146 research outputs found
The first record in Italy of Trichogramma cordubense Vargas & Cabello 1985 (Hymenoptera: Trichogrammatidae) emerging from the eggs of Lobesia botrana (Denis & Schiffermüller, 1775) (Lepidoptera: Tortricidae)
This study investigated the egg parasitoids of Lobesia botrana (Denis & Schiffermüller, 1775) feeding on Daphne gnidium L. (Malvales, Thymelaeaceae) in the San Rossore-Migliarino-Massaciuccoli Nature Reserve (Tuscany, Italy). Four species of egg parasitoids of the genus Trichogramma spp. were obtained. The parasitization rate gradually increased over the season, reaching its maximum level in September 2015, with a percentage of parasitized eggs close to 55 %. Three of the species obtained were already known as L. botrana parasitoids, whereas the finding of Trichogramma cordubense Vargas & Cabello, 1985 represents the first recording in Italy, as well as the first report of this species among the natural enemies of L. botrana
The AGN fuelling/feedback cycle in nearby radio galaxies - V. The cold atomic gas of NGC 3100 and its group
We present Australia Compact Telescope Array (ATCA) 21-cm observations of the
nearby low-excitation radio galaxy (LERG) NGC 3100. This is the brightest
galaxy of a loose group and hosts a young ( Myr) radio source. The ATCA
observations reveal for the first time the presence of neutral hydrogen (HI)
gas in absorption in the centre of this radio galaxy, and in emission in two
low-mass galaxies of the group and in a diffuse dark cloud in the proximity of
NGC 3100. The sensitivity to low-column density gas (
cm) allows us to reveal asymmetries in the periphery of most the
HI-detected galaxies, suggesting that tidal interactions may be on-going. The
diffuse cloud does not show a stellar counterpart down to mag/arcsec
and could be the remnant of these interactions. The analysis of the HI
absorption complex in NGC 3100 indicates that the atomic phase of the hydrogen
is distributed as its molecular phase (observed at arcsecond resolution through
several carbon monoxide emission lines). We suggest that the interactions
occurring within the group are causing turbulent cold gas clouds in the
intra-group medium to be slowly accreted towards the centre of NGC 3100. This
caused the recent formation of the cold circum-nuclear disk which is likely
sustaining the young nuclear activity.Comment: 10 pages, 7 figures; submitted to Astronomy & Astrophysic
The star formation histories of galaxies in different stages of pre-processing in the Fornax A group
We study the recent star formation histories of ten galaxies in the Fornax A
galaxy group, on the outskirts of the Fornax cluster. The group galaxies are
gas-rich, and their neutral atomic hydrogen (HI) was studied in detail with
observations from the MeerKAT telescope. This allowed them to be classified
into different stages of pre-processing (early, ongoing, advanced). We use
long-slit spectra obtained with the South African Large Telescope (SALT) to
analyse stellar population indicators to constrain quenching timescales and to
compare these to the HI gas content of the galaxies. The H equivalent
width, EW(H), suggest that the pre-processing stage is closely related
to the recent (< 10 Myr) specific Star Formation Rate (sSFR). The early-stage
galaxy (NGC 1326B) is not yet quenched in its outer parts, while the
ongoing-stage galaxies mostly have a distributed population of very young
stars, though less so in their outer parts. The galaxies in the advanced stage
of pre-processing show very low recent sSFR in the outer parts. Our results
suggest that NGC 1326B, FCC 35 and FCC 46 underwent significantly different
histories from secular evolution during the last Gyr. The fact that most
galaxies are on the secular evolution sequence implies that pre-processing has
a negligible effect on these galaxies compared to secular evolution. We find
EW(H) to be a useful tool for classifying the stage of pre-processing
in group galaxies. The recent sSFR and HI morphology show that galaxies in the
Fornax A vicinity are pre-processing from the outside in.Comment: 17 pages, accepted for publication in MNRA
The MeerKAT Fornax Survey -- II. The rapid removal of HI from dwarf galaxies in the Fornax cluster
We present MeerKAT Fornax Survey atomic hydrogen (HI) observations of the
dwarf galaxies located in the central ~2.5 x 4 deg of the Fornax galaxy
cluster. The HI images presented in this work have a column density
sensitivity between 2.7 and 50 x 10 cm over 25 km s for
spatial resolution between 4 and 1 kpc. We are able to detect an impressive MHI
= 5 x 10 Msun 3 point source with a line width of 50 km s
at a distance of 20 Mpc. We detect HI in 17 out of the 304 dwarfs in our field
-- 14 out of the 36 late type dwarfs (LTDs), and 3 of the 268 early type dwarfs
(ETDs). The HI-detected LTDs have likely just joined the cluster and are on
their first infall as they are located at large clustocentric radii, with
comparable MHI and mean stellar surface brightness at fixed luminosity as blue,
star-forming LTDs in the field. The HI-detected ETDs have likely been in the
cluster longer than the LTDs and acquired their HI through a recent merger or
accretion from nearby HI. Eight of the HI-detected LTDs host irregular or
asymmetric HI emission and disturbed or lopsided stellar emission. There are
two clear cases of ram-pressure shaping the HI, with the LTDs displaying
compressed HI on the side closest to the cluster centre and a one-sided,
starless tail pointing away from the cluster centre. The HI-detected dwarfs
avoid the most massive potentials, consistent with massive galaxies playing an
active role in the removal of HI. We create a simple toy model to quantify the
timescale of HI stripping in the cluster. We find that a MHI = 10 Msun
dwarf will be stripped in ~ 240 Myr. The model is consistent with our
observations, where low mass LTDs are directly stripped of their HI from a
single encounter and more massive LTDs can harbour a disturbed HI morphology
due to longer times or multiple encounters being required to fully strip their
HI.Comment: Accepted in Astronomy & Astrophysics. 21 pages, 10 figures. Data
available at the MeerKAT Fornax Survey website
https://sites.google.com/inaf.it/meerkatfornaxsurve
A blind ATCA HI survey of the Fornax galaxy cluster:Properties of the HI detections
We present the first interferometric blind HI survey of the Fornax galaxy cluster, which covers an area of 15 deg2 out to the cluster virial radius. The survey has a spatial and velocity resolution of 67″ × 95″(∼6 × 9 kpc at the Fornax cluster distance of 20 Mpc) and 6.6 km s−1 and a 3σ sensitivity of NHI ∼ 2 × 1019 cm−2 and MHI ∼ 2 × 107 M⊙, respectively. We detect 16 galaxies out of roughly 200 spectroscopically confirmed Fornax cluster members. The detections cover about three orders of magnitude in HI mass, from 8 × 106 to 1.5 × 1010 M⊙. They avoid the central, virialised region of the cluster both on the sky and in projected phase-space, showing that they are recent arrivals and that, in Fornax, HI is lost within a crossing time, ∼2 Gyr. Half of these galaxies exhibit a disturbed HI morphology, including several cases of asymmetries, tails, offsets between HI and optical centres, and a case of a truncated HI disc. This suggests that these recent arrivals have been interacting with other galaxies, the large-scale potential or the intergalactic medium, within or on their way to Fornax. As a whole, our Fornax HI detections are HI-poorer and form stars at a lower rate than non-cluster galaxies in the same M⋆ range. This is particularly evident at M⋆  ≲  109 M⊙, indicating that low mass galaxies are more strongly affected throughout their infall towards the cluster. The MHI/M⋆ ratio of Fornax galaxies is comparable to that in the Virgo cluster. At fixed M⋆, our HI detections follow the non-cluster relation between MHI and the star formation rate, and we argue that this implies that thus far they have lost their HI on a timescale ≳1−2 Gyr. Deeper inside the cluster HI removal is likely to proceed faster, as confirmed by a population of HI-undetected but H2-detected star-forming galaxies. Overall, based on ALMA data, we find a large scatter in H2-to-HI mass ratio, with several galaxies showing an unusually high ratio that is probably caused by faster HI removal. Finally, we identify an HI-rich subgroup of possible interacting galaxies dominated by NGC 1365, where pre-processing is likely to have taken place
4E assessment of power generation systems for a mobile house in emergency condition using solar energy: a case study
In this study, a solar parabolic trough concentrator (PTC) was evaluated as a heat source of a power generation system based on energy (E1), exergy (E2), environmental (E3), and economic (E4) analyses. Various configurations of power generation systems were investigated, including the solar SRC (SRC) and solar ORC (ORC). Water and R113 were used as heat transfer fluids of SRC and ORC system, respectively. It should be mentioned that the proposed solar systems were evaluated for providing the required power of a mobile house in an emergency condition such as an earthquake that was happened in Kermanshah, Iran, in 2016 with many homeless people. The PTC system was optically and thermally investigated based on sensitivity analysis. The optimized PTC system was assumed as a heat source of the RC with two various configurations for power generation. Then, the solar RC systems were investigated based on 4E analyses for providing the power of the mobile house based on various numbers of solar RC units. It was concluded that the solar SRC system could be recommended for achieving the highest 4E performance. The highest value of its energy efficiency was found at 24.60% and of his exergy at 26.37%. On the other hand, the ORC system has energy and exergy efficiencies at 17.64% and 18.91%, respectively, which are significantly lower than the efficiencies of the SRC system. The optimum heat source temperature for the SRC system is found at 650 K, while for the ORC system at 499 K. Moreover, the best economic performance was found with the SRC system with a payback period of 7.47 years. Finally, the CO2 mitigated per annum (φCO2) was estimated at 5.29 (tones year−1), and the carbon credit (ZCO2) was calculated equal to 76.71 ($ year−1)
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