3,536 research outputs found
Dust in 3C324
The results of a deep submillimetre observation using SCUBA of the powerful
radio galaxy 3C324, at redshift z=1.206, are presented. At 850 microns,
emission from the location of the host radio galaxy is marginally detected at
the 4.2 sigma level, 3.01 +/- 0.72 mJy, but there is no detection of emission
at 450 microns to a 3 sigma limit of 21 mJy. A new 32 GHz radio observation
using the Effelsberg 100m telescope confirms that the sub-millimetre signal is
not associated with synchrotron emission. These observations indicate that both
the mass of warm dust within 3C324, and the star formation rate, lie up to an
order of magnitude below the values recently determined for radio galaxies at z
= 3 to 4. The results are compared with dust masses and star formation rates
derived in other ways for 3C324.Comment: 5 pages LaTeX, including 1 figure. Accepted for publication in MNRA
Non-intrusive Time Galerkin POD for Optimal Control of a Fixed-Bed Reactor for CO<sub>2</sub> Methanation
Heating of the molecular gas in the massive outflow of the local ultraluminous-infrared and radio-loud galaxy 4C12.50
We present a comparison of the molecular gas properties in the outflow vs. in
the ambient medium of the local prototype radio-loud and ultraluminous-infrared
galaxy 4C12.50 (IRAS13451+1232), using new data from the IRAM Plateau de Bure
interferometer and 30m telescope, and the Herschel space telescope. Previous
H_2 (0-0) S(1) and S(2) observations with the Spitzer space telescope had
indicated that the warm (~400K) molecular gas in 4C12.50 is made up of a
1.4(+-0.2)x10^8 M_sun ambient reservoir and a 5.2(+-1.7)x10^7 M_sun outflow.
The new CO(1-0) data cube indicates that the corresponding cold (25K) H_2 gas
mass is 1.0(+-0.1)x10^10 M_sun for the ambient medium and <1.3x10^8 M_sun for
the outflow, when using a CO-intensity-to-H_2-mass conversion factor alpha of
0.8 M_sun /(K km/s pc^2). The combined mass outflow rate is high, 230-800
M_sun/yr, but the amount of gas that could escape the galaxy is low. A
potential inflow of gas from a 3.3(+-0.3)x10^8 M_sun tidal tail could moderate
any mass loss. The mass ratio of warm-to-cold molecular gas is >= 30 times
higher in the outflow than in the ambient medium, indicating that a
non-negligible fraction of the accelerated gas is heated to temperatures at
which star formation is inefficient. This conclusion is robust against the use
of different alpha factor values, and/or different warm gas tracers (H_2 vs.
H_2 plus CO): with the CO-probed gas mass being at least 40 times lower at 400K
than at 25K, the total warm-to-cold mass ratio is always lower in the ambient
gas than in the entrained gas. Heating of the molecular gas could facilitate
the detection of new outflows in distant galaxies by enhancing their emission
in intermediate rotational number CO lines.Comment: A&A, in pres
Reflectivity Anisotropy Spectra of Cu- and Ag- (110) surfaces from {\it ab initio} theory
We are able to disentagle the effects of the intraband and interband parts of
the bulk dielectric function on the bare dielectric anisotropy of the surface.
We show how the position, sign and amplitude of the structures observed in such
spectra depend on the above quantities. The lineshape of all the calculated
structures agree very well with the ones observed experimentally for samples
treated by suitable surface cleaning. In particular, we reproduce the observed
single peak structure of Ag at high energy, found to represent a state of the
clean surface different from the one giving the originally observed double peak
structure. This results is not reproduced by the 'local field' model.Comment: 4 pages, 3 figures. submitted to Phys. Rev. Let
Multifrequency Observations of the Blazar 3C 279 in January 2006
We report first results of a multifrequency campaign from radio to hard X-ray
energies of the prominent gamma-ray blazar 3C 279, which was organised around
an INTEGRAL ToO observation in January 2006, and triggered on its optical
state. The variable blazar was observed at an intermediate optical state, and a
well-covered multifrequency spectrum from radio to hard X-ray energies could be
derived. The SED shows the typical two-hump shape, the signature of non-thermal
synchrotron and inverse-Compton (IC) emission from a relativistic jet. By the
significant exposure times of INTEGRAL and Chandra, the IC spectrum (0.3 - 100
keV) was most accurately measured, showing - for the first time - a possible
bending. A comparison of this 2006 SED to the one observed in 2003, also
centered on an INTEGRAL observation, during an optical low-state, reveals the
surprising fact that - despite a significant change at the high-energy
synchrotron emission (near-IR/optical/UV) - the rest of the SED remains
unchanged. In particular, the low-energy IC emission (X- and hard X-ray
energies) remains the same as in 2003, proving that the two emission components
do not vary simultaneously, and provides strong constraints on the modelling of
the overall emission of 3C 279.Comment: 4 pages, 6 figures; to be published in the Proc. of the 6th INTEGRAL
workshop "The Obscured Universe" (Moscow, July 2-8, 2006), eds. S. Grebenev,
R. Sunyaev, C. Winkler, ESA SP 622 (2006
Galaxy And Mass Assembly (GAMA) : The mechanisms for quiescent galaxy formation at z<1
© 2016 The Authors. One key problem in astrophysics is understanding how and why galaxies switch off their star formation, building the quiescent population that we observe in the local Universe. From the Galaxy And Mass Assembly and VIsible MultiObject Spectrograph Public Extragalactic Redshift surveys, we use spectroscopic indices to select quiescent and candidate transition galaxies.We identify potentially rapidly transitioning post-starburst (PSB) galaxies and slower transitioning green-valley galaxies. Over the last 8Gyr, the quiescent population has grown more slowly in number density at high masses (M * > 10 11 M ⊙ ) than at intermediate masses (M * > 10 10.6 M ⊙ ). There is evolution in both the PSB and green-valley stellar mass functions, consistent with higher mass galaxies quenching at earlier cosmic times.At intermediatemasses (M * > 10 10.6 M ⊙ ), we find a green-valley transition time-scale of 2.6 Gyr. Alternatively, at z ~ 0.7, the entire growth rate could be explained by fast-quenching PSB galaxies, with a visibility time-scale of 0.5 Gyr. At lower redshift, the number density of PSBs is so low that an unphysically short visibility window would be required for them to contribute significantly to the quiescent population growth. The importance of the fast-quenching route may rapidly diminish at z 10 11 M ⊙ ), there is tension between the large number of candidate transition galaxies compared to the slow growth of the quiescent population. This could be resolved if not all high-mass PSB and green-valley galaxies are transitioning from star forming to quiescent, for example if they rejuvenate out of the quiescent population following the accretion of gas and triggering of star formation, or if they fail to completely quench their star formation
On the Calibration of Full-polarization 86GHz Global VLBI Observations
We report the development of a semi-automatic pipeline for the calibration of
86 GHz full-polarization observations performed with the Global Millimeter-VLBI
array (GMVA) and describe the calibration strategy followed in the data
reduction. Our calibration pipeline involves non-standard procedures, since
VLBI polarimetry at frequencies above 43 GHz is not yet well established. We
also present, for the first time, a full-polarization global-VLBI image at 86
GHz (source 3C 345), as an example of the final product of our calibration
pipeline, and discuss the effect of instrumental limitations on the fidelity of
the polarization images. Our calibration strategy is not exclusive for the
GMVA, and could be applied on other VLBI arrays at millimeter wavelengths. The
use of this pipeline will allow GMVA observers to get fully-calibrated datasets
shortly after the data correlation.Comment: 10 pages, 10 figures. Accepted for publication in A&
Generalized Assisted Inflation
We obtain a new class of exact cosmological solutions for multi-scalar fields
with exponential potentials. We generalize the assisted inflation solutions
previously obtained, and demonstrate how they are modified when there exist
cross-couplings between the fields, such as occur in supergravity inspired
cosmological models.Comment: 5 page
Finite Action in d5 Gauged Supergravity and Dilatonic Conformal Anomaly for Dual Quantum Field Theory
Gauged supergravity (SG) with single scalar (dilaton) and arbitrary scalar
potential is considered. Such dilatonic gravity describes special RG flows in
extended SG where scalars lie in one-dimensional submanifold of total space.
The surface counterterm and finite action for such gauged SG in three-, four-
and five-dimensional asymptotically AdS space are derived. Using finite action
and consistent gravitational stress tensor (local surface counterterm
prescription) the regularized expressions for free energy, entropy and mass of
d4 dilatonic AdS black hole are found. The same calculation is done within
standard reference background subtraction.
The dilaton-dependent conformal anomaly from d3 and d5 gauged SGs is
calculated using AdS/CFT correspondence. Such anomaly should correspond to two-
and four-dimensional dual quantum field theory which is classically (not
exactly) conformally invariant, respectively. The candidate c-functions from d3
and d5 SGs are suggested. These c-functions which have fixed points in
asymptoticaly AdS region are expressed in terms of dilatonic potential and they
are positively defined and monotonic for number of potentials.Comment: LaTeX file, 46 pages, two appendixes and some clarifications are
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