We analyzed the near-infrared to UV data of 16 quasars with redshifts ranging from 0.71 <z< 2.13 to investigate dust extinction properties. The sample presented in this work was obtained from the ...High AV Quasar (HAQ) survey. The quasar candidates were selected from the Sloan Digital Sky Survey (SDSS) and the UKIRT Infrared Deep Sky Survey (UKIDSS), and follow-up spectroscopy was carried out at the Nordic Optical Telescope (NOT) and the New Technology Telescope (NTT). To study dust extinction curves intrinsic to the quasars, we selected 16 cases from the HAQ survey for which the Small Magellanic Cloud (SMC) law could not provide a good solution to the spectral energy distributions (SEDs). We derived the extinction curves using the Fitzpatrick & Massa (1986, ApJ, 307, 286, FM) law by comparing the observed SEDs to a combined previously published quasar template. The derived extinction, AV, ranges from 0.2–1.0 mag. All the individual extinction curves of our quasars are steeper (RV = 2.2–2.7) than that of the SMC, with a weighted mean value of RV = 2.4. We derived an average quasar extinction curve for our sample by simultaneously fitting SEDs by using the weighted mean values of the FM law parameters and a varying RV. The entire sample is well fit with a single best-fit value of RV = 2.2 ± 0.2. The average quasar extinction curve deviates from the steepest Milky Way and SMC extinction curves at a confidence level ≳95%. Such steep extinction curves suggest that a significant population of silicates is involved in producing small dust grains. Another possibility might be that the large dust grains may have been destroyed by the activity of the nearby active galactic nuclei (AGN), resulting in steep extinction curves.
A scaling relation has recently been suggested to combine the galaxy mass–metallicity (MZ) relation with metallicities of damped Lyman α systems (DLAs) in quasar spectra. Based on this relation the ...stellar masses of the absorbing galaxies can be predicted. We test this prediction by measuring the stellar masses of 12 galaxies in confirmed DLA absorber–galaxy pairs in the redshift range 0.1 < z < 3.2. We find an excellent agreement between the predicted and measured stellar masses over three orders of magnitude, and we determine the average offset 〈C
M/H〉 = 0.44 ± 0.10 between absorption and emission metallicities. We further test if C
M/H could depend on the impact parameter and find a correlation at the 5.5σ level. The impact parameter dependence of the metallicity corresponds to an average metallicity difference of −0.022 ± 0.004 dex kpc−1. By including this metallicity versus impact parameter correlation in the prescription instead of C
M/H, the scatter reduces to 0.39 dex in log M
*. We provide a prescription on how to calculate the stellar mass (
$M_*^{\mathrm{DLA}}$
) of the galaxy when both the DLA metallicity and DLA galaxy impact parameter is known. We demonstrate that DLA galaxies follow the MZ relation for luminosity-selected galaxies at z = 0.7 and 2.2 when we include a correction for the correlation between impact parameter and metallicity.
Machine vision based inspection systems are in great focus nowadays for quality control applications. The proposed work presents a novel approach for classification of wood knot defects for an ...automated inspection. The proposed technique utilizes gray level co-occurrence matrix and laws texture energy measures as texture feature extractors and feed-forward back-propagation neural network as classifier. The proposed work involves the comparison of gray level co-occurrence matrix based features with laws texture energy measures based features. Firstly it takes contrast, correlation, energy and homogeneity as input parameters to a feed-forward back propagation neural network to predict wood defects and then it take energy calculated from laws texture energy measures based energy maps as input feature to a feed-forward back propagation neural network. Mean Square Error (MSE) for training data is found to be 0.0718 and 90.5% overall average classification accuracy is achieved when laws texture energy measures based features are used as input to the neural network as compared to gray level co-occurrence matrix based input features where MSE for training data is found to be 0.10728 and 84.3% overall average classification accuracy is achieved. The proposed technique shows promising results to classify wood defects using a feed forward back-propagation neural network.
Damped absorbers, seen in the spectra of background quasars, are unique probes to select Hi-rich galaxies. These galaxies allow one to estimate the neutral gas mass over cosmological scales. The ...neutral gas mass is a possible indicator of gas consumption as star formation proceeds. The damped Ly alpha absorbers and sub-DLAs are believed to contain a large fraction of neutral gas mass in the Universe. In Paper I of the series, we presented the results of a search for DLAs and sub-DLAs in the European Southern Observatory (ESO) Ultraviolet Visual Echelle Spectrograph (UVES) advanced data products dataset of 250 quasars. The complete sample shows that sub-DLAs contribute 8-20% to the total omega g from 1.5 lessthan zeta lessthan 5.0. In agreement with previous studies, no evolution of omega g was observed from low to high redshift, suggesting that star formation alone cannot explain this non-evolution and replenishment of gas and that recombination of ionized gas is needed.
A scaling relation has recently been suggested to combine the galaxy mass-metallicity (MZ) relation with metallicities of damped Lyman alpha systems (DLAs) in quasar spectra. Based on this relation ...the stellar masses of the absorbing galaxies can be predicted. We test this prediction by measuring the stellar masses of 12 galaxies in confirmed DLA absorber-galaxy pairs in the redshift range 0.1 < z < 3.2. We find an excellent agreement between the predicted and measured stellar masses over three orders of magnitude, and we determine the average offset ... between absorption and emission metallicities. We further test if ... could depend on the impact parameter and find a correlation at the 5.5.. level. The impact parameter dependence of the metallicity corresponds to an average metallicity difference of -0.022 plus or minus 0.004 dex kpc... By including this metallicity versus impact parameter correlation in the prescription instead of CM/H, the scatter reduces to 0.39 dex in log M... We provide a prescription on how to calculate the stellar mass (...) of the galaxy when both the DLA metallicity and DLA galaxy impact parameter is known. We demonstrate that DLA galaxies follow the MZ relation for luminosity-selected galaxies at z = 0.7 and 2.2 when we include a correction for the correlation between impact parameter and metallicity. (ProQuest: ... denotes formulae/symbols omitted.)
Context. The gamma-ray bursts hosts (GRBHs) are excellent targets to study the extinction properties of dust and its effects on the global emission of distant galaxies. The dust extinction curve is ...measured along the GRB afterglow line of sight and the analysis of the spectral energy distribution (SED) of the host galaxy gives access to the global dust attenuation of the stellar light. Aims. In this pilot study we gather information on dust extinction in GRBHs to compare the properties of the extinction curve to those of the dust obscuration affecting the total stellar light of the host galaxy. Assuming the extinction curve to be representative of the dust properties, we aim to investigate which dust-stars geometries and local dust distribution in the inter stellar medium (ISM) can reproduce the observed attenuation curve. Methods. We selected a sample of 30 GRBs for which the extinction curve along the GRB afterglow line-of-sight (l.o.s.) is measured in the rest-frame ultraviolet (UV) up to optical and we analysed the properties of the extinction curve as a function of the host galaxy properties. From these 30 GRBs, we selected seven GRBHs with a good rest-frame UV to near-infrared (NIR) spectral coverage for the host. The attenuation curve was derived by fitting the SEDs of the GRBH sample with the CIGALE SED fitting code. Different star formation histories (SFH) were studied to recover the star formation rates (SFR) derived using Hα luminosities. Implications for the dust-stars geometries in the ISM are inferred by a comparison with radiative transfer simulations. Results. The most extinguished GRBs are preferentially found in the more massive hosts and the UV bump is preferentially found in the most extinguished GRB l.o.s. Five out of seven hosts are best fitted with a recent burst of star formation, leading to lower stellar mass estimates than previously found. The average attenuation in the host galaxies is about 70% of the amount of extinction along the GRB l.o.s. We find a great variety in the derived attenuation curves of GRBHs, the UV slope can be similar, flatter or even steeper than the extinction curve slope. Half of the attenuation curves are consistent with the Calzetti attenuation law and there is evidence of a UV bump in only one GRBH. We find that the flatter (steeper) attenuation curves are found in galaxies with the highest (lowest) SFR and stellar masses. The comparison of our results with radiative transfer simulations leads to a uniform distribution of dust and stars in a very clumpy ISM for half the GRBHs and various dust-stars geometries for the second half of the sample.
The circumgalactic medium (CGM) can be probed through the analysis of absorbing systems in the line of sight to bright background quasars. We present measurements of the metallicity of a new sample ...of 15 sub-damped Lyman α absorbers (sub-DLAs, defined as absorbers with 19.0 < log N(H I) < 20.3) with redshift 0.584 ≤ z
abs ≤ 3.104 from the ESO Ultra-Violet Echelle Spectrograph (UVES) Advanced Data Products Quasar Sample (EUADP). We combine these results with other measurements from the literature to produce a compilation of metallicity measurements for 92 sub-DLAs as well as a sample of 362 DLAs. We apply a multi-element analysis to quantify the amount of dust in these two classes of systems. We find that either the element depletion patterns in these systems differ from the Galactic depletion patterns or they have a different nucleosynthetic history than our own Galaxy. We propose a new method to derive the velocity width of absorption profiles, using the modelled Voigt profile features. The correlation between the velocity width ΔV
90 of the absorption profile and the metallicity is found to be tighter for DLAs than for sub-DLAs. We report hints of a bimodal distribution in the Fe/H metallicity of low redshift (z < 1.25) sub-DLAs, which is unseen at higher redshifts. This feature can be interpreted as a signature from the metal-poor, accreting gas and the metal-rich, outflowing gas, both being traced by sub-DLAs at low redshifts.
Abstract
We present the first major release of data from the SAMI Galaxy Survey. This data release focuses on the emission-line physics of galaxies. Data Release One includes data for 772 galaxies, ...about 20 per cent of the full survey. Galaxies included have the redshift range 0.004 < z < 0.092, a large mass range (7.6 < log M*/ M⊙ < 11.6), and star formation rates of ∼10−4 to ∼101M⊙ yr−1. For each galaxy, we include two spectral cubes and a set of spatially resolved 2D maps: single- and multi-component emission-line fits (with dust-extinction corrections for strong lines), local dust extinction, and star formation rate. Calibration of the fibre throughputs, fluxes, and differential atmospheric refraction has been improved over the Early Data Release. The data have average spatial resolution of 2.16 arcsec (full width at half-maximum) over the 15 arcsec diameter field of view and spectral (kinematic) resolution of R = 4263 (σ = 30 km s−1) around H α. The relative flux calibration is better than 5 per cent, and absolute flux calibration has an rms of 10 per cent. The data are presented online through the Australian Astronomical Observatory's Data Central.
We present a detailed analysis of a red quasar at z = 2.32 with an intervening damped Lyman α absorber (DLA) at z = 2.13. Using high-quality data from the X-shooter spectrograph at ESO Very Large ...Telescope, we find that the absorber has a metallicity consistent with solar. We observe strong C i and H2 absorption indicating a cold, dense absorbing medium. Partial coverage effects are observed in the C i lines, from which we infer a covering fraction of 27 ± 6 per cent and a physical diameter of the cloud of 0.1 pc. From the covering fraction and size, we estimate the size of the background quasar's broad line region. We search for emission from the DLA counterpart in optical and near-infrared imaging. No emission is observed in the optical data. However, we see tentative evidence for a counterpart in the H- and K′-band images. The DLA shows high depletion (as probed by Fe/Zn = −1.22) indicating that significant amounts of dust must be present in the DLA. By fitting the spectrum with various dust reddened quasar templates we find a best-fitting amount of dust in the DLA of A(V)DLA = 0.28 ± 0.01|stat ± 0.07|sys. We conclude that dust in the DLA is causing the colours of this intrinsically very luminous background quasar to appear much redder than average quasars, thereby not fulfilling the criteria for quasar identification in the Sloan Digital Sky Survey. Such chemically enriched and dusty absorbers are thus under-represented in current samples of DLAs.
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