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Mosaic Imaging and 3D Distance Vectors

North: up East: Left. Mosaic Imaging and 3D Distance Vectors. NGC 4088 and NGC 4085 – Interacting Galaxies Chelsea Braun. Image: Digitized Sky Survey. North: up East: Left. Outline. Introduction Theory Mosaic Image Plan Creating the Images Final Image Distance Calculation

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Mosaic Imaging and 3D Distance Vectors

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  1. North: up East: Left Mosaic Imaging and 3D Distance Vectors NGC 4088 and NGC 4085 – Interacting Galaxies Chelsea Braun Image: Digitized Sky Survey

  2. North: up East: Left Outline • Introduction • Theory • Mosaic Image Plan • Creating the Images • Final Image • Distance Calculation • Discussion Image: Jeff Johnson, croppedhttp://jeffjastro.com/dso/NGC4088_30Jan09.htm

  3. North: up East: Left Introduction • NGC 4088 is a weakly barred spiral galaxy with morphological type SAB(rs)bc • NGC 4085 is an Sc D galaxy • Found in the Ursa Major constellation • Part of the M109 group Image: Stellarium Credit: Simbad

  4. Theory • The 3D distance vector • Calculating the distance between 2 galaxies • Not as simple as finding the distance in arc seconds on an image and then converting to parsecs • Requires knowing the distance to these objects

  5. Geometry

  6. Distance • 4 equations • Where the distance to the galaxies, d1 and d2, can be determined using arcmins, is determined from the image with scale, S

  7. Imaging • Spent a night collecting 1hr 30mins of data • 30 mins for 3 7’x7’ images • Difficulties? • Telescope moved a lot • Provided difficulties when combining the images

  8. North: up East: Left Mosaic Image Plan • Take three 7’x7’ images, 30 mins at 60sec exposures • North up and East right (for all images) • Have common stars in each image to line up the images NGC 4088 MID NGC 4085 Image: Digitized Sky Survey

  9. North: up East: Left Mosaic Image Plan 15’x7’ Image: Digitized Sky Survey

  10. North: up East: Left NGC 4088 • 30 images at 60sec exposures, 7’x7’ image • Calibrated the images • Broke into 2 subgroups: 1-9, 10-30

  11. North: up East: Left NGC 4088

  12. North: up East: Left NGC 4088 • Final NGC 4088 image • Combine the final averaged images from the substacks into 1 stack • Register them • Combine

  13. North: up East: Left NGC 4088 Image: 6.7’x5.2’

  14. MID • 30 images at 60 second exposures, 7’x7’ images • The middle star image had the most difficulties • Most noise • First 5 frames removed (guide stars missing) • Broken down into 3 substacks: • Substack 1: 6-15 • Substack 2:16-21 • Substack 3: 22-30

  15. Substack 1 • Most difficult to register • done for the 10 frames using TurboReg: scaled rotation • Pick 2 points on 2 different images • Aligns those 2 points using translation and rotation • Rotation is a bad thing

  16. North: up East: Left Substack 1 Slide 15 Slide 6

  17. Substack 1 • Crop all the manually registered images and place in a stack • PROBLEM: slight rotation in the TurboRegplugin caused a very noisy averaged image

  18. North: up East: Left Substack 1

  19. North: up East: Left Substack 1

  20. North: up East: Left Substack 2 & 3 Final Images

  21. North: up East: Left Mid – Final Image Image: 6.5’ x 5.5’

  22. NGC 4085 • 30 images at 60 second exposures, 7’x7’ • No substacks needed • Although 2 registrations were necessary to align the images

  23. Image: 6.7’x5.8’ NGC 4085 – Final Image North: up East: Left

  24. Background Levels • Background levels were matched to create the mosaic • Measured the background levels of the 3 final images • Took the darkest background level and matched them into the other images • Subtracted the differences in background levels

  25. North: up East: Left

  26. Background Levels • Convert to 16 bit to use MosaicJ • Find the minimum and maximum pixel values for all three images and set the B & C min and max to these values over all 3 images • Then convert to 16 bit

  27. North: up East: Left Final Image Image: 16.8’ x 7.6’

  28. Distance Between Galaxies • Measured a distance of 894.79 pixels between galaxies

  29. Distance Between Galaxies • Using the 4 equations • Darcmins= 12.2' ± 0.4' • Drads = 0.0035 ± 0.0001 • Dparsecs = 0.043 ± 0.001 Mpc • d1-d2 = 0.33 Mpc • D' = 0.33 ± 0.03 Mpc

  30. Discussion • Fixing the MID image • Save a ROI line between stars for substack 1 and use the same length distance • Should eliminate rotation?

  31. END • THANKS!!!!!!

  32. References • Association of Universities for Research in Astronomy, Inc. 1994. The Digitized Sky Survey http://stdatu.stsci.edu/cgi-bin/dss_form • Chereau F, Gates M, Kerr N, Marcos D, Marinov B. et al. 2010. Stellarium • Goldman, D. (2008). NGC 4088 in UMa. Last accessed 15th Nov. <http://dg-imaging.astrodon.com/gallery/display.cfm?imgID=135> • This research has made use of the SIMBAD database, operated at CDS, Strasbourg, France. 

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