| 1. |
- Abdalla, H., et al.
(författare)
-
Search for Dark Matter Annihilation Signals from Unidentified Fermi-LAT Objects with HESS
- 2021
-
Ingår i: Astrophysical Journal. - : Institute of Physics Publishing (IOPP). - 0004-637X .- 1538-4357. ; 918:1
-
Tidskriftsartikel (refereegranskat)abstract
- Cosmological N-body simulations show that Milky Way-sized galaxies harbor a population of unmerged dark matter (DM) subhalos. These subhalos could shine in gamma-rays and eventually be detected in gamma-ray surveys as unidentified sources. We performed a thorough selection among unidentified Fermi-Large Area Telescope Objects (UFOs) to identify them as possible tera-electron-volt-scale DM subhalo candidates. We search for very-high-energy (E greater than or similar to 100 GeV) gamma-ray emissions using H.E.S.S. observations toward four selected UFOs. Since no significant very-high-energy gamma-ray emission is detected in any data set of the four observed UFOs or in the combined UFO data set, strong constraints are derived on the product of the velocity-weighted annihilation cross section sigma v by the J factor for the DM models. The 95% confidence level observed upper limits derived from combined H.E.S.S. observations reach sigma vJ values of 3.7 x 10(-5) and 8.1 x 10(-6) GeV(2 )cm(-2 )s(-1) in the W (+) W (-) and tau (+) tau (-) channels, respectively, for a 1 TeV DM mass. Focusing on thermal weakly interacting massive particles, the H.E.S.S. constraints restrict the J factors to lie in the range 6.1 x 10(19)-2.0 x 10(21) GeV(2 )cm(-5) and the masses to lie between 0.2 and 6 TeV in the W (+) W (-) channel. For the tau (+) tau (-) channel, the J factors lie in the range 7.0 x 10(19)-7.1 x 10(20) GeV(2 )cm(-5) and the masses lie between 0.2 and 0.5 TeV. Assuming model-dependent predictions from cosmological N-body simulations on the J-factor distribution for Milky Way-sized galaxies, the DM models with masses >0.3 TeV for the UFO emissions can be ruled out at high confidence level.
|
|
| 2. |
- Abdalla, H., et al.
(författare)
-
LMC N132D : A mature supernova remnant with a power-law gamma-ray spectrum extending beyond 8 TeV
- 2021
-
Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 655
-
Tidskriftsartikel (refereegranskat)abstract
- Context. Supernova remnants (SNRs) are commonly thought to be the dominant sources of Galactic cosmic rays up to the knee of the cosmic-ray spectrum at a few PeV. Imaging Atmospheric Cherenkov Telescopes have revealed young SNRs as very-high-energy (VHE, >100 GeV) gamma-ray sources, but for only a few SNRs the hadronic cosmic-ray origin of their gamma-ray emission is indisputably established. In all these cases, the gamma-ray spectra exhibit a spectral cutoff at energies much below 100 TeV and thus do not reach the PeVatron regime. Aims. The aim of this work was to achieve a firm detection for the oxygen-rich SNR LMC N132D in the VHE gamma-ray domain with an extended set of data, and to clarify the spectral characteristics and the localization of the gamma-ray emission from this exceptionally powerful gamma-ray-emitting SNR. Methods. We analyzed 252 h of High Energy Stereoscopic System (H.E.S.S.) observations towards SNR N132D that were accumulated between December 2004 and March 2016 during a deep survey of the Large Magellanic Cloud, adding 104 h of observations to the previously published data set to ensure a > 5 sigma detection. To broaden the gamma-ray spectral coverage required for modeling the spectral energy distribution, an analysis of Fermi-LAT Pass 8 data was also included. Results. We unambiguously detect N132D at VHE with a significance of 5.7 sigma. We report the results of a detailed analysis of its spectrum and localization based on the extended H.E.S.S. data set. The joint analysis of the extended H.E.S.S and Fermi-LAT data results in a spectral energy distribution in the energy range from 1.7 GeV to 14.8 TeV, which suggests a high luminosity of N132D at GeV and TeV energies. We set a lower limit on a gamma-ray cutoff energy of 8 TeV with a confidence level of 95%. The new gamma-ray spectrum as well as multiwavelength observations of N132D when compared to physical models suggests a hadronic origin of the VHE gamma-ray emission. Conclusions. SNR N132D is a VHE gamma-ray source that shows a spectrum extending to the VHE domain without a spectral cutoff at a few TeV, unlike the younger oxygen-rich SNR Cassiopeia A. The gamma-ray emission is best explained by a dominant hadronic component formed by diffusive shock acceleration. The gamma-ray properties of N132D may be affected by an interaction with a nearby molecular cloud that partially lies inside the 95% confidence region of the source position.
|
|
| 3. |
- Chibueze, J. O., et al.
(författare)
-
A MeerKAT, e-MERLIN, HESS, and Swift search for persistent and transient emission associated with three localized FRBs
- 2022
-
Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press. - 0035-8711 .- 1365-2966. ; 515:1, s. 1365-1379
-
Tidskriftsartikel (refereegranskat)abstract
- We report on a search for persistent radio emission from the one-off fast radio burst (11(B) 20190714A, as well as from two repeating FRBs, 20190711A and 20171019A, using the MeerKAT radio telescope. For FRB 20171019A, we also conducted simultaneous observations with the High-Energy Stereoscopic System (H.E.S.S.) in very high-energy gamma rays and searched for signals in the ultraviolet, optical, and X-ray bands. For this FRB, we obtain a UV flux upper limit of 1.39 x 10(-16) erg cm(-2) s(-1) angstrom(-1), X-ray limit of similar to 6.6 x 10(-14) erg cm(-2) s(-1) and a limit on the very high energy gamma-ray flux Phi(E > 120 GeV) < 1.7 x 10(-12) erg cm(-2) S-1. We obtain a radio upper limit of similar to 15 mu Jy beam(-1) for persistent emission at the locations of both FRBs 20190711A and 20171019A with MeerKAT. However, we detected an almost unresolved (ratio of integrated flux to peak flux is similar to 1.7 beam) radio emission, where the synthesized beam size was similar to 8 arcsec size with a peak brightness of similar to 53 mu Jy beam(-1) at MeerKAT and similar to 86 mu Jy beam(-1) at e-MERLIN, possibly associated with FRB 20190714A at z = 0.2365. This represents the first detection of persistent continuum radio emission potentially associated with a (as-yet) non- repeating FRB. If the association is confirmed, one of the strongest remaining distinction between repeaters and non-repeaters would no longer be applicable. A parallel search for repeat bursts from these FRBs revealed no new detections down to a fluence of 0.08 Jy ms for a 1 ms duration burst.
|
|
| 4. |
- Ricci, M., et al.
(författare)
-
The XXL Survey: XLIV. Sunyaev-Zel'dovich mapping of a low-mass cluster at z ∼1: A multi-wavelength approach
- 2020
-
Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 642
-
Tidskriftsartikel (refereegranskat)abstract
- High-mass clusters at low redshifts have been intensively studied at various wavelengths. However, while more distant objects at lower masses constitute the bulk population of future surveys, their physical state remain poorly explored to date. In this paper, we present resolved observations of the Sunyaev-Zel'dovich (SZ) effect, obtained with the NIKA2 camera, towards the cluster of galaxies XLSSC 102, a relatively low-mass system (M500 ∼ 2 × 1014 M·) at z = 0.97 detected from the XXL survey. We combine NIKA2 SZ data, XMM-Newton X-ray data, and Megacam optical data to explore, respectively, the spatial distribution of the gas electron pressure, the gas density, and the galaxies themselves. We find significant offsets between the X-ray peak, the SZ peak, the brightest cluster galaxy, and the peak of galaxy density. Additionally, the galaxy distribution and the gas present elongated morphologies. This is interpreted as the sign of a recent major merging event, which induced a local boost of the gas pressure towards the north of XLSSC 102 and stripped the gas out of the galaxy group. The NIKA2 data are also combined with XXL data to construct the thermodynamic profiles of XLSSC 102, obtaining relatively tight constraints up to about ∼r500, and revealing properties that are typical of disturbed systems. We also explore the impact of the cluster centre definition and the implication of local pressure substructure on the recovered profiles. Finally, we derive the global properties of XLSSC 102 and compare them to those of high-mass-and-low-redshift systems, finding no strong evidence for non-standard evolution. We also use scaling relations to obtain alternative mass estimates from our profiles. The variation between these different mass estimates reflects the difficulty to accurately measure the mass of low-mass clusters at z ∼ 1, especially with low signal-to-noise ratio data and for a disturbed system. However, it also highlights the strength of resolved SZ observations alone and in combination with survey-like X-ray data. This is promising for the study of high redshift clusters from the combination of eROSITA and high resolution SZ instruments and will complement the new generation of optical surveys from facilities such as LSST and Euclid.
|
|
| 5. |
- Adam, R. M., et al.
(författare)
-
The XXL Survey: LI. Pressure profile and Y SZ -M scaling relation in three low-mass galaxy clusters at z∼1 observed with NIKA2
- 2024
-
Ingår i: Astronomy and Astrophysics. - 0004-6361 .- 1432-0746. ; 684
-
Tidskriftsartikel (refereegranskat)abstract
- Context. The thermodynamical properties of the intracluster medium (ICM) are driven by scale-free gravitational collapse, but they also reflect the rich astrophysical processes at play in galaxy clusters. At low masses (∼1014M) and high redshift (z≳1), these properties remain poorly constrained, observationally speaking, due to the difficulty in obtaining resolved and sensitive data. Aims. We aim to investigate the inner structure of the ICM as seen through the Sunyaev-Zel’dovich (SZ) effect in this regime of mass and redshift. We focused on the thermal pressure profile and the scaling relation between SZ flux and mass, namely the YSZ-M scaling relation. Methods. The three galaxy clusters XLSSC 072 (z=1.002), XLSSC 100 (z=0.915), and XLSSC 102 (z=0.969), with M500∼2×1014M, were selected from the XXL X-ray survey and observed with the NIKA2 millimeter camera to image their SZ signal. XMM-Newton X-ray data were used as a complement to the NIKA2 data to derive masses based on the YX-M relation and the hydrostatic equilibrium. Results. The SZ images of the three clusters, along with the X-ray and optical data, indicate dynamical activity related to merging events. The pressure profile is consistent with that expected for morphologically disturbed systems, with a relatively flat core and a shallow outer slope. Despite significant disturbances in the ICM, the three high-redshift low-mass clusters follow the YSZ-M relation expected from standard evolution remarkably well. Conclusions. These results indicate that the dominant physics that drives cluster evolution is already in place by z∼1, at least for systems with masses above M500∼1014M.
|
|
| 6. |
- Gerotziafas, GT, et al.
(författare)
-
Guidance for the Management of Patients with Vascular Disease or Cardiovascular Risk Factors and COVID-19: Position Paper from VAS-European Independent Foundation in Angiology/Vascular Medicine
- 2020
-
Ingår i: Thrombosis and haemostasis. - : Georg Thieme Verlag KG. - 2567-689X .- 0340-6245. ; 120:12, s. 1597-1628
-
Tidskriftsartikel (refereegranskat)abstract
- COVID-19 is also manifested with hypercoagulability, pulmonary intravascular coagulation, microangiopathy, and venous thromboembolism (VTE) or arterial thrombosis. Predisposing risk factors to severe COVID-19 are male sex, underlying cardiovascular disease, or cardiovascular risk factors including noncontrolled diabetes mellitus or arterial hypertension, obesity, and advanced age. The VAS-European Independent Foundation in Angiology/Vascular Medicine draws attention to patients with vascular disease (VD) and presents an integral strategy for the management of patients with VD or cardiovascular risk factors (VD-CVR) and COVID-19. VAS recommends (1) a COVID-19-oriented primary health care network for patients with VD-CVR for identification of patients with VD-CVR in the community and patients' education for disease symptoms, use of eHealth technology, adherence to the antithrombotic and vascular regulating treatments, and (2) close medical follow-up for efficacious control of VD progression and prompt application of physical and social distancing measures in case of new epidemic waves. For patients with VD-CVR who receive home treatment for COVID-19, VAS recommends assessment for (1) disease worsening risk and prioritized hospitalization of those at high risk and (2) VTE risk assessment and thromboprophylaxis with rivaroxaban, betrixaban, or low-molecular-weight heparin (LMWH) for those at high risk. For hospitalized patients with VD-CVR and COVID-19, VAS recommends (1) routine thromboprophylaxis with weight-adjusted intermediate doses of LMWH (unless contraindication); (2) LMWH as the drug of choice over unfractionated heparin or direct oral anticoagulants for the treatment of VTE or hypercoagulability; (3) careful evaluation of the risk for disease worsening and prompt application of targeted antiviral or convalescence treatments; (4) monitoring of D-dimer for optimization of the antithrombotic treatment; and (5) evaluation of the risk of VTE before hospital discharge using the IMPROVE-D-dimer score and prolonged post-discharge thromboprophylaxis with rivaroxaban, betrixaban, or LMWH.
|
|
| 7. |
- Béthermin, Matthieu, et al.
(författare)
-
CONCERTO: High-fidelity simulation of millimeter line emissions of galaxies and [CII] intensity mapping
- 2022
-
Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 667
-
Tidskriftsartikel (refereegranskat)abstract
- The intensity mapping of the [CII] 158-μm line redshifted to the submillimeter window is a promising probe of the za>4 star formation and its spatial distribution into large-scale structures. To prepare the first-generation experiments (e.g., CONCERTO), we need realistic simulations of the submillimeter extragalactic sky in spectroscopy. We present a new version of the simulated infrared dusty extragalactic sky (SIDES) model including the main submillimeter lines around 1 mm (CO, [CII], [CI]). This approach successfully reproduces the observed line luminosity functions. We then use our simulation to generate CONCERTO-like cubes (125-305 GHz) and forecast the power spectra of the fluctuations caused by the various astrophysical components at those frequencies. Depending on our assumptions on the relation between the star formation rate and [CII] luminosity, and the star formation history, our predictions of the za∼6 [CII] power spectrum vary by two orders of magnitude. This highlights how uncertain the predictions are and how important future measurements will be to improve our understanding of this early epoch. SIDES can reproduce the CO shot noise recently measured at a4;100 GHz by the millimeter-wavelength intensity mapping experiment (mmIME). Finally, we compare the contribution of the different astrophysical components at various redshifts to the power spectra. The continuum is by far the brightest, by a factor of three to 100, depending on the frequency. At 300 GHz, the CO foreground power spectrum is higher than the [CII] one for our base scenario. At lower frequencies, the contrast between [CII] and extragalactic foregrounds is even worse. Masking the known galaxies from deep surveys should allow us to reduce the foregrounds to 20% of the [CII] power spectrum up to z∼ 6.5. However, this masking method will not be sufficient at higher redshifts. The code and the products of our simulation are released publicly, and can be used for both intensity mapping experiments and submillimeter continuum and line surveys.
|
|
| 8. |
- Van Cuyck, M., et al.
(författare)
-
CONCERTO : Extracting the power spectrum of the [CII] emission line
- 2023
-
Ingår i: Astronomy and Astrophysics. - 0004-6361 .- 1432-0746. ; 676
-
Tidskriftsartikel (refereegranskat)abstract
- Context. CONCERTO is the first experiment to perform a [CII] line intensity mapping (LIM) survey on the COSMOS field to target z > 5.2. Measuring the [CII] angular power spectrum allows us to study the role of dusty star-forming galaxies in the star formation history during the epochs of Reionization and post-Reionization. The main obstacle to this measurement is the contamination by bright foregrounds: the dust continuum emission and atomic and molecular lines from foreground galaxies at z ≲ 3.Aims. We evaluate our ability to retrieve the [CII] signal in mock observations of the sky using the Simulated Infrared Dusty Extragalactic Sky (SIDES), which covers the mid-infrared to millimetre range. We also measure the impact of field-to-field variance on the residual foreground contamination.Methods. We compared two methods for dealing with the dust continuum emission from galaxies (i.e. the cosmic infrared background fluctuations): the standard principal component analysis (PCA) and the asymmetric re-weighted penalized least-squares (arPLS) method. For line interlopers, the strategy relies on masking low-redshift galaxies using the instrumental beam profile and external catalogues. As we do not have observations of CO or deep-enough classical CO proxies (such as LIR), we relied on the COSMOS stellar mass catalogue, which we demonstrate to be a reliable CO proxy for masking. To measure the angular power spectrum of masked data, we adapted the P of K EstimatoR (POKER) from cosmic infrared background studies and discuss its use on LIM data.Results. The arPLS method achieves a reduction in the cosmic infrared background fluctuations to a sub-dominant level of the [CII] power at z ∼ 7, a factor of > 70 below our fiducial [CII] model. When using the standard PCA, this factor is only 0.7 at this redshift. The masking lowers the power amplitude of line contamination down to 2 × 10−2 Jy2 sr−1. This residual level is dominated by faint undetected sources that are not clustered around the detected (and masked) sources. For our [CII] model, this results in a detection at z = 5.2 with a power ratio [CII]/(residual interlopers) = 62 ± 32 for a 22% area survey loss. However, at z = 7, [CII]/(residual interlopers) = 2.0 ± 1.4, due to the weak contrast between [CII] and the residual line contamination. Thanks to the large area covered by SIDES-Uchuu, we show that the power amplitude of line residuals varies by 12–15% for z = 5.2 − 7, which is less than the field-to-field variance affecting [CII] power spectra.Conclusions. We present an end-to-end simulation of the extragalactic foreground removal that we ran to detect the [CII] at high redshift via its angular power spectrum. We show that cosmic infrared background fluctuations are not a limiting foreground for [CII] LIM. On the contrary, the CO and [CI] line contamination severely limits our ability to accurately measure the [CII] angular power spectrum at z ≳ 7.
|
|
| 9. |
- Gkogkou, A., et al.
(författare)
-
CONCERTO: Simulating the CO, [CII], and [CI] line emission of galaxies in a 117 deg2 field and the impact of field-to-field variance
- 2023
-
Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 670
-
Tidskriftsartikel (refereegranskat)abstract
- In the submillimeter regime, spectral line scans and line intensity mapping (LIM) are new promising probes for the cold gas content and star formation rate of galaxies across cosmic time. However, both of these two measurements suffer from field-to-field variance. We study the effect of field-to-field variance on the predicted CO and [CII] power spectra from future LIM experiments such as CONCERTO, as well as on the line luminosity functions (LFs) and the cosmic molecular gas mass density that are currently derived from spectral line scans. We combined a 117 deg2 dark matter lightcone from the Uchuu cosmological simulation with the simulated infrared dusty extragalactic sky (SIDES) approach. The clustering of the dusty galaxies in the SIDES-Uchuu product is validated by reproducing the cosmic infrared background anisotropies measured by Herschel and Planck. We find that in order to constrain the CO LF with an uncertainty below 20%, we need survey sizes of at least 0.1 deg2. Furthermore, accounting for the field-to-field variance using only the Poisson variance can underestimate the total variance by up to 80%. The lower the luminosity is and the larger the survey size is, the higher the level of underestimate. At z < 3, the impact of field-to-field variance on the cosmic molecular gas density can be as high as 40% for the 4.6 arcmin2 field, but drops below 10% for areas larger than 0.2 deg2. However, at z > 3 the variance decreases more slowly with survey size and for example drops below 10% for 1 deg2 fields. Finally, we find that the CO and [CII] LIM power spectra can vary by up to 50% in 1 deg2 fields. This limits the accuracy of the constraints provided by the first 1 deg2 surveys. In addition the level of the shot noise power is always dominated by the sources that are just below the detection thresholds, which limits its potential for deriving number densities of faint [CII] emitters. We provide an analytical formula to estimate the field-to-field variance of current or future LIM experiments given their observed frequency and survey size. The underlying code to derive the field-to-field variance and the full SIDES-Uchuu products (catalogs, cubes, and maps) are publicly available.
|
|
| 10. |
|
|
