Galaxy formation and evolution

Abstract:

Abstract We present the first results of the H i intensity mapping power spectrum analysis with the MeerKAT International GigaHertz Tiered Extragalactic Exploration (MIGHTEE) survey. We use data covering ∼ 4 square degrees in the COSMOS field using a frequency range 962.5 MHz to 1008.42 MHz, equivalent to H i emission in 0.4 < z < 0.48. The data consists of 15 pointings with a total of 94.2 hours on-source. We verify the suitability of the MIGHTEE data for H i intensity mapping by testing for residual systematics across frequency, baselines and pointings. We also vary the window used for H i signal measurements and find no significant improvement using stringent Fourier mode cuts. We compute the H i power spectrum at scales 0.5 Mpc−1 ≲ k ≲ 10 Mpc−1 in auto-correlation as well as cross-correlation between observational scans using power spectrum domain averaging for pointings. We report consistent upper limits of 29.8  mK2Mpc3 from the 2σ cross-correlation measurements and 25.82 mK2Mpc3 from auto-correlation at k ∼2 Mpc−1.The low signal-to-noise in this data potentially limits our ability to identify residual systematics, which will be addressed in the future by incorporating more data in the analysis.

Abstract:

Abstract We present a new measurement of the dark and luminous matter distribution of massive elliptical galaxies, and their evolution with redshift, by combining strong lensing and dynamical observables. Our sample of 56 lens galaxies covers a redshift range of 0.090 ≤ zl ≤ 0.884. By combining new Hubble Space Telescope imaging with previously observed velocity dispersion and line-of-sight measurements, we decompose the luminous matter profile from the dark matter profile and perform a Bayesian hierarchical analysis to constrain the population-level properties of both profiles. We find that the inner slope of the dark matter density profile (‘cusp’; $\rho _{\rm DM} \propto r^{-\gamma _{\rm in}}$) is consistent ($\mu _{\gamma _{\rm in}}=0.97^{+0.03}_{-0.03}$ with ≤0.07 intrinsic scatter) with a standard Navarro–Frenk–White (NFW; γin = 1) at z = 0.35. Additionally, we find an appreciable evolution with redshift ($d\log (\gamma _{\rm in})/dz=-0.44^{+0.14}_{-0.15}$) resulting in a shallower slope (of >2σ tension from NFW) at redshifts z ≥ 0.49. This is in excellent agreement with previous population-level observational studies, as well as with predictions from hydrodynamical simulations such as IllustrisTNG. We also find the stellar mass-to-light ratio at the population level is consistent with that of a Salpeter initial mass function, a small stellar mass-to-light gradient (κ*(r)∝r−η, with $\overline{\eta } \le 5 \times 10^{-5}$), and isotropic stellar orbits. Our averaged total mass density profile is consistent with a power-law profile within 0.25 to 4 Einstein radii ($\overline{\gamma } = 2.24 \pm 0.14$), with an internal mass-sheet transformation parameter $\overline{\lambda } = 0.96 \pm 0.03$ consistent with no mass sheet. Our findings confirm the validity of the standard mass models used for time-delay cosmography.

Abstract:

The topology of reionization and the environments where galaxies efficiently produce ionizing photons are key open questions. For the first time, we investigate the trend between ionizing photon production efficiency, ξion, and galaxy overdensity, log(1+δ) . We analyze the ionizing properties of 79 galaxies between 1.0 < z < 5.2 using JWST NIRSpec medium-resolution spectra from the Systematic Mid-infrared Instrument Legacy Extragalactic Survey (SMILES) program. Among these, 67 galaxies have Hα coverage, spanning 1.0 < z < 3.1. The galaxy overdensity, log(1+δ) , is measured using the JADES photometric catalog, which covers the SMILES footprint. For the subset with Hα coverage, we find that logξion is positively correlated with log(1+δ) , with a slope of 0.94−0.46+0.46 . Additionally, the mean ξion for galaxies in overdense regions ( log(1+δ)>0.1 ) is 2.43 times that of galaxies in lower density regions ( log(1+δ)<0.1 ). This strong trend is found to be independent of redshift evolution. Furthermore, our results confirm the robust correlations between ξion and the rest-frame equivalent widths of the [O iii] or Hα emission lines. Our results suggest that galaxies in high-density regions are efficient producers of ionizing photons.

Abstract:

<jats:p>We present accurate mass measurements of the central supermassive black hole (SMBH) in NGC 4736 (M 94). We used the “gold-standard” stellar absorption features (CO band heads) at ∼2.3 μm, as opposed to gas emission lines, to trace the dynamics in the nuclear region, easily resolving the SMBH’s sphere of influence. The analysis uses observations made with the integral field unit of the Near-Infrared Spectrograph (NIRSpec) on the <jats:italic>James Webb</jats:italic> Space Telescope and a surface brightness profile derived from <jats:italic>Hubble</jats:italic> Space Telescope archival images. We used Jeans anisotropic models within a Bayesian framework, and comprehensive Markov chain Monte Carlo optimization, to determine the best-fit black hole mass, orbital anisotropy, mass-to-light ratio, and nucleus kinematical inclination. We obtained a SMBH mass <jats:italic>M</jats:italic><jats:sub>BH</jats:sub> = (1.60 ± 0.16)×10<jats:sup>7</jats:sup> M<jats:sub>⊙</jats:sub> (1<jats:italic>σ</jats:italic> random error), which is consistent with the <jats:italic>M</jats:italic><jats:sub>BH</jats:sub>–<jats:italic>σ</jats:italic> and <jats:italic>M</jats:italic><jats:sub>BH</jats:sub>–<jats:italic>M</jats:italic><jats:sub>⋆</jats:sub> relations. This is the first dynamical measurement of a <jats:italic>M</jats:italic><jats:sub>BH</jats:sub> in NGC 4736 based on the stellar kinematics observed with NIRSpec. We thus settle a longstanding inconsistency between estimates based on nuclear emission-line tracers and the <jats:italic>M</jats:italic><jats:sub>BH</jats:sub>–<jats:italic>σ</jats:italic> relation. Our analysis shows that NIRSpec can detect SMBHs with <jats:italic>M</jats:italic><jats:sub>BH, min</jats:sub> ≈ 5 × 10<jats:sup>6</jats:sup> M<jats:sub>⊙</jats:sub> in galaxies within 5 Mpc and <jats:italic>σ</jats:italic> ≈ 100 km s<jats:sup>−1</jats:sup>.</jats:p>