Fermi-LAT Observations of Supernova Remnant Kesteven 79

In this paper we report on the detection of $\gamma$-ray emission coincident with the Galactic supernova remnant Kesteven 79 (Kes 79). We analysed approximately 52 months of data obtained with the Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope. Kes 79 is thought to be interacting with adjacent molecular clouds based on the presence of strong $^{12}$CO J = 1 $\rightarrow$ 0 and HCO$^{+}$ J = 1 $\rightarrow$ 0 emission and the detection of 1720 MHz line emission towards the east of the remnant. Acceleration of cosmic rays is expected to occur at SNR shocks, and SNRs interacting with dense molecular clouds provide a good testing ground for detecting and analysing the production of $\gamma$-rays from the decay of $\pi^0$ into two $\gamma$-ray photons. This analysis investigates $\gamma$-ray emission coincident with Kes 79, which has a detection significance of $\sim 7 \sigma$. Additionally we present an investigation of the spatial and spectral characteristics of Kes 79 using multiple archival XMM-Newton observations of this remnant. We determine the global X-ray properties of Kes 79 and estimate the ambient density across the remnant. We also performed a similar analysis for Galactic SNR Kesteven 78 (Kes 78), but due to large uncertainties in the $\gamma$-ray background model, no conclusion can be made about an excess of GeV $\gamma$-ray associated with the remnant.Comment: Accepted by ApJ; 16 pages, 5 figures, 6 table

FERMI-LAT Observations of Supernova Remnant G5.7-0.1, Believed to be Interacting with Molecular Clouds

This work reports on the detection of $\gamma$-ray emission coincident with the supernova remnant (SNR) SNR G5.7-0.1 using data collected by the Large Area Telescope aboard the Fermi Gamma-ray Space Telescope. The SNR is believed to be interacting with molecular clouds, based on 1720 MHz hydroxyl (OH) maser emission observations in its direction. This interaction is expected to provide targets for the production of $\gamma$-ray emission from $\pi^0$-decay. A $\gamma$-ray source was observed in the direction of SNR G5.7-0.1, positioned nearby the bright $\gamma$-ray source SNR W28. We model the emission from radio to $\gamma$-ray energies using a one-zone model. Following consideration of both $\pi^0$-decay and leptonically dominated emission scenarios for the MeV-TeV source, we conclude that a considerable component of the $\gamma$-ray emission must originate from the $\pi^0$-decay channel. Finally, constraints were placed on the reported ambiguity of the SNR distance through X-ray column density measurements made using XMM-Newton observations. We conclude SNR G5.7-0.1 is a significant $\gamma$-ray source positioned at a distance of $\sim 3$ kpc with luminosity in the 0.1--100 GeV range of $L_{\gamma} \approx 7.4 \times 10^{34}$ erg/s.Comment: 8 pages, 5 figures, 1 table, Accepted for publication in Ap

Fermi LAT Observations of Supernova Remnants Interacting with Molecular Clouds: W41, MSH 17-39, and G337.0-0.1

We report the detection of gamma-ray emission coincident with three supernova remnants (SNRs) using data from the Large Area Telescope on board the Fermi Gamma-ray Space Telescope. W41, MSH 17-39, and G337.0-0.1 are SNRs known to be interacting with molecular clouds, as evidenced by observations of hydroxyl (OH) maser emission at 1720 MHz in their directions and other observational information. SNR shocks are expected to be sites of cosmic ray acceleration, and clouds of dense material can provide effective targets for production of gamma-rays from neutral pion-decay. The observations reveal unresolved sources in the direction of G337.0-0.1, and MSH 17-39, and an extended source coincident with W41. We model their broadband emission (radio to gamma-ray) using a simple one-zone model, and after considering scenarios in which the MeV-TeV sources originate from either neutral pion-decay or leptonic emission, we conclude that the gamma-rays are most likely produced through the hadronic channel.Comment: 9 pages, 11 figures, accepted for publication in Ap

Multi-wavelength analysis of the Galactic supernova remnant MSH 11-61A

Due to its centrally bright X-ray morphology and limb brightened radio profile, MSH 11-61A (G290.1-0.8) is classified as a mixed morphology supernova remnant (SNR). H\textsc{i} and CO observations determined that the SNR is interacting with molecular clouds found toward the north and southwest regions of the remnant. In this paper we report on the detection of $\gamma$-ray emission coincident with MSH 11-61A, using 70 months of data from the Large Area Telescope on board the \textit{Fermi Gamma-ray Space Telescope}. To investigate the origin of this emission, we perform broadband modelling of its non-thermal emission considering both leptonic and hadronic cases and concluding that the $\gamma$-ray emission is most likely hadronic in nature. Additionally we present our analysis of a 111 ks archival \textit{Suzaku} observation of this remnant. Our investigation shows that the X-ray emission from MSH 11-61A arises from shock-heated ejecta with the bulk of the X-ray emission arising from a recombining plasma, while the emission towards the east arises from an ionising plasma.Comment: 12 Pages, 8 figures. Accepted for publication in the Astrophysical Journa

Analyse zur globalen Genexpression in Geweben des frühen Arabidopsis thaliana Embryos

Die Entstehung vielzelliger Eukaryonten bestehend aus unterschiedlichsten Zell- sowie Gewebetypen beruht auf zellulären Differenzierungsprozessen von pluripotenten und nicht endgültig differenzierten Zellen. Damit diese Stammzellen in Zellen mit spezifischen Aufgaben differenziert werden können, ist eine Veränderung der zellulären Genexpression grundlegend. Daher ist das Wissen über unterschiedliche Genexpressionsmuster sowie deren Zustandekommen unerlässlich für ein tieferes Verständnis von entwicklungsbiologischen Aspekten. Bei den Bedecktsamern (Angiospermen) wie der Ackerschmalwand (Arabidopsis thaliana) wird der Grundbauplan während der frühen Embryogenese ausgebildet. Dabei sind bereits im sogenannten embryonalen Herzstadium alle drei Achsen (apikal-basale, radiale, bilaterale), das Spross- sowie das Wurzelmeristems, die beiden Keimblätter (Kotyledonen) und das Hypokotyl festgelegt. Zu Beginn der Embryogenese markiert in Arabidopsis bereits die erste Zellteilung der Zygote die apikal-basale Symmetrieebene, wobei die beiden daraus resultierenden Tochterzellen in der Folge grundlegend verschiedene Entwicklungsrichtungen einschlagen. Während die Nachkommen der apikale Zelle durch Teilungen in verschiedenen Ebenen einen sphärischen Zellverband, den sogenannten Proembryo ausbilden, teilen sich die Nachkommen der basalen Zelle ausschliesslich horizontal und es entsteht dadurch eine einzige Zellreihe, der sogenannte Suspensor. Aufgrund seiner geringen Größe und der Tatsache, dass der Embryo bei Blütenpflanzen meist sehr tief im maternalen Gewebe eingebettet ist, waren Untersuchungen auf Transkriptomebene in der Vergangenheit kaum möglich. In dieser Arbeit wurde exemplarisch am frühen Arabidopsis Embryo eine Methode entwickelt, mit deren Hilfe Genexpressionsprofile von Zellkernen des Proembryos und des Suspensors sowie auch des gesamten Embryos erstellt wurden. Dafür wurden gewebespezifische Markerlinien in Pflanzen etabliert, deren extrahierte Kerne mittels fluoreszenzbasierter Durchflusszytometrie, sogenanntem fluorescence-activated nuclear sorting (FANS) aufgereinigt wurden. Schliesslich wurde die Boten-RNA (mRNA) der Zellkerne über DNA-Microarrays analysiert. Durch Vergleich mit dem Genexpressionsprofil aus Zellen ganzer, intakter Embryonen vergleichbaren, embryonalen Stadiums konnte die Ähnlichkeit von Kernen und Zellen auf der Ebene der Genexpression gezeigt werden. Die statistisch signifikanten Unterschiede im Genexpressionsmuster zwischen apikalem und basalem Embryonalgewebe wurden in vivo mittels Promoter-Reporter Fusionskonstrukten sowie RNA in situ Hybridisierung verifiziert. Überdies konnte gezeigt werden, dass die hier vorgestellte Methode Vorteile gegenüber der vormals angewendeten Laser-Mikrodissektion bietet. Mit dieser Methode sollte es möglich sein, aus schwerzugänglichen Geweben mit geringer Zellzahl auch in anderen Organismen verlässliche Genexpressionsprofile herzustellen. Die Ergebnisse dieser Arbeit liefern ausserdem eine nützliche Datenbank auf transkriptioneller Ebene für zukünftige Studien in der frühen Embryogenese von Arabidopsis thaliana

High-Energy Emission from the Composite Supernova Remnant MSH 15-56

MSH 15-56 (G326.3-1.8) is a composite supernova remnant (SNR) that consists of an SNR shell and a displaced pulsar wind nebula (PWN) in the radio. We present XMM-Newton and Chandra X-ray observations of the remnant that reveal a compact source at the tip of the radio PWN and complex structures that provide evidence for mixing of the supernova (SN) ejecta with PWN material following a reverse shock interaction. The X-ray spectra are well fitted by a non-thermal power-law model whose photon index steepens with distance from the presumed pulsar, and a thermal component with an average temperature of 0.55 keV. The enhanced abundances of silicon and sulfur in some regions, and the similar temperature and ionization timescale, suggest that much of the X-ray emission can be attributed to SN ejecta that have either been heated by the reverse shock or swept up by the PWN. We find one region with a lower temperature of 0.3 keV that appears to be in ionization equilibrium. Assuming the Sedov model, we derive a number of SNR properties, including an age of 16,500 yr. Modeling of the gamma-ray emission detected by Fermi shows that the emission may originate from the reverse shock-crushed PWN.Comment: 11 pages, 3 tables, 8 figures, accepted for publication in The Astrophysical Journa

A CR-hydro-NEI Model of Multi-wavelength Emission from the Vela Jr. Supernova Remnant (SNR RX J0852.0-4622)

Based largely on energy budget considerations and the observed cosmic-ray (CR) ionic composition, supernova remnant (SNR) blast waves are the most likely sources of CR ions with energies at least up to the "knee" near 3 PeV. Shocks in young shell-type TeV-bright SNRs are surely producing TeV particles, but the emission could be dominated by ions producing neutral pion-decay emission or electrons producing inverse-Compton gamma-rays. Unambiguously identifying the GeV-TeV emission process in a particular SNR will not only help pin down the origin of CRs, it will add significantly to our understanding of the diffusive shock acceleration (DSA) mechanism and improve our understanding of supernovae and the impact SNRs have on the circumstellar medium. In this study, we investigate the Vela Jr. SNR, an example of TeV-bright non-thermal SNRs. We perform hydrodynamic simulations coupled with non-linear DSA and non-equilibrium ionization near the forward shock (FS) to confront currently available multi-wavelength data. We find, with an analysis similar to that used earlier for SNR RX J1713.7-3946, that self-consistently modeling the thermal X-ray line emission with the non-thermal continuum in our one-dimensional model strongly constrains the fitting parameters, and this leads convincingly to a leptonic origin for the GeV-TeV emission for Vela Jr. This conclusion is further supported by applying additional constraints from observation, including the radial brightness profiles of the SNR shell in TeV gamma-rays, and the spatial variation of the X-ray synchrotron spectral index. We will discuss implications of our models on future observations by the next-generation telescopes.Comment: 12 pages, 10 figures, to appear at the Astrophysical Journa