Largest 3D Map of Galaxies

Blob · #1 (**permalink**) 03-October-2006, 11:32 AM

Quote:

A team of American, Australian and British astronomers has released maps from the largest full-sky, three-dimensional survey of galaxies ever conducted.
Their detailed maps show the ‘local’ cosmos out to a distance of 600 million light years, identifying all the major superclusters of galaxies and voids. They also provide important clues regarding the distribution of the mysterious ‘dark matter’ and ‘dark energy’ which are thought to account for up to 96% of the apparent mass of the Universe.
Within this vast volume, the most massive galaxy supercluster is 400 million light years away. It was named after its identifier, the American astronomer Harlow Shapley. The Shapley supercluster is so big that it takes light at least 20 million years to travel from its one end to the other. However, Shapley is not the only massive supercluster in our vicinity.
The new maps are based on the observation that, as the Universe expands, the colours of galaxies change as their emitted light waves are stretched or “redshifted”. By measuring the extent of this redshift, astronomers are able to calculate approximate distances to galaxies.
The new survey, known as the 2MASS Redshift Survey (2MRS), has combined two dimensional positions and colours from the Two Micron All Sky Survey (2MASS), with redshifts of 25,000 galaxies over most of the sky. These redshifts were either measured specifically for the 2MRS or they were obtained from an even deeper survey of the southern sky, the 6dF Galaxy Redshift Survey (6dFGS).

Read more

IMAGE 1
IMAGE 2
IMAGE 3

Title: Reconstructed Density and Velocity Fields from the 2MASS Redshift Survey
Authors: Pirin Erdo¢gdu, Ofer Lahav, John P. Huchra., Matthew Colless, Roc M. Cutri, Emilio Falco. Teddy George, Thomas Jarrett, D. Heath Jones, Lucas M. Macri, Jeff Mader, Nathalie Martimbeau, Michael A. Pahre, Quentin A. Parker, Anais Rassat, Will Saunders

We present the reconstructed real-space density and the predicted velocity fields from the Two Mass Redshift Survey (2MRS). The 2MRS is the densest all-sky redshift survey to date and includes about 23,200 galaxies with extinction corrected magnitudes brighter than Ks = 11.25. Our method is based on the expansion of these fields in Fourier-Bessel functions.
Within this framework, the linear redshift distortions only affect the density field in the radial direction and can easily be deconvolved using a distortion matrix. Moreover, in this coordinate system, the velocity field is related to the density field by a simple linear transformation. The shot noise errors in the reconstructions are suppressed by means of a Wiener filter which yields a minimum variance estimate of the density and velocity fields.
Using the reconstructed real-space density fields, we identify all major superclusters and voids. At 50 h-1 Mpc, our reconstructed velocity field indicates a back-side infall to the Great Attractor region of vinfall = (491 ± 200)(β/0.5) kms-1 in the Local Group frame and vinfall = (64 ± 205)(β/0.5) kms^-1 in the cosmic microwave background (CMB) frame and β is the redshift distortion parameter. The direction of the reconstructed dipole agrees well with the dipole derived by Erdo¢gdu et al. (2006). The misalignment between the reconstructed 2MRS and the CMB dipoles drops to 13. at around 5000 kms^-1 but then increases at larger distances.

Read more (676kb, PDF)

thorka · #2 (**permalink**) 03-October-2006, 03:28 PM

In this survey it looks up to 600 mil. light years, SLOAN Digital Survey looks even further as far as I know. Considerng those vast distances, what we see from Earth is becoming "obsolete" picture : distant objects have different positions then we see them from Earth.
I would compare it to tracking group of planes just based on their sounds: one can exactly track position of all sounds, but trying to do draw their 3D positions exactly means to take into consideration speed ot the sound , espec. for further planes.

My point is : do we in those studies intend to develop model (3D map) of the Space as instant picture (all objects in their positions to the same point of time, which would include prediction of position of moving distant objects) OR the model will present Space as we see it from Earth as of today ?

Tomas

antoniseb · #3 (**permalink**) 03-October-2006, 03:35 PM

Quote:

Originally Posted by thorka

OR the model will present Space as we see it from Earth as of today?

I can imagine that some people will want to project what the 'instantaneous' universe looks like now, but most studies are of the universe as we see it today. Your use of the word 'we' is a little confusing to me.

publiusr · #4 (**permalink**) 06-October-2006, 07:39 PM

I love this kind of art.

Thread Tools	Search this Thread
Show Printable Version Email this Page	Search this Thread: Advanced Search
Display Modes
Linear Mode Switch to Hybrid Mode Switch to Threaded Mode