The Experts below are selected from a list of 5868 Experts worldwide ranked by ideXlab platform
Andrea Ceglia - One of the best experts on this subject based on the ideXlab platform.
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50 shades of Colour: how thickness, iron redox and manganese/antimony contents influence perceived and Intrinsic Colour in Roman glass
Archaeological and Anthropological Sciences, 2020Co-Authors: Anne-isabelle Bidegaray, Karin Nys, Alberta Silvestri, Peter Cosyns, Wendy Meulebroeck, Herman Terryn, Stéphane Godet, Andrea CegliaAbstract:Roman glass is studied here by means of optical absorption spectroscopy, in order to provide an objective method to quantitatively evaluate Colour. The dataset is composed of 165 soda-lime silicate glass samples from various western European sites, mainly dated from the first to fourth century AD, and containing variable amounts of iron, manganese and/or antimony. Iron redox ratios and Colour coordinates (based on the CIELab Colour system) are determined and put in relation with the thickness of samples and their manganese/antimony contents. Results reveal thickness as a crucial parameter when discussing glass hues, thus leading to a differentiation between the ‘Intrinsic’ and ‘perceived’ Colour of glass objects (i.e. the Colour of the object with the thickness normalised to 1 mm, and that with its original thickness, respectively). Apart from HIMT and purple glass, the concentration of ferrous iron appears to be correlated with a * — a Colourimetric parameter determining how green the glass is. Significant relations of antimony/manganese contents versus iron redox and glass Colour are also considered, resulting in quantitative arguments to entitle antimony-deColoured glass as the most oxidised and Colourless glass.
Anne-isabelle Bidegaray - One of the best experts on this subject based on the ideXlab platform.
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50 shades of Colour: how thickness, iron redox and manganese/antimony contents influence perceived and Intrinsic Colour in Roman glass
Archaeological and Anthropological Sciences, 2020Co-Authors: Anne-isabelle Bidegaray, Karin Nys, Alberta Silvestri, Peter Cosyns, Wendy Meulebroeck, Herman Terryn, Stéphane Godet, Andrea CegliaAbstract:Roman glass is studied here by means of optical absorption spectroscopy, in order to provide an objective method to quantitatively evaluate Colour. The dataset is composed of 165 soda-lime silicate glass samples from various western European sites, mainly dated from the first to fourth century AD, and containing variable amounts of iron, manganese and/or antimony. Iron redox ratios and Colour coordinates (based on the CIELab Colour system) are determined and put in relation with the thickness of samples and their manganese/antimony contents. Results reveal thickness as a crucial parameter when discussing glass hues, thus leading to a differentiation between the ‘Intrinsic’ and ‘perceived’ Colour of glass objects (i.e. the Colour of the object with the thickness normalised to 1 mm, and that with its original thickness, respectively). Apart from HIMT and purple glass, the concentration of ferrous iron appears to be correlated with a * — a Colourimetric parameter determining how green the glass is. Significant relations of antimony/manganese contents versus iron redox and glass Colour are also considered, resulting in quantitative arguments to entitle antimony-deColoured glass as the most oxidised and Colourless glass.
Sugata Kaviraj - One of the best experts on this subject based on the ideXlab platform.
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on the formation of massive galaxies a simultaneous study of number density size and Intrinsic Colour evolution in goods
Monthly Notices of the Royal Astronomical Society, 2009Co-Authors: Ignacio Ferreras, Thorsten Lisker, A Pasquali, Sadegh Khochfar, Sugata KavirajAbstract:The evolution of number density, size and Intrinsic Colour is determined for a volume-limited sample of visually classified early-type galaxies selected from the Hubble Space Telescope/Advanced Camera for Surveys images of the Great Observatories Origins Deep Survey (GOODS) North and South fields (version 2). The sample comprises 457 galaxies over 320 arcmin 2 with stellar masses above 3 x 10 10 M ⊙ in the redshift range 0.4 3 x 10 11 M ⊙ ) do not show any appreciable change in comoving number density or size in our data. Furthermore, when including the results from 2dF galaxy redshift survey, we find that the number density of massive early-type galaxies is consistent with no evolution between z = 1.2 and 0, i.e. over an epoch spanning more than half of the current age of the Universe. We find large discrepancies between the predictions of semi-analytic models. Massive galaxies show very homogeneous Intrinsic Colour distributions, with nearly flat radial Colour gradients, but with a significant negative correlation between stellar mass and Colour gradient, such that red cores appear predominantly in massive galaxies. The distribution of half-light radii - when compared to z ∼ 0 and z > 1 samples - is compatible with the predictions of semi-analytic models relating size evolution to the amount of dissipation during major mergers.
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on the formation of massive galaxies a simultaneous study of number density size and Intrinsic Colour evolution in goods
arXiv: Cosmology and Nongalactic Astrophysics, 2009Co-Authors: Ignacio Ferreras, Thorsten Lisker, A Pasquali, Sadegh Khochfar, Sugata KavirajAbstract:The evolution of number density, size and Intrinsic Colour is determined for a volume-limited sample of visually classified early-type galaxies selected from the HST/ACS images of the GOODS North and South fields (version 2). The sample comprises 457 galaxies over 320 arcmin2 with stellar masses above 3E10 Msun in the redshift range 0.4 3E11 Msun) do not show any appreciable change in comoving number density or size in our data. Furthermore, when including the results from 2dFGRS, we find that the number density of massive early-type galaxies is consistent with no evolution between z=1.2 and 0, i.e. over an epoch spanning more than half of the current age of the Universe. Massive galaxies show very homogeneous **Intrinsic** Colour distributions, featuring red cores with small scatter. The distribution of half-light radii -- when compared to z=0 and z>1 samples -- is compatible with the predictions of semi-analytic models relating size evolution to the amount of dissipation during major mergers. However, in a more speculative fashion, the observations can also be interpreted as weak or even no evolution in comoving number density **and size** between 0.4
S Picaud - One of the best experts on this subject based on the ideXlab platform.
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modelling the galactic interstellar extinction distribution in three dimensions
Astronomy and Astrophysics, 2006Co-Authors: D J Marshall, A C Robin, C Reyle, M Schultheis, S PicaudAbstract:Aims. The Two Micron All Sky Survey, along with the Stellar Population Synthesis Model of the Galaxy, developed in Besancon, is used to calculate the extinction distribution along different lines of sight. By combining many lines of sight, the large scale distribution of interstellar material can be deduced. Methods. The Galaxy model is used to provide the Intrinsic Colour of stars and their probable distances, so that the near infrared Colour excess, and hence the extinction, may be calculated and its distance evaluated. Such a technique is dependent on the model used, however we are able to show that moderate changes in the model parameters result in insignificant changes in the predicted extinction. Results. This technique has now been applied to over 64 000 lines of sight, each separated by 15´, in the inner Galaxy ($|l|\le$ 100°, $|b|\le$ 10°). We have projected our three dimensional results onto a two dimensional plane in order to compare them with existing two dimensional extinction maps and CO surveys. We find that although differences exist due to the different methods used or the medium traced, the same large scale structures are visible in each of the different maps. Using our extinction map, we have derived the main characteristics of the large scale structure of the dust distribution. The scale height of the interstellar matter is found to be $125^{+17}_{-7}$ pc. The dust distribution is found to be asymmetrically warped, in agreement with CO and HI observations of the ISM. However, the slope of the dust warp and the galactocentric distance where it starts are found to be smaller than the values measured for the external HI disc: for positive longitudes the angle is $\theta=$ $89\degr$, it starts at 8.7 kpc from the Galactic center and grows with a slope of 0.14, while at negative longitudes, the angle of the maximum is at $\theta=$ $272\degr$, the starting radius 7.8 kpc and the slope 0.11. Finally, the presence of dust is detected in the Galactic bulge. It forms an elongated structure approximately 5.2 kpc long and lies at an angle of 30 ± $5\degr$ with respect to the Sun-Galactic centre direction. This may be interpreted as a dust lane along the Galactic bar. This resulting extinction map will be useful for studies of the inner Galaxy and its stellar populations.
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modelling the galactic interstellar extinction distribution in three dimensions
arXiv: Astrophysics, 2006Co-Authors: D J Marshall, A C Robin, C Reyle, M Schultheis, S PicaudAbstract:The Two Micron All Sky Survey, along with the Stellar Population Synthesis Model of the Galaxy, developed in Besancon, is used to calculate the extinction distribution along different lines of sight. By combining many lines of sight, the large scale distribution of interstellar material can be deduced. The Galaxy model is used to provide the Intrinsic Colour of stars and their probable distances, so that the near infrared Colour excess, and hence the extinction, may be calculated and its distance evaluated. Such a technique is dependent on the model used, however we are able to show that moderate changes in the model parameters result in insignificant changes in the predicted extinction. This technique has now been applied to over 64000 lines of sight, each separated by 15 arcmin, in the inner Galaxy (|l|<=100 deg, |b|<=10 deg). Using our extinction map, we have derived the main characteristics of the large scale structure of the dust distribution: scale height and warp of the ISM disc as well as the angle of the dust in the Galactic Bar. This resulting extinction map will be useful for studies of the inner Galaxy and its stellar populations.
Herman Terryn - One of the best experts on this subject based on the ideXlab platform.
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50 shades of Colour: how thickness, iron redox and manganese/antimony contents influence perceived and Intrinsic Colour in Roman glass
Archaeological and Anthropological Sciences, 2020Co-Authors: Anne-isabelle Bidegaray, Karin Nys, Alberta Silvestri, Peter Cosyns, Wendy Meulebroeck, Herman Terryn, Stéphane Godet, Andrea CegliaAbstract:Roman glass is studied here by means of optical absorption spectroscopy, in order to provide an objective method to quantitatively evaluate Colour. The dataset is composed of 165 soda-lime silicate glass samples from various western European sites, mainly dated from the first to fourth century AD, and containing variable amounts of iron, manganese and/or antimony. Iron redox ratios and Colour coordinates (based on the CIELab Colour system) are determined and put in relation with the thickness of samples and their manganese/antimony contents. Results reveal thickness as a crucial parameter when discussing glass hues, thus leading to a differentiation between the ‘Intrinsic’ and ‘perceived’ Colour of glass objects (i.e. the Colour of the object with the thickness normalised to 1 mm, and that with its original thickness, respectively). Apart from HIMT and purple glass, the concentration of ferrous iron appears to be correlated with a * — a Colourimetric parameter determining how green the glass is. Significant relations of antimony/manganese contents versus iron redox and glass Colour are also considered, resulting in quantitative arguments to entitle antimony-deColoured glass as the most oxidised and Colourless glass.
