%0 Journal Article
%T The atomic gas of star-forming galaxies at z ¡« 0.05 as revealed by the Five-hundred-meter Aperture Spherical Radio Telescope
%A Bo Zhang
%A Cheng Cheng
%A Chuan He
%A Cong Kevin Xu
%A Edo Ibar
%A Gustavo Orellana-Gonz¨¢les
%A Hai Xu
%A Jia-Sheng Huang
%A Juan Molina
%A Marat Musin
%A Ming Zhu
%A Roger Leiton
%A Shumei Wu
%A Thomas M. Hughes
%A Tianwen Cao
%A Wei Du
%A Xu Shao
%A Y. Sophia Dai
%A Zijian Li
%J -
%D 2020
%R 10.1051/0004-6361/202038483
%X <i>Context.<i/> We report new H£¿I observations of four <i>z<i/>£¿¡«£¿0.05 VALES galaxies undertaken during the commissioning phase of the Five-hundred-meter Aperture Spherical Radio Telescope (FAST).<i>Aims.<i/> FAST is the largest single-dish telescope in the world, with a 500 m aperture and a 19-Beam receiver. Exploiting the unprecedented sensitivity provided by FAST, we aim to study the atomic gas content, via the H£¿I 21 cm emission line, in low-<i>z<i/> star formation galaxies taken from the Valpara¨ªso ALMA/APEX Line Emission Survey (VALES). Together with previous Atacama Large Millimeter/submillimeter Array (ALMA) CO(<i>J<i/>£¿=£¿1£¿0) observations, the H£¿I data provides crucial information to measure the gas mass and dynamics.<i>Methods.<i/> As a pilot H£¿I galaxy survey, we targeted four local star-forming galaxies at <i>z<i/>£¿¡«£¿0.05. In particular, one of them has already been detected in H£¿I by the Arecibo Legacy Fast ALFA survey (ALFALFA), allowing a careful comparison. We use an ON-OFF observing approach that allowed us to reach an rms of 0.7 mJy beam<sup>£¿1<sup/> at a 1.7 km s<sup>£¿1<sup/> velocity resolution within only 20 min ON-target integration time.<i>Results.<i/> In this Letter, we demonstrate the extraordinary capability of the FAST 19-beam receiver to push the detectability of the H£¿I emission line of extra-galactic sources. The H£¿I emission line detected by FAST shows good consistency with the previous Arecibo telescope ALFALFA results. Our observations are put into context with previous multi-wavelength data to reveal the physical properties of these low-<i>z<i/> galaxies. We find that the CO(<i>J<i/>£¿=£¿1£¿0) and H£¿I emission line profiles are similar. The dynamical mass estimated from the H£¿I data is an order of magnitude higher than the baryon mass and the dynamical mass derived from the CO observations, implying that the mass probed by dynamics of H£¿I is dominated by the dark matter halo. In one case, a target shows an excess of CO(<i>J<i/>£¿=£¿1£¿0) in the line centre, which can be explained by an enhanced CO(<i>J<i/>£¿=£¿1£¿0) emission induced by a nuclear starburst showing high-velocity dispersion
%U https://www.aanda.org/articles/aa/full_html/2020/06/aa38483-20/aa38483-20.html