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Objective: The maternal cardiovascular system of women with hypertensive disorders of pregnancy (HDP) can be impaired, with higher rates of left ventricular (LV) remodeling and diastolic dysfunction compared to those with normotensive pregnancy. The primary objective of this prospective study was to correlate cardiac indices obtained by transthoracic echocardiography (TTE) and circulating angiogenic markers, such as soluble fms‐like tyrosine kinase‐1 (sFlt‐1) and placental growth factor (PlGF). Methods: In this study, 95 women with a pregnancy complicated by HDP and a group of 25 with an uncomplicated pregnancy at term underwent TTE and blood tests to measure sFlt‐1 and PlGF during the peripartum period (before delivery or within a week of giving birth). Spearman's rank correlation was used to derive correlation coefficients between biomarkers and cardiac indices in the HDP and control populations. Results: The HDP group included 61 (64.2%) pre‐eclamptic patients and, among them, 42 (68.9%) delivered before 37 weeks' gestation. Twelve women with HDP (12.6%) underwent blood sampling and TTE after delivery, and, as they showed significantly lower levels of angiogenic markers, they were excluded from the analysis. There was a correlation between sFlt‐1 and LV mass index (LVMI) (r = 0.246; P = 0.026) and early diastolic mitral inflow velocity (E) and early diastolic mitral annular velocity (e′) ratio (r = 0.272; P = 0.014) in the HDP group (n = 83), while in the controls, sFlt‐1 showed a correlation with relative wall thickness (r = 0.409; P = 0.043), lateral e′ (r = −0.562; P = 0.004) and E/e′ ratio (r = 0.417; P = 0.042). PlGF correlated with LVMI (r = −0.238; P = 0.031) in HDP patients and with lateral e′ (r = 0.466; P = 0.022) in controls. sFlt‐1/PlGF ratio correlated with lateral e′ (r = −0.568; P = 0.004) and E/e′ ratio (r = 0.428; P = 0.037) in controls and with LVMI (r = 0.252; P = 0.022) and E/e′ ratio (r = 0.269; P = 0.014) in HDP. Conclusions: Although the current data are not able to infer causality, they confirm the intimate relationship between the maternal cardiovascular system and angiogenic markers that are used both to diagnose and indicate the severity of HDP. © 2023 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology. [ABSTRACT FROM AUTHOR]

Objective: There has been an unprecedented fall in the rate of stillbirth in twin pregnancy in the UK. It is contested whether implementation of the National Institute for Health and Care Excellence (NICE) guidance on the antenatal management of uncomplicated twin pregnancies has contributed to this change. The aim of this study was to investigate whether the implementation of NICE guidance was associated with a reduction in the rate of stillbirth in twin pregnancies delivered in a large UK hospital. Methods: This was a retrospective cohort study including all twin pregnancies delivered at St George's Hospital, London, UK, between 2000 and 2018. Data were analyzed according to two time periods: before implementation of the NICE guidance on twins (before June 2013; pre‐NICE) and after its implementation (after June 2013; post‐NICE). The exclusion criteria were higher‐order multiple gestations, pregnancies of unknown chorionicity, pregnancies complicated by miscarriage, those that underwent termination and those diagnosed with vanishing twin. The main outcome was stillbirth. Other outcomes included neonatal death (NND), admission to the neonatal intensive care unit (NICU) and emergency Cesarean section. We planned a priori a sensitivity analysis according to chorionicity. The chi‐square test and Mann–Whitney U‐test were used to compare outcomes between the study groups. Results: We included in the analysis 1666 twin pregnancies (3332 fetuses), of which 1114 pregnancies (2228 fetuses) were delivered before and 552 pregnancies (1104 fetuses) after June 2013. Of those, 1299 were dichorionic and 354 were monochorionic diamniotic. The incidence of stillbirth was significantly lower in the post‐NICE than in the pre‐NICE group (3.6 per 1000 births vs 13.5 per 1000 births; P = 0.008). The reduction in stillbirth rate was from 8.5 to 3.6 per 1000 births (P = 0.161) in dichorionic and from 33.6 to 3.8 per 1000 births (P = 0.011) in monochorionic diamniotic twin pregnancies. There was no significant difference in the rates of NND (P = 0.625), NICU admission (P = 0.506) or emergency Cesarean section (P = 0.820) between the two groups. The median gestational age at delivery was significantly lower in the post‐NICE than in the pre‐NICE group (median 36.3 vs 36.9 weeks; P < 0.001), as a consequence of a significant increase in preterm birth between 34 and 37 weeks' gestation (39.3% vs 27.0%; P = 0.002), but not before 34 weeks (P = 0.473). Conclusions: A significant reduction of > 70% in the stillbirth rate in twin pregnancies was noted after implementation of the NICE guidance. This reduction was statistically significant in monochorionic, but not dichorionic, twin pregnancies. The improvement in twin pregnancy outcome was achieved without a concomitant increase in NND, admission to the NICU or emergency Cesarean section. © 2020 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of the International Society of Ultrasound in Obstetrics and Gynecology. [ABSTRACT FROM AUTHOR]

Context. The analysis of the UV slope β of Lyman-break galaxies (LBG) at different luminosities and redshifts is fundamental for understanding their physical properties, and in particular, their dust extinction. Aims. We analyse a unique sample of 517 bright (L >  L*) LBGs at redshift z ∼ 3 in order to characterise the distribution of their UV slopes β and infer their dust extinction under standard assumptions. Methods. We exploited multi-band observations over 750 arcmin2 of the COSMOS field that were acquired with three different ground-based facilities: the Large Binocular Camera (LBC) on the Large Binocular Telescope (LBT), the Suprime-Cam on the SUBARU telescope, and the VIRCAM on the VISTA telescope (ULTRAVISTA DR2). Our multi-band photometric catalogue is based on a new method that is designed to maximise the signal-to-noise ratio in the estimate of accurate galaxy colours from images with different point spread functions (PSF). We adopted an improved selection criterion based on deep Y-band data to isolate a sample of galaxies at z ∼ 3 to minimise selection biases. We measured the UV slopes (β) of the objects in our sample and then recovered the intrinsic probability density function of β values (PDF(β)), taking into account the effect of observational uncertainties through detailed simulations. Results. The galaxies in our sample are characterised by mildly red UV slopes with ⟨β⟩≃ − 1.70 throughout the enitre luminosity range that is probed by our data (−24 ≲ M1600 ≲ −21). The resulting dust-corrected star formation rate density (SFRD) is log(SFRD)≃ − 1.6 M⊙ yr−1 Mpc−3, corresponding to a contribution of about 25% to the total SFRD at z ∼ 3 under standard assumptions. Conclusions. Ultra-bright LBGs at z ∼ 3 match the known trends, with UV slopes being redder at decreasing redshifts, and brighter galaxies being more highly dust extinct and more frequently star-forming than fainter galaxies. [ABSTRACT FROM AUTHOR]

We present the results of CANDELSz7, a European Southern Observatory (ESO) Large Program aimed at spectroscopically confirming a homogeneous sample of z ≃ 6 and z ≃ 7 star forming galaxies. The candidates were selected in the GOODS-South, UDS, and COSMOS fields using the official CANDELS catalogs based on H160-band detections. Standard color criteria, which were tailored depending on the ancillary multi-wavelength data available for each field, were applied to select more than 160 candidate galaxies at z ≃ 6 and z ≃ 7. Deep, medium-resolution FORS2 spectroscopic observations were then conducted with integration times ranging from 12 to 20 h to reach a Lyα flux limit of approximately 1 − 3 × 10−18 erg s−1 cm−2 at 3σ. We could determine a spectroscopic redshift for about 40% of the galaxies, mainly through the detection of a single emission line that we interpret as Lyα emission, or for some of the brightest objects (H160 ≤ 25.5) from the presence of faint continuum and a sharp drop that we interpret as a Lyα break. In this paper we present the redshifts and main properties of 65 newly confirmed high-redshift galaxies. Adding previous proprietary and archival data we assemble a sample of ≃260 galaxies that we use to explore the evolution of the Lyα fraction in Lyman break galaxies and the change in the shape of the emission line between z ∼ 6 and z ∼ 7. We also discuss the accuracy of the CANDELS photometric redshifts in this redshift range. [ABSTRACT FROM AUTHOR]

Winds accelerated by active galactic nuclei (AGNs) are invoked in the most successful models of galaxy evolution to explain the observed physical and evolutionary properties of massive galaxies. Winds are expected to deposit energy and momentum into the interstellar medium (ISM), thus regulating both star formation and supermassive black hole (SMBH) growth. We undertook a multiband observing program aimed at obtaining a complete census of winds in a sample of WISE/SDSS selected hyper-luminous (WISSH) quasars (QSOs) at z ≈ 2–4. We analyzed the rest-frame optical (i.e. LBT/LUCI and VLT/SINFONI) and UV (i.e. SDSS) spectra of 18 randomly selected WISSH QSOs to measure the SMBH mass and study the properties of winds both in the narrow line region (NLR) and broad line region (BLR) traced by blueshifted or skewed [OIII] and CIV emission lines, respectively. These WISSH QSOs are powered by SMBH with masses ≳109M⊙ accreting at 0.4 < λEdd < 3.1. We found the existence of two subpopulations of hyper-luminous QSOs characterized by the presence of outflows at different distances from the SMBH. One population (i.e. [OIII] sources) exhibits powerful [OIII] outflows, a rest-frame equivalent width (REW) of the CIV emission REWCIV ≈ 20–40 Å, and modest CIV velocity shift (vCIVpeak $v_{\textrm{CIV}}^{\textrm{peak}}$ v CIV peak ) with respect to the systemic redshift (vCIVpeak $v_{\textrm{CIV}}^{\textrm{peak}}$ v CIV peak <~ 2000 km s−1). The second population (i.e. Weak [OIII] sources), representing ~70% of the analyzed WISSH QSOs, shows weak or absent [OIII] emission and an extremely large blueshifted CIV emission (vCIVpeak $v_{\textrm{CIV}}^{\textrm{peak}}$ v CIV peak up to ~8000 km s−1 and REWCIV <~ 20 Å). We propose two explanations for the observed behavior of the strength of the [OIII] emission in terms of the orientation effects of the line of sight and ionization cone. The dichotomy in the presence of BLR and NLR winds could be likely due to inclination effects considering a polar geometry scenario for the BLR winds. In a few cases these winds are remarkably as powerful as those revealed in the NLR in the [OIII] QSOs (Ėkin ~ 1044−45 erg s−1). We also investigated the dependence of these CIV winds on fundamental AGN parameters such as bolometric luminosity (LBol), Eddington ratio (λEdd), and UV-to-X-ray continuum slope (αOX). We found a strong correlation with LBol and an anti-correlation with αOX whereby the higher the luminosity, the steeper the ionizing continuum described by means of αOX and the larger the blueshift of the CIV emission line. Finally, the observed dependence vCIVpeak $v_{\textrm{CIV}}^{\textrm{peak}}$ v CIV peak ∝ LBol0.28 ± 0.04 $L_{\textrm{Bol}}^{0.28~\pm~0.04}$ L Bol 0.28   ±   0.04 is consistent with a radiatively-driven-winds scenario, where a strong UV continuum is necessary to launch the wind and a weakness of the X-rayemission is fundamental to prevent overionization of the wind itself. [ABSTRACT FROM AUTHOR]

Context. Finding the sources responsible for the hydrogen reionization is one of the most pressing issues in observational cosmology. Bright quasi-stellar objects (QSOs) are known to ionize their surrounding neighborhood, but they are too few to ensure the required HI ionizing background. A significant contribution by faint active galactic nuclei (AGNs), however, could solve the problem, as recently advocated on the basis of a relatively large space density of faint active nuclei at z > 4. Aims. This work is part of a long-term project aimed at measuring the Lyman Continuum escape fraction for a large sample of AGNs at z ~ 4 down to an absolute magnitude of M1450 ~ -23. We have carried out an exploratory spectroscopic program to measure the HI ionizing emission of 16 faint AGNs spanning a broad U-I color interval, with I ~ 21-23, and 3:6 < z < 4.2. These AGNs are three magnitudes fainter than the typical SDSS QSOs (M1450 . ≲26) which are known to ionize their surrounding IGM at z ≳ 4. Methods. We acquired deep spectra of these faint AGNs with spectrographs available at the VLT, LBT, and Magellan telescopes, that is, FORS2, MODS1-2, and LDSS3, respectively. The emission in the Lyman Continuum region, close to 900 Å rest frame, has been detected with a signal to noise ratio of ~10-120 for all 16 AGNs. The flux ratio between the 900 Å rest-frame region and 930 Å provides a robust estimate of the escape fraction of HI ionizing photons. Results. We have found that the Lyman Continuum escape fraction is between 44 and 100% for all the observed faint AGNs, with a mean value of 74% at 3:6 < z < 4.2 and -25.1 ≲ M1450 ≲-23.3, in agreement with the value found in the literature for much brighter QSOs (M1450 ≲ -26) at the same redshifts. The Lyman Continuum escape fraction of our faint AGNs does not show any dependence on the absolute luminosities or on the observed U-I colors of the objects. Assuming that the Lyman Continuum escape fraction remains close to ~75% down to M1450 ~ -18, we find that the AGN population can provide between 16 and 73% (depending on the adopted luminosity function) of the whole ionizing UV background at z ~ 4, measured through the Lyman forest. This contribution increases to 25-100% if other determinations of the ionizing UV background are adopted from the recent literature. Conclusions. Extrapolating these results to z ~ 5-7, there are possible indications that bright QSOs and faint AGNs can provide a significant contribution to the reionization of the Universe, if their space density is high at M1450 ~ -23. [ABSTRACT FROM AUTHOR]

Context: The reionization of the Universe is one of the most important topics of present-day astrophysical research. The most plausible candidates for the reionization process are star-forming galaxies, which according to the predictions of the majority of the theoretical and semi-analytical models should dominate the H I ionizing background at z ≳ 3. Aims: We measure the Lyman continuum escape fraction, which is one of the key parameters used to compute the contribution of star-forming galaxies to the UV background. It provides the ratio between the photons produced at λ ≤ 912 Å rest-frame and those that are able to reach the inter-galactic medium, i.e. that are not absorbed by the neutral hydrogen or by the dust of the galaxy's inter-stellar medium. Methods: We used ultra-deep U-band imaging (U = 30.2 mag at 1σ) from Large Binocular Camera at the Large Binocular Telescope (LBC/LBT) in the CANDELS/GOODS-North field and deep imaging in the COSMOS and EGS fields in order to estimate the Lyman continuum escape fraction of 69 star-forming galaxies with secure spectroscopic redshifts at 3.27 ≤ z ≤ 3.40 to faint magnitude limits (L = 0.2L*, or equivalently M1500 ~ - 19). The narrow redshift range implies that the LBC U-band filter exclusively samples the λ ≤ 912 Å rest-frame wavelengths. Results: We measured through stacks a stringent upper limit (<1.7% at 1σ) for the relative escape fraction of H I ionizing photons from bright galaxies (L>L*), while for the faint population (L = 0.2L*) the limit to the escape fraction is ≲ 10%. We computed the contribution of star-forming galaxies to the observed UV background at z ~ 3 and find that it is not sufficient to keep the Universe ionized at these redshifts unless their escape fraction increases significantly (≥ 10%) at low luminosities (M1500 ≥ - 19). Conclusions: We compare our results on the Lyman continuum escape fraction of high-z galaxies with recent estimates in the literature, and discuss future prospects to shed light on the end of the Dark Ages. In the future, strong gravitational lensing will be fundamental in order to measure the Lyman continuum escape fraction down to faint magnitudes (M1500~ - 16) that are inaccessible with the present instrumentation on blank fields. These results will be important in order to quantify the role of faint galaxies to the reionization budget. [ABSTRACT FROM AUTHOR]

Context. Establishing the number of faint active galactic nuclei (AGNs) at z = 4-6 is crucial to understanding their cosmological importance as main contributors to the reionization of the Universe. Aims. In order to derive the AGN contribution to the cosmological ionizing emissivity we have selected faint AGN candidates at z> 4 in the CANDELS GOODS-South field, which is one of the deepest fields with extensive multiwavelength coverage from Chandra, HST, Spitzer, and various ground-based telescopes. Methods. We have adopted a relatively novel criterion. As a first step, high redshift galaxies are selected in the NIR H band down to very faint levels (H ≤ 27) using reliable photometric redshifts. At z > 4 this corresponds to a selection criterion based on the galaxy rest-frame UV flux. AGN candidates are then picked up from this parent sample if they show X-ray fluxes above a threshold of FX ~ 1.5 × 10-17 erg cm-2 s-1 (0.5-2 keV), corresponding to a probability of spurious detections of 2 × 10-4 in the deep X-ray 4 Ms Chandra image. Results. We have found 22 AGN candidates at z > 4 and we have derived the first estimate of the UV luminosity function in the redshift interval 4 < z < 6.5 and absolute magnitude interval - 22.5 ≲ M1450 ≲ -18.5 typical of local Seyfert galaxies. The faint end of the derived luminosity function is about two to four magnitudes fainter at z ~ 4-6 than that derived from previous UV surveys. We estimated ionizing emissivities and hydrogen photoionization rates in the same redshift interval under reasonable assumptions and after discussion of possible caveats, the most important being the large uncertainties involved in the estimate of photometric redshift for sources with featureless, almost power-law SEDs and/or low average escape fraction of ionizing photons from the AGN host galaxies. Both effects could, in principle, significantly reduce the estimated average volume densities and/or ionizing emissivities, especially at the highest redshifts. Conclusions. At z = 4-6.5 we argue that, under reasonable evaluations of possible biases, the probed AGN population can produce photoionization rates consistent with that required to keep the intergalactic medium observed in the Lyman-a forest of high redshift QSO spectra highly ionized, providing an important contribution to the cosmic reionization. [ABSTRACT FROM AUTHOR]

Aims. We aim to constrain the assembly history of high-redshift galaxies and the reliability of UV-based estimates of their physical parameters from an accurate analysis of a unique sample of z ~ 3 Lyman-break galaxies (LBGs). Methods. We analyse 14 LBGs at z ~ 2.8–3.8 constituting the only sample where both a spectroscopic measurement of their metallicity and deep IR observations (CANDELS+HUGS survey) are available. Fixing the metallicity of population synthesis models to the observed values, we determine best-fit physical parameters under different assumptions about the star-formation history (SFH) and also consider the effect of nebular emission. For comparison, we determine the UV slope of the objects, and use it to estimate their SFRUV99 by correcting the UV luminosity. Results. A comparison between star-formation rate (SFR) obtained through SED-fitting (SFRfit) and the SFRUV99 shows that the latter are underestimated by a factor of 2–10, regardless of the assumed SFH. Other SFR indicators (radio, far-IR, X-ray, recombination lines) coherently indicate SFRs a factor of 2–4 larger than SFRUV99 and in closer agreement with SFRfit. This discrepancy is due to the solar metallicity implied by the usual ß - A1600 conversion factor. We propose a refined relation, appropriate for subsolar metallicity LBGs: A1600 = 5.32 + 1.99 * ß. This relation reconciles the dust-corrected UV with the SED-fitting and the other SFR indicators. We show that the fact that z ~ 3 galaxies have subsolar metallicity implies an upward revision by a factor of ~1.5–2 of the global SFRD, depending on the assumptions about the age of the stellar populations. We find very young best-fit ages (10–500 Myr) for all our objects. From a careful examination of the uncertainties in the fit and the amplitude of the Balmer break we conclude that there is little evidence of the presence of old stellar population in at least half of the LBGs in our sample, suggesting that these objects are probably caught during a huge star-formation burst, rather than being the result of a smooth evolution. [ABSTRACT FROM AUTHOR]

Aims. We present a deep multiwavelength imaging survey (UGR) in 3 different fields, Q0933, Q1623, and COSMOS, for a total area of ~1500 arcmin2. The data were obtained with the Large Binocular Camera on the Large Binocular Telescope. Methods. To select our Lyman-break galaxy (LBG) candidates, we adopted the well established and widely used color-selection criterion (U - G vs. G - R). One of the main advantages of our survey is that it has a wider dynamic color range for U-dropout selection than in previous studies. This allows us to fully exploit the depth of our R-band images, obtaining a robust sample with few interlopers. In addition, for 2 of our fields we have spectroscopic redshift information that is needed to better estimate the completeness of our sample and interloper fraction. Results. Our limiting magnitudes reach 27.0(AB) in the R band (5σ) and 28.6(AB) in the U band (1σ). This dataset was used to derive LBG candidates at z ≈ 3. We obtained a catalog with a total of 12 264 sources down to the 50% completeness magnitude limit in the R band for each field. We find a surface density of ~3 LBG candidates arcmin-2 down to R = 25.5, where completeness is ⩾95% for all 3 fields. This number is higher than the original studies, but consistent with more recent samples. [ABSTRACT FROM AUTHOR]

We used Early Release Science (ERS) observations taken with the Wide Field Camera 3 (WFC3) in the GOODS-S field to study the galaxy stellar mass function (GSMF) at 0.6 ≤ z < 4.5. Deep WFC3 near-IR data (for Y as faint as 27.3, J and H as faint as 27.4 AB mag at 5σ), as well as deep KS (as faint as 25.5 at 5σ) Hawk-I band data, provide an exquisite data set with which determine in an unprecedented way the low-mass end of the GSMF, allowing an accurate probe of masses as low as M" ≃ 7.6 × 109 M☉ at z ∼ 3. Although the area used is relatively small (∼33 arcmin2), we found generally good agreement with previous studies on the entire mass range. Our results show that the slope of the faint-end increases with redshift, from α = -1.44± 0.03 at z ∼ 0.8 to α = -1.86± 0.16 at z ∼ 3, although indications exist that it does not steepen further between z ∼ 3 and z ∼ 4. This result is insensitive to any uncertainty in the M" parameter. The steepness of the GSMF faint-end solves the well-known disagreement between the stellar mass density (SMD) and the integrated star-formation history at z > 2. However, we confirm that there appears to be an excess of integrated star formation with respect to the SMD at z < 2, by a factor of ∼2-3. Our comparison of the observations with theoretical predictions shows that the models forecast a greater abundance of low mass galaxies, at least up to z ∼ 3, as well as a dearth of massive galaxies at z ∼ 4 with respect to the data, and that the predicted SMD is generally overestimated at z ≲ 2. [ABSTRACT FROM AUTHOR]

We present the rest-frame Js- and Ks-band luminosity function (LF) of a sample of about 300 galaxies selected in the Hubble Deep Field-South (HDF-S) at (Vega). We use calibrated photometric redshift together with spectroscopic redshift for 25 per cent of the sample. The accuracy reached in the photometric redshift estimate is 0.06 (rms) and the fraction of outliers is 1 per cent. We find that the rest-frame Js-band luminosities obtained by extrapolating the observed Js-band photometry are consistent with those obtained by extrapolating the photometry in the redder H and Ks bands closer to the rest-frame Js, at least up to . Moreover, we find no significant differences among the luminosities obtained with different spectral libraries. Thus, our LF estimate is not dependent either on the extrapolation made on the best-fitting template or on the library of models used to fit the photometry. The selected sample has allowed us to probe the evolution of the LF in the three redshift bins [0; 0.8), [0.8; 1.9) and [1.9; 4) centred at the median redshift and to probe the LF at down to the unprecedented faint luminosities and . We find hints of a rise of the faint-end ( and ) near-infrared (near-IR) LF at : a rise that cannot be probed at higher redshift with our sample. The values of α we estimate are consistent with the local value and do not show any trend with redshift. We do not see evidence of evolution from to suggesting that the population of local bright galaxies was already formed at . In contrast, we clearly detect an evolution of the LF to characterized by a brightening of and by a decline of . To brightens by about 0.4–0.6 mag and decreases by a factor 2–3. This trend persists, even if at a lesser extent, down to in both the Js- and Ks-band LF. The decline of the number density of bright galaxies seen at suggests that a significant fraction of them increase their stellar mass at and that they underwent a strong evolution in this redshift range. On the other hand, this implies also that a significant fraction of local bright/massive galaxies were already in place at . Thus, our results suggest that the assembly of massive galaxies is spread over a large redshift range and that the increase of their stellar mass has been very efficient also at very high redshift at least for a fraction of them. [ABSTRACT FROM AUTHOR]

We discuss the constraints that future photometric and spectroscopic redshift surveys can put on dark energy through the baryon oscillations of the power spectrum. We model the dark energy either with a perfect fluid or a scalar field and take into account the information contained in the linear growth function. We show that the growth function helps to break the degeneracy in the dark energy parameters and reduce the errors onroughly by 30 per cent, making more appealing multicolour surveys based on photometric redshifts. We find that a 200-deg2 spectroscopic survey reachingcan constrainto within, tousing photometric redshifts with an absolute uncertainty of 0.02, and towith an uncertainty of 0.04. In the scalar field case, we show that the slopenof the inverse power-law potential for dark energy can be constrained to(spectroscopic redshifts) or(photometric redshifts), i.e. better than with future ground-based supernovae surveys or cosmic microwave background data. [ABSTRACT FROM AUTHOR]

Abstract Combining a new, increased data set of eight quasi-stellar objects (QSOs) covering the Lyα forest at redshifts 1.5 > z < 3.6 from VLT/UVES observations with previously published results, we have investigated the properties of the Lyα forest at 1.5 < z <4 . With the six QSOs covering the Lyα forest at 1.5 < z < 2.5 , we have extended previous studies in this redshift range. In particular, we have concentrated on the evolution of the line number density and the clustering of the Lyα forest at z≤ 2.5 , where the Lyα forest starts to show some inhomogeneity from sightline to sightline. We have fitted Voigt profiles to the Lyα absorption lines as in previous studies, and have, for two QSOs with z[sub em]∼ 2.4 , fitted Lyα and higher order of Lyman lines down to 3050 Å simultaneously. This latter approach has been taken in order to study the Lyβ forest at z∼ 2.2 and the higher H i column density Lyα forest in the Lyβ forest region. For a given N[sub H I] range, the Lyα forest at 1.5 < z < 4 shows the monotonic evolution, which is governed mainly by the Hubble expansion at this redshift range. In general, the Lyα forest line number density (dn/dz) is best approximated with dn/dz= 6.1(1 +z)[sup 2.47 ± 0.18] for the H i column density N[sub H I]= 10[sup 13.64-17] cm[sup -2] at 1.5 < z < 4 . When the results at 0 < z < 1.5 from Hubble Space Telescope (HST) observations are combined, the slow-down in the number density evolution occurs at z < 1.5 . For higher column density clouds at N[sub Hi] > 10[sup 14] cm[sup -2] , there is a variation in the line number density from sightline to sightline at z < 2.5 . This variation is stronger for higher column density systems, probably due to more gravitationally evolved structures at lower z. The mean H i opacity is at 1.5 < z < 4 . HST observations show evidence for slower evolution of at z < 1 . For N[sub Hi]= 10[sup 12.5–15] cm[sup -2] , the differential column density distribution function, f(N[sub Hi]) , can be best fitted by f(N[sub HI]∝N[sub Hi][sup -β] with β≈ 1.5 for 1.5 < z < 4 . When combined with HST observations, the exponent β increases as z decreases at 0 < z < 4 for N[sub Hi]= 10[sup 13–17] cm[sup -2] . The correlation strength of the step optical depth correlation function shows the strong evolution from = 3.3 to = 2.1 , although there is a large scatter along different sightlines. The analyses of the Lyβ forest at z∼ 2.2 are, in general, in good agreement with those of the Lyα forest. [ABSTRACT FROM AUTHOR]

We present an analysis of the evolution of galaxy clustering in the redshift interval in the Hubble Deep Field South (HDF-South). The HST optical data are combined with infrared ISAAC/VLT observations, and photometric redshifts are used for all the galaxies brighter than . The clustering signal is obtained in different redshift bins using two different approaches: a standard one, which uses the best redshift estimate of each object, and a second one, which takes into account the redshift probability function of each object. This second method makes it possible to improve the information in the redshift intervals where contamination from objects with insecure redshifts is important. With both methods, we find that the clustering strength up to in the HDF-South is consistent with the previous results in the HDF-North. Whereas at redshift lower than the HDF galaxy population is un/anti-biased with respect to the underlying dark matter, at high redshift the bias increases up to , depending on the cosmological model. These results support previous claims that, at high redshift, galaxies are preferentially located in massive haloes, as predicted by the biased galaxy formation scenario. In order to quantify the impact of cosmic errors on our analyses, we have used analytical expressions from Bernstein . Once the behaviour of higher-order moments is assumed, our results show that errors in the clustering measurements in the HDF surveys are indeed dominated by pure shot-noise in most regimes, as assumed in our analysis. We also show that future observations with instruments like the Advanced Camera on HST will improve the signal-to-noise ratio by at least a factor of 2, as a consequence, more detailed analyses of the errors will be required. In fact, pure shot-noise will give a smaller contribution with respect to other sources of errors, such as finite volume effects or non-Poissonian discreteness effects. [ABSTRACT FROM AUTHOR]

We report the discovery of the optical counterpart of the 12.3-s transient X-ray pulsar GS 0834-43. We reanalysed archival ROSAT PSPC observations of GS 0834-43, obtaining two new refined positions, ∼14 and ∼18 arcsec away from the previously published one, and a new spin period measurement. Based on these results we carried out optical and infrared (IR) follow-up observations. Within the new error circles, we found a relatively faint (V=20.1) early-type reddened star (V-R=2.24). The optical spectrum shows a strong Hα emission line. The IR observations of the field confirm the presence of an IR excess for the Hα-emitting star (K′=11.4, J-K′=1.94), which is likely surrounded by a conspicuous circumstellar envelope. Spectroscopic and photometric data indicate a B0–2 V–IIIe spectral type star located at a distance of 3–5 kpc and confirm the Be-star/X-ray binary nature of GS 0834-43. [ABSTRACT FROM AUTHOR]

The evolution of galaxy clustering from z=0 to z≃4.5 is analysed using the angular correlation function and the photometric redshift distribution of galaxies brighter than I[sub AB] &les; 28.5 in the Hubble Deep Field North. The reliability of the photometric redshift estimates is discussed on the basis of the available spectroscopic redshifts, comparing different codes and investigating the effects of photometric errors. The redshift bins in which the clustering properties are measured are then optimized to take into account the uncertainties of the photometric redshifts. The results show that the comoving correlation length r[sub 0] has a small decrease in the range 0&lsim;z&lsim;1 followed by an increase at higher z. We compare these results with the theoretical predictions of a variety of cosmological models belonging to the general class of Cold Dark Matter scenarios, including Einstein–de Sitter models, an open model and a flat model with non-zero cosmological constant. Comparison with the expected mass clustering evolution indicates that the observed high-redshift galaxies are biased tracers of the dark matter with an effective bias b strongly increasing with redshift. Assuming an Einstein–de Sitter universe, we obtain b≃2.5 at z≃2 and b≃5 at z≃4. These results support theoretical scenarios of biased galaxy formation in which the galaxies observed at high redshift are preferentially located in more massive haloes. Moreover, they suggest that the usual parameterization of the clustering evolution as ξ(r,z)=ξ(r,0)(1+z)[sup -(3+ε)] is not a good description for any value of ε. Comparison of the clustering amplitudes that we measured at z≃3 with those reported by Adelberger et al. and Giavalisco et al., based on a different selection, suggests that the clustering depends on the abundance of the objects: more abundant objects are less clustered, as expected in the paradigm of hierarchical galaxy formation. The strong clustering and high bias measured at z≃3 are consistent with the expected density of massive haloes predicted in the frame of the various cosmologies considered here. At z≃4, the strong clustering observed in the Hubble Deep Field requires a significant fraction of massive haloes to be already formed by that epoch. This feature could be a discriminant test for the cosmological parameters if confirmed by future observations. [ABSTRACT FROM AUTHOR]

BeppoSAX observed the Seyfert 1.9 galaxy NGC 4258 in 1998 December, when its 2-10 keV luminosity was about 1041 ergs s-1. Large amplitude (100%) variability is observed in the 3-10 keV band on timescales of a few tens of thousands of seconds, while variability of ~20% is observed on timescales as short as 1 hr. The nuclear component is visible above 2 keV only, being obscured by a column density of (9.5 ± 1.2) × 1022 cm-2; this component is detected at up to 70 keV with a signal-to-noise ratio of gsim3 and with a steep power-law energy spectral index of αE = 1.11 ± 0.14. Bremsstrahlung emission for the 2-70 keV X-ray luminosity, as expected in advection-dominated accretion flow models with strong winds, is ruled out by the data. The ratio between the nuclear radio (22 GHz) luminosity and the X-ray (5 keV) luminosity is consistent with that of radio-quiet quasars and Seyfert galaxies. X-ray variability, spectral shape, and radio/X-ray and near-IR/X-ray luminosity ratios suggest that the nucleus of NGC 4258 could be a scaled down version of a Seyfert nucleus and that the X-ray nuclear luminosity can be explained in terms of Comptonization in a hot corona. The soft (E lesssim 2 keV) X-ray emission is complex. There are at least two thermal-like components with temperatures of 0.6 ± 0.1 keV and gsim1.3 keV. The cooler (L0.1-2.4 keV~ 1040 ergs s-1) component is probably associated with the jet, resolved in X-rays by the ROSAT HRI (Cecil et al. 1994). The luminosity of the second component, which can be modeled equally well by an unobscured power-law model with αE = 0.2img1.gif, is L0.1-2.4 keV~ 7 × 1039 ergs s-1, consistent with that expected from discrete X-ray sources (binaries and supernova remnants) in the host galaxy. Observations of NGC 4258 and other maser active galactic nuclei (AGNs) show strong nuclear X-ray absorption. We propose that this large column of gas might be responsible for shielding the regions of water maser emission from X-ray illumination. So a large column density absorbing gas may be a necessary property of masing AGNs., Astronomy

We included 1666 twin pregnancies (3332 fetuses), with 1114 pregnancies (2228 fetuses) before June 2013 and 552 pregnancies (1104 fetuses) after June 2016, in the analysis. Implementation of NICE guidance was associated with a significant reduction (> 70%) in stillbirth in twin pregnancies, which was even higher in monochorionic twin pregnancies. [Extracted from the article]