An international team of astronomers has made a significant advance in the study of galaxy formation by linking a particular class of distant galaxies with present-day spiral galaxies. The team of French, American, and Chilean astronomers believes that luminous compact galaxies, a type of galaxy common seven to ten billion years ago but rare today, are the direct predecessors of spiral galaxies such as the Milky Way. Their results, publicized this month, will be published in an upcoming issue of The Astrophysical Journal.
Illustration shows a sketchy sequence of compact galaxy morphologies on the right.
From the top picture to the bottom closely interaction are shown, and then formation of stars in bulges and finally in the disk. Spectra of some luminous compact galaxies, taken with one of the 8-meter mirrors of the European Southern Observatory's Very Large Telescope in Chile, revealed absorption lines from iron and other metals. The spectral signatures of the luminous compact galaxies closely match the spectra from the bulges of spiral galaxies. That coincidence, along with other observations of the shapes of such galaxies, led astronomers to conclude that luminous compact galaxies are the progenitors of current spiral galaxies, dating back to a time before the spiral arms formed. This work is the first to conclusively tie luminous compact galaxies to spiral galaxies, he said.