The upcoming WEAVE-QSO survey will target a high density of quasars over a large area, enabling the reconstruction of the 3D density field through Lyman-$α$ tomography over unprecedented volumes smoothed on intermediate scales ($\approx$ 16 Mpc/$h$). We produce mocks of the Lyman-$α$ forest using LyMAS, and reconstruct the 3D density field between sightlines through Wiener filtering in a configuration compatible with the future WEAVE-QSO observations. The fidelity of the reconstruction is assessed by measuring one- and two-point statistics from the distribution of critical points in the cosmic web. In addition, initial Lagrangian statistics are predicted from first principles, and measurements of the connectivity of the cosmic web are performed. The reconstruction captures well the expected features in the auto- and cross-correlations of the critical points. This remains true after a realistic noise is added to the synthetic spectra, even though sparsity of sightlines introduces systematics, especially in the cross-correlations of points with mixed signature. Specifically, for walls and filaments, the most striking clustering features could be measured with up to 4 sigma of significance with a WEAVE-QSO-like survey. Moreover, the connectivity of each peak identified in the reconstructed field is globally consistent with its counterpart in the original field, indicating that the reconstruction preserves the geometry of the density field not only statistically, but also locally. Hence the critical points relative positions within the tomographic reconstruction could be used as standard rulers for dark energy by WEAVE-QSO and similar surveys.
In these proceedings we describe the WEAVE-QSO survey, which will observe around 400,000 high redshift quasars starting in 2018. This survey is part of a broader WEAVE survey to be conducted at the 4.2m William Herschel Telescope. We will focus on chiefly on the science goals, but will also briefly summarise the target selection methods anticipated and the expected survey plan. Understanding the apparent acceleration in the expansion of the Universe is one of the key scientific challenges of our time. Many experiments have been proposed to study this expansion, using a variety of techniques. H…
Forecast for the detectability of patchy hydrogen reionization in WEAVE-QSO measurements of the Lyman-$α$ forest power spectrum at redshift $z \geq 4$
The University of Nottingham（诺丁汉大学）；University of Hertfordshire（赫特福德大学）；Indian Institute of Technology Indore（印度理工学院印多尔分校）；Aix Marseille Université（艾克斯-马赛大学）；Università degli Studi di Milano-Bicocca（米兰比可卡大学）；Camosun College（卡莫森学院）；IUCAA（印度天体物理与宇宙学研究与教学中心）；INAF - Osservatorio Astronomico di Brera（意大利国家天体物理研究所布拉耶天文台）
Measurements of QSO clustering in the SDSS show that $\mathrm{z}>4$ QSOs are some of the most highly biased objects in the universe. Their large correlation lengths of $r_0 \sim 20h^{-1}$Mpc are comparable to the most massive clusters of galaxies in the universe today and suggest that these QSOs may mark the locations of massive cluster progenitors at high redshift. We report the discovery of an overdensity of LBGs around QSO SDSSJ114514.18+394715.9 as part of our survey to identify Lyman-Break galaxies (LBGs) around luminous $\mathrm{z}\sim4$ QSOs. In this field three of the eight LBGs with s…
We utilize the Multi Unit Spectroscopic Explorer (MUSE) on the Very Large Telescope (VLT) to search for extended Lyman-Alpha emission around the z~6.6 QSO J0305-3150. After carefully subtracting the point-spread-function, we reach a nominal 5-sigma surface brightness limit of SB = 1.9x10$^{-18}$ erg/s/cm$^2$/arcsec$^2$ over a 1 arcsec$^2$ aperture, collapsing 5 wavelength slices centered at the expected location of the redshifted Lyman-Alpha emission (i.e. at 9256 Ang.). Current data suggest the presence (5-sigma, accounting for systematics) of a Lyman-Alpha nebula that extends for 9 kpc aroun…
The spectrum of cosmic ultraviolet background radiation at He II ionizing energies (E > 4 Ryd) is important to study the He II reionization, thermal history of the intergalactic medium (IGM) and metal lines observed in QSO absorption spectra. It is determined by the emissivity of QSOs at E > 4 Ryd obtained from their observed luminosity functions and the mean spectral energy distribution (SED). The SED is approximated as a power-law at energies E > 1 Ryd, $f_E \propto E^α$, where the existing observations constrain the power-law index $α$ only up to ~2.3 Ryd. Here, we constrain $α$ for E > 4 R…
In this third paper in a series on the nature of extended, asymmetric Lyman alpha emitters at z ~ 3 we report the discovery, in an ultra-deep, blind, spectroscopic long-slit survey, of a Lyman alpha emitting halo around a QSO at redshift 3.045. The QSO is a previously known, obscured AGN. The halo appears extended along the direction of the slit and exhibits two faint patches separated by 17 proper kpc in projection from the QSO. Comparison of the 2-dimensional spectrum with archival HST ACS images shows that these patches coincide spatially with emission from a peculiar, dumbbell-shaped, fain…
Lyman-alpha forest data probing the post-reionization Universe shows surprisingly large opacity fluctuations over rather large ($\ge$50 comoving Mpc/h) spatial scales. We model these fluctuations using a hybrid approach utilizing the large volume Millennium simulation to predict the spatial distribution of QSOs combined with smaller scale full hydrodynamical simulation performed with RAMSES and post-processed with the radiative transfer code ATON. We produce realictic mock absorption spectra that account for the contribution of galaxies and QSOs to the ionising UV background. This improved mod…
We report long-slit spectroscopic observations of the quasar SDSS J082303.22+052907.6 ($z_{\rm CIV}$$\sim$3.1875), whose Broad Line Region (BLR) is partly eclipsed by a strong damped Lyman-$α$ (DLA; log$N$(HI)=21.7) cloud. This allows us to study the Narrow Line Region (NLR) of the quasar and the Lyman-$α$ emission from the host galaxy. Using CLOUDY models that explain the presence of strong NV and PV absorption together with the detection of SiII$^*$ and OI$^{**}$ absorption in the DLA, we show that the density and the distance of the cloud to the quasar are in the ranges 180 $<$ $n_{\rm H}$ …
We present the first lensing total mass estimate of a galaxy, at redshift 2.207, that acts as a gravitational deflector and damped Lyman-alpha absorber on the background QSO SDSS J1135-0010, at redshift 2.888. The remarkably small projected distance, or impact parameter, between the lens and the source has been estimated to be 0.8 +/- 0.1 kpc in a recent work. By exploiting the Sloan Digital Sky Survey database, we establish a likely lensing magnification signal in the photometry of the QSO. This is determined to be 2.2 mag brighter (or 8 times more luminous) than the median QSO at comparable …
We introduce a new method for determining the influence of galaxies and active galactic nuclei (AGN) on the physical state of the intergalactic medium (IGM) at high redshift and illustrate its potential via a first application to the field of the $z=6.42$ QSO J1148+5251. By correlating the spatial positions of spectroscopically-confirmed Lyman break galaxies (LBGs) with fluctuations in the Lyman alpha forest seen in the high signal-to-noise spectrum of a background QSO, we provide a statistical measure of the typical escape fraction of Lyman continuum photons close to the end of cosmic reionis…
We present the elemental abundance and H2 content measurements of a Damped Lyman-α (DLA) system with an extremely large H i column density, log N(H i) (cm-2) = 22.0+/-0.10, at zabs = 3.287 towards the QSO SDSS J 081634+144612. We measure column densities of H2, C i, C i^*, Zn ii, Fe ii, Cr ii, Ni ii and Si ii from a high signal-to-noise and high spectral resolution VLT-UVES spectrum. The overall metallicity of the system is [Zn/H] = -1.10 +/- 0.10 relative to solar. Two molecular hydrogen absorption components are seen at z = 3.28667 and 3.28742 (a velocity separation of \approx 52 km s-1) in …
Composite spectra of 85 proximate absorbers (log N(HI)>20 and velocity difference between the absorption and emission redshift, dv<10,000 km/s) in the SDSS are used to investigate the trends of metal line strengths with velocity separation from the QSO. We construct composites in 3 velocity bins: dv<3000 km/s, 3000<dv<6000 km/s and dv>6000 km/s, with further sub-samples to investigate the metal line dependence on N(HI) and QSO luminosity. Low (e.g. SiII and FeII) and high ionization (e.g. SiIV and CIV) species alike have equivalent widths (EWs) that are larger by factors of 1.5 -- 3 in the dv<…
We report the discovery of a "super-damped" Lyman-alpha absorber at $z_{abs}=2.2068$ toward QSO Q1135-0010 in the Sloan Digital Sky Survey, and follow-up VLT UVES spectroscopy. Voigt profile fit to the DLA line indicates log $N_{\rm H I} = 22.05 \pm 0.1$. This is the second QSO DLA discovered to date with such high $N_{\rm H I}$. We derive element abundances [Si/H] = $-1.10 \pm 0.10$, [Zn/H] = $-1.06 \pm 0.10$, [Cr/H] = $-1.55 \pm 0.10$, [Ni/H] = $-1.60 \pm 0.10$, [Fe/H] = $-1.76 \pm 0.10$, [Ti/H] = $-1.69 \pm 0.11$, [P/H] = $-0.93 \pm 0.23$, and [Cu/H] = $-0.75 \pm 0.14$. Our data indicate de…
We present the results of a survey for damped (DLA, log N(H I) > 20.3) and sub-damped Lyman-? systems (19.5 < log N(H I) < 20.3) at z > 2.55 along the lines-of-sight to 77 quasars with emission redshifts in the range 4 < zem < 6.3. Intermediate resolution (R ? 4300) spectra have been obtained with the Echellette Spectrograph and Imager (ESI) mounted on the Keck telescope. A total of 100 systems with log N(H I) > 19.5 are detected of which 40 systems are damped Lyman-? systems for an absorption length of ?X = 378. About half of the lines of sight of this homogeneous survey have never been inves…
In recent years, the autocorrelation of the hydrogen Lyman-α forest has been used to observe the baryon acoustic peak at redshift 2 < z < 3.5 using tens of thousands of QSO spectra from the BOSS survey. However, the interstellar medium of the Milky-Way introduces absorption lines into the spectrum of any extragalactic source. These lines, while weak and undetectable in a single BOSS spectrum, could potentially bias the cosmological signal. In order to examine this, we generate absorption line maps by stacking over a million spectra of galaxies and QSOs. We find that the systematics introduced …
The variation of the dimensionless fundamental physical constant mu = m_p/m_e (the proton to electron mass ratio) can be constrained via observation of Lyman and Werner lines of molecular hydrogen in the spectra of damped Lyman alpha systems (DLAs) in the line of sight to distant QSOs. Drawing on VLT-UVES high resolution data sets of QSO 0347-383 and its DLA obtained in 2009 our analysis yields dmu/mu = (4.3 +/- 7.2) * 10^-6 at z_abs =3.025. We apply corrections for the observed offsets between discrete spectra and for the first time we find indications for inter-order distortions. Current ana…
We present a theoretical estimate for a new observable: the cross-correlation between the Lyman-alpha flux fluctuations in quasar (QSO) spectra and the convergence of the cosmic microwave background (CMB) as measured along the same line-of-sight. As a first step toward the assessment of its detectability, we estimate the signal-to-noise ratio using linear theory. Although the signal-to-noise is small for a single line-of-sight and peaks at somewhat smaller redshifts than those probed by the Lyman-alpha forest, we estimate a total signal-to-noise of 9 for cross-correlating QSO spectra of SDSS-I…
The nature of the galaxies that give rise to absorption lines, such as damped Lyman-alpha systems (DLAs) or strong MgII lines, in quasar spectra is difficult to investigate in emission. Taking advantage of the total absorption of the QSO light bluewards of the Lyman limit of two DLAs at z>3.4, we look for the continuum emission from intervening galaxies at z~2 that are identified via strong metal absorption lines. The MgII absorbers have equivalent width large enough to be potential DLA systems. Deep images are obtained with the FOcal Reducer and Spectrograph (FORS1) on the Very Large Telescop…
To search for low-redshift damped Lyman-alpha (DLA) and sub-DLA quasar absorbers, we have conducted a 21cm absorption survey of radio-loud quasars at small impact parameters to foreground galaxies selected from the Sloan Digital Sky Survey (SDSS). Here we present the first results from this survey based on observations of SDSS J104257.58+074850.5 ($z_{QSO}$ = 2.66521), a quasar at an angular separation from a foreground galaxy ($z_{gal}$ = 0.03321) of 2.5" (1.7 kpc in projection). The foreground galaxy is a low-luminosity spiral with on-going star formation (0.004 M$_{\odot}$ yr$^{-1}$ kpc$^{-…
The gas added and removed from galaxies over cosmic time greatly affects their stellar populations and star formation rates. QSO absorption studies in close QSO/galaxy pairs create a unique opportunity to study the physical conditions and kinematics of this gas. Here we present new Hubble Space Telescope (HST) images of the QSO/galaxy pair 3C 232/NGC 3067. The quasar spectrum contains a Lyman-limit absorption system (LLS) due to NGC 3067 at cz = 1421 km/s that is associated with the nearby SAB galaxy NGC 3067. Previous work identifies this absorber as a high-velocity cloud (HVC) in NGC 3067 bu…
Motivated by the anomalous dust-to-metal ratios derived in the literature for gamma-ray burst (GRB) damped Lyman-alpha absorbers (DLAs), we measure these ratios using the dust-depletion pattern observed in UV/optical afterglow spectra associated with the ISM at the GRB host-galaxy redshifts. Our sample consists of 20 GRB absorbers and a comparison sample of 72 QSO-DLAs with redshift 1.2 < z < 4.0 and down to Z = 0.002 Z_Sol metallicities. The dust-to-metal ratio in QSO- and GRB-DLAs increases both with metallicity and metal column density, spanning ~10--110% of the Galactic value and pointing …
We report on the first Cosmic Origins Spectrograph (COS) observations of damped and sub-damped Lyman-alpha (DLA) systems discovered in a new survey of the gaseous halos of low-redshift galaxies. From observations of 37 sightlines, we have discovered three DLAs and four sub-DLAs. We measure the neutral gas density Omega(HI), and redshift density dN/dz, of DLA and sub-DLA systems at z<0.35. We find dN/dz=0.25 and Omega(HI)=1.4x10^-3 for DLAs, and dN/dz=0.08 with Omega(HI)=4.2x10^-5 for sub-DLAs over a redshift path delta z=11.9. To demonstrate the scientific potential of such systems, we present…
We constrain the H I photoionization rate $(Γ_{\rm HI})$ at $z \lesssim 0.45$ by comparing the flux probability distribution function and power spectrum of the Ly-$α$ forest data along 82 QSO sightlines obtained using Cosmic Origins Spectrograph with models generated from smoothed particle hydrodynamic simulations. We have developed a module named "Code for Ionization and Temperature Evolution (CITE)" for calculating the intergalactic medium (IGM) temperature evolution from high to low redshifts by post-processing the GADGET-2 simulation outputs. Our method, that produces results consistent wi…
We study the effect of the non-Gaussianity induced by gravitational evolution upon the statistical properties of absorption in quasar (QSO) spectra. Using the generic hierarchical ansatz and the lognormal approximation we derive the analytical expressions for the one-point PDF as well as for the joint two-point probability distribution (2PDF) of transmitted fluxes in two neighbouring QSOs. These flux PDFs are constructed in 3D as well as in projection (i.e. in 2D). The PDFs are constructed by relating the lower-order moments, i.e. cumulants and cumulant correlators, of the fluxes to the 3D neu…
We have serendipitously detected a strong O VI-bearing Lyman limit system at z_abs = 0.3558 toward the QSO J1009+0713 (z_em = 0.456) in our survey of low-redshift galaxy halos with the Hubble Space Telescope's Cosmic Origins Spectrograph. Its rest-frame equivalent width of W_r = 835 +/- 49 mA is the highest for an intervening absorber yet detected in any low-redshift QSO sightline, with absorption spanning 400 km s^-1 in its rest frame. HST/WFC3 images of the galaxy field show that the absorber is associated with two galaxies lying at 14 and 46 kpc from the QSO line of sight. The bulk of the a…
We present VLT/UVES spectroscopy of the quasar Q0841+129, whose spectrum shows a proximate damped Lyman-alpha (PDLA) absorber at z=2.47621 and a proximate sub-DLA at z=2.50620, both lying close in redshift to the QSO itself at z_em=2.49510+/-0.00003. This fortuitous arrangement, with the sub-DLA acting as a filter that hardens the QSO's ionizing radiation field, allows us to model the ionization level in the foreground PDLA, and provides an interesting case-study on the origin of the high-ion absorption lines Si IV, C IV, and O VI in DLAs. The high ions in the PDLA show at least five component…
We present high resolution echelle spectra of 7 proximate damped Lyman alpha (PDLA) systems whose relative velocity separation from the background quasar is Delta V < 3000 km/s. Combining our sample with a further 9 PDLAs from the literature we compare the chemical properties of the proximate systems with a control sample of intervening DLAs. Taken at face value, the sample of 16 PDLAs exhibits a wide range of metallicities, ranging from Z ~ 1/3 Z_sun down to Z ~ 1/1000 Z_sun, including the DLA with the lowest N(SiII)/N(HI) yet reported in the literature. We find several pieces of evidence tha…
Visualizing the high-redshift Universe is difficult due to the dearth of available data; however, the Lyman-alpha forest provides a means to map the intergalactic medium at redshifts not accessible to large galaxy surveys. Large-scale structure surveys, such as the Baryon Oscillation Spectroscopic Survey (BOSS), have collected quasar (QSO) spectra that enable the reconstruction of HI density fluctuations. The data fall on a collection of lines defined by the lines-of-sight (LOS) of the QSO, and a major issue with producing a 3D reconstruction is determining how to model the regions between the…
