102 research outputs found
Constraints on reionisation from the z=7.5 QSO ULASJ1342+0928
The recent detection of ULASJ1342+0928, a bright QSO at , provides a
powerful probe of the ionisation state of the intervening intergalactic medium,
potentially allowing us to set strong constraints on the epoch of reionisation
(EoR). Here we quantify the presence of Ly damping wing absorption from
the EoR in the spectrum of ULASJ1342+0928. Our Bayesian framework
simultaneously accounts for uncertainties on: (i) the intrinsic QSO emission
(obtained from reconstructing the Ly profile from a covariance matrix
of emission lines) and (ii) the distribution of HII regions during reionisation
(obtained from three different 1.6 Gpc simulations spanning the range
of plausible EoR morphologies). Our analysis is complementary to that in the
discovery paper (Ba\~nados et al.) and the accompanying method paper (Davies et
al.) as it focuses solely on the damping wing imprint redward of Ly
(\AA), and uses a different methodology for (i) and
(ii). We recover weak evidence for damping wing absorption. Our intermediate
EoR model yields a volume-weighted neutral hydrogen fraction at of
(68 per cent). The
constraints depend weakly on the EoR morphology. Our limits are lower than
those presented previously, though they are consistent at ~1-1.5. We
attribute this difference to: (i) a lower amplitude intrinsic Ly
profile obtained from our reconstruction pipeline, driven by correlations with
other high-ionisation lines in the spectrum which are relatively weak; and (ii)
only considering transmission redward of Ly when computing the
likelihood, which reduces the available constraining power but makes the
results less model-dependent. Our results are consistent with previous
estimates of the EoR history, and support the picture of a moderately extended
EoR.Comment: 7 pages, 3 figures. Submitted to MNRAS, comments welcom
The galaxy environment of a QSO at z ~ 5.7
High-redshift quasars are believed to reside in massive halos in the early
universe and should therefore be located in fields with overdensities of
galaxies, which are thought to evolve into galaxy clusters seen in the local
universe. However, despite many efforts, the relationship between galaxy
overdensities and z~6 quasars is ambiguous. This can possibly be attributed to
the difficulty of finding galaxies with accurate redshifts in the vicinity of
z~6 quasars. So far, overdensity searches around z~6 quasars have been based on
studies of Lyman break galaxies (LBGs), which probe a redshift range of Delta z
~ 1. This range is large enough to select galaxies that may not be physically
related to the quasar. We use deep narrow- and broadband imaging to study the
environment of the z=5.72 quasar ULAS J0203+0012. The redshift range probed by
our narrow-band selection of Lyman alpha emitters (LAEs) is Delta z ~ 0.1,
which is significantly narrower than the LBG searches. This is the first time
that LAEs were searched for near a z~6 quasar, in an effort to provide clues
about the environments of quasars at the end of the epoch of reionization. We
find no enhancement of LAEs in the surroundings of ULAS J0203+0012 in
comparison with blank fields. We explore different explanations and
interpretations for this non-detection of a galaxy overdensity, including that
(1) the strong ionization from the quasar may prevent galaxy formation in its
immediate vicinity and (2) high-redshift quasars may not reside in the center
of the most massive dark matter halos.Comment: text updated to match published versio
On eleven-dimensional Supergravity and Chern-Simons theory
We probe in some depth into the structure of eleven-dimensional,
osp(32|1)-based Chern-Simons supergravity, as put forward by Troncoso and
Zanelli (TZ) in 1997. We find that the TZ Lagrangian may be cast as a
polynomial in 1/l, where l is a length, and compute explicitly the first three
dominant terms. The term proportional to 1/l^9 turns out to be essentially the
Lagrangian of the standard 1978 supergravity theory of Cremmer, Julia and
Scherk, thus establishing a previously unknown relation between the two
theories. The computation is nontrivial because, when written in a sufficiently
explicit way, the TZ Lagrangian has roughly one thousand non-explicitly
Lorentz-covariant terms. Specially designed algebraic techniques are used to
accomplish the results.Comment: v1: 16 pages, no figures. v2: updated references and minor
corrections. v3: 10 pages, no figures. Paper fully rewritten; results and
conclusions unchanged. v4: 13 pages, no figures. Some minor changes and
improved bibliography. Version accepted for publication in NP
Uncovering the First AGN Jets with AXIS
Jets powered by AGN in the early Universe () have the potential
to not only define the trajectories of the first-forming massive galaxies but
to enable the accelerated growth of their associated SMBHs. Under typical
assumptions, jets could even rectify observed quasars with light seed formation
scenarios; however, not only are constraints on the parameters of the first
jets lacking, observations of these objects are scarce. Owing to the
significant energy density of the CMB at these epochs capable of quenching
radio emission, observations will require powerful, high angular resolution
X-ray imaging to map and characterize these jets. As such, \textit{AXIS} will
be necessary to understand early SMBH growth and feedback.Comment: 7 Pages, 2 Figures. This White Paper is part of a series commissioned
for the AXIS Probe Concept Mission; additional AXIS White Papers can be found
at the AXIS website (http://axis.astro.umd.edu/) with a mission overview
here: arXiv:2311.0078
Exploring Reionization-Era Quasars IV: Discovery of Six New Quasars with DES, VHS and unWISE Photometry
This is the fourth paper in a series of publications aiming at discovering
quasars at the epoch of reionization. In this paper, we expand our search for
quasars to the footprint of the Dark Energy Survey (DES) Data Release
One (DR1), covering deg of new area. We select quasar
candidates using deep optical, near-infrared (near-IR) and mid-IR photometric
data from the DES DR1, the VISTA Hemisphere Survey (VHS), the VISTA Kilo-degree
Infrared Galaxy (VIKING) survey, the UKIRT InfraRed Deep Sky Surveys -- Large
Area Survey (ULAS) and the unblurred coadds from the Wide-field Infrared Survey
Explore () images (unWISE). The inclusion of DES and unWISE photometry
allows the search to reach 1 magnitude fainter, comparing to our quasar survey in the northern sky (Wang et al. 2018). We report
the initial discovery and spectroscopic confirmation of six new luminous
quasars at , including an object at , the fourth quasar yet
known at , from a small fraction of candidates observed thus far. Based on
the recent measurement of quasar luminosity function using the
quasar sample from our survey in the northern sky, we estimate that there will
be 55 quasars at at in the full DES
footprint.Comment: 8 pages, 3 figures, submitted to A
Possible Contamination of the Intergalactic Medium Damping Wing in ULAS J1342+0928 by Proximate Damped Ly Absorption
The red damping wing from neutral hydrogen in the intergalactic medium is a
smoking-gun signal of ongoing reionization. One potential contaminant of the
intergalactic damping wing signal is dense gas associated with foreground
galaxies, which can give rise to proximate damped Ly absorbers. The
Ly imprint of such absorbers on background quasars is indistinguishable
from the intergalactic medium within the uncertainty of the intrinsic quasar
continuum, and their abundance at is unknown. Here we show that the
complex of low-ionization metal absorption systems recently discovered by deep
JWST/NIRSpec observations in the foreground of the quasar
ULAS~J13420928 can potentially reproduce the quasar's spectral profile close
to rest-frame Ly without invoking a substantial contribution from the
intergalactic medium, but only if the absorbing gas is extremely metal-poor
(). Such a low oxygen abundance has never been
observed in a damped Ly absorber at any redshift, but this possibility
still complicates the interpretation of the spectrum. Our analysis highlights
the need for deep spectroscopy of high-redshift quasars with JWST or ELT to
"purify" damping wing quasar samples, an exercise which is impossible for much
fainter objects like galaxies.Comment: 10 pages, 5 figures, submitted to ApJ
Mapping the Lyman-Alpha Emission Around a z~6.6 QSO with MUSE: Extended Emission and a Companion at Close Separation
We utilize the Multi Unit Spectroscopic Explorer (MUSE) on the Very Large
Telescope (VLT) to search for extended Lyman-Alpha emission around the z~6.6
QSO J0305-3150. After carefully subtracting the point-spread-function, we reach
a nominal 5-sigma surface brightness limit of SB = 1.9x10
erg/s/cm/arcsec over a 1 arcsec aperture, collapsing 5 wavelength
slices centered at the expected location of the redshifted Lyman-Alpha emission
(i.e. at 9256 Ang.). Current data suggest the presence (5-sigma, accounting for
systematics) of a Lyman-Alpha nebula that extends for 9 kpc around the QSO.
This emission is displaced and redshifted by 155 km/s with respect to the
location of the QSO host galaxy traced by the [CII] emission line. The total
luminosity is L = 3.0x10 erg/s. Our analysis suggests that this emission
is unlikely to rise from optically thick clouds illuminated by the ionizing
radiation of the QSO. It is more plausible that the Lyman-Alpha emission is due
to fluorescence of the highly ionized optically thin gas. This scenario implies
a high hydrogen volume density of n ~ 6 cm. In addition, we detect a
Lyman-Alpha emitter (LAE) in the immediate vicinity of the QSO: i.e., with a
projected separation of 12.5 kpc and a line-of-sight velocity difference of 560
km/s. The luminosity of the LAE is L = 2.1x10 erg/s and its inferred
star-formation-rate is SFR ~ 1.3 M/yr. The probability of finding such
a close LAE is one order of magnitude above the expectations based on the
QSO-galaxy cross-correlation function. This discovery is in agreement with a
scenario where dissipative interactions favour the rapid build-up of
super-massive black holes at early Cosmic times.Comment: 17 pages, 15 figures. Accepted for publication in Ap
Mapping the Lyman-Alpha Emission Around a z~6.6 QSO with MUSE: Extended Emission and a Companion at Close Separation
We utilize the Multi Unit Spectroscopic Explorer (MUSE) on the Very Large
Telescope (VLT) to search for extended Lyman-Alpha emission around the z~6.6
QSO J0305-3150. After carefully subtracting the point-spread-function, we reach
a nominal 5-sigma surface brightness limit of SB = 1.9x10
erg/s/cm/arcsec over a 1 arcsec aperture, collapsing 5 wavelength
slices centered at the expected location of the redshifted Lyman-Alpha emission
(i.e. at 9256 Ang.). Current data suggest the presence (5-sigma, accounting for
systematics) of a Lyman-Alpha nebula that extends for 9 kpc around the QSO.
This emission is displaced and redshifted by 155 km/s with respect to the
location of the QSO host galaxy traced by the [CII] emission line. The total
luminosity is L = 3.0x10 erg/s. Our analysis suggests that this emission
is unlikely to rise from optically thick clouds illuminated by the ionizing
radiation of the QSO. It is more plausible that the Lyman-Alpha emission is due
to fluorescence of the highly ionized optically thin gas. This scenario implies
a high hydrogen volume density of n ~ 6 cm. In addition, we detect a
Lyman-Alpha emitter (LAE) in the immediate vicinity of the QSO: i.e., with a
projected separation of 12.5 kpc and a line-of-sight velocity difference of 560
km/s. The luminosity of the LAE is L = 2.1x10 erg/s and its inferred
star-formation-rate is SFR ~ 1.3 M/yr. The probability of finding such
a close LAE is one order of magnitude above the expectations based on the
QSO-galaxy cross-correlation function. This discovery is in agreement with a
scenario where dissipative interactions favour the rapid build-up of
super-massive black holes at early Cosmic times.Comment: 17 pages, 15 figures. Accepted for publication in Ap
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