Time delays in gravitationally lensed quasars

Starting with a concise introduction on gravitational lensing, time delays between lensed quasars and its importance as a cosmological probe to estimate the Hubble constant, we present our contribution to this domain. In a first part, we explain the details of the Numerical Model Fit, a method to estimate time delays between two or more lensed quasar images. We apply this technique to the light curves of 11 lensed quasars with known time delays in order to analyse these published delays in a more homogeneous way. Some results can be confirmed, but others prove to be unreliable. The second part is devoted to the most recent results of our contribution to the COSMOGRAIL collaboration. We briefly summarize the data reduction and analysis tools before the presentation of the photometry and time delay analysis of 6 lensed quasars. On top of the confirmation of time delays in two objects, SDSS J1206+4332 and SDSS J1650+4251, we are the first to measure the time delay in three doubly lensed quasar systems: HS 2209+1914, SDSS J0903+5028, and SDSS J1155+6346. The time delay analysis of the well-known quadruply lensed quasar PG 1115+080 reveals interesting elements, and asks for further investigation of longer light curves.Après une courte introduction sur les lentilles gravitationnelles, les délais temporels entre les images de quasars et leur importance comme méthode pour estimer la constante de Hubble, nous présentons notre contribution à ce domaine. Dans une première partie, nous expliquons les détails de notre méthode qui, en utilisant un ajustement d’un modèle numérique, mesure le délai temporel entre deux ou plusieurs images d’un quasar ayant subi l’e et de lentille gravitationnelle. Nous appliquons ensuite cette technique à des courbes de lumière de 11 mirages gravitationnels ayant un délai temporel connu, afin d’analyser ces délais de façon plus homogène. Certains résultats sont confirmés, mais d’autres se révèlent être douteux. La deuxième partie est consacrée aux résultats les plus récents de notre contribution à la collaboration COSMOGRAIL. Nous résumons brièvement les méthodes de réduction et d’analyse des données puis nous présentons la photométrie et l’analyse des délais temporels de 6 mirages gravitationnels. En plus de la confirmation des délais temporels dans deux objets, SDSS J1206+4332 et SDSS J1650+4251, nous sommes les premiers à mesurer le délai temporel dans trois mirages gravitationnels à deux images: HS 2209+1914, SDSS J0903+5028 et SDSS J1155+6346. Enfin, l’analyse des délais temporels dans la lentille quadruple bien connue PG 1115+080 révèle des éléments intéressants et demande une étude approfondie de plus longues courbes de lumière

COSMOGRAIL: the COSmological MOnitoring of GRAvItational Lenses: XIV. Time delay of the doubly lensed quasar SDSS~J1001+5027

This paper presents optical R-band light curves and the time delay of the doubly imaged gravitationally lensed quasar SDSS J1001+5027 at a redshift of 1.838. We have observed this target for more than six years, between March 2005 and July 2011, using the 1.2-m Mercator Telescope, the 1.5-m telescope of the Maidanak Observatory and the 2-m Himalayan Chandra Telescope. Our resulting light curves are composed of 443 independent epochs, and show strong intrinsic quasar variability, with an amplitude of the order of 0.2 magnitudes. From this data, we measure the time delay using five different methods, all relying on distinct approaches. One of these techniques is a new development presented in this paper. All our time-delay measurements are perfectly compatible. By combining them, we conclude that image A is leading B by 119.3 ± 3.3 days (1σ, 2.8%), including systematic errors. It has been shown recently that such accurate time-delay measurements offer a highly complementary probe of dark energy and spatial curvature, as they independently constrain the Hubble constant. The next mandatory step towards using SDSS J1001+5027 in this context will be the measurement of the redshift of the lensing galaxy, in combination with deep HST imaging

COSMOGRAIL: Measuring Time Delays of Gravitationally Lensed Quasars to Constrain Cosmology

COSMOGRAIL is a long-term programme for the photometric monitoring of gravitationally lensed quasars. It makes use of several medium-size telescopes to derive long and well-sampled light curves of lensed quasars, in order to measure the time delays between the quasar images. These delays directly relate to the Hubble constant H0, without any need for secondary distance calibrations. COSMOGRAIL was initiated in 2004, and has now secured almost a decade of data, resulting in cosmological constraints that are very complementary to other cosmological probes

Seroprevalence for Brucella spp. in Baltic ringed seals (Phoca hispida) and East Greenland harp (Pagophilus groenlandicus) and hooded (Cystophora cristata) seals

Zoonotic infections transmitted from marine mammals to humans in the Baltic and European Arctic are of unknown significance, despite given considerable potential for transmission due to local hunt. Here we present results of an initial screening for Brucella spp. in Arctic and Baltic seal species. Baltic ringed seals (Pusa hispida, n = 12) sampled in October 2015 and Greenland Sea harp seals (Pagophilus groenlandicus, n = 6) and hooded seals (Cystophora cristata, n = 3) sampled in March 2015 were serologically analysed for antibodies against Brucella spp. The serological analyses were performed using the Rose Bengal Test (RBT) followed by a confirmatory testing of RBT-positive samples by a competitive-enzyme linked immunosorbent assay (C-ELISA). Two of the Baltic ringed seals (a juvenile male and a juvenile female) were seropositive thus indicating previous exposure to a Brucella spp. The findings indicate that ringed seals in the Baltic ecosystem may be exposed to and possibly infected by Brucella spp. No seropositive individuals were detected among the Greenland harp and hooded seals. Although our initial screening shows a zoonotic hazard to Baltic locals, a more in-depth epidemiological investigation is needed in order to determine the human risk associated with this

Prevalence of antibodies against Brucella spp. in West Greenland polar bears (Ursus maritimus) and East Greenland muskoxen (Ovibos moschatus)

Zoonotic infections transmitted from terrestrial and marine mammals to humans in European Arctic are of unknown significance, despite considerable potential for transmission due to local hunt and a rapidly changing environment. As an example, infection with Brucella bacteria may have significant impact on human health due to consumption of raw meat or otherwise contact with tissues and fluids of infected game species such as muskoxen and polar bears. Here, we present serological results for Baffin Bay polar bears (Ursus maritimus) (n = 96) and North East Greenland muskoxen (Ovibos moschatus) (n = 32) for antibodies against Brucella spp. The analysis was a two-step trial initially using the Rose Bengal Test (RBT), followed by confirmative competitive enzyme-linked immunosorbent assays of RBT-positive samples. No muskoxen had antibodies against Brucella spp., while antibodies were detected in six polar bears (6.25%) rendering a seroprevalence in line with previous findings in other Arctic regions. Seropositivity was not related to sex, age or biometrics i.e. size and body condition. Whether Brucella spp. antibodies found in polar bears were due to either prey spill over or true recurrent Brucella spp. infections is unknown. Our results therefore highlight the importance of further research into the zoonotic aspects of Brucella spp. infections, and the impact on wildlife and human health in the Arctic region.Prevalence of antibodies against Brucella spp. in West Greenland polar bears (Ursus maritimus) and East Greenland muskoxen (Ovibos moschatus)acceptedVersion© Springer-Verlag GmbH Germany, part of Springer Nature 2018. This is a post-peer-review, pre-copyedit version of an article published in Polar Biology. Locked until 19 March 2019 due to copyright restrictions. The final authenticated version is available online at: https://doi.org/10.1007/s00300-018-2307-4

Prevalence of antibodies against Brucella spp. in West Greenland polar bears (Ursus maritimus) and East Greenland muskoxen (Ovibos moschatus)

Zoonotic infections transmitted from terrestrial and marine mammals to humans in European Arctic are of unknown significance, despite considerable potential for transmission due to local hunt and a rapidly changing environment. As an example, infection with Brucella bacteria may have significant impact on human health due to consumption of raw meat or otherwise contact with tissues and fluids of infected game species such as muskoxen and polar bears. Here, we present serological results for Baffin Bay polar bears (Ursus maritimus) (n = 96) and North East Greenland muskoxen (Ovibos moschatus) (n = 32) for antibodies against Brucella spp. The analysis was a two-step trial initially using the Rose Bengal Test (RBT), followed by confirmative competitive enzyme-linked immunosorbent assays of RBT-positive samples. No muskoxen had antibodies against Brucella spp., while antibodies were detected in six polar bears (6.25%) rendering a seroprevalence in line with previous findings in other Arctic regions. Seropositivity was not related to sex, age or biometrics i.e. size and body condition. Whether Brucella spp. antibodies found in polar bears were due to either prey spill over or true recurrent Brucella spp. infections is unknown. Our results therefore highlight the importance of further research into the zoonotic aspects of Brucella spp. infections, and the impact on wildlife and human health in the Arctic region