HIFI spectroscopy of low-level water transitions in M82

We present observations of the rotational ortho-water ground transition, the two lowest para-water transitions, and the ground transition of ionised ortho-water in the archetypal starburst galaxy M82, performed with the HIFI instrument on the Herschel Space Observatory. These observations are the first detections of the para-H2O(111-000) (1113\,GHz) and ortho-H2O+(111-000) (1115\,GHz) lines in an extragalactic source. All three water lines show different spectral line profiles, underlining the need for high spectral resolution in interpreting line formation processes. Using the line shape of the para-H2O(111-000) and ortho-H2O+(111-000) absorption profile in conjunction with high spatial resolution CO observations, we show that the (ionised) water absorption arises from a ~2000 pc^2 region within the HIFI beam located about ~50 pc east of the dynamical centre of the galaxy. This region does not coincide with any of the known line emission peaks that have been identified in other molecular tracers, with the exception of HCO. Our data suggest that water and ionised water within this region have high (up to 75%) area-covering factors of the underlying continuum. This indicates that water is not associated with small, dense cores within the ISM of M82 but arises from a more widespread diffuse gas component.Comment: 5 pages, 4 figures. Accepted for publication in A&

Whole genome transcription profiling of <it>Anaplasma phagocytophilum </it>in human and tick host cells by tiling array analysis

<p>Abstract</p> <p>Background</p> <p><it>Anaplasma phagocytophilum </it>(<it>Ap</it>) is an obligate intracellular bacterium and the agent of human granulocytic anaplasmosis, an emerging tick-borne disease. <it>Ap </it>alternately infects ticks and mammals and a variety of cell types within each. Understanding the biology behind such versatile cellular parasitism may be derived through the use of tiling microarrays to establish high resolution, genome-wide transcription profiles of the organism as it infects cell lines representative of its life cycle (tick; ISE6) and pathogenesis (human; HL-60 and HMEC-1).</p> <p>Results</p> <p>Detailed, host cell specific transcriptional behavior was revealed. There was extensive differential <it>Ap </it>gene transcription between the tick (ISE6) and the human (HL-60 and HMEC-1) cell lines, with far fewer differentially transcribed genes between the human cell lines, and all disproportionately represented by membrane or surface proteins. There were <it>Ap </it>genes exclusively transcribed in each cell line, apparent human- and tick-specific operons and paralogs, and anti-sense transcripts that suggest novel expression regulation processes. Seven <it>virB2 </it>paralogs (of the bacterial type IV secretion system) showed human or tick cell dependent transcription. Previously unrecognized genes and coding sequences were identified, as were the expressed <it>p44/msp2 </it>(major surface proteins) paralogs (of 114 total), through elevated signal produced to the unique hypervariable region of each – 2/114 in HL-60, 3/114 in HMEC-1, and none in ISE6.</p> <p>Conclusion</p> <p>Using these methods, whole genome transcription profiles can likely be generated for <it>Ap</it>, as well as other obligate intracellular organisms, in any host cells and for all stages of the cell infection process. Visual representation of comprehensive transcription data alongside an annotated map of the genome renders complex transcription into discernable patterns.</p

Efficient simulation of chemical reactions and dust destruction in accretion disks

Simulation of chemical reactions, e.g. in astrophysics, mostly leads to large systems of stiff differential equations. For the integration of such systems implicit methods are required. We present an efficient BDF-method and give a detailed description of the error and step size control and the strategies to minimize the effort of the linear algebra problems. Typical applications for chemical processes (chemistry and dust destruction) in an accretion disk are treated with this method. The code turned out to be more robust and much faster (more than a factor of 50) than the more conventional one used first. (orig.)SIGLEAvailable from TIB Hannover: RR 1606(95-28) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman