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Does the Universe Have a Handedness?

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Does the Universe Have a Handedness? Does the Universe Have a Handedness? Michael J. Longo University of Michigan, Ann Arbor, MI 48109 I have studied the distribution of spiral galaxies in the Sloan Digital Sky Survey (SDSS) to investigate whether the universe has an overall handedness. A preference for spiral galaxies in one sector of the sky to be left-handed or right-handed spirals would indicate a preferred axis in the Universe. The SDSS data show a strong signal for such an asymmetry. Its axis seems to be strongly corre- lated with that of the dipole, quadrupole and octopole moments in the WMAP microwave sky survey, whose unlikely alignment has been dubbed "the Axis of Evil". Our Galaxy has its spin axis along the same direction. I propose a mechanism that explains all of these align- ments in terms of a large-scale cosmic magnetic field. GLCW8 - 1 (a) A hypothetical universe with all galaxies having the same handedness. Note that galaxies in one hemisphere would appear to us to be right-handed and in the opposite hemisphere left-handed. (b) A “typical” spiral galaxy from the SDSS. This one is defined as having right-handed “spin”. (c) A left-handed two-armed spiral galaxy. GLCW8 - 2 The Sloan Digital Sky Survey The SDSS DR5 database contains ~40000 galaxies with spectra for redshifts <0.04 with a wide coverage in right ascensions (RA) and a more limited range of declina- tions ( ). A few percent of these are spiral galaxies that can be used in a search for a preferred handedness. GLCW8 - 3 A few "typical" Galaxies from the Sloan Survey GLCW8 - 4 The SDSS sky coverage is, of course, far from complete. (A) Polar plot of right ascensions vs. redshifts for all declinations. The gaps in coverage are due to obscuration by the Milky Way. (B) Plot of declinations vs. redshifts. The left and right hemispheres in (A) are plotted on their respective sides in (B). The declination coverage mainly reflects the location of the telescope in the Northern hemisphere Declinations between -19° and +60° were used in this analysis. GLCW8 - 5 The Analysis (1) First select galaxies from the SDSS with the SQL command: select p.objid, p.ra, p.dec, p.u, p.g, p.r, p.i, p.z, s.z as redshift from galaxy p, specobj s where p.objid=s.bestobjid and p.g < 17 and s.z BETWEEN 0.001 AND .04 which translates as "Select galaxies (with spectra) with green magnitude greater than -17 and with redshifts between 0.001 and 0.04." This yielded 22,768 galaxies. GLCW8 - 6 The Analysis (2) These were then scanned "by hand" and galaxies with fairly clear spiral structure were selected. No Yes No No Galaxies that were seen too "edge-on" for spiral structure to be apparent were not used. No GLCW8 - 7 The Analysis (2-cont'd) This scanning was done randomly in right ascension and declination, so that any bias would not give a false signal. Selected spirals were scaled appropriately and down- loaded from the SDSS web site as JPEG files for further analysis. Each JPEG had separate red, green, and blue images. After some months of effort, this yielded approx. 2835 spirals. GLCW8 - 8 The spiral candidates were then analyzed by an IDL program to determine their handedness. The red, green, and blue components of the JPEG files were analyzed separately The JPEG file for each spiral galaxy was submitted to an IDL program to determine its handed- ness. The algorithm used for this analysis was based on a rotating one-armed spiral mask. The spiral mask was rotated in 64 steps through the galaxy, and the convolu- tion of the mask and galaxy was determined at each step. The 64 convolutions were then subjected to a Fourier analysis to determine the power in each har- monic term of order n. Two masks were used; one was the mirror image of the other (thus representing right- and left-handed spirals that were otherwise identical). For more, see http://www-personal.umich.edu/~mlongo/Handedness/ GLCW8 - 9 "Typical" Fourier Power vs. Order Red is positive handedness mask Blue is negative GLCW8 - 10 The asymmetry a(n) is defined as the difference between the (+/–) powers for each order divided by their sum. An average overall asymmetry A was obtained from a weighted sum of orders 2 through 6. The red, green and blue images were analyzed separately. The differences between their A’s were used as a measure of the uncertainty !A, and the three were averaged to get an average A for each galaxy. For further analysis it was required that |A| > 0.15 and that |A| > 2(!A). GLCW8 - 11 RA=90° 0.0022 0.23 (33) (3) Net asymmetries <A> by 0.145 0.0648 sector in RA and segments -0.021 0.0266 -0.0046 in z. Segments with positive (284) (65) 0.0381 0.0959 <A> are indicated in red 0.152 0.249 and negative <A> in blue. 0.0179 0.0401 0.0164 0.0238 The <A> for segments 0.0986 0.0308 0.0046 -0.068 0.113 with <10 galaxies are not (366) 0.259 0.175 (58) 0.195 shown. The larger numbers RA=0° RA=180° 0.0406 0.0159 near the periphery give the 0.0657 0.0258 0.0986 0.0138 0.0862 0.0504 overall asymmetry for that 0.0653 0.0009 sector; the black num- -0.050 0.0101 (65) (297) 0.198 bers in parentheses are 0.0690 the total number of spiral 0.152 z = 0.02 0.0178 galaxies in the sector. 0.0982 0.082 0.0064 (31) (258) 0.0121 0.0780 -0.051 (190) z = 0.04 GLCW8 - 12 Number counts and net asymmetries for the RA ranges indicated. The 3rd row gives the combined numbers for the first two rows. The last column gives the number of standard deviations for the asymmetries. + – + – RA Range N N NTot (N – N )/NTot ± A / (R) 80° to –80° 118 104 222 0.063±0.067 +0.94 (L) 150° to 210° 296 368 664 –0.108±0.039 –2.79 (R-L) Combined 178 264 886 –0.0971±0.0336 –2.89 The σ are determined from standard normal distribution statistics, ! ( N ) = N , which gives !( A ) = 1 / N + + N " The 3rd row shows the difference in number counts between the first two rows. The combined asymmetry differs from zero by 2.89 σ . The nominal probability for exceeding 2.89 σ is 0.39%. GLCW8 - 13 If I maximize the asymmetry by choosing the optimal axis, this becomes an asymmetry of 3.6 σ at an RA of 188°. The probability of this happening by chance is about 0.04%. The SDSS coverage in declination is too limited to say much about the declination other than that it is consistent with δ ~ 0°. GLCW8 - 14 The Wilkinson Microwave Anisotropy Probe (WMAP) studied the cosmic background radiation. Their results for the angular power spectra showed anomalies in the low- l moments. The axis of the dipole, the normal to the quadrupole, and two of the octopole axes nearly coincided with each other and with the ecliptic, the plane of the Earth's orbit. This bizarre alignment has been dubbed "the Axis of Evil". GLCW8 - 15 * "It has been suggested that a preferred direction in CMB fluctuations may signal a nontrivial cosmic topology. The preferred axis could also be the result of aniso- tropic expansion, possibly due to strings, walls, or magnetic fields, or even the result of an intrinsically inhomogeneous Universe. Such claims remain controversial; more mundanely the observed ‘‘axis of evil’’ could be the result of galactic foreground contamination or large-scale unsubtracted systematics. ." Original title "The Axis of Evil" * RA = 173°, δ = 4° GLCW8 - 16 The alignment with the ecliptic (plane of the Earth's orbit) and equinoxes was especially troubling because the only way to explain it is foreground contamination from the Solar System(!) The big problem in studying the CMB is the "foreground" contamination from the Galactic plane which has to be carefully removed. So we have astrotheorists wringing their hands over the unexpected alignments. GLCW8 - 17 A possible explanation of the quadrupole and octopole alignments was offered by Campanelli et al. – PRL 97, 131302 (2006) Ellipsoidal Universe Can Solve the Cosmic Microwave Background Quadrupole Problem L. Campanelli, P. Cea and L. Tedesco The recent 3 yr Wilkinson Microwave Anisotropy Probe data have confirmed the anomaly concerning the low quadrupole amplitude compared to the best-fit –cold dark matter prediction. We show that by allowing the large-scale spatial geometry of our universe to be plane symmetric with eccentricity at decoupling or order 10-2, the quadrupole amplitude can be drastically reduced without affecting higher multipoles of the angular power spectrum of the temperature anisotropy. GLCW8 - 18 Campanelli et al. suggest that the eccentricity is produced by a cosmic magnetic field ~5 x 10-9 G. The Campanelli et al. explanation assumes an "ellipsoidal" universe. However, I contend that a large-scale cosmic magnetic field alone is is sufficient to explain all of the observed alignments. A large scale magnetic field is the only reasonable explanation for an align- of spiral galaxy spins. As the ionized matter in the protogalaxy condenses, the electrons and protons will move in cyclotron orbits about the field lines in opposite senses. Energy loss by synchrotron radiation will help to damp the angular momentum. As we'll see in a moment, our Galaxy is a perfect example. GLCW8 - 19 The proposed mechanism – A large-scale magnetic field can generate a CMB quadrupole by inverse Compton scattering of electrons in the intergalactic plasma that are preferentially circulating with one handedness.
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