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![Estimated properties of REBELS-29-2 and REBELS-12-2
a, Star-formation rate as a function of stellar mass for z>5.5\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$z > 5.5$$\end{document} galaxies. Background contours show the distribution of faint LBGs at z = 6–8. The dashed line and shaded region indicates the star-forming main-sequence as measured up to z ≈ 4 and extrapolated to z = 7 (ref. ¹⁹). Cyan squares represent previously identified dusty star-forming galaxies (DSFGs) at z ≈ 5.7–6.9. Purple squares show dusty galaxies found as companions of z ≈ 6.1–6.5 quasars, which also remained undetected in rest-UV observations. Their mass limits are estimated from dynamical masses13,14. Error bars correspond to 1σ uncertainties. The UV-bright galaxies (REBELS-12 and REBELS-29), and the serendipitous, dusty galaxies (REBELS-12-2 and REBELS-29-2) are shown as blue and red stars (using SFRIR). The SFRs and stellar mass limits of the newly identified galaxies are lower than the majority of z > 5.5 DSFGs and quasar companions at these redshifts. b, c, Photometric constraints and SEDs of REBELS-29-2 and REBELS-12-2, respectively. 2σ upper limits are shown for non-detections (grey arrows). Red and blue solid lines show the median posterior SEDs together with their 68% confidence contours. For comparison, SEDs of dusty star-bursting galaxies normalized at the ALMA continuum fluxes are indicated in solid green (the average SED of ALESS galaxies²⁰), dashed brown (HFLS03⁸), and dashed purple lines (HDF850.1)²¹. The newly found dusty sources as companions of normal star-forming galaxies suggest that dusty, lower-luminosity versions of DSFGs exist at z = 6–8 in larger number than previously assumed.](profile/Luca-Graziani/publication/354777045/figure/fig6/AS:1071071432294404@1632374737694/Estimated-properties-of-REBELS-29-2-and-REBELS-12-2-a-Star-formation-rate-as-a-function.png)
Estimated properties of REBELS-29-2 and REBELS-12-2 a, Star-formation rate as a function of stellar mass for z>5.5\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$z > 5.5$$\end{document} galaxies. Background contours show the distribution of faint LBGs at z = 6–8. The dashed line and shaded region indicates the star-forming main-sequence as measured up to z ≈ 4 and extrapolated to z = 7 (ref. ¹⁹). Cyan squares represent previously identified dusty star-forming galaxies (DSFGs) at z ≈ 5.7–6.9. Purple squares show dusty galaxies found as companions of z ≈ 6.1–6.5 quasars, which also remained undetected in rest-UV observations. Their mass limits are estimated from dynamical masses13,14. Error bars correspond to 1σ uncertainties. The UV-bright galaxies (REBELS-12 and REBELS-29), and the serendipitous, dusty galaxies (REBELS-12-2 and REBELS-29-2) are shown as blue and red stars (using SFRIR). The SFRs and stellar mass limits of the newly identified galaxies are lower than the majority of z > 5.5 DSFGs and quasar companions at these redshifts. b, c, Photometric constraints and SEDs of REBELS-29-2 and REBELS-12-2, respectively. 2σ upper limits are shown for non-detections (grey arrows). Red and blue solid lines show the median posterior SEDs together with their 68% confidence contours. For comparison, SEDs of dusty star-bursting galaxies normalized at the ALMA continuum fluxes are indicated in solid green (the average SED of ALESS galaxies²⁰), dashed brown (HFLS03⁸), and dashed purple lines (HDF850.1)²¹. The newly found dusty sources as companions of normal star-forming galaxies suggest that dusty, lower-luminosity versions of DSFGs exist at z = 6–8 in larger number than previously assumed.
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Over the past decades, rest-frame ultraviolet (UV) observations have provided large samples of UV luminous galaxies at redshift (z) greater than 6 (refs. 1–3), during the so-called epoch of reionization. While a few of these UV-identified galaxies revealed substantial dust reservoirs4–7, very heavily dust-obscured sources at these early times have...
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![Figure 1: [CII] 158 µm line and dust emission detections. a: REBELS-29...](profile/Riley-Endsley/publication/354777663/figure/fig1/AS:1071139107377155@1632390872977/CII-158-m-line-and-dust-emission-detections-a-REBELS-29-field-at-z-668-b_Q320.jpg)
Over the past decades, rest-frame ultraviolet (UV) observations have provided large samples of UV luminous galaxies at redshift (z) greater than 6, during the so-called epoch of reionization. While a few of these UV identified galaxies revealed significant dust reservoirs, very heavily dust-obscured sources at these early times have remained elusiv...
Citations
... This population includes but is not limited to the following samples: sub-millimetre galaxies (SMGs) (e.g., Walter et al. 2012), H-band dropouts (e.g., Wang et al. 2019;Alcalde Pampliega et al. 2019;Smail et al. 2023), Ks-faint (e.g., Smail et al. 2021), Hubble Space Telescope (HST)-dark/faint galaxies (e.g., Franco et al. 2018;Pérez-González et al. 2023;Xiao et al. 2023;Gómez-Guijarro et al. 2023), and radio-selected near infrared (NIR) dark galaxies (Algera et al. 2020;Talia et al. 2021;Enia et al. 2022;van der Vlugt et al. 2023;Gentile et al. 2024a,b). Recent studies revealed that this population contributes significantly (10 − 40%) to the cosmic star formation rate density in the early universe (z ∼ 3 − 6, Wang et al. 2019;Fudamoto et al. 2021;Talia et al. 2021;Enia et al. 2022;Shu et al. 2022;Xiao et al. 2023), and dominates the massive end of the stellar mass function (SMF) at z ∼ 3 − 8 (Wang et al. 2019;Gottumukkala et al. 2024). This indicates that this population plays a significant role in cosmic star formation history, even up to 50% estimated from Lyman break galaxy selected samples at z ∼ 3 (Enia et al. 2022), but has been largely missed by previous optical/NIR surveys. ...
Optically dark dusty star-forming galaxies (DSFGs) play an essential role in massive galaxy formation at early cosmic time, however their nature remains elusive. Here we present a detailed case study of all the baryonic components of a z=4.821 DSFG, XS55. Selected from the ultra-deep COSMOS-XS 3GHz map with a red SCUBA-2 450m/850m colour, XS55 was followed up with ALMA 3mm line scans and spectroscopically confirmed to be at z=4.821 via detections of the CO(5-4) and [CI](1-0) lines. JWST/NIRCam imaging reveals that XS55 is a F150W-dropout with red F277W/F444W colour, and a complex morphology: a compact central component embedded in an extended structure with a likely companion. XS55 is tentatively detected in X-rays with both Chandra and XMM-Newton, suggesting an active galactic nucleus (AGN) nature. By fitting a panchromatic SED spanning NIR to radio wavelengths, we revealed that XS55 is a massive main-sequence galaxy with a stellar mass of and a star formation rate of . The dust of XS55 is optically thick in the far infrared (FIR) with a surprisingly cold dust temperature of , making XS55 one of the coldest DSFGs at known to date. This work unveils the nature of a radio-selected F150W-dropout, suggesting the existence of a population of DSFGs hosting active black holes embedded in optically thick dust.
... Therefore, it is usually very challenging to differentiate true DSFGs at z > 4 from lower-redshift "interlopers" with large z phot error (e.g., see the recent dispute of COSBO-7 at z phot > 7 but spectroscopic redshift z spec = 2.625; Ling et al. 2024, Jin et al. 2024a). Many of these DSFGs at z phot ≳ 4 are totally dustobscured at HST wavelengths, and therefore also known as "HST-dark", "NIR-dark", "H-dropout" or "H-faint" galaxies (e.g., Huang et al. 2011;da Cunha et al. 2015;Simpson et al. 2015;Fujimoto et al. 2016;Franco et al. 2018;Alcalde Pampliega et al. 2019;Wang et al. 2019b;Yamaguchi et al. 2019;Sun et al. 2021;Talia et al. 2021;Enia et al. 2022;Gómez-Guijarro et al. 2022;Kokorev et al. 2022;Manning et al. 2022;Xiao et al. 2023b;Tsujita et al. 2024), including certain amount of galaxies that are only detected with ALMA (e.g., Decarli et al. 2017;Mazzucchelli et al. 2019;Venemans et al. 2019;Williams et al. 2019;Fudamoto et al. 2021;Wang et al. 2023). Therefore, it is very challenging to obtain secure redshifts of these galaxies through groundbased optical/near-IR spectroscopy. ...
We present a stringent measurement of the dust-obscured star-formation rate density (SFRD) at from the ASPIRE JWST Cycle-1 medium and ALMA Cycle-9 large program. We obtained JWST/NIRCam grism spectroscopy and ALMA 1.2-mm continuum map along 25 independent quasar sightlines, covering a total survey area of 35 arcmin where we search for dusty star-forming galaxies (DSFGs) at . We identify eight DSFGs in seven fields at through the detection of H or [O III] 5008 lines, including fainter lines such as H, [O III] 4960, [N II] 6585, [S II] 6718,6733 for six sources. With this spectroscopically complete DSFG sample at and negligible impact from cosmic variance (shot noise), we measure the infrared luminosity function (IRLF) down to . We find flattening of IRLF at towards the faint end (power-law slope ). We determine the dust-obscured cosmic SFRD at this epoch as . This is significantly higher than previous determination using ALMA data in the Hubble Ultra Deep Field, which is void of DSFGs at because of strong cosmic variance (shot noise). We conclude that the majority (%) of cosmic star formation at is still obscured by dust. We also discuss the uncertainty of SFRD propagated from far-IR spectral energy distribution and IRLF at the bright end, which will need to be resolved with future ALMA and JWST observations.
... Global star formation rate density at each simulation timestep in our simulated boxes as a function of redshift. Line styles are the same as those in Fig. 5. Observationally inferred data comes from several different methods (Robertson & Ellis 2012;Fudamoto et al. 2021;Gruppioni et al. 2020;Cochrane et al. 2023;Algera et al. 2023). Higher energy loadings can lead to much more suppression in star formation. ...
... Fudamoto et al. (2021) Cochrane et al.(2023) ...
We deploy the new Arkenstone galactic wind model in cosmological simulations for the first time, allowing us to robustly resolve the evolution and impact of high specific energy winds. In a (25Mpc) box we perform a set of numerical experiments that systematically vary the mass and energy loadings of such winds, finding that their energy content is the key parameter controlling the stellar to dark matter mass ratio. Increasing the mass loading, at fixed energy, actually results in mildly enhanced star formation, counter to prevailing wisdom but in agreement with recent analytic models. Of the simple parametrisations that we test, we find that an energy loading that scales inversely with halo mass best matches a wide range of observations, and can do so with mass loadings drastically lower than those in most previous cosmological simulations. In this scenario, much less material is ejected from the interstellar medium. Instead, winds both heat gas in the circumgalactic medium, slowing infall onto the galaxy, and also drive shocks beyond the virial radius, preventing accretion onto the halo in the first place. We have not yet tied the mass and energy loadings to high-resolution simulations (a key goal of the Learning the Universe collaboration); however, we can already report that a much lower fraction of the available supernova energy is needed in preventative galaxy regulation than required by ejective wind feedback models such as IllustrisTNG.
... 3. The emergence of dusty galaxies: The fraction of star formation missed due to dust at z > 4 and at low luminosities remains unclear. ALMA has discovered dusty galaxies with relatively low masses and star formation rates already at z > 5 (e.g., Wang et al. 2019;Williams et al. 2019;Yamaguchi et al. 2019;Fudamoto et al. 2021;Dayal et al. 2022;Algera et al. 2023), suggesting that dust-obscured star formation may be more prominent than was expected. These highly obscured extreme starbursts known to exist may represent only the tip of the iceberg. ...
In this paper we describe the survey design for the Ultradeep NIRSpec and NIRCam Observations before the Epoch of Reionization (UNCOVER) Cycle 1 JWST Treasury program, which executed its early imaging component in 2022 November. The UNCOVER survey includes ultradeep (∼29–30AB) imaging of ∼45 arcmin ² on and around the well-studied A2744 galaxy cluster at z = 0.308 and will follow up ∼500 galaxies with extremely deep low-resolution spectroscopy with the NIRSpec/PRISM during the summer of 2023, with repeat visits in summer 2024. We describe the science goals, survey design, target selection, and planned data releases. We also present and characterize the depths of the first NIRCam imaging mosaic, highlighting previously unparalleled resolved and ultradeep 2–4 μ m imaging of known objects in the field. The UNCOVER primary NIRCam mosaic spans 28.8 arcmin ² in seven filters (F115W, F150W, F200W, F277W, F356W, F410M, and F444W) and 16.8 arcmin ² in our NIRISS parallel (F115W, F150W, F200W, F356W, and F444W). To maximize early community use of the Treasury data set, we publicly release the full reduced mosaics of public JWST imaging including 45 arcmin ² NIRCam and 17 arcmin ² NIRISS mosaics on and around the A2744 cluster, including the Hubble Frontier Field primary and parallel footprints.
... Despite the short cosmic time available for dust production at high-redshift, early galaxies host surprisingly abundant dust (Fudamoto et al. 2021;Schouws et al. 2022;Xiao et al. 2023;McKinney et al. 2023;Akins et al. 2023). This explains why even the deepest HST+Spitzer campaigns missed these "dark" galaxies, but brings new questions to the forefront. ...
We present the PANORAMIC survey, a pure parallel extragalactic imaging program with NIRCam observed during JWST Cycle 1. The survey obtained 530 sq arcmin of NIRCam imaging from 1-5m, totaling 192 hours of science integration time. This represents the largest on-sky time investment of any Cycle 1 GO extragalactic NIRCam imaging program by nearly a factor of 2. The survey includes 432 sq arcmin of novel sky area not yet observed with JWST using at least 6 NIRCam broad-band filters, increasing the existing area covered by similar Cycle 1 data by 60%. 70 square arcmin was also covered by a 7th filter (F410M). A fraction of PANORAMIC data (200 sq arcmin) was obtained in or around extragalactic deep-fields, enhancing their legacy value. Pure parallel observing naturally creates a wedding cake survey with both wide and ultra-deep tiers, with 5 point source depths at F444W ranging from 27.8-29.4 (ABmag), and with minimized cosmic variance. The 6+ filter observing setup yields remarkably good photometric redshift performance, achieving similar median scatter and outlier fraction as CANDELS (; ), which enables a wealth of science across redshift without the need for followup or ancillary data. We overview the proposed survey, the data obtained as part of this program, and document the science-ready data products in the first data release. PANORAMIC has delivered wide-area and deep imaging with excellent photometric performance, demonstrating that pure parallel observations with JWST are a highly efficient observing mode that is key to acquiring a complete picture of galaxy evolution from rare bright galaxies to fainter, more abundant sources at all redshifts.
... Clearly, SNe (and later on growth in the ISM) do produce tangible amounts of dust, as less than 500 Myr later, at z ≈ 7, dust appears widespread (Inami et al. 2022;Schouws et al. 2023;Witstok et al. 2023a;Algera et al. 2023) -both puzzlingly high dust-to-stellar mass ratios (M d /M ⋆ ∼ 0.01; Algera et al. 2024) and fully dust-obscured sources (Fudamoto et al. 2021) are observed at this epoch. In addition, features of the at-tenuation curve associated with the carbonaceous dust grains produced by SNe are observed at z ∼ 6.7 (Witstok et al. 2023b). ...
We report the first successful ALMA follow-up observations of a secure JWST-selected galaxy, by robustly detecting () the [OIII] line in JADES-GS-z14-0 (hereafter GS-z14). The ALMA detection yields a spectroscopic redshift of , and increases the precision on the prior redshift measurement of from NIRSpec by 180. Moreover, the redshift is consistent with that previously determined from a tentative detection () of CIII] (), solidifying the redshift determination via multiple line detections. We measure a line luminosity of , placing GS-z14 at the lower end, but within the scatter of, the local -star formation rate relation. No dust continuum from GS-z14 is detected, suggesting an upper limit on the dust-to-stellar mass ratio of , consistent with dust production from supernovae with a yield . Combining a previous JWST/MIRI photometric measurement of the [OIII]4959,5007 and H lines with Cloudy models, we find GS-z14 to be surprisingly metal-enriched () a mere after the Big Bang. The detection of a bright oxygen line in GS-z14 thus reinforces the notion that galaxies in the early Universe undergo rapid evolution.
... High-redshift individual galaxy detections such as Fudamoto et al. (2021) have detected early-time, dusty, SF galaxies. Fudamoto et al. (2021) estimate that obscured star formation at z > 6 could be contributing between 10% and 25% to the total density. ...
... High-redshift individual galaxy detections such as Fudamoto et al. (2021) have detected early-time, dusty, SF galaxies. Fudamoto et al. (2021) estimate that obscured star formation at z > 6 could be contributing between 10% and 25% to the total density. However, Gruppioni et al. (2020) in the ALMA ALPINE survey identify higher fractions of obscured star formation using a larger sample of ∼50 detected IR sources. ...
We explore the cosmic evolution of the fraction of dust-obscured star formation predicted by the simba cosmological hydrodynamic simulations featuring an on-the-fly model for dust formation, evolution, and destruction. We find that up to z = 3, our results are broadly consistent with previous observational results of little to no evolution in obscured star formation. However, at z > 3 we find strong evolution at fixed galaxy stellar mass toward greater amounts of obscured star formation, in tension with high-redshift observations. We explain the trend of increasing obscuration at higher redshifts by evolving star-dust geometry, as the dust-to-stellar mass ratios remain relatively constant across cosmic time. We additionally see that at a fixed redshift, more massive galaxies have a higher fraction of their star formation obscured, which is explained by increased dust-to-stellar mass ratios at higher stellar masses. Finally, we estimate the contribution of dust-obscured star formation to the total star formation rate budget and find that the dust-obscured star formation history peaks around z ∼ 2−3, and becomes subdominant at z ≳ 5. The dominance of obscured star formation at redshifts z ≲ 4 is consistent with our results for the evolution of the obscured star formation fraction at fixed stellar mass to higher values at higher redshift because there exist fewer massive, heavily obscured galaxies at high redshift.
... Decarli et al. (2017) and Venemans et al. (2020) have shown that quasars are especially good places to look for bright star-forming companions, with ∼50% of the quasars they examined showing at least one companion galaxy (see also Meyer et al. 2022). Massive galaxies ( * ≳ 10 8.5 M ⊙ ) at high redshifts are also excellent targets to use for efficient searches for companion galaxies (Loiacono et al. 2021;Fudamoto et al. 2021). To date about 40 companion galaxies have been discovered at ≳ 4 with ALMA observations (e.g., Decarli et al. 2017;Trakhtenbrot et al. 2017;Miller et al. 2020;Venemans et al. 2020;Loiacono et al. 2021;Fudamoto et al. 2021). ...
... Massive galaxies ( * ≳ 10 8.5 M ⊙ ) at high redshifts are also excellent targets to use for efficient searches for companion galaxies (Loiacono et al. 2021;Fudamoto et al. 2021). To date about 40 companion galaxies have been discovered at ≳ 4 with ALMA observations (e.g., Decarli et al. 2017;Trakhtenbrot et al. 2017;Miller et al. 2020;Venemans et al. 2020;Loiacono et al. 2021;Fudamoto et al. 2021). ...
... We make use of the [CII]-emitting companion galaxies identified around 75 [CII]-emitting galaxies from the ALPINE large program (Le Fèvre et al. 2020;Béthermin et al. 2020) at = 4-6, 25 [CII]-emitting galaxies from the REBELS large program (Bouwens et al. 2022b) at = 6.5-7.7, and 27 [CII]-emitting QSOs from Venemans et al. (2020) at = 6.0-7.6. Loiacono et al. (2021) report 12 [CII]-emitter candidates around UV-selected = 4-6 galaxies in the ALPINE survey, and Fudamoto et al. (2021) report 2 [CII]-emitting galaxies around UV-selected sources in REBELS. Around the 27 [CII]-emitting QSOs studied by Venemans et al. (2020), 27 line-emitting galaxies are identified, but only 20 of these appear to lie at frequencies <2000 km/s from the target [CII]-emitting source and thus are likely at ∼ 6-7. ...
We present a new method to determine the star formation rate (SFR) density of the Universe at that includes the contribution of dust-obscured star formation. For this purpose, we use a [CII] (158 m) selected sample of galaxies serendipitously identified in the fields of known objects to characterize the fraction of obscured SFR. The advantage of a [CII] selection is that our sample is SFR-selected, in contrast to a UV-selection that would be biased towards unobscured star formation. We obtain a sample of 23 [CII] emitters near star-forming (SF) galaxies and QSOs -- three of which we identify for the first time -- using previous literature and archival ALMA data. 18 of these serendipitously identified galaxies have sufficiently deep rest-UV data and are used to characterize the obscured fraction of the star formation in galaxies with SFRs . We find that [CII] emitters identified around SF galaxies have 63\% of their SFR obscured, while [CII] emitters around QSOs have 93\% of their SFR obscured. By forward modeling existing wide-area UV luminosity function (LF) determinations, we derive the intrinsic UV LF using our characterization of the obscured SFR. Integrating the intrinsic LF to = 20 we find that the obscured SFRD contributes to and of the total SFRD at and based on our sample of companions galaxies near SFGs and QSOs, respectively. Our results suggest that dust obscuration is not negligible at , further underlining the importance of far-IR observations of the Universe.
... Previous observations of the FIR emis-sion in high-redshift galaxies has shown that the stellar mass range of log 10 ( ★ /M ⊙ )= 9-10 is key for understanding the build-up of dust at early times. As shown in samples of galaxies observed through various ALMA large programs, within this mass range the obscured SFR fraction of = 4-8 galaxies is ≃ 0.5 (Fudamoto et al. 2020b;Algera et al. 2023;Mitsuhashi et al. 2024;Bowler et al. 2024), with some sources showing obs > 0.9 (Fudamoto et al. 2021). ...
We present a spatially resolved analysis of four star-forming galaxies at using data from the JWST PRIMER and ALMA-CRISTAL surveys to probe the stellar and inter-stellar medium properties on the sub-kpc scale. In the JWST NIRCam imaging we find that the galaxies are composed of multiple clumps (between 2 and ) separated by , with comparable morphologies and sizes in the rest-frame UV and optical. Using BAGPIPES to perform pixel-by-pixel SED fitting to the JWST data we show that the SFR () and stellar mass () derived from the resolved analysis are in close () agreement with those obtained by fitting the integrated photometry. In contrast to studies of lower-mass sources, we thus find a reduced impact of outshining of the older (more massive) stellar populations in these normal galaxies. Our JWST analysis recovers bluer rest-frame UV slopes () and younger ages () than archival values. We find that the dust continuum from ALMA-CRISTAL seen in two of these galaxies correlates, as expected, with regions of redder rest-frame UV slopes and the SED-derived , as well as the peak in the stellar mass map. We compute the resolved IRX- relation, showing that the IRX is consistent with the local starburst attenuation curve and further demonstrating the presence of an inhomogeneous dust distribution within the galaxies. A comparison of the CRISTAL sources to those from the FirstLight zoom-in simulation of galaxies with the same and SFR reveals similar age and colour gradients, suggesting that major mergers may be important in the formation of clumpy galaxies at this epoch.
... Hopkins & Beacom 2006, Madau & Dickinson 2014, now extending to the highest redshifts ( > 6; e.g. Kistler et al. 2009, Robertson & Ellis 2012, Fudamoto et al. 2021, Zavala et al. 2021, Bouwens et al. 2022, Barrufet et al. 2023, Algera et al. 2023, and in identifying large samples of AGN (e.g. Mazzucchelli et al. 2017, Farina et al. 2022, including some of the first supermassive black holes in the Universe (Bañados et al. 2018, Yang et al. 2020, Wang et al. 2021). ...
We present an analysis of 152,355 radio sources identified in the second data release of the LOFAR Two Metre Sky Survey (LoTSS-DR2) with Sloan Digital Sky Survey (SDSS) spectroscopic redshifts in the range 0.00 < z < 0.57. Using Monte Carlo simulations we determine the reliability of each source exhibiting an excess in radio luminosity relative to that predicted from their Ha emission, and, for a subset of 124,023 sources we combine this measurement with a full BPT analysis. Using these two independent diagnostics we determine the reliability of each source hosting a supermassive black hole of high or low Eddington-scaled accretion rate, and combine the measurements to determine the reliability of sources belonging to each of four physical classes of objects: star forming galaxies (SFGs), radio-quiet active galactic nuclei (RQAGN), and high- or low-excitation radio galaxies (HERGs or emission-line LERGs). The result is a catalogue which enables user-defined samples of radio sources with a reliability threshold suited to their science goal e.g. prioritising purity or completeness. Here we select high-confidence samples of radio sources (>90% reliability) to report: 38,588 radio-excess AGN in the LoTSS DR2 sample (362 HERGs, and 12,648 emission-line LERGs), together with 38,729 SFGs, and 18,726 RQAGN. We validate these results through comparison to literature using independent emission-line measurements, and to widely-adopted WISE photometric selection techniques. While our use of SDSS spectroscopy limits our current analysis to ~4 percent of the LoTSS-DR2 catalogue, our method is directly applicable to data from the forthcoming WEAVE-LOFAR survey which will obtain over a million spectra of 144 MHz selected sources.
