OA@INAF - Istituto Nazionale di Astrofisica
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Multi-technique investigation of silicon nitride/aluminum membranes as optical blocking filters for high-energy space missions
Get PDFWe acknowledge Elettra Sincrotrone Trieste for providing access to its synchrotron radiation facilities
and for financial support, we received the Italian full support for both the proposals (Grant
Nos. 20180369 and 20190214). E.M., S.N., and I.P. acknowledge funding from EUROFEL project
(RoadMap ESFRI). The research leading to these results received funding from the European
Space Agency for the project “Large Area high-performance Optical Filters for X-ray instrumentation
– LAOF” (Grant No. 4000120250/17/NL/BJ), and from the European Union’s Horizon 2020
Program for the project AHEAD2020 (Grant No. 871158).X-ray detectors for space astrophysics missions are susceptible to noise caused by photons with energies outside the operating energy range; for this reason, efficient external optical blocking filters are required to shield the detector from the out-of-band radiation. These filters play a crucial role in meeting the scientific requirements of the X-ray detectors, and their proper operation over the life of the mission is
essential for the success of the experimental activity. We studied thin sandwich membranes made of silicon nitride and aluminum as optical blocking filters for high-energy detectors in space missions. Here, we report the results of a multi-technique characterization of SiN membranes with thicknesses in the range from 40 nm to 145 nm coated with few tens of nanometers of aluminum on both sides.
In particular, we have measured the X-ray transmission at synchrotron radiation beamlines, the rejection of ultraviolet, visible, and near-infrared radiation, the amount of native oxide on the aluminum surfaces by X-ray photoelectron spectroscopy, the morphology of the sample surfaces by atomic force microscopy, and the aging effects under proton irradiation
AGN X-ray luminosity function and absorption function in the Early Universe (3 ≤ z ≤ 6)
No full textThe XLF of AGN offers a robust tool to study the evolution and the growth of
SMBHs over cosmic time. Owing to the limited area probed by X-ray surveys,
optical surveys are routinely used to probe the accretion in the high redshift
Universe . However, optical surveys may be incomplete because they are
strongly affected by dust redenning. In this work, we derive the XLF and its
evolution at high redshifts using a large sample of AGNs selected in different
fields with various areas and depths covering a wide range of luminosities.
Additionally, we put the tightest yet constraints on the absorption function in
this redshift regime. In particular, we use more than 600 soft X-ray selected
high-z sources in the Chandra Deep fields, the Chandra COSMOS Legacy survey and
the XMM-XXL northern field. We derive the X-ray spectral properties for all
sources via spectral fitting, using a consistent technique and model. For
modeling the parametric form of the XLF and the absorption function, we use a
Bayesian methodology allowing us to correctly propagate the uncertainties for
the observed X-ray properties of our sources and also the absorption effects.
The evolution of XLF is in agreement with a pure density evolution model
similar to what is witnessed at optical wavelengths, although a luminosity
dependent density evolution model cannot be securely ruled out. A large
fraction ( of our sources are absorbed by column densities of , while \% of the sources are CTK. Our results favor
a scenario where both the ISM of the host and the AGN torus contribute to the
obscuration. The derived BHAD is in agreement with the simulations, if one
takes into account that the X-ray AGN are hosted by massive galaxies, while it
differs from the one derived using JWST data. The latter could be due to the
differences in the AGN and host-galaxy properties
1-arcsecond imaging of the ELAIS-N1 field at 144MHz using the LoTSS survey with the international LOFAR telescope
No full textWe present the first wide area (2.5 × 2.5 deg2) LOFAR high band antenna image at a resolution of 1.2″ × 2″ with a median noise of ≈80 µJy beam‑1. It was made from an 8-hour International LOFAR Telescope (ILT) observation of the ELAIS-N1 field at frequencies ranging from 120 to 168 MHz with the most up-to-date ILT imaging methods. This intermediate resolution falls between the highest possible resolution (0.3″) achievable by using all ILT baselines and the standard 6-arcsec resolution in the LOFAR Two-meter Sky Survey (LoTSS) image products utilising the LOFAR Dutch baselines only. This is the first demonstration of the feasibility of imaging using the ILT at a resolution of ~1″, which provides unique information on source morphology at scales that fall below the surface brightness limits at higher resolutions. The total calibration and imaging computational time is approximately 52 000 core hours, which is nearly five times more than required to produce a 6″ resolution image. We also present a radio source catalogue containing 2263 sources detected over the 2.5 × 2.5 deg2 image of the ELAIS-N1 field, with a peak intensity threshold of 5.5σ. The catalogue has been cross-matched with the LoTSS deep ELAIS-N1 field radio catalogue, and its flux density and positional accuracy have been investigated and corrected accordingly. We find that ~80% of sources that we expect to be detectable based on their peak brightness in the LoTSS 6″ resolution image are detected in this image, which is approximately a factor of two higher than for 0.3″ resolution imaging in the Lockman Hole, implying there is a wealth of information on these intermediate scales
Abundant hydrocarbons in the disk around a very-low-mass star
No full textVery-low-mass stars (those less than 0.3 solar masses) host orbiting terrestrial planets more frequently than other types of stars. The compositions of those planets are largely unknown but are expected to relate to the protoplanetary disk in which they form. We used James Webb Space Telescope mid-infrared spectroscopy to investigate the chemical composition of the planet-forming disk around ISO-ChaI 147, a 0.11-solar-mass star. The inner disk has a carbon-rich chemistry; we identified emission from 13 carbon-bearing molecules, including ethane and benzene. The high column densities of hydrocarbons indicate that the observations probe deep into the disk. The high carbon-to-oxygen ratio indicates radial transport of material within the disk, which we predict would affect the bulk composition of any planets forming in the disk
MINDS: The JWST MIRI Mid-INfrared Disk Survey
No full textThe study of protoplanetary disks has become increasingly important with the Kepler satellite finding that exoplanets are ubiquitous around stars in our galaxy and the discovery of enormous diversity in planetary system architectures and planet properties. High-resolution near-IR and ALMA images show strong evidence for ongoing planet formation in young disks. The JWST MIRI mid-INfrared Disk Survey (MINDS) aims to (1) investigate the chemical inventory in the terrestrial planet-forming zone across stellar spectral type, (2) follow the gas evolution into the disk dispersal stage, and (3) study the structure of protoplanetary and debris disks in the thermal mid-IR. The MINDS survey will thus build a bridge between the chemical inventory of disks and the properties of exoplanets. The survey comprises 52 targets (Herbig Ae stars, T Tauri stars, very low-mass stars and young debris disks). We primarily obtain MIRI/MRS spectra with high signal-to-noise ratio (∼100–500) covering the complete wavelength range from 4.9 to 27.9 μm. For a handful of selected targets we also obtain NIRSpec IFU high resolution spectroscopy (2.87–5.27 μm). We will search for signposts of planet formation in thermal emission of micron-sized dust—information complementary to near-IR scattered light emission from small dust grains and emission from large dust in the submillimeter wavelength domain. We will also study the spatial structure of disks in three key systems that have shown signposts for planet formation, TW Hya and HD 169142 using the MIRI coronagraph at 15.5 μm and 10.65 μm respectively and PDS 70 using NIRCam imaging in the 1.87 μm narrow and the 4.8 μm medium band filter. We provide here an overview of the MINDS survey and showcase the power of the new JWST mid-IR molecular spectroscopy with the TW Hya disk spectrum where we report the detection of the molecular ion and the robust confirmation of HCO+ earlier detected with Spitzer
Abell 746: A Highly Disturbed Cluster Undergoing Multiple Mergers
No full textWe present deep XMM-Newton, Karl G. Jansky Very Large Array, and upgraded Giant Metrewave Radio Telescope observations of Abell 746, a cluster that hosts a plethora of diffuse emission sources that provide evidence for the acceleration of relativistic particles. Our new XMM-Newton images reveal a complex morphology of the thermal gas with several substructures. We observe an asymmetric temperature distribution across the cluster: the southern regions exhibit higher temperatures, reaching ∼9 keV, while the northern regions have lower temperatures (≤4 keV), likely due to a complex merger. We find evidence of three surface brightness edges and one candidate edge, of which three are merger-driven shock fronts. Combining our new data with published LOw-Frequency ARray observations has unveiled the nature of diffuse sources in this system. The bright NW relic shows thin filaments and a high degree of polarization with aligned magnetic field vectors. We detect a density jump, aligned with the fainter relic to the north. To the south, we detect high-temperature regions, consistent with the shock-heated regions and a density jump coincident with the northern tip of the southern radio structure. Its integrated spectrum shows a high-frequency steepening. Lastly, we find that the cluster hosts large-scale radio halo emission. A comparison of the thermal and nonthermal emission reveals an anticorrelation between the bright radio and X-ray features at the center. Our findings suggest that Abell 746 is a complex system that involves multiple mergers...
Highly Significant Detection of X-Ray Polarization from the Brightest Accreting Neutron Star Sco X-1
Get PDFThe Imaging X-ray Polarimetry Explorer measured with high significance the X-ray polarization of the brightest Z-source, Sco X-1, resulting in the nominal 2-8 keV energy band in a polarization degree of 1.0% ± 0.2% and a polarization angle of 8° ± 6° at a 90% confidence level. This observation was strictly simultaneous with observations performed by NICER, NuSTAR, and Insight-HXMT, which allowed for a precise characterization of its broadband spectrum from soft to hard X-rays. The source has been observed mainly in its soft state, with short periods of flaring. We also observed low-frequency quasiperiodic oscillations. From a spectropolarimetric analysis, we associate a polarization to the accretion disk at <3.2% at 90% confidence level, compatible with expectations for an electron scattering dominated optically thick atmosphere at the Sco X-1 inclination of ~44°; for the higher-energy Comptonized component, we obtain a polarization of 1.3% ± 0.4%, in agreement with expectations for a slab of Thomson optical depth of ~7 and an electron temperature of ~3 keV. A polarization rotation with respect to previous observations by OSO-8 and PolarLight, and also with respect to the radio-jet position angle, is observed. This result may indicate a variation of the polarization with the source state that can be related to relativistic precession or a change in the corona geometry with the accretion flow
Zero and Extremely Low-metallicity Rotating Massive Stars: Evolution, Explosion, and Nucleosynthesis Up to the Heaviest Nuclei
Get PDFWe present the evolution and the explosion of two massive stars, 15 and 25 M ⊙, spanning a wide range of initial rotation velocities (from 0 to 800 km s−1) and three initial metallicities: Z = 0 ([Fe/H] = −∞), 3.236 × 10−7 ([Fe/H] = −5), and 3.236 × 10−6 ([Fe/H] = −4). A very large nuclear network of 524 nuclear species extending up to Bi has been adopted. Our main findings may be summarized as follows: (a) rotating models above Z = 0 are able to produce nuclei up to the neutron closure shell N = 50, and in a few cases up to N = 82; (b) rotation drastically inhibits the penetration of the He convective shell in the H-rich mantle, a phenomenon often found in zero metallicity nonrotating massive stars; (c) vice versa, rotation favors the penetration of the O convective shell in the C-rich layers with the consequence of significantly altering the yields of the products of the C, Ne, and O burning; (d) none of the models that reach the critical velocity while in H burning lose more the 1 M ⊙ in this phase; (e) conversely, almost all models able to reach their Hayashi track exceed the Eddington luminosity and dynamically lose almost all their H-rich mantle. These models suggest that rotating massive stars may have contributed significantly to the synthesis of the heavy nuclei in the first phase of enrichment of the interstellar medium, i.e., at early times
The VLBA CANDELS GOODS-North Survey -I. survey design, processing, data products, and source counts
Get PDFThe past decade has seen significant advances in wide-field cm-wave very long baseline interferometry (VLBI), which is timely given the wide-area, synoptic survey-driven strategy of major facilities across the electromagnetic spectrum. While wide-field VLBI poses significant post-processing challenges that can severely curtail its potential scientific yield, man y dev elopments in the km-scale connected-element interferometer sphere are directly applicable to addressing these. Here we present the design, processing, data products, and source counts from a deep (11 μJy beam -1 ), quasi-uniform sensitivity, contiguous wide-field (160 arcmin 2 ) 1.6 GHz VLBI surv e y of the CANDELS GOODS-North field. This is one of the best-studied extragalactic fields at milli-arcsecond resolution and, therefore, is well-suited as a comparative study for our Tera-pixel VLBI image. The derived VLBI source counts show consistency with those measured in the COSMOS field, which broadly traces the AGN population detected in arcsecond-scale radio surv e ys. Ho we ver, there is a distinctive flattening in the S 1.4GHz ∼100-500 μJy flux density range, which suggests a transition in the population of compact faint radio sources, qualitatively consistent with the excess source counts at 15 GHz that is argued to be an unmodelled population of radio cores. This surv e y approach will assist in deriving robust VLBI source counts and broadening the disco v ery space for future wide-field VLBI surv e ys, including VLBI with the Square Kilometre Array, which will include new large field-of-view antennas on the African continent at ≲1000 km baselines. In addition, it may be useful in the design of both monitoring and/or rapidly triggered VLBI transient programmes
UNIVERS@LL: attività 2020-2023
Get PDFIl gruppo “Inclusione” all’interno del settore Didattica e Divulgazione dell’Istituto Nazionale di Astrofisica, ribattezzato UNIVERS@LL nel 2023, è impegnato nello studio e progettazione di attività, eventi e percorsi educativi che garantiscano e favoriscano il più possibile l’equità nell’accesso alla cultura scientifica.
Miriamo a una profonda consapevolezza della diversità e della sua ricchezza, oltre che all'autodeterminazione individuale che deriva dal superamento di stereotipi e barriere.
Raccogliamo e raccontiamo eventi e testimonianze sulle enormi potenzialità che l'astrofisica ha di promuovere l'uguaglianza tra le persone e di creare contesti e opportunità di dialogo universali.
In questo documento sono riportate la storia e l’organizzazione del gruppo dalla sua nascita, gli aambiti dii lavoro e le attività svolte nel periodo 2020-2023