472 research outputs found
The large scale clustering of radio sources
The observed two-point angular correlation function, w(theta), of mJy radio
sources exhibits the puzzling feature of a power-law behaviour up to very large
(almost 10 degrees) angular scales which cannot be accounted for in the
standard hierarchical clustering scenario for any realistic redshift
distribution of such sources. After having discarded the possibility that the
signal can be explained by a high density local source population, we find no
alternatives to assuming that - at variance with all the other extragalactic
populations studied so far, and in particular with optically selected quasars -
radio sources responsible for the large-scale clustering signal were
increasingly less clustered with increasing look-back time, up to at least z=1.
The data are accurately accounted for in terms of a bias function which
decreases with increasing redshift, mirroring the evolution with cosmic time of
the characteristic halo mass, M_{star}, entering the non linear regime. In the
framework of the `concordance cosmology', the effective halo mass controlling
the bias parameter is found to decrease from about 10^{15} M_{sun}/h at z=0 to
the value appropriate for optically selected quasars, 10^{13} M_{sun}/h, at
z=1.5. This suggests that, in the redshift range probed by the data, the
clustering evolution of radio sources is ruled by the growth of large-scale
structure, and that they are associated with the densest environments
virializing at any cosmic epoch. The data provide only loose constraints on
radio source clustering at z>1 so we cannot rule out the possibility that at
these redshifts the clustering evolution of radio sources enters a different
regime, perhaps similar to that found for optically selected quasars. The
dependence of w(theta) on cosmological parameters is also discussed.Comment: 9 pages, 8 figures. Accepted for publication on MNRA
Valentino Braitenberg: From neuroanatomy to behavior and back
This article compiles an expose of Valentino Braitenberg's singular view on neuroanatomy and neuroscience. The review emphasizes his topologically informed work on neuroanatomy and his dialectics of brain-based explanations of motor behavior. Some of his early ideas on topologically informed neuroanatomy are presented, together with some of his more obscure work on the taxonomy of neural fiber bundles and synaptic arborizations. His functionally informed interpretations of neuroanatomy of the cerebellum, cortex, and hippocampus, are introduced. Finally, we will touch on his philosophical views and the inextricable role of function in the explanation of neural behavior
A reassessment of the evidence of the Integrated Sachs-Wolfe effect through the WMAP-NVSS correlation
We reassess the estimate of the cross-correlation of the spatial distribution
of the NRAO VLA Sky Survey (NVSS) radio sources with that of Cosmic Microwave
Background (CMB) anisotropies from the Wilkinson Microwave Anisotropy Probe
(WMAP). This re-analysis is motivated by the fact that most previous studies
adopted a redshift distribution of NVSS sources inconsistent with recent data.
We find that the constraints on the bias-weighted redshift distribution,
b(z)xN(z), of NVSS sources, set by the observed angular correlation function,
w(theta), strongly mitigate the effect of the choice of N(z). If such
constraints are met, even highly discrepant redshift distributions yield
NVSS-WMAP cross-correlation functions consistent with each other within
statistical errors. The models favoured by recent data imply a bias factor,
b(z), decreasing with increasing z, rather than constant, as assumed by most
previous analyses. As a consequence, the function b(z)xN(z) has more weight at
z<1, i.e. in the redshift range yielding the maximum contribution to the ISW in
a standard LambdaCDM cosmology. On the whole, the NVSS turns out to be better
suited for ISW studies than generally believed, even in the absence of an
observational determination of the redshift distribution. The NVSS-WMAP
cross-correlation function is found to be fully consistent with the prediction
of the standard LambdaCDM cosmology.Comment: 6 pages, 2 figures, submitted to MNRA
Astrophysical and Cosmological Information from Large-scale sub-mm Surveys of Extragalactic Sources
We present a quantitative analysis of the astrophysical and cosmological
information that can be extracted from the many important wide-area, shallow
surveys that will be carried out in the next few years. Our calculations
combine the predictions of the physical model by Granato et al. (2004) for the
formation and evolution of spheroidal galaxies with up-to-date phenomenological
models for the evolution of starburst and normal late-type galaxies and of
radio sources. We compute the expected number counts and the redshift
distributions of these source populations separately and then focus on
proto-spheroidal galaxies. For the latter objects we predict the counts and
redshift distributions of strongly lensed sources at 250, 350, 500, and 850
micron, the angular correlation function of sources detected in the surveys
considered, the angular power spectra due to clustering of sources below the
detection limit in Herschel and Planck surveys. An optimal survey for selecting
strongly lensed proto-spheroidal galaxies is described, and it is shown how
they can be easily distinguished from the other source populations. We also
discuss the detectability of the imprints of the 1-halo and 2-halo regimes on
angular correlation functions and clustering power spectra, as well as the
constraints on cosmological parameters that can be obtained from the
determinations of these quantities. The novel data relevant to derive the first
sub-millimeter estimates of the local luminosity functions of starburst and
late-type galaxies, and the constraints on the properties of rare source
populations, such as blazars, are also briefly described.Comment: 16 pages, 10 figures. Accepted for publication on MNRA
ALMA observations of lensed Herschel sources: testing the dark matter halo paradigm
With the advent of wide-area submillimetre surveys, a large number of high-redshift gravitationally lensed dusty star-forming galaxies have been revealed. Because of the simplicity of the selection criteria for candidate lensed sources in such surveys, identified as those with S500 μm > 100 mJy, uncertainties associated with the modelling of the selection function are expunged. The combination of these attributes makes submillimetre surveys ideal for the study of strong lens statistics. We carried out a pilot study of the lensing statistics of submillimetre-selected sources by making observations with the Atacama Large Millimeter Array (ALMA) of a sample of strongly lensed sources selected from surveys carried out with the Herschel Space Observatory. We attempted to reproduce the distribution of image separations for the lensed sources using a halo mass function taken from a numerical simulation that contains both dark matter and baryons. We used three different density distributions, one based on analytical fits to the haloes formed in the EAGLE simulation and two density distributions [Singular Isothermal Sphere (SIS) and SISSA] that have been used before in lensing studies. We found that we could reproduce the observed distribution with all three density distributions, as long as we imposed an upper mass transition of ∼1013 M⊙ for the SIS and SISSA models, above which we assumed that the density distribution could be represented by a Navarro–Frenk–White profile. We show that we would need a sample of ∼500 lensed sources to distinguish between the density distributions, which is practical given the predicted number of lensed sources in the Herschel surveys
Primary Mandibular Condyle Xanthoma: Case Report and Literature Review
Bone xanthoma is a rare benign primary bone lesion histologically characterized by sheets of foamy cells which are macrophages with a cytoplasm filled with droplets of fat. It is usually associated with endocrine or metabolic diseases, in the absence of which the lesion is called primary xanthoma. Because of the lack of pathognomonic radiologic and clinical features, they require a differential diagnosis with a broad spectrum of lesions with a varying degree of malignant potential. We describe a case of primary mandibular xanthoma of a 16-year-old girl without typical cutaneous manifestations and alterations in lipid values. The temporomandibular joint involvement at the mandibular condyle is peculiar in the case described here. We present even a qualitative systematic review of the literature on primary xanthoma of the jaws in others to draw up treatment guidelines
Modelling high resolution ALMA observations of strongly lensed highly star forming galaxies detected by <i>Herschel</i>
We have modelled ∼ 0.1 arcsec resolution ALMA imaging of six strong gravitationally lensed galaxies detected by the Herschel Space Observatory. Our modelling recovers mass properties of the lensing galaxies and, by determining magnification factors, intrinsic properties of the lensed sub-millimetre sources. We find that the lensed galaxies all have high ratios of star formation rate to dust mass, consistent with or higher than the mean ratio for high redshift sub-millimetre galaxies and low redshift ultra-luminous infra-red galaxies. Source reconstruction reveals that most galaxies exhibit disturbed morphologies. Both the cleaned image plane data and the directly observed interferometric visibilities have been modelled, enabling comparison of both approaches. In the majority of cases, the recovered lens models are consistent between methods, all six having mass density profiles that are close to isothermal. However, one system with poor signal to noise shows mildly significant differences
Origins Space Telescope: predictions for far-IR spectroscopic surveys
We illustrate the extraordinary potential of the (far-IR) Origins Survey
Spectrometer (OSS) on board the Origins Space Telescope (OST) to address a
variety of open issues on the co-evolution of galaxies and AGNs. We present
predictions for blind surveys, each of 1000 h, with different mapped areas (a
shallow survey covering an area of 10 deg and a deep survey of 1
deg) and two different concepts of the OST/OSS: with a 5.9 m telescope
(Concept 2, our reference configuration) and with a 9.1 m telescope (Concept 1,
previous configuration). In 1000 h, surveys with the reference concept will
detect from to lines from
- star-forming galaxies and from
to lines from - AGNs. The shallow survey will detect
substantially more sources than the deep one; the advantage of the latter in
pushing detections to lower luminosities/higher redshifts turns out to be quite
limited. The OST/OSS will reach, in the same observing time, line fluxes more
than one order of magnitude fainter than the SPICA/SMI and will cover a much
broader redshift range. In particular it will detect tens of thousands of
galaxies at , beyond the reach of that instrument. The polycyclic
aromatic hydrocarbons lines are potentially bright enough to allow the
detection of hundreds of thousands of star-forming galaxies up to ,
i.e. all the way through the re-ionization epoch. The proposed surveys will
allow us to explore the galaxy-AGN co-evolution up to with very
good statistics. OST Concept 1 does not offer significant advantages for the
scientific goals presented here.Comment: 24 pages, 20 figures, 2 tables, accepted for publication in PAS
The far-infrared/radio correlation for a sample of strongly lensed dusty star-forming galaxies detected by Herschel
We investigate the radio/far-infrared (FIR) correlation for a sample of 28 bright high-redshift (1 z 4) star-forming galaxies selected in the FIR from the Herschel -ATLAS fields as candidates to be strongly gravitationally lensed. The radio information comes either from high sensitivity dedicated Australia Telescope Compact Array observations at 2.1 GHz or from cross-matches with the FIRST surv e y at 1.4 GHz. By taking advantage of source brightness possibly enhanced by lensing magnification, we identify a weak evolution with redshift out to z 4 of the FIR-to-radio luminosity ratio q FIR . We also find that the q FIR parameter as a function of the radio power L 1 . 4 GHz displays a clear decreasing trend, similarly to what is observed for optically/radio- selected lensed quasars found in literature, yet co v ering a complementary region in the q FIR –L 1 . 4 GHz diagram. We interpret such a behaviour in the framework of an in situ galaxy formation scenario, as a result of the transition from an early dust-obscured star-forming phase (mainly pinpointed by our FIR selection) to a late radio-loud quasar phase (preferentially sampled by the optical/radio selection)
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