Transformational astrophysics and exoplanet science with Habitable Worlds Observatory's High Resolution Imager
Authors:
Vincent Van Eylen,
Richard Massey,
Saeeda Awan,
Jo Bartlett,
Louisa Bradley,
Andrei Bubutanu,
Kan Chen,
Andrew Coates,
Mark Cropper,
Ross Dobson,
Fabiola Antonietta Gerosa,
Emery Grahill-Bland,
Leah Grant,
Daisuke Kawata,
Tom Kennedy,
Minjae Kim,
Adriana Adelina Mihailescu,
Jan-Peter Muller,
Georgios Nicolaou,
Mathew Page,
Paola Pinilla,
Louisa Preston,
Ted Pyne,
Hamish Reid,
Santiago Velez Salazar
, et al. (146 additional authors not shown)
Abstract:
Habitable Worlds Observatory (HWO) will be NASA's flagship space telescope of the 2040s, designed to search for life on other planets and to transform broad areas of astrophysics. NASA are seeking international partners, and the UK is well-placed to lead the design and construction of its imaging camera - which is likely to produce the mission's most visible public impact. Early participation in t…
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Habitable Worlds Observatory (HWO) will be NASA's flagship space telescope of the 2040s, designed to search for life on other planets and to transform broad areas of astrophysics. NASA are seeking international partners, and the UK is well-placed to lead the design and construction of its imaging camera - which is likely to produce the mission's most visible public impact. Early participation in the mission would return investment to UK industry, and bring generational leadership for the UK in space science, space technology, and astrophysics.
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Submitted 18 December, 2025;
originally announced December 2025.
Ripples in the baryon to dark matter ratio in $Λ$CDM: implications for galaxy formation
Authors:
Owen Jessop,
Adrian Jenkins,
Andrew Pontzen,
Joop Schaye,
Matthieu Schaller,
John C. Helly
Abstract:
We use the FLAMINGO galaxy formation model to quantify the impact of baryon-CDM isocurvature perturbations on galaxy formation in $Λ$CDM. In linear theory, these perturbations represent local, compensated variations in the ratio between the baryon and CDM densities; they freeze in amplitude at late times, with an RMS amplitude of $1.5\%$ on the Lagrangian scale of a $10^{11}\,\rm M_\odot$ halo (…
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We use the FLAMINGO galaxy formation model to quantify the impact of baryon-CDM isocurvature perturbations on galaxy formation in $Λ$CDM. In linear theory, these perturbations represent local, compensated variations in the ratio between the baryon and CDM densities; they freeze in amplitude at late times, with an RMS amplitude of $1.5\%$ on the Lagrangian scale of a $10^{11}\,\rm M_\odot$ halo ($0.85\, \rm{Mpc}$). Although such perturbations arise naturally within $Λ$CDM, most cosmological simulations and semi-analytic models to date omit them. These perturbations are strongly anti-correlated with the matter overdensity field such that halos form with baryon fractions below the cosmic mean, with earlier-collapsing halos exhibiting stronger baryonic suppression. To isolate the galaxy response, we analyse three hydrodynamical simulations with identical initial matter overdensity fields that: i) include isocurvature modes, ii) omit them, or iii) invert their amplitude. At $z=8$, isocurvature perturbations reduce the mean baryon fraction and star formation rates of resolved halos by $ 5\%$ and $ 12\%$, respectively, relative to the null-isocurvature case. These effects are almost independent of halo mass and diminish steadily with time, reaching $ 0.1\%$ and $ 1\%$ by $z=0$. We develop a model based on spherical collapse that accurately reproduces the mean baryon fraction suppression. As high-redshift observations become increasingly routine, incorporating isocurvature perturbations into simulations and semi-analytic models will be important for robust predictions of early galaxy and black hole formation in the JWST era.
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Submitted 1 May, 2026; v1 submitted 1 December, 2025;
originally announced December 2025.