35,359 research outputs found
The Peculiar Balmer Line Profiles of OQ 208
We present spectrophotometric observations of the Broad Line Radio Galaxy OQ
208 (Mrk 668, 1404+286) obtained between 1985 and 1991. We show that the Balmer
line fluxes and profile shapes undergo remarkable changes. The ratio of
intensities between the broad and narrow components of Hbeta increased
monotonically from 15 in 1985 to 40 in 1991. The peak of the broad components
of Hbeta and Halpha were known to be strongly displaced to the red. We have
discovered a correlation between the amplitude of the broad peak displacement
and the luminosity of Hbeta, in the sense that the displacement is larger when
the line luminosity is higher. We suggest that the observations are not
compatible with either a binary Broad Line Region model or one involving
ballistic acceleration of the line emitting gas. Radiative acceleration of a
system of outflowing clouds readily explains the correlation between line shift
and luminosity as well as the peculiar line profiles. Furthermore, it seems
that most or all of the Balmer emission originates from the inward face of the
clouds. Theoretical line profiles suggest that the observed Hbeta profile is
best fit assuming the contribution of an ensemble which might be spherical or
confined in a thick disk in addition to a component emitted in a thin shell
contained in a cone of half opening angle 12 degrees seen along its axis.Comment: 28 pages + tables and figures available upon request, Latex, No
preprint numbe
CPT, Lorentz invariance and anomalous clash of symmetries
In this paper we first discuss the analysis regarding the role of Lorentz
symmetry in the perturbative non-gravitational anomalies for a family of
fermions, which has been recently performed in arXiv:0809.0184. The theory is
assumed to be translational invariant, power-counting renormalizable and based
on a local action, but is allowed to have general Lorentz violating operators,
including those that break CPT. The main result is that Lorentz symmetry does
not participate in the clash of symmetries that leads to the anomalies.
Moreover, here we provide a simple "semiclassical" argument that shortly
illustrates the origin of this fact.Comment: 8 pages, no figures. To appear in the proceedings of Discrete '08:
Symposium on Prospects in the Physics of Discrete Symmetries, Valencia,
Spain, 11-16 Dec 200
Detection of a large fraction of atomic gas not associated with star-forming material in M17 SW
We probe the column densities and masses traced by the ionized and neutral
atomic carbon with spectrally resolved maps, and compare them to the diffuse
and dense molecular gas traced by [C I] and low- CO lines toward the
star-forming region M17SW. We mapped a 4.1pc x 4.7pc region in the [C I] 609
m line using the APEX telescope, as well as the CO isotopologues with the
IRAM 30m telescope. We analyze the data based on velocity channel maps that are
1 km/s wide. We correlate their spatial distribution with that of the [C II]
map obtained with SOFIA/GREAT. Optically thin approximations were used to
estimate the column densities of [C I] and [C II] in each velocity channel. The
spatial distribution of the [C I] and all CO isotopologues emission was found
to be associated with that of [C II] in about 20%-80% of the mapped region,
with the high correlation found in the central (15-23 km/s ) velocity channels.
The excitation temperature of [C I] ranges between 40 K and 100 K in the inner
molecular region of M17 SW. Column densities in 1 km/s channels between
~10 and ~10 cm were found for [C I]. Just ~20% of the
velocity range (~40 km/s) that the [C II] line spans is associated with the
star-forming material traced by [C I] and CO. The total gas mass estimated from
the [C II] emission gives a lower limit of ~4.4x10 . At least
64% of this mass is not associated with the star-forming material in M17SW. We
also found that about 36%, 17%, and 47% of the [C II] emission is associated
with the HII, HI, and H_2 regimes, respectively. Comparisons with the
H41 line shows an ionization region mixed with the neutral and part of
the molecular gas, in agreement with the clumped structure and dynamical
processes at play in M17SW. These results are also relevant to extra-galactic
studies in which [C II] is often used as a tracer of star-forming material.Comment: 21 pages + 6 pages of appendix, 32 figures in total, accepted for
publication on A&A (10/12/2014) Relevant calibrated data cubes are available
on CD
Astrophysical Implications of a Visible Dark Matter Sector from a Custodially Warped-GUT
We explore, within the warped extra dimensional framework, the possibility of
finding anti-matter signals in cosmic rays (CRs) from dark matter (DM)
annihilation. Exchange of order 100 GeV radion, an integral part of our setup,
generically results in Sommerfeld enhancement of the annihilation rate for TeV
DM mass. No dark sector is required to obtain boosted annihilation cross
sections. A mild hierarchy between the radion and DM masses can be natural due
to the pseudo-Goldstone boson nature of the radion. Implications of Sommerfeld
enhancement in warped grand unified theory (GUT) models, where proton stability
implies a DM candidate, are studied. We show, via partially unified Pati-Salam
group, how to incorporate a custodial symmetry for Z->b\bar b into the GUT
framework such that a few TeV Kaluza-Klein (KK) mass scale is allowed by
precision tests. The model with smallest fully unified SO(10) representation
allows us to decouple the DM from the electroweak sector. Thus, a correct DM
relic density is obtained and direct detection bounds are satisfied. Looking at
robust CR observables, a possible future signal in the \bar p / p flux ratio is
found. We show how to embed a similar custodial symmetry for the right handed
tau, allowing it to be strongly coupled to KK particles. Such a scenario might
lead to observed signal in CR positrons; however, the DM candidate in this case
can not constitute all of the DM in the universe. Independently of the above,
the strong coupling between KK particles and tau's can lead to striking LHC
signals.Comment: 53 pages, 9 figure
Discovery of a wide companion near the deuterium burning mass limit in the Upper Scorpius association
We present the discovery of a companion near the deuterium burning mass limit
located at a very wide distance, at an angular separation of 4.6+/-0.1 arcsec
(projected distance of ~ 670 AU) from UScoCTIO108, a brown dwarf of the very
young Upper Scorpius association. Optical and near-infrared photometry and
spectroscopy confirm the cool nature of both objects, with spectral types of M7
and M9.5, respectively, and that they are bona fide members of the association,
showing low gravity and features of youth. Their masses, estimated from the
comparison of their bolometric luminosities and theoretical models for the age
range of the association, are 60+/-20 and 14^{+2}_{-8} MJup, respectively. The
existence of this object around a brown dwarf at this wide orbit suggests that
the companion is unlikely to have formed in a disk based on current planet
formation models. Because this system is rather weakly bound, they did not
probably form through dynamical ejection of stellar embryos.Comment: 10 pages, including 4 figures and 2 table
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