31 research outputs found
Molecular gas in galaxies at all redshifts
I review some recent results about the molecular content of galaxies,
obtained essentially from the CO lines, but also dense tracers, or the dust
continuum emission. New results have been obtained on molecular cloud physics,
and their efficiency to form stars, shedding light on the Kennicutt-Schmidt law
as a function of surface density and galaxy type.
Large progress has been made on galaxy at moderate and high redshifts,
allowing to interprete the star formation history and star formation efficiency
as a function of gas content, or galaxy evolution.
In massive galaxies, the gas fraction was higher in the past, and galaxy
disks were more unstable and more turbulent.
ALMA observations will allow the study of more normal galaxies at high z with
higher spatial resolution and sensitivity.Comment: 8 pages, 4 figures, to appear in proceedings of the IAU 277th
Symposium, Editors: C. Carignan, F. Combes, K. Freema
The supergravity dual of 3d supersymmetric gauge theories with unquenched flavors
We obtain the supergravity dual of N=1 supersymmetric gauge theory in 2+1
dimensions with a large number of unquenched massless flavors. The geometries
found are obtained by solving the equations of motion of supergravity coupled
to a suitable continuous distribution of flavor branes. The background obtained
preserves two supersymmetries. We find that when N_c\ge 2N_f the behavior of
the solutions is compatible with having an asymptotically free dual gauge
theory with dynamical quarks. On the contrary, when N_c<2N_f the theory
develops a Landau pole in the UV. We also find a new family of (unflavored)
backgrounds generated by D5-branes that wrap a three-cycle of a cone with G_2
holonomy.Comment: 56 pages, 11 figures; v2: references adde
A large-scale CO survey of the Rosette Molecular Cloud: assessing the effects of O stars on surrounding molecular gas
We present a new large-scale survey of J=3-2 12CO emission covering 4.8
square degrees around the Rosette Nebula. Approximately 2000 compact clumps are
identified, with a spatially-invariant power law mass distribution index of
-1.8. Most of the inner clumps show velocity gradients of 1-3 km/s/pc, directed
away from the exciting nebula. The gradients decrease with distance from the
central O stars, and are consistent with a photoionised gas acceleration model,
assuming clump lifetimes of a few 10^5 yrs. However, in one clear case, the
observed near-constant velocity gradient is difficult to explain with simple
models. Most blue-shifted but very few of the red-shifted clumps are associated
with dark absorbing optical globules, confirming that the dominant molecular
gas motion is expansion away from the central nebula and O stars. Many clumps
also lie in a molecular ring, having an expansion velocity of 30 km/s, radius
11pc, and dynamical lifetime of ~1Myr. The J=3-2/1-0 12CO line ratios of the
clumps decrease with distance from the O stars, implying a gradient in their
surface temperatures; the results are consistent with a simple model of clump
surface heating due to the central stars.
Seven high-velocity molecular flows are found in the region, with a close
correspondence between these flows and embedded young clusters. These outflows
are sufficiently energetic to drive local gas turbulence within each cluster.
We find 14 clear examples of association between embedded young stars seen at
24um and CO clumps; these are thought to be photoevaporating molecular
envelopes. The CO clumps without evidence of embedded stars tend to have lower
velocity gradients, and it is suggested that the presence of the young star may
extend the lifespan of the photoevaporating envelope.Comment: 19 pages, 18 figures, 2 tables; to be published in MNRA
Screening effects on meson masses from holography
We study the spectra of scalar and vector mesons in four dimensional strongly
coupled SQCD-like theories in the Veneziano limit. The gauge theories describe
the low energy dynamics of intersecting D3 and D7-branes on the singular and
deformed conifold and their strong coupling regime can be explored by means of
dual fully backreacted supergravity backgrounds. The mesons we focus on are
dual to fluctuations of the worldvolume gauge field on a probe D7-brane in
these backgrounds. As we will comment in detail, the general occurrence of
various UV pathologies in the D3-D7 set-ups under study, forces us to adapt the
standard holographic recipes to theories with intrinsic cutoffs. Just as for
QED, the low energy spectra for mesonic-like bound states will be consistent
and largely independent of the UV cutoffs. We will study in detail how these
spectra vary with the number of the fundamental sea flavors and their mass.Comment: 30 pages + appendices, 10 figures; v2: subsection 3.3.3 and some
comments adde
Ultraluminous Infrared Galaxies
Ever since their discovery in the 1970's, UltraLuminous InfraRed Galaxies
(ULIRGs; classically Lir>10^12Lsun) have fascinated astronomers with their
immense luminosities, and frustrated them due to their singularly opaque
nature, almost in equal measure. Over the last decade, however, comprehensive
observations from the X-ray through to the radio have produced a consensus
picture of local ULIRGs, showing that they are mergers between gas rich
galaxies, where the interaction triggers some combination of dust-enshrouded
starburst and AGN activity, with the starburst usually dominating. Very recent
results have thrown ULIRGs even further to the fore. Originally they were
thought of as little more than a local oddity, but the latest IR surveys have
shown that ULIRGs are vastly more numerous at high redshift, and tantalizing
suggestions of physical differences between high and low redshift ULIRGs hint
at differences in their formation modes and local environment. In this review
we look at recent progress on understanding the physics and evolution of local
ULIRGs, the contribution of high redshift ULIRGs to the cosmic infrared
background and the global history of star formation, and the role of ULIRGs as
diagnostics of the formation of massive galaxies and large-scale structures.Comment: Review article, published in "Astrophysics Update 2 - topical and
timely reviews on astronomy and astrophysics". Ed. John W. Mason.
Springer/Praxis books. ISBN: 3-540-30312-X. 53 pages, 5 figures. Higher
quality figures available on reques
Poesie scelte, illustrate e commentate da Alfonso Bertoldi
Università degli Studi di Triest
Prose critiche di storia e d'arte.
"De' vari scritti ... i più videro la luce, dall'89 al '95, nella Nueva antologia e nel Giornale storico della letterature italiana: due (il sesto e il decimo ...) sono del tutto inediti. Ma inedite sono anche molte parti de'rimanenti, che qui vennero quale arricchito di nuove ragional e testimonianze, quale riíatto, quale ritoccato e corretto."--Avvertenza.Bibliographical foot-notes.L'ode "Per l'inclita nice".--Il Parini illustrato.--Storia del "Giorno".--Il Duranti e il Parini.--Ancora di un amore e di un'ode del Foscolo.--Faville foscoliane.--Pietro Giordani e altri personaggi del tempo.--L'amicizia di P. Giordani con A. Cesari.--Il Giordani, il Betti, e vari altri.--Movente e significato della Bassvilliana.Mode of access: Internet
Modello Ornamentale Internazionale n.DM/038018, depositato il 28.10.1996 “Orologio a pendolo portatile da tavolo”
Si tratta di orologio a pendolo che comprende un involucro formato da due semigusci allungati, incernierati alle loro estrermità superiori e divaricabili a quelle inferiori di appoggio e un meccanismo di orologio a pendolo contenibile entro detto involucro