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Line profiles with and without thermal (i.e. Doppler) broadening in a simulation. The strength of the un-broadened lines are dependent on the spectral resolution of the code, and so we arbitrarily rescale the intensity to allow a closer comparison with the thermal broadened lines. These lines are sight-lines through the BHighRes model at an elevation angle of 0 • (i.e. edge-on) and an azimuthal angle of 45 • .
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Observations (e.g. Phillips, Heckman et al., Martin) have revealed cold gas with large velocity dispersions (≈300 km s−1) within the hot outflows of ultraluminous infrared galaxies (ULIRGs). This gas may trace its origin to the Rayleigh–Taylor
(RT) fragmentation of a super-bubble or may arise on smaller scales. We model a ULIRG outflow at two scale...
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In this paper we propose a generalized method for stochastic measurement of power grid frequency. The generalization consists of replacing the input two-bit A/D flash converters with m-bit flash A/D converters, where m ≤ 4. The proposed method is highly robust against signal distortions, even in the case when all harmonics have the maximum allowed...
Citations
... Since the presence of a bulge stabilizes the gas against gravitational instability, only the contribution to the potential from a disc was included. Galaxies with this set-up may settle to conditions similar to those of gas-rich, high-redshift galactic discs that do not yet have a bulge, or to those in the nuclei of post-merger highredshift galaxies (Williamson et al. 2014). ...
A suite of idealized, global, gravitationally unstable, star-forming galactic disc simulations with 2 pc spatial resolution, performed with the adaptive mesh refinement code ramses, is used in this paper to predict the emergent effects of supernova feedback. The simulations include a simplified prescription for the formation of single stellar populations of mass $\sim 100 \, {\rm M}_{\odot }$, radiative cooling, photoelectric heating, an external gravitational potential for a dark matter halo and an old stellar disc, self-gravity, and a novel implementation of supernova feedback. The results of these simulations show that gravitationally unstable discs can generate violent supersonic winds with mass-loading factors η ≳ 10, followed by a galactic fountain phase. These violent winds are generated by highly clustered supernovae exploding in dense environments created by gravitational instability, and they are not produced in simulation without self-gravity. The violent winds significantly perturb the vertical structure of the disc, which is later re-established during the galactic fountain phase. Gas resettles into a quasi-steady, highly turbulent disc with volume-weighted velocity dispersion $\sigma \gt 50 \, {\rm km\, s}^{-1}$. The new configuration drives weaker galactic winds with a mass-loading factor η ≤ 0.1. The whole cycle takes place in ≤10 dynamical times. Such high time variability needs to be taken into account when interpreting observations of galactic winds from starburst and post-starburst galaxies.
... Since the presence of a bulge stabilises the gas against gravitational instability, only the contribution to the potential from a disc was included. Galaxies with this setup may settle to conditions similar to those of gas-rich, high-redshift galactic discs that do not yet have a bulge, or to those in the nuclei of post-merger high-redshift galaxies (Williamson et al. 2014). ...
A suite of idealised, global, gravitationally unstable, star-forming galactic disc simulations with 2 pc spatial resolution, performed with the adaptive mesh refinement code RAMSES is used in this paper to predict the emergent effects of supernova feedback. The simulations include a simplified prescriptions for formation of single stellar populations of mass $\sim 100 \, M_{\odot}$, radiative cooling, photoelectric heating, an external gravitational potential for a dark matter halo and an old stellar disc, self-gravity, and a novel implementation of supernova feedback. The results of these simulations show that gravitationally unstable discs can generate violent supersonic winds with mass loading factors $\eta \gtrsim 10$, followed by a galactic fountain phase. These violent winds are generated by highly clustered supernovae exploding in dense environments created by gravitational instability, and they are not produced in simulation without self-gravity. The violent winds significantly perturb the vertical structure of the disc, which is later re-established during the galactic fountain phase. Gas resettles into a quasi-steady, highly turbulent disc with volume-weighted velocity dispersion $\sigma > 50 \, {\rm km/s}$. The new configuration drives weaker galactic winds with mass loading factor $\eta \leq 0.1$. The whole cycle takes place in $\leq 10$ dynamical times. Such high time variability needs to be taken into account when interpreting observations of galactic winds from starburst and post-starburst galaxies.
Winds arising from galaxies, star clusters, and active galactic nuclei are crucial players in star and galaxy formation, but it has proven remarkably difficult to use observations of them to determine physical properties of interest, particularly mass fluxes. Much of the difficulty stems from a lack of a theory that links a physically-realistic model for winds' density, velocity, and covering factors to calculations of light emission and absorption. In this paper we provide such a model. We consider a wind launched from a turbulent region with a range of column densities, derive the differential acceleration of gas as a function of column density, and use this result to compute winds' absorption profiles, emission profiles, and emission intensity maps in both optically thin and optically thick species. The model is sufficiently simple that all required computations can be done analytically up to straightforward numerical integrals, rendering it suitable for the problem of deriving physical parameters by fitting models to observed data. We show that our model produces realistic absorption and emission profiles for some example cases, and argue that the most promising methods of deducing mass fluxes are based on combinations of absorption lines of different optical depths, or on combining absorption with measurements of molecular line emission. In the second paper in this series, we expand on these ideas by introducing a set of observational diagnostics that are significantly more robust that those commonly in use, and that can be used to obtain improved estimates of wind properties.
Our three-dimensional hydro-dynamical simulations of starbursts examine the
formation of superbubbles over a range of driving luminosities and mass
loadings which determine superbubble growth and wind velocity. From this we
determine the relationship between the velocity of a galactic wind and the
power of the starburst. We find a threshold for the formation of a wind, above
which the speed of the wind is not affected by grid resolution or the
temperature floor of our radiative cooling. We investigate the effect two
different temperature floors in our radiative cooling prescription have on wind
kinematics and content. We find that cooling to $10$ K instead of to $10^4$ K
increases the mass fraction of cold neutral and hot X-ray gas in the galactic
wind while halving that in warm H$\alpha$. Our simulations show the mass of
cold gas transported into the lower halo does not depend on the starburst
strength. Optically bright filaments form at the edge of merging superbubbles,
or where a cold dense cloud has been disrupted by the wind. Filaments formed by
merging superbubbles will persist and grow to $>400$ pc in length if anchored
to a star forming complex. Filaments embedded in the hot galactic wind contain
warm and cold gas which moves $300-1200$ km s$^{-1}$ slower than the
surrounding wind, with the coldest gas hardly moving with respect to the
galaxy. Warm and cold matter in the galactic wind show asymmetric absorption
profiles consistent with observations, with a thin tail up to the wind
velocity.
We present the best sensitivity and angular resolution maps of the molecular
disk and outflow of Mrk 231, as traced by CO observations obtained with
IRAM/PdBI, and we analyze archival Chandra and NuSTAR observations. We
constrain the physical properties of both the molecular disk and outflow, the
presence of a highly-ionized ultra-fast nuclear wind, and their connection. The
molecular outflow has a size of ~1 kpc, and extends in all directions around
the nucleus, being more prominent along the south-west to north-east direction,
suggesting a wide-angle biconical geometry. The maximum projected velocity of
the outflow is nearly constant out to ~1 kpc, thus implying that the density of
the outflowing material decreases from the nucleus outwards as $r^{-2}$. This
suggests that either a large part of the gas leaves the flow during its
expansion or that the bulk of the outflow has not yet reached out to ~1 kpc,
thus implying a limit on its age of ~1 Myr. We find $\dot M_{OF}=[ 500-1000]~
M_{\odot}~yr^{-1}$ and $\dot E_{kin,OF}=[7-10]\times 10^{43}$ erg s$^{-1}$.
Remarkably, our analysis of the X-ray data reveals a nuclear ultra-fast outflow
(UFO) with velocity -20000 km s$^{-1}$, $\dot M_{UFO}=[0.3- 2.1] ~M_\odot
yr^{-1}$, and momentum load $\dot P_{UFO}/\dot P_{rad}=[0.2-1.6]$.We find $\dot
E_{kin,UFO}\sim \dot E_{kin,OF}$ as predicted for outflows undergoing an energy
conserving expansion. This suggests that most of the UFO kinetic energy is
transferred to mechanical energy of the kpc-scale outflow, strongly supporting
that the energy released during accretion of matter onto super-massive black
holes is the ultimate driver of giant massive outflows. We estimate a momentum
boost $\dot P_{OF}/\dot P_{UFO}\approx [30-60]$. The ratios $\dot E_{kin,
UFO}/L_{bol,AGN} =[ 1-5]\%$ and $\dot E_{kin,OF}/L_{bol,AGN} = [1-3]\%$ agree
with the requirements of the most popular models of AGN feedback.
