14 research outputs found
Age of submarine debris avalanches and tephrostratigraphy offshore Ischia Island, Tyrrhenian Sea, Italy
We present an "event stratigraphy" framework built for the last 23 cal ka marine record in the southern offshore of Ischia Island based on AMS (14)C dating and tephrostratigraphic analysis of 11 gravity cores. Two collapse events have been recovered in the record: a) the Ischia submarine debris avalanche/debris flow (DA/DF), dated between similar to 3 ka B.P. and 2.4 ka B.P. and possibly between 2.7 ka B.P. and 2.4 ka B.P. (event DF1); b) a former, pre-Holocene, DA/DF older than 23 cal ka B.P. (event DF2). The Ischia DA, with an estimated volume of 1.5 km(3), incorporates thousands of blocks that are still detectable on the sea-floor until 45-50 km far from the island. Our results indicate an age of emplacement younger than previously thought and support the hypothesis that a major catastrophic event occurred when the island was already inhabited by Greek settlers (i.e. after the 7th century BC). Three ash layers have been recognised in the post-DF1 avalanche sequence and correlated with Ischian eruptions occurred between Middle Ages and Roman times. Two tephras recovered in the pre-DF1 succession have been correlated with explosive activity occurred on Ischia and Procida islands from similar to 23 ka to similar to 17.5 ka B.P. The results presented here improve the chronostratigraphic reconstruction of the main eruptive and collapse events that affected Ischia volcano during Late Pleistocene-Holocene and their dispersal at sea The occurrence of at least two major collapsing events in the past 23 kyr confirms the close genetic relationship between gravity failures and Mt. Epomeo uplift. (C) 2010 Elsevier B.V. All rights reserved
DISCOVERY OF CARBON RADIO RECOMBINATION LINES IN M82
Carbon radio recombination lines (RRLs) at low frequencies (<=500 MHz) trace
the cold, diffuse phase of the interstellar medium, which is otherwise
difficult to observe. We present the detection of carbon RRLs in absorption in
M82 with LOFAR in the frequency range of 48-64 MHz. This is the first
extragalactic detection of RRLs from a species other than hydrogen, and below 1
GHz. Since the carbon RRLs are not detected individually, we cross-correlated
the observed spectrum with a template spectrum of carbon RRLs to determine a
radial velocity of 219 +- 9 km/s . Using this radial velocity, we stack 22
carbon-{\alpha} transitions from quantum levels n = 468-508 to achieve an 8.5
sigma detection. The absorption line profile exhibits a narrow feature with
peak optical depth of 0.003 and FWHM of 31 km/s. Closer inspection suggests
that the narrow feature is superimposed on a broad, shallow component. The
total line profile appears to be correlated with the 21 cm H I line profile
reconstructed from H I absorption in the direction of supernova remnants in the
nucleus. The narrow width and centroid velocity of the feature suggests that it
is associated with the nuclear starburst region. It is therefore likely that
the carbon RRLs are associated with cold atomic gas in the direction of the
nucleus of M82.Comment: 6 pages, 5 figures, accepted for publication in ApJ
LOFAR MSSS: Discovery of a 2.56 Mpc giant radio galaxy associated with a disturbed galaxy group
We report on the discovery in the LOFAR Multifrequency Snapshot Sky Survey
(MSSS) of a giant radio galaxy (GRG) with a projected size of
Mpc projected on the sky. It is associated with the galaxy triplet UGC 9555,
within which one is identified as a broad-line galaxy in the Sloan Digital Sky
Survey (SDSS) at a redshift of , and with a
velocity dispersion of km/s. From archival radio observations
we see that this galaxy hosts a compact flat-spectrum radio source, and we
conclude that it is the active galactic nucleus (AGN) responsible for
generating the radio lobes. The radio luminosity distribution of the jets, and
the broad-line classification of the host AGN, indicate this GRG is orientated
well out of the plane of the sky, making its physical size one of the largest
known for any GRG. Analysis of the infrared data suggests that the host is a
lenticular type galaxy with a large stellar mass
(), and a moderate star
formation rate (). Spatially
smoothing the SDSS images shows the system around UGC 9555 to be significantly
disturbed, with a prominent extension to the south-east. Overall, the evidence
suggests this host galaxy has undergone one or more recent moderate merger
events and is also experiencing tidal interactions with surrounding galaxies,
which have caused the star formation and provided the supply of gas to trigger
and fuel the Mpc-scale radio lobes.Comment: Compressed for arXiv, see journal for full resolution image
Definition and management of colorectal polyposis not associated with APC/MUTYH germline pathogenic variants: AIFEG consensus statement
An expert consensus panel convened by the Italian Association for Inherited and Familial Gastrointestinal Tumors (Associazione Italiana per lo Studio della Familiarit\ue0 ed Ereditariet\ue0 dei Tumori Gastrointestinali, AIFEG) reviewed the literature and agreed on a number of position statements regarding the definition and management of polyposis coli without an identified pathogenic mutation on the APC or MUTYH genes, defined in the document as NAMP (non-APC/MUTYH polyposis)