94 research outputs found
A powerful radio-loud quasar at the end of cosmic reionization
We present the discovery of the radio-loud quasar PSO J352.4034-15.3373 at
z=5.84 pm 0.02. This quasar is the radio brightest source known, by an order of
magnitude, at z~6 with a flux density in the range of 8-100 mJy from 3GHz to
230MHz and a radio loudness parameter R>~1000. This source provides an
unprecedented opportunity to study powerful jets and radio-mode feedback at the
highest redshifts, and presents the first real chance to probe deep into the
neutral intergalactic medium by detecting 21 cm absorption at the end of cosmic
reionization.Comment: ApJL accepted on May 8, 2018. See the companion paper by Momjian et
a
Circum-galactic medium in the halo of quasars
The properties of circum-galactic gas in the halo of quasar host galaxies are
investigated analyzing Mg II 2800 and C IV 1540 absorption-line systems along
the line of sight close to quasars. We used optical spectroscopy of closely
aligned pairs of quasars (projected distance 200 kpc, but at very
different redshift) obtained at the VLT and Gran Telescopio Canarias to
investigate the distribution of the absorbing gas for a sample of quasars at
z1. Absorption systems of EW 0.3 associated with the
foreground quasars are revealed up to 200 kpc from the centre of the host
galaxy, showing that the structure of the absorbing gas is patchy with a
covering fraction quickly decreasing beyond 100 kpc. In this contribution we
use optical and near-IR images obtained at VLT to investigate the relations
between the properties of the circum-galactic medium of the host galaxies and
of the large scale galaxy environments of the foreground quasars.Comment: 6 pages, 3 figures, proceedings of the conference "QUASARS at all
cosmic epochs", accepted for publication on Frontiers in Astronomy and Space
Scienc
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
A metal-poor damped Ly-alpha system at redshift 6.4
We identify a strong Ly-alpha damping wing profile in the spectrum of the
quasar P183+05 at z=6.4386. Given the detection of several narrow metal
absorption lines at z=6.40392, the most likely explanation for the absorption
profile is that it is due to a damped Ly-alpha system. However, in order to
match the data a contribution of an intergalactic medium 5-38% neutral or
additional weaker absorbers near the quasar is also required. The absorption
system presented here is the most distant damped Ly-alpha system currently
known. We estimate an HI column density (cm),
metallicity ([O/H]), and relative chemical abundances of a
system consistent with a low-mass galaxy during the first Gyr of the universe.
This object is among the most metal-poor damped Ly-alpha systems known and,
even though it is observed only ~850 Myr after the big bang, its relative
abundances do not show signatures of chemical enrichment by Population III
stars.Comment: Updated to match published versio
The Decoupled Kinematics of High- z QSO Host Galaxies and Their Ly α Halos
© 2022. The Author(s). Published by the American Astronomical Society. This is an open access article distributed under the Creative Commons Attribution License, to view a copy of the license, see: https://creativecommons.org/licenses/by/4.0/We present a comparison of the interstellar medium traced by [C ii] (Atacama Large Millimeter/submillimeter Array), and ionized halo gas traced by Lyα (Multi Unit Spectroscopic Explorer), in and around QSO host galaxies at z ∼ 6. To date, 18 QSOs at this redshift have been studied with both MUSE and high-resolution ALMA imaging; of these, 8 objects display a Lyα halo. Using data cubes matched in velocity resolution, we compare and contrast the spatial and kinematic information of the Lyα halos and the host galaxies’ [C ii] (and dust-continuum) emission. We find that the Lyα halos extend typically 3−30 times beyond the interstellar medium of the host galaxies. The majority of the Lyα halos do not show ordered motion in their velocity fields, whereas most of the [C ii] velocity fields do. In those cases where a velocity gradient can be measured in Lyα, the kinematics do not align with those derived from the [C ii] emission. This implies that the Lyα emission is not tracing the outskirts of a large rotating disk, which is a simple extension of the central galaxy seen in [C ii] emission. It rather suggests that the kinematics of the halo gas are decoupled from those of the central galaxy. Given the scattering nature of Lyα, these results need to be confirmed with James Webb Space Telescope Integral Field Unit observations that can constrain the halo kinematics further using the nonresonant Hα line.Peer reviewe
Enhanced X-ray Emission from the Most Radio-Powerful Quasar in the Universe's First Billion Years
We present deep (265 ks) Chandra X-ray observations of PSO
J352.403415.3373, a quasar at z=5.831 that, with a radio-to-optical flux
ratio of R>1000, is one of the radio-loudest quasars in the early universe and
is the only quasar with observed extended radio jets of kpc-scale at . Modeling the X-ray spectrum of the quasar with a power law, we find a best
fit of , leading to an X-ray luminosity of
and
an X-ray to UV brightness ratio of . We
identify a diffuse structure 50 kpc () to the NW of the
quasar along the jet axis that corresponds to a enhancement in the
angular density of emission and can be ruled out as a background fluctuation
with a probability of P=0.9985. While with few detected photons the spectral
fit of the structure is uncertain, we find that it has a luminosity of
. These observations therefore
potentially represent the most distant quasar jet yet seen in X-rays. We find
no evidence for excess X-ray emission where the previously-reported radio jets
are seen (which have an overall linear extent of ), and a
bright X-ray point source located along the jet axis to the SE is revealed by
optical and NIR imaging to not be associated with the quasar.Comment: 16 pages, 7 Figures. Accepted for publication the Astrophysical
Journa
Quantitative Constraints on the Reionization History from the IGM Damping Wing Signature in Two Quasars at z > 7
During reionization, neutral hydrogen in the intergalactic medium (IGM)
imprints a damping wing absorption feature on the spectrum of high-redshift
quasars. A detection of this signature provides compelling evidence for a
significantly neutral Universe, and enables measurements of the hydrogen
neutral fraction at that epoch. Obtaining reliable quantitative
constraints from this technique, however, is challenging due to stochasticity
induced by the patchy inside-out topology of reionization, degeneracies with
quasar lifetime, and the unknown unabsorbed quasar spectrum close to rest-frame
Ly. We combine a large-volume semi-numerical simulation of reionization
topology with 1D radiative transfer through high-resolution hydrodynamical
simulations of the high-redshift Universe to construct models of quasar
transmission spectra during reionization. Our state-of-the-art approach
captures the distribution of damping wing strengths in biased quasar halos that
should have reionized earlier, as well as the erosion of neutral gas in the
quasar environment caused by its own ionizing radiation. Combining this
detailed model with our new technique for predicting the quasar continuum and
its associated uncertainty, we introduce a Bayesian statistical method to
jointly constrain the neutral fraction of the Universe and the quasar lifetime
from individual quasar spectra. We apply this methodology to the spectra of the
two highest redshift quasars known, ULAS J1120+0641 and ULAS J1342+0928, and
measured volume-averaged neutral fractions and (posterior medians and 68% credible
intervals) when marginalized over quasar lifetimes of years.Comment: 18 pages, 13 figures. Submitted to Ap
The Discovery of A Luminous Broad Absorption Line Quasar at A Redshift of 7.02
Despite extensive efforts, only two quasars have been found at to date
due to a combination of low spatial density and high contamination from more
ubiquitous Galactic cool dwarfs in quasar selection. This limits our current
knowledge of the super-massive black hole (SMBH) growth mechanism and
reionization history. In this letter, we report the discovery of a luminous
quasar at , DELS J003836.10152723.6 (hereafter J00381527),
selected using photometric data from DESI Legacy imaging Survey (DELS),
Pan-STARRS1 (PS1) imaging Survey, as well as Wide-field Infrared Survey Explore
() mid-infrared all-sky survey. With an absolute magnitude of
=27.1 and bolometric luminosity of =5.610 , J00381527 is the most luminous quasar
known at . Deep optical to near infrared spectroscopic observations
suggest that J0038-1527 hosts a 1.3 billion solar mass BH accreting at the
Eddington limit, with an Eddington ratio of 1.250.19. The CIV broad
emission line of J00381527 is blue-shifted by more than 3000 km s to
the systemic redshift. More detailed investigations of the high quality spectra
reveal three extremely high velocity CIV broad absorption lines (BALs) with
velocity from 0.08 to 0.14 times the speed of light and total balnicity index
of more than 5000 km s, suggesting the presence of relativistic
outflows. J00381527 is the first quasar found at the epoch of reionization
(EoR) with such strong outflows and provides a unique laboratory to investigate
AGN feedback on the formation and growth of the most massive galaxies in the
early universe.Comment: ApJL in pres
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