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1. The evolution of the size–mass relation at z = 1–3 derived from the complete Hubble Frontier Fields data set

   https://doi.org/10.1093/mnras/staa3713  

   Yang, Lilan; Roberts-Borsani, Guido; Treu, Tommaso; Birrer, Simon; Morishita, Takahiro; Bradač, Maruša (December 2020, Monthly Notices of the Royal Astronomical Society)

   null (Ed.)

   ABSTRACT We measure the size–mass relation and its evolution between redshifts 1 < z < 3, using galaxies lensed by six foreground Hubble Frontier Fields clusters. The power afforded by strong gravitation lensing allows us to observe galaxies with higher angular resolution beyond current facilities. We select a stellar mass limited sample and divide them into star-forming or quiescent classes based on their rest-frame UVJ colours from the ASTRODEEP catalogues. Source reconstruction is carried out with the recently released lenstruction software, which is built on the multipurpose gravitational lensing software lenstronomy. We derive the empirical relation between size and mass for the late-type galaxies with $$M_{*}\gt 3\times 10^{9}\, \mathrm{M}_{\odot }$$ at 1 < z < 2.5 and $$M_{*}\gt 5\times 10^{9}\, \mathrm{M}_{\odot }$$ at 2.5 < z < 3, and at a fixed stellar mass, we find galaxy sizes evolve as $$R \rm _{eff} \propto (1+z)^{-1.05\pm 0.37}$$. The intrinsic scatter is <0.1 dex at z < 1.5 but increases to ∼0.3 dex at higher redshift. The results are in good agreement with those obtained in blank fields. We evaluate the uncertainties associated with the choice of lens model by comparing size measurements using five different and publicly available models, finding the choice of lens model leads to a 3.7 per cent uncertainty of the median value, and ∼25  per cent scatter for individual galaxies. Our work demonstrates the use of strong lensing magnification to boost resolution does not introduce significant uncertainties in this kind of work, and paves the way for wholesale applications of the sophisticated lens reconstruction technique to higher redshifts and larger samples. 

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2. Probing sub-galactic mass structure with the power spectrum of surface-brightness anomalies in high-resolution observations of galaxy–galaxy strong gravitational lenses. II. Observational constraints on the subgalactic matter power spectrum

   https://doi.org/10.1093/mnras/stad1402  

   Bayer, D.; Chatterjee, S.; Koopmans, L. V. E.; Vegetti, S.; McKean, J. P.; Treu, T.; Fassnacht, C. D.; Glazebrook, K. (May 2023, Monthly Notices of the Royal Astronomical Society)

   ABSTRACT Stringent observational constraints on the subgalactic matter power spectrum would allow one to distinguish between the concordance ΛCDM and the various alternative dark-matter models that predict significantly different properties of mass structure in galactic haloes. Galaxy–galaxy strong gravitational lensing provides a unique opportunity to probe the subgalactic mass structure in lens galaxies beyond the Local Group. Here, we demonstrate the first application of a novel methodology to observationally constrain the subgalactic matter power spectrum in the inner regions of massive elliptical lens galaxies on 1–10 kpc scales from the power spectrum of surface-brightness anomalies in highly magnified galaxy-scale Einstein rings and gravitational arcs. The pilot application of our approach to Hubble Space Telescope (HST/WFC3/F390W) observations of the SLACS lens system SDSS J0252+0039 allows us to place the following observational constraints (at the 99 per cent confidence level) on the dimensionless convergence power spectrum $$\Delta ^{2}_{\delta \kappa }$$ and the standard deviation in the aperture mass σAM: $$\Delta ^{2}_{\delta \kappa }\lt 1$$ (σAM < 0.8 × 108 M⊙) on 0.5-kpc scale, $$\Delta ^{2}_{\delta \kappa }\lt 0.1$$ (σAM < 1 × 108 M⊙) on 1-kpc scale and $$\Delta ^{2}_{\delta \kappa }\lt 0.01$$ (σAM < 3 × 108 M⊙) on 3-kpc scale. These first upper-limit constraints still considerably exceed the estimated effect of CDM subhaloes. However, future analysis of a larger sample of galaxy–galaxy strong lens systems can substantially narrow down these limits and possibly rule out dark-matter models that predict a significantly higher level of density fluctuations on the critical subgalactic scales. 

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3. GRRMHD simulations of MAD accretion discs declining from super-Eddington to sub-Eddington accretion rates

   https://doi.org/10.1093/mnras/stac3330  

   Curd, Brandon; Narayan, Ramesh (November 2022, Monthly Notices of the Royal Astronomical Society)

   ABSTRACT We present two general relativistic radiation magnetohydrodynamics (GRRMHD) simulations of magnetically arrested discs (MADs) around non-spinning (a* = 0) and spinning (a* = 0.9) supermassive black holes (BHs). In each simulation, the mass accretion rate is decreased with time such that we sample Eddington-scaled rates over the range $$3 \gtrsim \dot{M}/\dot{M}_{\rm {Edd}}\gtrsim 0.3$$. For the non-spinning BH model, the total and radiative efficiencies increase as the accretion rate decreases, varying over the range $$\eta _{\rm {tot}}\sim 9\!-\!16{{\ \rm per\ cent}}$$ and $$\eta _{\rm {rad}}\sim 6{-}12{{\ \rm per\ cent}}$$, respectively. This model shows very little jet activity. In contrast, the spinning BH model has a strong relativistic jet powered by spin energy extracted from the BH. The jet power declines with accretion rate such that $$\eta _{\rm {jet}}\sim 18{-}39{{\ \rm per\ cent}}$$ while the total and radiative efficiencies are $$\eta _{\rm {tot}}\sim 64{-}100{{\ \rm per\ cent}}$$ and $$\eta _{\rm {rad}}\sim 45{-}79{{\ \rm per\ cent}}$$, respectively. We confirm that mildly sub-Eddington discs can extract substantial power from a spinning BH, provided they are in the MAD state. The jet profile out to $$100\, GM/c^2$$ is roughly parabolic with a power-law index of k ≈ 0.43−0.53 during the sub-Eddington evolution. Both models show significant variability in the outgoing radiation which is likely associated with episodes of magnetic flux eruptions. The a* = 0.9 model shows semiregular variations with a period of $$\sim 2000\, GM/c^3$$ over the final $$\sim 10\, 000\, GM/c^3$$ of the simulation, which suggests that magnetic flux eruptions may be an important source of quasi-periodic variability. For the simulated accretion rates, the a* = 0 model is spinning up while the a* = 0.9 model is spinning down. Spinup–spindown equilibrium of the BH will likely be achieved at 0.5 < a*, eq < 0.6, assuming continuous accretion in the MAD state. 

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4. Overconstrained gravitational lens models and the Hubble constant

   https://doi.org/10.1093/mnras/staa344  

   Kochanek, C S (April 2020, Monthly Notices of the Royal Astronomical Society)

   ABSTRACT It is well known that measurements of H0 from gravitational lens time delays scale as H0 ∝ 1 − κE, where κE is the mean convergence at the Einstein radius RE but that all available lens data other than the delays provide no direct constraints on κE. The properties of the radial mass distribution constrained by lens data are RE and the dimensionless quantity ξ = REα″(RE)/(1 − κE), where α″(RE) is the second derivative of the deflection profile at RE. Lens models with too few degrees of freedom, like power-law models with densities ρ ∝ r−n, have a one-to-one correspondence between ξ and κE (for a power-law model, ξ = 2(n − 2) and κE = (3 − n)/2 = (2 − ξ)/4). This means that highly constrained lens models with few parameters quickly lead to very precise but inaccurate estimates of κE and hence H0. Based on experiments with a broad range of plausible dark matter halo models, it is unlikely that any current estimates of H0 from gravitational lens time delays are more accurate than $${\sim} 10{{\ \rm per\ cent}}$$, regardless of the reported precision. 

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5. A lack of constraints on the cold opaque H  i mass: H  i spectra in M31 and M33 prefer multicomponent models over a single cold opaque component

   https://doi.org/10.1093/mnras/stab981  

   Koch, Eric W; Rosolowsky, Erik W; Leroy, Adam K; Chastenet, Jérémy; Chiang; Dalcanton, Julianne; Kepley, Amanda A; Sandstrom, Karin M; Schruba, Andreas; Stanimirović, Snežana; et al (April 2021, Monthly Notices of the Royal Astronomical Society)

   null (Ed.)

   ABSTRACT Previous work has argued that atomic gas mass estimates of galaxies from 21-cm H i emission are systematically low due to a cold opaque atomic gas component. If true, this opaque component necessitates a $$\sim 35{{\ \rm per\ cent}}$$ correction factor relative to the mass from assuming optically thin H i emission. These mass corrections are based on fitting H i spectra with a single opaque component model that produces a distinct ‘top-hat’ shaped line profile. Here, we investigate this issue using deep, high spectral resolution H i VLA observations of M31 and M33 to test if these top-hat profiles are instead superpositions of multiple H i components along the line of sight. We fit both models and find that $${\gt}80{{\ \rm per\ cent}}$$ of the spectra strongly prefer a multicomponent Gaussian model while $${\lt}2{{\ \rm per\ cent}}$$ prefer the single opacity-corrected component model. This strong preference for multiple components argues against previous findings of lines of sight dominated by only cold H i. Our findings are enabled by the improved spectral resolution (0.42 $${\rm km\, s^{-1}}$$), whereas coarser spectral resolution blends multiple components together. We also show that the inferred opaque atomic ISM mass strongly depends on the goodness-of-fit definition and is highly uncertain when the inferred spin temperature has a large uncertainty. Finally, we find that the relation of the H i surface density with the dust surface density and extinction has significantly more scatter when the inferred H i opacity correction is applied. These variations are difficult to explain without additionally requiring large variations in the dust properties. Based on these findings, we suggest that the opaque H i mass is best constrained by H i absorption studies. 

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