Exploring the possibility that fundamental constants of Nature might vary temporally or spatially constitutes one of the key science drivers for the European Southern Observatory's ESPRESSO spectrograph on the VLT and for the HIRES spectrograph on the ELT. High-resolution spectra of quasar absorption systems permit accurate measurements of fundamental constants out to high redshifts. The quality of new data demands completely objective and reproducible methods. We have developed a new fully automated Artificial Intelligence-based method capable of deriving optimal models of even the most complex absorption systems known. The AI structure is built around VPFIT, a well-developed and extensively-tested non-linear least-squares code. The new method forms a sophisticated parallelised system, eliminating human decision-making and hence bias. Here we describe the workings of such a system and apply it to synthetic spectra, in doing so establishing methods of importance for future analyses of VLT and ELT data. The results show that modelling line broadening for high-redshift absorption components should include both thermal and turbulent components. Failing to do so means it is easy to derive the wrong model and hence incorrect parameter estimates. We also argue that model non-uniqueness can be significant, such that it is not feasible to expect to derive an unambiguous estimate of the fine structure constant alpha from one or a small number of measurements. No matter how optimal the modelling method, it is a fundamental requirement to use a large sample of measurements to meaningfully constrain temporal or spatial alpha variation.
We present photoionisation modelling of the intrinsic absorber in the bright quasar HS 1603+3820. We construct spectral energy distribution using optical/UV/X-ray observations as an input to photoionisation calculations. Spectra from Keck telescope show extremely high ratio of CIV to HI, for the first absorber in system A, named A1. This value, together with high column density of CIV ion, puts strong constraints on photoionisation model. We use photoionisation modeling to derive hydrogen number density at the cloud illuminated surface. Estimating bolometric luminosity of HS 1603+3820, from ty…
We devise an optimal method to measure the temporal power spectrum of the lensing and intrinsic fluctuations of multiply-imaged strongly lensed quasar light curves, along with the associated time delays. The method is based on a Monte-Carlo Markov Chain (MCMC) sampling of a putative gaussian likelihood, and accurately recovers the input properties of simulated light curves, as well as the "Time Delay Challenge". We apply this method to constrain the dimensionless cosmological (non-linear) matter power spectrum on milliparsec scales (comparable to the size of the solar system), to $Δ_{\rm NL}^2…
Cosmological gravitational microlensing has been proven to be a powerful tool to constrain the structure of multiply imaged quasars, especially the accretion disc and central supermassive black-hole system. However, the derived constraints on models may be affected by large systematic errors introduced in the various stages of modelling, namely, the macromodels, the microlensing magnification maps, and the convolution with realistic disc profiles. In particular, it has been known that different macromodels of the galaxy lens that fit the observations equally well, can lead to different values …
Quadruply lensed quasars are extremely rare objects, but incredibly powerful cosmological tools. Only few dozen are known in the whole sky. Here we present the spectroscopic confirmation of two new quadruplets WG0214-2105 and WG2100-4452 discovered by Agnello & Spiniello (2018) within the Dark Energy Survey (DES) public footprints. We have conducted spectroscopic follow-up of these systems with the Southern African Large Telescope as part of a program that aims at confirming the largest possible number of optically selected strong gravitational lensing systems in the Equatorial and Southern He…
We present an analysis of 23 absorption systems along the lines of sight towards 18 quasars in the redshift range of $0.4 \leq z_{abs} \leq 2.3$ observed on the Very Large Telescope (VLT) using the Ultraviolet and Visual Echelle Spectrograph (UVES). Considering both statistical and systematic error contributions we find a robust estimate of the weighted mean deviation of the fine-structure constant from its current, laboratory value of $Δα/α=\left(0.22\pm0.23\right)\times10^{-5}$, consistent with the dipole variation reported in Webb et al. and King et al. This paper also examines modelling me…
This article reviews the two major recent developments that significantly improved cosmological measurements of fundamental constants derived from high resolution quasar spectroscopy. The first one is the deployment of astronomical Laser Frequency Combs on high resolution spectrographs and the second one is the development of spectral analysis tools based on Artificial Intelligence methods. The former all but eliminated the previously dominant source of instrumental uncertainty whereas the latter established optimal methods for measuring the fine structure constant ($α$) in quasar absorption s…
Infrared spectroscopy of the H-alpha emission lines of a sub-sample of 19 high-redshift (0.8 < z < 2.3) Molonglo quasars, selected at 408 MHz, is presented. These emission lines are fitted with composite models of broad and narrow emission, which include combinations of classical broad-line regions of fast-moving gas clouds lying outside the quasar nucleus, and/or a theoretical model of emission from an optically-thick, flattened, rotating accretion disk. All bar one of the nineteen sources are found to have emission consistent with the presence of an optically-emitting accretion disk, with th…
High resolution spectra of quasar absorption systems provide the best constraints on temporal or spatial changes of fundamental constants in the early universe. An important systematic that has never before been quantified concerns model non-uniqueness. The absorption structure is generally complicated, comprising many blended lines. This characteristic means any given system can be fitted equally well by many slightly different models, each having a different value of α, the fine structure constant. We use AI Monte Carlo modelling to quantify non-uniqueness. Extensive supercomputer calculatio…
We assess the effect of a population of high-redshift quasars on the 21-cm power spectrum during the epoch of reionisation. Our approach is to implement a semi-numerical scheme to calculate the three-dimensional structure of ionised regions surrounding massive halos at high redshift. We include the ionising influence of luminous quasars by populating a simulated overdensity field with quasars using a Monte Carlo Markov Chain algorithm. We find that quasars modify both the amplitude and shape of the power spectrum at a level which is of the same order as the fractional contribution to reionisat…
We present spectroscopic analysis of the broad absorption line outflow in quasar SDSS J1512+1119. In particular, we focus our attention on a kinematic component in which we identify PV and SIV/SIV* absorption troughs. The shape of the unblended phosphorus doublet troughs and the three SIV/SIV* troughs allow us to obtain reliable column density measurements for these two ions. Photoionization modelling using these column densities and those of HeI* constrain the abundance of phosphorus to the range of 0.5-4 times the solar value. The total column density, ionization parameter and metalicity inf…
Strongly lensed explosive transients such as supernovae, gamma-ray bursts, fast radio bursts, and gravitational waves are very promising tools to determine the Hubble constant ($H_0$) in the near future in addition to strongly lensed quasars. In this work, we show that the transient nature of the point source provides an advantage over quasars: the lensed host galaxy can be observed before or after the transient's appearance. Therefore, the lens model can be derived from images free of contamination from bright point sources. We quantify this advantage by comparing the precision of a lens mode…
We present a blind time-delay strong lensing (TDSL) cosmographic analysis of the doubly imaged quasar SDSS 1206+4332. We combine the relative time delay between the quasar images, Hubble Space Telescope imaging, the Keck stellar velocity dispersion of the lensing galaxy, and wide-field photometric and spectroscopic data of the field to constrain two angular diameter distance relations. The combined analysis is performed by forward modelling the individual data sets through a Bayesian hierarchical framework, and it is kept blind until the very end to prevent experimenter bias. After unblinding,…
TDCOSMO. XXIII. Measurement of the Hubble constant from the doubly lensed quasar HE1104-1805
The University of Tokyo（东京大学）；Ecole Polytechnique Fédérale de Lausanne (EPFL)（洛桑联邦理工学院）；Universitat de Barcelona (IEEC-UB)（巴塞罗那大学）；Institució Catalana de Recerca i Estudis Avançats (ICREA)（加泰罗尼亚高级研究学院）；UC Davis（加州大学戴维斯分校）；Technical University of Munich（慕尼黑工业大学）；Max-Planck-Institut für Astrophysik（马克斯·普朗克天体物理学研究所）；ETH Zurich（苏黎世联邦理工学院）；Liège Université（列日大学）；University of California, Los Angeles（加州大学洛杉矶分校）；Stony Brook University（石溪大学）；Fermi National Accelerator Laboratory（费米国家加速器实验室）
本文利用双镜像类星体HE1104-1805测量哈勃常数，通过结合多 telescope 数据测量时间延迟、恒星速度弥散、费马势差和收敛，采用幂律质量模型得出H_0=64.2±5.8xλ_int km s⁻¹ Mpc⁻¹。
In the era of synoptic surveys, the number of known gravitationally lensed quasars is set to increase by over an order of magnitude. These new discoveries will enable a move from single-quasar studies to investigations of statistical samples, presenting new opportunities to test theoretical models for the structure of quasar accretion discs and broad emission line regions (BELRs). As one crucial step in preparing for this influx of new lensed systems, a large-scale exploration of microlensing convergence-shear parameter space is warranted, requiring the computation of O(10^5) high resolution m…
The thermal state of the intergalactic medium (IGM) provides an indirect probe of both the HI and HeII reionisation epochs. Current constraints on the IGM temperature from the Lya forest are restricted to the redshift range 2<z<4.5, limiting the ability to probe the thermal memory of HI reionisation toward higher redshift. In this work, we present the first direct measurement of the IGM temperature around a z=6 quasar by analysing the Doppler widths of Lya absorption lines in the proximity zone of SDSS J0818+1722. We use a high resolution (R= 40000) Keck/HIRES spectrum in combination with deta…
We wish to study the extent and subparsec scale spatial structure of intervening quasar absorbers, mainly those involving neutral and molecular gas. We have selected quasar absorption systems with high spectral resolution and good S/N data, with some of their lines falling on quasar emission features. By investigating the consistency of absorption profiles seen for lines formed either against the quasar continuum source or on the much more extended emission line region (ELR), we can probe the extent and structure of the foreground absorber over the extent of the ELR (0.3-1 pc). The spatial cov…
Global VLBI (EVN+VLBA) polarization observations at 5 and 8.4 GHz of ten high redshift (z > 3) quasars are presented. The core and jet brightness temperatures are found through modelling the self-calibrated uv-data with Gaussian components, which provide reliable estimates of the flux density and size of individual components. The observed high core brightness temperatures (median $T_{\rm b,\,core}=4\times10^{11}$ K) are consistent with Doppler boosted emission from a relativistic jet orientated close to the line-of-sight. This can also explain the dramatic jet bends observed for some of our s…
We present the catalogue of the Mg II absorption systems detected at a high significance level using an automated search algorithm in the spectra of quasars from the twelfth data release of the Sloan Digital Sky Survey. A total of 266,433 background quasars were searched for the presence of absorption systems in their spectra. The continuum modelling for the quasar spectra was performed using a mean filter. A pseudo-continuum derived using a median filter was used to trace the emission lines. The absorption system catalogue contains 39,694 Mg II systems detected at a 6.0, 3.0$σ$ level respecti…
We present measurements of the ionising ultraviolet background (UVB) at z ~ 5-6 using the quasar proximity effect. The fifteen quasars in our sample cover the range 4.6 < z_q < 6.4, enabling the first proximity effect measurements of the UVB at z > 5. The metagalactic hydrogen ionisation rate, Gamma_bkg, was determined by modelling the combined ionisation field from the quasar and the UVB in the proximity zone on a pixel-by-pixel basis. The optical depths in the spectra were corrected for the expected effect of the quasar until the mean flux in the proximity region equalled that in the average…
