Subaru: Ancient Eye in the Sky

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bystander
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Subaru: Ancient Eye in the Sky

Post by bystander » Tue Jul 26, 2016 2:47 pm

Ancient Eye in the Sky
Subaru Telescope | National Astronomical Observatory of Japan | 2016 July 25
[c][attachment=0]Eye-of-Horus.jpg[/attachment][/c][hr][/hr]
Light from a distant galaxy can be strongly bent by the gravitational influence of a foreground galaxy. That effect is called strong gravitational lensing. Normally a single galaxy is lensed at a time. The same foreground galaxy can – in theory – simultaneously lens multiple background galaxies. Although extremely rare, such a lens system offers a unique opportunity to probe the fundamental physics of galaxies and add to our understanding of cosmology. One such lens system has recently been discovered and the discovery was made not in an astronomer’s office, but in a classroom. It has been dubbed the Eye of Horus, and this ancient eye in the sky will help us understand the history of the universe. ...

A close inspection of the images revealed two distinct arcs/rings of light with different colors. This strongly suggested that two distinct background galaxies were being lensed by the foreground galaxy. The lensing galaxy has a spectroscopic redshift of z = 0.79 (which means it’s 7.0 billion light-years away) based on data from the Sloan Digital Sky Survey. Follow-up spectroscopic observations of the lensed objects using the infrared-sensitive FIRE spectrometer on the Magellan Telescope confirmed that there are actually two galaxies behind the lens. One lies at z = 1.30 and the other is at z = 1.99 (9.0 and 10.5 billion light-years away, respectively). ...

The distinct features for the system (several bright knots, an arc, a complete Einstein ring) arise from the nice alignment of the central lens galaxy and both sources, creating an eye-like structure. The astronomers dubbed it Eye of Horus, for the sacred eye of an ancient Egyptian god, since the system has an uncanny resemblance to it. ...

A Spectroscopically Confirmed Double Source Plane Lens System
in the Hyper Suprime-Cam Subaru Strategic Program - Masayuki Tanaka et al
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Eye of Horus in pseudo color. Enlarged image to the right (field of view of <br />23 arcseconds x 19 arcseconds) show two arcs/rings with different colors. <br />The inner arc has a reddish hue, while the outer arc has a blue tint. These <br />arcs are lensed images of the two background galaxies. There are blobs <br />in and around the arcs/rings, which are also the lensed images of those <br />background galaxies. The yellow-ish object at the center is a massive <br />galaxy at z = 0.79 (distance 7 billion light years), which bends the light <br />from the two background galaxies. (Credit: NAOJ)
Eye of Horus in pseudo color. Enlarged image to the right (field of view of
23 arcseconds x 19 arcseconds) show two arcs/rings with different colors.
The inner arc has a reddish hue, while the outer arc has a blue tint. These
arcs are lensed images of the two background galaxies. There are blobs
in and around the arcs/rings, which are also the lensed images of those
background galaxies. The yellow-ish object at the center is a massive
galaxy at z = 0.79 (distance 7 billion light years), which bends the light
from the two background galaxies. (Credit: NAOJ)
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Ann
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Re: Subaru: Ancient Eye in the Sky

Post by Ann » Wed Jul 27, 2016 5:36 am

This 800 KB figure of the Eye of Horus system shows how the lensing works, and demonstrates that the blue background galaxy is more distant than the red one.

The red background galaxy must be dominated by yellow stars, which have been redshifted by cosmological redshift to look redder than the yellow stars in the elliptical foreground galaxy. The blue background galaxy must be dominated by ultraviolet stars and star formation.

Ann
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