Clues to the origin of Fermi Bubbles from OVIII/OVII line ratio

We constrain the origin of Fermi Bubbles using 2D hydrodynamical simulations of both star formation driven and black hole accretion driven wind models. We compare our results with recent observations of OVIII to OVII line ratio within and near Fermi Bubbles. Our results suggest that independent of the driving mechanisms, a low luminosity ($\mathcal{L} \sim 0.7-1\times 10^{41}$ erg s$^{-1}$) energy injection best reproduces the observed line ratio for which the shock temperature is $\approx 3\times 10^6$ K. Assuming the Galactic halo temperature to be $2\times 10^6$K, we estimate the shock velocity to be $\sim 300$ km s$^{-1}$ for a weak shock. The corresponding estimated age of the Fermi bubbles is $\sim 15-25$ Myr. Such an event can be produced either by a star formation rate of $\sim 0.5$ M$_\odot$ yr$^{-1}$ at the Galactic centre or a very low luminosity jet/accretion wind arising from the central black hole. Our analysis rules out any activity that generates an average mechanical luminosity $\gtrsim 10^{41}$ \ergps as a possible origin of the Fermi Bubbles.Comment: 14 pages, 9 figures, accepted version (MNRAS); includes updates on the electron-proton equilibrium time scale and its implications for high energy jet

Tungsten disulfide-multiwalled carbon nanotube hybrid anode for lithium-ion battery

The present work is focused on the preparation of tungsten disulfide-multiwalled carbon nanotube (WS2-MWCNT) hybrids by simple dry grinding of WS2 and MWCNT in different proportion by weight (1:3, 1:1, 3:1). The as prepared hybrids have been characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), high resolution transmission electron microscopy (HRTEM) and Raman analyses. XRD results indicated complete exfoliation of MWCNT among WS2 particles in WS2-MWCNT (3:1) and (1:1) hybrids. FESEM images showed the formation of a 3-D network in WS2-MWCNT (1:1) hybrid with uniform dispersion of MWCNT being evident from HRTEM images. Raman analysis also suggested significant interaction between WS2 and MWCNT. WS2-MWCNT (1:1) hybrid, when used as anode material in lithium ion battery, exhibited a high initial charge capacity (483 mA h g(-1)) and an improved cycling stability with over 80% retention of the first cycle capacity after 20 cycles compared to only 40% capacity retention in pristine WS2. Such enhanced electrochemical performance of WS2-MWCNT (1:1) hybrid has been attributed to synergistic effect of WS2 and MWCNT

TiS2-MWCNT hybrid as high performance anode in lithium-ion battery

The present work reports the preparation of hybrids by simple dry grinding of titanium sulfide (TiS2) and multi-walled carbon nanotubes(MWCNTs) in different weight ratio and their characterization. X-ray diffraction and Raman studies indicated the presence of interaction between the TiS2 and MWCNT. Field emission scanning electron microscopy and high resolution transmission electron microscopy showed the formation of three-dimensional architecture and co-dispersion in TiS2-MWCNT (1:1) hybrid. X-ray photoelectron spectroscopy also confirmed the presence of TiS2 and MWCNT in the prepared hybrid. Thermogravimetric analysis indicated an increase in thermal stability with higher MWCNT content. The results of the electrochemical analyses indicated that TiS2-MWCNT (1:1) hybrid exhibited an enhanced performance as lithium-ion battery anode. The initial specific capacity was found to be approximate to 450 mAh g(-1) with 80 % retention in capacity after 50 discharge-charge cycles. These values are significantly higher compared to those for TiS2, MWCNT or other TiS2-MWCNT hybrids. Such improved performance is attributed to the presence of a synergistic effect between TiS2 and MWCNT

Review 1994

SIGLEAvailable from British Library Document Supply Centre- DSC:7768.388(1994) / BLDSC - British Library Document Supply CentreGBUnited Kingdo

Long way to go: how outflows from large galaxies propagate through the hot halo gas

Using hydrodynamic simulations, we study the mass-loss due to supernova-driven outflows from Milky Way type disc galaxies, paying particular attention to the effect of the extended hot halo gas. We find that the total mass-loss at inner radii scales roughly linearly with total mass of stars formed, and that the mass loading factor at the virial radius can be several times its value at inner radii because of the swept up hot halo gas. The temperature distribution of the outflowing material in the inner region (similar to 10 kpc) is bimodal in nature, peaking at 10(5) K and 10(6.5) K, responsible for optical and X-ray emission, respectively. The contribution of cold/warm gas with temperature <= 10(5.5) K to the outflow rate within 10 kpc is approximate to 0.3-0.5. The warm mass loading factor, eta(3e5) (T <= 3 x 10(5) K) is related to the mass loading factor at the virial radius (eta(v)) as eta(v) approximate to 25 eta(3e5) (SFR/M-circle dot yr(-1))(-0.15) for a baryon fraction of 0.1 and a starburst period of 50 Myr. We also discuss the effect of multiple bursts that are separated by both short and long periods. The outflow speed at the virial radius is close to the sound speed in the hot halo, less than or similar to 200 km s(-1). We identify two `sequences' of outflowing cold gas at small scales: a fast (approximate to 500 km s(-1)) sequence, driven by the unshocked free-wind; and a slow sequence (approximate to +/- 100 km s(-1)) at the conical interface of the superwind and the hot halo