LifetimeOfQuasars

This repository provides a simple code to estimate the quasar formation rate using data from the Sloan Digital Sky Survey.

Disclaimer

I am not an astronomer, so the calculation method may be wrong. Use the code at your own risk.

Key Ideas

1. Quasar Lifetime:

   • The accepted lifetime of quasars is approximately 55 million years.
   • Few papers discuss quasar lifetime estimation. One notable reference is Quasar Clustering and the Lifetime of Quasars.
   • You can adjust this value in the code to explore its impact.

2. Data Collection:

   • Quasar redshifts (z) are queried from the SkyServer.
   • Due to a server limit of 500,000 rows per query, the Universe's lifetime is divided into subranges, and queries are run for each subrange sequentialy.
   • The results are merged into a single dataset. A full list of approximately 750,000 quasars is available as quasars.json.
   • The code uses this file if it exists. To regenerate it, delete the local copy and re-run the code.

3. Quasar Birth Rate Estimation:

   • The quasar birth rate is calculated approximately.

The code

Python code is available as quasar_ages.py

Requirements to be installed is available here.

Results

Age of the Universe: measured in billions of years (Gyr).
Birth Rate: measured in quasars per billion years (Gyr^-1).

The quasar birth rate peaks approximately 2 billion years after the Big Bang and then declines sharply. Negative values arise due to errors in approximating the derivative using finite differences on a grid with a limited number of time points.