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Transcript for Star Formation & U/HLXs in the Cartwheel Galaxy

Slide 1:
I am Donna Young and I work with the NASA/Chandra X-Ray Center outreach office. This is an overview and introduction to the DS9 Star Formation & U/HLXs in the Cartwheel Galaxy investigation developed by the Chandra mission. For a more comprehensive introduction to the DS9 image analysis software and individual investigations, please watch the short webinar introduction at the beginning of the imaging section.

Slide 2:
The Chandra X-Ray Observatory is in an extreme orbit that ranges from 16,000 km at closest approach to Earth to more than a third of the distance to the moon. The highly inclined orbit takes 64 hours with 55 uninterrupted hours of observing time. The 2 sets of 4 nested hyperbolic/parabolic mirrors match the grazing incidence of the incoming X-Ray photons and direct them to a focal point at the end of the spacecraft. The photons are detected by one of two scientific instruments – the HRC (high resolution camera) or ACIS (advanced CCD imaging spectrometer). A high energy transmission grating is lowered into the focal plane with the ACIS and a low energy transmission grating for the HRC.

Slide 3:
The photons are detected, converted to a voltage and recorded. Every 8 hours there is a data download to the Deep Space Network (DSN) in Spain, Australia or Goldstone in Barstow, CA. The data is then transmitted through the system to Cambridge, MA where the data is analyzed by Chandra scientists. Unique to X-Ray observations and the mirror/grating/scientific instruments aboard the Chandra spacecraft, for each individual X-ray photon detected the amount of energy, the position (x-y coordinates) and time arrival are known – resulting in a high resolution analysis of the objects being observed.

Slide 4:
There is an extensive teachers guide for this investigation and an answer key, as well as both a pencil and paper version and the version that requires the use of the ds9 image analysis software. The student handout provides all the information about U/HLXs necessary for the investigation. This analysis works best with students that have already studied basic stellar evolution as they will be determining which of the bright X-ray sources might be newly formed stars. The tools learned in the Investigating the Ages of Supernova Remnants would be a good introduction to this investigation and the same types of measurements and conversions are used in both.

Slide 5:
The download instructions for the ds9 software are located at The software can be downloaded to Windows, MacOSX or Linux environments. The website also has self-guided tutorials and activities to learn how to use the software and the analysis tools. However, all the instructions are included within the Star Formation & U/HLXs in the Cartwheel Galaxy student handout, so students do not need to learn the software beforehand, or use the tutorials or activities unless the teacher requires it.

Slide 6:
Students determine the size of the bright ring of the Cartwheel Galaxy, and decide if the center contains an Active Galactic Nuclei (AGN) or not. AGNs are super active galaxies with massive black holes that have a huge effect on the structure of the entire galaxy and can initiate massive star formation.

Slide 7:
The appearance of the Cartwheel Galaxy is due to an intruder galaxy that plowed through the Cartwheel in the past. The top left image is a Hubble image and the top right image is X-Ray data from the Chandra mission. The image on the lower left is a composite of the optical and X-Ray images and the image on the lower right shows the pathway and current position of the probable intruder galaxy.

Slide 8:
Chandra X-Ray data and Hubble optical data are compared side by side to determine which of the bright areas within the galaxy are X-ray sources. The screen shots from Ds9 show three examples of how the crosshairs can be locked onto corresponding areas of brightness with both sets of data for a visual inspection. The changing table displays the coordinates and associated energy for each object. Using the results of the prior calculations of the Cartwheel, along with the location and energy of the bright areas and the table of information for different types of stars, the students then identify where new stars are forming.

Slide 9:
Students then perform a similar analysis of Arp 147, another interacting galaxy. There are several analytical questions for students to answer. References are provided for students so they can then compare their answers with published scientific papers.

Slide 10:
A task specific scoring rubric has been provided to assess student understanding and the communication of that understanding. Two more galaxies – M82 and the Antennae can also be analyzed in the same way as the Cartwheel Galaxy and Arp 147 for assessment also.

Slide 11:
The Chandra educational materials website has excellent supporting resources for multiwavelength astronomy and stellar evolution. You can request available ancillary classroom materials using the materials request form. If you have any questions, please email me.