Cosmic shear in sky field with galaxy cluster

The image shows an example of the mapping of the dark mass distribution in one of the 50 sky fields observed with the VLT and FORS1. To the left is the original image, a 36-min exposure in a near-infrared wavelength band. To the right is the reconstructed map of the mass (a "mass photo") in this direction, based on an analysis of the weak shear effect seen in the field; that is, on the measured elongations and directions of the axes of the galaxy images in this field. The brighter areas indicate the directions in which there is most mass along the line of sight. The circle in the left photo surrounds the images of a distant cluster (or group) of galaxies, seen in this direction. Note that there is a corresponding concentration of mass in the "mass photo"; this is obviously the mass of that cluster. The mass reconstruction map shows the (mostly) dark matter responsible for the cosmic shear found on the small scales, now measured with the VLT. Technical information about these photos is available below.

Technical information about the photo: The sky photo (left) is reproduced from a 36 min exposure, obtained on 15 June 1999 with VLT ANTU and the multi-mode FORS1 instrument. The optical filter was I (900 nm) and the seeing was 0.53 arcsec. The field measures approx. 6 x 6 arcmin 2. North is up and East is left.

Crédit:

ESO

À propos de l'image

Identification:eso0040a
Type:Observation
Date de publication:1 décembre 2000
Communiqués de presse en rapport:eso0040
Taille:3000 x 1479 px

À propos de l'objet

Nom:Dark Matter, Galaxy cluster
Type:Early Universe : Cosmology : Phenomenon : Dark Matter
Early Universe : Galaxy : Grouping : Cluster
Catégorie:Galaxy Clusters

Image Formats

Grand JPEG
1,2 Mio
JPEG taille écran
213,2 Kio

Fonds d'écran

1024x768
287,3 Kio
1280x1024
436,4 Kio
1600x1200
589,2 Kio
1920x1200
707,6 Kio
2048x1536
851,2 Kio

Couleurs & filtres

DomaineLongueur d'ondeTélescope
Infrarouge
I
900 nmVery Large Telescope
FORS1

Exposure time: 1160s