Revisiting the Hubble constant, spatial curvature and cosmography with time-delay and cosmic chronometer observations

Abstract

In this work, we use a model-independent approach to determine the Hubble constant and the spatial curvature simultaneously. We use the cosmic chronometers in combination with the time delay measurements in this method, and the cosmography method is used to reconstruct distances from cosmic chronometer observations instead of the polynomial expansion. This approach avoids the problems of the physical meaning of polynomial coefficients and the calibration of "nuisance parameter". Our results show that the measured Hubble constant \(H_0=72.24^{+2.73}_{-2.52} km/s/Mpc\) is in good agreement with that derived from the local distance ladder measurement. In addition, our results show that a zero spatial curvature \(\Omega_k=0.062^{+0.117}_{-0.078}\) and an accelerating expansion of the Universe \(q_0=-0.645^{+0.126}_{-0.124}\) are supported by the current time delay of strong lensing system and cosmic chronometer observations. If we assume a flat universe in advance, we can infer that the \(H_0=70.47^{+1.14}_{-1.15} km/s/Mpc\), falls between the SH0ES and Plank CMB observation results. Moreover, the convergence and goodness of the fourth order fitting is worse than the third order fitting case. Finally, the cosmic expansion history is reconstructed within a wide range of redshifts.