Spectral survey of the LAMOST sky reveals the properties of stellar populations of galaxies

(ORDO NEWS) — From the data collected from the LAMOST Sky Survey, Wang Lili, a doctoral student at Dezhou University, China, and colleagues calculated the age and metallicity of stellar populations for approximately 43,000 galaxies from the 7th release of the LAMOST Spectral Sky Survey.

The data obtained were included in the LAMOST catalog, supplementing the available data on galaxies. The LAMOST (Large Sky Area Multi-Object Fiber Spectroscopic Telescope) survey of the sky is controlled by the National Astronomical Observatories of the Chinese Academy of Sciences.

Galaxies are systems of stars, gas and dust. The spectrum of galaxies in the optical range, which mainly consists of the light of hundreds of billions of stars, allows us to calculate the approximate distribution of stars by age and metallicity.

Based on the analysis of the spectra of stellar populations of the galaxy, it is possible to obtain new information about the formation of stars and the history of the chemical evolution of the galaxy.

A common method for analyzing stellar populations is to compare them with typical spectra, which represent the full spectrum of a galaxy. However, when applying this method, there are always uncertainties arising from inaccurate calibration of the radiation flux or high dust density in the galaxy.

In the new work, the researchers propose a method for comparison with typical spectra based on a comparison of individual small-scale structural elements of the spectrum to estimate the age and metallicity of galaxies in the LAMOST catalog.

This new method is based on separating the small-scale structures of the galaxy spectrum from the large-scale components and then comparing them with models of only small-scale structures that are not affected by the general shape of the continuous spectrum.

The results of several tests and comparisons confirmed that the properties calculated using this method are reliable.

“One of the advantages of this technique is that it is suitable for analyzing stellar populations of galaxies with an undefined radiation flux or spatially inhomogeneous dust attenuation, which is a big challenge for the classical method,” Wang said.

This work is the first estimate of the age and metallicity of galaxies from the LAMOST spectroscopic sky survey, which will play an important role in studying the physical properties of galaxies and galactic systems characterized by low redshifts.

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