Mosaic Imaging and 3D Distance Vectors NGC 4088 and NGC 4085 – Interacting Galaxies Chelsea Braun...
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Transcript of Mosaic Imaging and 3D Distance Vectors NGC 4088 and NGC 4085 – Interacting Galaxies Chelsea Braun...
Mosaic Imaging and 3D Distance Vectors
NGC 4088 and NGC 4085 – Interacting GalaxiesChelsea Braun
Image: Digitized Sky Survey
North: upEast: Left
OutlineIntroductionTheoryMosaic Image PlanCreating the ImagesFinal ImageDistance CalculationDiscussion
Image: Jeff Johnson, croppedhttp://jeffjastro.com/dso/NGC4088_30Jan09.htm
North: upEast: Left
IntroductionNGC 4088 is a weakly barred spiral galaxy
with morphological type SAB(rs)bcNGC 4085 is an Sc D galaxyFound in the Ursa Major constellationPart of the M109 group
Image: StellariumCredit: Simbad
North: upEast: Left
TheoryThe 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
Geometry
Distance4 equations
Where the distance to the galaxies, d1 and d2,
can be determined using arcmins, is determined from the image with scale, S
ImagingSpent a night collecting 1hr
30mins of data30 mins for 3 7’x7’ imagesDifficulties?
◦Telescope moved a lot◦Provided difficulties when combining
the images
Mosaic Image PlanTake three 7’x7’ images, 30 mins at 60sec
exposuresNorth up and East right (for all images)Have common stars in each image to line
up the images
NGC 4088 MID NGC 4085Image: Digitized Sky Survey
North: upEast: Left
Mosaic Image Plan
Image: Digitized Sky Survey
15’x7’
North: upEast: Left
NGC 408830 images at 60sec exposures, 7’x7’
image◦Calibrated the images
Broke into 2 subgroups: 1-9, 10-30
North: upEast: Left
NGC 4088North: upEast: Left
NGC 4088Final NGC 4088 imageCombine the final averaged
images from the substacks into 1 stack
Register themCombine
North: upEast: Left
NGC 4088
Image: 6.7’x5.2’
North: upEast: Left
MID30 images at 60 second exposures,
7’x7’ imagesThe 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 1Most 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 1Slide 6
Slide 15
North: upEast: Left
Substack 1Crop all the manually registered
images and place in a stack◦PROBLEM: slight rotation in the
TurboReg plugin caused a very noisy averaged image
Substack 1North: upEast: Left
Substack 1North: upEast: Left
Substack 2 & 3 Final Images
North: upEast: Left
Mid – Final Image
Image: 6.5’ x 5.5’
North: upEast: Left
NGC 408530 images at 60 second exposures,
7’x7’No substacks neededAlthough 2 registrations were
necessary to align the images
NGC 4085 – Final ImageImage: 6.7’x5.8’
North: upEast: Left
Background LevelsBackground levels were matched to
create the mosaicMeasured the background levels of
the 3 final imagesTook the darkest background level
and matched them into the other images ◦Subtracted the differences in
background levels
North: upEast: Left
Background LevelsImage 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
Final Image
Image: 16.8’ x 7.6’
North: upEast: Left
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
Distance Between Galaxies
Using the 4 equations
Darcmins = 12.2' ± 0.4'Drads = 0.0035 ± 0.0001Dparsecs = 0.043 ± 0.001 Mpcd1-d2 = 0.33 MpcD' = 0.33 ± 0.03 Mpc
DiscussionFixing the MID image
◦Save a ROI line between stars for substack 1 and use the same length distance Should eliminate rotation?
ENDTHANKS!!!!!!
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.