HII Regions - Teacher's Guide
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HII Regions
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Challenge 1: A Catalog of HII regions

This challenge asks students to create a catalog of HII regions, the star forming regions of galaxies. SDSS astronomers could use such a catalog to study star formation and to test future updates of SDSS software.

Students write a query - a short computer program - to search through SDSS for objects classified as galaxies that might be HII regions. Students will have to visually examine every object to verify that it is a HII region. This challenge is best undertaken by a group of students, so they can divide up their list of potential candidates as they verify them.

Project Goals

By the end of the project, students should be able to:

  • Define an HII region and explain its importance to astronomers
  • Describe the color characteristics of an HII region and how its colors differ from the colors of a typical galaxy
  • Create SQL queries to search and retrieve information on likely HII regions
  • Sort data to find the objects most likely to be HII regions
  • Identify prominent spectral lines in HII regions
  • Create a useful catalog of astronomical objects
  • Effectively communicate how their data were collected so that others may use and refer to their catalog
  • Create and carry out a complex independent research project

Background Knowledge

Students should be familiar with the types of galaxies and with some of their characteristics. They also should be comfortable working with the SDSS color system and know about the magnitude scale. Students will need to use this knowledge to make educated guesses about the colors of HII regions. The Colors and Galaxies projects give good introductions to these concepts.

In this challenge, students will look at the spectra of candidate HII regions. They should know how to retrieve spectra from SkyServer using the Get Plates tool. Students should be familiar with spectral emission lines, since these lines are the dominant feature in the spectrum of an HII region.

Computer skills are very important for this challenge. Students will need to create SQL queries that return data that are likely to include HII regions. Students will need to know how to filter data in the "where" block of the query, and how to retrieve data from multiple tables in the same database. You may wish to work through one of the SQL tutorials so that you may answer student questions.

Students will need to know how to use SkyServer's Navigation tool and Object Explorer to look up images and Spectra of various objects. For some objects, they may wish to download the images and look at them using an image processing program such as IRIS to get a better view. See the Image Processing project for more information on how to use IRIS.

Project Structure

The first page of the student project teaches students what HII regions are. The second page describes some of the characteristics of HII regions so students can form some ideas on the best way to search the data. The third page teaches students how to query SDSS data with SkyServer's Query tool. The fourth page tells students how to tell if a candidate object is actually an HII region.

The goal of this challenge is to create a catalog of HII regions that could be used for research. SDSS astronomers just published a similar catalog of quasars from SDSS's early data release. You can see the research paper where they explain their results here. (The paper is a .pdf file, and you will need Adobe Acrobat Reader to view it. If you do not already have the reader, you can download it free from Adobe's web site.) You may wish to show this paper to students to give them an idea of what their catalogs could be used for.