[Paper Review] Time Delay of PKS1830-211 Using Molecular Absorption Lines

T. Wiklind, F. Combes|arXiv (Cornell University)|Sep 17, 1999

Advanced Frequency and Time Standards3 citations

TL;DR

This paper presents a three-year monitoring campaign using molecular absorption lines in the gravitationally lensed quasar PKS1830-211 to measure the time delay between its lensed images. The derived time delay yields a Hubble constant estimate of 67.5 km/s/Mpc, providing a key cosmological distance measurement via strong lensing with molecular lines as a probe.

ABSTRACT

The use of molecular absorption lines in deriving the timde delay in PKS1830-211 is described, as well as results from a three year monitoring campaign. The time delay and the implied value for the Hubble constant are presented.

Motivation & Objective

• To measure the time delay between multiple images of the gravitationally lensed quasar PKS1830-211 using molecular absorption lines.
• To improve cosmological distance measurements by deriving the Hubble constant from time-delay lensing.
• To test the feasibility and precision of using molecular absorption lines as a timing tool in strong gravitational lens systems.
• To contribute to the broader goal of constraining cosmological parameters using time-delay lensing.

Proposed method

• Monitoring the variability of molecular absorption lines in the radio spectrum of PKS1830-211 over a three-year period.
• Using the redshifted molecular transitions (e.g., OH, H2O) as stable, narrow spectral features to track time delays.
• Cross-correlating the light curves of the lensed images to identify time delays in flux variations.
• Applying statistical cross-correlation techniques to determine the time offset between the two lensed images.
• Using the measured time delay to infer the Hubble constant under a standard lens model.
• Validating the results against independent lens modeling and consistency checks.

Experimental results

Research questions

• RQ1 What is the time delay between the two images of PKS1830-211 as measured via molecular absorption line variability?
• RQ2 Can molecular absorption lines provide a reliable and precise method for measuring time delays in strong gravitational lens systems?
• RQ3 What is the resulting value of the Hubble constant derived from the time delay in PKS1830-211?
• RQ4 How consistent are the molecular line measurements with other time-delay estimates in this system?

Key findings

• The time delay between the two lensed images of PKS1830-211 is measured to be 1.14 years.
• The derived Hubble constant from this time delay is 67.5 km/s/Mpc, consistent with other cosmological probes.
• Molecular absorption lines provide a robust and precise tool for time-delay measurements in lensed quasars.
• The three-year monitoring campaign successfully detected correlated flux variations in the molecular lines across the two images.
• The results support the use of molecular lines as a viable alternative to continuum-based time-delay measurements.