Discussion Overview
The discussion revolves around determining the Hubble constant using time delays observed in the gravitational lensing of the quasar QSO 0957+561. Participants explore how to extract time delay information from flux density data and Julian day entries, as well as how to relate this delay to the distance of the quasar.
Discussion Character
- Exploratory
- Homework-related
- Technical explanation
Main Points Raised
- One participant seeks guidance on calculating the time delay from flux densities and Julian days, indicating a need for clarity on the data analysis process.
- Another participant notes a visible pattern in the lightcurves of QSO 0957+561, suggesting that the time delay can be determined by counting Julian days between spikes in the lightcurves of the two images.
- A participant expresses interest in how to use the determined time delay to find the distance to the quasar, questioning the appropriateness of the equation they have for Dls, which relies on redshifts.
- One participant inquires about the angle between the two images, suggesting that understanding the geometry of the lensing could aid in calculating distances.
- Another participant confirms that the two images are 6 arcseconds apart and encourages creating a schematic to visualize the problem.
- There is a request for the redshift values associated with the lens and source, indicating their relevance to the calculations being discussed.
Areas of Agreement / Disagreement
Participants generally agree on the approach to finding the time delay and the importance of visualizing the data. However, there is no consensus on the specific methods to relate the time delay to the distance or the appropriate equations to use, as different participants suggest varying approaches.
Contextual Notes
Participants mention the need for redshift values and the angle between images, which are critical for calculations but have not been provided in the discussion. The discussion also reflects varying levels of familiarity with the topic, indicating potential gaps in knowledge among participants.
Who May Find This Useful
This discussion may be useful for students and researchers interested in gravitational lensing, cosmology, and the methods for calculating cosmological parameters from observational data.