Research into the gas accretion and star-formation histories of Milky Way-mass galaxies from 9 billion years ago provides crucial insights into the evolution of galaxies. This study sheds light on the conditions that prevailed in the early universe and how they compare to the present day. Let’s delve into the key findings and implications of this groundbreaking research.
What are the Gas Accretion and Star-Formation Histories of Milky Way-Mass Galaxies 9 Billion Years Ago?
The study focuses on galaxies at redshifts z=1.2-1.3, which exhibit properties similar to the progenitors of Milky Way-mass galaxies. It is observed that 9 billion years ago, these galaxies were forming stars at a rate 30 times faster than today. This rapid star formation is indicative of a rich molecular gas reservoir, a stark contrast to the low gas fractions seen in present-day Milky Way-mass galaxies (<10%).
The detection of large molecular gas masses in these ancient galaxies challenges our previous understanding of the evolution of galactic gas content. The CO(J=3-2) emission measurements reveal molecular gas masses that are comparable to or even exceed the stellar masses of these early galaxies. This suggests that the majority of baryons in these galaxies existed in the form of cold gas, rather than stars at this early cosmic epoch.
What is the Significance of Detecting Large Molecular Gas Masses in Galaxies at Redshifts z=1.2-1.3?
The detection of large molecular gas masses in galaxies at z=1.2-1.3 is significant as it provides valuable insights into the early stages of galaxy evolution. These observations indicate that galaxies in the early universe possessed substantial reservoirs of molecular gas, which facilitated the intense star formation rates observed at that time.
The presence of such significant amounts of molecular gas challenges existing models of galaxy evolution and necessitates a reevaluation of our understanding of the processes that govern gas accretion and star formation in galaxies throughout cosmic history.
How Does the Star-Formation Efficiency in Distant Galaxies Compare to That in Local Galaxies?
The study finds that the star-formation efficiency in distant galaxies remains relatively constant since redshift z=1.2, despite a considerable decrease in gas fraction. This suggests that the physical mechanisms responsible for the cooling of gas and subsequent star formation in distant galaxies are akin to those operating in present-day local galaxies.
Additionally, the comparison of star-formation efficiencies between distant and local galaxies reveals intriguing parallels in the processes driving star formation, indicating a remarkable consistency in the fundamental mechanisms that regulate this essential aspect of galaxy evolution.
In conclusion, the research on large molecular gas reservoirs in progenitors of Milky Way-mass galaxies from 9 billion years ago offers profound insights into the early universe’s galactic evolution. By studying the gas accretion and star-formation histories of these ancient galaxies, astronomers deepen their understanding of the fundamental processes that shape galaxies across cosmic epochs.
To read the full research article, please visit arXiv.org.
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