We present new results from the observations of the supernova remnant (SNR) RX J1713.7–3946 (also G347.3–0.5) performed in five distinct pointings with the EPIC instrument on board the satellite ...XMM-Newton. RX J1713.7–3946 is a shell-type SNR dominated by synchrotron radiation in the X-rays. Its emission (emission measure and photon index) as well as the absorption along the line-of-sight has been characterized over the entire SNR. The X-ray mapping of the absorbing column density has revealed strong well-constrained variations ($0.4 \times 10^{22}$ cm$^{-2} \leq N_{{\rm H}} \leq 1.1 \times 10^{22}$ cm-2) and, particularly, a strong absorption in the southwest. Moreover, there are several clues indicating that the shock front of RX J1713.7–3946 is impacting the clouds responsible for the absorption as revealed for instance by the positive correlation between X-ray absorption and X-ray brightness along the western rims. The CO and Hi observations show that the inferred cumulative absorbing column densities are in excellent agreement with the X-ray findings in different parts of the remnant on condition that the SNR lies at a distance of $1.3 \pm 0.4$ kpc, probably in the Sagittarius galactic arm, instead of the commonly-accepted value of 6 kpc. An excess in the CO emission is found in the southwest suggesting that the absorption is due to molecular clouds. A search for OH masers in the southwestern region has been unsuccessful, possibly due to the low density of the clouds. The X-ray mapping of the photon index has also revealed strong variations ($1.8 \leq \Gamma \leq 2.6$). The spectrum is steep in the faint central regions and flat at the presumed shock locations, particularly in the southeast. Nevertheless, the regions where the shock impacts molecular clouds have a steeper spectrum than those where the shock propagates into a low density medium. The search for the thermal emission in RX J1713.7–3946 has been unsuccessful leading to a number density upper limit of $2 \times 10^{-2}$ cm-3 in the ambient medium. This low density corresponds to a reasonable kinetic energy of the explosion provided that the remnant is less than a few thousand years old. A scenario based on a modified ambient medium due to the effect of a progenitor stellar wind is proposed and leads to an estimate of RX J1713.7–3946's progenitor mass between 12 and $16 \: {M}_{\odot}$. The X-ray bright central point source 1WGA J1713.4–3949 detected at the center of SNR RX J1713.7–3946 shows spectral properties very similar to those of the Compact Central Objects found in SNRs and consistent in terms of absorption with that of the central diffuse X-ray emission arising from the SNR. It is highly probable that the point source 1WGA J1713.4–3949 is the compact relic of RX J1713.7–3946's supernova progenitor.
The XXL Survey Faccioli, L.; Pacaud, F.; Sauvageot, J.-L. ...
Astronomy and astrophysics (Berlin),
12/2018, Letnik:
620
Journal Article
Recenzirano
Odprti dostop
Aims.
A well characterised detection pipeline is an important ingredient for X-ray cluster surveys.
Methods.
We present the final development of the XXL Survey pipeline. The pipeline optimally uses ...X-ray information by combining many overlapping observations of a source when possible, both for its detection and its characterisation. It can robustly detect and characterise several types of X-ray sources: AGNs (point-like), galaxy clusters (extended), galaxy clusters contaminated by a central AGN, and pairs of AGNs close on the sky. We perform a thorough suite of validation tests via realistic simulations of
XMM-Newton
images and we introduce new selection criteria for various types of sources that will be detected by the survey.
Results.
We find that the use of overlapping observations allows new clusters to be securely identified that would be missed or less securely identified by using only one observation at a time. We also find that, with the new pipeline we can robustly identify clusters with a central AGN that would otherwise have been missed, and we can flag pairs of AGNs close on the sky that might have been mistaken for a cluster.
In this paper, we investigate two bolometer detectors with a pixel size of 500 µm and 1200 µm to address, respectively, the 0.6 mm and 1.5 mm wavelengths in order to study the temperature and ...polarization of cosmic microwave background (CMB). The pixels are polarization sensitive using Ti/TiN superconducting absorbers. They are deposited on suspended doped Silicon thermometers operating at low temperature, typically in the range 50–100 mK. A quarter-wavelength optical cavity formed between absorbers and metal reflector of these pixels is adapted for an absorption around 100 µm. In order to address the millimeter band, we have used a dielectric (Silicon) superstrate placed above the absorbers to shift the absorption band to larger wavelengths. In this paper, we have conducted finite-element (FEM) electromagnetic simulations to optimize the pixel design. The optical absorption measurements of the pixels were performed at room temperature using a terahertz time-domain spectrometer (THz-TDS) and at 300 mK with a Fourier-transform spectrometer (FTS). Finally, an estimation of pixels performances is discussed showing, an expected high responsivity of around 10
11
V/W and a low noise equivalent power (NEP) of 10
–18
W/Hz
1/2
.
This paper reports our results on the electrothermal modeling of cryogenic silicon bolometers with pixel pitches of 500 and 1200 µm designed for cosmic microwave background polarimetric observation ...in 0.6 mm and 1.5 mm bands. These detectors should provide a high responsivity, typically around 10
11
V/W, and a very low noise equivalent power (NEP) of 10
−18
W/Hz
1/2
between 50 and 100 mK. They are based on doped silicon thermometers, which exhibit a nonohmic behavior described by the “hot electron model” (HEM) at very low temperature under high bias currents. We compare this model to the experimental characterization of these thermometers at cryogenic temperatures to confirm that the HEM is governing their electrical characteristics and their sensitivity at very low temperature. Finally, this model is used to derive the simulated responsivity and NEP performances of the pixels under weak and moderate optical power illumination.
Context.
This paper is the fourth of a series evaluating the ASpiX cosmological method, based on X-ray diagrams, which are constructed from simple cluster observable quantities, namely: count rate ...(CR), hardness ratio (HR), core radius (
r
c
), and redshift.
Aims.
Following extensive tests on analytical toy catalogues (Paper III), we present the results of a more realistic study over a 711 deg
2
template-based maps derived from a cosmological simulation.
Methods.
Dark matter haloes from the Aardvark simulation have been ascribed luminosities, temperatures, and core radii, using local scaling relations and assuming self-similar evolution. The predicted X-ray sky-maps were converted into XMM event lists, using a detailed instrumental simulator. The XXL pipeline runs on the resulting sky images, produces an observed cluster catalogue over which the tests have been performed. This allowed us to investigate the relative power of various combinations of the CR, HR,
r
c
, and redshift information. Two fitting methods were used: a traditional Markov chain Monte Carlo (MCMC) approach and a simple minimisation procedure (Amoeba) whose mean uncertainties are a posteriori evaluated by means of synthetic catalogues. The results were analysed and compared to the predictions from the Fisher analysis (FA).
Results.
For this particular catalogue realisation, assuming that the scaling relations are perfectly known, the CR-HR combination gives
σ
8
and
Ω
m
at the 10% level, while CR-HR-
r
c
-z improves this to ≤3%. Adding a second HR improves the results from the CR-HR
1
-
r
c
combination, but to a lesser extent than when adding the redshift information. When all coefficients of the mass-temperature relation (M-T, including scatter) are also fitted, the cosmological parameters are constrained to within 5–10% and larger for the M-T coefficients (up to a factor of two for the scatter). The errors returned by the MCMC, those by Amoeba and the FA predictions are in most cases in excellent agreement and always within a factor of two. We also study the impact of the scatter of the mass-size relation (M-Rc) on the number of detected clusters: for the cluster typical sizes usually assumed, the larger the scatter, the lower the number of detected objects.
Conclusions.
The present study confirms and extends the trends outlined in our previous analyses, namely the power of X-ray observable diagrams to successfully and easily fit at the same time, the cosmological parameters, cluster physics, and the survey selection, by involving all detected clusters. The accuracy levels quoted should not be considered as definitive. A number of simplifying hypotheses were made for the testing purpose, but this should affect any method in the same way. The next publication will consider in greater detail the impact of cluster shapes (selection and measurements) and of cluster physics on the final error budget by means of hydrodynamical simulations.
CEA has a long history of customizing optoelectronic components for space and astronomy applications. With this expertise we are undertaking a development of cooled silicon bolometers for millimeter ...(mm) wave polarization detection, typically at λ=1.5 mm, in order to address the next generation of space astronomy missions. This work presents the early results on the design and fabrication of an innovative pixel operating at very low temperature between 50 and 100 mK. This pixel is using a Ti/TiN thin film absorber and an ion-implanted silicon thermometer which exhibits a very small heat capacity and a very low 1/f noise at low temperature. This sensor is implemented on a standard SOI substrate. We performed a 2D process simulation of the silicon thermometer and an electromagnetic simulation of the pixel absorption to obtain good performances at low temperature. We present R(T) electrical characterizations of simplified silicon thermometers at low temperature showing a variable range hopping (VRH) model dominating effect. The model prediction shows a good agreement with experimental results.
A high-sensitivity cryogenic sub-millimetre camera is planned for the SPICA space observatory. At the heart of this instrument, new all-silicon bolometer arrays integrate
in pixel
instrumental ...polarimetry capabilities.
In this work, 29 iridium(iii) heteroleptic organometallic complexes based on four cyclometalating and eight ancillary ligands were incorporated in a cross-linked copolymer. The photophysical ...properties of the complexes in chloroform solution and in the polymer matrix were studied. Preliminary scintillation behaviours of the samples, such as the influence of the iridium complex concentration within the matrix or the relative radioluminescence intensity of each sample are given. The scintillators showed promising scintillation yields (up to 1500 ph MeV super(-1)) without the use of a primary fluorophore. Unexpectedly, one of the prepared scintillators exhibited thermoluminescence.
The XXL Survey Faccioli, L.; Pacaud, F.; Sauvageot, J.-L. ...
Astronomy and astrophysics (Berlin),
12/2018, Letnik:
620
Journal Article
Recenzirano
Odprti dostop
Aims. A well characterised detection pipeline is an important ingredient for X-ray cluster surveys. Methods. We present the final development of the XXL Survey pipeline. The pipeline optimally uses ...X-ray information by combining many overlapping observations of a source when possible, both for its detection and its characterisation. It can robustly detect and characterise several types of X-ray sources: AGNs (point-like), galaxy clusters (extended), galaxy clusters contaminated by a central AGN, and pairs of AGNs close on the sky. We perform a thorough suite of validation tests via realistic simulations of XMM-Newton images and we introduce new selection criteria for various types of sources that will be detected by the survey. Results. We find that the use of overlapping observations allows new clusters to be securely identified that would be missed or less securely identified by using only one observation at a time. We also find that, with the new pipeline we can robustly identify clusters with a central AGN that would otherwise have been missed, and we can flag pairs of AGNs close on the sky that might have been mistaken for a cluster.
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