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The Shanghai Astronomical Observatory found a case of a galaxy "escaping" 12.1 billion light-years away

via:环球网     time:2022/1/11 20:06:38     readed:108

On January 11, the reporter learned from the official website of the Chinese Academy of Sciences that the early universe and high redshift galaxy clusters of the Shanghai Astronomical Observatory analyzed the observation data of the Hubble Space Telescope (HST) deep-field GOODS-S.A galaxy with Lyman's ionized photon escape was found 12.1 billion light-years away (redshift 3.8).The discovery of this galaxy provides an ideal object for exploring the process by which galaxies drive the reionization of the universe.

It is reported that the relevant research results were published in The Astrophysical Journal Letters.

The work is mainly based on ultraviolet deep field HDUV data from the Hubble Space Telescope (HST). Zheng Zhenya, a researcher at the Shanghai Astronomical Observatory and a collaborator of the paper, said that the work further confirmed the research value of the ultraviolet deep field in space.

According to reports, the cosmic reionization process occurred about 13 billion years ago, involving the birth of the first generation of celestial bodies in the universe and the last major phase transition of the entire universe. In this process, the most abundant element in the universe, "hydrogen", becomes the whole ionization of hydrogen in the environment of overall neutral hydrogen, under the ionization of ultraviolet photons produced by first-generation stars, galaxies and black holes. Therefore, the study of cosmic reionization is one of the frontiers of current astronomy. Both the Webb (JWST) Space Telescope and the Next Generation Square Kilometre Array Radio Telescope (SKA) incorporate "cosmic reionization" into core science goals.

However, due to the absorption of intergalactic dielectrics and the weakening effect of flow signals as distance increases, scientists cannot directly observe the process by which Lyman ionization photons produced by galaxies during the cosmic reionization period ionize the surrounding neutral hydrogen.Therefore, in the problem of Lyman ionization photon escape in galaxies, it is limited to the study of more than a dozen cases of galaxies with Lyman ionization photon escape at the middle and low redshift (redshift 4 or less), which requires deep ultraviolet observation data to obtain the detection signal of the redshifted Lehmann ionization photon (the rest coordinate system wavelength is below 912 angstroms) to calculate the galaxy's ionization ability to neutral hydrogen, so as to understand the process of cosmic reionization.

In the study, researchers used space UV deep field data to systematically search a group of galaxies with strong emission lines, and found that one of the galaxies, CDFS-6664, had a signal-to-noise ratio of more than 5 on the Hubble UV deep field image.According to the redshift of the galaxy (3.797), the signal comes from Lyman ionizing photon radiation, indicating that the galaxy is more likely to have Lyman ionization photon escape.

Yuan Fangting, the first author of the paper and an associate researcher at the Shanghai Astronomical Observatory, introduced: "Through further research, we found that the spectral line shape and spectral energy distribution of the galaxy are in line with the characteristics of the Lyman ionization photon escape galaxy, and also found that the surrounding environment of the galaxy is relatively special, and the quasars such as ionization sources that exist near it are very likely to ionize the neutral absorbers in the direction of sight, making the Lyman ionophotons of the galaxy more easily observable than other galaxies." Combining this evidence, we believe that the galaxy belongs to a high-redshift Lehmann ionizing photon escape galaxy rarely observed in existing observations. ”

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