The ALMA REBELS sur v ey: obscured star formation in massi v e Lyman-break galaxies at z = 4-8 revealed by the IRX-βand M*relations

R. A.A. Bowler, H. Inami, L. Sommovigo, R. Smit, H. S.B. Algera, M. Aravena, L. Barrufet, R. Bouwens, E. da Cunha, F. Cullen, P. Dayal, I. De Looze, J. S. Dunlop, Y. Fudamoto, V. Mauerhofer, R. J. McLure, M. Stefanon, R. Schneider, A. Ferrara, L. GrazianiJ. A. Hodge, T. Nanayakkara, M. Palla, S. Schouws, D. P. Stark, P. P. van der Werf

Research output: Contribution to journalArticlepeer-review

2 Citations (Scopus)


We investigate the degree of dust obscured star formation in 49 massive (log 10 ( M*/M ⊙) > 9) Lyman-break galaxies (LBGs) at z = 6.5-8 observed as part of the Atacama Large Millimeter/submillimeter Array (ALMA) Reionization Era Bright Emission Line Surv e y (REBELS) large program. By creating deep stacks of the photometric data and the REBELS ALMA measurements we determine the average rest-frame ultraviolet (UV), optical, and far-infrared (FIR) properties which reveal a significant fraction ( f obs = 0.4-0.7) of obscured star formation, consistent with previous studies. From measurements of the rest-frame UV slope, we find that the brightest LBGs at these redshifts show bluer ( β≃ -2.2) colours than expected from an extrapolation of the colour-magnitude relation found at fainter magnitudes. Assuming a modified blackbody spectral energy distribution (SED) in the FIR (with dust temperature of T d = 46 K and βd = 2.0), we find that the REBELS sources are in agreement with the local 'Calzetti-like' starburst Infrared-excess (IRX)-βrelation. By re-analysing the data available for 108 galaxies at z ≃ 4-6 from the ALMA Large Program to Investigate C + at Early Times (ALPINE) using a consistent methodology and assumed FIR SED, we show that from z ≃ 4-8, massive galaxies selected in the rest-frame UV have no appreciable evolution in their derived IRX-βrelation. When comparing the IRX-M*relation derived from the combined ALPINE and REBELS sample to relations established at z < 4, we find a deficit in the IRX, indicating that at z > 4 the proportion of obscured star formation is lower by a factor of ≳3 at a given a M*. Our IRX-βresults are in good agreement with the high-redshift predictions of simulations and semi-analytic models for z ≃ 7 galaxies with similar stellar masses and star formation rates.

Original languageEnglish
Pages (from-to)5808-5828
Number of pages21
JournalMonthly Notices of the Royal Astronomical Society
Issue number3
Early online date4 Dec 2023
Publication statusPublished - 1 Jan 2024


Dive into the research topics of 'The ALMA REBELS sur v ey: obscured star formation in massi v e Lyman-break galaxies at z = 4-8 revealed by the IRX-βand M*relations'. Together they form a unique fingerprint.

Cite this