Hidden Dwarf Dark Galaxy Spotted In ALMA Gravitational Lens Image

Posted: Apr 16 2016, 6:19am CDT | by , Updated: Apr 16 2016, 11:11pm CDT, in News | Latest Science News


Hidden Dwarf Dark Galaxy Spotted in ALMA Image
Composite image of the gravitational lens SDP.81 showing the distorted image of the more distant galaxy (red arcs) and the nearby lensing galaxy (blue center object) Credit: Y. Hezaveh; ALMA

New analysis reveals a dwarf dark galaxy which has been distorted by the gravity of a foreground galaxy.

Astronomers have found a dwarf dark galaxy hidden in Atacama Large Millimeter/Submillimeter Array (ALMA) telescope’s image.

In 2014, a variety of experimental images were taken by ALMA telescope in order to get an idea of its power and capacity. One of those images was an Einstein Ring, where a red light from a distant galaxy is seen encircling another galaxy nearly 12 billion light years away.

When researchers recently reanalyzed this distorted image, they found an evidence of dwarf dark galaxy lurking in the ring (white dot in the left lower arc) nearly 4 billion light years away.  

ALMA is a powerful tool to gaze at galaxies lurking in the universe which are otherwise too distant to observe. In this image, dwarf galaxy is obscured by distortion and this distortion is caused by gravitational influence of dark matter.

Lead researcher Yashar Hezaveh from Stanford University in California explains this phenomenon in this way. “We can find these invisible objects in the same way that you can see rain droplets on a window. You know they are there because they distort the image of the background objects.”

Universe is mostly made up of dark matter which cannot be directly observed directly. However, its presence can be felt only by gravitational influence. 

Using powerful computer models, researchers have identified gravitational anomaly in the region of the space. Based on its relation to larger galaxy, estimated mass and lack of an optical counterpart, researchers suspect that the subtle anomaly was potentially be caused by an extremely fain, dark matter galaxy. 

Scientists theorize that most galaxies are accompanied by dwarf galaxies and other objects even our own galaxy Milky Way is thought to have thousands of such small objects. However, it is exceedingly hard to detect those dwarf dark objects or galaxies.

“This discrepancy between observed satellites and predicted abundances has been a major problem in cosmology for nearly two decades, even called a 'crisis' by some researchers,” said Neal Dalal, one of the researchers involved in the study. “If these dwarf objects are dominated by dark matter, this could explain the discrepancy while offering new insights into the true nature of dark matter.”

Currently dark matter is taken as cold substance but with the help of those dark matter ‘clumps’ around distant galaxies, we can measure the temperature of dark matter. And this discovery could pave the way to address important questions related to the nature of dark matter.

“We are now confident that ALMA can efficiently discover these dwarf galaxies,” said Hezaveh. “Our next step is to look for more of them and to have a census of their abundance to figure out if there is any possibility of a warm temperature of dark matter particles.”

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Hira Bashir covers daily affairs around the world.




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