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Surprisingly mature galaxies in the early universe

Surprisingly mature galaxies in the early universe

A mosaic showing some of the galaxies observed by ALMA. The bright yellow areas are those where most stars form (the ionized carbon (C +) line makes it possible to see the formation of stars darkened by dust). The second image on the left in the top row shows a triple merge. Credit: Michele Ginolfi / ALPINE

When the universe was only one-tenth of its present age, its galaxies experienced a leap in growth. It was during this period that scientists in the ALPINE project focused when they used ESO̵

7;s ALMA telescope to perform the first-ever study of distant galaxies. To their surprise, these galaxies observed in the early stages of their lives were far more mature than expected. Their work is the subject of a series of articles published on October 27, 2020 in the journal Astronomy and astrophysics, signed, inter alia, by members of the CNRS and the University of Aix-Marseille.

Galaxies began to form very early in the history of the universe. Therefore, to study their childhood, we need to go back to the dawn of time, observing very distant galaxies. The ALPINE project focuses on a period between 1 and 1.5 billion years after the Big Bang, when the first galaxies experienced a phase of rapid growth. Although such distant galaxies have already been observed, for the first time so many of them have been studied systematically. Images of 118 massive galaxies obtained with the Hubble Space Telescope (visible light) and Spitzer (near infrared light), as well as spectra obtained with the VLT and Keck ground-based telescopes, were supplemented by 70 hours of observation with ALMA at submillimeter wavelengths (between infrared and radio waves).

ALMA can quantify dust, a sign of maturity in galaxies, and cold gas, which provides information about their growth rate and the number of stars they can form, as well as the motion of that gas, thus revealing galaxy dynamics. And this revealed some surprising data. To begin with, the observed galaxies proved to be very rich not only in cold gas, which feeds star formation, but also in dust, which is considered a by-product of stars at the end of their lives. So despite their young age, these galaxies have apparently seen the formation and death of the first generation of stars. The galaxies studied also show an astonishing variety of shapes: some are disordered, others already have a rotating disk that can end up as a spiral structure like the Milky Way, while others have been spotted in the process of merging. Another surprising observation is that some galaxies appear to emit gas, forming mysterious halos around themselves. Thus, the study raises a number of new questions about the early evolution of galaxies.

Surprisingly mature galaxies in the early universe

Illustration by an artist of a dusty spinning distant galaxy in the early universe. In this image, red represents gas and blue / brown represents dust, as seen in ALMA radio waves. Many other galaxies are seen in the background based on optical data from VLT and Subaru. Animated version: https://vimeo.com/467391159/ef7ec0f163. Credit: B. Saxton NRAO / AUI / NSF, ESO, NASA / STScI; NAOJ / Subaru

The galaxies in the baby’s universe were surprisingly mature

More information:
O. Le Fèvre et al., ALPINE-ALMA [CII] research, Astronomy and astrophysics (2020). DOI: 10.1051 / 0004-6361 / 201936965

Quote: Surprisingly Mature Galaxies in the Early Universe (2020, October 27) downloaded on October 29, 2020 from https://phys.org/news/2020-10-surprisingly-mature-galaxies-early-universe.html

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