Galaxy formation and evolution

Abstract:

We measured the harmonic-space power spectrum of galaxy clustering auto-correlation from the Evolutionary Map of the Universe Pilot Survey 1 data (EMU PS1) and its cross-correlation with the lensing convergence map of cosmic microwave background (CMB) from Planck Public Release 4 at the linear scale range from ℓ = 2 to 500. We applied two flux density cuts at 0.18 and 0.4mJy on the radio galaxies observed at 944MHz and considered two source detection algorithms. We found the auto-correlation measurements from the two algorithms at the 0.18mJy cut to deviate for ℓ ≥ 250 due to the different criteria assumed on the source detection and decided to ignore data above this scale. We report a cross-correlation detection of EMU PS1 with CMB lensing at ∼5.5σ, irrespective of flux density cut. In our theoretical modelling we considered the SKADS and T-RECS redshift distribution simulation models that yield consistent results, a linear and a non-linear matter power spectrum, and two linear galaxy bias models. That is a constant redshift-independent galaxy bias b(z) = bg and a constant amplitude galaxy bias b(z) = bg/D(z). By fixing a cosmology model and considering a non-linear matter power spectrum with SKADS, we measured a constant galaxy bias at 0.18mJy (0.4mJy) with bg = 2.32-0.33^+0.41 (2.18-0.25^+0.17) and a constant amplitude bias with bg = 1.72-0.21^+0.31 (1.78-0.15^+0.22). When σ8 is a free parameter for the same models at 0.18mJy (0.4mJy) with the constant model we found σ8 = 0.68-0.14^+0.16 (0.82 ±0.10), while with the constant amplitude model we measured σ8 = 0.61-0.20^+0.18 (0.78-0.09^+0.11), respectively. Our results agree at 1σ with the measurements from Planck CMB and the weak lensing surveys and also show the potential of cosmology studies with future radio continuum survey data.

Abstract:

Early-type galaxies (ETGs) show a bimodal distribution in key structural properties like stellar specific angular momentum, kinematic morphology, shape, and nuclear surface brightness profiles. Slow rotator ETGs, mostly found in the densest regions of galaxy clusters, become common when the stellar mass exceeds a critical value of around M∗crit≈2×1011M⊙, or more precisely when lg(Re/kpc)≳12.4−lg(M∗/M⊙). These galaxies have low specific angular momentum, spheroidal shapes, and stellar populations that are old, metal-rich, and α-enhanced. In contrast, fast rotator ETGs form a continuous sequence of properties with spiral galaxies. In these galaxies, the age, metallicity, and α-enhancement of the stellar population correlate best with the effective stellar velocity dispersion σe∝M∗/Re (i.e., properties are similar for Re∝M∗), or with other proxies approximating their bulge mass fraction. This sequence spans from star-forming spiral disks to quenched, passive, spheroid-dominated fast rotator ETGs. Notably, at a fixed σe, younger galaxies show lower metallicity. The structural differences and environmental distributions of ETGs suggest two distinct formation pathways: slow rotators undergo early intense star formation followed by rapid quenching via their dark halos and supermassive black holes, and later evolve through dry mergers during hierarchical cluster assembly; fast rotators, on the other hand, develop more gradually through gas accretion and minor mergers, becoming quenched by internal feedback above a characteristic lg(σecrit/km s−1) ≳ 2.3 (in the local Universe) or due to environmental effects.

Abstract:

Almost every galaxy in the local Universe is observed to have a massive black hole in the center. The properties of these black holes are observed to tightly correlate with those of their host galaxy which has been interpreted as coevolution regulated by black hole feedback. This coevolution spans most of cosmic history, as the first active black holes, so-called active galactic nuclei, are already observed as early as z∼10. In this chapter, we lay out how we can find supermassive black holes, review what we know about the population of black holes and their host galaxies from observations, and summarize what we have learned about their coevolution across cosmic time from both observations and simulations.