Dense molecular clouds in the SN2008fp host galaxy

(abridged) We use observations of interstellar absorption features, such as atomic and molecular lines as well as diffuse interstellar bands (DIBs), towards SN2008fp to study the physical properties of extra-galactic diffuse interstellar clouds in the host galaxy, ESO428-G14. The properties of the intervening dust are investigated via spectropolarimetry. The spectra of SN2008fp reveal a complex of diffuse atomic clouds at radial velocities in line with the systematic velocities of the host galaxy (~1700 km/s). A translucent (A_V ~ 1.5 mag) cloud is detected at a heliocentric velocity of 1770 km/s This cold dense cloud is rich in dense atomic gas tracers, molecules, as well as diffuse interstellar bands. We have detected both C2 and C3 for the first time in a galaxy beyond the Local Group. The CN (0,0) band line ratios are used to derive an in-situ measurement of the cosmic background radiation temperature in an external galaxy; this gives an excitation temperature of T = 2.9 +- 0.3 K. The interstellar polarization law deviates significantly from what is observed in the Galaxy, indicating substantial differences in the composition or size distribution of dust grains in the SN2008fp host galaxy. C2 is used to probe the cold diffuse ISM density and temperature. The lack of variability in the extra-galactic absorption line profiles over a period of one month implies that the absorbing material is not circumstellar and thus not affected directly by the SN event. Also it shows that there are no significant density variation in the small-scale structure of the molecular cloud down to 100 AU.Comment: 10 pages. Accepted for publication in A&A. Revisions include several small correction

Studying the small scale ISM structure with supernovae

AIMS. In this work we explore the possibility of using the fast expansion of a Type Ia supernova photosphere to detect extra-galactic ISM column density variations on spatial scales of ~100 AU on time scales of a few months. METHODS. We constructed a simple model which describes the expansion of the photodisk and the effects of a patchy interstellar cloud on the observed equivalent width of Na I D lines. Using this model we derived the behavior of the equivalent width as a function of time, spatial scale and amplitude of the column density fluctuations. RESULTS. The calculations show that isolated, small (<100 AU) clouds with Na I column densities exceeding a few 10^11 cm^-2 would be easily detected. In contrast, the effects of a more realistic, patchy ISM become measurable in a fraction of cases, and for peak-to-peak variations larger than ~10^12 cm^-2 on a scale of 1000 AU. CONCLUSIONS. The proposed technique provides a unique way to probe the extra-galactic small scale structure, which is out of reach for any of the methods used so far. The same tool can also be applied to study the sub-AU Galactic ISM structure.Comment: 6 pages, 3 figures. Accepted for publication in Astronomy & Astrophysic

Eyes in the sky: Interactions between AGB winds and the interstellar magnetic field

We aim to examine the role of the interstellar magnetic field in shaping the extended morphologies of slow dusty winds of Asymptotic Giant-branch (AGB) stars in an effort to pin-point the origin of so-called eye shaped CSE of three carbon-rich AGB stars. In addition, we seek to understand if this pre-planetary nebula (PN) shaping can be responsible for asymmetries observed in PNe. Hydrodynamical simulations are used to study the effect of typical interstellar magnetic fields on the free-expanding spherical stellar winds as they sweep up the local interstellar medium (ISM). The simulations show that typical Galactic interstellar magnetic fields of 5 to 10 muG, are sufficient to alter the spherical expanding shells of AGB stars to appear as the characteristic eye shape revealed by far-infrared observations. The typical sizes of the simulated eyes are in accordance with the observed physical sizes. However, the eye shapes are of transient nature. Depending on the stellar and interstellar conditions they develop after 20,000 to 200,000yrs and last for about 50,000 to 500,000 yrs, assuming that the star is at rest relative to the local interstellar medium. Once formed the eye shape will develop lateral outflows parallel to the magnetic field. The "explosion" of a PN in the center of the eye-shaped dust shell gives rise to an asymmetrical nebula with prominent inward pointing Rayleigh-Taylor instabilities. Interstellar magnetic fields can clearly affect the shaping of wind-ISM interaction shells. The occurrence of the eyes is most strongly influenced by stellar space motion and ISM density. Observability of this transient phase is favoured for lines-of-sight perpendicular to the interstellar magnetic field direction. The simulations indicate that shaping of the pre-PN envelope can strongly affect the shape and size of PNe.Comment: Accepted for publication in A&A. Final version will contain animated result

Large Interstellar Polarisation Survey II. UV/optical study of cloud-to-cloud variations of dust in the diffuse ISM

It is well known that the dust properties of the diffuse interstellar medium exhibit variations towards different sight-lines on a large scale. We have investigated the variability of the dust characteristics on a small scale, and from cloud-to-cloud. We use low-resolution spectro-polarimetric data obtained in the context of the Large Interstellar Polarisation Survey (LIPS) towards 59 sight-lines in the Southern Hemisphere, and we fit these data using a dust model composed of silicate and carbon particles with sizes from the molecular to the sub-micrometre domain. Large (> 6 nm) silicates of prolate shape account for the observed polarisation. For 32 sight-lines we complement our data set with UVES archive high-resolution spectra, which enable us to establish the presence of single-cloud or multiple-clouds towards individual sight-lines. We find that the majority of these 35 sight-lines intersect two or more clouds, while eight of them are dominated by a single absorbing cloud. We confirm several correlations between extinction and parameters of the Serkowski law with dust parameters, but we also find previously undetected correlations between these parameters that are valid only in single-cloud sight-lines. We find that interstellar polarisation from multiple-clouds is smaller than from single-cloud sight-lines, showing that the presence of a second or more clouds depolarises the incoming radiation. We find large variations of the dust characteristics from cloud-to-cloud. However, when we average a sufficiently large number of clouds in single-cloud or multiple-cloud sight-lines, we always retrieve similar mean dust parameters. The typical dust abundances of the single-cloud cases are [C]/[H] = 92 ppm and [Si]/[H] = 20 ppm.Comment: A&A accepte

Diffractive production of high pt photons at HERA

We study the diffractive production of high pt photons at HERA. We have implemented the process as a new hard sub-process in the HERWIG event generator in order to prepare the ground for a future measurement.Comment: 4 pages, 4 figures. Contribution to the 1999 UK Phenomenology Workshop on Collider Physics, Durham, U

Polycyclic aromatic hydrocarbons and molecular hydrogen in oxygen-rich planetary nebulae: the case of NGC6720

Evolved stars are primary sources for the formation of polycyclic aromatic hydrocarbons (PAHs) and dust grains. Their circumstellar chemistry is usually designated as either oxygen-rich or carbon-rich, although dual-dust chemistry objects, whose infrared spectra reveal both silicate- and carbon-dust features, are also known. The exact origin and nature of this dual-dust chemistry is not yet understood. Spitzer-IRS mid-infrared spectroscopic imaging of the nearby, oxygen-rich planetary nebula NGC6720 reveals the presence of the 11.3 micron aromatic (PAH) emission band. It is attributed to emission from neutral PAHs, since no band is observed in the 7 to 8 micron range. The spatial distribution of PAHs is found to closely follow that of the warm clumpy molecular hydrogen emission. Emission from both neutral PAHs and warm H2 is likely to arise from photo-dissociation regions associated with dense knots that are located within the main ring. The presence of PAHs together with the previously derived high abundance of free carbon (relative to CO) suggest that the local conditions in an oxygen-rich environment can also become conducive to in-situ formation of large carbonaceous molecules, such as PAHs, via a bottom-up chemical pathway. In this scenario, the same stellar source can enrich the interstellar medium with both oxygen-rich dust and large carbonaceous molecules.Comment: Accepted by MNRAS. 5 page

Deep Proteomics of Mouse Skeletal Muscle Enables Quantitation of Protein Isoforms, Metabolic Pathways, and Transcription Factors

Skeletal muscle constitutes 40% of individual body mass and plays vital roles in locomotion and whole-body metabolism. Proteomics of skeletal muscle is challenging because of highly abundant contractile proteins that interfere with detection of regulatory proteins. Using a state-of-the art MS workflow and a strategy to map identifications from the C2C12 cell line model to tissues, we identified a total of 10,218 proteins, including skeletal muscle specific transcription factors like myod1 and myogenin and circadian clock proteins. We obtain absolute abundances for proteins expressed in a muscle cell line and skeletal muscle, which should serve as a valuable resource. Quantitation of protein isoforms of glucose uptake signaling pathways and in glucose and lipid metabolic pathways provides a detailed metabolic map of the cell line compared with tissue. This revealed unexpectedly complex regulation of AMP-activated protein kinase and insulin signaling in muscle tissue at the level of enzyme isoforms

Reply to ``Comment on `Insulating Behavior of λ\lambda-DNA on the Micron Scale' "

In our experiment, we found that the resistance of vacuum-dried $\lambda$-DNA exceeds $10^{14} \Omega$ at 295 K. Bechhoefer and Sen have raised a number of objections to our conclusion. We provide counter arguments to support our original conclusion.Comment: 1 page reply to comment, 1 figur