What is AzTEC2?

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What is AzTEC2, a bright object in millimeter waves but invisible at optical wavelengths, with no known distance since its discovery 15 years ago? In this astronomy article to be published in ApJ we tell you about it arXiv:2001.06997 , and you can find an explanation to all public below.

AzTEC2 is the second brightest 1.1mm source found with the AzTEC camera in 2005 in the COSMOS field. Then AzTEC was mounted in the 15m JCMT telescope, and had an image sharpness of 18 arc seconds (1 arcsec ~ 1 coin of 1 dime at 4km). Now AzTEC is at the  LMT.

The ALMA telescope array, with 18 times better sharpness, found that AzTEC2 is not a single galaxy, but two very close and bright galaxies that form stars at  about a 2000 and 700 larger rate than the Milky Way. They are very dusty, hence their great brightness at 1.1mm.

Now with ALMA we have detected the ionized carbon line, and we determine its distance: galaxy A, with the largest star formation, is 25,206 million light years away, and galaxy B is at 25,219 million light years. Both galaxies are separated by about 65 thousand light years from each other.

AzTEC2A and AzTEC2B galaxies will surely merge into one, like the nearby Antenna galaxies. The gravitational interaction is strong and the partial cause of the great star formation that both galaxies experience.

The Carbon line allows to derive the distribution and movement of gas in galaxy A. This gives us a mass for galaxy A of ~ 300 billion masses of the Sun within a radius of about 8 thousand light years. We do not know how much of this mass are stars because we do not see their visible light

The article is led by two Mexican scientists who work in the US: Eric Jiménez Andrade (NRAO) and Jorge Zavala (UT Austin), both INAOE alumni. 15 other researchers from Mexico, USA, Germany and Croatia also participate.

Translation of my unrolled Twitter thread from 28/1/2020.