Galaxy formation and evolution

Abstract:

We present the Parallel Application of Slitless Spectroscopy to Analyze Galaxy Evolution (PASSAGE) spectroscopic redshift catalog in the COSMOS field. PASSAGE is a JWST Cycle 1 Near Infrared Imager and Slitless Spectrograph (or NIRISS) wide-field slitless spectroscopy pure-parallel survey, obtaining near-infrared spectra of thousands of extragalactic sources. Fifteen out of 63 PASSAGE fields fall within the Hubble Space Telescope COSMOS footprint, of which 11 overlap with COSMOS-Web, a JWST treasury survey providing additional space-based photometry. We present our custom line-finding algorithm and visual inspection effort used to identify emission lines and derive the spectroscopic redshifts for line-emitting sources in PASSAGE. The line-finding algorithm identifies between ∼200 and 950 line-emitting candidates per field, of which typically 47% were identified as true emission lines post visual inspection. We identify 2183 emission-line sources at 0.08 ≲ z ≲ 4.7, 1896 of which have available COSMOS photometric redshifts. We find excellent redshift agreement between the COSMOS photometric redshifts and the PASSAGE spectroscopic redshifts for strong (signal-to-noise ratio > 5), multi-line-emitting sources. This agreement weakens for PASSAGE single-line emitters with ambiguous identities. These single-line emitters are likely misidentified around 18% of the time based on comparisons to photometric redshifts. We derive stellar masses using PASSAGE photometry and spectroscopic redshifts, in broad agreement with existing COSMOS-Web stellar masses, but with some discrepancy driven by redshift disagreements. We publicly release this spectroscopic redshift catalog, which will enable community-led science in prime extragalactic fields and serve as a crucial dataset for validating Euclid and Roman spectroscopy.

Abstract:

Context. High-redshift radio galaxies can provide important insights into structure formation and galaxy evolution during earlier cosmological epochs. TGSS J1530+1049 was selected as a candidate high-redshift radio galaxy based on its very steep radio spectrum. Subsequent observations with the James Webb Space Telescope ( JWST ) presented in a companion paper have shown that it is located at a redshift of z = 4.0. The JWST data furthermore showed that the radio source is part of one of the densest structures of galaxies and ionized gas known at these redshifts. The complex system qualitatively resembles a massive (cluster) galaxy that formed early through a rapid succession of mergers. Aims. TGSS J1530+1049 is an unresolved source down to an ∼0.6″ scale in multiple radio surveys. To reveal its high-resolution radio structure and allow for a detailed comparison with JWST observations, we studied its morphology at various angular scales with different radio interferometric instruments. Methods. We observed TGSS J1530+1049 at a milliarcsecond- (mas) scale angular resolution with the European VLBI Network (EVN), and at an ∼100-mas scale resolution with the enhanced Multi-Element Remotely Linked Interferometer Network (e-MERLIN). Results. We recovered a complex north–south oriented structure with steep-spectrum radio-emitting features, which are associated with the lobes and hot spots of a jetted active galactic nucleus. However, the centre of the radio galaxy proved to be too faint at centimetre wavelengths to be unambiguously detected in our observations. Nevertheless, its linear size (∼5.5 kpc) and radio power ( L 1.4 GHz ≈ 3 × 10 27 W Hz −1 ) place it among the so-called medium-sized symmetric objects, which are a smaller and/or confined version of larger radio galaxies. A comparison between its radio morphology and that of the ionized gas as observed with the NIRSpec integral field unit on JWST shows that the two are closely aligned. However, the optical emission line gas extends out to ∼25 kpc, which is well beyond the detected radio structures.

Abstract:

Aims. The origin of the morphological dichotomy between Fanaroff-Riley Class I (FRI) and Class II (FRII) radio galaxies has long been debated. In this study, we investigate whether the cluster-scale environment plays a significant role in shaping the morphology of FRIs and FRIIs. Methods. Using the new morphologically classified catalogue from the second data release of the LOFAR Two-metre Sky Survey (LoTSS DR2), we construct two samples at z  < 0.4: a volume-limited sample with L 144 > 4 × 10 24 W Hz −1 and a paired sample in which each FRII is matched to the nearest FRI in luminosity and redshift. We cross-match these samples with a recent galaxy cluster catalogue based on the DESI Legacy Imaging Survey. A galaxy is considered associated with a cluster with M 500  > 0.47 × 10 14   M ⊙ if the redshift difference between the galaxy and the cluster centre is below 0.01, and the projected distance between the two is smaller than 2 R 500 . Results. In the volume-limited sample, 48.6 −1.8 +1.8 % of FRIs and 30.6 −2.3 +2.5 % of FRIIs are associated with clusters. In the paired sample, 45.6 −3.1 +3.1 % of FRIs and 32.6 −2.8 +3.0 % of FRIIs are associated with clusters. This difference in cluster match fractions between FRIs and FRIIs in both samples becomes more pronounced at higher radio luminosities ( L 144 MHz > 10 26 W Hz −1 ). In the volume-limited sample, 55.6 −9.6 +9.2 % of luminous FRIs and 19.0 −4.6 +5.7 % of luminous FRIIs are associated with clusters. In the paired sample, 50.0 −12.9 +12.9 % of luminous FRIs and 6.7 −3.9 +9.5 % of luminous FRIIs are associated with clusters. Nevertheless, those FRIs and FRIIs that are associated with clusters show similar properties. In particular, the distributions of radio luminosity and stellar mass as functions of cluster richness and M 500 are similar for FRIs and FRIIs. The radial density profiles of cluster-associated FRIs and FRIIs both peak at 0.5 × R 500 and decline beyond R 500 , showing very similar spatial distributions within clusters. Furthermore, in the volume-limited sample, 74.8 −2.3 +2.2 % of cluster-associated FRIs and 61.9 −4.6 +4.4 % of cluster-associated FRIIs are identified as brightest cluster galaxies (BCGs). In the paired sample, 78.1 −4.0 +3.5 % of cluster-associated FRIs and 65.9 −5.3 +4.9 % of cluster-associated FRIIs are identified as BCGs. The median properties of these FRI-BCGs and FRII-BCGs, as well as those of their host clusters, do not show significant differences. Conclusions. Compared to FRIs, FRIIs are less frequently found in galaxy clusters, particularly at high radio luminosities. This pattern may be explained by the jet disruption scenario, in which the dense gas in galaxy clusters can slow down or disturb radio jets, making it more difficult for powerful FRII structures to form or remain stable. However, when FRIs and FRIIs do reside in clusters, they appear to inhabit similar environments in terms of richness, mass, and radial position. These findings suggest that, while the cluster-scale environment may influence the cluster match fraction, the morphological distinction between FRIs and FRIIs is unlikely to be primarily driven by cluster-scale properties alone. Improved estimates of cluster richness and mass will help to further clarify the extent to which the cluster environment influences the radio morphology of FRIs and FRIIs.

Abstract:

Radio source detection and morphological classification are fundamental for exploiting the scientific potential of modern radio continuum surveys. However, the rapidly increasing data volumes and the wide diversity of radio morphologies make traditional visual inspection infeasible and pose significant challenges for automated source finding. We apply a transformer-based set-prediction detector (RF-DETR) to 150 MHz continuum images from the LOFAR Deep Fields for instance-level source detection and morphological classification. The method is adapted to multi-frequency-synthesis images of interferometric data and trained with a morphology-driven scheme using five mutually exclusive classes. The model is trained on the ELAIS-N1 Deep Field, where it achieves high detection and classification performance ( per cent), and is then applied without retraining to the other three LOFAR Deep Fields. Across all four fields, the model yields consistent catalogues with modest field-to-field differences arising from survey depth and calibration. Compared with widely used PyBDSF catalogues, RF-DETR recovers the majority of PyBDSF sources while representing classical multi-component radio galaxies as single source-level detections rather than fragmented Gaussian components. Artefact-affected and spurious detections are identified as explicit classes, allowing these detections to be distinguished from general astrophysical sources in the resulting catalogues. As external validation, RF-DETR recovers the majority of visually identified extended and giant radio galaxies in the LOFAR Deep Fields and assigns them predominantly to extended morphological classes. These results indicate that transformer-based detectors provide a practical, scalable, morphology-aware approach to source finding in deep radio surveys, with clear relevance for forthcoming facilities such as SKA-Low.