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Unveiling the Structure of a Giant Spiral Galaxy with JWST and ALMA Observations

Introduction to ADF22.A1

An international team of astronomers used the James Webb Space Telescope (JWST) and the Atacama Large Millimeter/Submillimeter Array (ALMA) to observe the giant spiral galaxy ADF22.A1. Findings from this study, posted on arXiv on October 29, reveal detailed insights into the galaxy's inner structure.

About ADF22.A1: Location and Classification

• Redshift and Location: Positioned at a redshift on 3.09, ADF22.A1 is a massive barred spiral galaxy within the proto-cluster SSA22.
• Galaxy Classification: Earlier observations have identified it as a dusty star-forming galaxy (DSFG) with a naturally bright but heavily obscured active galactic nucleus (AGN).

Why ADF22.A1 is Key to Understanding Galaxy Evolution

A Laboratory for Understanding Massive Galaxies

Astronomers regard ADF22.A1 as a rare laboratory for investigating how massive galaxies and supermassive black holes (SMBHs) gather mass and evolve into giant elliptical galaxies.

Challenges in Observing ADF22.A1

Nevertheless, its structure and properties remain largely unknown due to significant dust extinction obscuring its rest-frame ultraviolet view.

The Role of JWST and ALMA in Observing ADF22.A1

Using Cutting-Edge Technology for Detailed Observations

For this reason, a team of astronomers, led by Hideki Umehata from Nagoya University in Japan, has utilized JWST and ALMA to study ADF22.A1, as these instruments provide the tools needed to examine the galaxy's structure and kinematics.

• Researcher Insights: The researchers noted, "The arrival of JWST and ALMA allows us to resolve the structure and kinematics of ADF22.A1, offering unparalleled insights into the physical processes that drive the evolution of massive galaxies."

Key Findings from the Observations of ADF22.A1

Structure of the Galaxy

• Spiral Structure: Observations conducted by Umehata's team uncovered a spiral-like-stellar structure in ADF22.A1, tracing emissions from the optical to near-infrared spectrum.
• Effective Radius: The galaxy's effective radius was measured at around 22,800 light-years, akin to that of local galaxies, indicating rapid size growth in the proto-cluster core.

Dust and Active Star Formation

• Compact Dusty Core: Additionally, observations revealed a bright, compact dusty core at the center of ADF22.A1, signaling an active growth phase of a proto-bulge.
• Dust Distribution: Unlike some ASFGs, the dust continuum here extends beyond the core, spreading throughout the disk.

Astronomers suggest that this indicates active star formation is also taking place within the disk, along with substantial dust production.

Rotation and Stellar Angular Momentum

• Rotation Velocity: Through the analysis of ionized carbon emission lines, the researchers determined the rotation velocity of ADF22.A1, which was found to be approximately 530 km/s.
• High Stellar Angular Momentum: They also discovered that the galaxy possesses a relatively high specific stellar angular momentum.

Conclusion: The Fast-Rotating Giant Spiral Galaxy ADF22.A1

Key Takeaways

In conclusion, the authors of the paper assert that ADF22.A1 is an exceptionally fast-rotating giant spiral galaxy, and propose that a specific mechanism must have quickly accelerated the galaxy's disk within just two billion years of the Big Bang.

Most Plausible Explanation

According to the scientists, the most plausible explanation is a combination of cold accretion and mergers.

Source

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