Strong Gravitational Lensing by the Super-massive cD Galaxy in Abell 3827

We have discovered strong gravitational lensing features in the core of the nearby cluster Abell 3827 by analyzing Gemini South GMOS images. The most prominent strong lensing feature is a highly-magnified, ring-shaped configuration of four images around the central cD galaxy. GMOS spectroscopic analysis puts this source at z~0.2. Located ~20" away from the central galaxy is a secondary tangential arc feature which has been identified as a background galaxy with z~0.4. We have modeled the gravitational potential of the cluster core, taking into account the mass from the cluster, the BCG and other galaxies. We derive a total mass of (2.7 +- 0.4) x 10^13 Msun within 37 h^-1 kpc. This mass is an order of magnitude larger than that derived from X-ray observations. The total mass derived from lensing data suggests that the BCG in this cluster is perhaps the most massive galaxy in the nearby Universe.Comment: Minor typo corrections introduced. Journal reference and DOI added. 5 pages, 3 figures (2 in colors), 2 table

Multiple sclerosis - symptoms, diagnosis and treatment

Neðst á síðunni er hægt að nálgast greinina í heild sinni með því að smella á hlekkinn View/OpenMultiple sclerosis is an inflammatory disease of the central nervous system and a common cause of disability among young people. MS is thought to be an autoimmune disease involving both inheritance and environmental factors. The disease is characterized by relapses and the symptoms and course are highly variable. The diagnosis is primarily clinical and supported by results of diagnostic studies. The importance of timely diagnosis has increased with the availability of effective treatment. The purpose of this article is to review symptoms, signs, diagnosis and treatment of multiple sclerosis.Multiple sclerosis (MS) er bólgusjúkdómur í miðtaugakerfinu og algeng orsök fötlunar hjá ungu fólki. MS er talinn vera sjálfsofnæmissjúkdómur sem tengist samspili erfða og umhverfis. Sjúkdómurinn kemur í köstum og geta einkenni og gangur hans verið margbreytilegur. Greining byggir á sjúkdómseinkennum og styðst við niðurstöður rannsókna. Mikilvægi skjótrar greiningar hefur aukist með tilkomu áhrifaríkrar meðferðar. Tilgangur þessarar greinar er að rekja algengustu einkenni, greiningu og meðferð við MS sjúkdómi

The effect of maternal weight on pregnancy outcome

Neðst á síðunni er hægt að nálgast greinina í heild sinni með því að smella á hlekkinn Skoða/Opna(view/open)OBJECTIVE: To examine the frequency of adverse outcome during pregnancy and delivery and neonatal complications among normal weight, overweight and obese women at the beginning of pregnancy. MATERIAL AND METHODS: The study is a retrospective cohort study of 600 women, divided in 3 groups on the basis of maternal body mass index (BMI) at the beginning of pregnancy; 300 normal weight women (BMI 19.0-24.9), 150 overweight women (BMI 25.0-29.9) and 150 obese women (BMI ≥ 30). Maternal and neonatal complications were compared between groups. RESULTS: Obese women have a significantly increased risk of; essential hypertension prior to pregnancy (p<0.001), developing gestational hypertension (p=0.03), pre-eclampsia (p=0.007), gestational diabetes (p<0.001), musculoskeletal symptoms (p=0.04), requiring induction of labour (pp=0.006) and being delivered by cesarean section (p<0.001), both emergent (pp=0.012) and elective (pp=0.008) compared to mothers of normal weight and overweight. Neonates of obese mothers have significantly higher birth weight (pp=0.004), larger head circumference (p<0.001) and are more likely to require admission to neonatal ward compared with neonates of normal weight and overweight mothers (pp=0.004). CONCLUSIONS: Obesity carries a significant risk to maternal and neonatal health. During pregnancy maternal complications are increased causing adverse effects for both mother and infant. Women of reproductive age need counselling regarding the adverse effects of obesity on pregnancy outcome.Tilgangur: Að kanna tíðni fylgikvilla á meðgöngu, í fæðingu og hjá nýburum kvenna í kjörþyngd, of þungra og of feitra við upphaf meðgöngu. Þátttakendur og aðferðir: Rannsóknin er afturskyggn og tilfellaviðmiðuð. Upplýsingum um þyngd við upphaf meðgöngu var safnað hjá 600 konum; þar af voru 300 í kjörþyngd (þyngdarstuðull (ÞS) 19,0-24,9), 150 of þungar (ÞS 25,0-29,9) og 150 of feitar (ÞS ³30). Tíðni fylgikvilla var borin saman milli hópanna. Niðurstöður: Of feitar konur eru líklegri til að hafa langvinnan háþrýsting (p<0,001) fyrir þungun, fá meðgönguháþrýsting (p=0,03), meðgöngueitrun (p=0,007), meðgöngusykursýki (p<0,001), einkenni frá stoðkerfi (p=0,04), að framkalla þurfi fæðingu (p=0,006) og að fæða með keisaraskurði (p<0,001), bæði bráða- (p=0,012) og valkeisaraskurði (p=0,008), samanborið við mæður í kjörþyngd og ofþyngd. Nýburar of feitra kvenna eru þyngri (p=0,004), með stærra höfuðummál (p<0,001) og eru oftar lagðir inn á nýburagjörgæslu (p=0,004) en börn mæðra í kjörþyngd og ofþyngd. Ályktun:Offita hefur óæskileg áhrif á heilsufar verðandi mæðra og barna þeirra. Áhrifin koma fram á meðgöngu, í fæðingu og hjá börnum þeirra. Mikilvægt er að konur á barneignaraldri fái upplýsingar um hvaða áhrif offita hefur á meðgöngu, fæðingu og nýbura

Measurement of a Metallicity Gradient in a z=2 Galaxy: Implications for Inside-Out Assembly Histories

We present near-infrared imaging spectroscopy of the strongly-lensed z=2.00 galaxy SDSS J120601.69+514227.8 (`the Clone arc'). Using OSIRIS on the Keck 2 telescope with laser guide star adaptive optics, we achieve resolved spectroscopy with 0.20 arcsecond FWHM resolution in the diagnostic emission lines [O III], Halpha, and [N II]. The lensing magnification allows us to map the velocity and star formation from Halpha emission at a physical resolution of ~300 pc in the galaxy source plane. With an integrated star formation rate of ~50 Msun/yr, the galaxy is typical of sources similarly studied at this epoch. It is dispersion-dominated with a velocity gradient of +/- 80 km/s and average dispersion sigma = 85 km/s; the dynamical mass is 2.4 \times 10^{10} Msun within a half-light radius of 2.9 kpc. Robust detection of [N II] emission across the entire OSIRIS field of view enables us to trace the gas-phase metallicity distribution with 500 pc resolution. We find a strong radial gradient in both the [N II]/Halpha and [O III]/Halpha ratios indicating a metallicity gradient of -0.27 +/- 0.05 dex/kpc with central metallicity close to solar. We demonstrate that the gradient is seen independently in two multiple images. While the physical gradient is considerably steeper than that observed in local galaxies, in terms of the effective radius at that epoch, the gradient is similar. This suggests that subsequent growth occurs in an inside-out manner with the inner metallicity gradient diminished over time due to radial mixing and enrichment from star formation.Comment: 6 pages, 4 figures, accepted by ApJ Letter

The Dark Matter Distribution in Abell 383: Evidence for a Shallow Density Cusp from Improved Lensing, Stellar Kinematic and X-ray Data

We extend our analyses of the dark matter (DM) distribution in relaxed clusters to the case of Abell 383, a luminous X-ray cluster at z=0.189 with a dominant central galaxy and numerous strongly-lensed features. Following our earlier papers, we combine strong and weak lensing constraints secured with Hubble Space Telescope and Subaru imaging with the radial profile of the stellar velocity dispersion of the central galaxy, essential for separating the baryonic mass distribution in the cluster core. Hydrostatic mass estimates from Chandra X-ray observations further constrain the solution. These combined datasets provide nearly continuous constraints extending from 2 kpc to 1.5 Mpc in radius, allowing stringent tests of results from recent numerical simulations. Two key improvements in our data and its analysis make this the most robust case yet for a shallow slope \beta of the DM density profile \rho_DM ~ r^-\beta on small scales. First, following deep Keck spectroscopy, we have secured the stellar velocity dispersion profile to a radius of 26 kpc for the first time in a lensing cluster. Secondly, we improve our previous analysis by adopting a triaxial DM distribution and axisymmetric dynamical models. We demonstate that in this remarkably well-constrained system, the logarithmic slope of the DM density at small radii is \beta < 1.0 (95% confidence). An improved treatment of baryonic physics is necessary, but possibly insufficient, to reconcile our observations with the recent results of high-resolution simulations.Comment: Accepted to ApJ Letter

Analyzing the Flux Anomalies of the Large-Separation Lensed Quasar SDSS J1029+2623

Using a high resolution radio image, we successfully resolve the two fold image components B and C of the quasar lens system SDSS J1029+2623. The flux anomalies associated with these two components in the optical regime persist, albeit less strongly, in our radio observations, suggesting that the cluster must be modeled by something more than a single central potential. We argue that placing substructure close to one of the components can account for a flux anomaly with negligible changes in the component positions. Our best fit model has a substructure mass of ~10^8 solar masses up to the mass-sheet degeneracy, located roughly 0.1 arcsecs West and 0.1 arcsecs North of component B. We demonstrate that a positional offset between the centers of the source components can explain the differences between the optical and radio flux ratios.Comment: 5 pages, 3 figures, 2 tables, accepted to ApJ Letter

Detection of chromatic microlensing in Q 2237+0305 A

We present narrowband images of the gravitational lens system Q~2237+0305 made with the Nordic Optical Telescope in eight different filters covering the wavelength interval 3510-8130 \AA. Using point-spread function photometry fitting we have derived the difference in magnitude versus wavelength between the four images of Q~2237+0305. At $\lambda=4110$ \AA, the wavelength range covered by the Str\"omgren-v filter coincides with the position and width of the CIV emission line. This allows us to determine the existence of microlensing in the continuum and not in the emission lines for two images of the quasar. Moreover, the brightness of image A shows a significant variation with wavelength which can only be explained as consequence of chromatic microlensing. To perform a complete analysis of this chromatic event our observations were used together with Optical Gravitational Lensing Experiment light curves. Both data sets cannot be reproduced by the simple phenomenology described under the caustic crossing approximation; using more realistic representations of microlensing at high optical depth, we found solutions consistent with simple thin disk models ($r_{s}\varpropto \lambda^{4/3}$); however, other accretion disk size-wavelength relationships also lead to good solutions. New chromatic events from the ongoing narrow band photometric monitoring of Q~2237+0305 are needed to accurately constrain the physical properties of the accretion disk for this system.Comment: 9 pages, 9 figures, 2 tables. Matches ApJ published version. Some references adde

Near-Infrared K and L' Flux Ratios in Six Lensed Quasars

We examine the wavelength dependence of flux ratios for six gravitationally lensed quasars using K and L' images obtained at the Gemini North 8m telescope. We select lenses with source redshifts z_s < 2.8 so that K-band images probe rest-frame optical emission from accretion disks, while L'-band images probe rest-frame near-infrared flux emitted (in part) from the more extended surrounding torus. Since the observations correspond to different source sizes, the K and L' flux ratios are sensitive to structure on different scales and may be useful for studying small-structure in the lens galaxies. Four of the six lenses show differences between K and L' flux ratios. In HE 0435$-1223, SDSS 0246-0825, and HE 2149-2745 the differences may be attributable to known microlensing and/or intrinsic variability. In SDSS 0806+2006 the wavelength dependence is not easily attributed to known variations, and may indicate the presence of substructure. By contrast, in Q0142-100 and SBS 0909+523 the K and L' flux ratios are consistent within the uncertainties. We discuss the utility of the current data for studying chromatic effects related to microlensing, dust extinction, and dark matter substructure.Comment: 19 pages, 4 Figures, 4 Tables, AJ accepte

Probing Cosmic Dust of the Early Universe through High-Redshift Gamma-Ray Bursts

We explore the extinction properties of the dust in the distant universe through the afterglows of high-redshifted GRBs based on the "Drude" model which, unlike previous studies, does not require a prior assumption of template extinction laws. We select GRB070802 at z~2.45 (which shows clear evidence for the 2175\AA extinction bump) and GRB050904 at z~6.29, the 2nd most distant GRB observed to date. We fit their afterglow spectra to determine the extinction of their host galaxies. We find that (1) their extinction curves differ substantially from that of the Milky Way, the Small and Large Magellanic Clouds (which were widely adopted as template extinction laws in literature); (2) the 2175\AA extinction feature appears to be also present in GRB050904 at z~6.29; and (3) there does not appear to show strong evidence for a dependence of dust extinction on redshifts. The inferred extinction curves are closely reproduced in terms of a mixture of amorphous silicate and graphite, both of which are expected supernova condensates and have been identified in primitive meteorites as presolar grains originating from supernovae (which are considered as the main source of dust at high-z).Comment: 14 pages, 3 figures, 2 tables; accepted for publication in the Astrophysical Journal Letter

A Bayesian approach to strong lensing modelling of galaxy clusters

In this paper, we describe a procedure for modelling strong lensing galaxy clusters with parametric methods, and to rank models quantitatively using the Bayesian evidence. We use a publicly available Markov chain Monte-Carlo (MCMC) sampler ('Bayesys'), allowing us to avoid local minima in the likelihood functions. To illustrate the power of the MCMC technique, we simulate three clusters of galaxies, each composed of a cluster-scale halo and a set of perturbing galaxy-scale subhalos. We ray-trace three light beams through each model to produce a catalogue of multiple images, and then use the MCMC sampler to recover the model parameters in the three different lensing configurations. We find that, for typical Hubble Space Telescope (HST)-quality imaging data, the total mass in the Einstein radius is recovered with ~1-5% error according to the considered lensing configuration. However, we find that the mass of the galaxies is strongly degenerated with the cluster mass when no multiple images appear in the cluster centre. The mass of the galaxies is generally recovered with a 20% error, largely due to the poorly constrained cut-off radius. Finally, we describe how to rank models quantitatively using the Bayesian evidence. We confirm the ability of strong lensing to constrain the mass profile in the central region of galaxy clusters in this way. Ultimately, such a method applied to strong lensing clusters with a very large number of multiple images may provide unique geometrical constraints on cosmology. The implementation of the MCMC sampler used in this paper has been done within the framework of the Lenstool software package, which is publicly available.Comment: Accepted to "Gravitational Lensing" Focus Issue of the New Journal of Physics (invited), 35 pages, 11 figures at reduced resolutio