Infrared Galaxy Dynamics and Star Formation

Infrared observations reveal the energetic interplay between gas dynamics and star formation in galaxies enshrouded by dust. Molecular clouds collapse under gravity within unstable galactic discs, triggering bursts of star formation that heat surrounding dust and emit copiously at infrared wavelengths. High-resolution spectroscopy demonstrates that rotational transitions of molecules such as carbon monoxide (CO) and warm molecular hydrogen (H₂) trace kinematic structures from central nuclear discs to large-scale outflows, while mid-infrared features including polycyclic aromatic hydrocarbons and fine-structure lines diagnose the local radiation field and the balance between stellar and nuclear activity. In interacting and merging systems, dynamical torques funnel gas toward galactic centres, fuelling intense starbursts and occasionally active galactic nuclei (AGNs), which in turn can drive powerful feedback via radiation pressure and mechanical outflows. Quantifying the mass, temperature and velocity profiles of molecular gas reservoirs underpins models of galaxy evolution, as it links the efficiency of star formation to the availability of cold gas and to the mechanisms that regulate or quench further activity. This framework has global implications for understanding the peak epoch of cosmic star formation and the role of environmental factors in shaping galaxy populations across cosmic time.

Research from Nature Portfolio

A study has characterised the multi-wavelength luminosity budgets of galaxies with high infrared output, decomposing stellar, AGN and X-ray contributions across the electromagnetic spectrum. By applying advanced spectral energy distribution fitting tools, researchers derived robust estimates of the star formation rate, dust-to-gas mass ratios and intrinsic luminosities in a sample of ultra-luminous infrared galaxies. The analysis revealed strong correlations between intrinsic AGN power and both stellar and X-ray luminosities, indicating a co-evolutionary link between starburst activity and central black-hole growth. Moreover, obscured AGN systems displayed more rapid increases in infrared and X-ray outputs relative to their stellar components, emphasising the importance of dust attenuation in shaping observed galaxy properties.

Infrared Galaxy Dynamics and Star Formation publication trend

The graph below shows the total number of articles in infrared galaxy dynamics and star formation across all publications each year (not limited to Nature Index journals).

Technical terms

Ultraluminous Infrared Galaxy (ULIRG): A galaxy with infrared luminosity exceeding 10¹² solar luminosities, often driven by intense starburst or embedded AGN activity.

Active Galactic Nucleus (AGN): A compact region at a galaxy’s centre powered by accretion onto a supermassive black hole, emitting across the spectrum and influencing its host via feedback.

CO-to-H₂ conversion factor (α_CO): A proportionality constant used to infer molecular hydrogen mass from observed carbon monoxide line luminosity.

Polycyclic Aromatic Hydrocarbons (PAHs): Complex organic molecules whose infrared emission features trace photodissociation regions and star formation activity.

Molecular outflow: A flow of cold gas ejected from a galaxy’s central regions, driven by processes such as starburst winds or AGN feedback, which can regulate future star formation.

References

1. GOALS-JWST: Mid-infrared Spectroscopy of the Nucleus of NGC 7469. The Astrophysical Journal Letters (2023).
2. The CO-to-H2 conversion factor of molecular outflows. Astronomy & Astrophysics (2024).
3. Dissecting the Mid-infrared Heart of M83 with JWST. The Astrophysical Journal (2023).
4. Characterizing the luminosity components of luminous infrared galaxies in multi-wavelength from the X-ray to the far-infrared. Scientific Reports (2024).