arXiv subjects

Sergio Poppi

Publications and source records attributed to Sergio Poppi.

5 recordsLinked to original sources

arXiv2026

The Atacama Large Aperture Submillimeter Telescope (AtLAST): enabling large-scale sub-mm science beyond 2030

AtLAST is designed to be the largest (sub-)mm single-dish astronomical observatory and the first climate-neutral modern research infrastructure. It offers a unique combination of large aperture (50 m), large field of view (>1 deg), fast scanning speed (up to 3 deg/s), and high surface accuracy (20micron nighttime half wavefront error) that allows >=50% Ruze efficiency up to 1 THz. The design features a rocking chair mount with an active main reflector surface, a high precision closed-loop metrology system, and the space to house six major instruments. Instruments will be periodically updated as spectroscopic focal plane array, detector, coherent amplifier, and semiconductor technologies used in readout and backend electronics will advance over the next decades. AtLAST will be a multi-purpose facility that will produce transformational results in nearly all fields of Astrophysics, such as Astrochemistry, Galactic and Extragalactic Astronomy, Cosmology, Planetary science, Stellar and Solar Physics, High energy astrophysics, and Time domain astronomy. Its unrivalled throughput of 6170 m^2 deg^2 will enable wide-field unbiased surveys. These will overcome extragalactic confusion noise and enable the detection of normal galaxy populations out to z=7. AtLAST will reveal and characterise the missing baryons in the Universe, by mapping the elusive, low surface brightness gas within and around galaxies across cosmic time. AtLAST will be the first green off-grid observatory, powered by a bespoke renewable energy system and reusing its braking energy thanks to a cutting-edge energy recovery system. By sharing surplus power and technological know-how with local communities, AtLAST will contribute to energy justice in Chile. AtLAST's new bold vision of a sustainable pursuit of breakthrough astronomy is an exceptional opportunity to shape the future of scientific research infrastructures. [abridged]

astro-ph.IM↗

arXiv2025

The Southern Twenty-centimetre All-sky Polarization Survey (STAPS): survey description and maps

We present data processing and verification of the Southern Twenty-centimetre All-sky Polarization Survey (STAPS) conducted with Murriyang, the Parkes 64-m telescope. The survey covers the sky area of -89<Dec<0 and the frequency range of 1.3-1.8 GHz split into 1-MHz channels. STAPS was observed commensally with the S-band Polarization All-Sky Survey (S-PASS). The survey is composed of long azimuth scans, which allows us to absolutely calibrate Stokes Q and U with the data processing procedure developed for S-PASS. We obtain I, Q, and U maps in both flux density scale (Jy/beam) and main beam brightness temperature scale (K), for the 301 frequency channels with sufficiently good data. The temperature scale is tied to the Global Magneto-ionic Medium Survey (GMIMS) high-band north sky survey conducted with the Dominion Radio Astrophysical Observatory 26-m telescope. All the STAPS maps are smoothed to a common resolution of 20 arcmin. The rms noise per channel ranges from about 16 mK to 8 mK for I, and from about 8 mK to 5 mK for Q and U at frequencies from 1.3 to 1.8 GHz. The rms noise in Q and U varies with declination and reaches minimum at declination of -89 degree. We also run rotation measure (RM) synthesis and RM clean to obtain peak polarized intensity and Faraday depth maps. The whole STAPS data processing is validated by comparing flux densities of compact sources, pixel flux density versus pixel flux density for Cen A, pixel temperature versus pixel temperature for the entire survey area, and RMs of extragalactic sources between STAPS and other measurements. The uncertainty of the flux density scale is less than 10%. STAPS delivers an L-band (20 cm) multi-frequency polarization view of the Galaxy, and will help advance our understanding of the Galactic magnetic field and magnetized interstellar medium.

astro-ph.GA↗

arXiv2024

The conceptual design of the 50-meter Atacama Large Aperture Submillimeter Telescope (AtLAST)

The (sub)millimeter sky contains a vast wealth of information that is both complementary and inaccessible to other wavelengths. Over half the light we receive is observable at (sub)millimeter wavelengths, yet we have mapped only a small portion of the sky at sufficient spatial resolution and sensitivity to detect and resolve distant galaxies or star forming cores within their large-scale environments. For decades the astronomical community has highlighted the need for a large, high-throughput (sub-)mm ($\lambda\sim 0.35-10$ mm) single dish. The Atacama Large Aperture Submillimeter Telescope (AtLAST), with its 50-m aperture and $2^\circ$ maximal field of view, aims to be such a facility. We present here the preliminary design concept for AtLAST, developed through an EU Horizon 2020-funded design study. Our design approach begins with a long lineage of (sub)millimeter telescopes, relies on calculations and simulations to realize the optics, and uses finite element analysis to optimize the designs for the mechanical structure and subsystems. The demanding technical requirements for AtLAST, set by transformative science goals, have motivated the design effort to combine novel concepts with lessons learned from the past experience of previous efforts. The result is an innovative rocking chair design with six instrument bays, two of which are mounted on Nasmyth platforms, inside a large receiver cabin. Ultimately, AtLAST aims to achieve a surface accuracy of $\leq 20~\mu$m root mean square half wavefront error, corresponding a Ruze efficiency $>50\%$ at 950~GHz. We conclude that closed-loop metrology of the active primary surface will likely be required to achieve our surface accuracy goal. In the next phase of the project, we will prototype and test such metrology on existing platforms, with a goal of delivering a mature, construction-ready design by the end of this decade.

astro-ph.IM↗

arXiv2022

Towards coordinated site monitoring and common strategies for mitigation of Radio Frequency Interference at the Italian radio telescopes

We present a project to implement a national common strategy for the mitigation of the steadily deteriorating Radio Frequency Interference (RFI) situation at the Italian radio telescopes. The project involves the Medicina, Noto, and Sardinia dish antennas and comprised the definition of a coordinated plan for site monitoring as well as the implementation of state-of-the-art hardware and software tools for RFI mitigation. Coordinated monitoring of frequency bands up to 40 GHz has been performed by means of continuous observations and dedicated measurement campaigns with fixed stations and mobile laboratories. Measurements were executed on the frequency bands allocated to the radio astronomy and space research service for shared or exclusive use and on the wider ones employed by the current and under-development receivers at the telescopes. Results of the monitoring campaigns provide a reference scenario useful to evaluate the evolution of the interference situation at the telescopes sites and a case series to test and improve the hardware and software tools we conceived to counteract radio frequency interference. We developed a multi-purpose digital backend for high spectral and time resolution observations over large bandwidths. Observational results demonstrate that the spectrometer robustness and sensitivity enable the efficient detection and analysis of interfering signals in radio astronomical data. A prototype off-line software tool for interference detection and flagging has been also implemented. This package is capable to handle the huge amount of data delivered by the most modern instrumentation on board of the Italian radio telecsopes, like dense focal plane arrays, and its modularity easen the integration of new algorithms and the re-usability in different contexts or telescopes.

astro-ph.IM↗

arXiv2016

Magnetic field disorder and Faraday effects on the polarization of extragalactic radio sources

We present a polarization catalog of 533 extragalactic radio sources with 2.3 GHz total intensity above 420 mJy from the S-band Polarization All Sky Survey, S-PASS, with corresponding 1.4 GHz polarization information from the NRAO VLA Sky Survey, NVSS. We studied selection effects and found that fractional polarization, $π$, of radio objects at both wavelengths depends on the spectral index, source magnetic field disorder, source size and depolarization. The relationship between depolarization, spectrum and size shows that depolarization occurs primarily in the source vicinity. The median $π_{2.3}$ of resolved objects in NVSS is approximately two times larger than that of unresolved sources. Sources with little depolarization are $\sim2$ times more polarized than both highly depolarized and re-polarized sources. This indicates that intrinsic magnetic field disorder is the dominant mechanism responsible for the observed low fractional polarization of radio sources at high frequencies. We predict that number counts from polarization surveys will be similar at 1.4 GHz and at 2.3 GHz, for fixed sensitivity, although $\sim$10% of all sources may be currently missing because of strong depolarization. Objects with $π_{1.4}\approx π_{2.3} \ge 4\%$ typically have simple Faraday structures, so are most useful for background samples. Almost half of flat spectrum ($α\ge -0.5$) and $\sim$25% of steep spectrum objects are re-polarized. Steep spectrum, depolarized sources show a weak negative correlation of depolarization with redshift in the range 0 $<$ z $<$ 2.3. Previous non-detections of redshift evolution are likely due the inclusion of re-polarized sources as well.

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