Search

An HI mass function (HIMF) was derived for 751 galaxies selected from the deep Parkes HI survey across the Zone of Avoidance (HIZOA). HIZOA contains both the Great Attractor Wall and the Local Void, two of the most extreme environments in the local Universe, making the sample eminently suitable to explore the overall HIMF as well as its dependence on local environment. To avoid any selection bias because of the different distances of these large-scale structures, we first used the two-dimensional stepwise maximum-likelihood method for the definition of an average HIMF. The resulting parameters of a Schechter-type HIMF for the whole sample are $\alpha = -1.33\pm0.05$, $\log(M_{\rm HI}^*/M_{\odot})=9.93\pm0.04$, and $\phi^* = (3.9\pm0.6)\times 10^{-3}$ Mpc$^{-3}$. We then used the $k$-th nearest-neighbour method to subdivide the sample into four environments of decreasing local density and derived the Schechter parameters for each subsample. A strong trend is observed, for the slope $\alpha$ of the low-mass end of the HIMF. The slope changes from being nearly flat, i.e. $\alpha = -0.99\pm0.19$ for galaxies residing in the densest bin, to the steep value of $\alpha = -1.31\pm0.10$ in the lowest density bin. The characteristic mass, however, does not show a clear trend between the highest and lowest density bins. We find similar trends in the low-mass slope when we compare the results for a region dominated by the Great Attractor, and the Local Void, which are found to be over-, respectively underdense by 1.35 and 0.59 compared to the whole sample., Comment: 10 pages, 13 figures, 4 tables, accepted for publication in MNRAS

We report distance measurements for the Norma cluster based on the near-infrared $J$- and $K_s$-band Fundamental Plane (FP) relations. Our simultaneous $J$ and $K_s$-band photometry analyses were performed using 31 early-type galaxies in the nearby Norma cluster obtained using the 1.4 m InfraRed Survey Facility (IRSF) at the South African Astronomical Observatory. Our final $K_s$-band FP sample consists of 41 early-type galaxies from the Norma cluster observed using the IRSF and the New Technology Telescope (NTT) at the European Southern Observatory. This is the largest cluster sample used for peculiar velocity studies in the Great Attractor region to date. From the $K_s$-band FP, we find a distance to the Norma cluster of $4915 \pm 121$ km s$^{-1}$. The implied peculiar velocity for Norma is $44 \pm 151$ km s$^{-1}$ which further supports a small peculiar velocity for the Norma cluster., 15 pages, 6 Figures. Accepted for publication in ApJ

The Norma cluster is a very rich, massive nearby galaxy cluster lying at or close to the ‘core’ of the Great Attractor (GA). A carefully determined redshift-independent distance and peculiar velocity of this cluster, therefore, helps us clarify if the GA partakes in large-scale motions. We have thus determined the distance and peculiar velocity of the Norma cluster using the K s -band isophotal Tully-Fisher relation. Using near-infrared K s -band isophotal magnitudes and Hi line widths for 12 late-type galaxies, six of which lie within the Norma cluster, the measured distance of the Norma cluster is 4893 ± 329 km s−1 ( d = 69.4 ± 4.7 Mpc). The corresponding peculiar velocity is +61± 329 km s−1, which although with large uncertainty, is consistent with zero.

A blind HI survey of the extragalactic sky behind the southern Milky Way has been conducted with the multibeam receiver on the 64-m Parkes radio telescope. The survey covers the Galactic longitude range 212 < l < 36 and Galactic latitudes |b| < 5, and yields 883 galaxies to a recessional velocity of 12,000 km/s. The survey covers the sky within the HIPASS area to greater sensitivity, finding lower HI-mass galaxies at all distances, and probing more completely the large-scale structures at and beyond the distance of the Great Attractor. Fifty-one percent of the HI detections have an optical/NIR counterpart in the literature. A further 27% have new counterparts found in existing, or newly obtained, optical/NIR images. The counterpart rate drops in regions of high foreground stellar crowding and extinction, and for low-HI mass objects. Only 8% of all counterparts have a previous optical redshift measurement. A notable new galaxy is HIZOA J1353-58, a possible companion to the Circinus galaxy. Merging this catalog with the similarly-conducted northern extension (Donley et al. 2005), large-scale structures are delineated, including those within the Puppis and Great Attractor regions, and the Local Void. Several newly-identified structures are revealed here for the first time. Three new galaxy concentrations (NW1, NW2 and NW3) are key in confirming the diagonal crossing of the Great Attractor Wall between the Norma cluster and the CIZA J1324.7-5736 cluster. Further contributors to the general mass overdensity in that area are two new clusters (CW1 and CW2) in the nearer Centaurus Wall, one of which forms part of the striking 180 deg (100/h Mpc) long filament that dominates the southern sky at velocities of ~3000 km/s, and the suggestion of a further Wall at the Great Attractor distance at slightly higher longitudes., Published in Astronomical Journal 9 February 2016 (accepted 26 September 2015); 42 pages, 7 tables, 18 figures, main figures data tables only available in the on-line version of journal

In this work we describe 59 galaxies discovered in the talk-forum of the Milky Way Project (MWP) by volunteers of the project. The MWP is based on infrared images by the Spitzer Space Telescope and primarily probes the Zone of Avoidance for star-forming regions located in the Milky Way. The list of galaxies found here include 35 galaxies previously not described, a possible galaxy cluster and two galaxies that could be located in the Great Attractor Wall. The volunteers mainly discovered larger (d > 12'') galaxies with a higher star-forming rate and likely missed galaxies with low star-forming rate or small galaxies. This work demonstrates that many galaxies in the Zone of Avoidance remain undiscovered in the GLIMPSE data set.

We present the results of our study of the peculiar motions for 41 galaxy clusters and groups in the regions of the Hercules and Leo superclusters (0.027 < z < 0.045). For this purpose, based on SDSS (Data Release 8) data, we compiled a sample of early-type galaxies in the investigated clusters and groups, constructed their fundamental planes (FPs), and determined independent distances and peculiar velocities. The Hubble law between the radial velocities galaxy clusters and the distances derived from the FPs holds for the rich Hercules supercluster as a whole. At the same time, however, significant peculiar motions along the line of sight with rms deviations of 736 ± 50 and 584 ± 50 km s−1 are observed within this supercluster and in its immediate neighborhood. In the poor Leo supercluster, the rms deviation is also large, 625 ± 70 km s−1. Its Hubble diagram exhibits the approach of galaxy clusters and groups along the line of sight relative to the most massive cluster A1185. In the immediate neighborhood of the Leo supercluster (virtually in its field), the rms deviation of the peculiar velocities is minimal, 287 ± 60 km s−1.

Cosmography, the study and making of maps of the universe or cosmos, is a field where visual representation benefits from modern three-dimensional visualization techniques and media. At the extragalactic distance scales, visualization is contributing in understanding the complex structure of the local universe, in terms of spatial distribution and flows of galaxies and dark matter. In this paper, we report advances in the field of extragalactic cosmography obtained using the SDvision visualization software in the context of the Cosmicflows Project. Here, multiple visualization techniques are applied to a variety of data products: catalogs of galaxy positions and galaxy peculiar velocities, reconstructed velocity field, density field, gravitational potential field, velocity shear tensor viewed in terms of its eigenvalues and eigenvectors, envelope surfaces enclosing basins of attraction. These visualizations, implemented as high-resolution images, videos, and interactive viewers, have contributed to a number of studies: the cosmography of the local part of the universe, the nature of the Great Attractor, the discovery of the boundaries of our home supercluster of galaxies Laniakea, the mapping of the cosmic web, the study of attractors and repellers., Accepted for publication in the PASP Special Focus Issue: Techniques and Methods for Astrophysical Data Visualization

We investigated the properties of galaxy clusters in the region of the Hercules supercluster using observational data from the SDSS and 2MASS catalogs and the NED. We have selected 13 galaxy clusters with a total dynamical mass of 4.82 × 1015 M ⊙ in a 100 × 45 Mpc supercluster region in the plane of the sky (0.030 < z < 0.041). In addition, our sample includes eight clusters from the immediate neighborhoods of the superclusters and ten field clusters at the same z. The derived properties of the rich Hercules supercluster are shown in comparison with the data for the poor Leo supercluster. The main parameters of the virialized galaxy cluster regions in the near infrared (K s ) for the Hercules supercluster differ from those for the Leo supercluster: the number of galaxies and the total luminosity (to a limiting magnitude of −21 · 5) increase with cluster mass (L K,200 ∝ M 200 0.91±0.07 and N 200 ∝ M 200 0.94±0.07 ), but the dependences are steeper by 0.28 and 0.22. In the virialized cluster regions, the fraction of early-type galaxies selected by the bulge contribution, concentration index, and u t= r color is, on average, 66% (60% in Leo, 70% in the field) among the galaxies brighter than −23 · 3 and 54% (51% in Leo, 61% in the field) among the galaxies brighter than −22 · 3. The fraction of early-type galaxies in the superclusters does not change with galaxy cluster mass and luminosity. The composite luminosity function of the rich Hercules supercluster is described by a Schechter function and does not differ from the luminosity function of the poor Leo supercluster for the luminosity interval [−26 m , −21 · 5] but differs from the field luminosity function at the same z determined from ten galaxy clusters.

It is a firm prediction of the concordance Cold Dark Matter (CDM) cosmological model that galaxy clusters live at the intersection of large-scale structure filaments. The thread-like structure of this "cosmic web" has been traced by galaxy redshift surveys for decades. More recently the Warm-Hot Intergalactic Medium (WHIM) residing in low redshift filaments has been observed in emission and absorption. However, a reliable direct detection of the underlying Dark Matter skeleton, which should contain more than half of all matter, remained elusive, as earlier candidates for such detections were either falsified or suffered from low signal-to-noise ratios and unphysical misalignements of dark and luminous matter. Here we report the detection of a dark matter filament connecting the two main components of the Abell 222/223 supercluster system from its weak gravitational lensing signal, both in a non-parametric mass reconstruction and in parametric model fits. This filament is coincident with an overdensity of galaxies and diffuse, soft X-ray emission and contributes mass comparable to that of an additional galaxy cluster to the total mass of the supercluster. Combined with X-ray observations, we place an upper limit of 0.09 on the hot gas fraction, the mass of X-ray emitting gas divided by the total mass, in the filament., Comment: Nature, in press

The article discusses the discovery of the supercluster Laniakea in which the Milky Way galaxy is located. Topics covered include the potential role of Laniakea in providing insights into the past and future of the universe, the possibility that Laniakea would help demystify dark energy, and the expansion of the universe at an accelerating rate. The peculiar velocity of 600 kilometers per second by the Local Supercluster, and the role of the Great Attractor complex in it are also discussed.

IB is supported by a Science and Technology Facilities Council studentship. The positions and velocities of galaxies in the Local Group (LG) measure the gravitational field within it. This is mostly due to the Milky Way (MW) and Andromeda (M31). We constrain their masses using distance and radial velocity (RV) measurements of 32 LG galaxies. To do this, we follow the trajectories of many simulated particles starting on a pure Hubble flow at redshift 9. For each observed galaxy, we obtain a trajectory which today is at the same position. Its final velocity is the model prediction for the velocity of that galaxy. Unlike previous simulations based on spherical symmetry, ours are axisymmetric and include gravity from Centaurus A. We find the total LG mass is 4.33+0.37 -0.32 × 1012M⊙, with 0.14 ± 0.07 of this being in the MW. We approximately account for IC 342, M81, the Great Attractor and the Large Magellanic Cloud. No plausible set of initial conditions yields a good match to the RVs of our sample of LG galaxies. Observed RVs systematically exceed those predicted by the best-fitting Lambda Cold Dark Matter (ΛCDM) model, with a typical disagreement of 45.1+7.0 -5.7 km s-1 and a maximum of 110 ± 13 km s-1 for DDO 99. Interactions between LG dwarf galaxies cannot easily explain this. One possibility is a past close flyby of the MW and M31. This arises in some modified gravity theories but not in ΛCDM. Gravitational slingshot encounters of material in the LG with either of these massive fast-moving galaxies could plausibly explain why some non-satellite LG galaxies are moving away from us even faster than a pure Hubble flow. Publisher PDF

High-accuracy HI profiles and linewidths are presented for inclined ($(b/a)^o < 0.5$) spiral galaxies in the southern Zone of Avoidance (ZOA). These galaxies define a sample for use in the determinations of peculiar velocities using the near-infrared Tully-Fisher (TF) relation. The sample is based on the 394 HI-selected galaxies from the Parkes HI Zone of Avoidance survey (HIZOA). Follow-up narrow-band Parkes HI observations were obtained in 2010 and 2015 for 290 galaxies, while for the further 104 galaxies, sufficiently high signal-to-noise spectra were available from the original HIZOA data. All 394 spectra are reduced and parameterized in the same systematic way. Five different types of linewidth measurements were derived, and a Bayesian mixture model was used to derive conversion equations between these five widths. Of the selected and measure galaxies, 342 have adequate signal-to-noise (S/N $\geq$ 5) for use in TF distance estimation. The average value of the signal-to-noise ratio of the sample is 14.7. We present the HI parameters for these galaxies. The sample will allow a more accurate determination of the flow field in the southern ZOA which bisects dynamically important large-scale structures such as Puppis, the Great Attractor, and the Local Void., 11 pages, 7 figures, 4 tables, accepted for publication in MNRAS

If we live in the vicinity of the hypothesized Great Attractor, the age of the universe as inferred from the local expansion rate can be off by 3 per cent. We study the effect that living inside or near a massive overdensity has on cosmological parameters induced from observations of supernovae, the Hubble parameter and the cosmic microwave background. We compare the results to those for an observer in a perfectly homogeneous Λ cold dark matter universe. We find that for instance the inferred value for the global Hubble parameter changes by around three per cent if we happen to live inside a massive overdensity such as the hypothesized Great Attractor. Taking into account the effect of such structures on our perception of the universe makes cosmology perhaps less precise, but more accurate.

‘Cosmic Flows’ is a program to determine galaxy distances for 30000 galaxies with systematic errors below 2%, almost ten times the number currently known and a five-fold improvement in systematics. The resultant velocity field will provide input for constrained local universe simulations: CLUES (www.clues-project.org). The observed and the simulated universe are then comparatively studied. This synergy of observations and theory distinguishes the program, and should lead to fundamental discoveries regarding the sources of deviations from the expansion of the universe. Specifically, the program should give a definitive answer to one of the most outstanding unsolved problem in cosmology: the cause of the motion of 630 km s–1 of our Galaxy manifested in the microwave background dipole. This paper presents current results with particular emphasis on the “great attractor” reconstruction (© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

The Universe on scales $10-100~h^{-1}$ Mpc is dominated by a cosmic web of voids, filaments, sheets and knots of galaxy clusters. These structures participate differently in the global expansion of the Universe: from non-expanding clusters to the above average expansion rate of voids. In this paper we characterize Hubble expansion anisotropies in the COMPOSITE sample of 4534 galaxies and clusters. We concentrate on the dipole and quadrupole in the rest frame of the Local Group. These both have statistically significant amplitudes. These anisotropies, and their redshift dependence, cannot be explained solely by a boost of the Local Group in the Friedmann-Lema��tre-Robertson-Walker (FLRW) model which expands isotropically in the rest frame of the cosmic microwave background (CMB) radiation. We simulate the local expansion of the Universe with inhomogeneous Szekeres models, which match the standard FLRW model on $> 100~h^{-1}$ Mpc scales but exhibit nonkinematic relativistic differential expansion on small scales. We restrict models to be consistent with observed CMB temperature anisotropies, while simultaneously fitting the redshift variation of the Hubble expansion dipole. We include features to account for both the Local Void and the "Great Attractor". While this naturally accounts for the Hubble expansion and CMB dipoles, the simulated quadrupoles are smaller than observed. Further refinement to incorporate additional structures may improve this. This would enable a test of the hypothesis that some large angle CMB anomalies result from failing to treat the relativistic differential expansion of the background geometry, a natural feature of solutions to Einstein's equations not included in the current standard model of cosmology., 32 pages, 4 figures, v3 - clarifications made, version accepted by JCAP

We analyze the properties of galaxy clusters in the region of the Leo supercluster using observational data from the SDSS and 2MASS catalogs. We have selected 14 galaxy clusters with a total dynamical mass of 1.77 × 1015 M ⊙ in the supercluster region 130 by 60 Mpc in the plane of the sky (z ≃ 0.037). The composite luminosity function of the supercluster is described by a Schechter function with parameters that, within the error limits, correspond to field galaxies and does not differ from the luminosity function of the richer Ursa Major (UMa) supercluster for the same luminosity range (the bright end). The luminosity functions of early-type and late-type galaxies in Leo at the faint end are characterized by a sharp decrease (α = −0.60±0.08) and a steep increase (α = −1.44± 0.10) in the number of galaxies, respectively. In the virialized cluster regions, the fraction of early-type galaxies selected by the u-r color, bulge contribution, and concentration index among the galaxies brighter than M * + 1 is, on average, 62%. This fraction is smaller than that in the UMa supercluster at a 2–3σ level. The near-infrared luminosities of galaxy clusters down to a fixed absolute magnitude correlate with their masses almost in the same way as for other samples of galaxy clusters (L 200,K ∝ M 200 0.63±0.11 )).

Galaxies congregate in clusters and along filaments, and are missing from large regions referred to as voids. These structures are seen in maps derived from spectroscopic surveys that reveal networks of structure that are interconnected with no clear boundaries. Extended regions with a high concentration of galaxies are called 'superclusters', although this term is not precise. There is, however, another way to analyse the structure. If the distance to each galaxy from Earth is directly measured, then the peculiar velocity can be derived from the subtraction of the mean cosmic expansion, the product of distance times the Hubble constant, from observed velocity. The peculiar velocity is the line-of-sight departure from the cosmic expansion and arises from gravitational perturbations; a map of peculiar velocities can be translated into a map of the distribution of matter. Here we report a map of structure made using a catalogue of peculiar velocities. We find locations where peculiar velocity flows diverge, as water does at watershed divides, and we trace the surface of divergent points that surrounds us. Within the volume enclosed by this surface, the motions of galaxies are inward after removal of the mean cosmic expansion and long range flows. We define a supercluster to be the volume within such a surface, and so we are defining the extent of our home supercluster, which we call Laniakea. A key component of this paper is an accompanying movie that can be viewed (also in 3D) and downloaded at http://irfu.cea.fr/laniakea or http://vimeo.com/pomarede/laniakea, accompanying video available in 3D, 7 minutes, english/french, closed captions, teaser of 1 minute http://irfu.cea.fr/laniakea

As part of our programme to map the large-scale distribution of galaxies behind the southern Milky Way, we observed 314 optically-selected, partially-obscured galaxies in the Zone of Avoidance (ZOA) in the Crux and Great Attractor (GA) regions. The observations were conducted with the Parkes 64m radio telescope, in a single-pixel pointed mode, reaching an rms noise level of typically 2-6 mJy over the velocity search range of 400

A detailed dynamical analysis of the nearby rich Norma cluster (ACO 3627) is presented. From radial velocities of 296 cluster members, we find a mean velocity of 4871 +/- 54 km/s and a velocity dispersion of 925 km/s. The mean velocity of the E/S0 population (4979 +/- 85 km/s) is offset with respect to that of the S/Irr population (4812 +/- 70 km/s) by `Delta' v = 164 km/s in the cluster rest frame. This offset increases towards the core of the cluster. The E/S0 population is free of any detectable substructure and appears relaxed. Its shape is clearly elongated with a position angle that is aligned along the dominant large-scale structures in this region, the so-called Norma wall. The central cD galaxy has a very large peculiar velocity of 561 km/s which is most probably related to an ongoing merger at the core of the cluster. The spiral/irregular galaxies reveal a large amount of substructure; two dynamically distinct subgroups within the overall spiral-population have been identified, located along the Norma wall elongation. The dynamical mass of the Norma cluster within its Abell radius is 1 - 1.1 x 10^15 h^-1_73 M_Sun. One of the cluster members, the spiral galaxy WKK 6176 which recently was observed to have a 70 kpc X-ray tail, reveals numerous striking low-brightness filaments pointing away from the cluster centre suggesting strong interaction with the intracluster medium., Sumbitted to MNRAS. 13 pages, 11 figures. Figures 6 and 10 reduced in resolution. Original available on request

We present the latest results of the Clusters in the Zone of Avoidance (CIZA) survey, which is mapping the large-scale matter distribution behind the Milky Way by performing the first systematic search for X-ray luminous galaxy clusters at low Galactic latitudes. The survey's approach, which uses X-ray emission to locate cluster candidates, overcomes the problems faced by optically selected cluster surveys which have traditionally avoided this region of the sky due to the severe extinction present along the Galactic plane. We here present the second flux-limited CIZA cluster catalog containing 60 X-ray luminous galaxy clusters, 88% of which are new discoveries. We also examine the degree to which known superclusters extend into the Zone of Avoidance and highlight newly discovered structures which have previously gone unnoticed. We show that the survey has found far fewer rich clusters in the Great Attractor region than would be expected given the region's proposed mass. Instead, we find a significant increase in the number of clusters behind the Great Attractor, with the most notable being an association of clusters near the Shapley supercluster. We propose these clusters trace an extension of the large-scale filament network in which the Shapley concentration is embedded. We also highlight an association of clusters near the Galactic anticenter, which is the first supercluster found to be completely hidden by the Milky Way. Our finding of a less massive Great Attractor and the detection of significant structures behind the complex supports studies which suggest the motion of nearby galaxies, including that of the Local Group, is due, in part, to a large-scale bulk flow which is induced by overdensities beyond the Great Attractor region.

The highly obscured radio-bright galaxy PKS1343-601 (l=309.7, b=+1.8) has been suspected to mark the centre of a hitherto unknown cluster in the Great Attractor region. As such it presents an ideal region for a search of galaxies in the near-infrared (NIR) and an in-depth study of their colours as a function of extinction. A visual search of a ~30 square-degree area centered on this radio galaxy on images of the NIR DENIS survey (IJK) revealed 83 galaxies (including two AGNs) and 39 possible candidates. Of these, 49 are also listed in the 2MASS Extended Source Catalog 2MASX. Taking the IRAS/DIRBE extinction values (Schlegel et al. 1998) at face value, the absorption in the optical (A_B) ranges from ~2m to over 100m across the Galactic Plane. Comparing the detections with other systematic surveys, we conclude that this search is highly complete up to the detection limits of the DENIS survey and certainly surpasses any automatic galaxy finding algorithm applied to crowded areas. The NIR galaxy colours from the 7" aperture were used as a probe to measure total Galactic extinction. A comparison with the IRAS/DIRBE Galactic reddening maps suggests that the IRAS/DIRBE values result in a slight overestimate of the true extinction at such low Galactic latitudes; the inferred extinction from the galaxy colours corresponds to about 87% of the IRAS/DIRBE extinctions. Although this determination still shows some scatter, it proves the usefulness of NIR surveys for calibrating the IRAS/DIRBE maps in the extinction range of 2m < A_B < 12m., 28 pages, 15 figures, submitted to A&A

According to the standard cosmological scenario, superclusters are objects that have just passed the turn around point and are collapsing. The dynamics of very few superclusters have been analysed up to now. In this paper we study the supercluster SC0028-0005, at redshift 0.22, identify the most prominent groups and/or clusters that make up the supercluster, and investigate the dynamic state of this structure. For the membership identification, we have used photometric and spectroscopic data from SDSS-DR10, finding 6 main structures in a flat spatial distribution. We have also used a deep multi-band observation with MegaCam/CFHT to estimate de mass distribution through the weak-lensing effect. For the dynamical analysis, we have determined the relative distances along the line of sight within the supercluster using the Fundamental Plane of early-type galaxies. Finally, we have computed the peculiar velocities of each of the main structures. The 3D distribution suggests that SC0028-005 is indeed a collapsing supercluster, supporting the formation scenario of these structures. Using the spherical collapse model, we estimate that the mass within $r = 10$~Mpc should lie between 4 and $16 \times 10^{15} M_\odot$. The farthest detected members of the supercluster suggest that within $\sim 60$~Mpc the density contrast is $\delta \sim 3$ with respect to the critical density at $z=0.22$, implying a total mass of $\sim 4.6$--$16 \times 10^{17} M_\odot$, most of which in the form of low-mass galaxy groups or smaller substructures., Comment: 12 pages, 9 figures, Accepted for publication in MNRAS

In this paper, the results of an analysis of galaxy positions and magnitudes in European Southern Observatory (ESO) field 606 are presented. This 5° × 5° field centred at 23.8 h,−19°.53, contains 29 313 galaxies with magnitudes m F between 12.97 and 20.64. An automatic search of galaxy clusters and groups in the field was made using the Voronoi tessellation technique for two cases: firstly, for all galaxies in the field and, secondly, for galaxies within a magnitude limit of 18.3. We found 37 clusters of galaxies in the field for the first case, and nine clusters for the second case. There are seven Abell–Corwin–Olowin (ACO) clusters in this ESO field. The location of the identified structures on the celestial sphere suggests the existence of a possible galaxy supercluster in the field that covers a region measuring 4°.8 by 2°.4 centred at 23.841 h and−20°.44. The largest clusters from both cases and five of the seven ACO clusters are in the region. The estimated size of the supercluster is 28 h − 1 × 14 ...

We present the result of a deep near-infrared survey of the newly identified X-ray luminous cluster of galaxies CIZA J1324.7-5736 in the Great Attractor (GA) region. In a 35 x 35 arcmin 2 region, 111 galaxy candidates with r Ks 20 > arcsec are identified. Comparison of the extinction-corrected K s -band luminosity function of CIZA J 1324.7-5736 with those of nearby clusters indicates that the richness class of CIZA J1324.7-5736 is almost the same as, or richer than, the Pavo. Centaurus and Hydra clusters but poorer than the Coma, Perseus and Norma clusters. CIZA J1324.7-5736 is possibly the second richest cluster in the GA region following the Norma cluster. The position of CIZA J1324.7-5736 [in the (l, b, v) space] is close to the Centaurus-Crux cluster and the agglomeration of galaxies detected by the Parkes Hi survey. CIZA J1324.7-5736, together with the Centaurus-Crux cluster and the Hi galaxy agglomeration, is most likely to be one of the richest local concentrations in the GA overdensity of galaxies.

The data on the peculiar velocities of 1493 RFGC flat spiral galaxies processed using the POTENT method allowed the density distribution of matter, including dark matter, on 75-Mpc scales to be reconstructed. Well-known attractors (the Great Attractor, the Perseus—Pisces and Coma superclusters) and voids are separated from the distribution. In general, the density distribution is close to that of IRAS galaxies, suggesting that the luminous-to-dark matter density ratio is constant. The masses of the main attractors were estimated.

We present cosmological simulations which closely mimic the real Universe within 100Mpc of the Local Group. The simulations, called Constrained Simulations, reproduce the large-scale density field with major nearby structures, including the Local Group, the Coma and Virgo clusters, the Great Attractor, the Perseus-Pices, and the Local Supercluster, in approximately correct locations. The MARK III survey of peculiar velocities of the observed structures inside 80Mpc/h sphere is used to constrain the initial conditions. Fourier modes on scales larger then 5Mpc/h are dominated by the constraints, while small scale waves are random. The main aim of this paper is the structure of the Local Supercluster (LSC; 30Mpc/h around the Virgo cluster) and the Local Group environment. We find that at the current epoch most of the mass (7.5e14Msun/h) of the LSC is located in a filament roughly centered on the Virgo cluster and extending over 40Mpc/h. The simulated Local Group (LG) is located in an adjacent smaller filament, which is not a part of the main body of the LSC, and has a peculiar velocity of 250kms toward the Virgo cluster. The peculiar velocity field in the LSC region is complicated and is drastically different from the field assumed in the Virgocentric infall models. The peculiar velocity flow in the vicinity of the LG in the simulation is ``cold'': the peculiar line-of-sight velocity dispersion within 7Mpc/h of the LG is less than 60km/s, comparable to the observed velocity dispersion of nearby galaxies., Comment: 22 pages, 9 figures, submitted to ApJ, high resolution version is available at http://astro.nmsu.edu/~aklypin/HOFFMAN

We report the results of applying the 2MASS Tully-Fisher (TF) relations to study the galaxy bulk flows. For 1141 all-sky distributed flat RFGC galaxies we construct J, H, K_s TF relations and find that Kron $J_{fe}$ magnitudes show the smallest dispersion on the TF diagram. For the sample of 971 RFGC galaxies with V_{3K} < 18000 km/s we find a dispersion $\sigma_{TF}=0.42^m$ and an amplitude of bulk flow V= 199 +/-61 km/s, directed towards l=301 degr +/-18 degr, b=-2 degr +/-15 degr. Our determination of low-amplitude coherent flow is in good agreement with a set of recent data derived from EFAR, PSCz, SCI/SCII samples. The resultant two- dimensional smoothed peculiar velocity field traces well the large-scale density variations in the galaxy distributions. The regions of large positive peculiar velocities lie in the direction of the Great Attractor and Shapley concentration. A significant negative peculiar velocity is seen in the direction of Bootes and in the direction of the Local void. A small positive peculiar velocity (100 -- 150 km/s) is seen towards the Pisces-Perseus supercluster, as well as the Hercules - Coma - Corona Borealis supercluster regions., Comment: 10 pages, 5 figures. A&A/2003/3582 accepted 15.05.2003

The apparatus of a correlation gamma function is used to analyze the spatial clustering of galaxies in the Local Supercluster. In particular, we analyzed a sample corrected for the peculiar velocities of the Local Supercluster galaxies by using our original technique for separating groups of galaxies. It turned out that the peculiar velocities did not significantly distort the gamma function even for relatively small sample sizes. The distribution of the galaxies obeys a power-law decrease in density with an index of 0.6–0.7. We found evidence for a luminosity dependence of the degree of galaxy clustering within the volume under study.

We report on the design and status of the Clusters in the Zone of Avoidance (CIZA) project, the first systematic X-ray search for clusters of galaxies behind the Milky Way. We demonstrate that an X-ray survey can find galaxy clusters at low Galactic latitude where optical searches are inefficient because of massive obscuration and extinction problems. We discuss the rationale for such a survey in the context of large-scale structure studies and describe in detail the combined X-ray/optical/NIR approach used by CIZA to identify clusters of galaxies at |b| < 20?, a region of the sky that has traditionally been excluded from earlier cluster catalogs. So far, CIZA has identified and spectroscopically confirmed 137 galaxy clusters in what used to be the zone of avoidance; additional clusters have been confirmed in imaging observations and await spectroscopic observation. We present a catalog of the 73 X-ray-brightest CIZA clusters, 53 (73%) of which are new discoveries. This sample is statistically complete out to at least z ~ 0.075 (cz ~ 22,500 km s-1). We reassess local large-scale structure in the Great Attractor (GA) region in light of this first X-ray-selected cluster sample at low Galactic latitude. Our survey discovered CIZA J1324.7-5736, a luminous cluster at l = 3074, b = 50, cz = 5700 km s-1, and possibly as massive as A3627, but ruled out a hypothesized X-ray-luminous cluster around the radio galaxy PKS 1343-601. We argue that this region of the GA may be best described as a wall-like, triangular structure with CIZA J1324.7-5736, A3627, and the Centaurus Cluster (A3526) at its vertices. Our survey also discovered what could be a supercluster in the same region but at cz ~ 15,000 km s-1, i.e., behind the GA. We speculate that the latter system may be partly responsible for the large-scale flow observed in this direction out to about that distance.

While Norma (ACO3627) is the richest cluster in the Great Attractor (GA) region, its role in the local dynamics is poorly understood. The Norma cluster has a mean redshift (z_CMB) of 0.0165 and has been proposed as the "core" of the GA. We have used the Ks-band Fundamental Plane (FP) to measure Norma cluster's distance with respect to the Coma cluster. We report FP photometry parameters (effective radii and surface brightnesses), derived from ESO NTT SOFI images, and velocity dispersions, from AAT 2dF spectroscopy, for 31 early-type galaxies in the cluster. For the Coma cluster we use 2MASS images and SDSS velocity dispersion measurements for 121 early-type galaxies to generate the calibrating FP dataset. For the combined Norma-Coma sample we measure FP coefficients of a=1.465+/-0.059 and b=0.326+/-0.020. We find an rms scatter, in log(central velocity dispersion) of 0.08 dex which corresponds to a distance uncertainty of 28% per galaxy. The zero point offset between Norma's and Coma's FPs is 0.154+/-0.014 dex. Assuming that the Coma cluster is at rest with respect to the cosmic microwave background frame and z_CMB(Coma)=0.0240, we derive a distance to the Norma cluster of 5026+/-160 km/s, and the derived peculiar velocity is -72+/-170 km/s, i.e., consistent with zero. This is lower than previously reported positive peculiar velocities for clusters/groups/galaxies in the GA region and hence the Norma cluster may indeed represent the GA's "core"., Comment: 16 pages, 11 figures, Accepted for publication in MNRAS

In this second paper of the catalogue series of galaxies behind the southern Milky Way, we report on the deep optical galaxy search in the Crux region (289 ' 318 and 10 b 10) and the Great Attractor region (316 ' 338 and 10 b 10). The galaxy catalogues are presented, a brief description of the galaxy search given, as well as a discussion on the distribution and characteristics of the uncovered galaxies. A total of 8182 galaxies with major diameters D 0: 2 were identied in this850 square degree area: 3759 galaxies in the Crux region and 4423 galaxies in the Great Attractor region. Of the 8182 galaxies, 229 (2.8%) were catalogued before in the optical (3 in radio) and 251 galaxies have a reliable (159), or likely (92) cross-identication in the IRAS Point Source Catalogue (3.1%). A number of prominent overdensities and laments of galaxies are identied. They are not correlated with the Galactic foreground extinction and hence indicative of extragalactic large-scale structures. Redshifts obtained at the South African Astronomical Observatory (SAAO) for 518 of the newly catalogued galaxies in the Crux and Great Attractor regions (Fairall et al. 1998; Woudt et al. 1999) conrm distinct voids and clusters in the area here surveyed. With this optical galaxy search, we have reduced the width of the optical \Zone of Avoidance" for galaxies with extinction-corrected diameters larger than 1.3 arcmin from extinction levels AB 1: m 0t oA B 3: m 0: the remaining optical Zone of Avoidance is now limited byjbj 3 (see Fig. 16).

ABSTRA C T The spatial orientations of the galactic planes for galaxies in the Coma/A1367 supercluster have been determined. Owing to the ambiguity in the determination of the inclination angle, two possible orientations of the normal to the galaxy plane were found. Two angles, the polar angle d D and the azimuthal angle h , describe the orientation of normals. The distribution of both angles has been checked for isotropy. It is shown that the distribution is not isotropic. The same alignment is observed for samples containing elliptical and lenticular galaxies and for samples containing only spirals, as well as for samples containing galaxies located in different parts of the supercluster. In the case of spiral galaxies, the anisotropy shows that galaxy rotation axes strongly favour alignment with the main plane of the supercluster. The projection of the rotation axes on to the main plane of the supercluster has a preferential direction pointing towards the supercluster, but this effect is weak. A comparison with theory is also presented.

Kormendy’s relation (μe-logR e) is used to investigate the structure of the compact Ursa Major supercluster of galaxies (11h30m+55°, cz=18 000 km s−1); this relation allows the distances of early-type galaxies to be estimated. The relative distances of 13 clusters in the supercluster and their peculiar velocities are determined with a mean statistical accuracy of 6%. In general, the supercluster obeys the Hubble relation between radial velocity and distance. However, there is reason to suggest that the supercluster consists of two subsystems with mean radial velocities of 16 200 and 19 700 km s−1. For a velocity dispersion in the subsystems of ∼1100 km s−1, the fact that each of them is gravitationally bound is not ruled out.

We use data on the local 3-dimensional galaxy distribution for studying the statistics of the detection rates of gravitational waves (GW) coming from supernova explosions. We consider both tensor and scalar gravitational waves which are possible in a wide range of relativistic and quantum gravity theories. We show that statistics of GW events as a function of sidereal time can be used for distinction between scalar and tensor gravitational waves because of the anisotropy of spatial galaxy distribution. For calculation of the expected amplitudes of GW signals we use the values of the released GW energy, frequency and duration of GW pulse which are consistent with existing scenarios of SN core collapse. The amplitudes of the signals produced by Virgo and the Great Attractor clusters of galaxies is expressed as a function of the sidereal time for resonant bar detectors operating now (IGEC) and for forthcoming laser interferometric detectors (VIRGO).Then, we calculate the expected number of GW events as a function of sidereal time produced by all the galaxies within 100 Mpc. In the case of axisymmetric rotational core collapse which radiates a GW energy of $10^{-9}M_{\odot}c^2$, only the closest explosions can be detected. However, in the case of nonaxisymmetric supernova explosion, due to such phenomena as centrifugal hangup, bar and lump formation, the GW radiation could be as strong as that from a coalescing neutron-star binary. For radiated GW energy higher than $10^{-6}M_{\odot}c^2$ and sensitivity of detectors at the level $h \approx 10^{-23}$ it is possible to detect Virgo cluster and Great Attractor, and hence to use the statistics of GW events for testing gravity theories., Comment: 15 pages, 12 figures