Forecast of Observing Time Delay of Strongly Lensed Quasars with the Muztagh-Ata 1.93 m Telescope

Abstract

As a completely independent method, the measurement of time delay of strongly lensed quasars (TDSL) are crucial to resolve the Hubble tension. Extensive monitoring is required but so far limited to a small sample of strongly lensed quasars. Together with several partner institutes, Beijing Normal University is constructing a 1.93m reflector telescope at the Muztagh-Ata site in west China, which has the world class observing conditions with median seeing of 0.82 arcsec and median sky brightness of 21.74 $\mathrm{mag} \operatorname{arcsec}^{-2}$ in V-band during the dark time. The telescope will be equipped with both a three-channel imager/photometer which covers $3500-11000$ Angstrom wavelength band, and a low-medium resolution ($\lambda/\delta\lambda=500/2000/7500$) spectrograph. In this paper, we investigate the capability of Muztagh-Ata 1.93m telescope in measuring time delays of strongly lensed quasars. We generate mock strongly lensed quasar systems and light curves with microlensing effects based on five known strongly lensed quasars, {\it i.e.}, RX J1131-1231, HE 0435-1223, PG 1115+080, WFI 2033-4723 and SDSS 1206+4332. In particular, RX J1131-1231 is generated with lens modeling in this work. Due to lack of enough information, we simulate the other 4 systems with the public data without lens modeling. According to simulations, for RX J1131-like systems (wide variation in time delay between images) the TDSL measurement can be achieved with the precision about $\Delta t=0.5$ day with 4 seasons campaign length and 1 day cadence. This accuracy is comparable to the up-coming TDCOSMO project. And it would be better when the campaign length keeps longer and with high cadence. As a result, the capability of Muztagh-Ata 1.93m telescope allows it to join the network of TDSL observatories. It will enrich the database for strongly lensed quasar observations and make more precise measurements of time delays, especially considering the unique coordinate of the site.

The Hubble constant tension: current status and future perspectives through new cosmological probes

“…Not only the theoretical scenarios have been called into question, but of course, the statistical analysis on the 𝐻 0 measurements constitutes a significant fraction of the literature regarding the Hubble tension [332][333][334][335][336][337][338][339][340][341][342]. The most tricky discussion concerning the Hubble tension must be done considering the probes used for its measurement: Cepheids [11,[343][344][345][346][347][348][349][350][351][352][353][354], SNe Ia , lensed objects [407][408][409][410][411][412][413][414][415][416][417], Cosmic Chronometers (CCs) [418][419][420][421], CMB [12,[422][423][424][425][426][427][428]…”