Atomic Chemistry in Turbulent Astrophysical Media. Ii. Effect of the Redshift Zero Metagalactic Background

Gray, Whitmore; Scannapieco, Evan

doi:10.3847/0004-637x/818/2/198

Cited by 22 publications

(32 citation statements)

References 76 publications

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“…To this end, we can turn again to the example presented in Figure 1. Gray et al (2015); Gray & Scannapieco (2016); Buie et al (2018) showed that at low amounts of turbulence, σ 3D 10 km s −1 (top panel), MAIHEM mass fractions agree well with the pure photoionization case computed with CLOUDY (Ferland et al 2013).…”

Section: Application To Cos-halos Datasupporting

confidence: 52%

“…Modifications for solving the hydrodynamic equations include using an unsplit solver based on Lee (2013) as well as a hybrid Riemann solver that utilizes the Harten Lax and van Leer (HLL) solver (Einfeldt et al 1991) to ensure stability in regions of strong shocks, and the Harten-Lax-van Leer-Contact (HLLC) solver (Toro et al 1994;Toro 1999) in continuous flows. MAIHEM was initially presented in Gray et al (2015) and further improved upon in Gray & Scannapieco (2016) and Gray & Scannapieco (2017).…”

Section: Maihem Modelsmentioning

confidence: 99%

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Interpreting Observations of Absorption Lines in the Circumgalactic Medium with a Turbulent Medium

Buie

Fumagalli

Scannapieco

2020

ApJ

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Single-phase photoionization equilibrium (PIE) models are often used to infer the underlying physical properties of galaxy halos probed in absorption with ions at different ionization potentials. To incorporate the effects of turbulence, we use the MAIHEM code to model an isotropic turbulent medium exposed to a redshift zero metagalactic UV background, while tracking the ionizations, recombinations, and species-by-species radiative cooling for a wide range of ions. By comparing observations and simulations over a wide range of turbulent velocities, densities, and metallicity with a Markov chain Monte Carlo technique, we find that MAIHEM models provide an equally good fit to the observed low-ionization species compared to PIE models, while reproducing at the same time high-ionization species such as Si IV and O VI. By including multiple phases, MAIHEM models favor a higher metallicity (Z/Z ≈ 40%) for the circumgalactic medium compared to PIE models. Furthermore, all of the solutions require some amount of turbulence (σ 3D 26 km s −1 ). Correlations between turbulence, metallicity, column density, and impact parameter are discussed alongside mechanisms that drive turbulence within the halo.

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Section: Application To Cos-halos Datasupporting

confidence: 52%

Section: Maihem Modelsmentioning

confidence: 99%

Interpreting Observations of Absorption Lines in the Circumgalactic Medium with a Turbulent Medium

Buie

Fumagalli

Scannapieco

2020

ApJ

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“…3.3). (1) [13] 10 −6 -10 15 cm −3 1D 625 species (including atomic ions); CHIANTI, Stout, LAMDA databases no (9) DESPOTIC (2) [31] Cool atomic and molecular ISM 1D C, O, H, and He, plus a super-species M that represents a composite of metallic elements no (9) LIME (3) [26] 10 2 -10 12 cm −3 3D LAMDA database yes MAIHEM (4) [32], [65], [66] Has been tested at 0.4-1200 cm −3…”

Section: Tools For Solving Level Populations and Line Excitationmentioning

confidence: 99%

Challenges and Techniques for Simulating Line Emission

et al. 2018

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Modeling emission lines from the millimeter to the UV and producing synthetic spectra is crucial for a good understanding of observations, yet it is an art filled with hazards. This is the proceedings of "Walking the Line", a 3-day conference held in 2018 that brought together scientists working on different aspects of emission line simulations, in order to share knowledge and discuss the methodology. Emission lines across the spectrum from the millimeter to the UV were discussed, with most of the focus on the interstellar medium, but also some topics on the circumgalactic medium. The most important quality of a useful model is a good synergy with observations and experiments. Challenges in simulating line emission are identified, some of which are already being worked upon, and others that must be addressed in the future for models to agree with observations. Recent advances in several areas aiming at achieving that synergy are summarized here, from micro-physical to galactic and circum-galactic scale.2 of 29 us to characterize the mass, composition, and chemical state of the ISM, as well as to trace galaxy properties such as star formation rate (SFR), metallicity and dynamics. For example, the emission from major cooling lines, such as Hα or [C II], is sensitive to the physical conditions (densities, radiation field) and dynamics of the ISM. In addition, emission lines work on all physical scales, from galaxy dynamics and inflows to turbulent and collapse motions in star-forming clouds and cores. By systematically comparing spectral-line signatures of different physical models, one can correctly identify the physical processes occurring in these regions. Furthermore, the emission from ionized interstellar gas contains particularly valuable information about the nature of the ionizing radiation sources in a galaxy. In fact, prominent optical emission lines are routinely used to estimate whether ionization is dominated by young massive stars (tracing SFR), an AGN or evolved, post-asymptotic giant branch (post-AGB) stars. Three of the most widely used line-ratio diagnostic "BPT" diagrams 1 , relate the [OIII]/Hβ ratio to the [NII]/Hα, [SII]/Hα and [OI]/Hα ratios. These diagrams have proven useful in identifying the nature of the ionizing radiation in large samples of galaxies in the local Universe [2,3]. Complementary to line emission are the observations of absorption lines of the circumgalactic medium (CGM), which can give key information on the history of the feedback, in terms of chemical, ionization, and thermodynamical state of the outflowing/inflowing gas, that regulates the star formation process. Gas kinematics, from both emission and absorption, give information about large scale gas flows. Thus galactic outflows, from active galactic nuclei (AGN) and starbursts, can be combined with CGM absorption line observations, to study the star formation history, AGN activity history, and feedback processes that regulate both the evolution of the galaxy and its environment.Looking back on the past three decades, t...

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“…It is with these issues in mind that we carry out a set of numerical calculations of turbulent astrophysical media exposed to a radiation field with a blackbody spectral shape, making use of the atomic chemistry network discussed in Gray & Scannapieco (2016). Like in Gray & Scan-napieco (2016), we catalog the hydrodynamical and chemical properties, but unlike this previous work, we also compute the average line emission.…”

Section: Introductionmentioning

confidence: 99%

“…The effect of turbulence on the steady state ionization fractions for several important astronomical elements has been studied both with (Gray & Scannapieco 2016) and without (Gray et al 2015) an ionizing UV background. In Gray et al (2015), we found that gas approximates a lognormal distribution with a variance that is well modeled, for supersonic turbulence, by…”

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confidence: 99%

The Effect of Turbulence on Nebular Emission Line Ratios

Gray

Scannapieco

2017

ApJ

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Motivated by the observed differences in the nebular emission of nearby and high-redshift galaxies, we carry out a set of direct numerical simulations of turbulent astrophysical media exposed to a UV background. The simulations assume a metallicity of Z/Z =0.5 and explicitly track ionization, recombination, charge transfer, and ion-by-ion radiative cooling for several astrophysically important elements. Each model is run to a global steady state that depends on the ionization parameter U , and the one-dimensional turbulent velocity dispersion, σ 1D , and the turbulent driving scale. We carry out a suite of models with a T=42,000K blackbody spectrum, n e = 100 cm −3 and σ 1D ranging between 0.7 to 42 km s −1 , corresponding to turbulent Mach numbers varying between 0.05 and 2.6. We report our results as several nebular diagnostic diagrams and compare them to observations of star-forming galaxies at a redshift of z ≈2.5, whose higher surface densities may also lead to more turbulent interstellar media. We find that subsonic, transsonic turbulence, and turbulence driven on scales of 1 parsec or greater, have little or no effect on the line ratios. Supersonic, small-scale turbulence, on the other hand, generally increases the computed line emission. In fact with a driving scale ≈ 0.1 pc, a moderate amount of turbulence, σ 1D =21-28 km s −1 , can reproduce many of the differences between high and low redshift observations without resorting to harder spectral shapes.

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Atomic Chemistry in Turbulent Astrophysical Media. Ii. Effect of the Redshift Zero Metagalactic Background

Cited by 22 publications

References 76 publications

Interpreting Observations of Absorption Lines in the Circumgalactic Medium with a Turbulent Medium

Interpreting Observations of Absorption Lines in the Circumgalactic Medium with a Turbulent Medium

Challenges and Techniques for Simulating Line Emission

The Effect of Turbulence on Nebular Emission Line Ratios

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