8/10/2023 0 Comments Hydrogen line emission spectrum![]() ![]() They found that many of them are very bright at 5.6 microns, indicating that a very prominent H-alpha emission line is present in these sources.įirst author Pierluigi Rinaldi says, "This research opens up the possibility of studying early galaxies in a way not possible before. Then they analyzed images of these preselected galaxies at longer wavelengths with MIRI. The researchers first searched for star-forming galaxies that might have emission lines at the time of reionization, based on their analysis of the more sensitive NIRCam images. The researchers also used ancillary data from HST in the Hubble eXtreme Deep Field (XDF). The ultra-deep MIRI image used in this study was obtained within the so-called MIRI European Guaranteed Time. MIRI is an important tool for this research, as is one of the other four instruments on Webb, NIRCam. H-alpha is not affected by the opacity of the intergalactic medium and thus allows astronomers to study star formation in these early galaxies. At high redshifts, previous studies have relied on the analysis of another prominent spectral line called Lyman-alpha, but this line becomes very faint or is generally not present at all in galaxies in the cosmic dawn because it is absorbed by the intergalactic medium, which is mostly opaque in that early period. Little is known about galaxies in the Epoch of Reionization. The research by Rinaldi and colleagues shows for the first time that a detailed study of star formation in early galaxies is possible and can be carried out with JWST/MIRI. The H-alpha line has now been studied-with the MIRI instrument on JWST-for the first time for galaxies with a redshift higher than seven (z>7) during the cosmic dawn, the period less than a billion years after the Big Bang, during which neutral hydrogen gas ionized. ![]() For galaxies with high redshift, this optical line is shifted to longer wavelengths, to the near- and mid-infrared. The best tracer to measure the level of star formation is the H-alpha emission line in the optical spectrum. Star-forming galaxies produce a large amount of UV photons, but during the Epoch of Reionization these photons are absorbed by the intergalactic medium. ![]()
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