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

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

3. 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 North: up East: Left

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, d 1 and d 2, 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. 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 4088MIDNGC 4085 Image: Digitized Sky Survey North: up East: Left

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

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

11. NGC 4088 North: up East: Left

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

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

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

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

18. Substack 1 North: up East: Left

19. Substack 1 North: up East: Left

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

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

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

23. NGC 4085 – Final Image Image: 6.7’x5.8’ 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 ImageBackground LevelDifference NGC 40881060.860 MID1109.7748.91 NGC 40851170.32109.46 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. Final Image Image: 16.8’ x 7.6’ North: up East: Left

28. Distance Between Galaxies Measured a distance of 894.79 pixels between galaxies VariableValueError d 1 distance to NGC 4088 12.22 MpcGiven d 2 distance to NGC 4085 12.55 MpcGiven D894.79 pixels±8 pixels S, image scale0.0136 arcmins/pixel± 0.0003 arcmins/pixel

29. Distance Between Galaxies Using the 4 equations D arcmins = 12.2' ± 0.4' D rads = 0.0035 ± 0.0001 D parsecs = 0.043 ± 0.001 Mpc d 1 -d 2 = 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. This research has made use of the SIMBAD database, operated at CDS, Strasbourg, France.