The movie of Milky Way

The more accurate reconstruction of the history of star formation in galaxies similar to our offers us the best vision of what may have happened in the course of billions of years, even in the Milky Way.
A kind of ‘film’ made up of many frames, about 2,000, each representing a snapshot of the state of evolution of spiral galaxies in very remote epochs. A history that goes back in time up to ten billion years ago, the team of researchers led by Casey Papovich (Texas A & M University in College Station, United States) has patiently reconstructed from the images collected from various space telescopes and ground, in different wavelength. From ultraviolet to the far infrared, the scientists combined the Hubble and Spitzer observations of NASA, the European Space Agency’s Herschel and the Magellan Baade Telescope Observatory Las Campanas, the Chilean Andes to get their results.


Credit: NASA, ESA, and Z. Levay (STScI)

“This study allows us to see how we would look the Milky Way in the past,” says Papovich. “This shows that these galaxies have undergone a great change in the mass of their stars over the past 10 billion years, increasing tenfold, which confirms the theories on their growth. And most of this growth of stellar mass took place in the first 5 billion years after the formation of galaxies.”
The data collected and analyzed show that these galaxies, and most likely also the Milky Way, have experienced their maximum growth between 9.2 and 10 billion years ago, churning out new stars to the dizzying pace of 30 every year, tens times more than what we record today in our Galaxy. The study, just published in The Astrophysical Journal, reinforces previous research that has shown how the Milky Way and galaxies similar to it, initially, were composed of small groups of stars and have achieved considerable masses ‘swallowing’ large amounts of gas. This accretion of matter has given it the considerable increase in the rate of star formation within them recorded in ancient times.



For Paola Santini, researcher INAF – Astronomical Observatory of Rome and winner along with Gian Paolo Fadini of the first edition of the “Young Researchers Award Italian” organized the group in 2003 for Scientific Research, “the analysis of Papovich and employees represents a step further to understand the complex process of evolution of galaxies. The authors of the work have used observations of extragalactic survey such deep candels, project that also here the Astronomical Observatory of Rome, we are actively involved. Such survey works as “time machines”, allowing us to look at what they look like at different ages, the galaxies that populate the universe today. The ultimate goal of the analysis is to understand the physical processes by which galaxies have evolved up to today show certain properties. ”
“Using data at different frequencies, which allow you to analyze the various components of galaxies, Papovich and collaborators show that galaxies like the Milky Way or Andromeda have gone through similar evolutionary stages, simply routes a bit ‘in advance from largest mass galaxies ‘ continues Santini. “These galaxies have experienced a phase of star formation modest, followed by a more intense and much obscured by dust, and finally have gradually transformed into passive galaxies, changing their morphology in a spherical shape and showing a net decrease in their activity star formation. Necessary to wait for new data, for example by the telescope ALMA, to determine if this transformation is due to exhaustion of the gas, the main ingredient for the formation of new stars, or the decrease of the efficiency of the conversion process gas into stars, or finally to a combination of these two phenomena. “

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