325 research outputs found
Assessing the Prosody of Non-Native Speakers of English: Measures and Feature Sets
In this paper, we describe a new database with audio recordings of non-native (L2) speakers of English, and the perceptual evaluation experiment conducted with native English speakers for assessing the prosody of each recording. These annotations are then used to compute the gold standard using different methods, and a series of regression experiments is conducted to evaluate their impact on the performance of a regression model predicting the degree of Abstract naturalness of L2 speech. Further, we compare the relevance of different feature groups modelling prosody in general (without speech tempo), speech rate and pauses modelling speech tempo (fluency), voice quality, and a variety of spectral features. We also discuss the impact of various fusion strategies on performance.Overall, our results demonstrate that the prosody of non-native speakers of English as L2 can be reliably assessed using supra- segmental audio features; prosodic features seem to be the most important ones
Obscuration in extremely luminous quasars
The spectral energy distributions and infrared (IR) spectra of a sample of
obscured AGNs selected in the mid-IR are modeled with recent clumpy torus
models to investigate the nature of the sources, the properties of the
obscuring matter, and dependencies on luminosity. The sample contains 21
obscured AGNs at z=1.3-3 discovered in the largest Spitzer surveys (SWIRE,
NDWFS, & FLS) by means of their extremely red IR to optical colors. All sources
show the 9.7micron silicate feature in absorption and have extreme mid-IR
luminosities (L(6micron)~10^46 erg/s). The IR SEDs and spectra of 12 sources
are well reproduced with a simple torus model, while the remaining 9 sources
require foreground extinction from a cold dust component to reproduce both the
depth of the silicate feature and the near-IR emission from hot dust. The
best-fit torus models show a broad range of inclinations, with no preference
for the edge-on torus expected in obscured AGNs. Based on the unobscured QSO
mid-IR luminosity function, and on a color-selected sample of obscured and
unobscured IR sources, we estimate the surface densities of obscured and
unobscured QSOs at L(6micron)>10^12 Lsun, and z=1.3-3.0 to be about 17-22
deg^-2, and 11.7 deg^-2, respectively. Overall we find that ~35-41% of luminous
QSOs are unobscured, 37-40% are obscured by the torus, and 23-25% are obscured
by a cold absorber detached from the torus. These fractions constrain the torus
half opening angle to be ~67 deg. This value is significantly larger than found
for FIR selected samples of AGN at lower luminosity (~46 deg), supporting the
receding torus scenario. A far-IR component is observed in 8 objects. The
estimated far-IR luminosities associated with this component all exceed
3.3x10^12 Lsun, implying SFRs of 600-3000 Msun/yr. (Abridged)Comment: ApJ accepte
Near-infrared polarimetric adaptive optics observations of NGC 1068: A torus created by a hydromagnetic outflow wind
et al.We present J′ and K′ imaging linear polarimetric adaptive optics observations of NGC 1068 using MMT-Pol on the 6.5-m MMT. These observations allow us to study the torus from a magnetohydrodynamical (MHD) framework. In a 0.5 arcsec (30 pc) aperture at K′, we find that polarization arising from the passage of radiation from the inner edge of the torus through magnetically aligned dust grains in the clumps is the dominant polarization mechanism, with an intrinsic polarization of 7.0 ± 2.2 per cent. This result yields a torus magnetic field strength in the range of 4–82 mG through paramagnetic alignment, and 139+11−20−20+11 mG through the Chandrasekhar–Fermi method. The measured position angle (P.A.) of polarization at K′ is found to be similar to the P.A. of the obscuring dusty component at few parsec scales using infrared interferometric techniques. We show that the constant component of the magnetic field is responsible for the alignment of the dust grains, and aligned with the torus axis on to the plane of the sky. Adopting this magnetic field configuration and the physical conditions of the clumps in the MHD outflow wind model, we estimate a mass outflow rate ≤0.17 M⊙ yr−1 at 0.4 pc from the central engine for those clumps showing near-infrared dichroism. The models used were able to create the torus in a time-scale of ≥105 yr with a rotational velocity of ≤1228 km s−1 at 0.4 pc. We conclude that the evolution, morphology and kinematics of the torus in NGC 1068 can be explained within a MHD framework.ELR and CP acknowledge support from the University of Texas at San Antonio. CP acknowledges support from NSF-0904421 grant. CP and TJJ acknowledge support from NSF-0704095 grant. AA-H acknowledges financial support from the Spanish Plan Nacional de AstronomÃa y AstrofisÃca under grant AYA2012-31447. RN acknowledges support by FONDECYT grant No. 3140436. CRA is supported by a Marie Curie Intra European Fellowship within the 7th European Community Framework Programme
(PIEF-GA-2012-327934).Peer Reviewe
The complexity of parsec-scaled dusty tori in AGN
Warm gas and dust surround the innermost regions of active galactic nuclei
(AGN). They provide the material for accretion onto the super-massive black
hole and they are held responsible for the orientation-dependent obscuration of
the central engine. The AGN-heated dust distributions turn out to be very
compact with sizes on scales of about a parsec in the mid-infrared. Only
infrared interferometry currently provides the necessary angular resolution to
directly study the physical properties of this dust. Size estimates for the
dust distributions derived from interferometric observations can be used to
construct a size--luminosity relation for the dust distributions. The large
scatter about this relation suggests significant differences between the dust
tori in the individual galaxies, even for nuclei of the same class of objects
and with similar luminosities. This questions the simple picture of the same
dusty doughnut in all AGN. The Circinus galaxy is the closest Seyfert 2 galaxy.
Because its mid-infrared emission is well resolved interferometrically, it is a
prime target for detailed studies of its nuclear dust distribution. An
extensive new interferometric data set was obtained for this galaxy. It shows
that the dust emission comes from a very dense, disk-like structure which is
surrounded by a geometrically thick, similarly warm dust distribution as well
as significant amounts of warm dust within the ionisation cone.Comment: 8 pages, 3 figures, to appear in the proceedings of the conference
"The central kiloparsec in Galactic Nuclei: Astronomy at High Angular
Resolution 2011", open access Journal of Physics: Conference Series (JPCS),
published by IOP Publishin
Properties of dusty tori in active galactic nuclei - II. Type 2 AGN
(abridged) This paper is the second part of a work investigating the
properties of dusty tori in AGN by means of multi-component SED fitting. It
focuses on low luminosity, low redshift (z < 0.25) AGN selected among emission
line galaxies as well as X-ray, radio and mid-infrared selected type 2 AGN
samples from the literature. The available multi-band photometry covers the
spectral range from the u-band up to 160 um. The observed SED of each object is
fit to a set of multi-component models comprising a stellar component, a high
optical depth torus and cold emission from a starburst (SB). The contribution
of the various components (stars, torus, SB) is reflected in the position of
the objects on the IRAC colour diagram. The comparison of type 1 (as derived
from Hatziminaoglou et al. 2008) and type 2 AGN properties is broadly
consistent with the Unified Scheme. The estimated ratio between type 2 and type
1 objects is about 2-2.5:1. The AGN accretion-to-infrared luminosity ratio is
an indicator of the obscuration of the AGN since it scales down with the
covering factor. We find evidence supporting the receding torus paradigm, with
the estimated fraction of obscured AGN decreasing with increasing optical
luminosity over four orders of magnitude. The average star formation rates are
of ~ 10, 40 and 115 Mo/yr for the low-z, type 2 and quasar samples,
respectively; but this might simply reflect observational biases, as our
quasars are one to two orders of magnitude more luminous than the type 2 AGN.
For the majority of objects with 70 and/or 160 um detections an SB component
was needed in order to reproduce the data points, implying that the
far-infrared emission in AGN arises mostly from star formation; moreover, the
SB-to-AGN luminosity ratio shows a slight trend with increasing luminosity.Comment: 20 pages, 23 figures, accepted for publication in MNRAS; full
versions of tables 1-4 and Figs. 5, 14 and 15 only available as online
materia
The differences in the torus geometry between hidden and non-hidden broad line active galactic nuclei
arXiv:1501.06584v1We present results from the fitting of infrared (IR) spectral energy distributions of 21 active galactic nuclei (AGNs) with clumpy torus models. We compiled high spatial resolution (~0.3–0.7 arcsec) mid-IR (MIR) N-band spectroscopy, Q-band imaging, and nuclear near- and MIR photometry from the literature. Combining these nuclear near- and MIR observations, far-IR photometry, and clumpy torus models enables us to put constraints on the torus properties and geometry. We divide the sample into three types according to the broad line region (BLR) properties: type-1s, type-2s with scattered or hidden broad line region (HBLR) previously observed, and type-2s without any published HBLR signature (NHBLR). Comparing the torus model parameters gives us the first quantitative torus geometrical view for each subgroup. We find that NHBLR AGNs have smaller torus opening angles and larger covering factors than HBLR AGNs. This suggests that the chance to observe scattered (polarized) flux from the BLR in NHBLR could be reduced by the dual effects of (a) less scattering medium due to the reduced scattering volume given the small torus opening angle and (b) the increased torus obscuration between the observer and the scattering region. These effects give a reasonable explanation for the lack of observed HBLR in some type-2 AGNs.This work was partly supported by the Grant-inAid for JSPS Fellows for young researchers (K.I.). C.P. acknowledges support from UTSA and NSF (grant number
0904421). C.R.A. is supported by a Marie Curie Intra European Fellowship within the 7th European Community Framework Programme (PIEF-GA-2012-327934). A.A.-H.
acknowledges support from the Spanish Plan Nacional de Astronomia y Astrofisica under grant AYA2012-31447.Peer Reviewe
Investigation of nitrogen enriched silicon for particle detectors
This article explores the viability of nitrogen enriched silicon for particle physics application. For that purpose silicon diodes and strip sensors were produced using high resistivity float zone silicon, diffusion oxygenated float zone silicon, nitrogen enriched float zone silicon and magnetic Czochralski silicon. The article features comparative studies using secondary ion mass spectrometry, electrical characterization, edge transient current technique, source and thermally stimulated current spectroscopy measurements on sensors that were irradiated up to a fluence of 1015 neq/cm2. Irradiations were performed with 23 MeV protons at the facilities in Karlsruhe (KIT), with 24 GeV/c protons at CERN (PS-IRRAD) and neutrons at the research reactor in Ljubljana. Secondary ion mass spectrometry measurements give evidence for nitrogen loss after processing, which makes gaining from nitrogen enrichment difficult
The HELLAS2XMM survey. XIII. Multi-component analysis of the spectral energy distribution of obscured AGN
We combine near-to-mid-IR Spitzer data with shorter wavelength observations
(optical to X-rays) to get insights on the properties of a sample of luminous,
obscured Active Galactic Nuclei (AGN). We aim at modeling their broad-band
Spectral Energy Distributions (SEDs) in order to estimate the main parameters
related to the dusty torus. The sample comprises 16 obscured high-redshift
(0.9<z<2.1) xray luminous quasars (L_2-10 ~ 10^44 erg s-1) selected from the
HELLAS2XMM survey. The SEDs are described by a multi-component model including
a stellar component, an AGN component and a starburst. The majority (~80%) of
the sources show moderate optical depth (tau_9.7um<3) and the derived column
densities N_H are consistent with the xray inferred values (10^22 <N_H< 3x10^23
cm-2) for most of the objects, confirming that the sources are moderately
obscured Compton-thin AGN. Accretion luminosities in the range 5x10^44 < Lbol <
4x10^46 erg s-1 are inferred. We compare model luminosities with those obtained
by integrating the observed SED, finding that the latter are lower by a factor
of ~2 in the median. The discrepancy can be as high as an order of magnitude
for models with high optical depth (tau_9.7um=10). The ratio between the
luminosities obtained by the fitting procedure and from the observed SED
suggest that, at least for Type~2 AGN, observed bolometric luminosities are
likely to underestimate intrinsic ones and the effect is more severe for highly
obscured sources. Bolometric corrections from the hard X-ray band are computed
and have a median value of k_2-10kev ~ 20. The obscured AGN in our sample are
characterized by relatively low Eddington ratios (median lambda_Edd~0.08). On
average, they are consistent with the Eddington ratio increasing at increasing
bolometric correction (e.g. Vasudevan & Fabiam 2009).Comment: 16 pages, 10 figures. Accepted for pubblication in Astronomy and
Astrophysics
Dust Reverberation Mapping and Light-Curve Modelling of Zw229-015
Multiwavelength variability studies of active galactic nuclei (AGN) can be
used to probe their inner regions which are not directly resolvable. Dust
reverberation mapping (DRM) estimates the size of the dust emitting region by
measuring the delays between the infrared (IR) response to variability in the
optical light curves. We measure DRM lags of Zw229-015 between optical
ground-based and Kepler light curves and concurrent IR Spitzer 3.6 and 4.5
m light curves from 2010-2015, finding an overall mean rest-frame lag of
18.3 4.5 days. Each combination of optical and IR light curve returns
lags that are consistent with each other within 1, which implies that
the different wavelengths are dominated by the same hot dust emission. The lags
measured for Zw229-015 are found to be consistently smaller than predictions
using the lag-luminosity relationship. Also, the overall IR response to the
optical emission actually depends on the geometry and structure of the dust
emitting region as well, so we use Markov chain Monte Carlo (MCMC) modelling to
simulate the dust distribution to further estimate these structural and
geometrical properties. We find that a large increase in flux between the
2011-2012 observation seasons, which is more dramatic in the IR light curve, is
not well simulated by a single dust component. When excluding this increase in
flux, the modelling consistently suggests that the dust is distributed in an
extended flat disk, and finds a mean inclination angle of 49
degrees.Comment: 32 pages, 32 Figures, 7 Tables; Accepted for publication in MNRA
The HELLAS2XMM Survey. XII. The infrared/sub-millimeter view of an X-ray selected Type 2 quasar at z=2
We present multi-wavelength observations (from optical to sub-millimeter,
including Spitzer and SCUBA) of H2XMMJ 003357.2-120038 (also GD158_19), an
X-ray selected, luminous narrow-line (Type 2) quasar at z=1.957 selected from
the HELLAS2XMM survey. Its broad-band properties can be reasonably well modeled
assuming three components: a stellar component to account for the optical and
near-IR emission, an AGN component (i.e., dust heated by an accreting active
nucleus), dominant in the mid-IR, with an optical depth at 9.7 micron along the
line of sight (close to the equatorial plane of the obscuring matter) of
tau(9.7)=1 and a full covering angle of the reprocessing matter (torus) of 140
degrees, and a far-IR starburst component (i.e., dust heated by star formation)
to reproduce the wide bump observed longward of 70 micron. The derived
star-formation rate is about 1500 solar masses per year. The overall modeling
indicates that GD158_19 is a high-redshift X-ray luminous, obscured quasar with
coeval powerful AGN activity and intense star formation. It is probably caught
before the process of expelling the obscuring gas has started, thus quenching
the star formation.Comment: 7 pages, 3 figures, 1 table, accepted for publication by MNRA
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