Cosmology and Extragalactic Astronomy
Summary
Cosmology seeks to describe the large-scale origin, content and fate of the Universe, while extragalactic astronomy extends these questions into the formation, evolution and interactions of galaxies beyond our own. A modern picture begins with a hot big bang about 13.8 billion years ago, followed by an early radiation-dominated epoch in which light elements were synthesised and a relic cosmic microwave background (CMB) was released. As the cosmic expansion slowed, matter clustered under gravity into dark-matter haloes that seeded galaxy formation. Gas cooled within these haloes to form stars and supermassive black holes, whose feedback regulated subsequent growth. Observations of galaxy morphology, kinematics and star-formation histories across cosmic time trace the interplay of dark matter, baryons and black-hole activity. Meanwhile, precision measurements of the CMB, large-scale structure and Type Ia supernovae constrain the matter content, dark-energy properties and geometry of space. Today, cosmology and extragalactic astronomy unite detailed studies of individual galaxies with statistical surveys across the sky, offering a coherent account of how structure emerged from primordial fluctuations and how galaxies and their central engines have co-evolved throughout the history of the Universe.
Research from Nature Portfolio
New evidence shows that the mass of a galaxy’s central black hole is the dominant predictor of its atomic‐to‐stellar mass ratio, implying that accretion-driven feedback chiefly governs the cold-gas content and thus the late-time star-formation activity of massive galaxies. Direct measurements of HI reservoirs reveal a stronger correlation with black‐hole mass than with stellar mass or bulge properties, lending support to models in which black-hole energy input ejects or heats the cool gas.
Laboratory experiments and theoretical modelling have overturned long-held views on molecular hydrogen formation in interstellar environments. Carbonaceous dust grains, including polycyclic aromatic hydrocarbons, sustain efficient H₂ synthesis at surface temperatures up to ~ 250 K. This high-temperature pathway increases H₂ availability in warmer molecular clouds, altering predictions for cloud collapse and star-formation efficiencies in both local and high-redshift galaxies.
Cosmology and Extragalactic Astronomy publication trend
The graph below shows the total number of articles in cosmology and extragalactic astronomy across all publications each year (not limited to Nature Index journals).
Technical terms
Dark energy: The unknown component driving the accelerated expansion of the Universe, typically characterised by negative pressure.
Cosmological constant (Λ): The simplest form of dark energy, a uniform energy density appearing as a constant term in Einstein’s field equations.
Equation-of-state parameter (w): The ratio of pressure to energy density of a cosmological fluid; w = –1 denotes a perfect cosmological constant.
Coupling parameter: A dimensionless factor describing the strength and direction of energy or momentum exchange between dark matter and dark energy.
Convolutional neural network (CNN): A deep-learning architecture employing convolutional filters to extract spatial features from images.
Transformer: A neural-network model using self-attention mechanisms to capture long-range dependencies in data.
Autoencoder: A neural network trained to compress and reconstruct data, facilitating unsupervised feature learning.
References
- Black holes regulate cool gas accretion in massive galaxies. Nature (2024).
- Enhanced star formation through the high-temperature formation of H2 on carbonaceous dust grains. Nature Astronomy (2023).
- Galaxy morphology classification based on Convolutional vision Transformer (CvT)★. Astronomy & Astrophysics (2024).
- Similar Image Retrieval using Autoencoder. I. Automatic Morphology Classification of Galaxies. Publications of the Astronomical Society of the Pacific (2023).
- The Classification of Galaxy Morphology in the H Band of the COSMOS-DASH Field: A Combination-based Machine-learning Clustering Model. The Astrophysical Journal Supplement Series (2023).
- Dark sector interaction: a remedy of the tensions between CMB and LSS data. European Physical Journal C (2019).
- Interacting Dark Energy after DESI Baryon Acoustic Oscillation Measurements. Physical Review Letters (2024).
- Model-independent reconstruction of the interacting dark energy kernel: Binned and Gaussian process. Journal of Cosmology and Astroparticle Physics (2023).
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