Context. The analysis of the Planck polarization E and B mode power spectra of interstellar dust emission at 353 GHz recently raised new questions concerning the impact of Galactic foregrounds on the ...detection of the polarization of the cosmic microwave background (CMB) and on the physical properties of the interstellar medium (ISM). In the diffuse ISM at high latitude a clear E–B asymmetry is observed that has twice as much power in E modes as in B modes; there is also a positive correlation between the total power, T, and both E and B modes, which is currently interpreted in terms of the link between the structure of interstellar matter and that of the Galactic magnetic field. Aims. In this paper we aim to extend the Planck analysis of the high latitude sky to low Galactic latitudes, investigating the correlation between the T–E–B auto- and cross-correlation power spectra with the gas column density from the diffuse ISM to molecular clouds. Methods. We divided the sky between Galactic latitudes |b| > 5° and |b| < 60° in 552 circular patches, with an area of ~400°2, and we studied the cross-correlations between the T–E–B power spectra and the column density of each patch using the latest release of the Planck polarization data. Results. We find that the B-to-E power ratio ( DlBB/DlEE $\mathcal{D}^{BB}_{\ell}/\mathcal{D}_{\ell}^{EE}$ D l BB / D l EE ) and the TE correlation ratio (rTE) depend on column density. While the former increases going from the diffuse ISM to molecular clouds in the Gould Belt, the latter decreases. This systematic variation must be related to actual changes in ISM properties. The data show significant scatter about this mean trend. The variations of DlBB/DlEE $\mathcal{D}^{BB}_{\ell}/\mathcal{D}_{\ell}^{EE}$ D l BB / D l EE and rTE are observed to be anticorrelated for all column densities. In the diffuse ISM, the variance of these two ratios is consistent with a stochastic non-Gaussian model in which the values of DlBB/DlEE $\mathcal{D}^{BB}_{\ell}/\mathcal{D}_{\ell}^{EE}$ D l BB / D l EE and rTE are fixed. We finally discuss the dependences of TB and EB with column density, which are however hampered by instrumental noise. Conclusions. For the first time, this work shows significant variations of the T–E–B power spectra of dust polarized emission across a large portion of the Galaxy. Their dependence on multipole and gas column density is key for accurate forecasts of next generation CMB experiments and for constraining present models of ISM physics (i.e., dust properties and interstellar turbulence), which are considered responsible for the observed T–E–B signals.
Abstract
GRB 221009A is the brightest gamma-ray burst (GRB) ever detected that has occurred at low Galactic latitude. Owing to this exceptional combination, its prompt X-ray emission could be ...detected for weeks in the form of expanding X-ray rings produced by scattering in Galactic dust clouds. We report on the analysis of 20 rings, generated by dust at distances ranging from 0.3 to 18.6 kpc, detected during two X‐ray Multi Mirror (XMM)-Newton observations performed about 2 and 5 days after the GRB. By fitting the spectra of the rings with different models for the dust composition and grain size distribution, we reconstructed the spectrum of the GRB prompt emission in the 0.7–4 keV energy range as an absorbed power law with photon index Γ = 1–1.4 and absorption in the host galaxy
N
H,z
= (4.1–5.3) × 10
21
cm
−2
. Taking into account the systematic uncertainties regarding the column density of dust contained in the clouds producing the rings, the 0.5–5 keV fluence of GRB 221009A can be constrained between 10
−3
and 7 × 10
−3
erg cm
−2
. Both the fluence and the photon index indicate the presence of a possible soft excess with respect to the extrapolation of the main GRB peak observed at higher energies.
Context.
Faraday tomography of a field centred on the extragalactic point source 3C 196 with the LOw Frequency ARray (LOFAR) revealed an intertwined structure of diffuse polarised emission with ...straight depolarisation canals and tracers of the magnetised and multi-phase interstellar medium (ISM), such as dust and line emission from atomic hydrogen (HI).
Aims.
This study aims at extending the multi-tracer analysis of LOFAR data to three additional fields in the surroundings of the 3C 196 field. For the first time, we study the three-dimensional structure of the LOFAR emission by determining the distance to the depolarisation canals.
Methods.
We used the rolling Hough transform to compare the orientation of the depolarisation canals with that of the filamentary structure seen in HI, and based on starlight and dust polarisation data, with that of the plane-of-the-sky magnetic field. Stellar parallaxes from
Gaia
complemented the starlight polarisation with the corresponding distances.
Results.
Faraday tomography of the three fields shows a rich network of diffuse polarised emission at Faraday depths between − 10 and + 15 rad m
−2
. A complex system of straight depolarisation canals resembles that of the 3C 196 field. The depolarisation canals align both with the HI filaments and with the magnetic field probed by dust. The observed alignment suggests that an ordered magnetic field organises the multiphase ISM over a large area (~20°). In one field, two groups of stars at distances below and above 200 pc, respectively, show distinct magnetic field orientations. These are both comparable with the orientations of the depolarisation canals in the same field. We conclude that the depolarisation canals likely trace the same change in the magnetic field as probed by the stars, which corresponds to the edge of the Local Bubble.
Abstract
We develop a new method for spatially mapping a lower limit on the mass fraction of the cold neutral medium by analyzing the amplitude structure of
T
ˆ
b
(
k
v
)
, the Fourier transform of
T
...b
(
v
), the spectrum of the brightness temperature of the H
i
21 cm line emission with respect to the radial velocity
v
. This advances a broader effort exploiting 21 cm emission line data alone (without absorption line data,
τ
) to extract integrated properties of the multiphase structure of the H
i
gas and to map each phase separately. Using toy models, we illustrate the origin of interference patterns seen in
T
ˆ
b
(
k
v
)
. Building on this, a lower limit on the cold gas mass fraction is obtained from the amplitude of
T
ˆ
b
at high
k
v
. Tested on a numerical simulation of thermally bi-stable turbulence, the lower limit from this method has a strong linear correlation with the “true” cold gas mass fraction from the simulation for a relatively low cold gas mass fraction. At a higher mass fraction, our lower limit is lower than the “true” value, because of a combination of interference and opacity effects. Comparison with absorption surveys shows a similar behavior, with a departure from linear correlation at
N
H I
≳ 3–5 × 10
20
cm
−2
. Application to the DRAO Deep Field from DHIGLS reveals a complex network of cold filaments in the Spider, an important structural property of the thermal condensation of the H
i
gas. Application to the HI4PI survey in the velocity range −90 <
v
< 90 km s
−1
produces a full sky map of a lower limit on the mass fraction of the cold neutral medium at 16.′2 resolution. Our new method has the ability to extract a lower limit on the cold gas mass fraction for massive amounts of emission line data alone with low computing time and memory, pointing the way to new approaches suitable for the new generation of radio interferometers.
Faraday tomography of radio polarimetric data below 200 MHz from the LOw Frequency ARray (LOFAR) has been providing new perspectives on the diffuse and magnetized interstellar medium (ISM). One ...aspect of particular interest is the unexpected discovery of Faraday-rotated synchrotron polarization associated with structures of neutral gas, as traced by atomic hydrogen (HI) and dust. Here, we present the first in-depth numerical study of these LOFAR results. We produced and analyzed comprehensive synthetic observations of low-frequency synchrotron polarization from magneto-hydrodynamical (MHD) simulations of colliding super shells in the multiphase ISM from the literature. Using an analytical approach to derive the ionization state of the multiphase gas, we defined five distinct gas phases over more than four orders of magnitude in gas temperature and density, ranging from hot, and warm fully ionized gas to a cold neutral medium. We focused on establishing the contribution of each gas phase to synthetic observations of both rotation measure and synchrotron polarized intensity below 200 MHz. We also investigated the link between the latter and synthetic observations of optically thin HI gas. We find that it is not only the fully ionized gas, but also the warm partially ionized and neutral phases that strongly contribute to the total rotation measure and polarized intensity. However, the contribution of each phase to the observables strongly depends on the choice of the integration axis and the orientation of the mean magnetic field with respect to the shell collision axis. A strong correlation between the HI synthetic data and synchrotron polarized intensity, reminiscent of the LOFAR results, is obtained with lines of sight perpendicular to the mean magnetic field direction. Our study suggests that multiphase modeling of MHD processes is needed in order to interpret observations of the radio sky at low frequencies. This work is a first step toward understanding the complexity of low-frequency synchrotron emission that will be soon revolutionized thanks to large-scale surveys with LOFAR and the Square Kilometre Array.
The Square Kilometre Array (SKA) will answer fundamental questions about the origin, evolution, properties, and influence of magnetic fields throughout the Universe. Magnetic fields can illuminate ...and influence phenomena as diverse as star formation, galactic dynamics, fast radio bursts, active galactic nuclei, large-scale structure, and dark matter annihilation. Preparations for the SKA are swiftly continuing worldwide, and the community is making tremendous observational progress in the field of cosmic magnetism using data from a powerful international suite of SKA pathfinder and precursor telescopes. In this contribution, we revisit community plans for magnetism research using the SKA, in light of these recent rapid developments. We focus in particular on the impact that new radio telescope instrumentation is generating, thus advancing our understanding of key SKA magnetism science areas, as well as the new techniques that are required for processing and interpreting the data. We discuss these recent developments in the context of the ultimate scientific goals for the SKA era.
Low-frequency radio observations of diffuse synchrotron radiation offer a unique vantage point from which to investigate the intricate relationship between gas and magnetic fields in the formation of ...structures within the Galaxy, spanning from the diffuse interstellar medium (ISM) to star-forming regions. Achieving this pivotal objective hinges on a comprehensive understanding of cosmic-ray properties; these dictate the effective energy distribution of relativistic electrons, which are primarily responsible for the observable synchrotron radiation. Notably, cosmic-ray electrons (CRe) with energies of between 100 MeV and 10 GeV play a crucial role in determining the majority of the sky brightness below the GHz range. However, their energy flux ( j e ) remains elusive because of solar modulation. We propose a way to derive observational constraints on this energy gap of interstellar CRe through the brightness temperature spectral index of low-frequency radio emission, here denoted β obs . We introduce a new parametric analytical model that fits available data for j e in accordance with the β obs values measured in the literature between 50 MHz and 1 GHz for diffuse emission in the Milky Way. Our model accounts for multiple observations considering magnetic-field strengths consistent with existing measurements below 10 μG. We present a first all-sky map of the average component of the magnetic field perpendicular to the line of sight and validate our methodology against state-of-the art numerical simulations of the diffuse ISM. This research makes headway in modeling Galactic diffuse emission with a practical, parametric form. It provides essential insights that will help preparations for the imminent arrival of the Square Kilometre Array.
Irritable bowel syndrome (IBS) is associated with other disorders (comorbidity), reduced quality of life and increased use of health resources. We aimed to explore the impact of comorbidity on cost ...of health care in patients with IBS in general practice.
In this cohort study 208 consecutive patients with IBS (Rome II) were recruited. Sociodemographic data, IBS symptoms, and comorbidity (somatic symptoms, organic diseases and psychiatric disorders) were assessed at baseline. Based on a follow up interview after 6-9 months and use of medical records, IBS and non-IBS related health resource use were measured as consultations, hospitalisations, use of medications and alternative health care products and sick leave days. Costs were calculated by national tariffs and reported in Norwegian Kroner (NOK, 1 EURO equals 8 NOK). Multivariate analyses were performed to identify predictors of costs.
A total of 164 patients (mean age 52 years, 69% female, median duration of IBS 17 years) were available at follow up, 143 patients (88%) had consulted their GP of whom 31 (19%) had consulted for IBS. Mean number of sick- leave days for IBS and comorbidity were 1.7 and 16.3 respectively (p < 0.01), costs related to IBS and comorbidity were 954 NOK and 14854 NOK respectively (p < 0.001). Age, organic diseases and somatic symptoms, but not IBS severity, were significant predictors for total costs.
Costs for health resource use among patients with IBS in general practice were largely explained by comorbidity, which generated ten times the costs for IBS.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Context. Herschel observations have emphasized the role of molecular filaments in star formation. However, the origin and evolution of these filaments are not yet well understood, partly because of ...the lack of kinematic information. Aims. We confirm from a kinematic viewpoint that the Taurus B211/B213 filament is accreting background cloud material, and we investigate the potential influence of large-scale external effects on the formation of the filament. Methods. To examine whether the B211/B213 filament is accreting background gas because of its gravitational potential, we produced a toy accretion model and compared its predictions to the velocity patterns observed in 12CO (1–0) and 13CO (1–0). We also examined the spatial distributions of Hα, Planck 857 GHz dust continuum, and HI emission to search for evidence of large-scale external effects. Results. We estimate that the depth of the Taurus cloud around the B211/B213 filament is ~0.3–0.7 pc under the assumption that the density of the gas is the same as the critical density of 13CO (1–0). Compared to a linear extent of >10 pc in the plane of the sky, this suggests that the 3D morphology of the cloud surrounding the B211/B213 filament is sheet-like. Position–velocity (PV) diagrams observed in 12CO (1–0) and 13CO (1–0) perpendicular to the filament axis show that the emission from the gas surrounding B211/B213 is redshifted to the northeast of the filament and blueshifted to the southwest, and that the velocities of both components approach the velocity of the B211/B213 filament as the line of sight approaches the crest of the filament. The PV diagrams predicted by our accretion model are in good agreement with the observed 12CO (1–0) and 13CO (1–0) PV diagrams, supporting the previously proposed scenario of mass accretion into the filament. Moreover, inspection of the spatial distribution of the Hα and Planck 857 GHz emission in the Taurus–California–Perseus region on scales up to >200 pc suggests that the B211/B213 filament may have formed as a result of an expanding supershell generated by the Per OB2 association. Conclusions. Based on these results, we propose a scenario in which the B211/B213 filament was initially formed by large-scale compression of HI gas and is now growing in mass by gravitationally accreting molecular gas of the ambient cloud.
Large-scale synchrotron loops are recognized as the main source of diffuse radio-continuum emission in the Galaxy at intermediate and high Galactic latitudes, yet their origin remain unexplained. For ...the first time, using a combination of multi-frequency data in the radio band of total and polarized intensities, we were able to associate one arc, hereafter, the Orion-Taurus ridge, with the wall of the most prominent stellar-feedback blown shell in the Solar neighborhood, namely, the Orion-Eridanus superbubble. We traced the Orion-Taurus ridge using 3D maps of interstellar dust extinction and column-density maps of molecular gas,
N
H
2
. We found the Orion-Taurus ridge at a distance of 400 pc, with a plane-of-the-sky extent of 180 pc. Its median
N
H
2
value is (1.4
−0.6
+2.6
) × 10
21
cm
−2
. Thanks to the broadband observations below 100 MHz of the Long Wavelength Array (LWA), we were also able to compute the low-frequency spectral-index map of synchrotron emissivity,
β
, in the Orion-Taurus ridge. We found a flat distribution of
β
with a median value of −2.24
−0.02
+0.03
, which we interpreted in terms of depletion of low-energy (< GeV) cosmic-ray electrons in recent supernova remnants (10
5
–10
6
yr). Our results are consistent with plane-of-the-sky magnetic-field strengths in the Orion-Taurus ridge greater than a few tens of μG (> 30 − 40 μG). We report the first detection of diffuse synchrotron emission from cold-neutral, partly molecular gas in the surroundings of the Orion-Eridanus superbubble. This observation opens a new perspective for studies of the multiphase and magnetized interstellar medium with the advent of future high-sensitivity radio facilities, such as the
C
-Band All-Sky Survey (C-BASS) and the Square Kilometre Array (SKA).
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