The signature of dissipation in the mass-size relation: are bulges simply spheroids wrapped in a disc?

The relation between the stellar mass and size of a galaxy's structural subcomponents, such as discs and spheroids, is a powerful way to understand the processes involved in their formation. Using very large catalogues of photometric bulge+disc structural decompositions and stellar masses from the Sloan Digital Sky Survey Data Release Seven, we carefully define two large subsamples of spheroids in a quantitative manner such that both samples share similar characteristics with one important exception: the 'bulges' are embedded in a disc and the 'pure spheroids' are galaxies with a single structural component. Our bulge and pure spheroid subsample sizes are 76,012 and 171,243 respectively. Above a stellar mass of ~$10^{10}$ M$_{\odot}$, the mass-size relations of both subsamples are parallel to one another and are close to lines of constant surface mass density. However, the relations are offset by a factor of 1.4, which may be explained by the dominance of dissipation in their formation processes. Whereas the size-mass relation of bulges in discs is consistent with gas-rich mergers, pure spheroids appear to have been formed via a combination of 'dry' and 'wet' mergers.Comment: Accepted for publication in MNRAS, 6 pages, 3 figure

The SBF Survey of Galaxy Distances. I. Sample Selection, Photometric Calibration, and the Hubble Constant

We describe a program of surface brightness fluctuation (SBF) measurements for determining galaxy distances. This paper presents the photometric calibration of our sample and of SBF in general. Basing our zero point on observations of Cepheid variable stars, we find that the absolute SBF magnitude in the Kron-Cousins I band correlates well with the mean (V-I)o color of a galaxy according to M_Ibar = (-1.74 +/- 0.07) + (4.5 +/- 0.25) [ (V-I)o - 1.15 ] for 1.0 < (V-I) < 1.3. This agrees well with theoretical estimates from stellar population models. Comparisons between SBF distances and a variety of other estimators, including Cepheid variable stars, the Planetary Nebula Luminosity Function (PNLF), Tully-Fisher (TF), Dn-sigma, SNII, and SNIa, demonstrate that the calibration of SBF is universally valid and that SBF error estimates are accurate. The zero point given by Cepheids, PNLF, TF (both calibrated using Cepheids), and SNII is in units of Mpc; the zero point given by TF (referenced to a distant frame), Dn-sigma and SNIa is in terms of a Hubble expansion velocity expressed in km/s. Tying together these two zero points yields a Hubble constant of H_0 = 81 +/- 6 km/s/Mpc. As part of this analysis, we present SBF distances to 12 nearby groups of galaxies where Cepheids, SNII, and SNIa have been observed.Comment: 29 pages plus 8 figures; LaTeX (AASTeX) uses aaspp4.sty (included); To appear in The Astrophysical Journal, 1997 February 1 issue; Compressed PostScript available from ftp://mars.tuc.noao.edu/sbf

Measurement of the Integrated Faraday Rotations of BL Lac Objects

We present the results of multi-frequency polarization VLA observations of radio sources from the complete sample of northern, radio-bright BL Lac objects compiled by H. Kuhr and G. Schmidt. These were used to determine the integrated rotation measures of 18 objects, 15 of which had never been measured previously, which hindered analysis of the intrinsic polarization properties of objects in the complete sample. These measurements make it possible to correct the observed orientations of the linear polarizations of these sources for the effect of Faraday rotation. The most probable origin for Faraday rotation in these objects is the Galactic interstellar medium. The results presented complete measurements of the integrated rotation measures for all 34 sources in the complete sample of BL Lac objects.Comment: 9 pages, 7 figure

The E-ELT Multi-Object Spectrograph: latest news from MOSAIC

There are 8000 galaxies, including 1600 at z larger than 1.6, which could be simultaneously observed in an E-ELT field of view of 40 sq. arcmin. A considerable fraction of astrophysical discoveries require large statistical samples, which can only be obtained with multi-object spectrographs (MOS). MOSAIC will provide a vast discovery space, enabled by a multiplex of 200 and spectral resolving powers of R=5000 and 20000. MOSAIC will also offer the unique capability of more than 10 "high-definition" (multi-object adaptive optics, MOAO) integral-field units, optimised to investigate the physics of the sources of reionization. The combination of these modes will make MOSAIC the world-leading MOS facility, contributing to all fields of contemporary astronomy, from extra-solar planets, to the study of the halo of the Milky Way and its satellites, and from resolved stellar populations in nearby galaxies out to observations of the earliest "first-light" structures in the Universe. It will also study the distribution of the dark and ordinary matter at all scales and epochs of the Universe. Recent studies of critical technical issues such as sky-background subtraction and MOAO have demonstrated that such a MOS is feasible with state-of-the-art technology and techniques. Current studies of the MOSAIC team include further trade-offs on the wavelength coverage, a solution for compensating for the non-telecentric new design of the telescope, and tests of the saturation of skylines especially in the near-IR bands. In the 2020s the E-ELT will become the world's largest optical/IR telescope, and we argue that it has to be equipped as soon as possible with a MOS to provide the most efficient, and likely the best way to follow-up on James Webb Space Telescope (JWST) observations.Comment: 10 pages, 3 Figures, in Ground-based and Airborne Instrumentation for Astronomy VI, 2016, Proc. SPI

Extracellular sheath formation by Sphaeropsis hypodermia and association with its infection in elm trees

Nous avons observé le mode de développement de Sphaeropsis hypodermia (isolé d'une branche d'orme (Ulmus americana) atteinte d'un chancre) dans les milieux suivants : un milieu gélosé (PDA), un tissu essuie-tout (Kimwipes), des blocs de bois d'orme stérilisés à l'autoclave, et des ormes d'Amérique inoculés en serre. Des échantillons de chaque substrat ont été fixés pour les observations en microscopie photonique et en microscopie électronique avec du glutaraldéhyde et du tétroxyde d'osmium. Observés en microscopie électronique, les hyphes accolés au substrat étaient entourés d'une épaisse couche extracellulaire devenant circonscrite par des bandes rigides et contenant des corps opaques simples ou agrégés, ou des masses de matière opaque plus volumineuses dans le cas des blocs de bois d'orme. Sur celui-ci et sur le tissu Kimwipes, la couche extracellulaire s'étendait sur une distance appréciable, loin des cellules fongiques, et avait également pénétré les parois de cellules de parenchyme et des fibres, selon le cas. Dans les ormes inoculés, le champignon a rapidement produit des dommages notables dans les tissus du cambium et colonisé abondamment les régions de l'écorce et du xylème avoisinantes. La pénétration et la dégradation des parois cellulaires de l'écorce étaient marquées, en relation également avec de la matière opaque entourant les cellules du champignon. Cette matière ressemblait à celle liée aux cellules fongiques sur les milieux stérilisés. Bien que les cellules du xylème étaient généralement colonisées, des altérations pariétales n'étaient apparentes que dans les cellules récemment formées. En outre, le passage du champignon d'une cellule à l'autre à travers les parois n'a été observé que dans le cas des éléments de vaisseaux et des cellules de rayon. Concernant les fibres, seule y était visible une bande de matière filamenteuse dans les parois et liant les cellules fongiques présentes dans la lumière de ces fibres. En réponse à la dégradation de parois cellulaires liée à de la matière opaque, l'hypertrophie et l'hyperplasie des cellules du cambium et de l'écorce interne ont été observées, liées possiblement à la formation d'une barrière de protection. On discute du rôle possible de la couche extracellulaire des cellules fongiques in vivo et in vitro.Sphaeropsis hypodermia, isolated from a cankered American elm branch, was grown on agar medium (PDA), on autoclaved wiping paper (Kimwipes), and American elm (Ulmus americana) wood chips, or inoculated into greenhouse-grown American elm saplings. Samples from each treatment were double-fixed with glutaraldehyde and osmium tetroxide and examined with the light and the transmission electron microscopes. Ultrastructurally, the hyphae on PDA and inert substrates appeared surrounded by large extracellular sheaths which were delimited by rigid opaque bands of various thicknesses. The sheaths extended appreciable distances from the fungal cells, as evidenced by their adherence to rigid substrates. Individual or aggregated opaque bodies, even as large masses on elm wood chips, were the main components of the sheath. This opaque material was often associated with penetration and ruptures of the wood cells. Inoculated into elm trees, the fungus rapidly caused pronounced alterations of cambial tissues and colonized the adjoining bark and xylem cells. The prominent penetration and breakdown of the inner and outer bark cells by the fungus were associated with opaque material, particularly in cortical fibres. The material was structurally similar to the sheath formed on the rigid sterilized substrates. In the xylem, only the walls of the recently deposited cells were visibly altered, and although mature fibres were generally colonized, the passage of the fungus from one fibre to another was rarely observed, contrary to the passage from vessel and ray cells to adjoining cells. In that instance, only bands of opaque material present in the walls of fibres were connected with fungal cells in their lumen. In the inner bark and cambial regions, cell hypertrophy and hyperplasia occurred next to host walls that were altered and contained similar opaque material. The extracellular sheath of S. hypodermia under in vitro conditions and the opaque material associated with host wall alterations in vivo are considered to be analogous

Extracellular Vesicles: Mechanisms in Human Health and Disease

SIGNIFICANCE: Secreted extracellular vesicles (EVs) are now considered veritable entities for diagnosis, prognosis, and therapeutics. These structures are able to interact with target cells and modify their phenotype and function. Recent Advances: Since composition of EVs depends on the cell type of origin and the stimulation that leads to their release, the analysis of EV content remains an important input to understand the potential effects of EVs on target cells. CRITICAL ISSUES: Here, we review recent data related to the mechanisms involved in the formation of EVs and the methods allowing specific EV isolation and identification. Also, we analyze the potential use of EVs as biomarkers in different pathologies such as diabetes, obesity, atherosclerosis, neurodegenerative diseases, and cancer. Besides, their role in these diseases is discussed. Finally, we consider EVs enriched in microRNA or drugs as potential therapeutic cargo able to deliver desirable information to target cells/tissues. FUTURE DIRECTIONS: We underline the importance of the homogenization of the parameters of isolation of EVs and their characterization, which allow considering EVs as excellent biomarkers for diagnosis and prognosis

Dutch parallel corpus: a balanced parallel corpus for Dutch-English and Dutch-French

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The Magnitude-Size Relation of Galaxies out to z ~ 1

As part of the Deep Extragalactic Evolutionary Probe (DEEP) survey, a sample of 190 field galaxies (I_{814} <= 23.5) in the ``Groth Survey Strip'' has been used to analyze the magnitude-size relation over the range 0.1 < z < 1.1. The survey is statistically complete to this magnitude limit. All galaxies have photometric structural parameters, including bulge fractions (B/T), from Hubble Space Telescope images, and spectroscopic redshifts from the Keck Telescope. The analysis includes a determination of the survey selection function in the magnitude-size plane as a function of redshift, which mainly drops faint galaxies at large distances. Our results suggest that selection effects play a very important role. A first analysis treats disk-dominated galaxies with B/T < 0.5. If selection effects are ignored, the mean disk surface brightness (averaged over all galaxies) increases by ~1.3 mag from z = 0.1 to 0.9. However, most of this change is plausibly due to comparing low luminosity galaxies in nearby redshift bins to high luminosity galaxies in distant bins. If this effect is allowed for, no discernible evolution remains in the disk surface brightness of bright (M_B < -19) disk-dominated galaxies. A second analysis treats all galaxies by substituting half-light radius for disk scale length, with similar conclusions. Indeed, at all redshifts, the bulk of galaxies is consistent with the magnitude-size envelope of local galaxies, i.e., with little or no evolution in surface brightness. In the two highest redshift bins (z > 0.7), a handful of luminous, high surface brightness galaxies appears that occupies a region of the magnitude-size plane rarely populated by local galaxies. Their wide range of colors and bulge fractions points to a variety of possible origins.Comment: 19 pages, 12 figures. Accepted for publication in the Astrophysical Journa

Determination of complex dielectric functions of ion implanted and implanted‐annealed amorphous silicon by spectroscopic ellipsometry

Measuring with a spectroscopic ellipsometer (SE) in the 1.8–4.5 eV photon energy region we determined the complex dielectric function (ϵ = ϵ1 + iϵ2) of different kinds of amorphous silicon prepared by self‐implantation and thermal relaxation (500 °C, 3 h). These measurements show that the complex dielectric function (and thus the complex refractive index) of implanted a‐Si (i‐a‐Si) differs from that of relaxed (annealed) a‐Si (r‐a‐Si). Moreover, its ϵ differs from the ϵ of evaporated a‐Si (e‐a‐Si) found in the handbooks as ϵ for a‐Si. If we use this ϵ to evaluate SE measurements of ion implanted silicon then the fit is very poor. We deduced the optical band gap of these materials using the Davis–Mott plot based on the relation: (ϵ2E2)1/3 ∼ (E− Eg). The results are: 0.85 eV (i‐a‐Si), 1.12 eV (e‐a‐Si), 1.30 eV (r‐a‐Si). We attribute the optical change to annihilation of point defects