ORCID Profile
0000-0002-4698-2607
Current Organisations
Australian National University
,
Osservatorio Astronomico di Cagliari
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Publisher: American Astronomical Society
Date: 08-2003
DOI: 10.1086/378398
Publisher: Springer Science and Business Media LLC
Date: 2013
DOI: 10.1038/NATURE11734
Abstract: The nucleus of the Milky Way is known to harbour regions of intense star formation activity as well as a supermassive black hole. Recent observations have revealed regions of γ-ray emission reaching far above and below the Galactic Centre (relative to the Galactic plane), the so-called 'Fermi bubbles'. It is uncertain whether these were generated by nuclear star formation or by quasar-like outbursts of the central black hole and no information on the structures' magnetic field has been reported. Here we report observations of two giant, linearly polarized radio lobes, containing three ridge-like substructures, emanating from the Galactic Centre. The lobes each extend about 60 degrees in the Galactic bulge, closely corresponding to the Fermi bubbles, and are permeated by strong magnetic fields of up to 15 microgauss. We conclude that the radio lobes originate in a biconical, star-formation-driven (rather than black-hole-driven) outflow from the Galaxy's central 200 parsecs that transports a huge amount of magnetic energy, about 10(55) ergs, into the Galactic halo. The ridges wind around this outflow and, we suggest, constitute a 'phonographic' record of nuclear star formation activity over at least ten million years.
Publisher: International Union of Radio Science (URSI)
Date: 2021
DOI: 10.46620/21-0026
Publisher: American Astronomical Society
Date: 02-03-2018
Publisher: Springer-Verlag
Date: 2003
DOI: 10.1007/10857580_39
Publisher: EDP Sciences
Date: 2005
DOI: 10.1051/EAS:2005013
Publisher: Oxford University Press (OUP)
Date: 21-06-2004
Publisher: EDP Sciences
Date: 07-2017
Publisher: Oxford University Press (OUP)
Date: 02-11-2019
DOI: 10.1093/BIOLINNEAN/BLZ140
Abstract: Owing to their close affinity, the African great apes are of interest in the study of human evolution. Although numerous researchers have described the ancestors we share with these species with reference to extant great apes, few have done so with phylogenetic comparative methods. One obstacle to the application of these techniques is the within-species phenotypic variation found in this group. Here, we leverage this variation, modelling common ancestors using ancestral state reconstructions (ASRs) with reference to subspecies-level trait data. A subspecies-level phylogeny of the African great apes and humans was estimated from full-genome mitochondrial DNA sequences and used to implement ASRs for 14 continuous traits known to vary between great ape subspecies. Although the inclusion of within-species phenotypic variation increased the phylogenetic signal for our traits and improved the performance of our ASRs, whether this was done through the inclusion of subspecies phylogeny or through the use of existing methods made little difference. Our ASRs corroborate previous findings that the last common ancestor of humans, chimpanzees and bonobos was a chimp-like animal, but also suggest that the last common ancestor of humans, chimpanzees, bonobos and gorillas was an animal unlike any extant African great ape.
Publisher: American Astronomical Society
Date: 31-05-2019
Publisher: Oxford University Press (OUP)
Date: 21-03-2006
Publisher: SPIE
Date: 08-10-2004
DOI: 10.1117/12.551408
Publisher: EDP Sciences
Date: 26-01-2017
Publisher: Oxford University Press (OUP)
Date: 06-2005
Publisher: Oxford University Press (OUP)
Date: 11-01-2021
Abstract: Since chemical abundances are inherited between generations of stars, we use them to trace the evolutionary history of our Galaxy. We present a robust methodology for creating a phylogenetic tree, a biological tool used for centuries to study heritability. Combining our phylogeny with information on stellar ages and dynamical properties, we reconstruct the shared history of 78 stars in the solar neighbourhood. The branching pattern in our tree supports a scenario in which the thick disc is an ancestral population of the thin disc. The transition from thick to thin disc shows an anomaly, which we attribute to a star formation burst. Our tree shows a further signature of the variability in stars similar to the Sun, perhaps linked to a minor star formation enhancement creating our Solar system. In this paper, we demonstrate the immense potential of a phylogenetic perspective and interdisciplinary collaboration, where with borrowed techniques from biology we can study key processes that have contributed to the evolution of the Milky Way.
Publisher: Oxford University Press (OUP)
Date: 03-2005
Publisher: Oxford University Press (OUP)
Date: 29-08-2017
Publisher: Oxford University Press (OUP)
Date: 09-11-2018
Publisher: Elsevier BV
Date: 05-2004
Publisher: Oxford University Press (OUP)
Date: 14-05-2010
Publisher: AIP
Date: 2002
DOI: 10.1063/1.1471845
Publisher: SPIE
Date: 02-2003
DOI: 10.1117/12.458896
Publisher: EDP Sciences
Date: 09-2018
DOI: 10.1051/0004-6361/201833358
Abstract: We report the detection of a new Galactic bubble at the interface between the halo and the Galactic disc. We suggest that the nearby Lupus complex and parts of the Ophiuchus complex constitute the denser parts of the structure. This young bubble, ≲3 Myr old, could be the remnant of a supernova and it expands inside a larger HI loop that has been created by the outflows of the Upper Scorpius OB association. An HI cavity filled with hot X-ray gas is associated with the structure, which is consistent with the Galactic chimney scenario. The X-ray emission extends beyond the west and north-west edges of the bubble, suggesting that hot gas outflows are breaching the cavity, possibly through the fragmented Lupus complex. Analyses of the polarised radio synchrotron and of the polarised dust emission of the region suggest the connection of the Galactic centre spur with the young Galactic bubble. A distribution of HI clumps that spatially corresponds well to the cavity boundaries was found at V LSR ≃−100 km s −1 . Some of these HI clumps are forming jets, which may arise from the fragmented part of the bubble. We suggest that these clumps might be “dripping” cold clouds from the shell walls inside the cavity that is filled with hot ionised gas. It is possible that some of these clumps are magnetised and were then accelerated by the compressed magnetic field at the edge of the cavity. Such a mechanism would challenge the Galactic accretion and fountain model, where high-velocity clouds are considered to be formed at high Galactic latitude from hot gas flows from the Galactic plane.
Publisher: American Astronomical Society
Date: 24-04-2015
Publisher: AIP
Date: 2002
DOI: 10.1063/1.1471864
Publisher: Oxford University Press (OUP)
Date: 25-03-2017
DOI: 10.1093/MNRAS/STX746
Publisher: Oxford University Press (OUP)
Date: 02-2013
DOI: 10.1093/MNRAS/STT002
Publisher: Oxford University Press (OUP)
Date: 15-03-2017
DOI: 10.1093/MNRAS/STX642
Publisher: EDP Sciences
Date: 17-05-2021
Publisher: Oxford University Press (OUP)
Date: 17-07-2006
Publisher: SPIE
Date: 08-10-2004
DOI: 10.1117/12.551671
Publisher: EDP Sciences
Date: 2005
DOI: 10.1051/EAS:2005040
Publisher: EDP Sciences
Date: 10-2018
DOI: 10.1051/0004-6361/201832846
Abstract: Context . Radio loud active galactic nuclei (AGN) are episodic in nature, cycling through periods of activity and quiescence. The study of this duty cycle has recently gained new relevance because of the importance of AGN feedback for galaxy evolution. Aims . In this work we investigate the duty cycle of the radio galaxy B2 0258+35, which was previously suggested to be a restarted radio galaxy based on its morphology. The radio source consists of a pair of kpc-scale jets embedded in two large-scale lobes (∼240 kpc) with relaxed shape and very low surface brightness, which resemble remnants of a past AGN activity. Methods . We have combined new LOFAR data at 145 MHz and new Sardinia Radio Telescope data at 6600 MHz with available WSRT data at 1400 MHz to investigate the spectral properties of the outer lobes and derive their age. Results . Interestingly, the spectrum of both the outer northern and southern lobes is not ultra-steep as expected for an old ageing plasma with spectral index values equal to α 145 1400 = 0.48 ± 0.11 and α 1400 6600 = 0.69 ± 0.20 in the outer northern lobe, and α 145 1400 = 0.73 ± 0.07 in the outer southern lobe. Moreover, despite the wide frequency coverage available for the outer northern lobe (145–6600 MHz), we do not identify a significant spectral curvature (SPC ≃ 0.2 ± 0.2). Conclusions . While mechanisms such as in-situ particle reacceleration, mixing or compression can temporarily play a role in preventing the spectrum from steepening, in no case seem the outer lobes to be compatible with being very old remnants of past activity as previously suggested (with age ≳ 80 Myr). We conclude that either the large-scale lobes are still fuelled by the nuclear engine or the jets have switched off no more than a few tens of Myr ago, allowing us to observe both the inner and outer structure simultaneously. Our study shows the importance of combining morphological and spectral properties to reliably classify the evolutionary stage of low surface brightness, diffuse emission that low frequency observations are revealing around a growing number of radio sources.
Publisher: Oxford University Press (OUP)
Date: 09-2003
Publisher: Springer Berlin Heidelberg
Date: 08-11-2003
DOI: 10.1007/10857580_65
Publisher: EDP Sciences
Date: 10-2018
DOI: 10.1051/0004-6361/201832768
Abstract: We have analyzed the southern sky emission in linear polarization at 2.3 GHz as observed by the S -band Polarization All Sky Survey ( S-PASS ). Our purpose is to study the properties of the diffuse Galactic polarized synchrotron as a contaminant to B -mode observations of the cosmic microwave background (CMB) polarization. We studied the angular distribution of the S-PASS signal at intermediate and high Galactic latitudes by means of the polarization angular power spectra. The power spectra, computed in the multipole interval 20 ≤ ℓ ≤ 1000, show a decay of the spectral litude as a function of multipole for ℓ ≲ 200, typical of the diffuse emission. At smaller angular scales, power spectra are dominated by the radio point source radiation. We find that, at low multipoles, spectra can be approximated by a power law C ℓ EE,BB ∝ ℓ α , with α ≃ −3, and characterized by a B -to- E ratio of about 0.5. We measured the polarized synchrotron spectral energy distribution (SED) in harmonic space, by combining S-PASS power spectra with low frequency WMAP and Planck ones, and by fitting their frequency dependence in six multipole bins, in the range 20 ≤ ℓ ≤ 140. Results show that the recovered SED, in the frequency range 2.3–33 GHz, is compatible with a power law with β s = −3.22 ± 0.08, which appears to be constant over the considered multipole range and in the different Galactic cuts. Combining the S-PASS total polarized intensity maps with those coming from WMAP and Planck we derived a map of the synchrotron spectral index β s at angular resolution of 2° on about 30% of the sky. The recovered β s distribution peaks at the value around −3.2. It exibits an angular power spectrum which can be approximated with a power law C ℓ ∝ ℓ γ with γ ≃ −2.6. We also measured a significant spatial correlation between synchrotron and thermal dust signals, as traced by the Planck 353 GHz channel. This correlation reaches about 40% on the larger angular scales, decaying considerably at the degree scales. Finally, we used the S-PASS maps to assess the polarized synchrotron contamination to CMB observations of the B -modes at higher frequencies. We ided the sky in small patches (with f sky ≃ 1%) and find that, at 90 GHz, the minimal contamination, in the cleanest regions of the sky, is at the level of an equivalent tensor-to-scalar ratio r synch ≃ 10 −3 . Moreover, by combining S-PASS data with Planck 353 GHz observations, we recover a map of the minimum level of total polarized foreground contamination to B -modes, finding that there is no region of the sky, at any frequency, where this contamination lies below equivalent tenor-to-scalar ratio r FG ≃ 10 −3 . This result confirms the importance of observing both high and low frequency foregrounds in CMB B -mode measurements.
Publisher: Springer New York
Date: 2008
Publisher: Oxford University Press (OUP)
Date: 10-01-2019
DOI: 10.1093/MNRAS/STZ092
Publisher: Springer Science and Business Media LLC
Date: 10-09-2022
DOI: 10.1007/S10909-022-02848-Z
Abstract: The MIllimetric Sardinia radio Telescope Receiver based on Array of Lumped elements KIDs, MISTRAL, is a cryogenic W-band (77–103 GH) LEKID camera which will be integrated at the Gregorian focus of the 64 m aperture Sardinia Radio Telescope, in Italy, in Autumn 2022. This instrument, thanks to its high angular resolution ( $$\\sim 13~{\\mathrm{arcsec}}$$ ∼ 13 arcsec ) and the wide instantaneous field of view ( $$\\sim 4~{\\mathrm{arcmin}}$$ ∼ 4 arcmin ), will allow continuum surveys of the mm-wave sky with a variety of scientific targets, spanning from extragalactic astrophysics to solar system science. In this contribution, we will describe the design of the MISTRAL camera, with a particular focus on the optimisation and test of a prototype of the focal plane.
Publisher: EDP Sciences
Date: 29-05-2014
Publisher: Cambridge University Press (CUP)
Date: 2017
DOI: 10.1017/PASA.2017.5
Abstract: The S -band Polarisation All-Sky Survey has observed the entire southern sky using the 64-m Parkes radio telescope at 2.3 GHz with an effective bandwidth of 184 MHz. The surveyed sky area covers all declinations δ ⩽ 0°. To analyse compact sources, the survey data have been re-processed to produce a set of 107 Stokes I maps with 10.75 arcmin resolution and the large scale emission contribution filtered out. In this paper, we use these Stokes I images to create a total intensity southern-sky extragalactic source catalogue at 2.3 GHz. The source catalogue contains 23 389 sources and covers a sky area of 16 600 deg 2 , excluding the Galactic plane for latitudes | b | 10°. Approximately, 8% of catalogued sources are resolved. S -band Polarisation All-Sky Survey source positions are typically accurate to within 35 arcsec. At a flux density of 225 mJy, the S -band Polarisation All-Sky Survey source catalogue is more than 95% complete, and ~ 94% of S -band Polarisation All-Sky Survey sources brighter than 500 mJy beam −1 have a counterpart at lower frequencies.
Publisher: Oxford University Press (OUP)
Date: 04-05-2018
Publisher: EDP Sciences
Date: 12-2017
No related grants have been discovered for Sergio Poppi.