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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

North: up

East: Left

Mosaic Imaging and 3D Distance Vectors

NGC 4088 and NGC 4085 – Interacting Galaxies

Chelsea Braun

Image: Digitized Sky Survey

outline

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

introduction

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

theory
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
distance
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

imaging
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
mosaic image plan

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

mosaic image plan1

North: up

East: Left

Mosaic Image Plan

15’x7’

Image: Digitized Sky Survey

ngc 4088

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
ngc 40882

North: up

East: Left

NGC 4088
  • Final NGC 4088 image
  • Combine the final averaged images from the substacks into 1 stack
  • Register them
  • Combine
ngc 40883

North: up

East: Left

NGC 4088

Image: 6.7’x5.2’

slide14
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
substack 1
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
substack 11

North: up

East: Left

Substack 1

Slide 15

Slide 6

substack 12
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
mid final image

North: up

East: Left

Mid – Final Image

Image:

6.5’ x 5.5’

ngc 4085
NGC 4085
  • 30 images at 60 second exposures, 7’x7’
  • No substacks needed
  • Although 2 registrations were necessary to align the images
background levels
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
slide25

North: up

East: Left

background levels1
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
final image

North: up

East: Left

Final Image

Image: 16.8’ x 7.6’

distance between galaxies
Distance Between Galaxies
  • Measured a distance of 894.79 pixels between galaxies
distance between galaxies1
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
discussion
Discussion
  • Fixing the MID image
    • Save a ROI line between stars for substack 1 and use the same length distance
      • Should eliminate rotation?
slide31
END
  • THANKS!!!!!!
references
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.