ADF22-WEB: A giant barred spiral starburst galaxy in the z = 3.1 SSA22 protocluster core

TL;DR

This paper presents detailed observations of a massive, rotating spiral galaxy at z=3.1 within a proto-cluster, revealing insights into early galaxy growth, angular momentum acquisition, and potential evolution into a massive elliptical.

Contribution

It provides the first detailed kinematic and morphological analysis of a giant spiral galaxy in a high-redshift proto-cluster, highlighting mechanisms like cosmic web accretion and bar-driven evolution.

Findings

Galaxy has a rotation velocity of 530 km/s and diameter >30 kpc.

High specific angular momentum indicates effective spin-up via cosmic web accretion.

Galaxy likely evolves into a massive elliptical with reduced angular momentum after mergers.

Abstract

In the present-day universe, the most massive galaxies are ellipticals located in the cores of galaxy clusters, harboring the heaviest super-massive black holes (SMBHs). However the mechanisms that drive the early growth phase and subsequent transformation of these morphology and kinematics of galaxies remain elusive. Here we report (sub)kiloparsec scale observations of stars, gas, and dust in ADF22.A1, a bright dusty starburst galaxy at z=3.1, hosting a heavily obscured active galactic nucleus and residing in a proto-cluster core. ADF22.A1 is a giant spiral galaxy with the kinematics of a rotating disk with rotation velocity Vrot=530+/-10km/s and diameter larger than 30 kpc. The high specific stellar angular momentum of this system, j*=3400+/-600 kpc km/s, requires a mechanism to effectively spin-up ADF22.A1, indicating the importance of accretion from the cosmic web to supply both gas and angular momentum to galaxies in their early gas-rich starburst phase. In its inner region, gas flows along dust lanes in a bar connected with the bright dusty core and the estimated mass ratio of a bulge to SMBH matches the local relation, suggesting that bars are a key mechanism to shape the early co-evolution of these components. Comparison with cosmological simulations shows that ADF22.A1 will likely evolve into a massive elliptical at the present day, experiencing a significant reduction in angular momentum associated with subsequent galaxy mergers.