* Astronomy

Members Login
Username 
 
Password 
    Remember Me  
Home -> Astronomy News -> Cosmology News -> The Great Attractor
Post Info TOPIC: The Great Attractor
Blobrana


L

Posts: 131433
Date:
RE: The Great Attractor
Permalink  
 

Hubble Focuses on "the Great Attractor"

720333main1_attractor673.JPG

A busy patch of space has been captured in this image from the NASA/ESA Hubble Space Telescope. Scattered with many nearby stars, the field also has numerous galaxies in the background.
Located on the border of Triangulum Australe (The Southern Triangle) and Norma (The Carpenter's Square), this field covers part of the Norma Cluster (Abell 3627) as well as a dense area of our own galaxy, the Milky Way.
The Norma Cluster is the closest massive galaxy cluster to the Milky Way, and lies about 220 million light-years away. The enormous mass concentrated here, and the consequent gravitational attraction, mean that this region of space is known to astronomers as the Great Attractor, and it dominates our region of the Universe.
Read more



__________________
Blobrana


L

Posts: 131433
Date:
Permalink  
 

Title: The Mass Distribution of the Great Attractor as Revealed by a Deep NIR Survey
Authors: R.C. Kraan-Korteweg (1), I.F. Riad (1), P.A. Woudt (1), T. Nagayama (2), K. Wakamatsu (3) ((1) Astronomy Department, ACGC, University of Cape Town, South Africa, (2) Department of Astrophysics, Nagoya University, Japan, (3) Faculty of Engineering, Gifu University, Japan)

This paper presents the analysis of a deep near-infrared J,H,Ks-imaging survey (37.5 sq deg) aimed at tracing the galaxy distribution of the Great Attractor (GA) in the Zone of Avoidance along the so-called Norma Wall. The resulting galaxy catalogue is complete to extinction-corrected magnitudes Ks° = 14.8 mag for extinctions less than A_K = 1.0 mag and star densities below log N(Ks<14.0) < 4.72. Of the 4360 catalogued galaxies, 99.2% lie in the hereby constrained 89.5% of the survey area. Although the analysed galaxy distribution reveals no new major galaxy clusters at the GA distance (albeit some more distant ones), the overall number counts and luminosity density indicate a clear and surprisingly smooth overdensity at the GA distance that extends over the whole surveyed region. A mass estimate of the Norma Wall overdensity derived from (a) galaxy number counts and (b) photometric redshift distribution gives a lower value compared to the original prediction by Lynden-Bell et al. 1988 (~14%), but is consistent with more recent independent assessments.

Read more (678kb, PDF)



__________________
Blobrana


L

Posts: 131433
Date:
Galaxy cluster Abell 3627
Permalink  
 

ESO 137-001: Two Tails to Tell

Two spectacular tails of X-ray emission have been seen trailing behind a galaxy using the Chandra X-ray Observatory. A composite mage of the galaxy cluster Abell 3627 shows X-rays from Chandra in blue, optical emission in yellow and emission from hydrogen light -- known to astronomers as "H-alpha" -- in red. The optical and H-alpha data were obtained with the Southern Astrophysical Research (SOAR) Telescope in Chile.
At the front of the tail is the galaxy ESO 137-001. The brighter of the two tails has been seen before and extends for about 260,000 light years. The detection of the second, fainter tail, however, was a surprise to the scientists.
Read more

__________________
Blobrana


L

Posts: 131433
Date:
Abell 3627
Permalink  
 

X-ray observations with the ROSAT satellite then revealed that Abell 3627, a previously known cluster of galaxies, was much more massive than originally suspected, containing many more galaxies. Optical astronomers had missed a great number of galaxies, because of the obscuration, but with hindsight (and with better observations), could spot many more galaxies. It is now thought that the Great Attractor is probably a supercluster, with Abell 3627 near its center.
Read more

__________________
Blobrana


L

Posts: 131433
Date:
Superclusters
Permalink  
 

Title: Toward understanding rich superclusters
Authors: M. Einasto, E. Saar, V.J. Martinez, J. Einasto, L. J. Liivam"agi, E. Tago, J.-L. Starck, V. Mueller, P. Hein"am"aki, P. Nurmi, S. Paredes, M. Gramann, G. Huetsi

We present a morphological study of the two richest superclusters from the 2dF Galaxy Redshift Survey (SCL126, the Sloan Great Wall, and SCL9, the Sculptor supercluster). We use Minkowski functionals, shapefinders, and galaxy group information to study the substructure of these superclusters as formed by different populations of galaxies. We compare the properties of grouped and isolated galaxies in the core region and in the outskirts of superclusters. The fourth Minkowski functional V_3 and the morphological signature K_1- K_2 show a crossover from low-density morphology (outskirts of supercluster) to high-density morphology (core of supercluster) at mass fraction m_f ~ 0.7. The galaxy content and the morphology of the galaxy populations in supercluster cores and outskirts is different. The core regions contain a larger fraction of early type, red galaxies, and richer groups than the outskirts of superclusters. In the core and outskirt regions the fine structure of the two prominent superclusters as delineated by galaxies from different populations also differs. Our results suggest that both local (group/cluster) and global (supercluster) environments are important in forming galaxy morphologies and colours (and determining the star formation activity). The differences between the superclusters indicate that these superclusters have different evolutional histories

Read more (504kb, PDF)

__________________
Blobrana


L

Posts: 131433
Date:
Shapley Supercluster
Permalink  
 

Title: The Density Contrast of the Shapley Supercluster
Authors: Joseph A. Muñoz (Harvard), Abraham Loeb (Harvard)
(Version v2)

We calculate the density contrast of the Shapley Supercluster (SSC) based on the enhanced abundance of X-ray clusters in it using the extended Press-Schechter formalism. We derive a total SSC mass of M_tot=(4.4 ±0.44)x10^{16} M_sun within a sphere of 50 Mpc centred at a distance of about 160 Mpc. The nonlinear fractional density contrast of the sphere is (1+delta)=1.76 ±0.17 relative to the mean matter density in the Universe, but the contrast increases in the interior of the SSC. Including the cosmological constant, the SSC region is found to be gravitationally unbound. The SSC contributes only a minor portion (9.0% ±2.1%) of the peculiar velocity of the local group.

Read more (118kb, PDF)

__________________
Blobrana


L

Posts: 131433
Date:
Universe
Permalink  
 

Simulation of our Universe showing in large scale



__________________
Blobrana


L

Posts: 131433
Date:
RE: The Great Attractor
Permalink  
 

The Universe Nearby


__________________
Blobrana


L

Posts: 131433
Date:
Local Supercluster
Permalink  
 

Title: The Structure of the Local Supercluster of Galaxies Revealed by the Three-Dimensional Voronoi's Tessellation Method
Authors: O. V. Melnyk, A. A. Elyiv, I. B. Vavilova

3D Voronoi's tessellation method was first applied to identify groups of galaxies in the structure of a supercluster. The sample under consideration consists of more than 7000 galaxies of the Local Supercluster (LS) with radial velocities up to 3100 km/s. Because of an essential non-homogeneity of the LS catalogue, it was proposed to overscale distances in such an ''artificial'' way that the concentration of galaxies was varying as with increase of the distance a power-behaved function with the same exponent beta as for the full homogeneous catalogue. Various parameters of clustering were taking into account: alpha (0.01, 0.1, 1%) as the part of galaxies, which have the relative volume of a Voronoi's cell smaller than the critical one for the random distribution; beta = 0, which fits to the random galaxy distribution; beta = 0.7, which is close to the pancake galaxy distribution. It is revealed that Voronoi's tessellation method depends weakly on beta-parameter, and the number of galaxies in rich structures is growing rather than in poor ones with increase of alpha-parameter. The comparison of the groups derived with the groups obtained by Karachentsev's dynamical method shows that the number of groups, which coincides by all the components, is 22%. As a whole, the dynamical method is more preferred for identifying sparsely populated galaxy groups, whereas 3D Voronoi's tessellation method is preferred for more populated ones.

galaxy
Expand (34kb, 736 x 521)
Projection of the LS sample galaxies onto the plane perpendicular to the galactic plane: (a) in the v space, (b) in the u space, (c) a random distribution of the same number of galaxies, (d) the distribution of LS galaxies with Mabs < 17.5m in the v space, (e) the distribution of LS galaxies with Mabs < 19m in the v space, (f) the distribution of LS galaxies with Mabs < 20.5m in the v space.

Read more (865kb, PDF)

__________________
Blobrana


L

Posts: 131433
Date:
Shapley concentration
Permalink  
 

A large galaxy could be lurking unseen in our own cosmic backyard, a pair of researchers says. Such a massive object could explain a mysterious gravitational pull on the Milky Way.
Astronomers know both the direction and speed of the Milky Way's motion based on measurements of the cosmic microwave background radiation that filled all space shortly after the big bang. The wavelength of this radiation appears slightly shorter in the direction of the Milky Way's motion because of the Doppler effect.
This motion is thought to be due to the gravitational pull from surrounding galaxies and clusters of galaxies. But when the influence of all known galaxies and galaxy clusters is added up, the Milky Way's actual motion is off by about 20°.
Now, new calculations suggest that the discrepancy may be due to a large galaxy hidden right on our cosmic doorstep, or a hidden cluster of galaxies somewhat farther away in the same direction. The calculations were made by Avi Loeb and Ramesh Narayan of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts, US.

Read more

__________________
1 2  >  Last»  | Page of 2  sorted by
 
Quick Reply

Please log in to post quick replies.
Home -> Astronomy News -> Cosmology News -> The Great Attractor


Create your own FREE Forum
Report Abuse 		Powered by ActiveBoard