Dust at cosmic dawn: unveiling the onset of dust and obscured star formation at z 8

summary

The gist

The gist Dust at cosmic dawn ALMA2040 reveals how next-generation submillimeter interferometry will unveil the onset of dust and obscured star formation at high redshifts by providing unprecedented

In short

ALMA2040 is a next-generation submillimeter interferometer designed to detect dust emission from galaxies at high redshifts ($z > 8$) with unprecedented sensitivity. This will allow researchers to measure dust masses, temperatures, and infrared luminosities simultaneously. This capability is crucial for understanding how dust and obscured star formation began in the earliest galaxies.

Key concepts

Dust at cosmic dawn: This refers to the epoch of very early galaxy formation, specifically at redshifts greater than 8 ($z > 8$). Dust plays a vital role in this era by obscuring star formation and altering how these distant galaxies look across different wavelengths. Understanding its presence helps reveal the hidden history of early cosmic evolution.
Grain growth: This is a process where dust particles grow larger within the interstellar medium of a galaxy. In local galaxies, this is thought to be a major way dust accumulates. At high redshifts ($z > 8$), this process is expected to be limited by factors like timescale and low metallicity, making it an important factor in determining how much dust forms early on.
Dust-to-stellar mass ratio (Md/M⋆): This ratio compares the total mass of dust in a galaxy to its stellar mass. Current observations suggest this ratio is relatively low ($10^{-3}$ to $10^{-2}$). Constraining this value at high redshift is key because it helps scientists distinguish between dust produced by supernovae and dust produced by grain growth in the early Universe.

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This episode discusses

The paper

Dust at cosmic dawn: unveiling the onset of dust and obscured star formation at z 8 · Read on arXiv

Hiddo Algera, Tom Bakx, Manuel Aravena, Leindert Boogaard, Karina Caputi, Stefano Carniani, Pierre Cox, Elisabete da Cunha, Miroslava Dessauges-Zavadsky, Ènio Diaz Santos, Ándreas Faisst, Andrea Ferrara, ×inobu Fudamoto, Carlotta Gruppioni, Mahmoud Hamed, Jacqueline Hodge, Ryota Ikeda, Hanae Inami, Adarsh Kumar, Ándrea Lapi, иizhong Liu, оmberto Maio→, Dieu Nguyen→, Omima Osman→, Andrea Pallottini, Gergo Popping ×5, Francesco Salvestrini, Irene Shivaei, Laura Sommovigo, иis Witstok×ok31, Mengyuan Xiao

Lorentz Center and NOVA · Department of Physics and Astronomy Chalmers University of Technology · Instituto de Estudios Astrofíicos Facultad de Ingeniería y Ciencias Universidad Diego Portales · Leiden Observatory Leiden University · Kapteyn Astronomical Institute University of Groningen · Scuola Normale Superiore Pisa Scuola Normale Superiore Pisa Scuola Normale Superiore Pisa Sorbonne Universite Paris and CNRS Institut d’Astrophysique de Paris International Centre for Radio Astronomy Research The University of Western Australia Department of Astronomy University of Geneva Foundation for Research and Technology--Hellas Institute of Fundamental Physics of the Universe Department of Astronomy University Michigan Physics and Astronomy and George P. and Cynthia Woods Mitchell Institute for Fundamental Physics and Astronomy

Although less than 1 percent of the baryonic mass budget of a galaxy, cosmic dust profoundly alters the multi-wavelength appearance of galaxies across cosmic time. The (sub)millimeter wavelength regime is uniquely capable of weighing these dust reservoirs, and revealing the total extent of galaxy evolution that remains hidden behind them. With current facilities, however, doing so at z > 8 is largely out of reach. ALMA2040, a next-generation (sub)millimeter interferometer, is set to change this. Through an order-of-magnitude increase in sensitivity compared to ALMA, ALMA2040 is a transformational facility that will be able to routinely detect dust emission from galaxies at z > 8 and, through simultaneous multi-band characterization, accurately measure their dust masses, temperatures, and infrared luminosities. Combined with ancillary metallicity measurements -- including from the far-infrared lines detected by ALMA2040 itself -- this will establish the relative roles of supernovae and grain growth in building up dust in the earliest galaxies. Simultaneously, ALMA2040 will measure the fraction of star formation that is obscured by dust at cosmic dawn, and thereby the extent to which rest-UV and optical surveys miss early galaxy build-up. Without a 10 times upgrade to ALMA -- comparable to the leap from the VLT to the ELT -- we will not be able to capitalize on the momentous advances enabled by JWST, and will remain blind to the cold and obscured component of galaxy formation in the z > 8 Universe.

Transcript

Introduction to the show: ident: Astrophysics Radio. Generated commentary on the latest astrophysics papers.

Vera: I'm Vera.

Jocelyn: And I'm Jocelyn, here with Subrahmanyan.

Vera: We're looking at the paper: "Dust at cosmic dawn".

Jocelyn: The gist Dust at cosmic dawn ALMA2040 reveals how next-generation submillimeter interferometry will unveil the onset of dust and obscured star formation at high redshifts by providing unprecedented sensitivity and…

Vera: First, who's behind it and why it matters.

Paper summary: Subrahmanyan: Thinking about what this paper means for the bigger cosmic picture, it really frames the problem as understanding the total extent of galaxy evolution that remains hidden behind this dust.

Vera: And it points directly at ALMA2040 as a facility needed to tackle these questions because it offers an order-of-magnitude increase in sensitivity compared to current ALMA observations.

Jocelyn: So the paper emphasizes that with ALMA2040, we will be able to routinely detect dust emission from galaxies at z greater than eight and measure their dust masses, temperatures, and infrared luminosities simultaneously <ref:2610.21460#pg1>.

Subrahmanyan: And combining those submillimeter measurements with ancillary metallicity measurements—including the far-infrared lines that ALMA2040 itself can detect—this will help us establish the relative roles of supernovae and grain growth in building up dust in the earliest galaxies.

Vera: Plus, ALMA2040 will measure what fraction of star formation is obscured by dust at cosmic dawn, which shows us how much rest-UV and optical surveys are missing when they try to map early galaxy build-up.

Jocelyn: So the conclusion is that without a tenfold upgrade to ALMA, comparable to the jump from the VLT to the ELT, we won't be able to take advantage of what JWST has enabled in terms of seeing these cold and obscured components of galaxy formation in the z greater than eight Universe <ref:2610.21460#pg1>.

Conclusion: Vera: So, this paper, "Dust at cosmic dawn," is basically about using new submillimeter data to see what's happening with dust and hidden star formation when the universe was really young, around eight billion years after the Big Bang.

Jocelyn: Right. They’re looking at galaxies at redshift z greater than eight. The main authors are talking about how this reveals the earliest stages of galaxy building up that we just can't see with current telescopes like rest-UV surveys.

Subrahmanyan: From a theoretical side, they’re asking fundamental questions—when and how did this dust actually start forming in these early galaxies? It connects to whether supernovae or grain growth is doing the heavy lifting early on.

Vera: Exactly. They're trying to figure out the nature of that early dust and where it lives inside those first structures. The core idea is that this dusty component is a huge piece of the puzzle for how galaxies evolved in the first billion years.

Jocelyn: And what they are measuring isn't just there, it’s quantifying what fraction of star formation we’re missing when we only look at brighter, less obscured light. It tells us how much the picture has to change before we can accurately map early galaxy growth using optical surveys.

Subrahmanyan: That really pushes us to think about the full spectrum of galaxy assembly. If a lot of star formation is hidden in dust, then our models of how structure forms need to account for that massive reservoir. We need more observations, maybe even deeper ones than we currently have, to nail down these early constraints.

Vera: It’s definitely a big picture thing. The paper points out that without this kind of sensitivity increase—like the ALMA2040 facility is aiming for—we are still blind to this cold, obscured part of galaxy formation in the z greater than eight Universe.

Jocelyn: So, they're showing us what’s possible with next-generation submillimeter work. And that leads us right into the specific details of how they measure these dust masses and what those numbers actually constrain.

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