Mysterious infrared light from space resolved perfectly
|Artist's impression of the Cosmic Infrared Background resolved with ALMA |
[Credit: NAOJ, Fujimoto et al.]
The origins of the first two have already been revealed. The COB comes from a huge number of stars, and the CMB comes from hot gas just after the Big Bang. However, the origin of the CIB was still to be solved. Various research projects, including past ALMA observations, have been conducted, but they could only explain half of the CIB.
A research team led by a graduate student, Seiji Fujimoto, and an associate professor, Masami Ouchi, at the University of Tokyo, tackled this mysterious infrared background by examining the ALMA data archive. ALMA is the perfect tool to investigate the source of the CIB thanks to its unprecedented sensitivity and resolution.
|Examples of faint objects seen with ALMA (red contour) and the Subaru Telescope (color). |
ALMA detects emissions from dust in galaxies observed in optical/infrared
[Credit: ALMA (ESO/NAOJ/NRAO), NAOJ, Fujimoto et al.]
"The origin of the CIB is a long-standing missing piece in the energy coming from the Universe," said Seiji Fujimoto, now studying at the Institute of Cosmic Ray Research, the University of Tokyo. "We devoted ourselves to analyzing the gigantic ALMA data in order to find the missing piece."
Finally, the team discovered 133 faint objects, including an object five times fainter than any other ever detected. The researchers found that the entire CIB can be explained by summing up the emissions from such objects.
|60 percent of them have corresponding optical/infrared galaxies, whereas the remaining |
40 percent are invisible in other wavelength [Credit: ALMA (ESO/NAOJ/NRAO),
NAOJ, Fujimoto et al.]
"However, we have no idea what the rest of them are. I speculate that they are galaxies obscured by dust. Considering their darkness, they would be very low-mass galaxies." Masami Ouchi explained passionately. "This means that such small galaxies contain great amounts of dust. That conflicts with our current understanding: small galaxies should contain small amounts of dust. Our results might indicate the existence of many unexpected objects in the distant Universe. We are eager to unmask these new enigmatic sources with future ALMA observations."
The findings have been published in The Astrophysical Journal Supplement Series.
Source: National Institutes of Natural Sciences [March 10, 2016]