Cosmological reionization around the first stars: Monte Carlo radiative transfer

Ciardi, B.; Ferrara, Andrea; Marri, S.; Raimondo, Gabriella

doi:10.1046/j.1365-8711.2001.04316.x

Cited by 163 publications

(186 citation statements)

References 32 publications

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“…e.g. Ciardi et al 2001) will be useful to constrain f esc more precisely. -Due to the redward stellar evolution and short lifetimes of the most massive stars, the hardness of the ionising spectrum decreased rapidly, leading to the disappearance of the characteristic He ii recombination lines after ∼3 Myr in instantaneous bursts.…”

Section: Summary and Discussionmentioning

confidence: 99%

“…the proceedings of Weiss et al 2000;Umemura & Susa 2001). Among the questions addressed (see also the reviews of are the star formation process and the initial mass function (IMF) of the D. Schaerer: Population III stars and stellar populations 29 first stars (Tegmark et al 1997;Abel et al 1998Abel et al , 2000Bromm et al 1999;Nakamura & Umemura 1999Omukai & Palla 2001), their effect of energy injection and supernovae (SN) (MacLow & Ferrara 1999;Ciardi et al 2000), their role on cosmic reionisation (Haiman & Loeb 1997;Gnedin & Ostriker 1997;Tumlinson & Shull 2000;Cojazzi et al 2000;Ciardi et al 2001), metal enrichment of the IGM and other signatures of early chemical evolution Abia et al 2001), and dust formation (Todini & Ferrara 2000).…”

Section: Introductionmentioning

confidence: 99%

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On the properties of massive Population III stars and metal-free stellar populations

Schaerer

2002

A&A

855

1,283

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Abstract. We present realistic models for massive Population III stars and stellar populations based on non-LTE model atmospheres, recent stellar evolution tracks and up-to-date evolutionary synthesis models, with the aim to study their spectral properties, including their dependence on age, star formation history, and IMF. A comparison of plane parallel non-LTE model atmospheres and comoving frame calculations shows that even in the presence of some putative weak mass loss, the ionising spectra of metal-free populations differ little or negligibly from those obtained using plane parallel non-LTE models. As already discussed by Tumlinson & Shull (2000), the main salient property of Pop III stars is their increased ionising flux, especially in the He + continuum (>54 eV). The main result obtained for individual Pop III stars is the following: due to their redward evolution off the zero age main sequence (ZAMS) the spectral hardness measured by the He + /H ionising flux is decreased by a factor ∼2 when averaged over their lifetime. If such stars would suffer strong mass loss, their spectral appearance could, however, remain similar to that of their ZAMS position. The main results regarding integrated stellar populations are: -for young bursts and the case of a constant SFR, nebular continuous emission -neglected in previous studiesdominates the spectrum redward of Lyman-α if the escape fraction of ionising photons out of the considered region is small or negligible. In consequence predicted emission line equivalent widths are considerably smaller than found in earlier studies, whereas the detection of the continuum is eased. Nebular line and continuous emission strongly affect the broad band photometric properties of Pop III objects; -due to the redward stellar evolution and short lifetimes of the most massive stars, the hardness of the ionising spectrum decreases rapidly, leading to the disappearance of the characteristic He ii recombination lines after ∼3 Myr in instantaneous bursts; -He ii λ1640, Hα (and other) line luminosities usable as indicators of the star formation rate are given for the case of a constant SFR. For obvious reasons such indicators depend strongly on the IMF; -due to an increased photon production and reduced metal yields, the relative efficiency of ionising photon energy to heavy element rest mass production, η, of metal-poor and metal-free populations is increased by factors of ∼4 to 18 with respect to solar metallicity and for "standard" IMFs; -the lowest values of η ∼ 1.6-2.2% are obtained for IMFs exclusively populated with high mass stars (M low > ∼ 50 M ). If correct, the yields dominated by pair creation SNae then predict large overabundances of O/C and Si/C compared to solar abundance ratios. Detailed results are given in tabular form and as fit formulae for easy implementation in other calculations. The predicted spectra will be used to study the detectability of Pop III galaxies and to derive optimal search strategies for such objects.

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Section: Summary and Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

On the properties of massive Population III stars and metal-free stellar populations

Schaerer

2002

A&A

855

1,283

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“…The outputs of the hydro simulations described above are postprocessed with the Monte Carlo RT code CRASH (Ciardi et al 2001;Maselli et al 2003Maselli et al , 2009Graziani et al 2013;Graziani et al in prep), which, in its latest version, solves the cosmological ra-diative transfer of UV and soft X-ray photons 2 in a gas made of hydrogen and helium. We refer the reader to the original papers for more details on the code.…”

Section: Multi-frequency Radiative Transfer Simulationsmentioning

confidence: 99%

The concerted impact of galaxies and QSOs on the ionization and thermal state of the intergalactic medium

Kakiichi

Graziani

Ciardi

et al. 2017

Monthly Notices of the Royal Astronomical Society

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We present a detailed analysis of the ionization and thermal structure of the intergalactic medium (IGM) around a high-redshift QSO using a large suite of cosmological, multifrequency radiative transfer (RT) simulations, exploring the contribution from galaxies as well as the QSO, and the effect of X-rays and secondary ionization. We show that in high-z QSO environments both the central QSO and the surrounding galaxies concertedly control the reionization morphology of hydrogen and helium and have a non-linear impact on the thermal structure of the IGM. A QSO imprints a distinctive morphology on H II regions if its total ionizing photon budget exceeds that of the surrounding galaxies since the onset of hydrogen reionization; otherwise, the morphology shows little difference from that of H II regions produced only by galaxies. In addition, the spectral shape of the collective radiation field from galaxies and QSOs controls the thickness of the I-fronts. While a UV-obscured QSO can broaden the I-front, the contribution from other UV sources, either galaxies or unobscured QSO, is sufficient to maintain a sharp I-front. X-rays photons from the QSO are responsible for a prominent extended tail of partial ionization ahead of the I-front. QSOs leave a unique imprint on the morphology of He II/He III regions. We suggest that, while the physical state of the IGM is modified by QSOs, the most direct test to understand the role of galaxies and QSOs during reionization is to perform galaxy surveys in a region of sky imaged by 21 cm tomography.

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“…The 2003 Wilkinson Microwave Anisotropy Probe (WMAP) discovery of large optical depths to electron scattering at z $ 15 ( Kogut et al 2003;Spergel et al 2003) motivated several numerical and analytical studies of early reionization (Haiman & Holder 2003;Cen 2003;Somerville & Livio 2003;Barkana & Loeb 2004;Sokasian et al 2003Sokasian et al , 2004Ciardi et al 2003Ciardi et al , 2001Wyithe & Loeb 2003). The goal of these models was to extend the classical picture of reionization to account for the large electron fractions at high redshifts while still accommodating lower redshift observations.…”

Section: Early Reionizationmentioning

confidence: 99%

Untitled

2006

ASTROPHYS J SUPPL S

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Radiation hydrodynamical transport of ionization fronts ( I-fronts) in the next generation of cosmological reionization simulations holds the promise of predicting UV escape fractions from first principles as well as investigating the role of photoionization in feedback processes and structure formation. We present a multistep integration scheme for radiative transfer and hydrodynamics for accurate propagation of I-fronts and ionized flows from a point source in cosmological simulations. The algorithm is a photon-conserving method that correctly tracks the position of I-fronts at much lower resolutions than nonconservative techniques. The method applies direct hierarchical updates to the ionic species, bypassing the need for the costly matrix solutions required by implicit methods while retaining sufficient accuracy to capture the true evolution of the fronts. We review the physics of ionization fronts in power-law density gradients, whose analytical solutions provide excellent validation tests for radiation coupling schemes. The advantages and potential drawbacks of direct and implicit schemes are also considered, with particular focus on problem time-stepping, which if not properly implemented can lead to morphologically plausible I-front behavior that nonetheless departs from theory. We also examine the effect of radiation pressure from very luminous central sources on the evolution of I-fronts and flows.

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Cosmological reionization around the first stars: Monte Carlo radiative transfer

Cited by 163 publications

References 32 publications

On the properties of massive Population III stars and metal-free stellar populations

On the properties of massive Population III stars and metal-free stellar populations

The concerted impact of galaxies and QSOs on the ionization and thermal state of the intergalactic medium

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