FAST has discovered a batch of the farthest neutral hydrogen galaxy samples to date. On May 10th, the relevant research results were published online in the Astrophysical Journal Newsletter.
Hydrogen is the earliest formed element in the universe, usually existing in the form of neutral hydrogen. Neutral hydrogen is an important component of gas circulation in galaxies, providing fuel for star forming regions, and is an important probe for exploring the dynamic structure of galaxies. Meanwhile, the neutral hydrogen rotation curve provides observational evidence for the existence of dark matter, laying the foundation for establishing a standard universe model.
The Australian Parkes 64 meter radio telescope searched for galaxies within 600 million light-years in the southern sky and detected approximately 5000 neutral hydrogen galaxies. The Arecibo 305 meter radio telescope in the United States searched for galaxies within 800 million light-years in the northern sky and detected approximately 30000 galaxies. These galaxy samples provide the mass distribution of neutral hydrogen galaxies, allowing astronomers to study the relationship between neutral hydrogen gas and stellar mass and star formation rate.
Peng Bo, a researcher at the National Astronomical Observatory of the Chinese Academy of Sciences, presided over the FAST ultra deep field sky survey project, which gives full play to FAST's high sensitivity and 19 beam receiver's advantages in large field of view to carry out deep "blind search" for distant and dim neutral hydrogen galaxies. Researchers discovered six neutral hydrogen galaxies at a distance of approximately 5 billion light-years during the pilot survey, which is the farthest sample of neutral hydrogen galaxies detected directly through a 21cm emission line to date. One galaxy has the largest neutral hydrogen mass to date. The team estimated the density of massive neutral hydrogen galaxies in the sample and found that there were more massive neutral hydrogen galaxies in the universe 4.2 billion years ago. The team utilized DESI spectral line data from collaborators and observed six optical counterparts of distant neutral hydrogen galaxies using Hale 5-meter, BTA 6-meter, and Keck 10-meter optical telescopes in multiple bands. This indicates that FAST provides a new way to detect distant neutral hydrogen galaxies in distant galaxy detection.
This work was completed in collaboration with the National Astronomical Observatory and the University of Western Australia in Australia.
Paper link
The black solid line represents the neutral hydrogen spectrum of the galaxy observed by FAST, the red solid line represents the fitting line, the blue solid line represents the optical spectrum, and the red dashed line represents the relative velocity of the optical counterpart.
The neutral hydrogen column density detected by FAST is superimposed on the tricolor map of the DESI Legacy Survey, where the red circle represents the size of the FAST beam at that redshift, and the enlarged optical counterpart is shown in the lower right corner.
Redshift is related to the time and distance of looking back. Display the time and co motion distance of the highest redshift galaxy discovered by each survey project at different data points.
