Impact of the turnover in the high-z galaxy luminosity function on the 21-cm signal during Cosmic Dawn and Epoch of Reionization

The shape of the faint-end of the high-z galaxy luminosity function (LF) informs early star formation and reionization physics during the Cosmic Dawn and Epoch of Reionization. Until recently, based on the strong gravitational lensing cluster deep surveys, the Hubble Frontier Fields (HFF) has found a potential turnover in the ultraviolet (UV) LF at z similar to 6. In this paper, we analyse the contribution of extremely faint galaxies with the magnitude larger than the turnover magnitude in LF to cosmic reionization. We apply the measurement from HFF to our suppressed star formation efficiency model, including three free parameters: halo mass threshold M-t, curvature parameter beta, and a UV conversion factor l(UV). According to our fit of 68 per cent confidence level, the high-redshift star formation in haloes smaller than M-t = 1.82(-1.08)(+2.86) x 10(10) M-circle dot is found to be dampened. The turnover magnitude greater than or similar to -13.99 - 2.45, correspondingly the halo mass less than or similar to (4.57 + 20.03) x 10(9) M-circle dot. We find that the absorption trough in the global 21-cm signal is sensitive to our SFE model parameters. Together with (beta, l(UV)) = (2.17(-1.72)(+2.42), 9.33(-0.42)(+0.43) erg yr s(-1) M-circle dot(-1)), the trough locates at similar to 134(-17)(+10) MHz with an amplitude of similar to-237(+7)(-6) mK, compared to (106 MHz, -212 mK) in the absence of turnover. Besides, we find that the star formation of faint galaxies has also an impact on the 21-cm power spectra. The best-fitting peak power decreases by similar to 4 per cent and shifts towards smaller scales from 0.88 h Mpc(-1). to 0.91 h Mpc(-1). According to our calculation, such impact is distinguishable with the forthcoming Square Kilometre Array.