208 research outputs found
The Discovery of a Gravitationally Lensed Quasar at z = 6.51
Strong gravitational lensing provides a powerful probe of the physical
properties of quasars and their host galaxies. A high fraction of the most
luminous high-redshift quasars was predicted to be lensed due to magnification
bias. However, no multiple imaged quasar was found at z>5 in previous surveys.
We report the discovery of J043947.08+163415.7, a strongly lensed quasar at
z=6.51, the first such object detected at the epoch of reionization, and the
brightest quasar yet known at z>5. High-resolution HST imaging reveals a
multiple imaged system with a maximum image separation theta ~ 0.2", best
explained by a model of three quasar images lensed by a low luminosity galaxy
at z~0.7, with a magnification factor of ~50. The existence of this source
suggests that a significant population of strongly lensed, high redshift
quasars could have been missed by previous surveys, as standard color selection
techniques would fail when the quasar color is contaminated by the lensing
galaxy.Comment: 8 pages, 4 figures, submitted to ApJ
De Novo Unbalanced Translocations in Prader-Willi and Angelman Syndrome Might Be the Reciprocal Product of inv dup(15)s.
De novo unbalanced translocations have a complex history/aetiology
We investigated 52 cases of de novo unbalanced translocations, consisting in a terminally deleted or inverted-duplicated deleted (inv-dup del) 46th chromosome to which the distal portion of another chromosome or its opposite end was transposed. Array CGH, whole-genome sequencing, qPCR, FISH, and trio genotyping were applied. A biparental origin of the deletion and duplication was detected in 6 cases, whereas in 46, both imbalances have the same parental origin. Moreover, the duplicated region was of maternal origin in more than half of the cases, with 25% of them showing two maternal and one paternal haplotype. In all these cases, maternal age was increased. These findings indicate that the primary driver for the occurrence of the de novo unbalanced translocations is a maternal meiotic non-disjunction, followed by partial trisomy rescue of the supernumerary chromosome present in the trisomic zygote. In contrast, asymmetric breakage of a dicentric chromosome, originated either at the meiosis or postzygotically, in which the two resulting chromosomes, one being deleted and the other one inv-dup del, are repaired by telomere capture, appears at the basis of all inv-dup del translocations. Notably, this mechanism also fits with the origin of some simple translocations in which the duplicated region was of paternal origin. In all cases, the signature at the translocation junctions was that of non-homologous end joining (NHEJ) rather than non-allelic homologous recombination (NAHR). Our data imply that there is no risk of recurrence in the following pregnancies for any of the de novo unbalanced translocations we discuss here
LBT/ARGOS adaptive optics observations of z lensed galaxies
Gravitationally lensed systems allow a detailed view of galaxies at high
redshift. High spatial- and spectral-resolution measurements of arc-like
structures can offer unique constraints on the physical and dynamical
properties of high-z systems. We present near-infrared spectra centred on the
gravitational arcs of six known z ~ 2 lensed star-forming galaxies of stellar
masses of 10^9-10^11 Msun and star formation rate (SFR) in the range between 10
and 400 Msun/yr. Ground layer adaptive optics (AO)-assisted observations are
obtained at the Large Binocular Telescope (LBT) with the LUCI spectrographs
during the commissioning of the ARGOS facility. We used MOS masks with curved
slits to follow the extended arched structures and study the diagnostic
emission lines. Combining spatially resolved kinematic properties across the
arc-like morphologies, emission line diagnostics and archival information, we
distinguish between merging and rotationally supported systems, and reveal the
possible presence of ejected gas. For galaxies that have evidence for outflows,
we derive outflow energetics and mass-loading factors compatible with those
observed for stellar winds in local and high-z galaxies. We also use flux ratio
diagnostics to derive gas-phase metallicities. The low signal-to-noise ratio in
the faint H and nitrogen lines allows us to derive an upper limit of ~
0.15 dex for the spatial variations in metallicity along the slit for the
lensed galaxy J1038. Analysed near-infrared spectra presented here represent
the first scientific demonstration of performing AO-assisted multi-object
spectroscopy with narrow curved-shape slits. The increased angular and spectral
resolution, combined with the binocular operation mode with the 8.4-m-wide eyes
of LBT, will allow the characterisation of kinematic and chemical properties of
a large sample of galaxies at high-z in the near future.Comment: 18 pages, 13 figures, accepted for publication in A&
Orbital and dynamical analysis of the system around HR 8799. New astrometric epochs from VLT/SPHERE and LBT/LUCI
HR\,8799 is a young planetary system composed of 4 planets and a double
debris belt. Being the first multi-planetary system discovered with the direct
imaging technique, it has been observed extensively since 1998. This wide
baseline of astrometric measurements, counting over 50 observations in 20
years, permits a detailed orbital and dynamical analysis of the system. To
explore the orbital parameters of the planets, their dynamical history, and the
planet-to-disk interaction, we made follow-up observations of the system during
the VLT/SPHERE GTO program. We obtained 21 observations, most of them in
favorable conditions. In addition, we observed HR\,8799 with the instrument
LBT/LUCI. All the observations were reduced with state-of-the-art algorithms
implemented to apply the spectral and angular differential imaging method. We
re-reduced the SPHERE data obtained during the commissioning of the instrument
and in 3 open-time programs to have homogeneous astrometry. The precise
position of the 4 planets with respect to the host star was calculated by
exploiting the fake negative companions method. To improve the orbital fitting,
we also took into account all of the astrometric data available in the
literature. From the photometric measurements obtained in different
wavelengths, we estimated the planets' masses following the evolutionary
models. We obtained updated parameters for the orbits with the assumption of
coplanarity, relatively small eccentricities, and periods very close to the 2:1
resonance. We also refined the dynamical mass of each planet and the parallax
of the system (24.49 0.07 mas). We also conducted detailed -body
simulations indicating possible positions of a~putative fifth innermost planet
with a mass below the present detection limits of ~\MJup.Comment: 27 pages, 15 figures, A&A in pres
Near-Infrared Observations of Outflows and YSOs in the Massive Star-Forming Region AFGL 5180
Methods: Broad- and narrow-band imaging of AFGL 5180 was made in the NIR with
the LBT, in both seeing-limited (\sim0.5\arcsec) and high angular resolution
(\sim0.09\arcsec) Adaptive Optics (AO) modes, as well as with HST. Archival
ALMA continuum data was also utilized.
Results: At least 40 jet knots were identified via NIR emission from H
and [FeII] tracing shocked gas. Bright jet knots outflowing from the central
most massive protostar, S4, are detected towards the east of the source and are
resolved in fine detail with the AO imaging. Additional knots are distributed
throughout the field, likely indicating the presence of multiple driving
sources. Sub-millimeter sources detected by ALMA are shown to be grouped in two
main complexes, AFGL 5180 M and a small cluster \sim15\arcsec to the south,
AFGL 5180 S. From our NIR continuum images we identify YSO candidates down to
masses of . Combined with the sub-mm sources, this yields a
surface number density of such YSOs of within a
projected radius of about 0.1 pc. Such a value is similar to those predicted by
models of both Core Accretion from a turbulent clump environment and
Competitive Accretion. The radial profile of is relatively flat on scales
out to 0.2~pc, with only modest enhancement around the massive protostar inside
0.05~pc.
Conclusions: This study demonstrates the utility of high-resolution NIR
imaging, in particular with AO, for detecting outflow activity and YSOs in
distant regions. The presented images reveal the complex morphology of
outflow-shocked gas within the large-scale bipolar flow of a massive protostar,
as well as clear evidence for several other outflow driving sources in the
region. Finally, this work presents a novel approach to compare the observed
YSO surface number density from our study against different models of massive
star formation.Comment: Accepted to Astronomy & Astrophysics (A&A
Molecular mechanisms generating and stabilizing terminal 22q13Deletions in 44 subjects with Phelan/McDermid Syndrome
Molecular Mechanisms Generating and Stabilizing Terminal 22q13 Deletions in 44 Subjects with Phelan/McDermid Syndrome
In this study, we used deletions at 22q13, which represent a substantial source of human pathology (Phelan/McDermid syndrome), as a model for investigating the molecular mechanisms of terminal deletions that are currently poorly understood. We characterized at the molecular level the genomic rearrangement in 44 unrelated patients with 22q13 monosomy resulting from simple terminal deletions (72%), ring chromosomes (14%), and unbalanced translocations (7%). We also discovered interstitial deletions between 17–74 kb in 9% of the patients. Haploinsufficiency of the SHANK3 gene, confirmed in all rearrangements, is very likely the cause of the major neurological features associated with PMS. SHANK3 mutations can also result in language and/or social interaction disabilities. We determined the breakpoint junctions in 29 cases, providing a realistic snapshot of the variety of mechanisms driving non-recurrent deletion and repair at chromosome ends. De novo telomere synthesis and telomere capture are used to repair terminal deletions; non-homologous end-joining or microhomology-mediated break-induced replication is probably involved in ring 22 formation and translocations; non-homologous end-joining and fork stalling and template switching prevail in cases with interstitial 22q13.3. For the first time, we also demonstrated that distinct stabilizing events of the same terminal deletion can occur in different early embryonic cells, proving that terminal deletions can be repaired by multistep healing events and supporting the recent hypothesis that rare pathogenic germline rearrangements may have mitotic origin. Finally, the progressive clinical deterioration observed throughout the longitudinal medical history of three subjects over forty years supports the hypothesis of a role for SHANK3 haploinsufficiency in neurological deterioration, in addition to its involvement in the neurobehavioral phenotype of PMS
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