Michele Cappellari

Abstract:

The spectral resolution (R ≡ λ/Δλ) of spectroscopic data is crucial information for accurate kinematic measurements. In this letter we present a robust measurement of the spectral resolution of the JWST Near Infrared Spectrograph (NIRSpec) in fixed slit (FS) and integral field spectroscopy (IFS) modes. Due to the similarity of the utilized slit dimension in the FS mode to that of the shutters in the multi-object spectroscopy (MOS) mode, our resolution measurements in the FS mode can also be used for the MOS mode in principle. We modeled H and He lines of the planetary nebula SMP LMC 58 using a Gaussian line spread function (LSF) to estimate the wavelength-dependent resolution for multiple disperser and filter combinations. We corrected for the intrinsic width of the planetary nebula’s H and He lines due to its expansion velocity by measuring it from a higher-resolution X-shooter spectrum. We find that NIRSpec’s in-flight spectral resolutions exceed the pre-launch estimates provided in the JWST User Documentation by 11–53% in the FS mode and by 1–24% in the IFS mode across the covered wavelengths. We recover the expected trend that the resolution increases with the wavelength within a configuration. The robust and accurate LSFs presented in this letter will enable high-accuracy kinematic measurements using NIRSpec for applications in cosmology and galaxy evolution.

Abstract:

We derive circular velocity curves (CVCs) from stellar dynamical models for ∼6000 nearby galaxies in the final data release of the Sloan Digital Sky Survey-IV MaNGA survey with integral-field spectroscopy, exploring connections between the inner gravitational potential (traced by CVC amplitude/shape) and galaxy properties. The maximum circular velocity ( Vcircmax ) and circular velocity at the half-light radius ( Vcirc(Remaj) ) both scale linearly with the stellar second velocity moment σe2≡〈V2+σ2〉 within the half-light isophote, following Vcircmax≈1.72σe (7% error) and Vcirc(Remaj)≈1.62σe (7% error). CVC shapes (rising, flat, declining) correlate strongly with structural and stellar population properties: declining curves dominate in massive, early-type, bulge-dominated galaxies with old, metal-rich stars and early quenching, while rising CVCs prevail in disk-dominated systems with younger stellar populations and ongoing star formation. Using a unified bulge–disk–halo model, we predict CVC shapes with minimal bias, identifying three governing parameters: bulge-to-total mass ratio (B/T), dark matter fraction within Re, and bulge Sérsic index. The distribution of CVC shapes across the mass–size plane reflects evolutionary pathways driven by (i) in situ star formation (spurring bulge growth) and (ii) dry mergers. This establishes CVC morphology as a diagnostic for galaxy evolution, linking dynamical signatures to structural and stellar population histories.

Abstract:

Time-delay distance measurements from strongly lensed quasars provide a robust and independent method for determining the Hubble constant (H0). This approach offers a crucial cross-check against H0 measurements obtained from the standard distance ladder in the late Universe and the cosmic microwave background in the early Universe. The mass-sheet degeneracy in strong-lensing models may introduce a significant systematic uncertainty, however, that limits the precision of H0 estimates. Dynamical modeling complements strong lensing very well to break the mass-sheet degeneracy because both methods model the mass distribution of galaxies, but rely on different sets of observational constraints. We developed a method and software framework for an efficient joint modeling of stellar kinematic and lensing data. Using simulated lensing and kinematic data of the lensed quasar system RXJ1131−1131 as a test case, we demonstrate that a precision of approximately 4% on H0 can be achieved with high-quality data that have a high signal-to-noise ratio. Through extensive modeling, we examined the impact of a supermassive black hole in the lens galaxy and potential systematic biases in kinematic data on the H0 measurements. Our results demonstrate that either using a prior range for the black hole mass and orbital anisotropy, as motivated by studies of nearby galaxies, or excluding the central bins in the kinematic data can effectively mitigate potential biases on H0 induced by the black hole. By testing the model on mock kinematic data with values that were systematically biased, we emphasize that it is important to use kinematic data with systematic errors below the subpercent level, which can currently be achieved. Additionally, we leveraged GPU parallelization to accelerate the Bayesian inference. This reduced a previously month-long process by an order of magnitude. This pipeline offers significant potential for advancing cosmological and galaxy evolution studies with large datasets.

Abstract:

We obtain spatially resolved kinematics with the Keck Cosmic Web Imager (KCWI) integral-field spectrograph for a sample of 14 massive ( 11