首页|Toward a Direct Measurement of the Cosmic Acceleration:The Pilot Observation of HⅠ 21 cm Absorption Line at FAST
Toward a Direct Measurement of the Cosmic Acceleration:The Pilot Observation of HⅠ 21 cm Absorption Line at FAST
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This study presents results on detecting neutral atomic hydrogen(HⅠ)21cm absorption in the spectrum of PKS PKS1413+13 at redshift z=0.24670041.The observation was conducted by FAST,with a spectral resolution of 10 Hz,using 10 minutes of observing time.The global spectral profile is examined by modeling the absorption line using a single Gaussian function with a resolution of 10 kHz within a 2 MHz bandwidth.The goal is to determine the rate of the latest cosmic acceleration by directly measuhng the redshift evolution of the HⅠ21 cm absorption line with Hubble flow toward a common background quasar over a decade or longer time span.This will serve as a detectable signal generated by the accelerated expansion of the Universe at redshift z＜1,referred to as redshift drift z or the SL effect.The measured HⅠ gas column density in this DLA system is approximately equivalent to the initial observation value,considering uncertainties of the spin temperature of a spiral host galaxy.The high signal-to-noise ratio of 57,obtained at a 10kHz resolution,strongly supports the feasibility of using the HⅠ 21 cm absorption line in DLA systems to accurately measure the redshift drift rate at a precision level of around 10-10 per decade.
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