Formaldehyde absorption toward W51

Kogut, A.; Smoot, George F.; Bennett, C. L.; Petuchowski, S. J.

doi:10.1086/168057

Cited by 35 publications

(71 citation statements)

References 4 publications

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“…In Fig. 13 we compare the evolution of the H ii volume‐weight ionization fractions (top panel) and the resultant evolution of the optical depth to electron scattering τ e (bottom panel) for three different cases for this form: (1) k = 0 (solid line), which represents our fiducial model with zero boosting; (2) k = 0.13 (dotted line), which represents the scenario where the combination of f esc = 0.20 and the boosting factor may be thought of in terms of an escape fraction which evolves from 0.20 at z = 6 (necessary to provide a consistent match with the Becker et al 2001 observations) to unity at z = 18 around when the first star‐forming sources turn on; and (3) k = 0.33 (dashed line), which is meant to serve as an illustrative example of the additional ionizing boost necessary at high redshifts in order to match the electron optical depth measurement implied by the Kogut et al (2003)‘model independent’ analysis. The electron optical depth was calculated using where σ T = 6.65 × 10 −25 cm 2 is the Thomson cross‐section and n e ( z ′) is the mean electron number density at z ′.…”

Section: Resultsmentioning

confidence: 67%

“…The uncertainty associated with this measurement depends on fitting all parameters concerned with the TT power spectrum and the TE cross‐power spectrum. Kogut et al (2003) obtain a 68 per cent confidence range of 0.13 < τ e < 0.21 corresponding to an instantaneous reionization epoch which occurred for 14 < z < 20. None of the models we have considered in this paper is able reionize the Universe by such early redshifts.…”

Section: Resultsmentioning

confidence: 77%

“…The recent tentative measurement of polarization in the CMB by the WMAP satellite (Kogut et al 2003) suggests that reionization occurred in a more complex manner than indicated by the SDSS quasars alone (e.g. Spergel et al 2003).…”

Section: Resultsmentioning

confidence: 99%

“…In particular, we do not account for massive, Population III stars that may have been prevalent at z ≳ 20. Tentative measurements of polarization in the cosmic microwave background (CMB) by the WMAP satellite (Kogut et al 2003) suggest that much of the IGM was ionized earlier than indicated by the SDSS quasars (e.g. Spergel et al 2003).…”

Section: Introductionmentioning

confidence: 99%

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Cosmic reionization by stellar sources: Population II stars

Sokasian

Abel

Hernquist

et al. 2003

Monthly Notices RAS

169

252

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We study the reionization of the Universe by stellar sources using a numerical approach that combines fast 3D radiative transfer calculations with high‐resolution hydrodynamical simulations. By supplementing a one‐step radiative transfer code specifically designed for following ionization processes with an adaptive ray‐tracing algorithm, we are able to speed up the calculations significantly to the point where handling a vast number of sources becomes technically feasible. This allows us to study how dim low‐mass sources, excluded in previous investigations owing to computational limitations, affect the morphological evolution of the reionization process. Ionizing fluxes for the sources are derived from intrinsic star formation rates computed in the underlying hydrodynamical simulations. Analysis of numerically converged results for star formation rates and halo mass functions allows us to assess the consequences of not including low‐mass objects and enables us to correct for resolution effects. With these corrections, we are able to reduce the effective mass resolution limit for sources to M∼ 4.0 × 107h−1 M⊙ in a 10 h−1 Mpc comoving box. Our calculations reveal that the process by which ionized regions in the intergalactic medium (IGM) percolate is complex and is especially sensitive to the inclusion of dim sources. Moreover, we find that, given the same level of cosmic star formation, the number of ionizing photons required to reionize the Universe is significantly overestimated if sources with masses below ∼109h−1 M⊙ are excluded. This result stems from the fact that low‐mass sources preferentially reside in less clumpy environments than their massive counterparts. Consequently, their exclusion has the net effect of concentrating more of the cosmic ionizing radiation in regions which have higher recombination rates. We present the results of our reionization simulation assuming a range of escape fractions for ionizing photons and make statistical comparisons with observational constraints on the neutral fraction of hydrogen at z∼ 6 derived from the z= 6.28 Sloan Digital Sky Survey (SDSS) quasar of Becker and coworkers. We find that, given the amplitude and form of the underlying star formation predictions, an escape fraction near fesc= 0.10–0.20 is most consistent with the observational results. In these models, reionization is expected to have occurred between z∼ 7–8, although the IGM remains fairly opaque until z≃ 6. Our method is also capable of handling the simultaneous reionization of the helium component in the IGM, allowing us to explore the plausibility of the scenario where sources with harder spectra are primarily responsible for reionization. In this case, we find that if the sources responsible for reionizing hydrogen by z∼ 8 had spectra similar to active galactic nuclei, then the helium component of the IGM should have been reionized by z∼ 6. We find that such an early reionization epoch for helium does not necessarily conflict with observational constraints obtained at z≃ 3, but may be c...

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Section: Resultsmentioning

confidence: 67%

Section: Resultsmentioning

confidence: 77%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Cosmic reionization by stellar sources: Population II stars

Sokasian

Abel

Hernquist

et al. 2003

Monthly Notices RAS

169

252

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“…The relatively bright rest‐frame ultraviolet continuum flux and Lyman α line luminosity of SBM03#3 and the recent WMAP results which indicate the epoch of reionization to lie at z > 10 (Kogut et al 2003) bode well for searches for ultraviolet‐luminous star‐forming galaxies at z > 7, such as those that will be possible using the narrow‐band near‐infrared imaging system DAZLE (the Dark Ages ‘Z’ Lyman Explorer: McMahon et al, in preparation), HST /WFC3 and James Webb Space Telescope.…”

Section: Discussionmentioning

confidence: 68%

A star-forming galaxy atz= 5.78 in theChandraDeep Field South

Bunker¹,

Stanway²,

Ellis³

et al. 2003

Monthly Notices of the Royal Astronomical Society

103

115

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We report the discovery of a luminous z= 5.78 star‐forming galaxy in the Chandra Deep Field South. This galaxy was selected as an ‘i‐drop’ from the GOODS public survey imaging with the Hubble Space Telescope/Advanced Camera for Surveys (object 3 in the work of Stanway, Bunker & McMahon 2003). The large colour of (i′−z′)AB= 1.6 indicated a spectral break consistent with the Lyman α forest absorption shortward of Lyman α at z≈ 6. The galaxy is very compact (marginally resolved with ACS with a half‐light radius of 0.08 arcsec, so rhl < 0.5 h−170 kpc). We have obtained a deep (5.5 h) spectrum of this z′AB= 24.7 galaxy with the DEIMOS optical spectrograph on the Keck Telescope, and here we report the discovery of a single emission line centred on 8245 Å detected at 20σ with a flux of f≈ 2 × 10−17 erg cm−2 s−1. The line is clearly resolved with detectable structure at our resolution of better than 55 km s−1, and the only plausible interpretation consistent with the ACS photometry is that we are seeing Lyman α emission from a z= 5.78 galaxy. This is the highest redshift galaxy to be discovered and studied using HST data. The velocity width (ΔvFWHM= 260 km s−1) and rest‐frame equivalent width (WLyαrest= 20 Å) indicate that this line is most probably powered by star formation, as an AGN would typically have larger values. The starburst interpretation is supported by our non‐detection of the high‐ionization N vλ1240‐ Å emission line, and the absence of this source from the deep Chandra X‐ray images. The star formation rate inferred from the rest‐frame UV continuum is 34 h−270 M⊙ yr−1 (ΩM= 0.3, ΩΛ= 0.7). This is the most luminous starburst known at z > 5. Our spectroscopic redshift for this object confirms the validity of the i′‐drop technique of Stanway et al. to select star‐forming galaxies atz≈ 6.

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The Dawn of Galaxies

Madau

2009

The Impact of HST on European Astronomy

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The development of primordial inhomogeneities into the non-linear regime and the formation of the first astrophysical objects within dark matter halos mark the transition from a simple, neutral, cooling universe -described by just a few parameters -to a messy ionized one -the realm of radiative, hydrodynamic, and star formation processes. The recent measurement by the WMAP satellite of a large optical depth to electron scattering implies that this transition must have begun very early, and that the universe was reionized at redshift z ion = 17 ± 5. It is an early generation of extremely metal-poor massive stars and/or 'seed' accreting black holes in subgalactic halos that may have generated the ultraviolet radiation and mechanical energy that reheated and reionized most of the hydrogen in the cosmos. The detailed thermal, ionization, and chemical enrichment history of the universe during the crucial formative stages around z = 10 − 20 depends on the power-spectrum of density fluctuations on small scales, the stellar initial mass function and star formation efficiency, a complex network of poorly understood 'feedback' mechanisms, and remains one of the crucial missing links in galaxy formation and evolution studies. *

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Formaldehyde absorption toward W51

Cited by 35 publications

References 4 publications

Cosmic reionization by stellar sources: Population II stars

Cosmic reionization by stellar sources: Population II stars

A star-forming galaxy atz= 5.78 in theChandraDeep Field South

The Dawn of Galaxies

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