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 Discussion Image: Jeff Johnson, cropped 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 North: up East: Left

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

Geometry

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

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 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

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

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

NGC 4088 North: up East: Left

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

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

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 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 1 Slide 6Slide 15 North: up East: Left

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

Substack 1 North: up East: Left

Substack 1 North: up East: Left

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

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

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

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

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

North: up East: Left

Background Levels ImageBackground LevelDifference NGC MID NGC 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: up East: Left

Distance Between Galaxies Measured a distance of pixels between galaxies VariableValueError d 1 distance to NGC MpcGiven d 2 distance to NGC MpcGiven D pixels±8 pixels S, image scale arcmins/pixel± arcmins/pixel

Distance Between Galaxies Using the 4 equations D arcmins = 12.2' ± 0.4' D rads = ± D parsecs = ± Mpc d 1 -d 2 = 0.33 Mpc D' = 0.33 ± 0.03 Mpc

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

END THANKS!!!!!!

References Association of Universities for Research in Astronomy, Inc The Digitized Sky Survey Chereau F, Gates M, Kerr N, Marcos D, Marinov B. et al 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.