483 research outputs found
Two-Face(s): ionized and neutral gas winds in the local Universe
We present a comprehensive study of the Na I 5890, 5895 (Na I D)
resonant lines in the Sloan Digital Sky Survey (SDSS, DR7) spectroscopic sample
to look for neutral gas outflows in the local galaxies. Individual galaxy
spectra are stacked in bins of M and SFR to investigate the dependence
of galactic wind occurrence and velocity as a function of the galaxy position
in the SFR- plane. In massive galaxies at the high SFR tail we find
evidence of a significant blue-shifted Na I D absorption, which we interpret as
evidence of neutral outflowing gas. The occurrence of the blue-shifted
absorption is observed at the same significance for purely SF galaxies, AGN and
composite systems at fixed SFR. In all classes of objects the blue-shift is the
largest and the Na I D equivalent width the smallest for face-on galaxies while
the absorption feature is at the systemic velocity for edge-on systems. This
indicates that the neutral outflow is mostly perpendicular or biconical with
respect to the galactic disk. We also compare the kinematics of the neutral gas
with the ionized gas phase as traced by the [OIII]5007, H,
[NII] and [NII] emission lines. Differently for the
neutral gas phase, all the emission lines show evidence of perturbed kinematics
only in galaxies with a significant level of nuclear activity and, they are
independent from the disk inclination. In conclusion, we find that, in the
local Universe, galactic winds show two faces which are related to two
different ejection mechanisms, namely the neutral outflowing gas phase related
to the SF activity along the galaxy disk and the ionized phase related to the
AGN feedback. In both the neutral and ionized gas phases, the observed wind
velocities suggest that the outflowing gas remains bound to the galaxy with no
definitive effect on the gas reservoir.Comment: Accepted to A&A, 13 pages, 9 figure
On Properties of Boundaries and Electron Conductivity in Mesoscopic Polycrystalline Silicon Films for Memory Devices
We present the results of molecular dynamics modeling on the structural
properties of grain boundaries (GB) in thin polycrystalline films. The
transition from crystalline boundaries with low mismatch angle to amorphous
boundaries is investigated. It is shown that the structures of the GBs satisfy
a thermodynamical criterion. The potential energy of silicon atoms is closely
related with a geometrical quantity -- tetragonality of their coordination with
their nearest neighbors. A crossover of the length of localization is observed.
To analyze the crossover of the length of localization of the single-electron
states and properties of conductance of the thin polycrystalline film at low
temperature, we use a two-dimensional Anderson localization model, with the
random one-site electron charging energy for a single grain (dot), random
non-diagonal matrix elements, and random number of connections between the
neighboring grains. The results on the crossover behavior of localization
length of the single-electron states and characteristic properties of
conductance are presented in the region of parameters where the transition from
an insulator to a conductor regimes takes place.Comment: 8 pages, 3 figure
SKELETAL MUSCLE MITOCHONDRIAL OXIDATIVE CAPACITY AND UNCOUPLING PROTEIN 3 ARE DIFFERENTLY INFLUENCED BY SEMISTARVATION AND REFEEDING
Star formation properties of sub-mJy radio sources
We investigate the star formation properties of ~800 sources detected in one
of the deepest radio surveys at 1.4 GHz. Our sample spans a wide redshift range
(~0.1 - 4) and about four orders of magnitude in star formation rate (SFR). It
includes both star forming galaxies (SFGs) and active galactic nuclei (AGNs),
further divided into radio-quiet and radio-loud objects. We compare the SFR
derived from the far infrared luminosity, as traced by Herschel, with the SFR
computed from their radio emission. We find that the radio power is a good SFR
tracer not only for pure SFGs but also in the host galaxies of RQ AGNs, with no
significant deviation with redshift or specific SFR. Moreover, we quantify the
contribution of the starburst activity in the SFGs population and the
occurrence of AGNs in sources with different level of star formation. Finally
we discuss the possibility of using deep radio survey as a tool to study the
cosmic star formation history.Comment: 18 pages, 14 figures, 1 table (available in its entirety as ancillary
data
Sub-mm detection of a high redshift Type 2 QSO
We report on the first SCUBA detection of a Type 2 QSO at z=3.660 in the
Chandra Deep Field South. This source is X-ray absorbed, shows only narrow
emission lines in the optical spectrum and is detected in the sub-mm: it is the
ideal candidate in an evolution scheme for AGN (e.g. Fabian (1999); Page et al.
(2004)) of an early phase corresponding to the main growth of the host galaxy
and formation of the central black hole. The overall photometry (from the radio
to the X-ray energy band) of this source is well reproduced by the spectral
energy distribution (SED) of NGC 6240, while it is incompatible with the
spectrum of a Type 1 QSO (3C273) or a starburst galaxy (Arp 220). Its sub-mm
(850 \mu m) to X-ray (2 keV) spectral slope (alpha_SX) is close to the
predicted value for a Compton-thick AGN in which only 1% of the nuclear
emission emerges through scattering. Using the observed flux at 850 \mu m we
have derived a SFR=550--680 M_dust=4.2 10^8 M_odotComment: 6 Pages, 5 Figures, accepted for publication in MNRA
The Bright and Dark Sides of High-Redshift starburst galaxies from {\it Herschel} and {\it Subaru} observations
We present rest-frame optical spectra from the FMOS-COSMOS survey of twelve
\textit{Herschel} starburst galaxies, with Star Formation Rate
(SFR) elevated by 8, on average, above the star-forming Main Sequence
(MS). Comparing the H to IR luminosity ratio and the Balmer Decrement
we find that the optically-thin regions of the sources contain on average only
percent of the total SFR whereas percent comes from an
extremely obscured component which is revealed only by far-IR observations and
is optically-thick even in H. We measure the [NII]/H
ratio, suggesting that the less obscured regions have a metal content similar
to that of the MS population at the same stellar masses and redshifts. However,
our objects appear to be metal-rich outliers from the metallicity-SFR
anticorrelation observed at fixed stellar mass for the MS population. The
[SII]/[SII] ratio from the average spectrum indicates an
electron density , larger than what
estimated for MS galaxies but only at the 1.5 level. Our results
provide supporting evidence that high- MS outliers are the analogous of
local ULIRGs, and are consistent with a major merger origin for the starburst
event.Comment: 6 pages, 4 figures, Accepted for publication in ApJ Letter
Mid-infrared Spitzer spectra of X-ray selected Type 2 QSOs: QSO2s are not ULIRGs
We have performed a spectroscopic study of 7 Type 2 QSOs using the
mid-infrared spectrometer IRS on board the Spitzer Space Telescope. These are
(to our knowledge) the first mid-IR spectra of X-ray selected QSO2s taken. The
objects have been selected according to their high intrinsic luminosities and
column densities in the X-rays. Their spectra strongly differ from template
spectra of Type 2 AGN at lower luminosities. They do not exhibit strong PAH
dust emission features from circum-nuclear star forming regions, typical for
lower luminosity Type 2 Seyfert galaxies or other previously used QSO2
templates, such as the (Ultra)luminous Infrared Galaxy ((U)LIRG) NGC 6240. They
also do not show the ice and silicate absorption features of highly luminous
but deeply embedded compact nuclei seen in some ULIRGs. Instead they reveal a
relatively featureless, rising continuum similar to luminous Type 1 AGN. We
also find evidence for a 10 micron silicate feature in emission. Models of
dusty tori in the AGN unification scenario predict this only for Type 1 AGN.
The ratio of the AGN continuum luminosity at 6 micron to the absorption
corrected 2-10keV X-ray AGN luminosity is very similar to that found in Seyfert
galaxies. X-ray selected QSO2s are thus characterized by powerful AGN in hosts
with a luminosity due to star formation < 1e11 L_sol. The dominance of the AGN
light in the mid-IR spectra of QSO2s together with their flatter spectral
energy distributions (SEDs) places important constraints on models of the
cosmic infrared background and of the star formation history of the universe.Comment: Accepted by ApJ, 15 pages, including 4 eps figure
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