10,138 research outputs found
A new twist to an old story: HE 0450-2958, and the ULIRG(optically bright QSO) transition hypothesis
We report on interferometric imaging of the CO J=1--0 and J=3--2 line
emission from the controversial QSO/galaxy pair HE 0450--2958. {\it The
detected CO J=1--0 line emission is found associated with the disturbed
companion galaxy not the luminous QSO,} and implies , which is \ga 30% of the dynamical mass in
its CO-luminous region. Fueled by this large gas reservoir this galaxy is the
site of an intense starburst with , placing
it firmly on the upper gas-rich/star-forming end of Ultra Luminous Infrared
Galaxies (ULIRGs, ). This makes HE 0450--2958 the
first case of extreme starburst and powerful QSO activity, intimately linked
(triggered by a strong interaction) but not coincident. The lack of CO emission
towards the QSO itself renews the controversy regarding its host galaxy by
making a gas-rich spiral (the typical host of Narrow Line Seyfert~1 AGNs) less
likely. Finally, given that HE 0450--2958 and similar IR-warm QSOs are
considered typical ULIRG(optically bright QSO) transition candidates, our
results raise the possibility that some may simply be {\it gas-rich/gas-poor
(e.g. spiral/elliptical) galaxy interactions} which ``activate'' an optically
bright unobscured QSO in the gas-poor galaxy, and a starburst in the gas-rich
one. We argue that such interactions may have gone largely unnoticed even in
the local Universe because the combination of tools necessary to disentagle the
progenitors (high resolution and S/N optical {\it and} CO imaging) became
available only recently.Comment: 25 pages, 5 figures, accepted for publication by The Astrophysical
Journa
Chiral density waves in quark matter within the Nambu--Jona-Lasinio model in an external magnetic field
A possibility of formation of static dual scalar and pseudoscalar density
wave condensates in dense quark matter is considered for the
Nambu--Jona-Lasinio model in an external magnetic field. Within a mean-field
approximation, the effective potential of the theory is obtained and its minima
are numerically studied; a phase diagram of the system is constructed. It is
shown that the presence of a magnetic field favors the formation of spatially
inhomogeneous condensate configurations at low temperatures and arbitrary
non-zero values of the chemical potential.Comment: 13 pages, 4 figure
Introduction: revisiting Moroccan migrations
Since the 1960s, Morocco has evolved into one of the world's leading emigration countries and in many ways migration has permeated Morocco's social, cultural and economic life. However, Morocco's position within Euro-African migration systems seems to be undergoing significant changes since 2000. Although Morocco remains primarily a country of emigration, it is also becoming a destination for migrants and refugees from sub-Saharan Africa and, to some extent, from Europe. The growing presence of immigrants confronts Moroccan society with an entirely new set of social, cultural, political and legal issues around diversity and integration. This special issue explores how continued emigration and increasing immigration is transforming contemporary Moroccan society, with a particular emphasis on the way in which the Moroccan state is dealing with these shifting migratory realities. The analyses highlight how existing migration theories can help to make sense of these transformations and, vice-versa, how the Moroccan case can contribute to migration scholarship. The Moroccan migration experience particularly exemplifies the value and necessity of going beyond Euro-centric biases in migration research that artificially divide the world into 'receiving' and 'sending' countries.Seventh Framework Programme (FP7)Institutions, Decisions and Collective Behaviou
Valency of rare earths in RIn3 and RSn3: Ab initio analysis of electric-field gradients
In RIn3 and RSn3 the rare earth (R) is trivalent, except for Eu and Yb, which
are divalent. This was experimentally determined in 1977 by perturbed angular
correlation measurements of the electric-field gradient on a 111Cd impurity. At
that time, the data were interpreted using a point charge model, which is now
known to be unphysical and unreliable. This makes the valency determination
potentially questionable. We revisit these data, and analyze them using ab
initio calculations of the electric-field gradient. From these calculations,
the physical mechanism that is responsible for the influence of the valency on
the electric-field gradient is derived. A generally applicable scheme to
interpret electric-field gradients is used, which in a transparent way
correlates the size of the field gradient with chemical properties of the
system.Comment: 10 page
Anti-correlation between the mass of a supermassive black hole and the mass accretion rate in type I ultraluminous infrared galaxies and nearby QSOs
We discovered a significant anti-correlation between the mass of a
supermassive black hole (SMBH), , and the luminosity ratio of
infrared to active galactic nuclei (AGN) Eddington luminosity, , over four orders of magnitude for ultraluminous infrared
galaxies with type I Seyfert nuclei (type I ULIRGs) and nearby QSOs. This
anti-correlation ( vs. ) can be interpreted
as the anti-correlation between the mass of a SMBH and the rate of mass
accretion onto a SMBH normalized by the AGN Eddington rate, . In other words, the mass accretion rate is not proportional to that of the central BH mass. Thus, this
anti-correlation indicates that BH growth is determined by the external mass
supply process, and not the AGN Eddington-limited mechanism. Moreover, we found
an interesting tendency for type I ULIRGs to favor a super-Eddington accretion
flow, whereas QSOs tended to show a sub-Eddington flow. On the basis of our
findings, we suggest that a central SMBH grows by changing its mass accretion
rate from super-Eddington to sub-Eddington. According to a coevolution scenario
of ULIRGs and QSOs based on the radiation drag process, it has been predicted
that a self-gravitating massive torus, whose mass is larger than a central BH,
exists in the early phase of BH growth (type I ULIRG phase) but not in the
final phase of BH growth (QSO phase). At the same time, if one considers the
mass accretion rate onto a central SMBH via a turbulent viscosity, the
anti-correlation ( vs. ) is well explained
by the positive correlation between the mass accretion rate
and the mass ratio of a massive torus to a SMBH.Comment: 29 pages, 4 figures, accepted for publication in Ap
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