287 research outputs found
Tracing the formation of massive spheroids from high-z galaxy clustering
The high-z progenitors of local massive early-type galaxies should be
characterized by a strong level of clustering, larger than that measured for
z=3 Lyman Break Galaxies and comparable to that of z~1 EROs. First possible
evidences for such strongly clustered objects at z~2 were found by the FIRES
and K20 surveys, that have identified new classes of faint high-z K-selected
galaxies. Some details are given here for the new population of massive
star-forming galaxies at z~2, found by the K20 survey in the GOODS-South area.
Because of their much redder UV continuum, most of these galaxies would not be
selected by the Lyman Break criterion. Such objects are good candidates for the
precursors of local ellipticals caught in their formation phase. We have
calibrated a two color criterion to allow the identification of these highest
redshift galaxies in bright K-limited samples.Comment: 6 pages, 3 figures, in "Multiwavelength Mapping of Galaxy Formation
and Evolution" Venice, October 2003, conference proceeding
Neuroscienze e categorie penalistiche: tra teoria e prassi
L’elaborato propone, in prospettiva multidisciplinare ed interdisciplinare, un percorso analitico di studio ed approfondimento critico delle risultanze neuroscientifiche nel diritto penale, sostanziale e processuale. Dopo avere illustrato sinteticamente il panorama delle ricerche sperimentali in materia di libertà e coscienza delle proprie azioni e dei propri comportamenti, la tesi entra nel merito delle possibili influenze che i principi riduzionisti neuroscientifici, fautori e propugnatori della naturalizzazione della persona umana, potrebbero avere sulle fondamenta del diritto penale, dogmaticamente inteso, con l’intento di sondare l’esistenza di una terza via, compatibilista, tra il rigetto aprioristico delle acquisizioni neuroscientifiche e lo scientismo fiducioso di natura positivista, per mezzo dell’indagine attraverso la suitas della condotta, la colpevolezza e le finalità sanzionatorie penali.
Condotto il confronto con le neuroscienze di seconda generazione, il progetto prosegue, nella seconda parte, dirigendo l’analisi verso la rielaborazione concreta delle ricerche sperimentali delle neuroscienze di prima generazione, sui soggetti affetti da lesioni cerebrali, con l’obiettivo di condurre la riflessione attraverso gli istituti dell’imputabilità e della pericolosità sociale, vagliando la possibilità di estrarre dalle neuroscienze elementi utili per affrontare la crisi del concetto di autore non imputabile pericoloso di reato, nel contesto del sistema a doppio binario
Revisiting the role of the Thermally-Pulsating Asymptotic Giant Branch phase in high-redshift galaxies
We study the debated contribution from thermally pulsing asymptotic giant
branch (TP-AGB) stars in evolutionary population synthesis models. We
investigate the Spectral Energy Distributions (SEDs) of a sample of 51
spectroscopically confirmed, high-z (), galaxies using
three evolutionary population synthesis models with strong, mild and light
TP-AGB. Our sample is the largest of spectroscopically confirmed galaxies on
which such models are tested so far. Galaxies were selected as passive, but we
model them using a variety of star formation histories in order not to be
dependent on this pre-selection.
We find that the observed SEDs are best fitted with a significant
contribution of TP-AGB stars or with substantial dust attenuation. Without
including reddening, TP-AGB-strong models perform better and deliver solutions
consistent within from the best-fit ones in the vast majority of
cases. Including reddening, all models perform similarly. Using independent
constraints from observations in the mid- and far-IR, we show that
low/negligible dust attenuation, i.e. , should be
preferred for the SEDs of passively-selected galaxies. Given that TP-AGB-light
models give systematically older ages for passive galaxies, we suggest number
counts of passive galaxies at higher redshifts as a further test to
discriminate among stellar population models.Comment: 48 pages, 17 figures, 10 Tables. Accepted for publication in MNRA
Three regimes of CO emission in galaxy mergers
The conversion factor from the observable CO(1-0)
luminosity to the mass of molecular gas is known to vary between isolated
galaxies and some mergers, but the underlying reasons are not clearly
understood. Thus, the value(s) of to be adopted remain highly
uncertain. To provide better constraints, we apply the large velocity gradient
method to a series of hydrodynamical simulations of galaxies and derive the
evolution of . We report significant variations of
, and identify three distinct regimes: disk galaxies,
starbursts and post-burst phases. We show that estimating the star formation
rate over 20 Myr smooths out some of these differences, but still maintains a
distinction between disks and starbursts. We find a tighter correlation of
with the gas depletion time than with star formation rate,
yet with deviations induced by the transitions to and from the starburst
episodes. We conclude that fluctuates because of both the
feedback energy and the velocity dispersion. Identifying the phase of an
interaction by classical means (e.g. morphology, luminosity) could then help
selecting the relevant conversion factor to be used and get more accurate
estimates of the molecular masses of galaxies.Comment: A&A accepted, 6 pages, 5 figure
Star formation and quenching among the most massive galaxies at z~1.7
We have conducted a detailed object-by-object study of a mass-complete
(M*>10^11 M_sun) sample of 56 galaxies at 1.4 < z < 2 in the GOODS-South field,
showing that an accurate de-blending in MIPS/24um images is essential to
properly assign to each galaxy its own star formation rate (SFR), whereas an
automatic procedure often fails. This applies especially to galaxies with SFRs
below the Main Sequence (MS) value, which may be in their quenching phase.
After that, the sample splits evenly between galaxies forming stars within a
factor of 4 of the MS rate (~45%), and sub-MS galaxies with SFRs ~10-1000 times
smaller (~55%). We did not find a well defined class of intermediate, transient
objects below the MS, suggesting that the conversion of a massive MS galaxy
into a quenched remnant may take a relatively short time (<1 Gyr), though a
larger sample should be analyzed in the same way to set precise limits on the
quenching timescale. X-ray detected AGNs represent a ~30% fraction of the
sample, and are found among both star-forming and quenched galaxies. The
morphological analysis revealed that ~50% of our massive objects are
bulge-dominated, and almost all MS galaxies with a relevant bulge component
host an AGN. We also found sub-MS SFRs in many bulge-dominated systems,
providing support to the notion that bulge growth, AGN activity and quenching
of star formation are closely related to each other.Comment: 27 pages, 19 figures, accepted for publication by MNRA
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