We present a deep XMM-Newton observation of the Galactic halo emission in the direction of the blazar 1ES 1553+113. In order to extract the Galactic halo component from the diffuse soft X-ray ...emission spectrum, accurately modeling the foreground components is crucial. Here we present complex modeling of the foregrounds with unprecedented details. A careful analysis of the spectrum yields two-temperature components of the halo gas ( T 1 em = 10 6.25 − 6.42 K, T 2 em = 10 6.68 − 6.92 K). We find that these temperatures obtained from the emission spectrum are not consistent with those from the absorption spectrum ( T 1 ab = 10 6.07 − 6.13 K, T 2 ab = 10 6.96 − 7.15 K), unlike the previous studies that found only one-temperature component of the Milky Way circumgalactic medium. This provides us with interesting insights into the nature of emitting and absorbing systems. We discuss several possibilities objectively, and conclude that most likely we are observing multiple (3-4) discrete temperatures between 10 5.5 K and ≥ 10 7 K in the Milky Way circumgalactic medium.
Abstract
Solar UV-C photons do not reach Earth’s surface, but are known to be endowed with germicidal properties that are also effective on viruses. The effect of softer UV-B and UV-A photons, which ...copiously reach the Earth’s surface, on viruses are instead little studied, particularly on single-stranded RNA viruses. Here we combine our measurements of the action spectrum of Covid-19 in response to UV light, Solar irradiation measurements on Earth during the SARS-CoV-2 pandemics, worldwide recorded Covid-19 mortality data and our “Solar-Pump” diffusive model of epidemics to show that (a) UV-B/A photons have a powerful virucidal effect on the single-stranded RNA virus Covid-19 and that (b) the Solar radiation that reaches temperate regions of the Earth at noon during summers, is sufficient to inactivate 63% of virions in open-space concentrations (1.5 × 10
3
TCID
50
/mL, higher than typical aerosol) in less than 2 min. We conclude that the characteristic seasonality imprint displayed world-wide by the SARS-Cov-2 mortality time-series throughout the diffusion of the outbreak (with temperate regions showing clear seasonal trends and equatorial regions suffering, on average, a systematically lower mortality), might have been efficiently set by the different intensity of UV-B/A Solar radiation hitting different Earth’s locations at different times of the year. Our results suggest that Solar UV-B/A play an important role in planning strategies of confinement of the epidemics, which should be worked out and set up during spring/summer months and fully implemented during low-solar-irradiation periods.
Abstract
We analyzed Suzaku and Chandra observations of the soft diffuse X-ray background toward four sight lines with the goal of characterizing the X-ray emission from the Milky Way circumgalactic ...medium (CGM). We identified two thermal components of the CGM, one at a uniform temperature of
kT
= 0.176 ± 0.008 keV and the other at temperatures in the range
kT
= 0.65–0.90 keV. The uniform lower-temperature component is consistent with the Galaxy’s virial temperature (∼10
6
K). The temperatures of the hotter components are similar to that recently discovered (∼10
7
K) in the sight line to blazar 1ES 1553+113, passing close to the Fermi bubble. Alternatively, the spectra can be described by just one lower-temperature component with supersolar neon abundance, once again similar to that found in the 1ES 1553+113 sight line. The additional hot component or the overabundance of Ne is required at a significance of >4
σ
, but we cannot distinguish between the two possibilities. These results show that the supervirial temperature gas or an enhanced Ne abundance in the warm-hot gas in the CGM is widespread, and these are not necessarily related to the Fermi bubble.
Abstract We conduct an in-depth spectral analysis of ∼1 Ms XMM-Newton data of the narrow line Seyfert 1 galaxy RE J1034+396. The long exposure ensures high spectral quality and provides us with a ...detailed look at the intrinsic absorption and emission features toward this target. Two warm-absorber (WA) components with different ionization states ( log ( ξ / erg cm s − 1 ) ∼ 4 and log ( ξ / erg cm s − 1 ) ∼ 2.5 – 3 ) are required to explain the intrinsic absorption features in the Reflection Grating Spectrometer spectra. The estimated outflow velocities are around −1400 km s −1 and −(100–300) km s −1 for the high- and low-ionization WA components, respectively. Both absorbers are located beyond the broad-line region and cannot significantly affect the host environment. We analyze the warm absorbers in different flux states. We also examine the 2007 May observation in the low and high phases of quasiperiodic oscillation (QPO). In contrast to previous analyses showing a negative correlation between the high-ionization WA and the QPO phase, we have found no such variation in this WA component. We discover a broad emission bump in the spectral range of ∼12–18 Å, covering the primary features of the high-ionization WA. This emission bump shows a dramatic change in different source states, and its intensity may positively correlate with the QPO phase. The absence of this emission bump in previous work may contribute to the suggested WA–QPO connection.
Abstract
The number of baryons hosted in the disks of galaxies is lower than expected based on the mass of their dark matter halos and the fraction of baryon-to-total matter in the Universe, giving ...rise to the so-called galaxy missing-baryon problem. The presence of cool circumgalactic matter gravitationally bound to its galaxy’s halo up to distances of at least 10 times the size of the galaxy’s disk mitigates the problem but is far from being sufficient for its solution. It has instead been suggested that the galaxy’s missing baryons may hide in a much hotter gaseous phase of the circumgalactic medium, possibly near the halo virial temperature and coexisting with the cool phase. Here we exploit the best available X-ray spectra of known cool circumgalactic absorbers of
L
* galaxies to report the first direct high statistical significance (best estimates ranging from 4.2
σ
to 5.6
σ
, depending on fitting methodology) detection of associated O
vii
absorption in the stacked XMM-Newton and Chandra spectra of three quasars. We show that these absorbers trace the hot medium in the X-ray halo of these systems at log
T
(in K) ≃ 5.8–6.3 (comprising the halo virial temperature
T
vir
≃ 10
6
K). We estimate masses of the X-ray halo within one virial radius within the interval
M
hot
−
CGM
≃
(
1
–
1.7
)
×
10
11
(
Z
/
0.3
Z
⊙
)
−
1
M
⊙
. For these systems, this corresponds to galaxy missing-baryon fractions in the range
ξ
b
=
M
hot
−
CGM
/
M
missing
≃
(
0.7
–
1.2
)
(
Z
/
0.3
Z
⊙
)
−
1
, thus potentially closing the galaxy baryon census in typical
L
* galaxies. Our measurements contribute significantly to the solution of the long-standing galaxy missing-baryon problem and to the understanding of the continuous cycle of baryons in-and-out of galaxies throughout the life of the Universe.
Using a 100 ks XMM-Newton exposure of NGC 4051, we show that the time evolution of the ionlzation state of the X-ray absorbers in response to the rapid and highly variable X-ray continuum constrains ...all the main physical and geometrical properties of an AGN "warm absorber" wind. The absorber consists of two different ionization components, with a difference of approximately 100 in ionization parameter and approximately 5 in column density. By tracking the response in the opacity of the gas to changes in the ionizing continuum, we were able to constrain the electron density of the system. We find n unk = (5.8-21.0) X 10 super(6) cm super(-3) for the high-ionization absorber and n unk > 8.1 x 10 super(7) cm super(-3) for the low-ionization absorber. These densities require that the high- and low-ionization absorbing components of NGC 4051 must be compact, at distances 0.5-1.0 It-days (2200R sub(s) 4400R sub(s)) and <3.5 it-days (<15.800R sub(s)) from the continuum source, respectively. This rules out an origin in the dusty obscuring torus, as the dust sublimation radius is at least an order of magnitude larger ( similar to 12 It-days). An accretion-disk origin for the warm absorber wind is strongly suggested, and an association with the high-ionization, He II emitting, broad emission line region (radius <2 It-days) is possible. The two detected phases are consistent with pressure equilibrium, which suggests that the absorber consists of a two-phase medium. A radial flow in a spherical geometry is unlikely, and a conical wind geometry is preferred. The implied mass cutflow rate from this wind can be well constrained and is 2%-5% of the mass accretion rate. If the mass outflow rate scaling with accretion rate is representative of all quasars, our results imply that warm absorbers in powerful quasars are unlikely to produce important evolutionary effects on their larger environment, unless we are observing the winds before they get fully accelerated. Only in such a scenario can AGN winds be important for cosmic feedback.
Stars and gas in galaxies, hot intracluster medium, and intergalactic photo-ionized gas make up at most half of the baryons that are expected to be present in the universe. The majority of baryons ...are still missing and are expected to be hidden in a web of warm-hot intergalactic medium. This matter was shock-heated during the collapse of density perturbations that led to the formation of the relaxed structures that we see today. Finding the missing baryons and thereby producing a complete inventory of possibly the only detectable component of the energy-mass budget of the universe is crucial to validate or invalidate our standard cosmological model.
Recent cosmological measurements indicate that baryons comprise about four per cent of the total mass-energy density of the Universe, which is in accord with the predictions arising from studies of ...the production of the lightest elements. It is also in agreement with the actual number of baryons detected at early times (redshifts z > 2). Close to our own epoch (z < 2), however, the number of baryons detected add up to just over half (∼ 55 per cent) of the number seen at z > 2 (refs 6-11), meaning that about ∼45 per cent are 'missing'. Here we report a determination of the mass-density of a previously undetected population of baryons, in the warm-hot phase of the intergalactic medium. We show that this mass density is consistent, within the uncertainties, with the mass density of the missing baryons.
Celotno besedilo
Dostopno za:
DOBA, IJS, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Seasonality of acute viral respiratory diseases is a well-known and yet not fully understood phenomenon. Several models have been proposed to explain the regularity of yearly recurring outbreaks and ...the phase differences observed at different latitudes on the Earth. Such models consider known internal causes, primarily the periodic emergence of new virus variants that evade the host immune response. Yet, this alone is generally unable to explain the regularity of recurrences and the observed phase differences.
Here we show that seasonality of viral respiratory diseases, as well as its distribution with latitude on the Earth, can be fully explained by the virucidal properties of UV-B and UV-A solar photons through a daily, minute-scale, resonant forcing mechanism. Such an induced periodicity can last, virtually unperturbed, from tens to hundreds of cycles, and even in the presence of internal dynamics (host's loss of immunity) much slower than seasonal will, on a long period, generate seasonal oscillations.
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•We present a model of epidemics that includes daily resonance by solar UV photons•The model explains the seasonality and latitude dependence of respiratory diseases•It explains the differences in the prevalence of COVID-19 observed at different latitudes•It models well the Italian data of SARS-CoV-2 over the monitored six-month period
Infection Control in Health Technology; Solar Terrestrial Physics; Complex Systems
We have calculated the equivalent widths of the absorption lines produced by Fexxv and Fexxvi in a Compton-thin, low-velocity photoionized material illuminated by the nuclear continuum in active ...galactic nuclei. The results, plotted against the ionization parameter and the column density of the gas, are a complement to those presented by Bianchi & Matt for the emission lines from the same ionic species. As an extension to the work by Bianchi & Matt, we also present a qualitative discussion on the different contributions to the He-like iron emission line complex in the regimes where recombination or resonant scattering dominates, providing a useful diagnostic tool to measure the column density of the gas. Future high-resolution missions (e.g. Astro-E2) will allow us to fully take advantage of these plasma diagnostics. In the meantime, we compare our results with an up-to-date list of Compton-thick and unobscured (at least at the iron line energy) Seyfert galaxies with emission and/or absorption lines from H- and He-like iron observed with Chandra and XMM–Newton.
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