Extremely Large Telescope

Abstract:

Abstract We obtain spatially resolved kinematics with the Keck Cosmic Web Imager (KCWI) integral-field spectrograph for a sample of 14 massive ( 11 < log 10 M * / M ⊙ < 12 ) lensing early-type galaxies at z ∼ 0.15–0.35 from the Sloan Lens ACS (SLACS) Survey. We integrate kinematic maps within the galaxy effective radius and examine the rotational and dispersion velocities, showing that 11/14 can be classified as slow rotators. The data set is unprecedented for galaxy-scale strong lenses in terms of signal-to-noise ratio (S/N), sampling, and calibration, vastly superseding previous studies. We find the primary contributions to systematic uncertainties to be the stellar template library and wavelength range of the spectral fit. Systematics are at the 1%–1.4% level, and positive covariance is <1% between sample galaxies and between spatial bins. This enables cosmographic inference with lensing time delays with a <2% uncertainty on H 0. We examine the effects of integration of the data cubes within circular apertures of different sizes and compare with Sloan Digital Sky Survey (SDSS) single-aperture velocity dispersions. We conclude that the velocity dispersions extracted from SDSS spectra for these 14 SLACS galaxies, which have low S/N (∼9 Å–1) relative to the SLACS candidate parent sample, are subject to systematic errors (and covariance) due to stellar template library selection at the level of 3% (2%), which need to be added to the random errors. Comparison between our KCWI stellar velocity dispersions, our own analysis of SDSS spectra, and previously published measurements based on SDSS spectra shows mean differences within a few percent. However, these differences are not significant given the uncertainties of the SDSS-based stellar velocity dispersions. We find that the correlations between scaling relations using quantities inferred from dynamical, lensing, and stellar population models agree with previous SLACS analysis with no statistically significant change. A follow-up paper will present Jeans modeling in the context of broader studies of galaxy evolution and cosmology.

Abstract:

Abstract We present high angular resolution (0.19 arcsec or ≈24 pc) Atacama Large Millimeter/submillimeter Array observations of the 12CO(3−2) line emission of the galaxy NGC 4751. The data provide evidence for the presence of a central supermassive black hole (SMBH). Assuming a constant mass-to-light ratio (M/L), we infer a SMBH mass $M_\text{BH}=3.43^{+0.45}_{-0.44}[\text{stat},\, 3\sigma ]^{+0.22}_{-0.64}[\text{sys}]\times 10^9$ M⊙ and a F160W filter stellar $M/L_{F160W}=2.68\pm 0.11[\text{stat},\, 3\sigma ]^{+0.10}_{-0.80}[\text{sys}]$ M⊙/L⊙, F160W, where the first uncertainties are statistical and the second systematic. Assuming a linearly spatially-varying M/L, we infer $M_\text{BH}=2.79^{+0.75}_{-0.57}[\text{stat},\, 3\sigma ]^{+0.75}_{-0.45}[\text{syst}]\times 10^9$ M⊙ and $\left(M/L_\text{F160W}\right)/\left(\text{M}_\odot /\text{L}_{\odot ,\text{F160W}}\right)=3.07^{+0.27}_{-0.35}[\text{stat},\, 3\sigma ]^{+0.08}_{-1.14}[\text{sys}]-0.09^{+0.08}_{-0.06}[\text{stat},\, 3\sigma ]^{+0.08}_{-0.01}[\text{sys}]\, \left(R/\text{arcsec}\right)$, where R is the galactocentric radius. We also present SMBH mass estimates using the Jeans Anisotropic Modelling (JAM) method and Very Large Telescope Spectrograph for INtegral Field Observations in the Near Infrared (SINFONI) stellar kinematics. Assuming a cylindrically-aligned velocity ellipsoid (JAMcyl) we infer MBH = (2.52 ± 0.36) × 109 M⊙, while assuming a spherically-aligned velocity ellipsoid (JAMsph) we infer MBH = (3.24 ± 0.87) × 109 M⊙. The SMBH mass assuming a constant M/L is statistically consistent with that of JAMsph, whereas the mass assuming a linearly-varying M/L is consistent with both JAMcyl and JAMsph (within the uncertainties). Our derived masses are larger than (and inconsistent with) one previous stellar dynamical measurement using the Schwarzschild orbit-superposition method and the same SINFONI kinematics.

Abstract:

Understanding the demographics of intermediate-mass black holes (IMBHs, MBH ≈ 102–105 M⊙) in low-mass galaxies is key to constraining black hole seed formation models, but detecting them is challenging due to their small gravitational sphere of influence (SOI). The upcoming Extremely Large Telescope (ELT) High Angular Resolution Monolithic Optical and Near-infrared Integral Field Spectrograph (HARMONI) instrument, with its high angular resolution, offers a promising solution. We present simulations assessing HARMONI’s ability to measure IMBH masses in nuclear star clusters (NSCs) of nearby dwarf galaxies. We selected a sample of 44 candidates within 10 Mpc. For two representative targets, NGC 300 and NGC 3115 dw01, we generated mock HARMONI integral-field data cubes using realistic inputs derived from Hubble Space Telescope imaging, stellar population models, and Jeans anisotropic models (JAM), assuming IMBH masses up to 1% of the NSC mass. We simulated observations across six near-infrared gratings at 10 mas resolution. Analyzing the mock data with standard kinematic extraction and JAM models in a Bayesian framework, we demonstrate that HARMONI can resolve the IMBH SOI and accurately recover masses down to ≈0.5% of the NSC mass within feasible exposure times. These results highlight HARMONI’s potential to revolutionize IMBH studies.