The First FAST detection of neutral hydrogen emission from extragalactic galaxies

The Five-hundred-meter Aperture Spherical Radio Telescope (FAST) is the largest telescope with the highest sensitivity in the world. Extragalactic neutral hydrogen detection is one of important scientific goals of FAST.

 

Recently, an international research team led by Dr. Cheng Cheng from Chinese Academy of Sciences South America Center for Astronomy (CASSACA) successfully detected the neutral hydrogen line emission from three local galaxies using the FAST 19-beam receiver with only five minutes of exposure. The research paper is recently published in Astronomy & Astrophysics Letter. This is the first publication on FAST observation of extragalactic neutral hydrogen.


Fig. 1. The optical color images of the four galaxies for FAST observation. The red contours are the previous CO observation by ALMA. The white spectra in each panel are the results from FAST.

 

Neutral hydrogen gas is the most extended baryons in galaxies, while cold gas traced by CO is more concentrated to a galaxy center (red contour in Figure 1). With dynamical measurements of neutral hydrogen and CO, we can estimate the mass distribution of galaxies at different radii. Dynamical masses of these four galaxies estimated from the newly observed neutral hydrogen line are 10 times higher than the observed baryon masses, indicating contribution of dark matter. On the other hand, dynamical masses estimated using previous CO observations were equivalent to their observed baryon masses. Therefore, the new FAST observation illustrates its ability of studying dark matter in galaxies using the neutral hydrogen 21cm emission line.

 

The FAST observation of these galaxies was an important part of an international research project, the Valparaíso ALMA Line Emission Survey (VALES), led by Prof. Edo Ibar from Valparaiso University in Chile. The VALES is a project of observing star forming galaxies using first-class international facilities such as SDSS, Herschel space observatory, ALMA, APEX and VLT. This international team has been publishing a series of scientific results.

 

FAST with the unpreceded sensitivity provides a very unique chance to observe the extra-galactic neutral hydrogen, and therefore has been adding to the list modern astronomical facilities used by this international collaboration. The FAST observation time was awarded in the Share-risk Observing call during the FAST Commissioning Phase. The team will apply for FAST time to further study the neutral hydrogen properties of VALES galaxies.


The paper can be accessed at https://www.aanda.org/articles/aa/full_html/2020/06/aa38483-20/aa38483-20.html

Related accessories
Related documents
China's FAST telescope officially opens to world
China's FAST telescope identifies over 300 pulsars
Staff carry out regular maintenance operation to FAST in Guizhou
China's FAST telescope to officially open to global astronomers
World’s most sensitive radio telescope concludes 15-month listening session, accepting international proposals
China's FAST telescope will be available to foreign scientists
FAST Reveals Mystery of Fast Radio Bursts from the Universe
FAST telescope IDs 132 pulsar candidates
China's FAST telescope detects extragalactic neutral hydrogen for dark matter study
FAST Discovery of an Eclipsing Binary Millisecond Pulsar in Globular Cluster M92
World's largest radio telescope starts formal operation
China Sky Eye, the world’s largest single-dish radio telescope, is now fully operational
FAST scope to search for planets like Earth
Scientists expect astronomical breakthroughs with FAST
A Journey to FAST: The Eye of Heaven
FAST Helps Reveal the Origin of Fast Radio Bursts
A Tribute to Arecibo
FAST Detects Multiple Bursts from FRB 121102
Two phase formation of galaxies
A New Study Verifies the Role of Angular Momentum in Molecular Clouds
Copyright © National Astronomical Observatories, Chinese Academy of Sciences
Address: 20A Datun Road, Chaoyang District, Beijing, China code: 100012
Tel: 010-64888708 E-mail: naoc@nao.cas.cn