Supergalactic Plane Research Articles

Searching for large-scale structure in deep radio surveys

(Abridged Abstract) We calculate the expected amplitude of the dipole and higher spherical harmonics in the angular distribution of radio galaxies. The median redshift of radio sources in existing catalogues is z=1, which allows us to study large scale structure on scales between those accessible to present optical and infrared surveys, and that of the Cosmic Microwave Background (CMB). The dipole is due to 2 effects which turn out to be of comparable magnitude: (i) our motion with respect to the CMB, and (ii) large scale structure, parameterised here by a family of Cold Dark Matter power-spectra. We make specific predictions for the Green Bank (87GB) and Parkes-MIT-NRAO (PMN) catalogues. For these relatively sparse catalogues both the motion and large scale structure dipole effects are expected to be smaller than the Poisson shot-noise. However, we detect dipole and higher harmonics in the combined 87GB-PMN catalogue which are far larger than expected. We attribute this to a 2 % flux mismatch between the two catalogues. We also investigate the existence and extent of the Supergalactic Plane in the above catalogues. In a strip of +- 10 deg of the standard Supergalactic equator, we find a 3-sigma detection in PMN, but only 1-sigma in 87GB.

Limits on source distances for the most energetic cosmic rays in intergalactic magnetic fields

Abstract The propagation of the highest energy cosmic rays through the intergalactic magnetic field is considered, including the effect of interactions with the 2.7 K microwave background. Energy loss in the microwave background due to photo-pion production limits the total distance travelled by the cosmic rays and the turbulent intergalactic field determines their total displacement. At energies above 10 20 eV, the average displacements are a few tens of megaparsecs, limiting possible sources to the volume dominated by the supergalactic plane.

The Signature of a Correlation between Cosmic‐Ray Sources above 1019eV and Large‐Scale Structure

We analyze the anisotropy signature expected if the high-energy (>1019 eV) cosmic-ray (CR) sources are extragalactic and trace the distribution of luminous matter on large scales. We investigate the dependence of the anisotropy on both the relative bias between the CR sources and the galaxy distribution and on the (unknown) intrinsic CR source density. We find that the expected anisotropy associated with the large-scale structure (LSS) should be detected once the number of CR events observed above 1019 eV is increased by a factor of ~10. This would require ~30 observation-years with existing experiments, but less than 1 year with the proposed ~5000 km2 Auger detectors. We find that the recently reported concentration of the Haverah Park CR events toward the supergalactic plane is not consistent with the known LSS. If real, the Haverah Park result suggests that the CR sources are much more concentrated toward the supergalactic plane than the known LSS. Our results are not sensitive to the number density of CR sources. We show that once the number of detected events is increased by a factor of ~10, the number density would be strongly constrained by considering the probability of having repeating sources.

Wiener reconstruction of the IRAS 1.2-Jy galaxy redshift survey: cosmographical implications

We utilise the method of Wiener reconstruction with spherical harmonics and Bessel functions to recover the density and velocity fields from the IRAS 1.2Jy redshift survey. The results are robust to changes in prior parameters and the number of expansion coefficients. Maps of these fields are presented in a variety of projections. Many known structures are observed, including clear confirmations of the clusters N1600 and A3627. The Perseus-Pisces supercluster appears to extend out to roughly 9000km/s, and the reconstruction shows `backside infall' to the Centaurus/Great Attractor region. A qualitative comparison of the reconstructed IRAS gravity field with that from Tully-Fisher peculiar velocity measurements (Mark III) shows reasonable agreement. The Wiener reconstruction of the density field is also the optimal reconstruction (in the minimum variance sense) of any quantity which is linear in the density contrast. We show reconstructions of three such quantities. The misalignment angle between the IRAS and CMB Local Group dipoles is only 13 degrees out to 5000km/s, but increases to 25 degrees out to 20,000km/s. The reconstructed IRAS bulk flow out to 5000km/s is roughly 300km/s, which agrees in amplitude with that derived from the Mark III peculiar velocities (370km/s). However, the two bulk flow vectors deviate by 70 degrees. Finally, moment of inertia analysis shows that the Wiener reconstructed Supergalactic Plane is aligned within 30 degrees of that defined by de Vaucouleurs.

Limits on Source Distances for the Most Energetic Cosmic Rays

AbstractThe propagation of the highest energy cosmic rays through the 2·7 K microwave background is considered. Photo-pion production interactions cause energy losses for primary cosmic ray protons which result in significant energy degradation over intergalactic distances. The process of energy loss is discussed and an estimate is made of the average distances travelled for observed cosmic rays with a range of energies, assuming a power law source spectrum. At energies over 1020 eV, the average distances travelled are a few tens of megaparsecs, limiting possible sources to the volume dominated by the supergalactic plane.

An Obscured Galaxy Redshift Survey with FLAIR

A problem for studies of large scale structures in nearby space (cz < 10,000 km s-1) is the presence of the Zone of Avoidance which is so large and wide on the sky that potentially important clusters and voids remain undetected. A prime example was the Ophiuchus cluster discovered by Wakamatsu and Malkan (1981) as a heavily obscured cD cluster close to the Galactic centre region (l = 0·5°, b = +9·5°). It is the second brightest X-ray cluster after Perseus. A hidden galaxy survey was performed by visually searching ESO/SERC Sky Survey (R and J) copy films of the region centred at l = 355°, b = +10° finding more than 4000 galaxies in six fields. Several irregular clusters adjacent to Ophiuchus were found forming a supercluster which may be connected to the Hercules supercluster by a wall structure parallel to the local supergalactic plane (Wakamatsu et al. 1994). In front of this supercluster, an 'Ophiuchus Void' is suggested (cz = 4,500 km s-1). The Ophiuchus supercluster at cz = 8,500 km s-1 is similar to the Hercules supercluster (cz = 11,000 km s-1), and extends north toward the latter supercluster.

The sky distribution of radiosources with flat spectra

Abstract Extragalactic radio sources with flat spectra (α 10°) supergalactic latitudes in the range of 150÷400 mJy. The shift of the correlation interval for the sources which are away from the supergalactic plane to fainter flux densities as well as the shift of the distribution of correlation pairs to less angular sizes for these sources probably reflect the sky distribution of radio sources for more distant rich clusters.

Redshift Distribution of Galaxies in the Southern Milky way Region 210° < I < 360° and |b| < 15°

We have carried out a redshift survey of an IRAS flux-limited (f60 > 0.6) galaxy sample behind the southern Milky Way, 210° < l < 360° at |b| < 15°. The survey includes redshifts for 951 galaxies, ~500 -of which are new. Of these 951 galaxies, 462 are in the zone 5° < b < 15 ° and 353 are in the zone −15° < b < −5°. Though the innermost region of the Milky Way (|b| = 5°) remains opaque except in the longitude near 240°, the deected galaxies show a high degree of completeness (~70%) in the zones 5° < b < −5° and −15° < b < −5°. The cone diagrams exhibiting the detailed distribution of IRAS galaxies in the region 210° < l < 360°, |b| < 15° shows two clusters in the Puppis region (l = 240°, b = −7°, v = 2400 km−1; l = 245° b = −5°, v = 7500 km s−1), the A3627 cluster (l = 325°, b =−7°; v = 4500 km s−1), the S4 cluster (l= =280°, b = 7°; v = 5500 km s−1), and a possible void at l = 245°, v = 3000 km s−1. The region 270° < l < 350° is dominated by overdensity of galaxies representing the extension of the Hydra-Centaurus Complex in the positive latitudes and the Pavo-Indus complex in the negative latitudes A velocity histogram of galaxies in the GA region 290° < l < 350°, |b| < 15° reveals a substantial overdensity of galaxies in the velocity range 2400–5000 km s−1. The centroid of this overdensity is located at 4000 km s−1. The broad increased density of galaxies seen in our data corresponds with the distant concentration seen at 4500 km s−1 in the supergalactic plane survey that covers the same longitude range like ours in l, but a larger range in latitude b (-30° to -10° and +10° to +45°). This lends support to the idea that the overdensity extends all the way from the Centaurus-Hydra complex (l = 302°, b = +22°) in the north to the major concentration of the Pavo-Indus Supercluster (l = 332°, b = −24°) in the south, through the Miky Way. We conclude that peak of the overdensity responsible for the peculiar velocity field in the local region is possibly situated in the Milky Way itself.

Possible Clustering of the Most Energetic Cosmic Rays within a Limited Space Angle Observed by the Akeno Giant Air Shower Array.

Accumulated data of the Akeno Giant Air Shower Array (AGASA) indicate that arrival directions of a significant fraction of extremely high energy cosmic rays (EHECR) are uniformly distributed over the observable sky. However, three pairs of showers with angular separation of less than 2.5\ifmmode^\circ\else\textdegree\fi{} within the pair are observed among the 36 events above 40 EeV ( $4\ifmmode\times\else\texttimes\fi{}{10}^{19}\mathrm{eV}$), corresponding to a chance probability of 2.9% from uniform distribution. It should be noted that two pairs of them are observed to be within 2.0\ifmmode^\circ\else\textdegree\fi{} of the supergalactic plane.

Arrival directions of the southern highest energy cosmic rays

We have examined the arrival directions of the highest energy cosmic rays recorded by the southern hemisphere SUGAR air shower array to determine whether there exists in the south a preference for directions along the supergalactic plane as suggested by northern data. We have not found such an effect.

Visual search for galaxies near the northern crossing of the Supergalactic Plane by the Milky Way

We have visually examined twelve Palomar red Plates for galaxies at low Galactic latitude b, where the Supergalactic Plane (SGP) is crossed by the Galactic Plane (GP), at Galactic longitude l ~135 degrees. The catalogue consists of 2575 galaxy candidates, of which 462 have major axis diameters d >= 0.8 arc min (uncorrected for extinction). Galaxy candidates can be identified down to |b| ~ 0 degrees. One of our galaxy candidates (J24 = Dwingeloo 1) has recently been discovered independently in 21cm by Kraan-Korteweg et al. (1994) as a nearby galaxy. Comparisons with the structures seen in the IRAS and UGC catalogues are made. We compare the success rate of identifying galaxies using the IRAS Point Source Catalogue under different colour selection criteria. The criteria that require both the 60 micron and 100 micron fluxes to be of high quality, have the highest probability of selecting a galaxy (with d >= 0.6 arc min), but at the expense of selecting a smaller number of galaxies in total.

Arrival directions of the most energetic cosmic rays.

In this Letter we examine the arrival directions of the most energetic cosmic rays $(Eg2\ifmmode\times\else\texttimes\fi{}{10}^{19}\mathrm{eV})$ detected by several air shower experiments. We find that data taken by different air shower arrays show positive correlations, indicating a nonuniform arrival direction distribution. We also find that the events with energy $g4\ifmmode\times\else\texttimes\fi{}{10}^{19}\mathrm{eV}$ exhibit a correlation with the general direction of the supergalactic plane, where a large number of potential sources are located. If confirmed by data from other experiments our results would support models for the extragalactic origin of the highest energy cosmic rays.

The orientation of spin vectors of galaxies in the Ursa Major filament

view Abstract Citations (20) References (22) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The Orientation of Spin Vectors of Galaxies in the Ursa Major Filament Han, Cheongho ; Gould, Andrew ; Sackett, Penny D. Abstract Spin vectors of 60 galaxies in the "Ursa Major filament" are obtained from CCD images and spectroscopic determinations of the directions of rotation. These data are used to remove the fourfold degeneracy introduced by the projected images of galaxies, making possible the complete reconstruction of the galaxy spin vectors. Several possible organizations of spin vectors are investigated by means of statistical analyses of the three-dimensional spin vector maps. The results indicate that there exists no significant alignment of galaxy spin vectors with respect to the supergalactic plane, the supergalactic axis, or the cylindrical axis of the filament itself. No tendency for linear alignment of spin vectors toward any specific direction was detected. We also obtain a statistically negative result for azimuthal, radial, and circular-helical orientation of spin vectors. Publication: The Astrophysical Journal Pub Date: May 1995 DOI: 10.1086/175671 arXiv: arXiv:astro-ph/9408022 Bibcode: 1995ApJ...445...46H Keywords: Alignment; Attitude (Inclination); Galactic Rotation; Galaxies; Sky Surveys (Astronomy); Spin Dynamics; Charge Coupled Devices; Data Correlation; Radial Velocity; Red Shift; Spectrum Analysis; Statistical Analysis; Astronomy; GALAXIES: FUNDAMENTAL PARAMETERS; GALAXIES: KINEMATICS AND DYNAMICS; Astrophysics E-Print: 20 pages, 4 figures, request PostScript file to cheongho@payne.mps.ohio-state.edu, OSU-TA-14/94 full text sources arXiv | ADS | data products SIMBAD (99) NED (94)

Possible Connection between Large-scale Structures

AbstractFrom the Lyon-Meudon Extragalactic Database (LEDA) we constructed a sample of 27000 galaxies with radial velocities smaller than 15 000 kms−1. From this first sample we selected the 5683 largest galaxies, which constitute a sample complete up to the diameter limit D25 = 1·6′. This sub-sample has been used to search for the most populated plane. The result is that the plane defined by the pole (l = 52°; b= 16°) contains twice as many galaxies as would be found for randomly distributed galaxies. This plane is not far from the supergalactic plane. The distribution of galaxies in this plane has been studied by using the radial velocity as an estimate of the distance. An excess of galaxies appears at a distance of about 70 Mpc. We discuss the reality of this density enhancement which could result from selection effects.

Wiener Reconstruction of All-Sky Galaxy Surveys in Spherical Harmonics

The analysis of whole-sky galaxy surveys commonly suffers from the problems of shot-noise and incomplete sky coverage (e.g., at the Zone of Avoidance). The orthogonal set of spherical harmonics is utilized here to expand the observed galaxy distribution. We show that in the framework of Bayesian statistics and Gaussian random fields the 4π harmonics can be recovered and the shot-noise can be removed, giving the optimal picture of the underlying density field. The correction factor from observed to reconstructed harmonics turns out to be the well-known Wiener filter (the ratio of signal to signal + noise), which is also derived by requiring minimum variance. We apply the method to the projected 1.2 Jy IRAS survey. The reconstruction confirms the connectivity of the supergalactic plane across the Galactic plane (at Galactic longitude l~135^deg^ and l~315^deg^) and the Puppis cluster behind the Galactic plane (l~240^deg^). The method can be extended to three dimensions in both real and redshift space, and applied to other cosmic phenomena such as the COBE microwave background maps.

Optical galaxies within 8000 km s-1 -I. The density field

The density field of optical galaxies to a depth of 8000 km s–1 over 67 per cent of the sky is determined using the UGC and ESO catalogues. The reconstruction method compensates for the varying completeness of the redshift data and for the galaxies that are not selected in the catalogues. The optical density field is dominated by supercluster complexes with dimensions in excess of 6000 km s–1. The most prominent of these are Perseus–Pisces and Centaurus–Hydra–Virgo–Pavo. The same complexes are seen in maps of IRAS galaxies, but the contrast of the optical maps is higher by a factor of 1.35 ± 0.16 when measured in 2500 km s–1 cells. By comparing the overdensity of galaxies in the Virgo supercluster to Virgo infall and assuming that mass follows light, we obtain |$\Omega =0.20_{-0.15}^{+0.30}$| . The ‘Great Attractor Region’ covered by Dressler's Supergalactic Plane Survey is overdense to 6000 km s–1, well beyond the Cen 30 cluster. However, unless there is a massive supercluster hidden in the zone of avoidance, this region is not sufficiently overdense for it to be identified with the Great Attractor inferred from |${D}_{n} - \sigma$| and Tully–Fisher peculiar velocities. Furthermore, within the Centaurus–Hydra–Virgo–Pavo complex, the density field peaks close to the Cen 30 cluster, which suggests that large-scale streaming motions may be better described by a weak 200 ± 150 km s–1 infall centred near Cen 30, plus a bulk dipole motion of 400 ± 150 km s–1 in the CMB frame.

The Shapes of Galaxy Groups

view Abstract Citations (12) References (32) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The Shapes of Galaxy Groups Fasano, G. ; Pisani, A. ; Vio, R. ; Girardi, M. Abstract The shape of groups of galaxies has been since now a disregarded topic in the literature, mainly due to the fact that individual ellipticity estimates of poor systems are strongly biased toward higher values. Such a bias turns out to depend on both the ellipticity itself and on the richness of the group. In this paper we have devised a modified version of the classical Lucy's iterative method, which is able to perform a statistical rectification of the observed ellipticity distribution of groups. Since this method needs an estimate of the average radial profile of the groups, we have faced also this problem. Our analysis has been applied to a sample of 54 groups belonging to the Tully (1987) catalog. The sample is selected in order to reduce the well-known, distance-dependent observational biases, which are present in all available group catalogs (Pisani et al. 1992). We found statistical evidence that galaxy groups share a common law for the radial distribution of members. This law can be quite satisfactorily represented by a simple Gaussian model, whereas a de Vaucouleurs profile (for instance) is definitely not consistent with the data. It is important to stress that the rectified distribution of apparent ellipticities looks very different from the original (unrectified) one. This implies that any statistical analysis which does not take into account the above mentioned bias, has to give meaningless results. The final aim of the paper is to produce the distribution of intrinsic ellipticities of groups, by deprojection of their apparent (rectified) ellipticity distribution. To do this we have to assume a biaxial (oblate or prolate) intrinsic shape of the groups are some model for their spatial orientation. Because of this reason, before the deprojection, we have searched for possible alignments of the group major axes along the supergalactic plane or toward the Local Supercluster center. We found a weak indication in favor of the latter hypothesis, but more sizable samples are needed to give statistical significance to this conclusion. At this stage, we have been forced to perform the deprojection by assuming a random orientation of the groups in the space. The apparent (rectified) ellipticity distribution which is obtained from our sample of galaxy groups, turned out to be consistent with both the oblate and the prolate intrinsic shapes. However, the oblate hypothesis should imply that a great fraction of groups has a very flattened, disklike structure. This circumstance is rather difficult to be explained within the available cosmological scenarios. Moreover, the convergence of the deprojection algorithm in the oblate case is hard-earned, and the final agreement with the data is less satisfactory than that obtained in the prolate case. All these facts led us to prefer the prolate solution with respect to the oblate one. Obviously a mixture of two different populations (oblate and prolate), as well as a triaxial solution, cannot be excluded. Publication: The Astrophysical Journal Pub Date: October 1993 DOI: 10.1086/173256 Bibcode: 1993ApJ...416..546F Keywords: GALAXIES: CLUSTERING full text sources ADS | data products SIMBAD (1)

The Puppis cluster of galaxies behind the Galactic plane and the origin of the 'Local Anomaly'

Recent surveys of galaxies behind the Galactic plane have revealed the Puppis cluster, centred at l approximately 240-degrees, b approximately 0-degrees and redshift cz approximately 1000-2000 km s-1. We supplement the recent 2-Jy IRAS redshift survey of Strauss et al. for absolute value of b > 5-degrees with an IRAS-selected sample in the direction of Puppis (absolute value of b < 5-degrees; 230-degrees < l < 260-degrees), which consists of 32 identified galaxies, 12 of them with measured redshift. Using this combined sample, we examine the overdensity of Puppis and its dynamical effect on the motion of the Local Group. We find that the projected number count of galaxies brighter than 2 Jy in Puppis is about half that of Virgo. We also compare Puppis with the rest of the sky by a spherical harmonic reconstruction; out to a distance of 3000 km s-1 Puppis is second only to Virgo. We estimate that Puppis (which lies below the Supergalactic plane) may contribute at least 30 km s-1 to the motion of the Local Group perpendicular to the Supergalactic plane (V(SGZ) = -370 km s-1 in the cosmic microwave background frame). Together with the Local Void (above the Supergalactic plane) and Fornax and Eridanus (below it), this may explain the origin of the so-called 'Local Anomaly'. The analysis presented here illustrates how to combine non-uniform surveys behind the Galactic plane to produce whole-sky uniform surveys.

A redshift survey of IRAS galaxies. IV - The galaxy distribution and the inferred density field

We have completed a full-sky flux-limited redshift survey of galaxies detected by the Infrared Astronomical Satellite (IRAS), which we use to characterize the density distribution of galaxies to a redshift of 8000 km s −1 . The galaxy distribution is dominated by the Hydra-Centaurus−Pavo-Indus supercluster (the Great Attractor) and the Perseus-Pisces supercluster. The Local Supercluster is an extension of the former. There is a large void in front of the Perseus-Pisces supercluster, as well as off the supergalactic plane

Does Gravity Rule the Universe?

AbstractThe initial results of a southern sky survey of the peculiar velocities of 1355 spiral galaxies by a group at Mount Stromlo and Siding Spring Observatories (MSSSO) are discussed against the background of past work in this area. The most important result is that the Great Attractor does not exist; rather, there is bulk flow relative to the cosmic microwave background (CMB) of amplitude 600 km s−1 and scale greater than 130 h−1 Mpc in the Supergalactic plane. This is generated by the assumption that the CMB dipole is Doppler induced by our Galaxy moving at 622 km s−1 relative to the CMB. This may be incorrect, in which case there is no bulk flow and the radiation dipole is cosmological in origin with important implications for the early Universe.