Writing Well

Norman, Renee

doi:10.20360/g2n01r

Cited by 10 publications

(12 citation statements)

References 0 publications

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“…10 at λ i = 100 kpc as the injection scale, then we would get a lower limit of about 10 percent. The simulations of Norman & Bryan (1999) suggest additional support by turbulent pressure of about 20 percent, averaged over the cluster (5 to 35 percent between core and virial radius), which is apparently of the same order as the present observational limit. However, further study is definitely required in order to establish how the observational quantities relate to the simulation results.…”

Section: Discussionsupporting

confidence: 80%

“…Accretion flows through filaments and sheets are highly asymmetric and produce complex patterns which can survive for long time-scales in the ICM (Miniati et al 2000). Simulations by Norman & Bryan (1999) predict that the turbulent pressure in the ICM can account for up to 20% of the thermal pressure. We thus expect some measurable effects of turbulence in the ICM of clusters of galaxies.…”

Section: Introductionmentioning

confidence: 99%

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Probing turbulence in the Coma galaxy cluster

Schuecker¹,

Finoguenov²,

Miniati

et al. 2004

A&A

280

307

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Abstract. Spatially-resolved gas pressure maps of the Coma galaxy cluster are obtained from a mosaic of XMM-Newton observations in the scale range between a resolution of 20 kpc and an extent of 2.8 Mpc. A Fourier analysis of the data reveals the presence of a scale-invariant pressure fluctuation spectrum in the range between 40 and 90 kpc and is found to be well described by a projected Kolmogorov/Oboukhov-type turbulence spectrum. Deprojection and integration of the spectrum yields the lower limit of ∼10 percent of the total intracluster medium pressure in turbulent form. The results also provide observational constraints on the viscosity of the gas.

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Section: Discussionsupporting

confidence: 80%

Section: Introductionmentioning

confidence: 99%

Probing turbulence in the Coma galaxy cluster

Schuecker¹,

Finoguenov²,

Miniati

et al. 2004

A&A

280

307

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show abstract

“…We conducted our simulations with the structured adaptive mesh refinement (AMR) hydrodynamics code Enzo (Bryan 1999;Norman & Bryan 1999;O'Shea et al 2004). Enzo uses an Eulerian method for solving the hydrodynamics equations on a Cartesian grid.…”

Section: Methodsmentioning

confidence: 99%

The effect of feedback and reionization on star formation in low-mass dwarf galaxy haloes

Simpson

Bryan

Johnston

et al. 2013

Monthly Notices of the Royal Astronomical Society

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We simulate the evolution of a 10 9 M dark matter halo in a cosmological setting with an adaptive-mesh refinement code as an analogue to local low luminosity dwarf irregular and dwarf spheroidal galaxies. The primary goal of our study is to investigate the roles of reionization and supernova feedback in determining the star formation histories of low mass dwarf galaxies. We include a wide range of physical effects, including metal cooling, molecular hydrogen formation and cooling, photoionization and photodissociation from a metagalactic (but not local) background, a simple prescription for self-shielding, star formation, and a simple model for supernova driven energetic feedback. To better understand the impact of each physical effect, we carry out simulations excluding each major effect in turn. We find that reionization is primarily responsible for expelling most of the gas in our simulations, but that supernova feedback is required to disperse the dense, cold gas in the core of the halo. Moreover, we show that the timing of reionization can produce an order of magnitude difference in the final stellar mass of the system. For our full physics run with reionization at z = 9, we find a stellar mass of about 10 5 M at z = 0, and a mass-to-light ratio within the half-light radius of approximately 130 M /L , consistent with observed low-luminosity dwarfs. However, the resulting median stellar metallicity is 0.06 Z , considerably larger than observed systems. In addition, we find star formation is truncated between redshifts 4 and 7, at odds with the observed late time star formation in isolated dwarf systems but in agreement with Milky Way ultrafaint dwarf spheroidals. We investigate the efficacy of energetic feedback in our simple thermal-energy driven feedback scheme, and suggest that it may still suffer from excessive radiative losses, despite reaching stellar particle masses of about 100 M , and a comoving spatial resolution of 11 pc.

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“…Properties of turbulence in galaxy clusters were studied by means of numerical simulations (e.g., Dolag et al 2005;Cassano & Brunetti 2005;Norman & Bryan 1999;Iapichino et al 2011;Vazza et al 2011). However despite the good "global" agreement between all simulations, the results on turbulent motions are still controversial, mainly due to insufficient resolution of simulations and, in particular, low Reynolds number (effective Re < 1000 in cosmological simulations) and other numerical issues (see, e.g., Kitsionas et al 2009;Dobler et al 2003;Beresnyak & Lazarian 2009).…”

Section: Introductionmentioning

confidence: 99%

Constraints on the ICM velocity power spectrum from the X-ray lines width and shift

Zhuravleva¹,

Churazov²,

Kravtsov³

et al. 2012

Monthly Notices of the Royal Astronomical Society

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Future X‐ray observations of galaxy clusters by high spectral resolution missions will provide spatially resolved measurements of the energy and width for the brightest emission lines in the intracluster medium (ICM) spectrum. In this paper we discuss various ways of using these high‐resolution data to constrain velocity power spectrum in galaxy clusters. We argue that variations of these quantities with the projected distance R in cool core clusters contain important information on the velocity field length scales (i.e. the size of energy‐containing eddies) in the ICM. The effective length leff along the line of sight, which provides dominant contribution to the line flux, increases with R, allowing one to probe the amplitude of the velocity variations at different spatial scales. In particular, we show that the width of the line as a function of R is closely linked to the structure function of the 3D velocity field. Yet another easily obtainable proxy of the velocity field length scales is the ratio of the amplitude of the projected velocity field (line energy) variations to the dispersion of the velocity along the line of sight (line width). Finally the projected velocity field can be easily converted into 3D velocity field, especially for clusters like Coma with an extended flat core in the surface brightness. Under assumption of a homogeneous isotropic Gaussian 3D velocity field we derived simple expressions relating the power spectrum of the 3D velocity field (or structure function) and the observables. We illustrate the sensitivity of these proxies to changes in the characteristics of the power spectrum for a simple isothermal β‐model of a cluster. The uncertainties in the observables, caused by the stochastic nature of the velocity field, are estimated by making multiple realizations of the random Gaussian velocity field and evaluating the scatter in observables. If large‐scale motions are present in the ICM these uncertainties may dominate the statistical errors of line width and shift measurements.

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Writing Well

Cited by 10 publications

References 0 publications

Probing turbulence in the Coma galaxy cluster

Probing turbulence in the Coma galaxy cluster

The effect of feedback and reionization on star formation in low-mass dwarf galaxy haloes

Constraints on the ICM velocity power spectrum from the X-ray lines width and shift

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