arXiv subjects

F. Guidi

Publications and source records attributed to F. Guidi.

46 records · Page 3Linked to original sources

arXiv2023

QUIJOTE scientific results -- V. The microwave intensity and polarisation spectra of the Galactic regions W49, W51 and IC443

We present new intensity and polarisation maps obtained with the QUIJOTE experiment towards the Galactic regions W49, W51 and IC443, covering the frequency range from 10 to 20 GHz at $\sim$ 1 deg angular resolution, with a sensitivity in the range 35-79 $μ$K/beam for total intensity and 13-23 $μ$K/beam for polarisation. For each region, we combine QUIJOTE maps with ancillary data at frequencies ranging from 0.4 to 3000 GHz, reconstruct the spectral energy distribution and model it with a combination of known foregrounds. We detect anomalous microwave emission (AME) in total intensity towards W49 at 4.7$σ$ and W51 at 4.0$σ$ with peak frequencies $ν_{AME}$ = (20.0 $\pm$ 1.4) GHz and $ν_{AME}$ = (17.7 $\pm$ 3.6) GHz respectively; this is the first detection of AME towards W51. The contamination from ultra-compact HII regions to the residual AME flux density is estimated at 10% in W49 and 5% in W51, and does not rule out the AME detection. The polarised SEDs reveal a synchrotron contribution with spectral indices $α_s$ = -0.67 $\pm$ 0.10 in W49 and $α_s$ = -0.51 $\pm$ 0.07 in W51, ascribed to the diffuse Galactic emission and to the local supernova remnant respectively. Towards IC443 in total intensity we measure a broken power-law synchrotron spectrum with cut-off frequency $ν_{0,s}$ = (114 $\pm$ 73) GHz, in agreement with previous studies; our analysis, however, rules out any AME contribution which had been previously claimed towards IC443. No evidence of polarised AME emission is detected in this study.

astro-ph.GA↗

arXiv2023

QUIJOTE scientific results -- IX. Radio sources in the QUIJOTE-MFI wide survey maps

We present the catalogue of Q-U-I JOint TEnerife (QUIJOTE) Wide Survey radio sources extracted from the maps of the Multi-Frequency Instrument compiled between 2012 and 2018. The catalogue contains 786 sources observed in intensity and polarization, and is divided into two separate sub-catalogues: one containing 47 bright sources previously studied by the \emph{Planck} collaboration and an extended catalogue of 739 sources either selected from the \emph{Planck} Second Catalogue of Compact Sources or found through a blind search carried out with a Mexican Hat 2 wavelet. A significant fraction of the sources in our catalogue (38.7 per cent) are within the $|b| \leq 20^\circ$ region of the Galactic plane. We determine statistical properties for those sources that are likely to be extragalactic. We find that these statistical properties are compatible with currently available models, with a $\sim$1.8 Jy completeness limit at 11 GHz. We provide the polarimetric properties of (38, 33, 31, 23) sources with P detected above the $99.99\%$ significance level at (11, 13, 17, 19) GHz, respectively. Median polarization fractions are in the $2.8$-$4.7$\% range in the 11-19 GHz frequency interval. We do not distinguish between Galactic and extragalactic sources here. The results presented here are consistent with those reported in the literature for flat- and steep-spectrum radio sources.

astro-ph.GA↗

arXiv2022

Searching for axion-like time-dependent cosmic birefringence with data from SPT-3G

Ultralight axionlike particles (ALPs) are compelling dark matter candidates because of their potential to resolve small-scale discrepancies between $Λ$CDM predictions and cosmological observations. Axion-photon coupling induces a polarization rotation in linearly polarized photons traveling through an ALP field; thus, as the local ALP dark matter field oscillates in time, distant static polarized sources will appear to oscillate with a frequency proportional to the ALP mass. We use observations of the cosmic microwave background from SPT-3G, the current receiver on the South Pole Telescope, to set upper limits on the value of the axion-photon coupling constant $g_{ϕγ}$ over the approximate mass range $10^{-22} - 10^{-19}$ eV, corresponding to oscillation periods from 12 hours to 100 days. For periods between 1 and 100 days ($4.7 \times 10^{-22} \text{ eV} \leq m_ϕ\leq 4.7 \times 10^{-20} \text{ eV}$), where the limit is approximately constant, we set a median 95% C.L. upper limit on the amplitude of on-sky polarization rotation of 0.071 deg. Assuming that dark matter comprises a single ALP species with a local dark matter density of $0.3\text{ GeV/cm}^3$, this corresponds to $g_{ϕγ} < 1.18 \times 10^{-12}\text{ GeV}^{-1} \times \left( \frac{m_ϕ}{1.0 \times 10^{-21} \text{ eV}} \right)$. These new limits represent an improvement over the previous strongest limits set using the same effect by a factor of ~3.8.

astro-ph.CO↗

arXiv2021

The PICASSO map-making code: application to a simulation of the QUIJOTE northern sky survey

Map-making is an important step for the data analysis of Cosmic Microwave Background (CMB) experiments. It consists of converting the data, which are typically a long, complex and noisy collection of measurements, into a map, which is an image of the observed sky. We present in this paper a new map-making code named PICASSO (Polarization and Intensity CArtographer for Scanned Sky Observations), which was implemented to construct intensity and polarization maps from the Multi Frequency Instrument (MFI) of the QUIJOTE (Q-U-I Joint TEnerife) CMB polarization experiment. PICASSO is based on the destriping algorithm, and is suited to address specific issues of ground-based microwave observations, with a technique that allows the fit of a template function in the time domain, during the map-making step. This paper describes the PICASSO code, validating it with simulations and assessing its performance. For this purpose, we produced realistic simulations of the QUIJOTE-MFI survey of the northern sky (approximately $\sim 20,000\,$deg$^2$), and analysed the reconstructed maps with PICASSO, using real and harmonic space statistics. We show that, for this sky area, PICASSO is able to reconstruct, with high fidelity, the injected signal, recovering all the scales with $\ell>10$ in TT, EE and BB. The signal error is better than 0.001% at $20<\ell<200$. Finally, we validated some of the methods that will be applied to the real wide-survey data, like the detection of the CMB anisotropies via cross-correlation analyses. Despite that the implementation of PICASSO is specific for QUIJOTE-MFI data, it could be adapted to other experiments.

astro-ph.IM↗

arXiv2021

Study of the thermal and nonthermal emission components in M31: the Sardinia Radio Telescope view at 6.6 GHz

The Andromeda galaxy is the best-known large galaxy besides our own Milky Way. Several images and studies exist at all wavelengths from radio to hard X-ray. Nevertheless, only a few observations are available in the microwave range where its average radio emission reaches the minimum. In this paper, we want to study the radio morphology of the galaxy, decouple thermal from nonthermal emission, and extract the star formation rate. We also aim to derive a complete catalog of radio sources for the mapped patch of sky. We observed the Andromeda galaxy with the Sardinia Radio Telescope at 6.6 GHz with very high sensitivity and angular resolution, and an unprecedented sky coverage. Using new 6.6 GHz data and Effelsberg radio telescope ancillary data, we confirm that, globally, the spectral index is $\sim 0.7-0.8$, while in the star forming regions it decreases to $\sim 0.5$. By disentangling (gas) thermal and nonthermal emission, we find that at 6.6 GHz, thermal emission follows the distribution of HII regions around the ring. Nonthermal emission within the ring appears smoother and more uniform than thermal emission because of diffusion of the cosmic ray electrons away from their birthplaces. This causes the magnetic fields to appear almost constant in intensity. Furthermore, we calculated a map of the star formation rate based on the map of thermal emission. Integrating within a radius of $R_{max}=15$ kpc, we obtained a total star formation rate of $0.19 \pm 0.01$ $M_{\odot}$/yr in agreement with previous results in the literature. Finally, we correlated our radio data with infrared images of the Andromeda galaxy. We find an unexpectedly high correlation between nonthermal and mid-infrared data in the central region, with a correlation parameter $r=0.93$.

astro-ph.GA↗

arXiv2021

Detection of Spectral Variations of Anomalous Microwave Emission with QUIJOTE and C-BASS

Anomalous Microwave Emission (AME) is a significant component of Galactic diffuse emission in the frequency range $10$-$60\,$GHz and a new window into the properties of sub-nanometre-sized grains in the interstellar medium. We investigate the morphology of AME in the $\approx10^{\circ}$ diameter $λ$ Orionis ring by combining intensity data from the QUIJOTE experiment at $11$, $13$, $17$ and $19\,$GHz and the C-Band All Sky Survey (C-BASS) at $4.76\,$GHz, together with 19 ancillary datasets between $1.42$ and $3000\,$GHz. Maps of physical parameters at $1^{\circ}$ resolution are produced through Markov Chain Monte Carlo (MCMC) fits of spectral energy distributions (SEDs), approximating the AME component with a log-normal distribution. AME is detected in excess of $20\,σ$ at degree-scales around the entirety of the ring along photodissociation regions (PDRs), with three primary bright regions containing dark clouds. A radial decrease is observed in the AME peak frequency from $\approx35\,$GHz near the free-free region to $\approx21\,$GHz in the outer regions of the ring, which is the first detection of AME spectral variations across a single region. A strong correlation between AME peak frequency, emission measure and dust temperature is an indication for the dependence of the AME peak frequency on the local radiation field. The AME amplitude normalised by the optical depth is also strongly correlated with the radiation field, giving an overall picture consistent with spinning dust where the local radiation field plays a key role.

astro-ph.GA↗

arXiv2019

Strong evidence of Anomalous Microwave Emission from the flux density spectrum of M31

We have observed the Andromeda galaxy, Messier 31 (M31), at 6.7GHz with the Sardinia Radio Telescope. We mapped the radio emission in the C-band, re-analyzed WMAP and Planck maps, as well as other ancillary data, and we have derived an overall integrated flux density spectrum from the radio to the infrared. This allowed us to estimate the emission budget from M31. Integrating over the whole galaxy, we found strong and highly significant evidence for anomalous microwave emission (AME), at the level of (1.45+0.17-0.19)Jy at the peaking frequency of ~25GHz. Decomposing the spectrum into known emission mechanisms such as free-free, synchrotron, thermal dust, and AME arising from electric dipole emission from rapidly rotating dust grains, we found that the overall emission from M31 is dominated, at frequencies below 10GHz, by synchrotron emission with a spectral index of -1.10+0.10-0.08, with subdominant free-free emission. At frequencies >10GHz, AME has a similar intensity to that of synchrotron and free-free emission, overtaking them between 20GHz and 50GHz, whereas thermal dust emission dominates the emission budget at frequencies above 60GHz, as expected.

astro-ph.GA↗

arXiv2019

QUIJOTE Scientific results. III. Microwave spectrum of intensity and polarization in the Taurus molecular cloud Complex and L1527

We present new intensity and polarization observations of the Taurus molecular cloud (TMC) region in the frequency range 10-20 GHz with the Multi-Frequency Instrument (MFI) mounted on the first telescope of the QUIJOTE experiment. From the combination of the QUIJOTE data with the WMAP 9-yr data release, the Planck second data release, the DIRBE maps and ancillary data, we detect an anomalous microwave emission (AME) component with flux density $S_{\rm AME, peak} = 43.0 \pm 7.9\,$Jy in the Taurus Molecular Cloud (TMC) and $S_{\rm AME, peak} = 10.7 \pm 2.7\,$Jy in the dark cloud nebula L1527, which is part of the TMC. In the TMC the diffuse AME emission peaks around a frequency of 19 GHz, compared with an emission peak about a frequency of 25 GHz in L1527. In the TMC, the best constraint on the level of AME polarisation is obtained at the Planck channel of 28.4 GHz, with an upper limit $π_{\rm AME}<$4.2$\,\%$ (95$\,\%$ C. L.), which reduces to $π_{\rm AME} <$3.8$\,\%$ (95$\,\%$ C.L.) if the intensity of all the free-free, synchrotron and thermal dust components are negligible at this frequency. The same analysis in L1527 leads to $π_{\rm AME}<$5.3$\%$ (95$\,\%$C.L.), or $π_{\rm AME}<$4.5$\,\%$ (95$\%$C.L.) under the same assumption. We find that in the TMC and L1527 on average about $80\%$ of the HII gas should be mixed with thermal dust. Our analysis shows how the QUIJOTE-MFI 10-20 GHz data provides key information to properly separate the synchrotron, free-free and AME components.

astro-ph.GA↗

arXiv2015

A Survey on Retrieval of Mathematical Knowledge

We present a short survey of the literature on indexing and retrieval of mathematical knowledge, with pointers to 72 papers and tentative taxonomies of both retrieval problems and recurring techniques.

cs.IR↗

arXiv2008

The Formal System lambda-delta

The formal system lambda-delta is a typed lambda calculus that pursues the unification of terms, types, environments and contexts as the main goal. lambda-delta takes some features from the Automath-related lambda calculi and some from the pure type systems, but differs from both in that it does not include the Pi construction while it provides for an abbreviation mechanism at the level of terms. lambda-delta enjoys some important desirable properties such as the confluence of reduction, the correctness of types, the uniqueness of types up to conversion, the subject reduction of the type assignment, the strong normalization of the typed terms and, as a corollary, the decidability of type inference problem.

cs.LO↗