826 research outputs found
Cluster and field elliptical galaxies at z~1.3. The marginal role of the environment and the relevance of the galaxy central regions
We compared the properties of 56 elliptical galaxies selected from three
clusters at with those of field galaxies in the GOODS-S (~30),
COSMOS (~180) and CANDELS (~220) fields. We studied the relationships among
effective radius, surface brightness, stellar mass, stellar mass density
and central mass density within 1 kpc radius. We
find that cluster ellipticals do not differ from field ellipticals: they share
the same structural parameters at fixed mass and the same scaling relations. On
the other hand, the population of field ellipticals at shows a
significant lack of massive ( M) and large (R kpc) ellipticals with respect to the cluster. Nonetheless, at
M, the two populations are similar. The size-mass
relation of ellipticals at z~1.3 defines two different regimes, above and below
a transition mass M: at lower masses the
relation is nearly flat (R), the mean radius is
constant at ~1 kpc and while, at larger masses,
the relation is R. The transition mass marks the
mass at which galaxies reach the maximum . Also the
-mass relation follows two different regimes,
, defining a transition mass
density M pc. The mass density
does not correlate with mass, dense/compact galaxies can be
assembled over a wide mass regime, independently of the environment. The
central mass density, , besides to be correlated with the mass,
is correlated to the age of the stellar population: the higher the central
stellar mass density, the higher the mass, the older the age of the stellar
population. [Abridged]Comment: Accepted for publication in A&A; 20 pages, 13 figures (replaced to
match the A&A version
Lower mass normalization of the stellar initial mass function for dense massive early-type galaxies at z ~ 1.4
This paper aims at understanding if the normalization of the stellar initial
mass function (IMF) of massive early-type galaxies (ETGs) varies with cosmic
time and/or with mean stellar mass density Sigma (M*/2\pi Re^2). For this
purpose we collected a sample of 18 dense (Sigma>2500 M_sun/pc^2) ETGs at
1.2<z<1.6 with available velocity dispersion sigma_e. We have constrained their
mass-normalization by comparing their true stellar masses (M_true) derived
through virial theorem, hence IMF independent, with those inferred through the
fit of the photometry assuming a reference IMF (M_ref). Adopting the virial
estimator as proxy of the true stellar mass, we have assumed for these ETGs
zero dark matter (DM). However, dynamical models and numerical simulations of
galaxy evolution have shown that the DM fraction within Re in dense high-z ETGs
is negligible. We have considered the possible bias of virial theorem in
recovering the total masses and have shown that for dense ETGs the virial
masses are in agreement with those derived through more sophisticated dynamical
models. The variation of the parameter Gamma = M_true/M_ref with sigma_e shows
that, on average, dense ETGs at = 1.4 follow the same IMF-sigma_e trend of
typical local ETGs, but with a lower mass-normalization. Nonetheless, once the
IMF-sigma_e trend we have found for high-z dense ETGs is compared with that of
local ETGs with similar Sigma and sigma_e, they turn out to be consistent. The
similarity between the IMF-sigma_e trends of dense high-z and low-z ETGs over 9
Gyr of evolution and their lower mass-normalization with respect to the mean
value of local ETGs suggest that, independently on formation redshift, the
physical conditions characterizing the formation of a dense spheroid lead to a
mass spectrum of new formed stars with an higher ratio of high- to low-mass
stars with respect to the IMF of normal local ETGs.Comment: 9 pages, 4 figures, accepted for pubblication in A&A, updated to
match final journal versio
Age, metallicity and star formation history of spheroidal galaxies in cluster at z~1.2
We present the analysis, based on spectra collected at the Large Binocular
Telescope, of the stellar populations in seven spheroidal galaxies in the
cluster XLSSJ0223 at 1.22. The aim is to constrain the epoch of their
formation and their star formation history. Using absorption line strenghts and
full spectral fitting, we derive for the stellar populations of the seven
spheroids a median age =2.40.6 Gyr, corresponding to a median
formation redshift $\sim2.6_{-0.5}^{+0.7}$ (lookback time =
11$_{-1.0}^{+0.6}$ Gyr). We find a significant scatter in age, showing that
massive spheroids, at least in our targeted cluster, are not coeval. The median
metallicity is [Z/H]=0.09$\pm$0.16, as for early-types in clusters at
0$<z<<\sigma_e_{dyn}\Sigma_e_{dyn}\Sigma_e_{dyn}\Sigma_ez\sim1.3$, i.e.
more massive spheroids are more metal rich, have lower stellar mass density and
tend to be older than lower-mass galaxies.Comment: 16 pages, 6 figures, 6 tables, published on MNRA
The population of early-type galaxies: how it evolves with time and how it differs from passive and late-type galaxies
The aim of our analysis is twofold. On the one hand we are interested in
addressing whether a sample of ETGs morphologically selected differs from a
sample of passive galaxies in terms of galaxy statistics. On the other hand we
study how the relative abundance of galaxies, the number density and the
stellar mass density for different morphological types change over the redshift
range 0.6<z<2.5. From the 1302 galaxies brighter than Ks=22 selected from the
GOODS-MUSIC catalogue, we classified the ETGs on the basis of their morphology
and the passive galaxies on the basis of their sSFR. We proved how the
definition of passive galaxy depends on the IMF adopted in the models and on
the assumed sSFR threshold. We find that ETGs cannot be distinguished from the
other morphological classes on the basis of their low sSFR, irrespective of the
IMF adopted in the models. Using the sample of 1302 galaxies morphologically
classified into spheroidal galaxies (ETGs) and not spheroidal galaxies (LTGs),
we find that their fractions are constant over the redshift range 0.6<z<2.5
(20-30% ETGs vs 70-80% LTGs). However, at z<1 these fractions change among the
population of the most massive (M*>=10^(11) M_sol) galaxies, with the fraction
of massive ETGs rising up to 40% and the fraction of massive LTGs decreasing
down to 60%. Moreover, we find that the number density and the stellar mass
density of the whole population of massive galaxies increase almost by a factor
of ~10 between 0.6<z<2.5, with a faster increase of these densities for the
ETGs than for the LTGs. Finally, we find that the number density of the
highest-mass galaxies (M*>3-4x10^(11) M_sol) both ETGs and LTGs do not increase
since z~2.5, contrary to the lower mass galaxies. This suggests that the
population of the most massive galaxies formed at z>2.5-3 and that the assembly
of such high-mass galaxies is not effective at lower redshift.Comment: 15 pages, 14 figures. Published in A&
Non-linear Matter Spectra in Coupled Quintessence
We consider cosmologies in which a dark-energy scalar field interacts with
cold dark matter. The growth of perturbations is followed beyond the linear
level by means of the time-renormalization-group method, which is extended to
describe a multi-component matter sector. Even in the absence of the extra
interaction, a scale-dependent bias is generated as a consequence of the
different initial conditions for baryons and dark matter after decoupling. The
effect is enhanced significantly by the extra coupling and can be at the 2-3
percent level in the range of scales of baryonic acoustic oscillations. We
compare our results with N-body simulations, finding very good agreement.Comment: 20 pages, 6 figures, typo correcte
The seaplane base Ivo Monti at S. Nicola Varano (FG): a monument of military archeology, between history and protection
Built in the years between 1915 and 1918, and located on the west bank of the \u201cVarano\u201d Lake, a bay running along the village of \u201cCagnano Varano\u201d, the \u201cIvo Monti\u201d seaplane base was erected on a pre-existing medieval settlement which belonged to the Benedictine Monks from the town of \u201cSan Nicola Imbuti\u201d.
During WWI, this seaplane base was turned, from a simple water airport, into a strategic military base for floatplanes. As a matter of fact, the large lagoon could be used as landing spot for the planes sent off to patrol the dalmatic coast, one of the historical regions of Croatia, then controlled by the Austrians.
After WWI, after the seaplane became an outdated technology, the \u201cIvo Monti\u201d base was progressively dismantled and then totally abandoned at the beginning of the 1950s.
In 2014, considering the historical relevance of this site and the unmistakable architectural value of its elements, a research framework agreement was signed between the \u201cDICEA\u201d Department of Marche Polytechnic University and the city council of the town hosting the site, aimed at the development of shared scientific research projects revolving around the study, the valorisation, and the restoration of the military complex in question, which had been in a complete state of decay and neglect for too long.
The still ongoing research project mentioned presents two main missions: the first is the historical reconstruction, the geometric mapping, and the robustness analysis of the ruins, by studying and faithfully representing the state of deterioration of the building materials and of the facilities; the second is the identification and the testing of potential architectural solutions for the conversion and the reuse of the site and of its facilities
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