Astronomical instrumentation

Abstract:

Despite its proximity, the mass of the supermassive black hole (SMBH) in the spiral galaxy M81 (NGC 3031) has remained a subject of discussion, with doubts previously cast on the reliability of available dynamical measurements. We present the first robust stellar-dynamics measurement of its mass using high-resolution, two-dimensional kinematics from JWST/NIRSpec observations of the central 3″ × 3″. By tracing stellar motions in the near-infrared, our data penetrate the obscuring nuclear dust and allow for the separation of stellar light from the nonthermal AGN continuum. We modeled the kinematics using the Jeans anisotropic modelling method. Rather than relying on a standard Bayesian approach for error estimation, we constructed a suite of 24 independent models, each employing a unique combination of different physical assumptions regarding stellar mass-to-light (M/L) ratio gradients, the point-spread function, the masking of the central active galactic nucleus, and the orientation of the velocity ellipsoid. This ensemble approach allows us to robustly account for the impact of systematic uncertainties. To estimate our systematic uncertainties, we performed a bootstrap of the MBH values derived from these 24 models, thereby incorporating the variance between different physical assumptions. Our analysis yields a precise SMBH mass of MBH = (4.77 ± 0.37) × 107 M⊙ (1σ confidence, including systematic and statistical uncertainties). This result is consistent with previous determinations within their uncertainties, while providing a crucial and highly reliable anchor point for SMBH–galaxy scaling relations in spiral galaxies.

Abstract:

We conduct a search for strong gravitational lenses in the Dark Energy Survey (DES) Year 6 imaging data. We implement a pre-trained Vision Transformer (ViT) for our machine learning (ML) architecture and adopt interactive machine learning to construct a training sample with multiple classes to address common types of false positives. Our ML model reduces ∼236 million DES cutout images to 22,564 targets of interest, including ∼85% of previously reported galaxy–galaxy lens candidates discovered in DES. These targets were visually inspected by citizen scientists, who ruled out ∼90% as false positives. Of the remaining 2618 candidates, 149 were expert-classified as “definite” lenses and 516 as “probable” lenses, for a total of 665 systems, with 147 of these candidates being newly identified. Additionally, we trained a second ViT to find double-source plane lens systems, finding at least one double-source system. Our main ViT excels at identifying galaxy–galaxy lenses, consistently assigning high scores to candidates with high expert assessments. The top 800 ViT-scored images include ∼100 of our “definite” lens candidates. This selection is an order of magnitude higher in purity than previous convolutional neural-network-based lens searches and demonstrates the feasibility of applying our methodology for discovering large samples of lenses in future surveys.

Abstract:

We present a detailed study of the inner regions of NGC 7582, a nearby Seyfert 2 galaxy, from the Galaxy Activity, Torus, and Outflow Survey (GATOS). The galaxy hosts a circumnuclear star-forming disc and an active galactic nucleus (AGN)-driven biconical ionized outflow. Using James Webb Space Telescope Near-Infrared Spectrograph (NIRSpec) and Mid-Infrared Instrument/Medium-Resolution Spectrometer (MIRI/MRS) integral-field spectroscopy, we analyse ionic emission lines spanning a wide range of ionization potentials (IPs, –126 eV). Gaussian line-profile fitting reveals kinematic stratification: low-IP species ( eV; e.g. [Fe ii], [Ar ii], and [Ne ii]) trace ordered disc rotation with PA , while high-IP species ( eV; e.g. [O iv], [Mg iv], and [Ne v]) follow the outflow with PA . Outflowing gas exhibits systematically higher velocity dispersions ( km s−1) than the disc ( km s−1), consistent with turbulent or bulk motions. Intermediate-IP lines, [S iii], [Ar iii], and [Ne iii], show contributions from both components, with the outflow characterized by higher dispersion, lower amplitude, and higher velocities in double-Gaussian fits. For these lines, a thin inclined disc plus 1D outflow model enables robust separation and quantification of the disc and outflow velocity fields. The outflow is consistent with a hollow bicone capable of accelerating gas beyond the local escape velocity, implying most material is unlikely to be re-accreted. The ionization cone opening angle shows no dependence on IP, indicating the AGN torus polar regions are largely unobscured. Our study provides new insights into AGN-driven outflows and circumnuclear disc dynamics, offering a framework to disentangle overlapping interstellar medium kinematics in nearby active galaxies.