47 research outputs found
Systemic Hypertension and Postoperative Symptomatic Spinal Epidural Hematoma : A Scoping Review
Peer reviewedPostprin
CHORUS Deliverable 3.3: Vision Document - Intermediate version
The goal of the CHORUS vision document is to create a high level vision on audio-visual search engines in order to give guidance to the future R&D work in this area (in line with the mandate of CHORUS as a Coordination Action).
This current intermediate draft of the CHORUS vision document (D3.3) is based on the previous CHORUS vision documents D3.1 to D3.2 and on the results of the six CHORUS Think-Tank meetings held in March, September and November 2007 as well as in April, July and October 2008, and on the feedback from other CHORUS events.
The outcome of the six Think-Thank meetings will not just be to the benefit of the participants which are stakeholders and experts from academia and industry – CHORUS, as a coordination action of the EC, will feed back the findings (see Summary) to the projects under its purview and, via its website, to the whole community working in the domain of AV content search.
A few subjections of this deliverable are to be completed after the eights (and presumably last) Think-Tank meeting in spring 2009
AGN Feedback in Galaxy Groups: the Delicate Touch of Self-Regulated Outflows
AGN heating, through massive subrelativistic outflows, might be the key to
solve the long-lasting `cooling flow problem' in cosmological systems. In a
previous paper, we showed that cold accretion feedback and, to a lesser degree,
Bondi self-regulated models are in fact able to quench cooling rates for
several Gyr, at the same time preserving the mainc ool core features, like
observed density and temperature profiles. Is it true also for lighter systems,
such as galaxy groups? The answer is globally yes, although with remarkable
differences. Adopting a modified version of the AMR code FLASH 3.2, we found
that successful 3D simulations with cold and Bondi models are almost convergent
in the galaxy group environment, with mechanical efficiencies in the range
5.e-4 - 1.e-3 and 5.e-2 - 1.e-1, respectively. The evolutionary storyline of
galaxy groups is dominated by a quasi-continuous gentle injection with
sub-Eddington outflows (with mechanical power and velocity around 1.e44 erg/s
and 1.e4 km/s). The cold and hybrid accretion models present, in addition, very
short quiescence periods, followed by moderate outbursts (10 times the previous
phase), which generate a series of 10-20 kpc size cavities with high density
contrast, temperatures similar to the ambient medium and cold rims. After shock
heating, a phase of turbulence promotes gas mixing and diffusion of metals,
which peak along jet-axis (up to 40 kpc) during active phases. At this stage
the tunnel, produced by the enduring outflow (hard to detect in the mock SBx
maps), is easily fragmented, producing tiny buoyant bubbles, typically a few
kpc in size. In contrast to galaxy clusters, the AGN self-regulated feedback
has to be persistent, with a `delicate touch', rather than rare and explosive
strokes. This evolutionary difference dictates in the end that galaxy groups
are not scaled-down versions of clusters.Comment: Accepted by MNRAS; 22 pages, 7 figure
Texture profile analyses in tench (Tinca tinca L., 1758) from extensive and intensive culture
Quasar induced galaxy formation: a new paradigm ?
We discuss observational evidence that quasars play a key role in the
formation of galaxies starting from the detailed study of the quasar
HE0450-2958 and extending the discussion to a series of converging evidence
that radio jets may trigger galaxy formation. The direct detection with VISIR
at the ESO-VLT of the 7 kpc distant companion galaxy of HE0450-2958 allows us
to spatially separate the sites of quasar and star formation activity in this
composite system made of two ultra-luminous infrared galaxies (ULIRGs). No host
galaxy has yet been detected for this quasar, but the companion galaxy stellar
mass would bring HE0450-2958 in the local M(BH)-M(stellar bulge) relation if it
were to merge with the QSO. This is bound to happen because of their close
distance (7 kpc) and small relative velocity (~60-200 km/s). We conclude that
we may be witnessing the building of the M(BH)-M(stellar bulge) relation, or at
least of a major event in that process. The star formation rate (~340 Msun/yr),
age (40-200 Myr) and stellar mass ([5-6]x10^10 Msun) are consistent with
jet-induced formation of the companion galaxy. We suggest that HE0450-2958 may
be fueled in fresh material by cold gas accretion from intergalactic filaments.
We map the projected galaxy density surrounding the QSO as a potential tracer
of intergalactic filaments and discuss a putative detection. Comparison to
other systems suggests that inside-out formation of quasar host galaxies and
jet-induced galaxy formation may be a common process. Two tests are proposed
for this new paradigm: (1) the detection of offset molecular gas or dust
emission with respect to the position of distant QSOs, (2) the delayed
formation of host galaxies as a result of QSO activity, hence the two step
building of the M(BH)/M(stellar bulge) ratio.Comment: 15 pages, 8 figures, accepted for publication in Astronomy and
Astrophysics (with minor corrections
Dynamics of Lyman Break Galaxies and Their Host Halos
We present deep two-dimensional spectra of 22 candidate and confirmed Lyman
break galaxies (LBGs) at redshifts 2<z<4 in the Hubble Deep Field (HDF)
obtained at the Keck II telescope. The targets were preferentially selected
with spatial extent and/or multiple knot morphologies, and we used slitmasks
and individual slits tilted to optimize measurement of any spatially resolved
kinematics. The median target magnitude was I_814=25.3, and total exposure
times ranged from 10 to 50 ks. We measure redshifts, some new, ranging from
z=0.2072 to z=4.056, including two interlopers at z<1, and resulting in a
sample of 14 LBGs with a median redshift z=2.424. The morphologies and
kinematics of the close pairs and multiple knot sources in our sample are
generally inconsistent with galaxy formation scenarios postulating that LBGs
occur only at the bottom of the potential wells of massive host halos; rather,
they support ``collisional starburst'' models with significant major merger
rates and a broad halo occupation distribution. For 13 LBGs with possible
kinematic signatures, we estimate simple dynamical masses ranging from 4e9 h^-1
M_sun to 1.1e11 h^-1 M_sun for individual galaxies and from <10e10 h^-1 to
~10^14 h^-1 M_sun with a median value 1e13 h^-1 M_sun for host dark matter
halos. Comparison with a recent numerical galaxy formation model implies that
the pairwise velocities might not reflect true dynamical masses. We compare our
dynamical mass estimates directly to stellar masses and find no evidence for a
strong correlation. The diversity of morphologies and dynamics implies that
LBGs represent a broad range of galaxy or proto-galaxy types in a variety of
evolutionary or merger stages rather than a uniform class with a narrow range
of mass.Comment: 64 pages, 8 figures; accepted for publication in ApJ. Full-res
figures available at http://www.ast.smith.edu/james
A search of CO emission lines in blazars: the low molecular gas content of BL Lac objects compared to quasars
BL Lacertae (Lac) objects that are detected at very-high energies (VHE) are
of fundamental importance to study multiple astrophysical processes, including
the physics of jets, the properties of the extragalactic background light and
the strength of the intergalactic magnetic field. Unfortunately, since most
blazars have featureless optical spectra that preclude a redshift
determination, a substantial fraction of these VHE extragalactic sources cannot
be used for cosmological studies. To assess whether molecular lines are a
viable way to establish distances, we have undertaken a pilot program at the
IRAM 30m telescope to search for CO lines in three BL Lac objects with known
redshifts. We report a positive detection of M_H2 ~ 3x10^8 Msun toward 1ES
1959+650, but due to the poor quality of the baseline, this value is affected
by a large systematic uncertainty. For the remaining two sources, W Comae and
RGB J0710+591, we derive 3sigma upper limits at, respectively, M_H2 < 8.0x10^8
Msun and M_H2 < 1.6x10^9 Msun, assuming a line width of 150 km/s and a standard
conversion factor alpha=4 M_sun/(K km/s pc^2). If these low molecular gas
masses are typical for blazars, blind redshift searches in molecular lines are
currently unfeasible. However, deep observations are still a promising way to
obtain precise redshifts for sources whose approximate distances are known via
indirect methods. Our observations further reveal a deficiency of molecular gas
in BL Lac objects compared to quasars, suggesting that the host galaxies of
these two types of active galactic nuclei (AGN) are not drawn from the same
parent population. Future observations are needed to assess whether this
discrepancy is statistically significant, but our pilot program shows how
studies of the interstellar medium in AGN can provide key information to
explore the connection between the active nuclei and the host galaxies.Comment: 8 pages, 3 figures. MNRAS accepte
Evolution of the Most Massive Galaxies to z ~ 0.6: II. The link between radio AGN activity and star formation
We analyze the optical spectra of massive (log M*/Msun > 11.4) radio-loud
galaxies at z~0.2 and z~0.6. By comparing stellar population parameters of
these radio-loud samples with radio-quiet control samples, we investigate how
the presence of a radio-emitting jet relates to the recent star formation
history of the host galaxy. We also investigate how the emission-line
properties of the radio galaxies evolve with redshift by stacking their
spectra. Our main results are the following. (1) Both at low and at high
redshift, half as many radio-loud as radio-quiet galaxies have experienced
significant star formation in the past Gyr. (2) The Balmer absorption line
properties of massive galaxies that have experienced recent star formation show
that star formation occurred as a burst in many of these systems. (3) Both the
radio and the emission-line luminosity of radio AGN evolve significantly with
redshift. However, radio galaxies with similar stellar population parameters,
have similar emission-line properties both at high- and at low-redshift. These
results suggest that massive galaxies experience cyclical episodes of gas
accretion, star formation and black hole growth, followed by the production of
a radio jet that shuts down further activity. The behaviour of galaxies with
log M*/Msun > 11.4 is the same at z = 0.6 as it is at z = 0.2, except that
higher redshift galaxies experience more star formation and black hole growth
and produce more luminous radio jets during each accretion cycle.Comment: 14 pages, 12 figures, submitted to MNRA
An OSIRIS study of the gas kinematics in a sample of UV-selected galaxies: Evidence of "Hot and Bothered" starbursts in the local Universe
We present data from Integral Field Spectroscopy for 3 supercompact
UV-Luminous Galaxies (ScUVLGs). As nearby (z~0.2), compact (R_50~1-2 kpc),
bright Paschen-alpha sources, with unusually high star formation rates
(SFR=3-100 M_sun/yr), ScUVLGs are an ideal population for studying detailed
kinematics and dynamics in actively star-forming galaxies. In addition, ScUVLGs
appear to be excellent analogs to high redshift Lyman Break Galaxies (LBGs) and
our results may offer additional insight into the dynamics of LBGs. Previous
work by our team has shown that the morphologies of these galaxies exhibit
tidal features and companions, and in this study we find that the dynamics of
ScUVLGs are dominated by disturbed kinematics of the emission line gas--
suggestive that these galaxies have undergone recent feedback, interactions or
mergers. While 2 of the 3 galaxies do display rotation, v/sigma < 1 --
suggesting dispersion dominated kinematics rather than smooth rotation. We also
simulate how these observations would appear at z~2. Lower resolution and loss
of low surface brightness features causes some apparent discrepancies between
the low-z (observed) and high-z (simulated) interpretations and quantitatively
gives different values for v/sigma, yet simulations of these low-z analogs
manage to detect the brightest regions well and resemble actual high-z
observations of LBGs.Comment: 4 pages, 4 figures (bitmapped), accepted for publication in ApJ