Search

We have searched high spectral resolution spectra of quasars known to exhibit high redshift (z > 1.7) intervening H2-bearing damped Lyman-α (DLA) systems for partial coverage of the quasar emission by intervening H2 clouds. Partial coverage manifests itself by the presence of non-zero residual flux in the core of saturated H2 absorption lines. The residual flux can be observed either only at the bottom of absorption lines redshifted on top of quasar emission lines, in which case part of the broad line region (BLR) is not covered, or in all absorption lines, in case some continuum source is not covered. Among 35 H2 absorption clouds in 14 quasar spectra obtained with the VLT-UVES or Keck-HIRES spectrographs, we detect partial coverage of the BLR for 13 clouds. This result suggests that the probability of partial coverage of the QSO BLR by a distant H2 absorption cloud is about 40 per cent. For four systems towards Q 0013−0029, Q 0405−4418, Q 0812+3208, and J 2100−0641, partial coverage is detected for the first time. We determine the theoretical probability of partial coverage of the BLR by a distant H2 cloud as a function of the ratio between the cloud and the BLR sizes. Using this model, we obtain an estimate of the characteristic BLR radius of |$50^{+19}_{-23}\,\rm{light \,days}$|⁠. This is similar to the estimate of the BLR size obtained by reverberation-mapping analysis |$({\sim}100\,\rm{light\, days})$|⁠. [ABSTRACT FROM AUTHOR]

We present the results of our automatic search for proximate damped Ly α absorption (PDLA) systems in the quasar spectra fromthe Sloan Digital Sky Survey Data Release 12. We constrain our search to those PDLAs lying within 1500 kms-1 from the quasar to make sure that the broad DLA absorption trough masks most of the strong Ly α emission from the broad-line region (BLR) of the quasar. When the Ly α emission from the BLR is blocked by these so-called eclipsing DLAs, narrow Ly α emission from the host galaxy could be revealed as a narrow emission line (NEL) in the DLA trough. We define a statistical sample of 399 eclipsing DLAs with log N(HI) ≥ 21.10. We divide our statistical sample into three subsamples based on the strength of theNEL detected in the DLA trough. By studying the stacked spectra of these subsamples, we found that absorptions from high ionization species are stronger in DLAs with stronger NEL in their absorption core.Moreover, absorption from the excited states of species like SiII are also stronger in DLAs with stronger NEL. We also found no correlation between the luminosity of the Ly α NEL and the quasar luminosity. These observations are consistent with a scenario in which the DLAs with stronger NEL are denser and physically closer to the quasar.We propose that these eclipsing DLAs could be the product of the interaction between infalling and outflowing gas. High-resolution spectroscopic observation would be needed to shed some light on the nature of these eclipsing DLAs. [ABSTRACT FROM AUTHOR]

We probe the small-scale absorption line variability using absorption depth based analysis of a sample of 64 ultra-fast outflow (UFO) C  iv broad absorption line (BAL) quasars monitored using the Southern African Large Telescope. We confirm the strong monotonic increase in the strength of variability with increasing outflow velocity. We identify regions inside the BAL trough for each source where the normalized flux difference between two epochs is >0.1 for a velocity width ≥500 km s−1 (called 'variable regions'). We find that the total number of variable regions increases with the time interval probed and the number of BALs showing variable regions almost doubles from short (<2 yr) to long (>2 yr) time-scales. We study the distributions of variable region properties such as its velocity width, depth, and location. These regions typically occupy a few-tenths of the entire width of the BAL. Their widths are found to increase with increasing time-scales having typical widths of ∼2000 km s−1 for Δ t > 2 yr. However, their absolute velocity with respect to z em and their relative position within the BAL profile remain random irrespective of the time-scale probed. The equivalent width variations of the BALs are strongly dependent on the size and depth of the variable regions but are little dependent on their total number. Finally, we find that ∼17 per cent of the UFO BALs show uncorrelated variability within the BAL trough. [ABSTRACT FROM AUTHOR]

We report the discovery of the first ‘ghostly’ damped Ly α absorption system (DLA), which is identified by the presence of absorption from strong low-ion species at zabs = 1.704 65 along the line of sight to the quasar SDSS J113341.29−005740.0 with zem = 1.704 41. No Ly α absorption trough is seen associated with these absorptions because the DLA trough is filled with the leaked emission from the broad emission-line region of the quasar. By modelling the quasar spectrum and analysing the metal lines, we derive log N(H i)(cm−2) ∼21.0 ± 0.3. The DLA cloud is small (≤0.32 pc), thus not covering entirely the broad-line region and is located at ≥39 pc from the central active galactic nucleus (AGN). Although the DLA is slightly redshifted relative to the quasar, its metallicity ([S/H] = −0.41 ± 0.30) is intermediate between what is expected from infalling and outflowing gas. It could be possible that the DLA is part of some infalling material accreting on to the quasar host galaxy through filaments, and that its metallicity is raised by mixing with the enriched outflowing gas emanating from the central AGN. Current DLA surveys miss these ‘ghostly’ DLAs, and it would be important to quantify the statistics of this population by searching the Sloan Digital Sky Survey (SDSS) data base using metal absorption templates. [ABSTRACT FROM AUTHOR]

We review the uncertainties in high-z star-formation rate (SFR) measures and the constraints that one obtains from high-z gamma-ray burst (GRB) rates on them. We show that at the present time, the GRB rates per unit star-formation at $z>3$ are higher than at lower redshift. There could be a multitude of reasons for this: a stellar metallicity bias for GRB production, a top-heavy initial mass function (IMF) and/or missing a significant fraction of star-formation in field galaxy surveys due to incompleteness, surface brightness limitations and cosmic variance. We also compare metallicity predictions made using a hierarchical model of cosmic chemical evolution based on two recently proposed SFRs, one based on the observed galaxy luminosity function at high redshift and one based on the GRB rate and find that within the considerable scatter in metal abundance measures, they both are consistent with the data. Analyzing the ensemble of different measurements together, we conclude that despite metallicity biases, GRBs may be a less biased probe of star-formation at $z>3$ than at $z<2$ . There is likely to be a common origin to the high GRB rate per unit star-formation and the high observed Lyman-continuum production rate in high redshift galaxies and that this may be due to a relative overabundance of stars with mass ${>}25~\mbox{M}_{\odot }$ which are likely GRB progenitors. We also find that to reconcile these measurements with the Thomson scattering cross section of cosmic microwave background (CMB) photons measured by Planck, the escape fraction of Lyman-continuum photons from galaxies must be low, about ∼15 % or less and that the clumping factor of the IGM is likely to be small, ∼3. Finally, we demonstrate that GRBs are unique probes of metallicity evolution in low-mass galaxy samples and that GRB hosts likely lost a significant fraction of metals to the intergalactic medium (IGM) due to feedback processes such as stellar winds and supernovae. [ABSTRACT FROM AUTHOR]

We present spectroscopic observations of six high redshift (zem > 2) quasars, which have been selected for their Lyman α (Lyα) emission region being only partially covered by a strong proximate (zabs ~ zem) coronagraphic damped Lyα system (DLA). We detected spatially extended Lyα emission envelopes surrounding these six quasars, with projected spatial extent in the range 26 ≤ dLyα ≤ 51 kpc. No correlation is found between the quasar ionizing luminosity and the Lyα luminosity of their extended envelopes. This could be related to the limited covering factor of the extended gas and/or due to the AGN being obscured in other directions than towards the observer. Indeed, we find a strong correlation between the luminosity of the envelope and its spatial extent, which suggests that the envelopes are probably ionized by the AGN. The metallicity of the coronagraphic DLAs is low and varies in the range -1.75 < [Si/H] < -0.63. Highly ionized gas is observed to be associated with most of these DLAs, probably indicating ionization by the central AGN. One of these DLAs has the highest Aliii/Siii ratio ever reported for any intervening and/or proximate DLA. Most of these DLAs are redshifted with respect to the quasar, implying that they might represent infalling gas probably accreted on to the quasar host galaxies through filaments. [ABSTRACT FROM AUTHOR]

We report long-slit spectroscopic observations of the quasar SDSS J082303.22+052907.6 (zCIV ~ 3.1875), whose broad-line region (BLR) is partly eclipsed by a strong damped Lyman α (DLA; logN(H I) = 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 N V and P V absorption together with the detection of Si II* and O I** absorption in the DLA, we show that the density and the distance of the cloud to the quasar are in the ranges 180 < nH < 710 cm-3 and 580 > r0 > 230 pc, respectively. Sizes of the neutral (~2-9pc) and highly ionized phases (~3-80pc) are consistent with the partial coverage of the C IV BLR by the C IV absorption from the DLA (covering factor of ~0.85). We show that the residuals are consistent with emission from the NLR with C IV/Lyman α ratios varying from 0 to 0.29 through the profile. Remarkably, we detect extended Lyman α emission up to 25 kpc to the north and west directions and 15 kpc to the south and east. We interpret the emission as the superposition of strong emission in the plane of the galaxy up to 10 kpc with emission in a wind of projected velocity ~500 km s-1 which is seen up to 25 kpc. The low metallicity of the DLA (0.27 solar) argues for at least part of this gas being infalling towards the active galactic nucleus and possibly being located where accretion from cold streams ends up. [ABSTRACT FROM AUTHOR]

We study the H2 molecular content in high redshift damped Lyman-alpha systems (DLAs) as a function of the Hı column density. We find a significant increase of the H2 molecular content around log N(Hı) (cm-2)~21.5-22, a regime unprobed until now in intervening DLAs, beyond which the majority of systems have log N(H2) > 17. This is in contrast with lines of sight towards nearby stars, where such H2 column densities are always detected as soon as log N(HI)>20.7. This can qualitatively be explained by the lower average metallicity and possibly higher surrounding UV radiation in DLAs. However, unlike in the Milky Way, the overall molecular fractions remain modest, showing that even at a large N(Hı) only a small fraction of overall Hı is actually associated with the self-shielded H2 gas. Damped Lyman-alpha systems with very high-N(Hı) probably arise along quasar lines of sight passing closer to the centre of the host galaxy where the gas pressure is higher. We show that the colour changes induced on the background quasar by continuum (dust) and line absorption (Hı Lyman and H2 Lyman & Werner bands) in DLAs with log N(Hı)~22 and metallicity ~1/10 solar is significant, but not responsible for the long-discussed lack of such systems in optically selected samples. Instead, these systems are likely to be found towards intrinsically fainter quasars that dominate the quasar luminosity function. Colour biasing should in turn be severe at higher metallicities. [ABSTRACT FROM AUTHOR]

We study the time variability (over ≤7.3 yr) of ultra fast outflows (UFOs) detected in a sample of 64 C iv broad absorption line (BAL) quasars (with 80 distinct BAL components) monitored using the Southern African Large Telescope. By comparing the properties of the quasar in our sample with those of a control sample of non-BAL quasars, we show that the distributions of black hole mass are different and the bolometric luminosities and optical photometric variations of UFO BAL quasars are slightly smaller compared to that of non-BAL quasars. The detection fraction of C  iv equivalent width (W) variability (∼95 per cent), the fractional variability amplitude |$\left(\frac{\Delta W}{W}\right)$| and the fraction of 'highly variable' BAL (i.e. |$\big|$| |$\frac{\Delta W}{W}$| |$\big|$| > 0.67) components (∼33 per cent) are higher in our sample compared to the general BAL population. The scatter in |$\frac{\Delta W}{W}$| and the fraction of 'highly variable' BALs increase with the time-scale probed. The |$\frac{\Delta W}{W}$| distribution is asymmetric at large time scales. We attribute this to the BAL strengthening time-scales being shorter than the weakening time-scales. The BAL variability amplitude correlates strongly with the BAL properties compared to the quasar properties. BALs with low W, high-velocity, shallow profiles, and low-velocity width tend to show more variability. When multiple BAL components are present, a correlated variability is seen between low- and high-velocity components with the latter showing a larger amplitude variations. We find an anticorrelation between the fractional variations in the continuum flux and W. While this suggests photoionization induced variability, the scatter in continuum flux is much smaller than that of W. [ABSTRACT FROM AUTHOR]

We present the Data Release 9 Quasar (DR9Q) catalog from the Baryon Oscillation Spectroscopic Survey (BOSS) of the Sloan Digital Sky Survey III. The catalog includes all BOSS objects that were targeted as quasar candidates during the survey, are spectrocopically confirmed as quasars via visual inspection, have luminosities Mi[z = 2] < -20.5 (in a ΛCDM cosmology with H0 = 70 km s-1 Mpc-1, ΩM = 0.3, and ΩΛ = 0.7) and either display at least one emission line with full width at half maximum (FWHM) larger than 500 km s-1 or, if not, have interesting/complex absorption features. It includes as well, known quasars (mostly from SDSS-I and II) that were reobserved by BOSS. This catalog contains 87 822 quasars (78 086 are new discoveries) detected over 3275 deg2 with robust identification and redshift measured by a combination of principal component eigenspectra newly derived from a training set of 8632 spectra from SDSS-DR7. The number of quasars with z > 2.15 (61 931) is ∼2.8 times larger than the number of z > 2.15 quasars previously known. Redshifts and FWHMs are provided for the strongest emission lines (C Iv, C III], Mg II). The catalog identifies 7533 broad absorption line quasars and gives their characteristics. For each object the catalog presents five-band (u, g, r, i, z) CCD-based photometry with typical accuracy of 0.03 mag, and information on the morphology and selection method. The catalog also contains X-ray, ultraviolet, near-infrared, and radio emission properties of the quasars, when available, from other large-area surveys. The calibrated digital spectra cover the wavelength region 3600-10 500 Å at a spectral resolution in the range 1300 < R < 2500; the spectra can be retrieved from the SDSS Catalog Archive Server. We also provide a supplemental list of an additional 949 quasars that have been identified, among galaxy targets of the BOSS or among quasar targets after DR9 was frozen [ABSTRACT FROM AUTHOR]

ABSTRACT We present a detailed analysis of the partial coverage of the Q1232+082 ( zem= 2.57) broad-line region (BLR) by an intervening H2-bearing cloud at zabs= 2.3377. Using curve of growth analysis and line profile fitting, we demonstrate that the H2-bearing component of the cloud covers the quasi-stellar object (QSO) intrinsic continuum source completely but only part of the BLR. We find that only 48 ± 6 per cent of the C iv BLR emission is covered by the C i absorbing gas. We observe residual light (∼6 per cent) as well in the bottom of the O i λ1302 absorption from the cloud, redshifted on top of the QSO Lyman α emission line. Therefore, the extent of the neutral phase of the absorbing cloud is not large enough to cover all of the background source. The most likely explanation for this partial coverage is the small size of the intervening cloud, which is comparable to the BLR size. We estimate the number densities in the cloud: ∼ 110 cm−3 for the H2-bearing core and nH∼ 30 cm−3 for the neutral envelope. Given the column densities, N(H2) = 3.71 ± 0.97 × 1019 cm−2 and N(H i) = 7.94 ± 1.6 × 1020 cm−2, we derive the linear size of the H2-bearing core and the neutral envelope along the line of sight to be ∼ 0.15+0.05−0.05 pc and ∼ 8.2+6.5−4.1 pc, respectively. We estimate the size of the C iv BLR by two ways: (i) extrapolating size-luminosity relations derived from reverberation observations and (ii) assuming that the H2-bearing core and the BLR are spherical in shape and the results are ∼0.26 and ∼0.18 pc, respectively. The large size we derive for the extent of the neutral phase of the absorbing cloud together with a covering factor of ∼0.94 of the Lyman α emission means that the Lyman α BLR is probably fully covered but that the Lyman α emission extends well beyond the limits of the BLR. [ABSTRACT FROM AUTHOR]

In recent years, the Lyman- α forest in quasar spectra has been used, together with N-body simulations, to determine the underlying matter distribution in the intergalactic medium (IGM). One of the key parameters to be known in order to compare observations and numerical simulations is the mean HI absorption in the IGM. To derive the latter, one has first to fit the quasar continuum. We have observed 20 high redshift and highly luminous QSOs ( m ≤ 17.5 and 2.40 ≤ z ≤ 3.91) at intermediate spectral resolution, with either EMMI (ESO Multi-Mode Instrument) on the ESO-NTT telescope or CARELEC at the OHP (Observatoire de Haute-Provence), and applied different methods of determining the QSO continuum to this QSO sample. We have measured the amount of absorption, known as the flux decrement, DA, in the Lyman- α forest for these different methods and compared the results. In addition, we have compared DA values measured along the same lines of sight observed at high and intermediate spectral resolutions. We discuss the systematics resulting from the use of automatic continuum fitting methods. [ABSTRACT FROM AUTHOR]

We present a detailed analysis of the H2 and HD absorption lines detected in the damped Lyman α (DLA) system at towards the quasar Q 1232 + 082. We show that this intervening cloud has a covering factor smaller than unity and covers only part of the quasi-stellar object (QSO) broad emission-line region. The zero flux level has to be corrected at the position of the saturated H2 and optically thin HD lines by about 10 per cent. We accurately determine the Doppler parameter for HD and C i lines . We find a ratio = that is significantly higher than what is observed in molecular clouds of the Galaxy. Chemical models suggest that in the physical conditions prevailing in the central part of molecular clouds, deuterium and hydrogen are mostly in their molecular forms. Assuming this is true, we derive . This implies that the corresponding baryon density of the Universe is . This value coincides within 1σ with that derived from observations of the cosmic microwave background radiation (CMBR) as well as from observations of the D/H atomic ratio in low-metallicity QSO absorption-line systems. The observation of HD at high redshift is therefore a promising independent method to constrain Ωb. This observation indicates as well a low astration factor of deuterium. This can be interpreted as the consequence of an intense infall of primordial gas on to the associated galaxy. [ABSTRACT FROM AUTHOR]

We study the density field around quasars using high-quality medium spectral resolution Echelle Spectrograph and Imager–Keck spectra ( , signal-to-noise ratio (S/N) > 25) of 45 high-redshift quasars selected from a total of 95 spectra. This large sample considerably increases the statistics compared to previous studies. The redshift evolution of the mean photoionization rate and the median optical depth of the intergalactic medium (IGM) are derived statistically from the observed transmitted flux and the pixel optical depth probability distribution function, respectively. This is used to study the so-called proximity effect, that is, the observed decrease of the median optical depth of the IGM in the vicinity of the quasar caused by enhanced photoionization rate due to photons emitted by the quasar. We show that the proximity effect is correlated with the luminosity of the quasars, as expected. By comparing the observed decrease of the median optical depth with the theoretical expectation, we find that the optical depth does not decrease as rapidly as expected when approaching the quasar if the gas in its vicinity is part of the standard IGM. We interpret this effect as revealing gaseous overdensities on scales as large as Mpc. The mean overdensity is of the order of 2 and 5 within, respectively, 10 and Mpc. If true, this would indicate that high-redshift quasars are located in the centre of overdense regions that could evolve with time into massive clusters of galaxies. The overdensity is correlated with luminosity: brighter quasars show higher overdensities. [ABSTRACT FROM AUTHOR]

We present the transverse flux correlation function of the Lyα forest in quasar absorption spectra at from VLT-FORS and VLT-UVES observations of a total of 32 pairs of quasars; 26 pairs with separations in the range and six pairs with . Correlation is detected at the 3σ level up to separations of the order of ∼4 arcmin (or comoving at for and ). We have, furthermore, measured the longitudinal correlation function at a somewhat higher mean redshift from 20 lines of sight observed with high spectral resolution and high signal-to-noise ratio with VLT-UVES. We compare the observed transverse and longitudinal correlation functions to that obtained from numerical simulations and illustrate the effect of spectral resolution, thermal broadening and peculiar motions. The shape and correlation length of the correlation functions are in good agreement with those expected from absorption by the filamentary and sheet-like structures in the photoionized warm intergalactic medium predicted in cold dark matter (CDM)-like models for structures formation. Using a sample of 139 C iv systems detected along the lines of sight towards the pairs of quasars we also investigate the transverse correlation of metals on the same scales. The observed transverse correlation function of intervening C iv absorption systems is consistent with that of a randomly distributed population of absorbers. This is likely due to the small number of pairs with separation less than 2 arcmin. We detect, however, a significant overdensity of systems in the sightlines towards the quartet Q 0103−294A&B, Q 0102−2931 and Q 0102−293 which extends over the redshift range and an angular scale larger than 10 arcmin. [ABSTRACT FROM AUTHOR]

ABSTRACT We study the clustering of matter in the intergalactic medium from the Lyman α forests seen in the spectra of pairs or groups of z∼ 2 quasars observed with FORS2 and UVES at the VLT-UT2 Kueyen ESO telescope. The sample consists of five pairs with separation of 0.6, 1, 2.1, 2.6 and 4.4 arcmin and a group of four quasars with separations from 2 up to 10 arcmin. This unprecedented data set allows us to measure the transverse flux correlation function for a range of angular scales. Correlations are clearly detectable at separations smaller than 3 arcmin. The shape and correlation length of the transverse correlation function on these scales are in good agreement with those expected from absorption by the photoionized warm intergalactic medium associated with the filamentary and sheet-like structures predicted in cold dark matter-like models for structure formation. At larger separation no significant correlation is detected. Assuming that the absorbing structures are randomly orientated with respect to the line of sight, the comparison of transverse and longitudinal correlation lengths constrains the cosmological parameters (as a modified version of the Alcock & Paczynski test). The present sample is too small to have significant constraints. Using N-body simulations, we investigate the possibility of constraining Ω[sub Λ] from future larger samples of quasistellar object pairs with similar separations. The observation of a sample of 30 pairs at 2, 4.5 and 7.5 arcmin should constrain the value of Ω[sub Λ] at ±15 per cent (2σ level). We also use the observed spectra of the group of four quasars to search for underdense regions in the intergalactic medium. We find a quasi-spherical structure of reduced absorption with radius 12.5 h[sup -1] Mpc , which we identify as an underdense region. [ABSTRACT FROM AUTHOR]

We present a time variability analysis of broad absorption lines (BAL; spread over the velocity range of 5800–29 000 km s−1) seen in the spectrum of J132216.25 + 052446.3 (z em = 2.04806) at ten different epochs spanning over 19 yr. The strongest absorption component (BAL-A; spread over 5800–9900 km s−1) is made up of several narrow components having velocity separations close to C  iv doublet splitting. The C  iv , N  v , and Si  iv absorption from BAL-A show correlated optical depth variability without major changes in the velocity structure. A very broad and shallow absorption (BAL-C; spread over the velocity range 15 000–29 000 km s−1) emerged during our monitoring period coinciding with a dimming episode of J1322 + 0524. All the identified absorption lines show correlated variability with the equivalent widths increasing with decreasing flux. This together with the C  iv emission line variability is consistent with ionization being the main driver of the correlated variability. The observed UV-continuum variations are weaker than what is required by the photoionization models. This together with a scatter in the C  iv equivalent width at a given continuum flux can be understood if variations of the C  iv ionizing photons are much larger than that of the UV continuum, the variations in the ionizing photon and UV fluxes are not correlated and/or the covering factor of the flow varies continuously. We suggest BAL-A is produced by a stable clumpy outflow located beyond the broad emission line region and BAL-C is a newly formed wind component located near the accretion disc and both respond to changes in the ionizing continuum. [ABSTRACT FROM AUTHOR]

We report a new, rare detection of H I 21 cm absorption associated with a quasar (only six quasars are known at 1 < z < 2) toward J2339−5523 at zem = 1.3531, discovered through the MeerKAT Absorption Line Survey (MALS). The absorption profile is broad (∼400 km s−1), and the peak is redshifted by ∼200 km s−1 from zem. Interestingly, optical/far-UV spectra of the quasar from the Magellan-MIKE/HST-COS spectrographs do not show any absorption features associated with the 21 cm absorption, despite the coincident presence of the optical quasar and the radio core inferred from a flat-spectrum component with a flux density of ∼65 mJy at high frequencies (> 5 GHz). The simplest explanation would be that no large H I column (N(H I) > 1017 cm−2) is present toward the radio core and the optical active galactic nucleus. Based on the joint optical and radio analysis of a heterogeneous sample of 16 quasars (zmedian = 0.7) and 19 radio galaxies (zmedian = 0.4) with H I 21 cm absorption detection and matched in 1.4 GHz luminosity (L1.4 GHz), a consistent picture emerges according to which quasars primarily trace the gas in the inner circumnuclear disk and cocoon created by the interaction of the jet with interstellar medium. They (i.e., quasars) exhibit a L1.4 GHz – ΔVnull correlation and a frequent mismatch of the radio and optical spectral lines. The radio galaxies show no such correlation and likely trace the gas from the cocoon and the galaxy-wide interstellar medium outside the photoionization cone. The analysis presented here demonstrates the potential of radio spectroscopic observations to reveal the origin of the absorbing gas associated with active galactic nuclei that may be missed in optical observations. [ABSTRACT FROM AUTHOR]

We present a detailed analysis of time variability of two distinct C  iv broad absorption line (BAL) components seen in the spectrum of J162122.54+075808.4 (z em = 2.1394) using observations from SDSS, NTT, and SALT taken at seven different epochs spanning about 15 yr. The blue-BAL component (with an ejection velocity, |$v_{\rm e}\sim 37\, 500$|  km s−1) is an emerging absorption that shows equivalent width variations and kinematic shifts consistent with acceleration. The red-BAL component (⁠|$v_{\rm e} \sim 15\, 400$|  km s−1) is a three-component absorption. One of the components is emerging and subsequently disappearing. The two other components show kinematic shifts consistent with acceleration coupled with equivalent width variability. Interestingly, we find the kinematic shifts and equivalent width variability of the blue- and red-BAL components to be correlated. While the C  iv emission-line flux varies by more than 17 per cent during our monitoring period, the available light curves (covering rest frame 1300–2300 Å) do not show more than a 0.1 mag variability in the continuum. This suggests that the variations in the ionizing flux are larger than that of the near-ultraviolet flux. However, the correlated variability seen between different BAL components cannot be explained solely by photoionization models without structural changes. In the framework of disc wind models, any changes in the radial profiles of density and/or velocity triggered either by disc instabilities or by changes in the ionizing radiation can explain our observations. High-resolution spectroscopic monitoring of J1621+0758 is important to understand the physical conditions of the absorbing gas and thereby to constrain the parameters of disc wind models. [ABSTRACT FROM AUTHOR]

The linear increase of the cosmic microwave background (CMB) temperature with cosmological redshift, , is a prediction of the standard cosmological CDM model. There are currently two methods to measure this dependence at redshift and, what is equally important, to estimate of the CMB temperature at the present epoch. The first method is based on the Sunyaev–Zeldovich effect for a galaxy cluster. However, this method is limited to redshifts and only the deviations from the standard relation can be measured with it. The second method is based on the analysis of the populations of atomic and molecular energy levels observed in the absorption spectra of quasars. This method allows to be measured directly. We present new estimates of in the redshift range based on the analysis of the excitation of CO rotational levels and C I fine-structure levels in 15 absorption systems. We take into account the collisional excitation of CO and C I with hydrogen atoms and and the radiative pumping of C I by the interstellar ultraviolet radiation. Applying this corrections leads to a systematic decrease in the previously obtained estimates of (for some systems the magnitude of the effect is ). Combining our measurements with the measurements of in galaxy clusters we have obtained a constraint on the parameter , which characterizes the deviation of the CMB temperature from the standard relation, , and an independent estimate of the CMB temperature at the present epoch, K, which agrees well with the estimate from orbital measurements, K. [ABSTRACT FROM AUTHOR]

Objective: To assess the risk of cesarean delivery after induction of labor in twin compared with singleton pregnancies.Study Design: This retrospective multicenter study compared data from two nationwide prospective cohorts: one of twin pregnancies established from February 2014 through March 2015 (JUMODA cohort), and the other of singleton pregnancies in November and December 2015 (MEDIP cohort). This study includes all women in both cohorts who had labor induced at ≥ 35 weeks of gestation, with a live fetus in cephalic presentation (Twin 1 for the twin pregnancies). Multivariate analyses with multilevel logistic regression models were used to study twin pregnancy as an independent risk factor for cesarean delivery, overall and stratified for parity and Bishop score.Results: The outcomes of 1995 twin births after induction of labor were compared to those of 2771 induced singleton births. The cesarean rate differed significantly between the two populations and was higher in twins (23% in twins vs 19.4% in singletons, P = 0.002). After adjustment for factors associated with cesareans, twin pregnancy was independently associated with it (aOR = 1.8, 95% CI 1.4-2.2).Conclusion: Twin pregnancy appears to be an independent risk factor for cesarean births after induction of labor, but more than three-quarters of inductions culminated in vaginal delivery. [ABSTRACT FROM AUTHOR]

An abstract of the article "The Sloan Digital Sky Survey quasar catalog: ninth data release" by I. Paris and colleagues is presented.

The chemical composition of gas in galaxies can be measured in great detail using absorption spectroscopy. By studying gas in galaxies in this way, it is possible to investigate small and faint galaxies, which are the most numerous in the universe. In particular, the chemical distribution of gas in absorbing systems gives us insight into cycles of gas in and around galaxies. In this work we study chemical enrichment within 64 damped Lyman- absorption systems (DLAs) for redshifts in the range 1:7 < z < 4:2. We use high-resolution spectra from VLT/UVES to infer dust depletion from relative abundances of several metals. Specifically, we performed a componentby- component analysis within DLAs, and characterised variations in their chemical enrichment. Unlike hydrogen, the metal columns can be characterised according to their individual components. We used them to derive the dust depletion, which is an indicator of chemical enrichment. Our main results are as follows. Firstly, we find that some DLAs are chemically diverse within themselves (with the measure of dust depletion [Zn/Fe]fit ranging up to 0.62 dex within a single system), suggesting that the absorbing gas within these galaxies is chemically diverse. Secondly, although we do not find a clear trend of decreasing dust depletion with redshift, we do see that the most chemically enriched systems are at lower redshifts. We also observe evidence for dust-poor components at all redshifts, which may be due to the accretion of pristine gas onto galaxies. By combining the chemical and kinematic properties of the individual gas components, we observe potential signatures of infalling gas with low depletion at velocities below ~100 km s1, and outflows with high depletion and velocities of ~600 km s1. Finally, we find over-abundances of -elements (an enhancement of ~0.3 dex) and under-abundances of Mn in several gas components, which is likely a signature of core-collapse supernovae nucleosythesis in the ISM. We observe these effects mostly at lower levels of chemical enrichment. [ABSTRACT FROM AUTHOR]

The BL Lac object PKS 1413+135 was observed by the Large Survey Project MeerKAT Absorption Line Survey (MALS) in the L-band, at 1139 MHz and 1293–1379 MHz, targeting the H I and OH lines in absorption at z = 0.24671. The radio continuum might come from the nucleus of the absorbing galaxy or from a background object at redshift lower than 0.5, as suggested by the absence of gravitational images. The H I absorption line is detected at a high signal-to-noise ratio, with a narrow central component, and with a red wing, confirming previous results. The OH 1720 MHz line is clearly detected in (maser) emission, peaking at a velocity shifted by −10 to −15 km s−1 with respect to the H I peak. The 1612 MHz line is lost due to radio frequency interference. The OH 1667 MHz main line is tentatively detected in absorption, but not the 1665 MHz line. Over 30 years a high variability is observed in optical depths, due to the rapid changes of the line of sight caused by the superluminal motions of the radio knots. The H I line has varied by 20% in depth, while the OH-1720 MHz depth has varied by a factor of ∼3. The position of the central velocity and the widths also varied. The absorbing galaxy is an early-type spiral (maybe S0) seen edge-on, with a prominent dust lane, covering the whole disk. Given the measured mass concentration and the radio continuum size at centimeter wavelengths (100 mas corresponding to 400 pc at z = 0.25), the width of the absorption lines from the nuclear regions are expected up to 250 km s−1. The narrowness of the observed lines (< 15 km s−1) suggests that the absorption comes from an outer gas ring, as frequently observed in S0 galaxies. The millimetric lines are even narrower (< 1 km s−1), which corresponds to the continuum size restricted to the core. The radio core is covered by individual 1 pc molecular clouds, whose column density is a few 1022 cm−2, which is compatible with the gas screen detected in X-rays. [ABSTRACT FROM AUTHOR]

We present MeerKAT Absorption Line Survey (MALS) observations of the H  i gas in the Klemola 31 galaxy group (z  = 0.029), located along the line of sight to the radio-loud quasar PKS 2020−370 (z  = 1.048). Four galaxies of the group are detected in H  i emission, and H  i absorption is also detected in front of PKS 2020−370 in Klemola 31A. The emission and absorption are somewhat compensating on the line of sight of the quasar, and the derived column density of the absorption appears underestimated, with respect to the neighbouring emission. A symmetric tilted-ring model of Klemola 31A, assuming the absorbing gas in regular rotation in the plane, yields a rather high spin temperature of 530 K. An alternative interpretation is that the absorbing gas is extra-planar, which will also account for its non-circular motion. The Na  i /Ca  ii ratio also suggests that the absorbing gas is unrelated to cold H  i disc. Two of the galaxies in the Klemola group are interacting with a small companion, and reveal typical tidal tails, and velocity perturbations. Only one of the galaxies, ESO 400−13, reveals a strong H  i deficiency, and a characteristic ram-pressure stripping, with a total asymmetry in the distribution of its gas. Since a small galaxy group as Klemola 31 is not expected to host a dense intra-group gas, this galaxy must be crossing the group at a very high velocity, mostly in the sky plane. [ABSTRACT FROM AUTHOR]

We demonstrate by quantitative experimental measurements that metamaterials with anisotropic properties can be used in the context of water waves to produce a reflectionless bent waveguide. The anisotropic medium consists in a bathymetry with subwavelength layered structure that shifts the wave in the direction of the waveguide bending (10°, 20°, and 30°). The waveguide filled with such metamaterial is tested experimentally and compared to a reference empty bent waveguide. The experimental method used to characterize the wave field allows for space-time resolved measurements of water elevation. Results show the efficiency of the shifter. Modal treatment of the experimental data confirms that the metamaterial prevents higher modes from being excited in the waveguide. [ABSTRACT FROM AUTHOR]

We report four new detections of 21-cm absorption from a systematic search of 21-cm absorption in a sample of 17 strong (rest equivalent width, Wr(Mg iiλ2796) ⩾ 1 Å) intervening Mg ii absorbers at 0.5 < zabs < 1.5. We also present 20-cm milliarcsecond scale maps of 40 quasars having 42 intervening strong Mg ii absorbers for which we have searched for 21-cm absorption. These maps are used to understand the dependence of 21-cm detection rate on the radio morphology of the background quasar and address the issues related to the covering factor of absorbing gas. Combining 21-cm absorption measurements for 50 strong Mg ii systems from our surveys with the measurements from literature, we obtain a sample of 85 strong Mg ii absorbers at 0.5 < zabs < 1 and 1.1 < zabs < 1.5. We present detailed analysis of this 21-cm absorption sample, taking into account the effect of the varying 21-cm optical depth sensitivity and covering factor associated with the different quasar sight lines. We find that the 21-cm detection rate is higher towards the quasars with flat or inverted spectral index at cm wavelengths. About 70% of 21-cm detections are towards the quasars with linear size, LS < 100 pc. The 21-cm absorption lines having velocity widths, ΔV > 100 km s-1 are mainly seen towards the quasars with extended radio morphology at arcsecond scales. However, we do not find any correlation between the integrated 21-cm optical depth, ∫ τdv, or the width of 21-cm absorption line, ΔV, with the LS measured from the milliarcsecond scale images. All this can be understood if the absorbing gas is patchy with a typical correlation length of ∼30-100 pc. We confirm our previous finding that the 21-cm detection rate for a given optical depth threshold can be increased by up to a factor 2 by imposing the following additional constraints: Mg ii doublet ratio <1.1, W(Mg ii)/W(Fe ii) < 1.47 and W(Mg i)/W(Mg ii) > 0.27. This suggests that the probability of detecting 21-cm absorption is higher in the systems with high N(H i). We show that within the measurement uncertainty, the 21-cm detection rate in strong Mg ii systems is constant over 0.5 < zabs < 1.5, i.e., over ∼30% of the total age of universe. We show that the detection rate can be underestimated by up to a factor 2 if 21-cm optical depths are not corrected for the partial coverage estimated using milliarcsecond scale maps. Since stellar feedback processes are expected to diminish the filling factor of cold neutral medium over 0.5 < z < 1, this lack of evolution in the 21-cm detection rate in strong Mg ii absorbers is intriguing. Large blind surveys of 21-cm absorption lines with the upcoming Square Kilometre Array pathfinders will provide a complete view of the evolution of cold gas in galaxies and shed light on the nature of Mg ii systems and DLAs, and their relationship with stellar feedback processes. [ABSTRACT FROM AUTHOR]

ABSTRACT We study the time variability of five Fe low-ionization broad absorption line (FeLoBAL) QSOs using repeated spectroscopic observations with the 2-m telescope at IUCAA Girawali Observatory (IGO) spanning an interval of up to 10 years. We report a dramatic variation in the Al iii and Fe iii fine-structure lines in the spectra of SDSS J221511.93−004549.9 ( zem∼ 1.478). However, there is no such strong variability shown by the C iv absorption. This source is known to be unusual with (i) the continuum emission dominated by Fe emission lines, (ii) Fe iii absorption being stronger than Fe ii and (iii) the apparent ratio of Fe iii UV 48 to Fe iii UV 34 absorption suggesting an inverted population ratio. This is the first reported detection of time variability in the Fe iii fine-structure lines in QSO spectra. There is a strong reduction in the absorption strength of these lines between 2000 and 2008. Using the template-fitting techniques, we show that the apparent inversion of the strength of ultraviolet lines could be related to the complex spectral energy distribution of this QSO. The observed variability can be related to a change in the ionization state of the gas or due to the transverse motion of this absorbing gas. The shortest variability time-scale of Al iii line gives a lower limit on the electron density of the absorbing gas as cm−3. The remaining four FeLoBALs do not show any changes beyond the measurement uncertainties either in optical depth or in the velocity structure. We present the long-term photometric light curve for all of our sources. Among them only SDSS J221511.93−004549.9 shows significant (≥0.2 mag) variability. [ABSTRACT FROM AUTHOR]

We study the time variability of five Fe low-ionization broad absorption line (FeLoBAL) QSOs using repeated spectroscopic observations with the 2-m telescope at IUCAA Girawali Observatory (IGO) spanning an interval of up to 10 years. We report a dramatic variation in the Al iii and Fe iii fine-structure lines in the spectra of SDSS J221511.93−004549.9 (zem∼ 1.478). However, there is no such strong variability shown by the C iv absorption. This source is known to be unusual with (i) the continuum emission dominated by Fe emission lines, (ii) Fe iii absorption being stronger than Fe ii and (iii) the apparent ratio of Fe iii UV 48 to Fe iii UV 34 absorption suggesting an inverted population ratio. This is the first reported detection of time variability in the Fe iii fine-structure lines in QSO spectra. There is a strong reduction in the absorption strength of these lines between 2000 and 2008. Using the template-fitting techniques, we show that the apparent inversion of the strength of ultraviolet lines could be related to the complex spectral energy distribution of this QSO. The observed variability can be related to a change in the ionization state of the gas or due to the transverse motion of this absorbing gas. The shortest variability time-scale of Al iii line gives a lower limit on the electron density of the absorbing gas as cm−3. The remaining four FeLoBALs do not show any changes beyond the measurement uncertainties either in optical depth or in the velocity structure. We present the long-term photometric light curve for all of our sources. Among them only SDSS J221511.93−004549.9 shows significant (≥0.2 mag) variability. [ABSTRACT FROM AUTHOR]

ABSTRACT We present the results of a systematic Green Bank Telescope and Giant Metrewave Radio Telescope survey for 21-cm absorption in a sample of 10 damped Lyman α systems (DLAs) at 2 ≤ zabs≤ 3.4. Analysis of L-band very long baseline array images of the background QSOs are also presented. We detect 21-cm absorption in only one DLA (at zabs= 3.1745 towards J1337+3152). Thus the detection rate of 21-cm absorption is ∼10 per cent when no limit on the integrated optical depth (∫τ( v)d v) is imposed and ∼13 per cent for a 3σ limit of 0.4 km s−1. Combining our data with the data from the literature (a sample of 28 DLAs) and assuming the measured core fraction at milliarcsecond scale to represent the gas covering factor, we find that the H i gas in DLAs at z≥ 2 is predominantly constituted by a warm neutral medium. The detection rate of 21-cm absorption seems to be higher for systems with higher N(H i) or metallicity. However, no clear correlation is found between the integrated 21-cm optical depth (or the spin temperature, TS) and either N(H i), metallicity or velocity spread of the low-ionization species. There are 13 DLAs in our sample for which high-resolution optical spectra covering the expected wavelength range of H2 absorption are available. We report the detection of H2 molecules in the zabs= 3.3871 21-cm absorber towards J0203+1134 (PKS 0201+113). In eight cases, neither H2 (with molecular fraction f(H2) ≤ 10−6) nor 21-cm absorption (with TS/ fc≥ 700 K) is detected. The lack of 21-cm and H2 absorption in these systems can be explained if most of the H i in these DLAs originates from low-density high-temperature gas. In one case we have a DLA with 21-cm absorption not showing H2 absorption. In two cases, both species are detected but do not originate from the same velocity component. In the remaining two cases 21-cm absorption is not detected despite the presence of H2 with evidence for the presence of cold gas. All this is consistent with the idea that the H2 components seen in DLAs are compact (with sizes of ≤15 pc) and contain only a small fraction (i.e. typically ≤10 per cent) of the total N(H i) measured in the DLAs. This implies that the molecular fractions f(H2) reported from the H2 surveys should be considered as conservative lower limits for the H2 components. [ABSTRACT FROM AUTHOR]

We study the X-ray and optical properties of 16 broad absorption line (BAL) quasars detected in a 3 deg region common to the wide synoptic (W-1) component of the Canada-France-Hawaii Telescope Legacy Survey (CFHTLS) and the XMM Large Scale Structure Survey (XMM-LSS). The BAL fraction is found to be 10 per cent in the full sample, 7 per cent for the optical colour-selected quasi-stellar objects (QSOs) and as high as 33 per cent if we consider QSOs selected from their infrared colours. The X-ray-detected non-BAL and BAL quasars have a mean observed X-ray-to-optical spectral slope () of and , respectively. We also find that the BAL QSOs have systematically smaller than what is expected from the relationship between optical luminosity and as derived from our sample. Based on this, we show, as already reported in the literature for quasars with high optical luminosities, that our new sample of BAL QSOs has X-ray luminosity a factor of 3 smaller than what has been found for non-BAL QSOs with similar optical luminosities. Comparison of hardness ratios of the BAL and non-BAL QSOs suggests a possible soft X-ray weakness of BAL QSOs. Combining our sample, of relatively fainter QSOs, with others from the literature we show that larger balnicity index (BI) and maximum velocity () of the C absorption are correlated with steeper X-ray-to-optical spectral index. We argue that this is most likely a consequence of the existence of a lower envelope in the distribution of BI (or ) values versus optical luminosity. Our results thus show that the previously known X-ray weakness of BAL QSOs extends to lower optical luminosities as well. [ABSTRACT FROM AUTHOR]

We estimate the He to H column density ratio, (He )/ N(He ), in the intergalactic medium towards the high-redshift ( bright quasar QSO HE 4342 using Voigt-profile fitting of the H transitions in the Lyman series and the He Lyman α transition as observed by the FUSE satellite. In agreement with previous studies, we find that in most of the Lyman α forest, except in four regions where it is much smaller () and therefore inconsistent with photoionization by the ultraviolet background flux. We detect O and C absorption lines associated with two of these regions ( and 2.6498). We show that, if we constrain the fit of the H and/or He absorption profiles with the presence of metal components, we can accommodate η values in the range 15-100 in these systems, assuming that broadening is intermediate between pure thermal and pure turbulent. While simple photoionization models reproduce the observed N(O )/ N(C ) ratio, they fail to produce low η values, in contrast to models with high temperatures (i.e K). The Doppler parameters measured for different species suggest a multiphase nature of the absorbing regions. Therefore, if low η values were to be confirmed, we would favour a multiphase model in which most of the gas is at a high temperature ( K) but the metals, and in particular C , are due to a lower-temperature (∼few 10 K) photoionized gas. [ABSTRACT FROM AUTHOR]

We report the detection of 21-cm and molecular hydrogen absorption lines in the same damped Lyman α system (DLA; with log N(H i) = 21.36 ± 0.10) at towards SDSS J133724.69+315254.55 ( ). We estimate the spin temperature of the gas to be K, intermediate between the expected values for cold and warm neutral media. This suggests that the H i absorption originates from a mixture of different phases. The total molecular fraction is low, , and H2 rotational level populations are not in equilibrium. The average abundance of the α-elements is [S/H]= . Nitrogen and iron are found underabundant with respect to α-elements by ∼1.0 and ∼0.5 dex, respectively. Using photoionization models we conclude that the gas, of mean density , is located more than 270 kpc away from the quasi-stellar object. While the position of the 21-cm absorption line coincides with the H2 velocity profile, its centroid is shifted by with respect to the redshift measured from the H2 lines. However, the position of the strongest metal absorption component matches the position of the 21-cm absorption line within 0.5 km s−1. From this, we constrain the variation of the combination of fundamental constants . This system is unique as we can at the same time have an independent constraint on μ using H2 lines. However, as the H2 column density is low, only Werner band absorption lines are seen and, unfortunately, the range of sensitivity coefficients is too narrow to provide a stringent constraint: . The Ultraviolet and Visual Echelle Spectrograph spectrum reveals another DLA at with log N(H i) = 20.41 ± 0.15 and low metallicity, [Si/H]= , in which [O/C] and [O/Si]∼ 0. This shows that even in the very early stages of chemical evolution, the carbon or silicon to oxygen ratios can be close to solar. Using Voigt profile fitting we derive log( N(D i)/ N(H i)) = in this system. This is a factor of 2 smaller than the value expected from the best-fitting value of Ωb from the Wilkinson Microwave Anisotropy Probe 5-yr data. This confirms the presence of astration of deuterium even at very low metallicity. [ABSTRACT FROM AUTHOR]

We present the results of a systematic Giant Metrewave Radio Telescope (GMRT) survey of 21-cm absorption in a representative and unbiased sample of 35 strong Mg ii systems in the redshift range: , 33 of which have . The survey using ∼400 h of telescope time has resulted in nine new 21-cm detections and stringent 21-cm optical depth upper limits (median 3σ optical depth per 10 km s−1 of 0.017) for the remaining 26 systems. This is by far the largest number of 21-cm detections from any single survey of intervening absorbers. Prior to our survey, no intervening 21-cm system was known in the above redshift range, and only one system was known in the redshift range . We discuss the relation between the detectability of 21-cm absorption and various properties of UV absorption lines. We show that if Mg ii systems are selected with the following criteria, Mg ii doublet ratio ≤1.3 and Wr(Mg i)/ Wr(Mg ii) ≥ 0.3, then a detection rate of 21-cm absorption up to 90 per cent can be achieved. We estimate n21, the number per unit redshift of 21-cm absorbers with and integrated optical depth , and show that n21 decreases with increasing redshift. In particular, for and falls by a factor of 4 from to . The evolution seems to be stronger for stronger Mg ii systems. Using a subsample of systems for which high-frequency Very Long Baseline Array (VLBA) images are available, we show that the effect is not related to the structure of the background radio sources and is most probably due to the evolution of the cold neutral medium filling factor in Mg ii systems. We find no correlation between the velocity spread of the 21-cm absorption feature and Wr(Mg ii) at . [ABSTRACT FROM AUTHOR]

We have discovered two dusty intervening Mg ii absorption systems at in the Sloan Digital Sky Survey (SDSS) data base. The overall spectra of both quasi-stellar objects (QSOs) are red and are well modelled by the composite QSO spectrum reddened by the extinction curve from the Large Magellanic Cloud (LMC2) Supershell redshifted to the rest frame of the Mg ii systems. In particular, we detect clearly the presence of the ultraviolet (UV) extinction bump at Å. Absorption lines of weak transitions like Si iiλ1808, Cr iiλ2056, Cr ii+ Zn iiλ2062, Mn iiλ2594, Ca iiλ3934 and Ti iiλ1910 from these systems are detected even in the low signal-to-noise ratio and low-resolution SDSS spectra, suggesting high column densities of these species. The depletion pattern inferred from these absorption lines is consistent with that seen in the cold neutral medium of the LMC. Using the LMC versus N(H i) relationship, we derive N(H i) in both systems. Metallicities are close to solar. Giant Metrewave Radio Telescope (GMRT) observations of these two relatively weak radio QSOs resulted in the detection of 21-cm absorption in both the cases. We show that the spin temperature of the gas is of the order of or smaller than 500 K. These systems provide a unique opportunity to search for molecules and diffuse interstellar bands at . [ABSTRACT FROM AUTHOR]

The human immunodeficiency virus type 1 (HIV-1) genome encodes a highly conserved regulatory gene product, Vpr (96 residues, 14 kDa), which is incorporated into virions. In the infected cells, Vpr, expressed late in the virus cycle, is believed to function in the early phases of HIV-1 replication, such as nuclear migration of pre-integration complex, transcription of the proviral genome, viral multiplication by blocking cells in G2 phase and regulation of apoptosis phenomenon. Vpr has a critical role in long term AIDS disease by inducing infection in non-dividing cells such as monocytes and macrophages. To gain insight into the structure–function relationships of Vpr, the (1–96)Vpr protein was synthesized with 22 labeled amino acids. Its 3D structure was analyzed in the presence of CD3CN and in pure water at low pH and refined by restrained simulated annealing. The structure of the protein is characterized by three well-defined α-helices: 17–33, 38–50 and 56–77 surrounded by flexible N and C-terminal domains. In contrast to the structure obtained in the presence of TFE, the three α-helices are folded around a hydrophobic core constituted of Leu, Ile, Val and aromatic residues as illustrated by numerous long range NOEs. This structure accounts for the interaction of Vpr with different targets. [Copyright &y& Elsevier]

The possible cosmological variation of the proton-to-electron mass ratio μ = m[sub p]/m[sub e] was estimated by measuring the H[sub 2] wavelengths in the spectra of distant quasars. We analyze high-resolution (FWHM ≈ 7 km s[sup -1]) spectra of the two damped Lyman-α systems at redshifts z[sub abs] = 2.3377 and 3.0249 observed in the spectra of the quasars Q 1232+082 and Q 0347-382, respectively. Our analysis yielded the most conservative estimate for the possible variation of μ in the past ∼10 Gyr, Δμ/μ = (5.7 ± 3.8) x 10[sup -5]. Since the significance of this result does not exceed 1.5σ, further observations are needed to increase the statistical significance. This is the most stringent limit on the possible cosmological variation of μ to date. [ABSTRACT FROM AUTHOR]

We present details of the Automated Radio Telescope Imaging Pipeline (ARTIP) and the results of a sensitive blind search for H i and OH absorbers at z < 0.4 and z < 0.7, respectively. ARTIP is written in Python 3.6, extensively uses the Common Astronomy Software Application tools and tasks, and is designed to enable the geographically distributed MeerKAT Absorption Line Survey (MALS) team to collaboratively process large volumes of radio interferometric data. We apply it to the first MALS data set obtained using the 64-dish MeerKAT radio telescope and 32 K channel mode of the correlator. With merely 40 minutes on target, we present the most sensitive spectrum of PKS 1830-211 ever obtained and characterize the known H i (z = 0.19) and OH (z = 0.89) absorbers. We further demonstrate ARTIP 's capabilities to handle realistic observing scenarios by applying it to a sample of 72 bright radio sources observed with the upgraded Giant Metrewave Radio Telescope (uGMRT) to blindly search for H i and OH absorbers. We estimate the numbers of H i and OH absorbers per unit redshift to be n21(z ∼ 0.18) < 0.14 and nOH(z ∼ 0.40) < 0.12, respectively, and constrain the cold gas covering factor of galaxies at large impact parameters (50 kpc < ρ < 150 kpc) to be less than 0.022. Due to the small redshift path, Δz ∼ 13 for H i with column density >5.4 × 1019 cm−2, the survey has probed only the outskirts of star-forming galaxies at ρ > 30 kpc. MALS with the expected Δz ∼ 103–4 will overcome this limitation and provide stringent constraints on the cold gas fraction of galaxies in diverse environments over 0 < z < 1.5. [ABSTRACT FROM AUTHOR]

Context. The identification of the sources that reionized the Universe and their specific contribution to this process are key missing pieces of our knowledge of the early Universe. Faint star-forming galaxies may be the main contributors to the ionizing photon budget during the epoch of reionization, but their escaping photons cannot be detected directly due to inter-galactic medium opacity. Hence, it is essential to characterize the properties of faint galaxies with significant Lyman continuum (LyC) photon leakage up to z ∼ 4 to define indirect indicators allowing analogs to be found at the highest redshift. Aims. Long gamma-ray bursts (LGRBs) typically explode in star-forming regions of faint, star-forming galaxies. Through LGRB afterglow spectroscopy it is possible to detect directly LyC photons. Our aim is to use LGRBs as tools to study LyC leakage from faint, star-forming galaxies at high redshift. Methods. Here we present the observations of LyC emission in the afterglow spectra of GRB 191004B at z = 3.5055, together with those of the other two previously known LyC-leaking LGRB host galaxies (GRB 050908 at z = 3.3467, and GRB 060607A at z = 3.0749), to determine their LyC escape fraction and compare their properties. Results. From the afterglow spectrum of GRB 191004B we determine a neutral hydrogen column density at the LGRB redshift of log(NH I/cm−2) = 17.2 ± 0.15, and negligible extinction (AV = 0.03 ± 0.02 mag). The only metal absorption lines detected are C IV and Si IV. In contrast to GRB 050908 and GRB 060607A, the host galaxy of GRB 191004B displays significant Lyman-alpha (Lyα) emission. From its Lyα emission and the non-detection of Balmer emission lines we constrain its star-formation rate (SFR) to 1 ≤ SFR ≤ 4.7 M⊙ yr−1. We fit the Lyα emission with a shell model and find parameters values consistent with the observed ones. The absolute (relative) LyC escape fractions we find for GRB 191004B, GRB 050908 and GRB 060607A are of 0.35−0.11+0.10 0. 35 − 0.11 + 0.10 $ 0.35^{+0.10}_{-0.11} $ (0.43−0.13+0.12 0. 43 − 0.13 + 0.12 $ 0.43^{+0.12}_{-0.13} $), 0.08−0.04+0.05 0. 08 − 0.04 + 0.05 $ 0.08^{+0.05}_{-0.04} $ (0.08−0.04+0.05 0. 08 − 0.04 + 0.05 $ 0.08^{+0.05}_{-0.04} $) and 0.20−0.05+0.05 0. 20 − 0.05 + 0.05 $ 0.20^{+0.05}_{-0.05} $ (0.45−0.15+0.15 0. 45 − 0.15 + 0.15 $ 0.45^{+0.15}_{-0.15} $), respectively. We compare the LyC escape fraction of LGRBs to the values of other LyC emitters found from the literature, showing that LGRB afterglows can be powerful tools to study LyC escape for faint high-redshift star-forming galaxies. Indeed we could push LyC leakage studies to much higher absolute magnitudes. The host galaxies of the three LGRBs presented here have all M1600 >  −19.5 mag, with the GRB 060607A host at M1600 >  −16 mag. LGRB hosts may therefore be particularly suitable for exploring the ionizing escape fraction in galaxies that are too faint or distant for conventional techniques. Furthermore, the time involved is minimal compared to galaxy studies. [ABSTRACT FROM AUTHOR]

Having analyzed the spectrum of the quasar PKS 1232+0.82 taken by Petitjean et al. (2000), we identified HD molecular lines in an absorption system at redshift z = 2.3377. We estimated the column density of HD molecules in this system, N(HD) = (1 - 4) × 10[sup 14] cm[sup -2]. The excitation temperature of the first rotational level J = 1 relative to the ground state J = 0 is T[sub ex] = 70 ± 7 K. As far as we know, this is the first detection of HD molecules at high redshift. [ABSTRACT FROM AUTHOR]

We present results from spectroscopic observations with X-shooter at the Very Large Telescope of seven H2-bearing damped Lyman-α systems (DLAs) at high redshifts (z abs ∼ 2.5–3). These DLAs were originally selected from the presence of strong H2 lines directly seen at the DLA redshift in low-resolution low signal-to-noise ratio SDSS spectra. We confirm the detection of molecular hydrogen in all of them. We measure the column densities of H  i , H2 in various rotational levels, and metal species, and associated dust extinction. The metallicities, obtained from undepleted species, are in the range log  Z  = −0.8 to −0.2. We discuss the chemical enrichment in these clouds and compare their properties with that of other molecular-rich systems selected by other means. In particular, we show that three different methods of pre-selection of H2-bearing DLAs in the SDSS have their own biases but complement each other mostly in terms of chemical enrichment. We use the rotational excitation of H2 molecules together with the fine-structure energy levels of neutral carbon to constrain the physical conditions in the gas with the help of numerical modelling as well as analytical expressions for the surface density at which atomic to molecular conversion happens. We find that the H2-bearing medium revealed by the studied DLAs has typical values for the kinetic temperature, hydrogen density, and UV radiation field of T ∼ 100 K, n H ∼ 100 cm−3, and I UV , respectively, about twice the intensity of the Draine field. Detailed studies combining different selections should therefore bring important clues to understand the H  i -H2 transition at high redshift. [ABSTRACT FROM AUTHOR]

We report the detections of molecular hydrogen (H2), vibrationally-excited H2 (H 2∗ 2 ∗ $ _{2}^{*} $), and neutral atomic carbon (C I), an efficient tracer of molecular gas, in two new afterglow spectra of GRBs 181020A (z = 2.938) and 190114A (z = 3.376), observed with X-shooter at the Very Large Telescope (VLT). Both host-galaxy absorption systems are characterized by strong damped Lyman-α absorbers (DLAs) and substantial amounts of molecular hydrogen with logN(H I, H2) = 22.20 ± 0.05,  20.40 ± 0.04 (GRB 181020A) and logN(H I, H2) = 22.15 ± 0.05,  19.44 ± 0.04 (GRB 190114A). The DLA metallicites, depletion levels, and dust extinctions are within the typical regimes probed by GRBs with [Zn/H] = −1.57 ± 0.06, [Zn/Fe] = 0.67 ± 0.03, and AV = 0.27 ± 0.02 mag (GRB 181020A) and [Zn/H] = −1.23 ± 0.07, [Zn/Fe] = 1.06 ± 0.08, and AV = 0.36 ± 0.02 mag (GRB 190114A). In addition, we examine the molecular gas content of all known H2-bearing GRB-DLAs and explore the physical conditions and characteristics required to simultaneously probe C I and H 2∗ 2 ∗ $ _{2}^{*} $. We confirm that H2 is detected in all C I- and H 2∗ 2 ∗ $ _{2}^{*} $ -bearing GRB absorption systems, but that these rarer features are not necessarily detected in all GRB H2 absorbers. We find that a large molecular fraction of fH2 ≳ 10−3 is required for C I to be detected. The defining characteristic for H 2∗ 2 ∗ $ _{2}^{*} $ to be present is less clear, though a large H2 column density is an essential factor. We also find that the observed line profiles of the molecular-gas tracers are kinematically "cold", with small velocity offsets of δv <  20 km s−1 from the bulk of the neutral absorbing gas. We then derive the H2 excitation temperatures of the molecular gas and find that they are relatively low with Tex ≈ 100−300 K, however, there could be evidence of warmer components populating the high-J H2 levels in GRBs 181020A and 190114A. Finally, we demonstrate that even though the X-shooter GRB afterglow campaign has been successful in recovering several H2-bearing GRB-host absorbers, this sample is still hampered by a significant dust bias excluding the most dust-obscured H2 absorbers from identification. C I and H 2∗ 2 ∗ $ _{2}^{*} $ could open a potential route to identify molecular gas even in low-metallicity or highly dust-obscured bursts, though they are only efficient tracers for the most H2-rich GRB-host absorption systems. [ABSTRACT FROM AUTHOR]

We present results from a search for strong H2 absorption systems proximate to quasars (zabs ≈ zem) in the Sloan Digital Sky Survey (SDSS) Data Release 14. The search is based on the Lyman-Werner band signature of damped H2 absorption lines without any prior on the associated metal or neutral hydrogen content. This has resulted in the detection of 81 systems with N(H2) ∼ 1019 − 1020 cm−2 located within a few thousand km s−1 from the quasar. Compared to a control sample of intervening systems, this implies an excess of proximate H2 systems by about a factor of 4 to 5. The incidence of H2 systems increases steeply with decreasing relative velocity, reaching an order of magnitude higher than expected from intervening statistics at Δv <  1000 km s−1. The most striking feature of the proximate systems compared to the intervening ones is the presence of Ly − α emission in the core of the associated damped H I absorption line in about half of the sample. This puts constraints on the relative projected sizes of the absorbing clouds to those of the quasar line emitting regions. Using the SDSS spectra, we estimate the H I, metal and dust content of the systems, which are found to have typical metallicities of one tenth Solar, albeit with a large spread among individual systems. We observe trends between the fraction of leaking Ly − α emission and the relative absorber-quasar velocity as well as with the excitation of several metal species, similar to what has been seen in metal-selected proximate DLAs. With the help of theoretical H I-H2 transition relations, we show that the presence of H2 helps to break the degeneracy between density and strength of the UV field as main sources of excitation and hence provides unique constraints on the possible origin and location of the absorbing clouds. We suggest that most of these systems originate from galaxies in the quasar group, although a small fraction of them could be located in the quasar host as well. We conclude that follow-up observations are still required to investigate the chemical and physical conditions in individual clouds and to assess the importance of AGN feedback for the formation and survival of H2 clouds. [ABSTRACT FROM AUTHOR]

A small subset of optically selected radio-quiet quasars showing weak or no emission lines may turn out to be the elusive radio-quiet BL Lac objects, or simply be radio-quiet QSOs with a still-forming/shielded broad line region (BLR). High polarization (p > 3–4 per cent), a hallmark of BL Lacs, can be used to test whether some optically selected ‘radio-quiet weak emission line quasars’ (RQWLQs) show a fractional polarization high enough to qualify as radio-quiet analogues of BL Lac objects. Out of the observed six RQWLQs candidates showing an insignificant proper motion, only two are found to have p > 1 per cent. For these two RQWLQs, namely J142505.59 + 035336.2 and J154515.77+003235.2, we found polarization of 1.03 ± 0.36 per cent and 1.59 ± 0.53 per cent, respectively, which again is too modest to justify a (radio-quiet) BL Lac classification. We also present here a statistical comparison of the optical spectral index, for a set of 40 RQWLQs with redshift-luminosity matched control sample of 800 QSOs and an equivalent sample of 120 blazars. The spectral index distribution of RQWLQs is found to differ, at a high significance level, from that of blazars and is consistent with that of the ordinary QSOs. Likewise, a structure–function analysis of photometric light curves presented here suggests that the mechanism driving optical variability in RQWLQs is similar to that operating in QSOs and different from that of blazars. These findings are consistent with the common view that the central engine in RQWLQs, as a population, is akin to that operating in normal QSOs and the primary differences between them might be related to differences in the BLR. [ABSTRACT FROM AUTHOR]

Drying and rewetting (DRW) events in soils cause the release of molybdate-unreactive dissolved phosphorus (MUP) into soil solutions, which has been historically considered biologically-derived phosphorus (P) from microbial cell lysis. This unreactive P, however, could also represent P bound to soil colloids/nanoparticles, whose releases are also known to be physically stimulated during DRW events. To explore this possibility, two riparian wetland soils (A and B) with contrasting soil P speciation were subjected to three successive DRW cycles in soil columns. Leachates were successively filtrated/ultrafiltrated with 0.45 μm, 30 kDa and 5 kDa pore size membranes to separate the different colloidal/nanoparticulate fractions, in which molybdate-reactive P (MRP), total P (TP), MUP (defined as TP minus MRP), Fe, Al and dissolved organic carbon (DOC) concentrations were measured. For both soils, TP concentrations peaked at the beginning of each rewetting event then decreased rapidly upon leaching. MUP concentrations appeared similar variations as TP, but MRP concentrations remained relatively constant during leaching. Soil B showed larger TP release peaks than soil A and contained different P forms (more MUP and MRP, respectively). In both soils, colloidal/nanoparticulate P was an important fraction (up to 70%) of TP (<0.45 μm) in leachates immediately after rewetting, then this proportion decreased markedly at the end of each DRW cycle. On average, the proportion of colloidal/nanoparticulate P in TP was much higher in soil B than in soil A (45% vs. 17%). Results suggested that the colloidal/nanoparticulate carriers likely consisted of a mixture of Fe/Al oxides and organic matter, and highlighted a higher colloidal/nanoparticulate P release capacity in soil B with higher soil organic matter content and porosity. In addition, colloidal/nanoparticulate P and truly dissolved MUP had a greater response to DRW events and were exhausted more rapidly than truly dissolved MRP and smaller nanoparticulate P, suggesting potential differences in their sources and production mechanisms. Thus, this study demonstrates that colloidal/nanoparticulate P can represent an important part of the unreactive P fraction released during DRW events in soils and further highlights the importance of the colloidal/nanoparticulate P fraction in the transport and cycling of P in soils and waters. [ABSTRACT FROM AUTHOR]

We present a detailed study of the quasar-galaxy pair: J1243+4043-UGC 07904. The sight line of the background quasar (zq = 1.5266) passes through a region of the galaxy (zg = 0.0169) at an impact parameter of 6.9 kpc with high metallicity (0.5 Z⊙) and negligible dust extinction. We detect H I 21-cm absorption from the foreground galaxy at arcsecond and milliarcsecond scales. For typical cold neutral medium (CNM) temperatures in the Milky Way, this 21-cm absorber can be classified as a damped Lyα absorber (DLA). We infer the harmonic mean spin temperature of the gas to be ~400K and for a simple two-phase medium we estimate the CNM fraction to be fCNM = 0.27. This is remarkably consistent with the CNM fraction observed in the Galaxy and less than that of high-redshift DLAs. The quasar exhibits a core-jet morphology on milliarcsecond scales, corresponding to an overall extent of ~9 pc at zg. We show that the size of CNM absorbing clouds associated with the foreground galaxy is >5 pc and they may be part of cold gas structures that extend beyond ~35 pc. Interestingly, the rotation measure of quasar J1243+4043 is higher than any other source in samples of quasars with high-z DLAs. However, we do not find any detectable differences in rotation measures and polarization fraction of sight lines with or without high-z (z ≥ 2) DLAs or low-z (z ≤ 0.3) 21-cm absorbers. Finally, the foreground galaxy UGC07904 is also part of a galaxy group. We serendipitously detect H I 21-cm emission from four members of the group, and an ~80 kpc long HI bridge connecting two of the other members. The latter, together with the properties of the group members, suggests that the group is a highly interactive environment. [ABSTRACT FROM AUTHOR]

For a new sample of eight weak-line quasars (WLQs) we report a sensitive search in 20 intranight monitoring sessions, for blazar-like optical flux variations on hour-like and longer time-scale (day/month/year-like). The sample consists exclusively of the WLQs that are not radio-loud and either have been classified as ‘radio-weak probable BL Lac candidates’ and/or are known to have exhibited at least one episode of large, blazar-like optical variability. Whereas only a hint of intranight variability is seen for two of these WLQs, J104833.5+620305.0 (z = 0.219) and J133219.6+622715.9 (z = 3.15), statistically significant internight variability at a few per cent level is detected for three of the sources, including the radio-intermediate WLQ J133219.6+622715.9 (z = 3.15) and the well-known bona fide radio-quiet WLQs J121221.5+534128.0 (z = 3.10) and WLQ J153259.9−003944.1 (z = 4.62). In the rest frame, this variability is intraday and in the far-ultraviolet band. On the time-scale of a decade, we find for three of the WLQs large brightness changes, amounting to 1.655 ± 0.009, 0.163 ± 0.010 and 0.144 ± 0.018 mag, for J104833.5+620305.0, J123743.1+630144.9 and J232428.4+144324.4, respectively. Whereas the latter two are confirmed radio-quiet WLQs, the extragalactic nature of J104833.5+620305.0 remains to be well established, thanks to the absence of any feature(s) in its available optical spectra. This study forms a part of our ongoing campaign of intranight optical monitoring of radio-quiet WLQs, in order to improve the understanding of this enigmatic class of active galactic nuclei and to look among them for a possible tiny, elusive population of radio-quiet BL Lacs. [ABSTRACT FROM AUTHOR]

We present a detailed analysis of an H2-rich, extremely strong intervening damped Ly α absorption system (DLA) at zabs = 2.786 towards the quasar J 0843+0221, observed with the Ultraviolet and Visual Echelle Spectrograph on the Very Large Telescope. The total column density of molecular (resp. atomic) hydrogen is log N(H2) = 21.21 ± 0.02 (resp. log N(H I) = 21.82 ± 0.11), making it to be the first case in quasar absorption line studies with H2 column density as high as what is seen in 13CO-selected clouds in the Milky Way. We find that this system has one of the lowest metallicity detected among H2-bearing DLAs, with [Zn/H] = −1.52+0.08 −0.10. This can be the reason for the marked differences compared to systems with similar H2 column densities in the local Universe: (i) the kinetic temperature, T ∼ 120 K, derived from the J = 0, 1 H2 rotational levels is at least twice higher than expected; (ii) there is little dust extinction with AV < 0.1; (iii) no CO molecules are detected, putting a constraint on the XCO factor XCO > 2 × 1023 cm−2/(km s−1 K), in the very low metallicity gas. Low CO and high H2 contents indicate that this system represents 'CO-dark/faint' gas. We investigate the physical conditions in the H2-bearing gas using the fine-structure levels of C I, CII, Si II and the rotational levels of HD and H2. We find the number density to be about n ∼ 260–380 cm−3, implying a high thermal pressure of 3–5 × 104 cm−3 K.We further identify a trend of increasing pressure with increasing total hydrogen column density. This independently supports the suggestion that extremely strong DLAs (with log N(H)∼22) probe high-z galaxies at low impact parameters. [ABSTRACT FROM AUTHOR]

Broad absorption lines (BALs) found in a significant fraction of quasar spectra identify highvelocity outflows that might be present in all quasars and could be a major factor in feedback to galaxy evolution. Understanding the nature of these flows requires further constraints on their physical properties, including their column densities, for which well-studied BALs, such as CIV λλ1548,1551, typically provide only a lower limit because of saturation effects. Low abundance lines, such as P V λλ1118,1128, indicate large column densities, implying that outflows more powerful than measurements of C IV alone would indicate. We search through a sample of 2694 BAL quasars from the Sloan Digital Sky Survey III/Baryon Oscillation Spectroscopic Survey data release 9 quasar catalogue for such absorption, and we identify 81 ‘definite’ and 86 ‘probable’ detections of P V broad absorption, yielding a firm lower limit of 3.0–6.2 per cent for the incidence of such absorption among BAL quasars. The P V-detected quasars tend to have stronger C IV and Si IV absorption, as well as a higher incidence of LoBAL absorption, than the overall BAL quasar population. Many of the P V-detected quasars have C IV troughs that do not reach zero intensity (at velocities where P V is detected), confirming that the outflow gas only partially covers the UV continuum source. P V appears significantly in a composite spectrum of non-P V-detected BAL quasars, indicating that P V absorption (and large column densities) is much more common than indicated by our search results. Our sample of P V detections significantly increases the number of known P V detections, providing opportunities for follow-up studies to better understand BAL outflow energetics. [ABSTRACT FROM AUTHOR]

We present the results from our search for H I 21-cm absorption in a sample of 16 strong Fe II systems [Wr(Mg II λ2796) ≥ 1.0 Å and Wr(Fe II λ2600) or WFeII ≥ 1 Å] at 0.5 < z < 1.5 using the Giant Metrewave Radio Telescope and the Green Bank Telescope. We report six new H I 21-cm absorption detections from our sample, which have increased the known number of detections in strong Mg II systems at this redshift range by ~50 per cent. Combining our measurements with those in the literature, we find that the detection rate of H I 21-cm absorption increases with,WFeII, being four times higher in systems with WFeII ≥ 1 Å compared to systems with WFeII < 1 Å. The N(HI) associated with the H I 21-cm absorbers would be ≥2 x 1020 cm-2, assuming a spin temperature of ~500 K (based on H I 21-cm absorption measurements of damped Lyman α systems at this redshift range) and unit covering factor. We find that H I 21-cm absorption arises on an average in systems with stronger metal absorption. We also find that quasars with H I 21-cm absorption detected towards them have systematically higher E(B - V) values than those which do not. Further, by comparing the velocity widths of H I 21-cm absorption lines detected in absorption- and galaxy-selected samples, we find that they show an increasing trend (significant at 3.8σ) with redshift at z < 3.5, which could imply that the absorption originates from more massive galaxy haloes at high z. Increasing the number of H I 21-cm absorption detections at these redshifts is important to confirm various trends noted here with higher statistical significance. [ABSTRACT FROM AUTHOR]