139 research outputs found
Extra-planar H I in the starburst galaxy NGC 253
Get PDFObservations of the nearby starburst galaxy NGC 253 in the 21-cm line reveal the presence of neutral hydrogen in the halo, up to 12 kpc from the galactic plane. This extra-planar H I is found in only one half of the galaxy and is concentrated in a half-ring structure and plumes which are lagging in rotation with respect to the disk. The H I plumes are seen bordering the bright Halpha and X-ray halo emission. It is likely that, as proposed earlier for the Halpha and the X-rays, the origin of the extra-planar H I is also related to the central starburst and to the active star formation in the disk. A minor merger and gas accretion are also discussed as possible explanations. The H I disk is less extended than the stellar disk. This may be the result of ionization of its outer parts or, alternatively, of tidal or ram pressure stripping
High velocity HI in NGC 6946 and extra-planar gas in NGC 253
No full textMulti-wavelength observations of nearby spiral galaxies have shown that neutral and ionized gas are present tip to a few kpc from the disk and that star formation and supernovae probably play an important role in bringing gas into the halo. We have obtained very sensitive H I observations of the face-on galaxy NGC 6946 and of the nearly edge-on starburst galaxy NGC 253. We find high velocity H I clouds in NGC 6946 and extra-planar gas with anomalous velocities in NGC 253. In both galaxies there seems to be a close connection between the star-forming disk and the halo H I. In the outer parts of NGC 6946 there is also evidence for recent gas accretion
Early transcriptional response in the jejunum of germ-free piglets after oral infection with virulent rotavirus
Get PDFGerm-free piglets were orally infected with virulent rotavirus to collect jejunal mucosal scrapings at 12 and 18 hours post infection (two piglets per time point). IFN-gamma mRNA expression was stimulated in the mucosa of all four infected piglets, indicating that they all responded to the rotavirus infection. RNA pools prepared from two infected piglets were used to compare whole mucosal gene expression at 12 and 18 hpi to expression in uninfected germ-free piglets (n = 3) using a porcine intestinal cDNA microarray. Microarray analysis identified 13 down-regulated and 17 up-regulated genes. Northern blot analysis of a selected group of genes confirmed the data of the microarray. Genes were functionally clustered in interferon-regulated genes, proliferation/differentiation genes, apoptosis genes, cytoskeleton genes, signal transduction genes, and enterocyte digestive, absorptive, and transport genes. Down-regulation of the transport gene cluster reflected in part the loss of rotavirus-infected enterocytes from the villous tips. Data mining suggested that several genes were regulated in lower- or mid-villus immature enterocytes and goblet cells, probably to support repair of the damaged epithelial cell layer at the villous tips. Furthermore, up-regulation was observed for IFN-¿ induced guanylate binding protein 2, a protein that effectively inhibited VSV and EMCV replication in vitro (Arch Virol 150:1213¿1220, 2005). This protein may play a role in the small intestine¿s innate defense against enteric viruses like rotavirus
The Westerbork HI survey of irregular and spiral galaxies, WHISP
No full textThis paper briefly describes WHISP, an ongoing project to image the HI in a large sample of nearby galaxies with the Westerbork Synthesis Radio Telescope (WSRT). The goal of the survey is to investigate the HI density distributions and velocity fields of galaxies as a function of Hubble type, luminosity and environment. The main emphasis so far has been on using HI kinematics to determine the mass distributions of galaxies, though other projects have been carried out with the WHISP data and axe briefly described.</p
The physical structure of magellanic cloud HII regions
No full textThis paper presents some of the first results of a project aimed at determining in detail the physical conditions of star-forming regions. The project uses spectroscopic data obtained of 17 HII regions in the SMC and LMC. The data set consists of ISO-SWS, ISO-LWS and optical spectroscopic data covering a spectral range from 0.35 mu m to 198 mu m. The combination of optical and infrared data makes it possible to derive the detailed physical structure of an HII region. Quantities derived from this structure, e.g. improved chemical abundances and excitation source, will provide a link to the star-forming properties of these regions.</p
Interactions, mergers and accretion:What can the HI tell us?
No full textHigh resolution observations of the H I in galaxies provide important additional information for obtaining a proper view on galaxy evolution. This paper focuses on the effects of the environment and describes what we can learn from H I in interacting and/or merging systems.</p
SWS observations of HII regions in the Magellanic Clouds
No full textThis paper describes the scientific goals of the SWS guaranteed time program on HII regions in the Magellanic Clouds and presents some preliminary results. The main objective is to use optical and IR recombination and fine structure lines to unambiguously determine temperature, density and if possible ionization structure and elemental abundance in 16 HII regions in the Large and Small Magellanic Cloud
The Westerbork HI survey of irregular and spiral galaxies, WHISP
No full textThis paper briefly describes WHISP, an ongoing project to image the HI in a large sample of nearby galaxies with the Westerbork Synthesis Radio Telescope (WSRT). The goal of the survey is to investigate the HI density distributions and velocity fields of galaxies as a function of Hubble type, luminosity and environment. The main emphasis so far has been on using HI kinematics to determine the mass distributions of galaxies, though other projects have been carried out with the WHISP data and axe briefly described.</p
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