CCD OBSERVING/RESEARCH PROJECT: NGC 3953 By: Ekta Patel Date: April 7 th, 2011 Instructor: J. West Course No: PHYS 2070 (NOAO, 2005)

 Basic Info  My Images  Image Comparison  Research Area  Repeated Calculation  Focus Area Table of ContentsTable of Contents

Basic Information Basic Information (Stellarium, 2010) Barred spiral galaxy Located 46 million light years away Magnitude: 10.1 Angular Size: 6’36” Coordinates (Jan 1, 23:00) (Stellarium, 2010) RA: 11 h 54 m 22.0s DE: +52 D 16’ 20” Rising earlier each night between January – March (our observing period) Best month is April Located in constellation Ursa Major Use one of the stars from the constellation as a guide star Member of the M109 Group of galaxies Over 50 galaxies Two supernovae have gone off in past decade SN 2001 dp (Type Ia) SN 2006 bp (Type II) (Moromisato, 2011)

Image ComparisonImage Comparison GAO Image STSciI DSS Image Date/Time May 7th, 1991/ 4:17:00 Location Latitude: Longitude: Telescope UsedOschin Schmidt - D Detector UsedPhotographic Plate FilterRG610 Exposure Time72 minutes Field of View7.0’ x 7.0’ Date/Time Feb 8, 2011/ 22:05:00 Location Latitude: min 43 s Longitude: 97 d, 7min, 20 s Telescope UsedEvans 40 cm Detector UsedApogee U47 Exposure Time33 minutes Field of View7.0’ x 7.0’

Image ProcessingImage Processing

Background InformationBackground Information Structural symmetry specifically in spiral arms of face-on spiral galaxies. Symmetry: “The quality of being made up of exactly similar parts facing each other or around an axis.” (Oxford American Dictionary, 2010) Asymmetry: “The lack of equivalence between parts or aspects of something; lack of symmetry.” (Oxford American Dictionary, 2010) General assumption: face-on spiral galaxies are mainly axi-symmetric (Foresman, 2007)

Background InformationBackground Information Fourier techniques show deviations in symmetry exist for spiral galaxies. (Zarisky, 1995) Use of symmetry of spiral arms as a morphological indicator: started by Elmegreen and Elmegreen in 1982  “symmetric images of galaxies …allowed for underlying spiral structure to be examined closely…revealed many spirals have hidden features (ie: triple arm patterns)” (Conselice, 2007) Classification of galaxies includes high redshifted galaxies (ie: those seen in HDS telescope images)  regular classification is not sufficient because they galaxies are faint and irregular. solution 1: automated classification through computer models to assign galaxies classical morphological types solution 2: use structural symmetry measurements for classification First we must study its usefulness and examine limitations on nearby galaxies (Conselice, 1997)

Research Paper “The Symmetry, Color, and Morphology of Galaxies” Christopher J. Conselice 1997 Research Topic : What symmetry in a galaxy can imply. Objects Studied: 35 face-on spiral (early, intermediate and late types) 8 elliptical selected from the public FTP site of galaxy images large, nearby with high-surface brightness various morphologies Images in R (650 nm) and J (450 nm) bands used 1.1 m Hall Lowell Obs (March 24-April ) CCD camera: 320 X 512 pixel RCA 30 min exposures for R band 45 min exposure for J band (Conselice, 1997)

Research Paper “The Symmetry, Color, and Morphology of Galaxies” Christopher J. Conselice 1997 Method: 1.Subtract background stars + sky background 2.Rotate 180 degrees about the center point (brightest region in the middle) 3.Subtract rotated image from original 4.Square the pixels in residual image 5.Divide the sum of pixels in residual image by 2 times the sum of the squared pixels of original image Equation: A=0 Perfectly symmetric A=1 Completely asymmetric

Research Paper “The Symmetry, Color, and Morphology of Galaxies” Christopher J. Conselice 1997 Potential Limitations: Distant galaxies have lower resolution Closer galaxies have higher resolution Are these limitations present? plot of symmetry vs. distance slight distance effect is noticed thus, caution should be used when applying this method to galaxies in different red-shift ranges (Conselice, 1997)

Research Paper “The Symmetry, Color, and Morphology of Galaxies” Christopher J. Conselice 1997 Results: J band images are more asymmetic on average than R band Most galaxies were found to be not extremely asymmetric NGC 3953 was right in the middle  average asymmetry Strong correlation between asymmetry and morphological types: Low #’s = early system High #’s = late-type system Trend noticeable between Hubble morphology & sym. As galaxies reach later- type spirals, asymmetry increases. Suggests, Hubble Sequence is on increasing optical asymmetry. (Conselice, 1997) (Conselice, 2007)

Research Paper “The Symmetry, Color, and Morphology of Galaxies” Christopher J. Conselice 1997 Symmetry colour plot has a strong correlation Thus degree of symmetry can be used to measure global stellar populations within a galaxy. asymmetric galaxies have stellar populations that are blue  recently formed massive young stars. Due to patchy star formation throughout the disk older stellar populations are smoothed out through time, thus more symmetric Global asymmetries affect R and J bands equally Asymmetries are causes by recently formed stars, thus can be used to measure star formation rate. (Conselice, 1997)

Research Paper Findings “The Symmetry, Color, and Morphology of Galaxies” Christopher J. Conselice 1997 Conclusions: Strong correlation between asymmetry and colour  useful for finding one, when other is unknown Using symmetry, physical parameters of galaxies which otherwise would not be measureable are reasonably estimated. Limited, but powerful for morphological and physical information of a galaxy.

NGC 3953 MeasurementsNGC 3953 Measurements Original Image: Background & Star Subtracted Background Subtracted & Star Subtracted + Flipped 180 o SUBTRACT

NGC 3953 MeasurementsNGC 3953 Measurements Result of Subtraction

NGC 3953 MeasurementsNGC 3953 Measurements 2 X (Original Image) 2 (Result of Subtraction) 2 DIVIDE

NGC 3953 MeasurementsNGC 3953 Measurements Calculations: A 2 = (73563 x )/ 2(73563 x ) A=0.20 (for 550 nm) Sources of Error: different wavelengths are being compared Star subtraction method was not perfect Background subtraction method was not 100% perfect

Focus Area: Colour Processing Techniques 1.GIMP/Photoshop – levels adjustment (method from class) 2.GIMP Colourize Tool– playing with hue/saturation 3.Stack to RGB 4.LUT RGB Composer Plugin NOTE: All of the following images are taken from Sloan Digital Sky Survey. Filters: Ultraviolet (u), Green (g), Red (r), Near Infrared (i), Infrared (z) Corresponding Wavelength (Angstroms): 3543, 4770, 6231, 7624, 9134

Level Control in GIMPLevel Control in GIMP Advantages: Highest control Disadvantage: Time consuming & multiple steps

Level Control in GIMPLevel Control in GIMP

Colourize ToolColourize Tool Uses GIMP/Photo Shop Disadvantage: Less control Advantage: Simple and Quick

Colourize ToolColourize Tool

Stack to RGBStack to RGB Open stake of 3 grey-scale images Convert to 8-bit Image  Colour  Stack to RGB

Stack to RGBStack to RGB

LUT Panel 2.2LUT Panel 2.2 Up to 3 gray-scale images Each image can have multiple colors assigned

LUT Panel 2.2LUT Panel 2.2

RGB Composer PluginRGB Composer Plugin Works for up to 3 gray-scale images Simple & easy to use. Take only a few minutes!

RGB Composer PluginRGB Composer Plugin

My ImagesMy Images RGB Composer Plug-InGIMP Level ControlsStack To RGB LUT Panel 2.2Colour Processor ToolStack To RGB

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 Conselice C The Symmetry, Color, and Morphology of Galaxies : Astronomical Society of the Pacific Haynes G, Haynes Best of AOP: NGC 3953: T. Moromisato G NGC This research has made use of the SIMBAD database, operated at CDS, Strasbourg, France.