Blue monsters at z > 10: Where all their dust has gone

¹ Scuola Normale Superiore, Piazza dei Cavalieri 7, 56126 Pisa, Italy
² Center for Computational Astrophysics, Flatiron Institute, 162 5th Avenue, New York, NY 10010, USA

^⋆ Corresponding author; andrea.ferrara@sns.it

Received: 22 October 2024
Accepted: 7 January 2025

Abstract

The properties of luminous, blue, super-early galaxies (a.k.a. blue monsters) at redshift z > 10 have been successfully explained by the attenuation-free model (AFM), in which dust is pushed to kiloparsec scales by radiation-driven outflows. As an alternative to AFM, here we assess whether “attenuation-free” conditions can be replaced by a “dust-free” scenario in which dust is produced in very limited amounts and/or later destroyed in the interstellar medium. To this aim, we compare the predicted values of the dust-to-stellar mass ratio, ξ_d, with those measured in 15 galaxies at z > 10 from James Webb Space Telescope (JWST) spectra, when outflows are not included. Our model constrains ξ_d as a function of several parameters by allowing wide variations in the initial mass function (IMF), dust and metal production, and dust destruction for a set of supernova (SN) progenitor models and explosion energies. We find that log ξ_d ≈ −2.2 for all systems, which is indicative of the dominant role of SN dust production over destruction in these early galaxies. Such a value is strikingly different from the data, which instead indicates log ξ_d ≲ −4. We conclude that dust destruction alone can hardly explain the transparency of blue monsters. Other mechanisms, such as outflows, might be required.