EI2GYB > ASTRO 21.11.25 16:00l 54 Lines 4521 Bytes #200 (0) @ WW
BID : 47796_EI2GYB
Subj: Dusty star-forming galaxy at high redshift discovered
Path: ED1ZAC<ED1ZAC<GB7CIP<GB7YEW<W0ARP<N5MDT<EI2GYB
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Dusty star-forming galaxy at high redshift discovered
An international team of astronomers reports the discovery of a new dusty star-forming galaxy at high redshift. The newfound galaxy, designated AC-2168, was detected using the Atacama Large Millimeter/submillimeter Array (ALMA) and the Northern Extended Millimeter Array (NOEMA). The finding was detailed in a paper published Nov. 11 on the pre-print server arXiv.
Intense star formation hidden behind dust
The so-called dusty star-forming galaxies (DSFGs) are highly obscured galaxies undergoing a period of intense star formation, with star-formation rates reaching even 1,000 solar masses per year. They represent the most intense starbursts in the universe and are crucial to improving our understanding of galaxy formation and evolution.
However, although many DSFGs are known, their nuclear structure, which can be essential to better understand the evolution of these galaxies, is still not fully explored. Hence, finding new DSFGs and investigating them in detail could shed more light on this matter.
A surprising find
Recently, a group of astronomers led by Longji Bing of the University of Sussex, UK, inspected a part of the sky from the Cosmic Evolution Survey (COSMOS). By analyzing the COSMOS field with ALMA, they serendipitously identified a new DSFG at a redshift of approximately 6.63. The detection was confirmed by NOEMA observations.
"We report the discovery of AC-2168, a NIRCam-dark, millimeter-bright galaxy at zspec = 6.631 serendipitously detected in ALMA 2mm continuum and spectroscopically confirmed with NOEMA 1.2mm, ALMA 2mm and ALMA 3mm observations," the researchers write in the paper.
The nature of AC-2168
The newfound DSFG has a stellar mass of about 37 billion solar masses, star-formation rate at a level of 240 solar masses per year, and infrared luminosity of 1.6 trillion solar luminosities. Therefore, the astronomers note that AC-2168 is less active in star formation than the hyper-luminous DSFGs commonly seen in wide area blind surveys at redshifts of over 6.0.
The observations found that AC-2168 has a warm dust (with a temperature of about 60,000 K) and showcases compact dust emission. The mass of the galaxy was measured to be 40 billion solar masses, its gas fraction was calculated to be 52%, while its gas depletion time was estimated to be around 170 million years.
According to the authors of the paper, the obtained results in the case of AC-2168 point to a rapid and efficient mass assembly episode capable of producing compact, massive descendants on short timescales.
The observations also found no evidence of Lyman-alpha emitters or Lyman-break galaxies that could be clearly associated with AC-2168, which suggests a possible diverse environment hosting massive galaxies when the universe was a few billion years old.
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