NRAO | ALMA | 2015 Apr 07
Astronomers have discovered that a distant galaxy -- seen from Earth with the aid of a gravitational lens -- appears like a cosmic ring, thanks to the highest resolution images ever taken with the Atacama Large Millimeter/submillimeter Array (ALMA).[imghover=https://public.nrao.edu/images/non-gall ... s_nrao.jpg]https://public.nrao.edu/images/non-gall ... T_nrao.jpg[/imghover]ALMA image of the gravitationally lensed galaxy SDP.81. The bright orange central region
of the ring (ALMA's highest resolution observation ever) reveals the glowing dust in this
distant galaxy. The surrounding lower-resolution portions of the ring trace the millimeter
wavelength light emitted by carbon monoxide. In the ALMA/Hubble composite image,
the diffuse blue element at the center of the ring is from the intervening lensing galaxy,
as seen with the Hubble Space Telescope. (Credit: ALMA (NRAO/ESO/NAOJ);
B. Saxton NRAO/AUI/NSF; NASA/ESA Hubble, T. Hunter (NRAO))[/i]
Forged by the chance alignment of two distant galaxies, this striking ring-like structure is a rare and peculiar manifestation of gravitational lensing as predicted by Albert Einstein in his theory of general relativity.
Gravitational lensing occurs when a massive galaxy or cluster of galaxies bends the light emitted from a more distant galaxy, forming a highly magnified, though much distorted image. In this particular case, the galaxy known as SDP.81 and an intervening galaxy line up so perfectly that the light from the more distant one forms a nearly complete circle as seen from Earth.
Discovered by the Herschel Space Observatory, SDP.81 is an active star-forming galaxy nearly 12 billion light-years away, seen at a time when the Universe was only 15 percent of its current age. It is being lensed by a massive foreground galaxy that is a comparatively nearby 4 billion light-years away. ...
The new SDP.81 images were taken in October 2014 as part of ALMA’s Long Baseline Campaign, an essential program to test and verify the telescope’s highest resolving power, achieved when the antennas are at their greatest separation: up to 15 kilometers apart.
The highest resolution image of SDP.81 was made by observing the relatively bright light emitted by cosmic dust in the distant galaxy. This striking image reveals well-defined arcs in a pattern that hints at a more complete, nearly contiguous ring structure. Other slightly lower-resolution images, made by observing the faint molecular signatures of carbon monoxide and water, help complete the picture and provide important details about this distant galaxy.
Though this intriguing interplay of gravity and light in SDP.81 has been studied previously by other observatories, including radio observations with the Submillimeter Array and the Plateau de Bure Interferometer, and visible light observations with the Hubble Space Telescope, none has captured the remarkable details of the ring structure revealed by ALMA. ...
ALMA Long Baseline Observations of the Strongly Lensed Submillimeter Galaxy
HATLAS J090311.6+003906 at z=3.042 - ALMA Partnership et al
- arXiv.org > astro-ph > arXiv:1503.02652 > 09 Mar 2015 (v1), 03 Apr 2015 (v3)