The function of a stellar primary mass varies with the mineral and the age of the stars, astronomers say

The function of stellar protomass varies with the metallicity and age of the stars

New research reveals that the mass of newly born stars (yellow, orange, and red circles represent stars from highest to lowest) varies with their metal abundance and when they were born (inner circle means born before). Credit: Wu Kun

In the vast and diverse universe, the initial distribution of mass at the birth of a new group of stars determines the fate of galaxies. This relationship is described by the initial mass function (IMF). For more than half a century, astronomers have assumed that the IMF is a global relationship, that is, that it is uniform throughout the universe.

However, in recent years, some indications point to this galaxies When star formation is particularly active, the IMF may be of a different shape than is often assumed in the Milky Way. But to fully verify these findings, astronomers will need to find more direct observational evidence in the Milky Way.

Now, based on the Large Sky Area Multi-Object Spectroscopic Fiber Telescope (LAMOST, also known as the Guo Shou Jing Telescope), a research team led by Professor Liu Zhao of the National Astronomical Observatories of the Chinese Academy of Sciences (NAOC) has found an important piece of direct evidence on how The International Monetary Fund differs in different environments.

This study has been published in nature On January 18th.

“The IMF varies with levels of metallic elements, and star clusters that were born earlier in the history of the universe have fewer Low mass stars “From the younger population,” said Li Jiadong, a doctoral student at NAOC and first author of the study.

Enumeration of stars in a given size is a direct and classic method of measuring the IMF of low-mass stars (red dwarfs), which mass distribution It does not evolve with time. This approach is essentially independent of models or assumptions.

The function of stellar protomass varies with the metallicity and age of the stars

The stellar initial mass function (IMF) describes the initial mass distribution of new stars in a population. Credit: NAOC

“Although many previous studies applied star counting to derive the IMF, two problems were not resolved. The first is that only a few stars were counted in the previous work. The second is that previous studies did not measure the metallicity of the stars.” said Professor Zhang Zhiyu, co-author of the study.

LAMOST provided spectra containing information about chemical compositionand the temperature and luminosity of millions of stars, allowing researchers to measure the metallicity of nearby red dwarf stars.

By choosing about 93,000 red dwarf Stars in catalogs from both the LAMOST and Gaia surveys, the researchers were able to group stars according to their metallicity and calculate the distribution of stellar mass in each group.

The study reveals the changing abundance of low-mass stars in our galaxy, the Milky Way, and sets a strong criterion for modeling star formation. The findings may also influence the results of chemical enrichment models for distant galaxies, as well as estimates of galaxy mass and planet formation efficiency.

“For example, the total stellar mass of galaxies is often estimated assuming the IMF to be constant, but if the IMF were to be variable, this could change estimates of the total mass of galaxies and potentially change the field of galactic astronomy.” Leo.

Professor Pavel Krupa, an IMF expert at the University of Bonn, Germany, commented on the results: “On the basis of a large well-observed ensemble of stars, the authors report that the IMF of late stars in the local galactic disk is dependent on metallicity and age. These The findings are critically important for addressing the universality of stellar IMF and enabling an in-depth understanding of potential transitions in stellar clusters that formed at different times and under different conditions in the galaxy.”

more information:
Zhao Liu, the stellar initial mass function varies with metal and time, nature (2023). DOI: 10.1038/s41586-022-05488-1.

the quote: The stellar primary mass function varies with the metal and age of the stars, astronomers say (2023, January 18) Retrieved January 18, 2023 from . programming language

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