Mosaic Imaging and 3D Distance Vectors

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Mosaic Imaging and 3D Distance Vectors
North up East Left

• NGC 4088 and NGC 4085 Interacting Galaxies
• Chelsea Braun

Image Digitized Sky Survey
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Outline
North up East Left

• Introduction
• Theory
• Mosaic Image Plan
• Creating the Images
• Final Image
• Distance Calculation
• Discussion

Image Jeff Johnson, croppedhttp//jeffjastro.com
/dso/NGC4088_30Jan09.htm
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Introduction
North up East Left

• 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
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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

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Geometry
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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

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Imaging

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

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Mosaic Image Plan
North up East Left

• Take three 7x7 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
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Mosaic Image Plan
North up East Left
15x7
Image Digitized Sky Survey
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NGC 4088
North up East Left

• 30 images at 60sec exposures, 7x7 image
• Calibrated the images
• Broke into 2 subgroups 1-9, 10-30

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NGC 4088
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NGC 4088
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• Final NGC 4088 image
• Combine the final averaged images from the
  substacks into 1 stack
• Register them
• Combine

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NGC 4088
North up East Left
Image 6.7x5.2
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MID

• 30 images at 60 second exposures, 7x7 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 216-21
• Substack 3 22-30

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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

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Substack 1
North up East Left
Slide 6
Slide 15
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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

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Substack 1
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Substack 1
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Substack 2 3 Final Images
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Mid Final Image
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Image 6.5 x 5.5
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NGC 4085

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

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NGC 4085 Final Image
Image 6.7x5.8
North up East Left
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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

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North up East Left
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Background Levels
Image Background Level Difference
NGC 4088 1060.86 0
MID 1109.77 48.91
NGC 4085 1170.32 109.46

• 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

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Final Image
North up East Left
Image 16.8 x 7.6
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Distance Between Galaxies

• Measured a distance of 894.79 pixels between
  galaxies

Variable Value Error
d1 distance to NGC 4088 12.22 Mpc Given
d2 distance to NGC 4085 12.55 Mpc Given
D 894.79 pixels 8 pixels
S, image scale 0.0136 arcmins/pixel 0.0003 arcmins/pixel
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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

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Discussion

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

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END

• THANKS!!!!!!

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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. lthttp//dg-imaging.astrodon.com
  /gallery/display.cfm?imgID135gt
• This research has made use of the SIMBAD
  database, operated at CDS, Strasbourg, France.