Team discovers major supercluster of galaxies hidden by Milky Way November 16, 2016 Please Register or Log in to view the hidden image! The Vela supercluster in its wider surroundings: The image displays the smoothed redshift distribution of galaxies in and around the Vela supercluster (larger ellipse; VSC). The centre of the image, so-called the Zone of Avoidance, is covered by the Milky Way (with its stellar fields and dust layers shown in grey scale), which obscures all structures behind it. Colour indicates the distance ranges of all galaxies within 500 - 1000 million light years (yellow is close to the peak of the Vela supercluster, green is nearer and orange further away). The ellipse marks the approximate extent of the Vela Supercluster, crossing the Galactic Plane. The VSC structure was revealed thanks to the new low latitude spectroscopic redshifts. Given its prominence on either side of the plane of the Milky Way it would be highly unlikely for these cosmic large-scale structures not to be connected across the Galactic Plane. The structure may be similar in aggregate mass to the Shapley Concentration (SC, smaller ellipse), although much more extended. The so-called “Great Attractor” (GA), located much closer to the Milky Way, is an example of a large web structure that crosses the Galactic Plane, although much smaller in extent than VSC. The central, dust-shrouded part of the VSC remains unmapped in the current Vela survey. Also visible are the Milky Way’s two satellite galaxies, LMC and SMC, located south of the Galactic plane. Credit: Thomas Jarrett (UCT) An international team of astronomers has discovered a previously unknown major concentration of galaxies in the constellation Vela, which they have dubbed the Vela supercluster. The gravitational attraction from this large mass concentration in our cosmic neighbourhood may have an important effect on the motion of our Local Group of galaxies including the Milky Way. It may also help to explain the direction and amplitude of the Local Group's peculiar velocity with respect to the Cosmic Microwave Background. Superclusters are the largest and most massive known structures in the Universe. They consist of clusters of galaxies and walls that span up to 200 million light-years across the sky. The most famous supercluster is the Shapley Supercluster, some 650 million light-years away containing two dozens of massive X-ray clusters for which thousands of galaxy velocities have been measured. It is believed to be the largest of its kind in our cosmic neighbourhood. Read more at: http://phys.org/news/2016-11-team-major-supercluster-galaxies-hidden.html#jCp
http://mnrasl.oxfordjournals.org/content/early/2016/11/08/mnrasl.slw229 Discovery of a supercluster in the ZOA in Vela: Abstract We report the discovery of a potentially major supercluster that extends across the Galactic Plane in the constellation of Vela, at a mean recessional velocity of ∼18 000 km s−1. Recent multi-object spectroscopic observations of this Vela Supercluster (VSCL), using AAOmega+2dF and SALT, confirm an extended galaxy overdensity in the Zone of Avoidance (ZOA) located where residual bulk flows predict a considerable mass excess. We present a preliminary analysis of ∼4500 new spectroscopic galaxy redshifts obtained in the ZOA centred on the Vela region (l = 272.∘" role="presentation" style="margin: 0px; padding: 0px; border: 0px; outline-style: none; font-size: 14px; font-family: inherit; line-height: normal; vertical-align: baseline; display: inline; word-spacing: normal; word-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; position: relative;">∘..∘;5 ± 20°, b = 0° ± 10°). The presently sparsely-sampled dataset traces an overdensity that covers 25° in Galactic longitude on either side of the Plane, suggesting an extent of 25° × 20°, corresponding to ∼ 115 × 90 h70 Mpc at the supercluster redshift. In redshift space the overdensity appears to consist of two merging wall-like structures, interspersed with clusters and groups. Both the velocity histogram and the morphology of the multi-branching wall structure are consistent with a supercluster classification. Kso" role="presentation" style="margin: 0px; padding: 0px; border: 0px; outline-style: none; font-size: 14px; font-family: inherit; line-height: normal; vertical-align: baseline; display: inline; word-spacing: normal; word-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; position: relative;">KosKso galaxy counts show an enhancement of ∼1.2 over the survey area for galaxies brighter than MK∗" role="presentation" style="margin: 0px; padding: 0px; border: 0px; outline-style: none; font-size: 14px; font-family: inherit; line-height: normal; vertical-align: baseline; display: inline; word-spacing: normal; word-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; position: relative;">M∗KMK∗ at the VSCL distance, and a galaxy overdensity of δ = 0.50–0.77 within a photometric redshift shell around VSCL, when compared to various 2MASS samples. Taking account of selection effects, the VSCL is estimated to contribute vLG≳50" role="presentation" style="margin: 0px; padding: 0px; border: 0px; outline-style: none; font-size: 14px; font-family: inherit; line-height: normal; vertical-align: baseline; display: inline; word-spacing: normal; word-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; position: relative;">vLG≳50vLG≳50 km s−1to the motion of the Local Group.
Thanks Paddoboy. I think I read about this a little while back maybe at the other site but it goes to show there is always more to discover. However that is the first time I have heard zone of avoidance so maybe this is yet another discovery past the one I seem to recall. Alex
