Milliarcsecond compact structure in radio quasars and the geometry of the universe. (arXiv:1708.08608v2 [astro-ph.CO] UPDATED)

Milliarcsecond compact structure in radio quasars and the geometry of the universe. (arXiv:1708.08608v2 [astro-ph.CO] UPDATED)
<a href="http://arxiv.org/find/astro-ph/1/au:+Cao_S/0/1/0/all/0/1">Shuo Cao</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Qi_J/0/1/0/all/0/1">Jingzhao Qi</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Biesiada_M/0/1/0/all/0/1">Marek Biesiada</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Zheng_X/0/1/0/all/0/1">Xiaogang Zheng</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Xu_T/0/1/0/all/0/1">Tengpeng Xu</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Pan_Y/0/1/0/all/0/1">Yu Pan</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Zhu_Z/0/1/0/all/0/1">Zong-Hong Zhu</a>

In this paper, by using the recently compiled set of 120
intermediate-luminosity quasars (ILQSO) observed in a single-frequency VLBI
survey, we propose an improved model-independent method to probe cosmic
curvature parameter $Omega_k$ and make the first measurement of the cosmic
curvature referring to a distant past, with redshifts up to $zsim 3.0$.
Compared with other methods, the proposed one involving the quasar data
achieves constraints with higher precision in this redshift range. More
importantly, our results indicate that the measured $Omega_k$ is in good
agreement with zero cosmic curvature, implying that there is no significant
deviation from a flat Universe. Finally, we investigate the possibility of
testing $Omega_k$ with a much higher accuracy using quasars observed in the
future VLBI surveys. It is shown that our method could provide a reliable and
tight constraint on the prior $Omega_k$ and one can expect the zero cosmic
curvature to be established at the precision of $DeltaOmega_ksim 10^{-2}$
with 250 well-observed radio quasars.

In this paper, by using the recently compiled set of 120
intermediate-luminosity quasars (ILQSO) observed in a single-frequency VLBI
survey, we propose an improved model-independent method to probe cosmic
curvature parameter $Omega_k$ and make the first measurement of the cosmic
curvature referring to a distant past, with redshifts up to $zsim 3.0$.
Compared with other methods, the proposed one involving the quasar data
achieves constraints with higher precision in this redshift range. More
importantly, our results indicate that the measured $Omega_k$ is in good
agreement with zero cosmic curvature, implying that there is no significant
deviation from a flat Universe. Finally, we investigate the possibility of
testing $Omega_k$ with a much higher accuracy using quasars observed in the
future VLBI surveys. It is shown that our method could provide a reliable and
tight constraint on the prior $Omega_k$ and one can expect the zero cosmic
curvature to be established at the precision of $DeltaOmega_ksim 10^{-2}$
with 250 well-observed radio quasars.

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