H-alpha emission in local galaxies: star formation, time variability and the diffuse ionized gas

Tacchella, Sandro; Smith, Aaron; Kannan, Rahul; Marinacci, Federico; Hernquist, Lars; Vogelsberger, Mark; Torrey, Paul; Sales, Laura; Li, Hui

doi:10.48550/arxiv.2112.00027

Cited by 5 publications

(8 citation statements)

References 125 publications

(171 reference statements)

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“…Keeping this in mind, our estimates are roughly consistent with other post-processing results from simulations with a multiphase ISM (e.g. Kado-Fong et al 2020;Smith et al 2021;Tacchella et al 2021).…”

Section: Dust Absorptionsupporting

confidence: 89%

The THESAN project: ionizing escape fractions of reionization-era galaxies

Yeh¹,

Smith²,

Kannan³

et al. 2022

Preprint

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A fundamental requirement for reionizing the Universe is that a sufficient fraction of the ionizing photons emitted by galaxies successfully escapes into the intergalactic medium. However, due to the scarcity of high-redshift observational data, the sources driving reionization remain uncertain. In this work we calculate the ionizing escape fractions ( 𝑓 esc ) of reionization-era galaxies from the state-of-the-art simulations, which combine an accurate radiation-hydrodynamic solver ( -) with the well-tested IllustrisTNG galaxy formation model to self-consistently simulate both small-scale galaxy physics and large-scale reionization throughout a large patch of the universe (𝐿 box = 95.5 cMpc). This allows the formation of numerous massive haloes (𝑀 halo 10 10 M ), which are often statistically underrepresented in previous studies but are believed to be important to achieve rapid reionization. We find that low-mass galaxies (𝑀 stars 10 7 M ) are the main drivers of reionization above 𝑧 7, while high-mass galaxies (𝑀 stars 10 8 M ) dominate the escaped ionizing photon budget at lower redshifts. We find a strong dependence of 𝑓 esc on the effective star-formation rate (SFR) surface density defined as the SFR per gas mass per escape area, i.e. ΣSFR = SFR/𝑀 gas /𝑅 2 200 . The variation in halo escape fractions decreases for higher-mass haloes, which can be understood from the more settled galactic structure, SFR stability, and fraction of sightlines within each halo significantly contributing to the escaped flux. We show that dust is capable of reducing the escape fractions of massive galaxies, but the impact on the global 𝑓 esc depends on the dust model. Finally, AGN are unimportant for reionization in and their escape fractions are lower than stellar ones due to being located near the centres of galaxy gravitational potential wells.

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Section: Dust Absorptionsupporting

confidence: 89%

The THESAN project: ionizing escape fractions of reionization-era galaxies

Yeh¹,

Smith²,

Kannan³

et al. 2022

Preprint

Self Cite

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“…Similarly, the calibration shifts when varying between a Salpeter, Kroupa, and Chabrier IMF. Furthermore, Tacchella et al (2021) recently showed that additional corrections to standard scaling relations are needed for the absorption of Lyman continuum photons by dust and helium. Since simulations, in principle, can capture many (but not all) of these effects, we argue that they can be used to calibrate SFR-line luminosity relations.…”

Section: Star Formation Rate Indicatorsmentioning

confidence: 99%

RAMSES-RTZ: Non-Equilibrium Metal Chemistry and Cooling Coupled to On-The-Fly Radiation Hydrodynamics

Katz

2022

Preprint

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Emission and absorption lines from elements heavier than helium (metals) represent one of our strongest probes of galaxy formation physics across nearly all redshifts accessible to observations. The vast majority of simulations that model these metal lines often assume either collisional or photoionisation equilibrium, or a combination of the two. For the few simulations that have relaxed these assumptions, a redshift-dependent meta-galactic UV background or fixed spectrum is often used in the nonequilibrium photoionisation calculation, which is unlikely to be accurate in the interstellar medium where the gas can self-shield as well as in the high-redshift circumgalactic medium where locally emitted radiation may dominate over the UV background. In this work, we relax this final assumption by coupling the ionisation states of individual metals to the radiation hydrodynamics solver present in RAMSES-RT. Our chemical network follows radiative recombination, dielectronic recombination, collisional ionisation, photoionisation, and charge transfer and we use the ionisation states to compute non-equilibrium optically-thin metalline cooling. The fiducial model solves for the ionisation states of C, N, O, Mg, Si, S, Fe, and Ne in addition to H, He, and H 2 , but can be easily extended for other ions. We provide interfaces to two different ODE solvers that are competitive in both speed and accuracy. The code has been benchmarked across a variety of gas conditions to reproduce results from CLOUDY when equilibrium is reached. We show an example isolated galaxy simulation with on-the-fly radiative transfer that demonstrates the utility of our code for translating between simulations and observations without the use of idealised photoionisation models.

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“…One of these is the absorption of LyC radiation by dust: dust can absorb the LyC photons before they can ionise the hydrogen atoms, and re-emit them at longer wavelength. The typical fraction of LyC radiation absorbed by dust has been constrained to be of the order of 30 -50% in observations of nearby galaxies (Inoue et al 2001;Hirashita et al 2003;Iglesias-Páramo et al 2004;Salim et al 2016) as well as in simulations (Tacchella et al 2022).…”

Section: Photoionisation Budgetmentioning

confidence: 99%

“…There, Σ mol was derived from CO line intensity with a radially varying CO-to-H 2 conversion factor (following Sun et al 2020). A stellar mass surface density Σ ⋆ was derived from 3.6 µm SB with a varying stellar mass-to-light ratio (following Leroy et al 2021b), and then it was converted to ρ ⋆ with an estimated stellar disk scale height from the disk radial scale length H ⋆ = R ⋆ /7.3 (van der Kruit & Searle 1981;Sun et al 2020). A fixed gas velocity dispersion of σ gas, z = 10 km s −1 was adopted following Leroy et al (2008).…”

Section: Pressure Terms As Function Of Galactocentric Radiusmentioning

confidence: 99%

Stellar feedback in M 83 as observed with MUSE

Bruna

Adamo

McLeod

et al. 2022

A&A

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Context. Energy and momentum injected by young, massive stars into the surrounding gas play an important role in regulating further star formation and in determining the galaxy's global properties. Before supernovae begin to explode, stellar feedback consists of two main processes: radiation pressure and photoionisation. Aims. We study pre-supernova feedback and constrain the leakage of Lyman continuum (LyC) radiation in a sample of ∼ 4700 H ii regions in the nearby spiral galaxy M83. We explore the impact that the galactic environment and intrinsic physical properties (metallicity, extinction, and stellar content) have on the early phases of H ii region evolution. Methods. We combined VLT/MUSE observations of the ionised gas with young star cluster physical properties derived from HST multiwavelength data. We identified H ii regions based on their Hα emission, and cross-matched the sample with planetary nebulae and supernova remnants to assess contaminant sources and identify evolved H ii regions. We also spectroscopically identified Wolf-Rayet (WR) stars populating the star-forming regions. We estimated the physical properties of the H ii regions (luminosity, size, oxygen abundance, and electron density). For each H ii region, we computed the pressure of ionised gas (P ion ) and the direct radiation pressure (P dir ) acting in the region, and investigated how they vary with galactocentric distance, with the physical properties of the region, and with the pressure of the galactic environment (P DE ). For a subset of ∼ 500 regions, we also investigated the link between the pressure terms and the properties of the cluster population (age, mass, and LyC flux). By comparing the LyC flux derived from Hα emission with the one modelled from their clusters and WRs, we furthermore constrained any escape of LyC radiation ( f esc ). Results. We find that P ion dominates over P dir by at least a factor of 10 on average over the disk. Both pressure terms are strongly enhanced and become almost comparable in the central starburst region. In the disk (R ≥ 0.15 R e ), we observe that P dir stays approximately constant with galactocentric distance. We note that P dir is positively correlated with an increase in radiation field strength (linked to the negative metallicity gradient in the galaxy), while it decreases in low extinction regions, as is expected if the amount of dust to which the momentum can be imparted decreases. In addition, P ion decreases constantly for increasing galactocentric distances; this trend correlates with the decrease in extinction -indicative of more evolved and thus less compact regions -and with changes in the galactic environment (traced by a decrease in P DE ). In general, we observe that H ii regions near the centre are underpressured with respect to their surroundings, whereas regions in the rest of the disk are overpressured and hence expanding. We find that regions hosting younger clusters or those that have more mass in young star clusters have a higher internal pressure, indicating that clust...

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H-alpha emission in local galaxies: star formation, time variability and the diffuse ionized gas

Cited by 5 publications

References 125 publications

The THESAN project: ionizing escape fractions of reionization-era galaxies

The THESAN project: ionizing escape fractions of reionization-era galaxies

RAMSES-RTZ: Non-Equilibrium Metal Chemistry and Cooling Coupled to On-The-Fly Radiation Hydrodynamics

Stellar feedback in M 83 as observed with MUSE

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