Large spiral galaxies, such as our neighbour the Andromeda Galaxy, leave virtually no gas or dust particles unused during the formation of stars. Dutch astronomers calculated this based on the rotational speeds of more than one hundred nearby galaxies. The large galaxies achieve an efficiency of 80 to 100% and are therefore far more efficient than the maximum of 20% attributed to the previous record holders: medium-sized galaxies such as our Milky Way.
The new calculations also have implications for what is called the missing normal matter. For a long time, researchers have assumed that the universe consists of about 5% normal matter, such as atoms and molecules, and of 95% dark, unknown matter and dark, unknown energy. In addition, the majority of that 5% normal matter was missing. According to the new calculations, however, scarcely any normal matter is missing in the large spiral galaxies.
Scientists are now adjusting the theory to reflect the new findings. Finding some of the missing normal matter was a relief. However, the fact that large galaxies form stars far more efficiently than previously thought will give rise to other problems.
NGC 5371 is an example of a very efficient spiral galaxy. It is located about 100 million light years from Earth in the constellation Canes Venatici, which lies near the constellation Ursa Major. It is one of the heaviest of the more than 100 galaxies investigated. The galaxy contains almost no missing normal matter and has used virtually all of the dust and gas to produce stars. The Andromeda Galaxy, our nearest neighbour at just 2.5 million light years from Earth, also proved to be highly efficient.
The research was carried out by Lorenzo Posti (University of Groningen and University of Strasbourg, France), Filippo Fraternali (University of Groningen) and Antonino Marasco (University of Groningen and ASTRON) and will soon be published in the journal Astronomy and Astrophysics.
Peak star formation efficiency and no missing baryons in massive spirals. By Lorenzo Posti (University of Groningen and University od Strasbourg France), Filippo Fraternali (University of Groningen) & Antonino Marasco (University of Groningen and ASTRON). Accepted for publication in Astronomy & Astrophysics. (free preprint)
Photo: The spiral galaxy NGC 5371 is highly efficient and contains almost no missing normal matter. (c) SDSS/Fraternali
Original press release here (in Dutch only).