Abstract. Development of fundamental physics relies on the constancy of various fundamental quantities such as the finestructure constant. Detecting or constraining the possible time variations of these fundamental physical quantities is an important step toward a complete understanding of basic physics. High-quality absorption lines seen in the spectra of distant QSOs allow one to probe time variations of several of these quantities. Here we present the results from a detailed manymultiplet analysis, to detect the possible variation of the fine-structure constant, performed using high signal-to-noise ratio, (∼70 per pixel), high spectral resolution (R ≥ 45 000) observations of 23 Mg  systems detected toward 18 QSOs in the redshift range 0.4 ≤ z ≤ 2.3 obtained using UVES at the VLT. We validate our procedure and define the selection criteria that will avoid possible systematics using a detailed analysis of a simulated data set. The spectra of Mg  doublets and Fe  multiplets are generated considering variations in α and specifications identical to that of our UVES spectra. We show that our Voigt profile fitting code recovers the variation in α very accurately when we use single component systems and multiple-component systems that are not heavily blended. Spurious detections are frequently seen when we use heavily blended systems or systems with very weak lines. Thus we avoided these system while analysing the UVES data. To make the analysis transparent and accessible to the community for critical scrutiny, all the steps involved in the analysis are presented in detail. The weighted mean value of the variation in α obtained from our analysis over the redshift range 0.4 ≤ z ≤ 2.3 is ∆α/α = (−0.06 ± 0.06) × 10 −5 . The median redshift of our sample is 1.55 and corresponds to a look-back time of 9.7 Gyr in the most favored cosmological model today. The 3σ upper limit on the time variation of α is −2.5 × 10 −16 yr −1 ≤ (∆α/α∆t) ≤ +1.2 × 10 −16 yr −1 . To our knowledge this is the strongest constraint from quasar absorption line studies to till date.

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We present a new catalog of narrow-line Seyfert 1 (NLSy1) galaxies from the Sloan Digital Sky Survey Data Release 12 (SDSS DR12). This was obtained by a systematic analysis through modeling of the continuum and emission lines of the spectra of all the 68,859 SDSS DR12 objects that are classified as "QSO" by the SDSS spectroscopic pipeline with z < 0.8 and a median signal-to-noise ratio (S/N) > 2 pixel −1 . This catalog contains a total of 11,101 objects, which is about five times larger than the previously known NLSy1 galaxies. Their monochromatic continuum luminosity at 5100Å is found to be strongly correlated with Hβ, Hα and [O III] emission line luminosities. The optical Fe II strength in NLSy1 galaxies is about two times larger than the broad-line Seyfert 1 (BLSy1) galaxies. About 5% of the catalog sources are detected in FIRST survey. The Eddington ratio (ξ Edd ) of NLSy1 galaxies has an average of log ξ Edd of −0.34, much higher than −1.03 found for BLSy1 galaxies. Their black hole masses (M BH ) have an average log M BH of 6.9 M , which is less than BLSy1 galaxies, which have an average of log M BH of 8.0 M . The M BH of NLSy1 galaxies is found to be correlated with their host galaxy velocity dispersion. Our analysis suggests that geometrical effects playing an important role in defining NLSy1 galaxies and their M BH deficit is perhaps due to their lower inclination compared to BLSy1 galaxies.

Abstract. A new limit on the possible cosmological variation of the proton-to-electron mass ratio µ = m p /m e is estimated by measuring wavelengths of H 2 lines of Lyman and Werner bands from two absorption systems at z abs = 2.5947 and 3.0249 in the spectra of quasars Q 0405−443 and Q 0347−383, respectively. Data are of the highest spectral resolution (R = 53 000) and S/N ratio (30÷70) for this kind of study. We search for any correlation between z i , the redshift of observed lines, determined using laboratory wavelengths as references, and K i , the sensitivity coefficient of the lines to a change of µ, that could be interpreted as a variation of µ over the corresponding cosmological time. We use two sets of laboratory wavelengths, the first one, Set (A) (Abgrall et al. 1993, J. Mol. Spec., 157, 512), based on experimental determination of energy levels and the second one, Set (P) (Philip et al. 2004, Can. J. Chem., 82, 713), based on new laboratory measurements of some individual rest-wavelengths. We find ∆µ/µ = (3.05 ± 0.75) × 10 −5 for Set (A), and ∆µ/µ = (1.65 ± 0.74) × 10 −5 for Set (P). The second determination is the most stringent limit on the variation of µ over the last 12 Gyr ever obtained. The correlation found using Set (A) seems to show that some amount of systematic error is hidden in the determination of energy levels of the H 2 molecule.

The high Himalayan mountains in the north of India are important sources for generating and maintaining the climate over the entire northern belt of the Indian subcontinent. They also influence extreme weather events, such as the western disturbances over the region during winter. The work presented here describes some current trends in weather and climate over the western Himalaya and suggests some possible explanations in the context of climate change. The work also shows how the special features of Indian orography in the western Himalaya affect climate change in the long term, changing the pattern of precipitation over the region. Data analysis of different ranges of the western Himalaya shows significant variations in temperature and snowfall trends in the past few decades. Possible explanations for the changing climate over the western Himalaya are proposed, in terms of variations in cloudiness. The possible effects of climate change on the number of snowfall days and the occurrences of western disturbances over the western Himalaya are also analysed.

Context. Line asymmetries are generated by convective Doppler shifts in stellar atmospheres, especially in metal-poor stars, where convective motions penetrate to higher atmospheric levels. Such asymmetries are usually neglected in abundance analyses. The determination of the 6 Li/ 7 Li isotopic ratio is prone to suffering from such asymmetries, as the contribution of 6 Li is a slight blending reinforcement of the red wing of each component of the corresponding 7 Li line, with respect to its blue wing. Aims. The present paper studies the halo star HD 74000 and estimates the impact of convection-related asymmetries on the Li isotopic ratio determination. Methods. Two methods are used to meet this aim. The first, which is purely empirical, consists in deriving a template profile from another element that can be assumed to originate in the same stellar atmospheric layers as Li i, producing absorption lines of approximately the same equivalent width as individual components of the 7 Li i resonance line. The second method consists in conducting the abundance analysis based on NLTE line formation in a 3D hydrodynamical model atmosphere, taking into account the effects of photospheric convection. Results. The results of the first method show that the convective asymmetry generates an excess absorption in the red wing of the 7 Li absorption feature that mimics the presence of 6 Li at a level comparable to the hitherto published values. This opens the possibility that only an upper limit on 6 Li/ 7 Li has thus far been derived. The second method confirms these findings. Conclusions. From this work, it appears that a systematic reappraisal of former determinations of 6 Li abundances in halo stars is warranted.

We report the results of intensive X-ray, UV and optical monitoring of the Seyfert 1 galaxy NGC 4593 with Swift. There is no intrinsic flux-related spectral change in the the variable components in any band with small apparent variations due only to contamination by a second constant component, possibly a (hard) reflection component in the X-rays and the (red) host galaxy in the UV/optical bands. Relative to the shortest wavelength band, UVW2, the lags of the other UV and optical bands are mostly in agreement with the predictions of reprocessing of high energy emission from an accretion disc. The U-band lag is, however, far larger than expected, almost certainly because of reprocessed Balmer continuum emission from the more distant broad line region gas. The UVW2 band is well correlated with the X-rays but lags by ∼ 6× more than expected if the UVW2 results from reprocessing of X-rays on the accretion disc. However, if the lightcurves are filtered to remove variations on timescales > 5d, the lag approaches the expectation from disc reprocessing. MEMEcho analysis shows that direct X-rays can be the driver of most of the variations in the UV/optical bands as long as the response functions for those bands all have long tails (up to 10d) in addition to a strong peak (from disc reprocessing) at short lag (< 1 d). We interpret the tails as due to reprocessing from the surrounding gas. Comparison of X-ray to UVW2 and UVW2 to V-band lags for 4 AGN, including NGC 4593, shows that all have UVW2 to V-band lags which exceed the expectations from disc resprocessing by ∼ < 2. However the X-ray to UVW2 lags are, mostly, in greater excess from the expectations from disc reprocessing and differ between AGN. The largest excess is in NGC 4151. Absorption and scattering may be affecting X-ray to UV lags.

We present a method for studying the proximity effect and the density structure around redshift z= 2–3 quasars. It is based on the probability distribution of Lyman α pixel optical depths and its evolution with redshift. We validate the method using mock spectra obtained from hydrodynamical simulations, and then apply it to a sample of 12 bright quasars at redshifts 2–3 observed with the Ultraviolet and Visible Echelle Spectrograph (UVES) at the VLT‐UT2 Kueyen European Southern Observatory telescope. These quasars do not show signatures of associated absorption and have a mean monochromatic luminosity of 5.4 × 1031 h−2 erg s−1 Hz−1 at the Lyman limit. The observed distribution of optical depth within 10 h−1 Mpc from the quasi‐stellar object is statistically different from that measured in the general intergalactic medium at the same redshift. Such a change will result from the combined effects of the increase in photoionization rate above the mean ultraviolet‐background due to the extra ionizing photons from the quasar radiation (proximity effect), and the higher density of the intergalactic medium if the quasars reside in overdense regions (as expected from biased galaxy formation). The first factor decreases the optical depth whereas the second increases the optical depth, but our measurement cannot distinguish a high background from a low overdensity. An overdensity of the order of a few is required if we use the amplitude of the ultraviolet‐background inferred from the mean Lyman α opacity. If no overdensity is present, then we require the ultraviolet‐background to be higher, and consistent with the existing measurements based on standard analysis of the proximity effect.