Bohan Yue

Abstract:

Abstract Cosmic filaments have been recognised as influencing galaxy evolution, but their connection to galactic cold gas reservoirs is elusive, particularly at low redshifts. We investigate the influence of filaments on neutral hydrogen (H i) detections in galaxies at 0.02 < z < 0.09, using the MeerKAT International GHz Tiered Extragalactic Exploration (MIGHTEE) survey in the COSMOS and XMM-LSS fields. We measure the fraction of optical galaxies from the Dark Energy Spectroscopic Instrument (DESI) Survey detected in H i emission as a function of stellar mass, morphology, local density, and the distance to the nearest filament. We find that galaxies closer to filaments have higher stellar masses, higher local densities, and a larger early-type fraction, all of which affect the H i detection. After controlling for these dependencies, filaments have measurable effects on H i detection. Late-type galaxies in low-local density environments show reduced H i detection fractions close to filaments across all stellar mass ranges, suggesting potential gas depletion through ram pressure stripping and cosmic web detachment. Massive early-type galaxies show an enhanced H i detection fraction in filaments compared to the voids, suggesting possible gas replenishment through filamentary accretion or gas-rich mergers. Our results suggest that cosmic filaments influence galactic H i gas reservoirs through various competing processes, whose relative importance varies with stellar mass and local density.

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:

ABSTRACT We study the spatially resolved star formation, gas ionization, and outflow properties of 1813 active galactic nuclei (AGNs) from the MaNGA survey, which we classify into infrared (IR), broad-line (BL), narrow-line (NL), and radio (RD) AGNs based on their mid-infrared colours, optical spectra, and/or radio photometry. We also provide estimations of AGN power at different wavelengths. AGN incidence is found to increase with stellar mass following a power law, with the high-mass end dominated by RDAGNs and the low-mass end dominated by NLAGNs. Compared to their mass-matched non-AGN counterparts, we find that IRAGNs, BLAGNs, and NLAGNs on average show enhanced specific star formation rates, younger stellar populations, and harder ionization towards the centre. RDAGNs, in contrast, show radial profiles similar to quiescent galaxies. [O iii] outflows are more common and stronger in BL/IRAGNs, while RDAGNs on average show no outflow features. The outflow incidence increases with [O iii] luminosity, and the features in BL/IRAGNs on average extend to $\sim$2 kpc from the nuclei. We further discuss a possible evolutionary sequence of AGNs and their host galaxies, where AGNs with strong emission lines or dust tori are present in star-forming galaxies. Later, young compact radio jets emerge, the host galaxies gradually quench, and the AGN hosts eventually evolve into globally quiescent systems with larger radio jets that prevent further gas cooling.