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Another X-ray UFO without a momentum-boosted molecular outflow. ALMA CO(1-0) observations of the galaxy pair IRAS 05054+1718
Get PDFWe present ALMA CO(1-0) observations of the nearby LIRG galaxy pair
IRAS05054+1718 with a new analysis of X-ray data collected between 2012 and
2021 using NuSTAR, Swift, and XMM-Newton. The western component of the pair,
NED01, hosts a Seyfert 1.9 nucleus launching a powerful X-ray UFO. Our X-ray
spectral analysis suggests the UFO could be variable or multi-component in
velocity and constrains its momentum flux to gcms. ALMA CO(1-0) observations include also the
eastern component of the pair, a LIRG with no clear evidence for an AGN. We
study the CO(1-0) kinematics in the two galaxies using the 3D-BAROLO code. In
both sources, we can model the bulk of the CO(1-0) emission with rotating disks
and, after subtracting the best-fit models, we detect compact residual emission
at S/N=15 within kpc from the centre. A molecular outflow in NED01, if
present, cannot be brighter than such residuals, implying an upper limit on its
outflow rate of and on
its momentum rate of gcms. Combined with the revised energetics of the X-ray wind, we
derive an upper limit on the momentum rate ratio of
. We discuss these results in
the context of the expectations of AGN feedback models, and we propose the
X-ray disk wind in NED01 has not significantly impacted the molecular gas
reservoir (yet), and we can constrain its effect to be much smaller than
expectations of AGN ''energy-driven'' feedback models. We also consider and
discuss the hypothesis of asymmetries of the molecular disk not properly
captured by the 3D-BAROLO code. Our results highlight the challenges in testing
the predictions of popular AGN disk-wind feedback theories, even with good
quality multi-wavelength observations
CHEX-MATE: Pressure profiles of six galaxy clusters as seen by SPT and Planck
Get PDFContext. Pressure profiles are sensitive probes of the thermodynamic conditions and the internal structure of galaxy clusters. The intra-cluster gas resides in hydrostatic equilibrium within the dark-matter gravitational potential. However, this equilibrium may be perturbed; for example, as a consequence of thermal energy losses, feedback, and non-thermal pressure supports. Accurate measures of the gas pressure over cosmic time are crucial for constraining cluster evolution as well as the contributions from astrophysical processes. Aims: In this work we present a novel algorithm for deriving the pressure profiles of galaxy clusters from the Sunyaev-Zeldovich (SZ) signal measured on a combination of Planck and South Pole Telescope (SPT) observations. The synergy of the two instruments makes it possible to track the profiles on a wide range of spatial scales. We exploited the sensitivity of the Planck High-Frequency Instrument to the larger scales in order to observe the faint peripheries, and took advantage of the higher spatial resolution of SPT to solve the innermost regions. Methods: We developed a two-step pipeline to take advantage of the specifications of each instrument. We first performed a component separation on the two data sets separately in order to remove the background (CMB) and foreground (Galactic emission) contaminants. We then jointly fitted a parametric pressure profile model on a combination of Planck and SPT data. Results: We validated our technique on a sample of six CHEX-MATE clusters detected by SPT. We compare the results of the SZ analysis with profiles derived from X-ray observations with XMM-Newton. We find excellent agreement between these two independent probes of the gas pressure structure
i(cm)z,, a semi-analytic model for the thermodynamic properties in galaxy clusters: calibrations with mass and redshift, and implication for the hydrostatic bias
Get PDFIn the self-similar scenario for galaxy cluster formation and evolution, the
thermodynamic properties of the X-ray emitting plasma can be predicted in their
dependencies on the halo mass and redshift only. However, several departures
from this simple self-similar scenario have been observed. We show how our
semi-analytic model , which modifies the self-similar predictions
through two temperature-dependent quantities, the gas mass fraction and the temperature variation ,
can be calibrated to incorporate the mass and redshift dependencies. We used a
published set of 17 scaling relations to constrain the parameters of the model.
We were subsequently able to make predictions as to the slope of any observed
scaling relation within a few percent of the central value and about one
of the nominal error. Contextually, the evolution of these scaling
laws was also determined, with predictions within and within 10
percent of the observational constraints. Relying on this calibration, we have
also evaluated the consistency of the predictions on the radial profiles with
some observational datasets. For a sample of high-quality data (X-COP), we were
able to constrain a further parameter of the model, the hydrostatic bias .
By calibrating the model, we have determined that (i) the slopes of the
temperature dependence are and ;
and that (ii) the dependence upon are constrained to be and . These values permit one to estimate
directly how the normalizations of a given quantity changes as a
function of the mass (or temperature) and redshift halo in the form , in very good agreement with
the current observational constraints
Coronal energy release by MHD avalanches. Effects on a structured, active region, multi-threaded coronal loop
Get PDFA possible key element for large-scale energy release in the solar corona is
an MHD kink instability in a single twisted magnetic flux tube. An initial
helical current sheet fragments in a turbulent way into smaller-scale sheets,
similarly to a nanoflare storm. As the loop expands in the radial direction
during the relaxation process, an unstable loop can disrupt nearby stable loops
and trigger an MHD avalanche. Exploratory investigations have been conducted in
previous works with relatively simplified loop configurations. Here, we address
a more realistic environment that comprehensively accounts for most of the
physical effects involved in a stratified atmosphere, typical of an active
region. The question is whether the avalanche process will be triggered, with
what timescales, and how it will develop, as compared with the original,
simpler approach. Three-dimensional MHD simulations describe the interaction of
magnetic flux tubes, which have a stratified atmosphere, including
chromospheric layers, the thin transition region to the corona, and the related
transition from high-beta to low-beta regions. The model also includes the
effects of thermal conduction and of optically thin radiation. Our simulations
address the case where one flux tube among a few is twisted at the footpoints
faster than its neighbours. We show that this flux tube becomes kink unstable
first, in conditions in agreement with those predicted by analytical models. It
rapidly involves nearby stable tubes, instigating significant magnetic
reconnection and dissipation of energy as heat. The heating determines the
development of chromospheric evaporation, while the temperature rises up to
about 10 MK, close to microflares observations. This work confirms that
avalanches are a viable mechanism for the storing and release of magnetic
energy in plasma confined in closed coronal loops, as a result of photospheric
motions
The Planck clusters in the LOFAR sky. IV. LoTSS-DR2: Statistics of radio haloes and re-acceleration models
Get PDFContext. Diffuse cluster-scale synchrotron radio emission is discovered in an increasing number of galaxy clusters in the form of radio haloes, probing the presence of relativistic electrons and magnetic fields in the intra-cluster medium (ICM). The favoured scenario to explain their origin is that they trace turbulent regions that are generated during cluster-cluster mergers, where particles are re-accelerated. In this framework, radio haloes are expected to probe cluster dynamics and are predicted to be more frequent in massive systems, in which more energy becomes available for the re-acceleration of relativistic electrons. For these reasons, statistical studies of galaxy cluster samples have the power to derive fundamental information on the radio haloes populations and on their connection with cluster dynamics, and hence to constrain theoretical models. Furthermore, low-frequency cluster surveys have the potential to shed light on the existence of radio haloes with very steep radio spectra, which are a key prediction of turbulent models and are thought to be generated in less energetic merger events and thus be more common in the Universe. Aims: The main question we address is whether we can explain the observed properties of the radio halo population within the framework of current models. Methods: We study the occurrence and properties of radio haloes from clusters of the second catalogue of Planck Sunyaev Zel'dovich-detected sources that lie within the 5634 deg2 that are covered by the second data release (DR2) of the LOFAR Two-meter Sky Survey. We derive their integral number, flux density, and redshift distributions. We compare these observations with expectations of theoretical models. We also study the connection between radio haloes and cluster mergers by using cluster morphological parameters derived through Chandra and/or XMM-Newton data. Results: We find that the number of observed radio haloes, their radio flux density, and their redshift distributions agree with what is expected in the framework of the re-acceleration scenario. In line with model expectations, the fraction of clusters with radio haloes increases with the cluster mass, confirming the leading role of the gravitational process of cluster formation in the generation of radio haloes. These models predict a large fraction of radio haloes with very steep spectra in the DR2 Planck sample. This will be tested in future studies, but a comparison of the occurrence of haloes in GMRT and LOFAR samples indeed shows a more frequent occurrence of haloes at lower frequencies, suggesting the presence of a population of haloes with very steep spectra that is preferentially detected by LOFAR. Using morphological information, we confirm that radio haloes are preferentially located in merging systems, and that the fraction of newly LOFAR-discovered radio haloes is larger in less strongly disturbed systems...
The Chandra Cygnus OB2 Legacy Survey: Design and X-Ray Point-source Catalog
Get PDFThe Cygnus OB2 association is the largest concentration of young and massive stars within 2 kpc of the Sun, including an estimated ∼65 O-type stars and hundreds of OB stars. The Chandra Cygnus OB2 Legacy Survey is a large imaging program undertaken with the Advanced CCD Imaging Spectrometer on board the Chandra X-ray Observatory. The survey has imaged the central 0.5 deg2 of the Cyg OB2 association with an effective exposure of ∼120 ks and an outer 0.35 deg2 area with an exposure of ∼60 ks. Here we describe the survey design and observations, discuss the data reduction and source detection, and present a catalog of ∼8000 X-ray point sources. The survey design employs a grid of 36 heavily (∼50%) overlapping pointings, a method that overcomes Chandra's low off-axis sensitivity and produces a highly uniform exposure over the inner 0.5 deg2. The full X-ray catalog is described here and is made available online
HI intensity mapping with MeerKAT: power spectrum detection in cross-correlation with WiggleZ galaxies
Get PDFWe present a detection of correlated clustering between MeerKAT radio
intensity maps and galaxies from the WiggleZ Dark Energy Survey. We find a
detection of the cross-correlation power spectrum, the amplitude of
which is proportional to the product of the HI density fraction (), HI bias () and the cross-correlation coefficient (). We
therefore obtain the constraint , at an effective scale of . The intensity maps were obtained from a
pilot survey with the MeerKAT telescope, a 64-dish pathfinder array to the SKA
Observatory (SKAO). The data were collected from 10.5 hours of observations
using MeerKAT's L-band receivers over six nights covering the 11hr field of
WiggleZ, in the frequency range
(0.4000.459 in redshift). This detection is the first
practical demonstration of the multi-dish auto-correlation intensity mapping
technique for cosmology. This marks an important milestone in the roadmap for
the cosmology science case with the full SKAO
Oxygen depletion in giant planets with different formation histories
Get PDFThe atmospheric C/O ratio of exoplanets is widely used to constrain their formation. To guarantee that the C/O ratio provides robust information, we need to accurately quantify the amount of C and O in exoplanetary atmospheres. In the case of O, water and carbon monoxide are generally studied as the two key carriers. However, oxygen is a very reactive element and does not bind only with carbon; depending on the temperature, it also binds to refractory elements. Estimating the amount of oxygen bound to refractory elements is therefore critical for unbiased estimates of the C/O ratio. In this work, we investigate the oxygen deficit due to refractory elements and its effects on the atmospheric C/O ratio of giant exoplanets as a function of their metallicity and equilibrium temperature. We model the composition of planetary atmospheres assuming chemical equilibrium and using as input physically justified elemental mixtures arising from detailed planet formation simulations. Our results show how the interplay between the atmospheric temperature and non-solar abundances of oxygen and refractory elements can sequester large fractions of oxygen, introducing significant biases in evaluating the C/O ratio when this effect is not accounted for. We apply our results to the case of Jupiter in the Solar system and show how the currently estimated water abundance points to a true oxygen abundance that is four times the solar one
High performance w-stacking for imaging radio astronomy data: a parallel and accelerated solution
Get PDFCurrent and upcoming radio-interferometers are expected to produce volumes of data of increasing size that need to be processed in order to generate the corresponding sky brightness distributions through imaging. This represents an outstanding computational challenge, especially when large fields of view and/or high-resolution observations are processed. We have investigated the adoption of modern high performance computing systems specifically addressing the gridding, fast Fourier transform, and w-correction of imaging, combining parallel and accelerated solutions. We have demonstrated that the code we have developed can support data set and images of any size compatible with the available hardware, efficiently scaling up to thousands of cores or hundreds of graphic processing units, keeping the time to solution <1 h even when images of the size of the order of billions or tens of billions of pixels are generated. In addition, portability has been targeted as a primary objective, both in terms of usability on different computing platforms and in terms of performance. The presented results have been obtained on two different state-of-the-art high performance computing architectures
NI-DPU ASW v1.3.9 – Release Notes
No full textThis document describes version 1.3.9 (Flight) of the NISP DPU ASW. This version was successfully
validated using the NISP-AVM setup, see reference [RD-5]