277 research outputs found
Spatially resolved kinematics, galactic wind, and quenching of star formation in the luminous infrared galaxy IRAS F11506-3851
We present a multi-wavelength integral field spectroscopic study of the low-z
LIRG IRAS F11506-3851, on the basis of VIMOS and SINFONI (ESO-VLT)
observations. The morphology and the 2D kinematics of the gaseous (neutral and
ionized) and stellar components have been mapped using the NaD doublet, the
H line, and the near-IR CO(2-0) and CO(3-1) bands. The kinematics of
the ionized gas and the stars are dominated by rotation, with large observed
velocity amplitudes and centrally peaked velocity dispersion maps. The stars
lag behind the warm gas and represent a dynamically hotter system, as indicated
by the observed dynamical ratios. Thanks to these IFS data we have disentangled
the contribution of the stars and the ISM to the NaD feature, finding that it
is dominated by the absorption of neutral gas clouds in the ISM. The neutral
gas 2D kinematics shows a complex structure dominated by two components. On the
one hand, the thick slowly rotating disk lags significantly compared to the
ionized gas and the stars, with an irregular and off-center velocity dispersion
map. On the other hand, a kpc-scale neutral gas outflow is observed along the
semi-minor axis of the galaxy, as revealed by large blueshifted velocities
(30-154 km/s). We derive an outflowing mass rate in neutral gas of about 48
/yr. Although this implies a global mass loading factor of
1.4, the 2D distribution of the ongoing SF suggests a much larger value of mass
loading factor associated with the inner regions (R200 pc), where the
current SF represents only 3 percent of the total. All together these results
strongly suggest that we are witnessing (nuclear) quenching due to SF feedback
in IRAS F11506-3851. However, the relatively large mass of molecular gas
detected in the nuclear region via the H2 1-0 S(1) line suggests that further
episodes of SF may take place again
Lexicality, frequency and stress assignment effects in bilingual children reading Italian as a second language
In Italian, developing readers exhibit lexicality and frequency effects, and are sensitive to the distributional properties of the language. But how do bilingual children with different ages of first L2 (Italian) exposure and L2 vocabulary sizes read L2 words and pseudowords? Two reading aloud experiments investigated lexicality, frequency and stress assignment effects in fourth- and fifth-grade bilinguals and monolinguals. Naming latencies and pronunciation accuracy were analyzed. In Experiment 1, effects of lexicality and frequency and between-group differences emerged. In Experiment 2, the word frequency effect was confirmed. Late bilinguals, characterized by a smaller L2 vocabulary size, were less accurate than early bilinguals and monolinguals in assigning non-dominant stress. As with monolinguals, lexical information seems to be employed when reading Italian as a second language. Furthermore, bilingual readers are sensitive to the distributional properties of the language. Stress assignment is affected by the L2 lexicon size of second-language learners
Uncertainties in gas kinematics arising from stellar continuum modelling in integral field spectroscopy data: the case of NGC2906 observed with MUSE/VLT
We study how the use of several stellar subtraction methods and line fitting
approaches can affect the derivation of the main kinematic parameters (velocity
and velocity dispersion fields) of the ionized gas component. The target of
this work is the nearby galaxy NGC 2906, observed with the MUSE instrument at
Very Large Telescope. A sample of twelve spectra is selected from the inner
(nucleus) and outer (spiral arms) regions, characterized by different
ionization mechanisms. We compare three different methods to subtract the
stellar continuum (FIT3D, STARLIGHT and pPXF), combined with one of the
following stellar libraries: MILES, STELIB and GRANADA+MILES. The choice of the
stellar subtraction method is the most important ingredient affecting the
derivation of the gas kinematics, followed by the choice of the stellar library
and by the line fitting approach. In our data, typical uncertainties in the
observed wavelength and width of the H\alpha and [NII] lines are of the order
of _rms \sim 0.1\AA\ and _rms \sim 0.2\AA\ (\sim 5
and 10km/s, respectively). The results obtained from the [NII] line seem to be
slightly more robust, as it is less affected by stellar absorption than
H\alpha. All methods considered yield statistically consistent measurements
once a mean systemic contribution
\Delta\bar\lambda=\Delta\bar\sigma=0.2xDelta_{MUSE} is added in quadrature to
the line fitting errors, where \Delta_{MUSE} = 1.1\AA\ \sim 50 km/s denotes the
instrumental resolution of the MUSE spectra. Although the subtraction of the
stellar continuum is critical in order to recover line fluxes, any method
(including none) can be used in order to measure the gas kinematics, as long as
an additional component of 0.2 x Delta_MUSE is added to the error budget.Comment: 20 pages, 14 figure
Impact and costs of proposed scenarios for power sector decarbonisation: An Italian case study
In the face of ever more ambitious global energy challenges, the European Union has set striving climate targets for 2030, planning to increase renewable energy penetration in the electricity generation as a key measure towards a clean energy transition. To respond to the challenge of keeping the increase in power sector costs, that inevitably arises when a profound reconfiguration of the electricity generation sector is expected, to the lowest possible, this paper aims to quantify the economic burden associated with the reduction of direct CO2 emissions through a comparative assessment of various alternatives proposed for 2030 ranked in terms of their cost-effectiveness. A sensitivity analysis is also applied to the main economic and energy parameters that make up CO2 mitigation costs to include those uncertainties that characterise future projections. The impact of electricity generation shares on CO2 mitigation costs is assessed thus providing a basis for the definition of alternative configurations for the Italian electricity sector capable to achieve the desired environmental performance with a limited economic impact. Finally, results reveal that those scenarios based largely on natural gas and solar source are characterized by high mitigation costs, while energy efficiency is essential for a virtuous and clean electricity sector along with the use of all available sources in appropriate shares, both renewable and non-renewable, to pursue the highest environmental objectives in a cost-effective manner. Although related to the Italian case, the methodology provided in this study can be applied to any other electricity sector to ultimately evaluate the economic burden arising from possible different configurations
Physics of ULIRGs with MUSE and ALMA: The PUMA project: I. Properties of the survey and first MUSE data results
Ultraluminous infrared galaxies (ULIRGs) are characterised by extreme
starburst (SB) and AGN activity, and are therefore ideal laboratories for
studying the outflow phenomena. We have recently started a project called
Physics of ULIRGs with MUSE and ALMA (PUMA), which is a survey of 25 nearby (z
< 0.165) ULIRGs observed with the integral field spectrograph MUSE and the
interferometer ALMA. This sample includes systems with both AGN and SB nuclear
activity in the pre- and post-coalescence phases of major mergers. The main
goals of the project are to study the prevalence of multi-phase outflows as a
function of the galaxy properties, to constrain the driving mechanisms of the
outflows (e.g. distinguish between SB and AGN winds), and to identify feedback
effects on the host galaxy. In this first paper, we present details on the
sample selection, MUSE observations, and derive first data products. MUSE data
were analysed to study the dynamical status of each of the 21 ULIRGs observed
so far, taking the stellar kinematics and the morphological properties inferred
from MUSE narrow-band images into account. We also located the ULIRG nuclei,
using near-IR (HST) and mm (ALMA) data, and studied their optical spectra to
infer the ionisation state through BPT diagnostics, and outflows in both
ionised and neutral gas. We show that the morphological and stellar kinematic
classifications are consistent: post-coalescence systems are more likely
associated with ordered motions, while interacting (binary) systems are
dominated by non-ordered and streaming motions. We also find broad and
asymmetric [OIII] and NaID profiles in almost all nuclear spectra, with line
widths in the range 300-2000 km/s, possibly associated with AGN- and SB-driven
winds. This result reinforces previous findings that indicated that outflows
are ubiquitous during the pre- and post-coalescence phases of major mergers.ERC
STF
MUSE view of Arp220: Kpc-scale multi-phase outflow and evidence for positive feedback
Arp220 is the nearest and prototypical ULIRG, and shows evidence of pc-scale
molecular outflows in its nuclear regions and strongly perturbed ionised gas
kinematics on kpc scales. It is therefore the ideal system for investigating
outflows and feedback phenomena in details. We investigate the feedback effects
on the Arp220 ISM, deriving a detailed picture of the atomic gas in terms of
physical and kinematic properties, with a spatial resolution never obtained
before (0.56", i.e. ~ 210 pc). We use optical IFS observations from VLT/MUSE-AO
to obtain spatially resolved stellar and gas kinematics, for both ionised ([N
II]6583) and neutral (Na ID5891,96) components; we also derive dust
attenuation, electron density, ionisation conditions and hydrogen column
density maps to characterise the ISM properties. Arp220 kinematics reveal the
presence of a disturbed, kpc-scale disk in the innermost nuclear regions, and
highly perturbed, multi-phase (neutral and ionised) gas along the minor-axis of
the disk, which we interpret as a galactic-scale outflow emerging from the
Arp220 eastern nucleus. This outflow involves velocities up to ~ 1000 km/s at
galactocentric distances of ~ 5 kpc, and has a mass rate of ~ 50 Msun/yr, and
kinetic and momentum power of ~ 1e43 erg/s and ~ 1e35 dyne, respectively. The
inferred energetics do not allow us to distinguish the origin of the outflows,
i.e. whether they are AGN-driven or starburst-driven. We also present evidence
for enhanced star formation at the edges of - and within - the outflow, with a
star formation rate SFR ~ 5 Msun/yr (i.e. ~ 2% of the total SFR). Our findings
suggest the presence of powerful winds in Arp220: they might be capable of
removing or heating large amounts of gas from the host ("negative feedback"),
but could be also responsible for triggering star formation ("positive
feedback").STFC
ER
Properties of the multiphase outflows in local (ultra)luminous infrared galaxies
Galactic outflows are known to consist of several gas phases, however, so far
the connection between these multiple phases has been investigated little and
only in a few objects. In this paper, we analyse MUSE/VLT data of 26 local
(U)LIRGs and study their ionised and neutral atomic phases. We also include
objects from the literature to obtain a total sample of 31 galaxies with
spatially resolved multi-phase outflow information. We find that the ionized
phase of the outflows has on average an electron density three times higher
than the disc ( 150 cm vs
500 cm), suggesting that cloud compression in the outflow is more
important that cloud dissipation. We find that the difference in extinction
between outflow and disc correlates with the outflow gas mass. Together with
the analysis of the outflow velocities, this suggests that at least some of the
outflows are associated with the ejection of dusty clouds from the disc. The
presence of dust in outflows is relevant for potential formation of molecules
inside them. We combine our data with millimetre data to investigate the
molecular phase. We find that the molecular phase accounts for more than 60
of the total mass outflow rate in most objects and this fraction is higher
in AGN-dominated systems. The neutral atomic phase contributes of the order of
10 , while the ionized phase is negligible. The ionized-to-molecular mass
outflow rate declines slightly with AGN luminosity, although with a large
scatter.STFC
ER
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