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#reionization

1 post1 participant0 posts today
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Massimo Luciani

#astronomy #cosmology #JWST #galaxies #reionization

An article published in the journal "Nature" reports the results of observations of the primordial galaxy JADES-GS-z13-1. A team of researchers used the James Webb Space Telescope to examine this galaxy, estimating that it dates back to about 330 million years after the Big Bang. The surprise came from the so-called Lyman-alpha radiation because it was much stronger than expected from a galaxy of that era.

english.tachyonbeam.com/2025/0

english.tachyonbeam.comAn intense primordial light from the dark ages of the universeAn article published in the journal 'Nature' reports the results of observations of the primordial galaxy cataloged as JADES-GS-z13-1. A team of researchers...
Public
Louis Marmet 🇨🇦

#Cosmology #Reionization #CMB
"Reionization after JWST: a photon budget crisis?"
🔗arxiv.org/abs/2404.07250

"Our current galaxy observations, taken at face value, imply an excess of ionizing photons and thus a process of reionization in tension with the cosmic microwave background and Lyman-α forest."

Another component of the evolution after the Big Bang that is at tension with the Big Bang.

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arXiv.orgReionization after JWST: a photon budget crisis?New James Webb Space Telescope (JWST) observations are revealing the first galaxies to be prolific producers of ionizing photons, which we argue gives rise to a tension between different probes of reionization. For hydrogen reionization to proceed there must be enough ionizing photons for all of the hydrogen atoms, including their recombinations. Over the last two decades a consensus has emerged where star-forming galaxies are able to generate these photons, given reasonable values for their number densities, ionizing efficiencies $ξ_{\rm ion}$ (per unit UV luminosity), and escape fractions $f_{\rm esc}$. However, new JWST observations infer high values of $ξ_{\rm ion}$ during reionization and an enhanced abundance of earlier ($z\gtrsim 9$) galaxies, dramatically increasing the number of ionizing photons produced at high $z$. Simultaneously, recent low-$z$ studies predict significant escape fractions for faint reionization-era galaxies. Put together, we show that the galaxies we have directly observed ($M_{\rm UV} < -15$) not only can drive reionization, but would end it too early. That is, our current galaxy observations, taken at face value, imply an excess of ionizing photons and thus a process of reionization in tension with the cosmic microwave background (CMB) and Lyman-$α$ forest. Considering galaxies down to $M_{\rm UV}\approx -11$, below current observational limits, only worsens this tension, requiring on average $f_{\rm esc}\approx 3\%$, far lower than expected for early galaxies from post-reionization studies. We discuss possible avenues to resolve this photon budget crisis, including missing astrophysical or observational selection effects, as well as enhanced recombinations.
Public
Massimo Luciani

#astronomy #quasar #SMBH #reionization #CosmicDawn

An article published in the journal "The Astrophysical Journal Letters" reports the discovery of the most distant pair of merging quasars known. A team of researchers combined observations from the Subaru Telescope with the Gemini North Telescope to find traces of this pair of quasars that we see as they were about 900 million years after the Big Bang.

Read the details at english.tachyonbeam.com/2024/0

english.tachyonbeam.comFirst pair of merging quasars observed at Cosmic DawnAn article published in the journal 'The Astrophysical Journal Letters' reports the discovery of the most distant pair of merging quasars known. A team of...
Public
Daniel Pomarède

in the #arXiv

The First Billion Years, According to JWST

1.5 years into the JWST science mission, a snapshot of the great progress made towards understanding the initial chapters of our cosmic history.
by Angela Adamo and co-authors
arxiv.org/abs/2405.21054

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arXiv.orgThe First Billion Years, According to JWSTWith stunning clarity, JWST has revealed the Universe's first billion years. The scientific community is analyzing a wealth of JWST imaging and spectroscopic data from that era, and is in the process of rewriting the astronomy textbooks. Here, 1.5 years into the JWST science mission, we provide a snapshot of the great progress made towards understanding the initial chapters of our cosmic history. We highlight discoveries and breakthroughs, topics and issues that are not yet understood, and questions that will be addressed in the coming years, as JWST continues its revolutionary observations of the Early Universe. While this compendium is written by a small number of authors, invited to ISSI Bern in March 2024 as part of the 2024 ISSI Breakthrough Workshop, we acknowledge the work of a large community that is advancing our collective understanding of the evolution of the Early Universe.
#JWST#EarlyUniverse#Cosmology
Public
Daniel Fischer

Strong (Hb + [OIII]) and Ha emitters at redshift z≃7−8 unveiled with JWST/NIRCam and MIRI imaging in the Hubble eXtreme Deep Field (XDF): arxiv.org/abs/2301.10717 -> #MIRI instrument on #JWST detects H-alpha emission during the Epoch of #Reionization for the first time: astronomie.nl/nieuws/en/miri-i

arXiv.orgMIDIS: Strong (Hb + [OIII]) and Ha emitters at redshift $z \simeq 7-8$ unveiled with JWST/NIRCam and MIRI imaging in the Hubble eXtreme Deep Field (XDF)We make use of \textit{JWST} medium and broad-band NIRCam imaging, along with ultra-deep MIRI $5.6 \rm μm$ imaging, in the Hubble eXtreme Deep Field (XDF) to identify prominent line emitters at $z\simeq 7-8$. Out of a total of 58 galaxies at $z\simeq 7-8$, we find 18 robust candidates ($\simeq$31\%) for (H$β$ + [OIII]) emitters, based on their enhanced fluxes in the F430M and F444W filters, with EW$_{0}$(H$β$ +[OIII]) $\simeq 87 - 2100$ Å. Among these emitters, 16 lie in the MIRI coverage area and 12 exhibit a clear flux excess at $5.6 \, \rm μm$, indicating the simultaneous presence of a prominent H$α$ emission line with EW$_{0}$(H$α$) $\simeq 200-3000$ Å. This is the first time that H$α$ emission can be detected in individual galaxies at $z>7$. The H$α$ line, when present, allows us to separate the contributions of H$β$ and [OIII] to the (H$β$ +[OIII]) complex, and derive H$α$-based star formation rates (SFRs). We find that in most cases [OIII]/H$β> 1$. Instead, two galaxies have [OIII]/H$β< 1$, indicating that the NIRCam flux excess is mainly driven by H$β$. This could potentially imply extremely low metallicities. Most prominent line emitters are very young starbursts or galaxies on their way to/from the starburst cloud. They make for a cosmic SFR density $\rm log_{10}(ρ_{SFR_{Hα}}) \simeq -2.35$, which is about a quarter of the total value ($\rm log_{10}(ρ_{SFR_{tot}}) \simeq -1.76$) at $z\simeq 7-8$. Therefore, the strong H$α$ emitters likely had a significant role in reionization.
Public
Massimo Luciani

#astronomy #cosmology #stars #galaxies #reionization #JWST
An article published in the journal "Astronomy & Astrophysics" reports the identification of a group of primordial galaxies that could be among the ones that contributed to the reionization of the universe, making it go from dark to bright. A team of researchers used observations conducted with the James Webb space telescope within the GLASS-JWST program to study 29 very distant and therefore ancient galaxies.

english.tachyonbeam.com/2023/0

english.tachyonbeam.comSome of the galaxies that might have turned the universe from a dark place to a bright one have been identifiedAn article published in the journal 'Astronomy & Astrophysics' reports the identification of a group of primordial galaxies that could be among the ones that...
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