**Unique Ultra-Luminous Infrared Galaxy Discovered Behind Cloverleaf Quasar**
*By Dwaipayan Roy | Oct 11, 2025, 05:28 pm*
—
An international team of astronomers has made a groundbreaking discovery of an ultra-luminous infrared galaxy (ULIRG) located behind the well-known Cloverleaf quasar, also known as H1413+117. This finding was achieved using the powerful Atacama Large Millimeter/submillimeter Array (ALMA) and has been detailed in the *Monthly Notices of the Royal Astronomical Society.*
### What Are ULIRGs and Why Are They Important?
ULIRGs are among the most intensely star-forming galaxies in the universe. Their intense infrared emissions make them crucial to understanding star formation in the early cosmos, especially those galaxies that are heavily obscured by dust and not visible in optical wavelengths.
### The Cloverleaf Quasar: A Brief Overview
The Cloverleaf quasar is a remarkable quadruply-lensed quasar with a redshift of approximately 2.56. It has long been a subject of interest due to its unique gravitational lensing and brightness, providing a valuable window into the distant universe.
### Discovering the New ULIRG
Led by astronomer Natsuki H. Hayatsu, the recent study revealed the presence of the ULIRG roughly six arcseconds away from the Cloverleaf quasar, sitting at a higher redshift of around 3.39. The galaxy boasts a massive molecular gas content, estimated between 40 to 230 billion solar masses, and harbors a black hole around 0.1 billion solar masses.
The ULIRG’s incredible energy output is evident in its total X-ray luminosity, measured to be about 4 x 10^44 erg/s (400 tredecillion erg/s), alongside an infrared luminosity reaching 2.8 trillion times that of our Sun.
### Insights into the Galaxy’s Evolution
Analysis of the galaxy’s molecular gas suggests it has not yet settled dynamically, a sign that it may be undergoing a gas-rich major merger. Such mergers can trigger intense starburst activity, and astronomers believe this galaxy is currently in such an active phase.
Furthermore, the team proposes that this ULIRG could represent an early stage in the evolutionary path leading to hot dust obscured galaxies (DOGs) or potentially evolving into naked active galactic nuclei (AGN).
### The Road Ahead: Future Research
Despite this remarkable discovery, the researchers emphasize the need for additional detailed studies focusing on the molecular gas properties of this galaxy. Understanding the physical state of the gas is critical to accurately determining its evolutionary status—whether it remains a massive starburst galaxy, evolves into a quasar, or transitions through other phases such as hot DOGs.
Future observational campaigns using ALMA and other instruments will aim to unveil these details, enhancing our understanding of galaxy evolution in the early universe.
—
*This discovery not only deepens our knowledge of star formation under extreme conditions but also highlights the dynamic and complex processes shaping galaxies billions of years ago.*
https://www.newsbytesapp.com/news/science/astronomers-discover-rare-galaxy-behind-famous-quasar-using-alma/story
