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Abstract:

The ringdown of a perturbed black hole contains fundamental information about space-time in the form of quasinormal modes (QNM). Modifications to general relativity, or extended profiles of other fields surrounding the black hole, so called "black hole hair", can perturb the QNM frequencies. Previous works have examined the QNM frequencies of spherically symmetric "dirty"black holes; that is black holes surrounded by arbitrary matter fields. Such analyses were restricted to static systems, making the assumption that the metric perturbation was independent of time. However, in most physical cases such black holes will actually be growing dynamically due to accretion of the surrounding matter. Here we develop a perturbative analytic method that allows us to compute for the first time the time dependent QNM deviations of such growing dirty black holes. Whilst both are small, we show that the change in QNM frequency due to the accretion can be of the same order or larger than the change due to the static matter distribution itself, and therefore should not be neglected in such calculations. We present the case of spherically symmetric accretion of a complex scalar field as an illustrative example, but the method has the potential to be extended to more complicated cases.

Abstract:

The Deep Extragalactic VIsible Legacy Survey (DEVILS) is an ongoing high-completeness, deep spectroscopic survey of ∼60 000 galaxies to Y < 21.2 mag, over ∼6 deg2 in three well-studied deep extragalactic fields: D10 (COSMOS), D02 (XMMLSS), and D03 (ECDFS). Numerous DEVILS projects all require consistent, uniformly derived and state-of-the-art photometric data with which to measure galaxy properties. Existing photometric catalogues in these regions either use varied photometric measurement techniques for different facilities/wavelengths leading to inconsistencies, older imaging data and/or rely on source detection and photometry techniques with known problems. Here, we use the PROFOUND image analysis package and state-of-the-art imaging data sets (including Subaru-HSC, VST-VOICE, VISTA-VIDEO, and UltraVISTA-DR4) to derive matched-source photometry in 22 bands from the FUV to 500 μm. This photometry is found to be consistent, or better, in colour analysis to previous approaches using fixed-size apertures (which are specifically tuned to derive colours), but produces superior total source photometry, essential for the derivation of stellar masses, star formation rates, star formation histories, etc. Our photometric catalogue is described in detail and, after internal DEVILS team projects, will be publicly released for use by the broader scientific community.

Abstract:

Galactic scale tests have proven to be powerful tools in constraining fundamental physics in previously under-explored regions of parameter space. The astrophysical regime which they probe is inherently complicated, and the inference methods used to make these constraints should be robust to baryonic effects. Previous analyses have assumed simple empirical models for astrophysical noise without detailed calibration or justification. We outline a framework for assessing the reliability of such methods by constructing and testing more advanced baryonic models using cosmological hydrodynamical simulations. As a case study, we use the Horizon-AGN simulation to investigate warping of stellar disks and offsets between gas and stars within galaxies, which are powerful probes of screened fifth forces. We show that the degree of `U'-shaped warping of galaxies is well modelled by Gaussian random noise, but that the magnitude of the gas-star offset is correlated with the virial radius of the host halo. By incorporating this correlation we confirm recent results ruling out astrophysically relevant Hu-Sawicki $f(R)$ gravity, and identify a $\sim 30\%$ systematic uncertainty due to baryonic physics. Such an analysis must be performed case-by-case for future galactic tests of fundamental physics.

Abstract:

<jats:p>We measured the cross-correlation between galaxy weak lensing data from the Kilo Degree Survey (KiDS-1000, DR4) and cosmic microwave background (CMB) lensing data from the Atacama Cosmology Telescope (ACT, DR4) and the <jats:italic>Planck</jats:italic> Legacy survey. We used two samples of source galaxies, selected with photometric redshifts, (0.1 &lt; <jats:italic>z</jats:italic><jats:sub>B</jats:sub> &lt; 1.2) and (1.2 &lt; <jats:italic>z</jats:italic><jats:sub>B</jats:sub> &lt; 2), which produce a combined detection significance of the CMB lensing and weak galaxy lensing cross-spectrum of 7.7<jats:italic>σ</jats:italic>. With the lower redshift galaxy sample, for which the cross-correlation was detected at a significance of 5.3<jats:italic>σ</jats:italic>, we present joint cosmological constraints on the matter density parameter, Ω<jats:sub>m</jats:sub>, and the matter fluctuation amplitude parameter, <jats:italic>σ</jats:italic><jats:sub>8</jats:sub>, marginalising over three nuisance parameters that model our uncertainty in the redshift and shear calibration as well as the intrinsic alignment of galaxies. We find our measurement to be consistent with the best-fitting flat ΛCDM cosmological models from both <jats:italic>Planck</jats:italic> and KiDS-1000. We demonstrate the capacity of CMB weak lensing cross-correlations to set constraints on either the redshift or shear calibration by analysing a previously unused high-redshift KiDS galaxy sample (1.2 &lt; <jats:italic>z</jats:italic><jats:sub>B</jats:sub> &lt; 2), with the cross-correlation detected at a significance of 7<jats:italic>σ</jats:italic>. This analysis provides an independent assessment for the accuracy of redshift measurements in a regime that is challenging to calibrate directly owing to known incompleteness in spectroscopic surveys.</jats:p>