360 research outputs found
Star-forming Clumps in Local Luminous Infrared Galaxies
We present HST narrowband near-infrared imaging of Paα and Paβ emission of 48 local luminous infrared galaxies (LIRGs) from the Great Observatories All-Sky LIRG Survey. These data allow us to measure the properties of 810 spatially resolved star-forming regions (59 nuclei and 751 extranuclear clumps) and directly compare their properties to those found in both local and high-redshift star-forming galaxies. We find that in LIRGs the star-forming clumps have radii ranging from ~90 to 900 pc and star formation rates (SFRs) of ~1 × 10⁻³ to 10 M⊙ yr⁻¹, with median values for extranuclear clumps of 170 pc and 0.03 M⊙ yr⁻¹. The detected star-forming clumps are young, with a median stellar age of 8.7 Myr, and have a median stellar mass of 5 × 10⁵ M ⊙. The SFRs span the range of those found in normal local star-forming galaxies to those found in high-redshift star-forming galaxies at z = 1–3. The luminosity function of the LIRG clumps has a flatter slope than found in lower-luminosity, star-forming galaxies, indicating a relative excess of luminous star-forming clumps. In order to predict the possible range of star-forming histories and gas fractions, we compare the star-forming clumps to those measured in the MassiveFIRE high-resolution cosmological simulation. The star-forming clumps in MassiveFIRE cover the same range of SFRs and sizes found in the local LIRGs and have total gas fractions that extend from 10% to 90%. If local LIRGs are similar to these simulated galaxies, we expect that future observations with ALMA will find a large range of gas fractions, and corresponding star formation efficiencies, among the star-forming clumps in LIRGs
No evidence of sars-cov-2 circulation in rome (Italy) during the pre-pandemic period. Results of a retrospective surveillance
In March 2020, the World Health Organization (WHO) declared that the COVID-19 outbreak recorded over the previous months could be characterized as a pandemic. The first known Italian SARS-CoV-2 positive case was reported on 21 February. In some countries, cases of suspected “COVID-19-like pneumonia” had been reported earlier than those officially accepted by health authorities. This has led many investigators to check preserved biological or environmental samples to see whether the virus was detectable on dates prior to those officially stated. With regard to Italy, the results of a microbiological screening in sewage samples collected between the end of February and the beginning of April 2020 from wastewaters in Milan (Northern Italy) and Rome (Central Italy) showed presence of SARS-CoV-2. In the present study, we evaluated, by means of a standardized diagnostic method, the SARS-CoV-2 infection prevalence amongst patients affected by severe acute respiratory syndrome (SARI) in an academic hospital located in Central Italy during the period of 1 November 2019–1 March 2020. Overall, the number of emergency room (ER) visits during the investigated period was 13,843. Of these, 1208 had an influenza-like syndrome, but only 166 matched the definition of SARI as stated in the study protocol. A total of 52 SARI cases were laboratory confirmed as influenza: 26 as a type B virus, 25 as a type A, and 1 as both viruses. Although about 17% of the total sample had laboratory or radiological data compatible with COVID-19, all the nasopharyngeal swabs stored underwent SARS-CoV-2 RT-PCR and tested negative. Based on our result, it is confirmed that the COVID-19 pandemic spread did not start prior to the “official” onset in central Italy. Routine monitoring of SARI causative agents at the local level is critical for reporting epidemiologic and etiologic trends that may differ from one country to another and also among different influenza seasons. This has a practical impact on prevention and control strategies
Recent Borexino results and prospects for the near future
The Borexino experiment, located in the Gran Sasso National Laboratory, is an
organic liquid scintillator detector conceived for the real time spectroscopy
of low energy solar neutrinos. The data taking campaign phase I (2007 - 2010)
has allowed the first independent measurements of 7Be, 8B and pep fluxes as
well as the first measurement of anti-neutrinos from the earth. After a
purification of the scintillator, Borexino is now in phase II since 2011. We
review here the recent results achieved during 2013, concerning the seasonal
modulation in the 7Be signal, the study of cosmogenic backgrounds and the
updated measurement of geo-neutrinos. We also review the upcoming measurements
from phase II data (pp, pep, CNO) and the project SOX devoted to the study of
sterile neutrinos via the use of a 51Cr neutrino source and a 144Ce-144Pr
antineutrino source placed in close proximity of the active material.Comment: 8 pages, 11 figures. To be published as proceedings of Rencontres de
Moriond EW 201
Recommended from our members
Solar neutrino with Borexino: results and perspectives
Borexino is a unique detector able to perform measurement of solar neutrinos
fluxes in the energy region around 1 MeV or below due to its low level of
radioactive background. It was constructed at the LNGS underground laboratory
with a goal of solar Be neutrino flux measurement with 5\% precision. The
goal has been successfully achieved marking the end of the first stage of the
experiment. A number of other important measurements of solar neutrino fluxes
have been performed during the first stage. Recently the collaboration
conducted successful liquid scintillator repurification campaign aiming to
reduce main contaminants in the sub-MeV energy range. With the new levels of
radiopurity Borexino can improve existing and challenge a number of new
measurements including: improvement of the results on the Solar and terrestrial
neutrino fluxes measurements; measurement of pp and CNO solar neutrino fluxes;
search for non-standard interactions of neutrino; study of the neutrino
oscillations on the short baseline with an artificial neutrino source (search
for sterile neutrino) in context of SOX project.Comment: 15 pages, 4 figure
Recommended from our members
Measurement of geo-neutrinos from 1353 days of Borexino
We present a measurement of the geo--neutrino signal obtained from 1353 days
of data with the Borexino detector at Laboratori Nazionali del Gran Sasso in
Italy. With a fiducial exposure of (3.69 0.16) proton
year after all selection cuts and background subtraction, we detected
(14.3 4.4) geo-neutrino events assuming a fixed chondritic mass Th/U
ratio of 3.9. This corresponds to a geo-neutrino signal = (38.8
12.0) TNU with just a 6 probability for a null geo-neutrino
measurement. With U and Th left as free parameters in the fit, the relative
signals are = (10.6 12.7) TNU and =
(26.5 19.5) TNU. Borexino data alone are compatible with a mantle
geo--neutrino signal of (15.4 12.3) TNU, while a combined analysis with
the KamLAND data allows to extract a mantle signal of (14.1 8.1) TNU. Our
measurement of a reactor anti--neutrino signal =
84.5 TNU is in agreement with expectations in the presence of
neutrino oscillations.Comment: 9 pages, 6 figure
Low-energy (anti)neutrino physics with Borexino: Neutrinos from the primary proton-proton fusion process in the Sun
The Sun is fueled by a series of nuclear reactions that produce the energy
that makes it shine. The primary reaction is the fusion of two protons into a
deuteron, a positron and a neutrino. These neutrinos constitute the vast
majority of neutrinos reaching Earth, providing us with key information about
what goes on at the core of our star. Several experiments have now confirmed
the observation of neutrino oscillations by detecting neutrinos from secondary
nuclear processes in the Sun; this is the first direct spectral measurement of
the neutrinos from the keystone proton-proton fusion. This observation is a
crucial step towards the completion of the spectroscopy of pp-chain neutrinos,
as well as further validation of the LMA-MSW model of neutrino oscillations.Comment: Proceedings from NOW (Neutrino Oscillation Workshop) 201
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