2,080 research outputs found
The Sagittarius Dwarf spheroidal Galaxy Survey (SDGS) II: The stellar content and constraints on the star formation history
A detailed study of the Star Formation History of the Sgr dSph galaxy is
performed through the analysis of the data from the Sagittarius Dwarf Galaxy
Survey (SDGS; Bellazzini, Ferraro & Buonanno 1999). Accurate statistical
decontamination of the SDGS Color - Magnitude diagrams allow us to obtain many
useful constraints on the age and metal content of the Sgr stellar populations
in three different region of the galaxy.
A coarse metallicity distribution of Sgr stars is derived, ranging from
[Fe/H]~ -2.0 to [Fe/H]~ -0.7, the upper limit being somewhat higher in the
central region of the galaxy. A qualitative global fit to all the observed CMD
features is attempted, and a general scheme for the Star Formation History of
the Sgr is derived. According to this scheme, star formation began at very
early time from a low metal content Inter Stellar Medium and lasted for several
Gyr, coupled with progressive chemical enrichment. The Star Formation Rate
(SFR) had a peak from 8 to 10 gyr ago when the mean metallicity was in the
range -1.3<= [Fe/H] <= -0.7. After that maximum, the SFR rapidly decreased and
very low rate star formation took place until ~1-0.5 Gyr ago.Comment: 21 pages, 12 figures, figg. 1,2,3,5,6,10 and 11 provided in lower
resolution format. For full resolution versions see
http://www.bo.astro.it/bap/BAPhome.html Accepted by MNRA
The giant, horizontal and asymptotic branches of galactic globular clusters. I. The catalog, photometric observables and features
A catalog including a set of the most recent Color Magnitude Diagrams (CMDs)
is presented for a sample of 61 Galactic Globular Clusters (GGCs). We used this
data-base to perform an homogeneous systematic analysis of the evolved
sequences (namely, Red Giant Branch (RGB), Horizontal Branch (HB) and
Asymptotic Giant Branch (AGB)). Based on this analysis, we present: (1) a new
procedure to measure the level of the ZAHB (V_ZAHB) and an homogeneous set of
distance moduli obtained adopting the HB as standard candle; (2) an independent
estimate for RGB metallicity indicators and new calibrations of these
parameters in terms of both spectroscopic ([Fe/H]_CG97) and global metallicity
([M/H], including also the alpha-elements enhancement). The set of equations
presented can be used to simultaneously derive a photometric estimate of the
metal abundance and the reddening from the morphology and the location of the
RGB in the (V,B-V)-CMD. (3) the location of the RGB-Bump (in 47 GGCs) and the
AGB-Bump (in 9 GGCs). The dependence of these features on the metallicity is
discussed. We find that by using the latest theoretical models and the new
metallicity scales the earlier discrepancy between theory and observations
(~0.4 mag) completely disappears.Comment: 51 pages, 23 figures, AAS Latex, macro rtrpp4.sty included, accepted
by A
Discriminating between a Stochastic Gravitational Wave Background and Instrument Noise
The detection of a stochastic background of gravitational waves could
significantly impact our understanding of the physical processes that shaped
the early Universe. The challenge lies in separating the cosmological signal
from other stochastic processes such as instrument noise and astrophysical
foregrounds. One approach is to build two or more detectors and cross correlate
their output, thereby enhancing the common gravitational wave signal relative
to the uncorrelated instrument noise. When only one detector is available, as
will likely be the case with the Laser Interferometer Space Antenna (LISA),
alternative analysis techniques must be developed. Here we show that models of
the noise and signal transfer functions can be used to tease apart the
gravitational and instrument noise contributions. We discuss the role of
gravitational wave insensitive "null channels" formed from particular
combinations of the time delay interferometry, and derive a new combination
that maintains this insensitivity for unequal arm length detectors. We show
that, in the absence of astrophysical foregrounds, LISA could detect signals
with energy densities as low as with just
one month of data. We describe an end-to-end Bayesian analysis pipeline that is
able to search for, characterize and assign confidence levels for the detection
of a stochastic gravitational wave background, and demonstrate the
effectiveness of this approach using simulated data from the third round of
Mock LISA Data Challenges.Comment: 10 Pages, 10 Figure
“FROM WASTE TO TASTE”: Exploring The Cultural Significance of Grapevine Leaves in Reggio Emilia to Foster Sustainability and Cultural Understanding
Reggio Emilia, Italy, has a rich history of wine production dating back to the 15th century. However, the global wine industry discards around 42 million tonnes of grapevine cuttings each year by burying or burning them on farms, leading to wasteful practices (Ellis, 2020). This inspired two PhD students with diverse backgrounds to raise awareness of the cultural significance of grapevine leaves in various communities in Reggio Emilia. They argue that grapevine leaves are not only a byproduct of winemaking but also an essential ingredient in many cultures, including immigrant communities, and how this practice aligns with food sustainability and cultural identity. The study draws on the Reggio Emilia Approach to food education, which highlights the importance of food as a medium for learning and explores the power of dialogue and negotiation in constructing meaning. Mealtimes, according to educators in Reggio Emilia, are moments for socializing, expressing cultural identities, and learning new skills and knowledge ((Edwards, Gandini, & Forman, 1998; Rinaldi, 2005) The researchers used autoethnography to demonstrate how grape leaves are used and their cultural significance in different contexts. They interviewed local farmers and communities and held workshops on making Dolma, a dish enjoyed by many nationalities, using grapevine leaves (Dogan et al., 2017). The study emphasizes the power of dialogue and negotiation in constructing meaning and recognizes the interconnectedness between plants and humans in our food experiences and cultural understanding. The findings have significant implications for food education, sustainable practices, and cultural significance in Reggio Emilia and other communities globally (Ozturk, 2022), highlighting the importance of collaboration between individuals from diverse backgrounds in promoting sustainable practices and fostering cultural understanding
Optical noise correlations and beating the standard quantum limit in advanced gravitational-wave detectors
The uncertainty principle, applied naively to the test masses of a
laser-interferometer gravitational-wave detector, produces a Standard Quantum
Limit (SQL) on the interferometer's sensitivity. It has long been thought that
beating this SQL would require a radical redesign of interferometers. However,
we show that LIGO-II interferometers, currently planned for 2006, can beat the
SQL by as much as a factor two over a bandwidth \Delta f \sim f, if their
thermal noise can be pushed low enough. This is due to dynamical correlations
between photon shot noise and radiation-pressure noise, produced by the LIGO-II
signal-recycling mirror.Comment: 12 pages, 2 figures; minor changes, some references adde
Distance and reddening of the Local Group dwarf irregular galaxy NGC 6822
On the basis of a new photometric analysis of the Local Group dwarf irregular
galaxy NCG 6822 based on observations obtained with the Advanced Camera for
Surveys onboard the Hubble Space Telescope, we have obtained a new estimate of
the extinction of two fields located in the southeast region of the galaxy.
Because of significant differences in the distance estimates to NGC 6822
available in literature, we decided to provide an independent determination of
the distance to this galaxy based on an updated and self-consistent theoretical
calibration of the tip of the red giant branch brightness. As a result we newly
determined the distance to NGC 6822 to be equal to , and compared our measurement with the most recent determinations of this
distance.Comment: 5 pages, 5 figures, Astronomy & Astrophysics (Research Note), in
press (proof correction included
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