84 research outputs found
Using of Hybrid Supply for Electric or Hybrid Vehicles
International audienc
Post-Traumatic Intra-Cocoon Mesenteric Tear: A Case Report
Sclerosing peritonitis, more commonly called abdominal cocoon, is a rare intra-peritoneal disease that is characterized by complete or partial encapsulation of the small intestine by a thick collagenous membrane. This disease mostly presents in the form of small bowel obstruction, however in our case the patient presented with intra-cocoon bleeding following a motor vehicle accident
Black Holes in the Early Universe
The existence of massive black holes was postulated in the sixties, when the
first quasars were discovered. In the late nineties their reality was proven
beyond doubt, in the Milky way and a handful nearby galaxies. Since then,
enormous theoretical and observational efforts have been made to understand the
astrophysics of massive black holes. We have discovered that some of the most
massive black holes known, weighing billions of solar masses, powered luminous
quasars within the first billion years of the Universe. The first massive black
holes must therefore have formed around the time the first stars and galaxies
formed. Dynamical evidence also indicates that black holes with masses of
millions to billions of solar masses ordinarily dwell in the centers of today's
galaxies. Massive black holes populate galaxy centers today, and shone as
quasars in the past; the quiescent black holes that we detect now in nearby
bulges are the dormant remnants of this fiery past. In this review we report on
basic, but critical, questions regarding the cosmological significance of
massive black holes. What physical mechanisms lead to the formation of the
first massive black holes? How massive were the initial massive black hole
seeds? When and where did they form? How is the growth of black holes linked to
that of their host galaxy? Answers to most of these questions are work in
progress, in the spirit of these Reports on Progress in Physics.Comment: Reports on Progress in Physics, in pres
The effect of bars on the M*- e relation: offset, scatter and residuals correlations
We analyse a set of collisionless disc galaxy simulations to study the consequences of bar formation and evolution on the M•-σe relation of supermassive black holes (SMBHs). The redistribution of angular momentum driven by bars leads to a mass increase within the central region, raising the velocity dispersion of the bulge, σe, on average by ˜12 per cent and as much as ˜20 per cent. If a disc galaxy with an SMBH satisfying the M•-σe relation forms a bar, and the SMBH does not grow in the process, then the increase in σe moves the galaxy off the M•-σe relation. We explore various effects that can affect this result including contamination from the disc and anisotropy. The displacement from the M•-σe relation for individual model barred galaxies correlates with both the bulge-to-total stellar mass ratio, M(B)/M(B + D), and the 2D anisotropy, βφ(B + D), both measured within the effective radius of the bulge. Overall, this process leads to an M•-σe for barred galaxies offset from that of unbarred galaxies, as well as an increase in its scatter. We assemble samples of observed unbarred and barred galaxies with classical bulges and find tentative hints of an offset between the two consistent with the predicted. Including all barred galaxies, rather than just those with a classical bulge, leads to a significantly larger offset, which is mostly driven by the significantly larger offset of pseudo bulge
Kinematics and simulations of the stellar stream in the halo of the Umbrella Galaxy
We study the dynamics of faint stellar substructures around the Umbrella Galaxy, NGC 4651, which hosts a dramatic system of streams and shells formed through the tidal disruption of a nucleated dwarf elliptical galaxy. We elucidate the basic characteristics of the system (colours, luminosities, stellar masses) using multiband Subaru/Suprime-Cam images. The implied stellar mass ratio of the ongoing merger event is ∼1:50. We identify candidate kinematic tracers (globular clusters, planetary nebulae, H ii regions) and follow up a subset with Keck/DEIMOS (DEep Imaging Multi-object Spectrograph) spectroscopy to obtain velocities. We find that 15 of the tracers are likely associated with halo substructures, including the probable stream progenitor nucleus. These objects delineate a kinematically cold feature in position–velocity phase space. We model the stream using single test particle orbits, plus a rescaled pre-existing N-body simulation. We infer a very eccentric orbit with a period of ∼0.35 Gyr and turning points at ∼2–4 and ∼40 kpc, implying a recent passage of the satellite through the disc, which may have provoked the visible disturbances in the host galaxy. This work confirms that the kinematics of low surface brightness substructures can be recovered and modelled using discrete tracers – a breakthrough that opens up a fresh avenue for unravelling the detailed physics of minor merging
Galaxy bulges and their massive black holes: a review
With references to both key and oft-forgotten pioneering works, this article
starts by presenting a review into how we came to believe in the existence of
massive black holes at the centres of galaxies. It then presents the historical
development of the near-linear (black hole)-(host spheroid) mass relation,
before explaining why this has recently been dramatically revised. Past
disagreement over the slope of the (black hole)-(velocity dispersion) relation
is also explained, and the discovery of sub-structure within the (black
hole)-(velocity dispersion) diagram is discussed. As the search for the
fundamental connection between massive black holes and their host galaxies
continues, the competing array of additional black hole mass scaling relations
for samples of predominantly inactive galaxies are presented.Comment: Invited (15 Feb. 2014) review article (submitted 16 Nov. 2014). 590
references, 9 figures, 25 pages in emulateApJ format. To appear in "Galactic
Bulges", E. Laurikainen, R.F. Peletier, and D.A. Gadotti (eds.), Springer
Publishin
Substructure and Tidal Streams in the Andromeda Galaxy and its Satellites
Tidal streams from existing and destroyed satellite galaxies populate the
outer regions of the Andromeda galaxy (M31). This inhomogeneous debris can be
studied without many of the obstacles that plague Milky Way research. We review
the history of tidal stream research in M31, and in its main satellite
galaxies. We highlight the numerous tidal streams observed around M31, some of
which reside at projected distances of up to 120 kpc from the center of this
galaxy. Most notable is the Giant Stellar Stream, a signature of the most
recent significant accretion event in the M31 system. This event involved an
early-type progenitor of ~10^9 solar masses that came within a few kpc of M31's
center roughly a gigayear ago; almost all of the inner halo debris (within 50
kpc) in M31 can be tied either directly or indirectly to this event. We draw
attention to the fact that most of M31's outer halo globular clusters lie
preferentially on tidal streams and discuss the potential this offers to use
these systems as probes of the accretion history. Tidal features observed
around M33, M32, NGC 205 and NGC 147 are also reviewed. We conclude by
discussing future prospects for this field.Comment: 29 pages, 9 figures. Book chapter in Tidal Streams in the Local Group
and Beyond, eds. Heidi Newberg and Jeff Carli
The nature and origin of substructure in the outskirts of M31-II. Detailed star formation histories
While wide-field surveys of M31 have revealed much substructure at large
radii, understanding the nature and origin of this material is not
straightforward from morphology alone. Using deep HST/ACS data, we have derived
further constraints in the form of quantitative star formation histories (SFHs)
for 14 inner halo fields which sample diverse substructures. In agreement with
our previous analysis of colour-magnitude diagram morphologies, we find the
resultant behaviours can be broadly separated into two categories. The SFHs of
'disc-like' fields indicate that most of their mass has formed since z~1, with
one quarter of the mass formed in the last 5 Gyr. We find 'stream-like' fields
to be on average 1.5 Gyr older, with <10 percent of their stellar mass formed
within the last 5 Gyr. These fields are also characterised by an
age--metallicity relation showing rapid chemical enrichment to solar
metallicity by z=1, suggestive of an early-type progenitor. We confirm a
significant burst of star formation 2 Gyr ago, discovered in our previous work,
in all the fields studied here. The presence of these young stars in our most
remote fields suggests that they have not formed in situ but have been
kicked-out from through disc heating in the recent past.Comment: 14 pages, 10 figures (+12 figures in appendix). MNRAS, in pres
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