Galaxy formation and evolution

Abstract:

We present JWST/NIRSpec IFU observations of the galaxy system B14-65666, as part of the GA-NIFS survey. Line and continuum emission in this massive system () is resolved into two strong cores surrounded by diffuse emission, as seen in recent JWST/NIRCam imaging. Our data set contains detections of [O ii], [Ne iii], Balmer lines, [O iii], He i, and weak [O iii]. Each spectrum is fit with a model that consistently incorporates interstellar medium conditions (i.e. electron temperature, , electron density, , and colour excess, ). The resulting line fluxes are used to constrain the gas-phase metallicity ( solar) and H-based star formation rate for each region. Common line ratio diagrams (O32–R23, R3–R2, Ne3O2–R23) reveal that each line-emitting region lies at the intersection of low- and high-redshift galaxies, suggesting low ionization and higher metallicity compared to the predominantly lower-mass galaxies studied with the JWST/NIRSpec IFU so far at . Spaxel-by-spaxel fits reveal evidence for both narrow (FWHM km s) and broad (FWHM km s) line emission, the latter of which likely represents tidal interaction or outflows. Comparison to ALMA [C ii]158m and [O iii]88 m data shows a similar velocity structure, and we explore optical-far infrared diagnostics. The two core galaxies both lie on the mass-metallicity relation at , but show contrasting properties (e.g. , ), suggesting distinct evolutionary pathways. Combining the NIRSpec IFU and ALMA data sets, our analysis opens new windows into the merging system B14-65666.

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.

Abstract:

Supermassive black hole (SMBH) binary systems are an unavoidable outcome of galaxy mergers. Their dynamics encode valuable information about their formation and growth, the composition of their host galactic nuclei, the evolution of galaxies, and the nature of gravity. Many SMBH binaries with separations pc-kpc have been found, but closer (subparsec) binaries remain to be confirmed. Identifying these systems may elucidate how binaries evolve past the “final parsec” until gravitational radiation drives them to coalescence. Methods to discover and characterize SMBH binaries can shed light on these important questions and potentially open new multimessenger channels. Here we show that SMBH binaries in nonactive galactic nuclei can be identified and characterized by the gravitational lensing of individual bright stars, located behind them in the host galaxy. The rotation of “caustics”—regions where sources are hugely magnified due to the SMBH binary’s orbit and inspiral—leads to quasiperiodic lensing of starlight (QPLS). The extreme lensing magnification of individual bright stars produces a significant variation in the host galaxies’ luminosity; their lightcurve traces the orbit of the SMBH binary and its evolution, analogous to the waveforms recorded by gravitational-wave (GW) detectors. QPLS probes the population of sources observable by pulsar timing arrays and space detectors (LISA, TianQin), offering advance warning triggers for merging SMBHs for coincident or follow-up GW detections. SMBH population models predict 1–50 $[190–5000](n_{\star }/{\mathrm{pc}}^{-3})$ QPLS binaries with period less than 10[40] yr with comparable masses and redshift $z<0.3$ , where $n_{\star }$ is the stellar number density. Additionally, stellar and orbital motion will lead to frequent instances of single or double flares caused by SMBHBs with longer periods. This novel signature can be searched for in a wealth of existing and upcoming time-domain photometric data: identifying quasiperiodic variability in galactic lightcurves will reveal an ensemble of binary systems and illuminate outstanding questions around them.

Abstract:

Deep radio continuum surveys provide fundamental constraints on galaxy evolution, but source confusion limits sensitivity to the faintest sources. We present a complete framework for producing high-fidelity deblended radio catalogues from the confused MIGHTEE maps using the probabilistic deblending framework XID+ and prior positions from deep multi-wavelength data in the COSMOS field. To assess performance, we construct MIGHTEE-like simulations based on the Tiered Radio Extragalactic Continuum Simulation radio source population, ensuring a realistic distribution of star-forming galaxies and active galactic nuclei for validation. Through these simulations, we show that prior catalogue purity is the dominant factor controlling deblending accuracy: a high-purity prior, containing only sources with a high likelihood of radio detection, recovers accurate flux densities and reproduces input source counts down to (where thermal noise). On the other hand, a complete prior overestimates the source counts due to spurious detections. Our optimal strategy combines the high-purity prior with a mask that removes sources detected above Jy. Applied to the 1.3 deg area of the MIGHTEE-COSMOS field defined by overlapping multi-wavelength data, this procedure yields a deblended catalogue of 89 562 sources. The derived 1.4 GHz source counts agree with independent P(D) analyses and indicate that we resolve the radio background to Jy. We also define a recommended high-fidelity sample of 20 757 sources, based on detection significance, flux density, and goodness-of-fit, which provides reliable flux densities for individual sources in the confusion-limited regime.