ALMA: Dwarf Dark Galaxy Hidden in Gravitational Lens Image

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ALMA: Dwarf Dark Galaxy Hidden in Gravitational Lens Image

Post by bystander » Thu Apr 14, 2016 4:40 pm

Dwarf Dark Galaxy Hidden in ALMA Gravitational Lens Image
National Radio Astronomy Observatory | ALMA | 2016 Apr 14
[img3="Composite image of the gravitational lens SDP.81 showing the distorted ALMA image of the more distant galaxy (red arcs) and the Hubble optical image of the nearby lensing galaxy (blue center object). By analyzing the distortions in the ring, astronomers have determined that a dark dwarf galaxy (data indicated by white dot near left lower arc segment) is lurking nearly 4 billion light-years away. (Credit: Y. Hezaveh, Stanford Univ.; ALMA (NRAO/ESO/NAOJ); NASA/ESA Hubble Space Telescope)"]https://public.nrao.edu/images/non-gall ... I_nrao.jpg[/img3][hr][/hr]
Subtle distortions hidden in ALMA’s stunning image of the gravitational lens SDP.81 are telltale signs that a dwarf dark galaxy is lurking in the halo of a much larger galaxy nearly 4 billion light-years away. This discovery paves the way for ALMA to find many more such objects and could help astronomers address important questions on the nature of dark matter.

In 2014, as part of ALMA’s Long Baseline Campaign, astronomers studied a variety of astronomical objects to test the telescope's new, high-resolution capabilities. One of these experimental images was that of an Einstein ring, which was produced by the gravity of a massive foreground galaxy bending the light emitted by another galaxy nearly 12 billion light-years away.

This phenomenon, called gravitational lensing, was predicted by Einstein’s theory of general relativity and it offers a powerful tool for studying galaxies that are otherwise too distant to observe. It also sheds light on the properties of the nearby lensing galaxy because of the way its gravity distorts and focuses light from more distant objects.

In a new paper accepted for publication in the Astrophysical Journal, astronomer Yashar Hezaveh at Stanford University in California and his team explain how detailed analysis of this widely publicized image uncovered signs of a hidden dwarf dark galaxy in the halo of the more nearby galaxy. ...

Researchers Help Discover "Dark Galaxy"
National Center for Supercomputing Applications | University of Illinois | 2016 Apr 14

Detection of Lensing Substructure Using ALMA Observations of the Dusty Galaxy SDP.81 - Yashar D. Hezaveh et al
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