William Atkins
Tuesday, 25 August 2009 19:52
Science -
Space
Page 2 of 3
In addition, they used the term initial mass function (IMF), which is defined as the mass distribution (different numbers of stars of different masses) of a population of stars in terms of their theoretical initial mass (as newborn stars).
Dr. Baerbel Koribalski, a member of the team, stated,
“All of these galaxies were detected with the Parkes telescope because they contain substantial amounts of neutral hydrogen gas, the raw material for forming stars, and this emits radio waves.” [CSIRO]
By using hydrogen gas, the different masses of the stars were able to be measured, without regards to the way the star was created and how it eventually evolved.
In fact, the astronomers measured FUV emissions and H-alpha emissions in 103 galaxies using NASA’s GALEX satellite and the 1.5-m CTIO optical telescope in Chile.
H-alpha emission traces the presence of very massive stars (O-type stars, brightest and most massive), which are born with masses more than 20 times that of the Sun.
The FUV emission measured both very massive stars and less massive stars (B-type stars, just below brightest and mass with respect to O stars, those with masses over three times that of the Sun but less than 20 solar-masses).
Dr. Meurer states,
“This is complicated work, and we’ve necessarily had to take into account many factors that affect the ratio of H-alpha to UV emission, such as the fact that B stars live much longer than O stars.” [CSIRO]
The CSIRO article concludes by stating,
“The team’s results allow a better understanding of other recently observed phenomena that have been puzzling astronomers, such as variation of the ratio of H-alpha to ultraviolet light as a function of radius within some galaxies. This now makes sense as the stellar mix varying as the pressure drops with radius (just like the pressure varies with altitude on the Earth).”
Also, it states,
“Importantly, the team also found that essentially all galaxies rich in neutral hydrogen seem to form stars.”
Dr. Meurer concludes,
“That means surveys for neutral hydrogen with radio telescopes will find star-forming galaxies of all kinds.”
Page three concludes with information from the paper.
