ブラックホール誕生の瞬間を観測（To ‘Infinity’ and beyond ― a look at a newborn black hole）

2025-07-15 イェール大学

イェール大学などの研究チームが、銀河衝突によって誕生した超大質量ブラックホールを「インフィニティ銀河」で発見。質量は約100万太陽質量で、銀河中心ではなく衝突構造の中間部に位置。これは巨大ガス雲が直接崩壊する「重い種（heavy seed）理論」を支持するもので、初期宇宙におけるブラックホール急成長の解明に貢献する。JWST、Keck天文台、Chandraなどのマルチ波長観測による成果で、『The Astrophysical Journal Letters』に掲載された。

The Infinity galaxy, observed with the James Webb Space Telescope. It is the result of a cosmic collision between two galaxies. The location of the possible newborn black hole is shown in the center, along with the two other black holes that were already present before the collision.　NASA, P. van Dokkum, G. Brammer

＜関連情報＞

∞銀河： 2つの巨大な環状核の間にある直接崩壊型超巨大ブラックホール候補 The ∞ Galaxy: A Candidate Direct-collapse Supermassive Black Hole between Two Massive, Ringed Nuclei

Pieter van Dokkum, Gabriel Brammer, Josephine F. W. Baggen, Michael A. Keim, Priyamvada Natarajan, and Imad Pasha
The Astrophysical Journal Letters Published: 2025 July 15
DOI:10.3847/2041-8213/addcfe

Abstract

We report the discovery of an unusual z = 1.14 object, dubbed the ∞ galaxy, in JWST imaging of the COSMOS field. Its rest-frame near-IR light is dominated by two compact nuclei with stellar masses of ∼10¹¹ M_⊙ and a projected separation of 10 kpc. Both nuclei have a prominent ring or shell around them, giving the galaxy the appearance of a figure eight or an ∞ symbol. The morphology resembles that of the nearby system II Hz 4, where the head-on collision of two galaxies with parallel disks led to the formation of collisional rings around both of their bulges. Keck spectroscopy, Very Large Array radio data, and Chandra X-ray data show that the ∞ galaxy hosts an actively accreting supermassive black hole (SMBH) with quasar-like radio and X-ray luminosity. Remarkably, the SMBH is not associated with either of the two nuclei but is in between them in both position and radial velocity. Furthermore, from excess emission in the NIRCAM F150W filter, we infer that the SMBH is embedded in an extended distribution of Hα-emitting gas, with a rest-frame equivalent width ranging from 400 Å to 2000 Å. The gas spans the entire width of the system and was likely shocked and compressed at the collision site in a galaxy-scale equivalent of what happened in the bullet cluster. We suggest that the SMBH formed within this gas in the immediate aftermath of the collision, when it was dense and highly turbulent. If corroborated with simulations and follow-up JWST spectroscopy, this would demonstrate that “direct” SMBH formation by a runaway gravitational collapse is possible in extreme conditions.