MERLIN observations of Stephan's Quintet

We present MERLIN L-band images of the compact galaxy group, Stephan's Quintet. The Seyfert 2 galaxy, NGC 7319, the brightest member of the compact group, is seen to have a triple radio structure typical of many extra-galactic radio sources which have a flat spectrum core and two steep spectrum lobes with hot spots. The two lobes are asymmetrically distributed on opposite sides of the core along the minor axis of the galaxy. Ultraviolet emission revealed in a high resolution HRC/ACS HST image is strongly aligned with the radio plasma and we interpret the intense star formation in the core and north lobe as an event induced by the collision of the north radio jet with over-dense ambient material. In addition, a re-mapping of archive VLA L-band observations reveals more extended emission along the major axis of the galaxy which is aligned with the optical axis. Images formed from the combined MERLIN and archive VLA data reveal more detailed structure of the two lobes and hot spots.Comment: Completely revised version with new HST data included, to appear in MNRA

CO Observations of the Interacting Galaxy Pair NGC 5394/95

Peer reviewe

Spitzer Space Telescope IRAC and MIPS observations of the interacting galaxies Ic 2163 and NGC 2207: clumpy emission

Peer reviewe

Cortical interstitial cell interactions induce sensitivity of hydronephrotic kidney to bradykinin

Cortical interstitial cell interactions induce sensitivity of hydronephrotic kidney to bradykinin. The mechanism of the increased prostaglandin production and induction of sensitivity to bradykinin by the cortex of the hydronephrotic rabbit kidney was investigated using tissue culture techniques. Cortical interstitial cells from normal, unilaterally hydronephrotic and contralateral kidneys were grown in tissue culture. Cells derived from hydronephrotic kidneys, but not normal or contralateral, increased PGE2 production when incubated with bradykinin. Of the two cell types, fibroblasts and macrophages, grown from hydronephrotic expiants, neither increased prostaglandin production when grown alone in tissue culture. Recombining the two cell types restored bradykinin responsiveness. Bradykinin responsiveness could be induced in either normal or contralateral cell cultures when macrophages from the hydronephrotic kidney were added to cultures of cells from normal or contralateral cortex. The data indicate unique characteristics of hydronephrotic macrophages are involved in the induction of bradykinin responsiveness in the cortex of the ureter-ligated kidney

3C254: MERLIN observations of a highly asymmetric quasar

Multifrequency, high-resolution radio observations of the quasar 3C254 using MERLIN are presented. The quasar has a highly asymmetric radio structure, with the eastern component of the double-lobed structure being much closer to the nucleus and significantly less polarized than the western one. However, the two lobes are more symmetric in their total flux densities. The observations show the detailed structure of the hotspots which are very different on opposite sides of the radio core, reveal no radio jet and suggest that the oppositely-directed jets may be intrinsically asymmetric.Comment: 8 pages, 5 figures, 1 table, accepted for publication in MNRA

Monitoring of the prompt radio emission from the unusual supernova 2004dj in NGC2403

Supernova 2004dj in the nearby spiral galaxy NGC2403 was detected optically in July 2004. Peaking at a magnitude of 11.2, this is the brightest supernova detected for several years. Here we present Multi-Element Radio Linked Interferometer Network (MERLIN) observations of this source, made over a four month period, which give a position of R.A. = 07h37m17.044s, Dec =+65deg35'57.84" (J2000.0). We also present a well-sampled 5 GHz light curve covering the period from 5 August to 2 December 2004. With the exception of the unusual and very close SN 1987A, these observations represent the first detailed radio light curve for the prompt emission from a Type II-P supernova.Comment: (1) Jodrell Bank Observatory (2) University of Valencia (3) University of Sheffield 6 pages, 1 figure. To appear in ApJ letter

A graph theory-based multi-scale analysis of hierarchical cascade in molecular clouds : Application to the NGC 2264 region

The spatial properties of small star-clusters suggest that they may originate from a fragmentation cascade of the cloud for which there might be traces up to a few dozen of kAU. Our goal is to investigate the multi-scale spatial structure of gas clumps, to probe the existence of a hierarchical cascade and to evaluate its possible link with star production in terms of multiplicity. From the Herschel emission maps of NGC 2264, clumps are extracted using getsf software at each of their associated spatial resolution, respectively [8.4, 13.5, 18.2, 24.9, 36.3]". Using the spatial distribution of these clumps and the class 0/I Young Stellar Object (YSO) from Spitzer data, we develop a graph-theoretic analysis to represent the multi-scale structure of the cloud as a connected network. From this network, we derive three classes of multi-scale structure in NGC 2264 depending on the number of nodes produced at the deepest level: hierarchical, linear and isolated. The structure class is strongly correlated with the column density $N_{\rm H_2}$ since the hierarchical ones dominate the regions whose N$_{\rm H_2} > 6 \times 10^{22}$cm$^{-2}$. Although the latter are in minority, they contain half of the class 0/I YSOs proving that they are highly efficient in producing stars. We define a novel statistical metric, the fractality coefficient F that measure the fractal index describing the scale-free process of the cascade. For NGC 2264, we estimate F = 1.45$\pm$0.12. However, a single fractal index fails to fully describe a scale-free process since the hierarchical cascade starts at a 13 kAU characteristic spatial scale. Our novel methodology allows us to correlate YSOs with their multi-scale gaseous environment. This hierarchical cascade that drives efficient star formation is suspected to be both hierarchical and rooted by the larger-scale gas environment up to 13 kAU

3C459: A highly asymmetric radio galaxy with a starburst

Multifrequency radio observations of the radio galaxy 3C459 using MERLIN, VLA and the EVN, and an optical HST image using the F702W filter are presented. The galaxy has a very asymmetric radio structure, a high infrared luminosity and a young stellar population. The eastern component of the double-lobed structure is brighter, much closer to the nucleus and is significantly less polarized than the western one. This is consistent with the jet on the eastern side interacting with dense gas, which could be due to a merged companion or dense cloud of gas. The HST image of the galaxy presented here exhibits filamentary structures, and is compared with the MERLIN 5-GHz radio map. EVN observations of the prominent central component, which has a steep radio spectrum, show a strongly curved structure suggesing a bent or helical radio jet. The radio structure of 3C459 is compared with other highly asymmetric, Fanaroff-Riley II radio sources, which are also good candidates for studying jet-cloud interactions. Such sources are usually of small linear size and it is possible that the jets are interacting with clouds of infalling gas that fuel the radio source.Comment: 10 pages, 6 figures, 2 table