849 research outputs found
The Role of Galaxies and Quasars in Reionising the High Redshift Intergalactic Medium
Only one billion years after the Big Bang, the neutral hydrogen in the intergalactic medium had been completely ionised. This last phase transition of the Universe known as the epoch of reionisation is one of the frontiers in astrophysics. Despite our growing knowledge on the timing and topology of cosmic reionisation, the sources responsible for emitting the necessary ionising photons have remained elusive. Specifically, the escape fraction of ionising photons in reionisation-era galaxies and the role of quasars remain open and debated questions. This Thesis aims to answer these questions in order to understand the nature of the sources of reionisation. Firstly, I present the discovery of a luminous galaxy whose double-peak Lyman-α emission profile indicates an escape fraction close to 100%. I show how this galaxy is the first evidence of an object self-ionising its own H II bubble deep into the reionisation era. Secondly, I measure the cross-correlation of z ∼ 5-6 galaxies and metal absorbers with the IGM opacity to Lyman-α probed by high-redshift quasars. I extend the analytical model of the galaxy-IGM cross-correlation to derive average escape fractions for faint galaxies in the reionisation era. Thirdly, I investigate the evolution of quasars with redshift by measuring the relative offsets of broad emission lines in four hundred quasars at 1 < z < 7. I discuss how quasar evolution and selection biases can explain the increased blueshift of the triplyionised carbon (C IV) quasar broad emission line in the first billion years. I then present the first results of a programme to detect missing lensed z ∼ 6 quasars. Finally, this Thesis concludes on the combination of the different results into a coherent picture of the nature of the sources of reionisation and prospects for future instruments and surveys
Covariant Affine Integral Quantization(s)
Covariant affine integral quantization of the half-plane is studied and
applied to the motion of a particle on the half-line. We examine the
consequences of different quantizer operators built from weight functions on
the half-plane. To illustrate the procedure, we examine two particular choices
of the weight function, yielding thermal density operators and affine inversion
respectively. The former gives rise to a temperature-dependent probability
distribution on the half-plane whereas the later yields the usual canonical
quantization and a quasi-probability distribution (affine Wigner function)
which is real, marginal in both momentum p and position q.Comment: 36 pages, 10 figure
ALMA 400 pc Imaging of a z = 6.5 Massive Warped Disk Galaxy
© 2023. The Author(s). Published by the American Astronomical Society. This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY), https://creativecommons.org/licenses/by/4.0/We present 0.″075 (≈400 pc) resolution Atacama Large Millimeter/submillimeter Array (ALMA) observations of the [C ii] and dust continuum emission from the host galaxy of the z = 6.5406 quasar, P036+03. We find that the emission arises from a thin, rotating disk with an effective radius of 0.″21 (1.1 kpc). The velocity dispersion of the disk is consistent with a constant value of 66.4 ± 1.0 km s−1, yielding a scale height of 80 ± 30 pc. The [C ii] velocity field reveals a distortion that we attribute to a warp in the disk. Modeling this warped disk yields an inclination estimate of 40.°4 ± 1.°3 and a rotational velocity of 116 ± 3 km s−1. The resulting dynamical mass estimate of (1.96 ± 0.10) × 1010 M ⊙ is lower than previous estimates, which strengthens the conclusion that the host galaxy is less massive than expected based on local scaling relations between the black hole mass and the host galaxy mass. Using archival MUSE Lyα observations, we argue that counterrotating halo gas could provide the torque needed to warp the disk. We further detect a region with excess (15σ) dust continuum emission, which is located 1.3 kpc northwest of the galaxy’s center and is gravitationally unstable (Toomre Q < 0.04). We posit this is a star-forming region whose formation was triggered by the warp because the region is located within a part of the warped disk where gas can efficiently lose angular momentum. The combined ALMA and MUSE imaging provides a unique view of how gas interactions within the disk–halo interface can influence the growth of massive galaxies within the first billion years of the Universe.Peer reviewe
Photometric IGM tomography with Subaru/HSC: the large-scale structure of Lyα emitters and IGM transmission in the COSMOS field at z ∼ 5
We present a novel technique called “photometric IGM tomography” to map the intergalactic medium (IGM) at z ≃ 4.9 in the COSMOS field. It utilizes deep narrow-band (NB) imaging to photometrically detect faint Lyα forest transmission in background galaxies across the Subaru/Hyper-Suprime Cam (HSC)’s 1.8sq.deg
field of view and locate Lyα emitters (LAEs) in the same cosmic volume. Using ultra-deep HSC images and Bayesian spectral energy distribution fitting, we measure the Lyα forest transmission at z ≃ 4.9 along a large number (140) of background galaxies selected from the DEIMOS10k spectroscopic catalogue at 4.98 < z < 5.89 and the SILVERRUSH LAEs at z ≃ 5.7. We photometrically measure the mean Lyα forest transmission and achieve a result consistent with previous measurements based on quasar spectra. We also measure the angular LAE-Lyα forest cross-correlation and Lyα forest auto-correlation functions and place an observational constraint on the large-scale fluctuations of the IGM around LAEs at z ≃ 4.9. Finally, we present the reconstructed 2D tomographic map of the IGM, co-spatial with the large-scale structure of LAEs, at a transverse resolution of 11h−1cMpc
across 140h−1cMpc
in the COSMOS field at z ≃ 4.9. We discuss the observational requirements and the potential applications of this new technique for understanding the sources of reionization, quasar radiative history, and galaxy-IGM correlations across z ∼ 3 − 6. Our results represent the first proof-of-concept of photometric IGM tomography, offering a new route to examining early galaxy evolution in the context of the large-scale cosmic web from the epoch of reionization to cosmic noon
The XQR-30 Metal Absorber Catalog: 778 Absorption Systems Spanning 2 < z < 6.5
Intervening metal absorption lines in the spectra of z > 6 quasars are
fundamental probes of the ionization state and chemical composition of
circumgalactic and intergalactic gas near the end of the reionization epoch.
Large absorber samples are required to robustly measure typical absorber
properties and to refine models of the synthesis, transport, and ionization of
metals in the early Universe. The "Ultimate XSHOOTER legacy survey of quasars
at z~5.8-6.6" (XQR-30) has obtained high signal-to-noise spectra of 30 luminous
quasars, nearly quadrupling the existing sample of 12 high quality z~6 quasar
spectra. We use this unprecedented sample to construct a catalog of 778 systems
showing absorption in one or more of MgII (360 systems), FeII (184), CII (46),
CIV (479), SiIV (127), and NV (13) which span 2 < z < 6.5. This catalog
significantly expands on existing samples of z > 5 absorbers, especially for
CIV and SiIV which are important probes of the ionizing photon background at
high redshift. The sample is 50% (90%) complete for rest-frame equivalent
widths W > 0.03AA (0.09AA). We publicly release the absorber catalog along with
completeness statistics and a Python script to compute the absorption search
path for different ions and redshift ranges. This dataset is a key legacy
resource for studies of enriched gas from the era of galaxy assembly to cosmic
noon, and paves the way for even higher redshift studies with the James Webb
Space Telescope and 30m-class telescopes.Comment: 29 pages and 14 figures including 2 appendices. Accepted for
publication in MNRAS. The metal absorber catalogue can be downloaded from
https://github.com/XQR-30/Metal-catalogue. Contents unchanged from v1 apart
from change to author lis
Little Red Dots: an abundant population of faint AGN at revealed by the EIGER and FRESCO JWST surveys
Characterising the prevalence and properties of faint active galactic nuclei
(AGN) in the early Universe is key for understanding the formation of
supermassive black holes (SMBHs) and determining their role in cosmic
reionization. We perform a spectroscopic search for broad H emitters at
using deep JWST/NIRCam imaging and wide field slitless
spectroscopy from the EIGER and FRESCO surveys. We identify 20 H lines
at that have broad components with line widths from km s, contributing % of the total line flux. We
interpret these broad components as being powered by accretion onto SMBHs with
implied masses M. In the UV luminosity range M = -21 to -18, we measure number densities of cMpc.
This is an order of magnitude higher than expected from extrapolating quasar UV
luminosity functions. Yet, such AGN are found in only % of star-forming
galaxies at . The SMBH mass function agrees with large cosmological
simulations. In two objects we detect narrow red- and blue-shifted H
absorption indicative, respectively, of dense gas fueling SMBH growth and
outflows. We may be witnessing early AGN feedback that will clear dust-free
pathways through which more massive blue quasars are seen. We uncover a strong
correlation between reddening and the fraction of total galaxy luminosity
arising from faint AGN. This implies that early SMBH growth is highly obscured
and that faint AGN are only minor contributors to cosmic reionization.Comment: 23 pages, 17 figures. Submitted to ApJ. Main Figs 4, 10, 15 (faint
AGN UV luminosity function) and 16 (SMBH mass function). Fig. 17 summarises
the results. Comments welcom
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