Quasar radiation transforms the gas in a merging companion galaxy

Area of Science:

• Astronomy and Astrophysics
• Cosmic Evolution
• Galaxy Formation and Evolution

Background:

• Quasars are highly energetic objects powered by supermassive black hole accretion.
• Galaxy mergers are hypothesized to trigger quasar activity and influence surrounding gas.
• Observational data on these processes, especially in early universe, are limited.

Purpose of the Study:

• To investigate the interplay between quasars and gas in a major merging system at redshift z ≈ 2.7.
• To provide observational constraints on quasar ignition and feedback mechanisms.
• To understand how quasar radiation affects molecular gas properties in merging galaxies.

Main Methods:

• Observation of a major merging system at redshift z ≈ 2.7.
• Analysis of gas properties in proximity to a quasar.
• Characterization of molecular gas excitation, density, and size.

Main Results:

• A quasar in one galaxy was found to directly alter gas properties in a companion galaxy.
• Molecular gas near the quasar nucleus is highly excited and extremely compact (densities ~10^5-10^6 cm^-3, sizes <0.02 pc).
• This compact gas is significantly smaller than typically observed in non-quasar environments.

Conclusions:

• Major galaxy mergers play a crucial role in triggering quasar activity.
• Quasar radiation exerts localized negative feedback, profoundly altering internal gas structure.
• This disruption of molecular gas likely hampers star formation within merging galaxies.