宇宙の暗黒天体の撮影に成功（Astronomers image a mysterious dark object in the distant universe）

2025-10-09 マックス・プランク研究所

Overlay of the infrared emission (black and white) with the radio emission (colour). The dark, low-mass object is located at the gap in the bright part of the arc on the right-hand side.
© Keck/EVN/GBT/VLBA

＜関連情報＞

• https://www.mpg.de/25518363/1007-asph-astronomers-image-a-mysterious-dark-object-in-the-distant-universe-155031-x
• https://www.nature.com/articles/s41550-025-02651-2
• https://academic.oup.com/mnrasl/article/544/1/L24/8262431?login=false

重力画像法を用いて宇宙論的距離で太陽質量100万の天体を検出 A million-solar-mass object detected at a cosmological distance using gravitational imaging

D. M. Powell,J. P. McKean,S. Vegetti,C. Spingola,S. D. M. White & C. D. Fassnacht
Nature Astronomy  Published:09 October 2025
DOI:https://doi.org/10.1038/s41550-025-02651-2

Abstract

Structure on subgalactic scales provides important tests of galaxy formation models and the nature of dark matter. However, such objects are typically too faint to provide robust mass constraints. Here we report the discovery of an extremely low-mass object detected by means of its gravitational perturbation to a thin lensed arc observed with milli-arcsecond-resolution very long baseline interferometry. The object was identified using a non-parametric gravitational imaging technique and confirmed using independent parametric modelling. It contains a mass of m₈₀ = (1.13 ± 0.04) × 10⁶ M_⊙ within a projected radius of 80 pc at an assumed redshift of 0.881. This detection is extremely robust and precise, with a statistical significance of 26σ, a 3.3% fractional uncertainty on m₈₀ and an astrometric uncertainty of 194 μas. This is the lowest-mass object known to us, by two orders of magnitude, to be detected at a cosmological distance by its gravitational effect. This work demonstrates the observational feasibility of using gravitational imaging to probe the million-solar-mass regime far beyond our local Universe.

赤方偏移2.059のレンズ効果を受けたコンパクトな対称天体からの、拡張された極めて薄い重力弧 An extended and extremely thin gravitational arc from a lensed compact symmetric object at redshift of 2.059

J P McKean, C Spingola, D M Powell, S Vegetti
Monthly Notices of the Royal Astronomical Society: Letters  Published:09 October 2025
DOI:https://doi.org/10.1093/mnrasl/slaf039

ABSTRACT

Compact symmetric objects (CSOs) are thought to be short-lived radio sources with two lobes of emission that are separated by less than a kpc in projection. However, studies of such systems at high redshift are challenging due to the limited resolution of present-day telescopes, and can be biased to the most luminous objects. Here, we report imaging of a gravitationally lensed CSO at a redshift of 2.059 using very long baseline interferometry at 1.7 GHz. The data are imaged using Bayesian forward modelling deconvolution, which reveals a spectacularly extended and thin gravitational arc, and several resolved features within the lensed images. The surface brightness of the lensing-corrected source shows two mini-lobes separated by 642 pc in projection, with evidence of multiple hotspots that have brightness temperatures of 10^8.6 to10^9.2 K, and a total luminosity density of 10^26.3 W Hz^-1⁠. By combining the well-resolved radio source morphology with previous multiwavelength studies, we conclude that this object is likely a CSO of type 2, and that the properties are consistent with the bow-shock model for compact radio sources. Our analysis highlights the importance of combining high-quality data sets with sophisticated imaging and modelling algorithms for studying the high-redshift Universe.