by – various methods to search for objects (ID, RA/Dec, Spectrum Nos.) Summary – general photo and spectral info PhotoObj – photometric data Field – statistical data for a region of sky Frame – JPEG images and their parameters PhotoZ – photometric redshifts Neighbors – list of objects within 0.5 arcminutes Navigate – link to Navigation tool FITS – download raw images (FITS) continued

Object Explorer SpecObj – measured parameters for a spectrum SpecLine – information on individual lines SpecLineIndex – line intensities used to find properties of galaxies XCRedShift – Cross-correlation redshifts ELRedShift – emission line redshifts Spectrum – GIF of spectrum Plate – information on plate that contains the spectrum FITS – raw (FITS) file of the spectrum continued

Object Explorer NED Search – searches for object in NASA Extragalactic Database (NED) Virtual Sky – searches data at Save in Notes – saves object to online notebook Show Notes – Shows objects in your notebook Print Page – prints the current display

Getting Raw Images from Object Explorer Click “PhotoObj -> FITS” “Corrected Frames” are final images One-wavelength, black/white Zipped files –Extension.fts.gz –Use WinZip to extract single.fts file

Searching the Data A.Radial Search B.Rectangular Search C.SQL Search D.Schema Browser E.Image List

Radial Search Search around specified coordinates Input ra, dec, radius Can apply magnitude cuts for all five filters (optional) Can retrieve data in HTML, XML, or CSV files –CSV files can be opened by most spreadsheet programs 1,000 object limit continued

Radial Search Example: search for Objects in galaxy cluster Abell 168 (from Famous Places)

Notes About the Results ObjID, run, rerun, camcol, field and obj can be used to look up data in the Object Explorer or Get Fields Obj Type: 3 = galaxy, 6 = star Err_u, etc, are uncertainties in magnitudes

Rectangular Search Similar to radial search Search area is a rectangular box continued

Rectangular Search Example : Search for objects near Abell 0957 Select CSV for format continued

Rectangular Search (cont) To save as a.csv file –Click the File menu and select “Save As” –Click “Save as type” and select text –Type a file name such as Abell0957.csv –Click Save continued

Rectangular Search To open a.csv file Use Excel’s “Text Import Wizard” Open Excel From the Data menu,select Get External Data -> Import Text File

Rectangular Search Select “Delimited,” then “Comma” Change any objid columns to “Text” This preserves all 18 digits of Object IDs

SQL Search What if you want to search for specific objects in the database? Example: show me all bright blue galaxies Database can return all bright blue galaxies and only bright blue galaxies! How? SQL! Incredibly powerful and flexible interface continued

SQL Search SQL – Structured Query Language –Common database access language –Industry standard, so students have practical advantages to learning Allows advanced searches (“queries”) of data Search using constraints on any variable Return any or all types of data

How to Learn SQL Go to Help -> How-To -> Searching for Data Interactive tutorial on SQL

Image List tool Go to Tools -> Visual Tools -> Image List Click “Use query to fill form” Enter query and click Submit

Image List tool Results appear in window Click “Send to List”

Image List tool Thumbnail for each query result Click any thumbnail to go to Navigation tool

Example: Stellar Evolution Adapted from Projects -> Advanced -> H-R Diagram How do stars change over time? You can’t watch a star age –Stars live for billions of years! So how can you learn?

Example: Stellar Evolution Solution: study lots of stars –Large statistical sample –Stars at all stages of life What properties to observe? –Temperature –Luminosity (brightness)

Temperature and Color Stars emit thermal (“blackbody”) radiation –Hotter stars have a shorter peak wavelength –Shorter wavelength = bluer How do you quantify “blueness”? A star with temperature 4000 K [peak wavelength in blue]

Temperature and Color Take picture of star in two filters –Such as g and r Ratio of bright- nesses shows up Magnitude is logarithmic, so take difference in magnitudes –Such as g-r

Temperature and Color Difference in magnitudes is “color” –Astronomical definition Color is a stand-in for temperature

Luminosity and Magnitude Luminosity: how much light the star emits [Apparent] Magnitude: how much light gets to Earth –Measured in specific wavelength –Logarithmic scale –Backwards (brighter stars, lower magnitudes) –Depends on distance (farther stars tend to look fainter)

Luminosity and Magnitude Problem –If you see a faint star, how do you know if it’s really faint, or just far away? Solution –Look at star clusters –Nearly same distance from Earth, so… –Faint cluster stars really are faint –Magnitude can substitute for luminosity

The H-R Diagram Temperature vs. luminosity is “H-R Diagram” –After discoverers, Hertzsprung and Russell –Temp on x-axis, luminosity on y –For us, color on x-axis, magnitude on y

The H-R Diagram 4 groups: 1) Main sequence –Like the Sun –Center of graph –More mass- ive stars on left top

The H-R Diagram 2) Red giants –Middle right –Older stars 3) Super- giants –“Horizontal branch” at top –Older, more massive stars

The H-R Diagram 4) White dwarfs –Bottom left –Very old, small, cool

The H-R Diagram H-R diagram maps stellar evolution –Main sequence -> Red Giant / Supergiant -> White Dwarf (for stars < 5-ish Solar Mass) Explained by physics of fusion

Our Star Cluster: Palomar 5 Globular cluster – old star cluster just outside our galaxy Famous cluster Palomar 5 (“Pal 5”) Discovered in 1950s by Palomar Observatory Sky Survey (POSS) –Palomar Observatory near San Diego –Biggest optical sky survey until SDSS

Pal 5 from the Palomar Sky Survey

Pal 5 from the SDSS

Palomar 5 Activity Open the Navigation tool Go to Palomar 5 coordinates –RA = ;Dec = Click on stars –Bright and faint Record g and r magnitudes Graph g-r (x-axis) vs. r (y-axis) Take about 15 minutes to do this

Sample H-R Diagram Yours will probably look different!

An Easier H-R Diagram Wasn’t that hard and labor-intensive? Easier way: SQL!!!! Open SQL Search tool Write a query –Hint: did you learn the function fGetNearbyObjEQ() ? fGetNearbyObjEQ() Save results, open in Excel Make a new H-R Diagram (g-r vs. r)

H-R Diagram of Palomar 5

H-R Diagrams Side-by-side From images From query

Interpreting the H-R Diagram See the: –Main sequence –Red giants –Horizontal branch (supergiants) –White dwarfs too faint Where are big main sequence stars???

Interpreting the H-R Diagram They burned out their fuel and became red giants! “Turnoff” from main seq tells you age of cluster So how old is Palomar 5?

Interpreting the H-R Diagram Hard to tell Where is turnoff? Somewhere between g-r = 0.25 and 0.4 Leads to an age of 1-5 billion years –See palomar5.doc to learn why

Interpreting the H-R Diagram Recent (Jan. 2003) age estimate for Palomar 5 –10-12 billion years –From Hubble data Why the difference? –Large data scatter –Foreground/background stars? –H-R is one of many age techniques

Interpreting the H-R Diagram But, you’ve learned something valuable –Cluster is a few billion years old –(not millions or 100s of billions) And, you’ve done real science! –Same data professionals use –Similar analysis –Valuable conclusions Can you think of extensions? –Could be good science fair projects

VII. Student Projects with SDSS Data A. Projects on SkyServer B.Examples of Student Lessons C.Create Your Own (Research!)

SkyServer Projects We have class-ready lesson plans online –SkyServer projects –All that you did today were [adapted] Projects!

SkyServer Projects Under “Projects” link of main page All projects use SDSS data extensively Most projects use inquiry-based learning Student activities –Questions –Exercises continued

SkyServer Projects Teachers’ Guides for all projects Goals, background knowledge, structure Advice on leading class through project Sample solutions and rubrics Correlations to standards –AAAS Project 2061 –NCTM Principles and Standards continued

Teacher’s Guides Go to Projects main page (I’ll show you) Click “ Register as a SkyServer teacher” Fill out form –If you forget school address, make one up –You can update later –We don’t verify with your school… we just say that to scare your students Tomorrow, you will be able to access sample solutions

Teacher’s Guides Click on “ See the Teacher’s Guides” Look through teacher’s guides Many projects are long, but you can do parts of them –For example, Thermal Radiation Curves in the Color projects

Create Your Own Projects Now you know how to use the site Appropriate topics might include: galaxy classification, asteroids, large-scale structure, spectroscopy, the Hubble Diagram, Image processing, Colors, Spectral Types of Stars and many others Be creative – the sky’s the limit! Additional resources on CD Let us know what you do!

Formal Evaluation We are beginning evaluation program Tell me what projects you will use I’ll send you copies of –Student/teacher surveys –Pre/post-tests I’ll include postage – mail them back 7 classes so far… results look good, but we need more data! Let me know if you can help

You’ve been a great audience! Let us know how you use SkyServer Send comments and suggestions Looking for test classes –Surveys and pre/post-tests –We’ll send you free SDSS stuff Jordan Raddick –(410)