The first billion years of cosmic history represents the final frontier in assembling a coherent physical picture of early galaxy formation, and a remarkable progress in this area has been made in the last few years. We have carried out a detailed analysis of a gravitationally lensed galaxy A2744_YD4 at z = 8.38 behind the massive galaxy cluster Abell 2744. The photometric redshift of about 8, estimated from HST, VLT and Spitzer data, was confirmed by the detection of the Ly_alpha line at a redshift of z=8.38 in a deep VLT X-SHOOTER spectrum. The follow-up observations with the Atacama Large Millimeter/submillimeter Array (ALMA) detected a significant 1 mm continuum flux indicative of the presence of dust in a very young star-forming galaxy. The ALMA spectrum showed also ionized oxygen at the same redshift. This is the most distant, and hence earliest, detection of dust and oxygen in the Universe. A2744_YD4 contained an amount of dust equivalent to 6 million times the mass of our Sun, a total stellar mass of 2 billion times the mass of our Sun, and a star formation rate ~ 20 solar masses per year. The detection of dust in this early epoch of the Universe provides key information on when the first supernovae exploded and hence the time when the first stars appeared in the Universe.
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In the 90s, the COBE satellite discovered that not all the microwave emission from our Galaxy behaved as expected. Part of this signal was later assigned to a fresh new emission component, spatially correlated with the Galactic dust emission, which showed greater importance in the microwave range of frequencies. It has been named since as “anomalous microwave emission”, or AME. The current main hypothesis to explain the AME origin is that it is emitted by small dust particles which undergo fast spinning movements. In Fernández-Torreiro et al. (2023), we study the observational properties of
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Stellar ages are key to several fields of astrophysics such as exoplanet research, galactic-archeology, and of course stellar physics. Obtaining the ages of stars is however not straightforward and requires stellar modeling. The most widely used technique only requires stellar colors or temperature and surface gravity, but the uncertainties are quite large. This technique is most efficient for stars belonging to clusters, as they were born from the same molecular cloud and share the same ages. In the last decades, based on the study of stellar acoustic waves, asteroseismology became the most
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H II regions are ionized nebulae associated with the formation of massive stars. They exhibit a wealth of emission lines in their spectra that form the basis for estimation of chemical composition. The amount of heavy chemical elements is essential to the understanding of important phenomena such as nucleosynthesis, star formation and chemical evolution of galaxies. For over 80 years, however, a discrepancy exists of a factor of around two between heavy-element abundances (the so-called metallicity) derived from the two main kinds of emission lines that can be measured in nebular spectra
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