341 research outputs found
Spoken content retrieval: A survey of techniques and technologies
Speech media, that is, digital audio and video containing spoken content, has blossomed in recent years. Large collections are accruing on the Internet as well as in private and enterprise settings. This growth has motivated extensive research on techniques and technologies that facilitate reliable indexing and retrieval. Spoken content retrieval (SCR) requires the combination of audio and speech processing technologies with methods from information retrieval (IR). SCR research initially investigated planned speech structured in document-like units, but has subsequently shifted focus to more informal spoken content produced spontaneously, outside of the studio and in conversational settings. This survey provides an overview of the field of SCR encompassing component technologies, the relationship of SCR to text IR and automatic speech recognition and user interaction issues. It is aimed at researchers with backgrounds in speech technology or IR who are seeking deeper insight on how these fields are integrated to support research and development, thus addressing the core challenges of SCR
Nuclear X-ray properties of the peculiar radio-loud hidden AGN 4C+29.30
We present results from a study of a nuclear emission of a nearby radio
galaxy, 4C+29.30, over a broad 0.5-200 keV X-ray band. This study used new
XMM-Newton (~17 ksec) and Chandra (~300 ksec) data, and archival Swift/BAT data
from the 58-month catalog. The hard (>2 keV) X-ray spectrum of 4C+29.30 can be
decomposed into an intrinsic hard power-law (Gamma ~ 1.56) modified by a cold
absorber with an intrinsic column density N_{H,z} ~ 5x10^{23} cm^{-2}, and its
reflection (|Omega/2pi| ~ 0.3) from a neutral matter including a narrow iron
Kalpha emission line at the rest frame energy ~6.4 keV. The reflected component
is less absorbed than the intrinsic one with an upper limit on the absorbing
column of N^{refl}_{H,z} < 2.5x10^{22} cm^{-2}. The X-ray spectrum varied
between the XMM-Newton and Chandra observations. We show that a scenario
invoking variations of the normalization of the power-law is favored over a
model with variable intrinsic column density. X-rays in the 0.5-2 keV band are
dominated by diffuse emission modeled with a thermal bremsstrahlung component
with temperature ~0.7 keV, and contain only a marginal contribution from the
scattered power-law component. We hypothesize that 4C+29.30 belongs to a class
of `hidden' AGN containing a geometrically thick torus. However, unlike the
majority of them, 4C+29.30 is radio-loud. Correlations between the scattering
fraction and Eddington luminosity ratio, and the one between black hole mass
and stellar velocity dispersion, imply that 4C+29.30 hosts a black hole with
~10^8 M_{Sun} mass.Comment: 13 pages, 5 figures, ApJ in pres
The Origin of the Silicate Emission Features in the Seyfert 2 Galaxy, NGC 2110
The unified model of active galactic nuclei (AGN) predicts silicate emission
features at 10 and 18 microns in type 1 AGN, and such features have now been
observed in objects ranging from distant QSOs to nearby LINERs. More
surprising, however, is the detection of silicate emission in a few type 2 AGN.
By combining Gemini and Spitzer mid-infrared imaging and spectroscopy of NGC
2110, the closest known Seyfert 2 galaxy with silicate emission features, we
can constrain the location of the silicate emitting region to within 32 pc of
the nucleus. This is the strongest constraint yet on the size of the silicate
emitting region in a Seyfert galaxy of any type. While this result is
consistent with a narrow line region origin for the emission, comparison with
clumpy torus models demonstrates that emission from an edge-on torus can also
explain the silicate emission features and 2-20 micron spectral energy
distribution of this object. In many of the best-fitting models the torus has
only a small number of clouds along the line of sight, and does not extend far
above the equatorial plane. Extended silicate-emitting regions may well be
present in AGN, but this work establishes that emission from the torus itself
is also a viable option for the origin of silicate emission features in active
galaxies of both type 1 and type 2.Comment: ApJL, accepte
Luminosity-variation independent location of the circum-nuclear, hot dust in NGC 4151
After recent sensitivity upgrades at the Keck Interferometer (KI), systematic
interferometric 2um studies of the innermost dust in nearby Seyfert nuclei are
within observational reach. Here, we present the analysis of new
interferometric data of NGC 4151, discussed in context of the results from
recent dust reverberation, spectro-photometric and interferometric campaigns.
The complete data set gives a complex picture, in particular the measured
visibilities from now three different nights appear to be rather insensitive to
the variation of the nuclear luminosity. KI data alone indicate two scenarios:
the K-band emission is either dominated to ~90% by size scales smaller than
30mpc, which falls short of any dust reverberation measurement in NGC 4151 and
of theoretical models of circum-nuclear dust distributions. Or contrary, and
more likely, the K-band continuum emission is dominated by hot dust (>= 1300K)
at linear scales of about 50mpc. The linear size estimate varies by a few tens
of percent depending on the exact morphology observed. Our interferometric,
deprojected centro-nuclear dust radius estimate of 55+-5mpc is roughly
consistent with the earlier published expectations from circum-nuclear, dusty
radiative transfer models, and spectro-photometric modeling. However, our data
do not support the notion that the dust emission size scale follows the nuclear
variability of NGC 4151 as a R_dust \propto L_nuc^0.5 scaling relation. Instead
variable nuclear activity, lagging, and variable dust response to illumination
changes need to be combined to explain the observations.Comment: 19 pages, 3 figures, 3 tables, accepted for publication in Ap
Gold Standard Online Debates Summaries and First Experiments Towards Automatic Summarization of Online Debate Data
Usage of online textual media is steadily increasing. Daily, more and more
news stories, blog posts and scientific articles are added to the online
volumes. These are all freely accessible and have been employed extensively in
multiple research areas, e.g. automatic text summarization, information
retrieval, information extraction, etc. Meanwhile, online debate forums have
recently become popular, but have remained largely unexplored. For this reason,
there are no sufficient resources of annotated debate data available for
conducting research in this genre. In this paper, we collected and annotated
debate data for an automatic summarization task. Similar to extractive gold
standard summary generation our data contains sentences worthy to include into
a summary. Five human annotators performed this task. Inter-annotator
agreement, based on semantic similarity, is 36% for Cohen's kappa and 48% for
Krippendorff's alpha. Moreover, we also implement an extractive summarization
system for online debates and discuss prominent features for the task of
summarizing online debate data automatically.Comment: accepted and presented at the CICLING 2017 - 18th International
Conference on Intelligent Text Processing and Computational Linguistic
The origin of the infrared emission in radio galaxies. III. Analysis of 3CRR objects
We present Spitzer photometric data for a complete sample of 19 low redshift
(z<0.1) 3CRR radio galaxies as part of our efforts to understand the origin of
the prodigious mid- to far-infrared (MFIR) emission from radio-loud AGN. Our
results show a correlation between AGN power (indicated by [OIII] 5007 emission
line luminosity) and 24 micron luminosity. This result is consistent with the
24 micron thermal emission originating from warm dust heated directly by AGN
illumination. Applying the same correlation test for 70 micron luminosity
against [OIII] luminosity we find this relation to suffer from increased
scatter compared to that of 24 micron. In line with our results for the
higher-radio-frequency-selected 2Jy sample, we are able to show that much of
this increased scatter is due to heating by starbursts which boost the
far-infrared emission at 70 micron in a minority of objects (17-35%). Overall
this study supports previous work indicating AGN illumination as the dominant
heating mechanism for MFIR emitting dust in the majority of low to intermediate
redshift radio galaxies (0.03<z<0.7), with the advantage of strong statistical
evidence. However, we find evidence that the low redshift broad-line objects
(z<0.1) are distinct in terms of their positions on the MFIR vs. [OIII]
correlations.Comment: 31 pages, 3 figures, accepted for publication to Ap
Smooth and Clumpy Dust Distribution in AGN: a Direct Comparison of two Commonly Explored Infrared Emission Models
The geometry of the dust distribution within the inner regions of Active
Galactic Nuclei (AGN) is still a debated issue and relates directly with the
AGN unified scheme. Traditionally, models discussed in the literature assume
one of two distinct dust distributions in what is believed to be a toroidal
region around the Supermassive Black Holes: a continuous distribution,
customarily referred to as smooth, and a concentration of dust in clumps or
clouds, referred to as clumpy.
In this paper we perform a thorough comparison between two of the most
popular models in the literature, namely the smooth models by Fritz. et al.
2006 and the clumpy models by Nenkova et al. 2008a, in their common parameters
space. Particular attention is paid to the silicate features at ~9.7 and ~18
micron, the width of the infrared bump, the near-infrared index and the
luminosity at 12.3 micron, all previously reported as possible diagnostic tools
to distinguish between the two dust distributions. We find that, due to the
different dust chemical compositions used in the two models, the behaviour of
the silicate features at 9.7 and 18 micron is quite distinct between the two
models. The width of the infrared bump and the peak of the infrared emission
can take comparable values, their distributions do, however, vary. The
near-infrared index is also quite different, due partly to the primary sources
adopted by the two models. Models with matched parameters do not produce
similar SEDs and virtually no random parameter combinations can result in
seemingly identical SEDs.Comment: 9 Pages, 6 Figures, 1 Table. Accepted for publication in MNRA
Learning the Visualness of Text Using Large Vision-Language Models
Visual text evokes an image in a person's mind, while non-visual text fails
to do so. A method to automatically detect visualness in text will enable
text-to-image retrieval and generation models to augment text with relevant
images. This is particularly challenging with long-form text as text-to-image
generation and retrieval models are often triggered for text that is designed
to be explicitly visual in nature, whereas long-form text could contain many
non-visual sentences. To this end, we curate a dataset of 3,620 English
sentences and their visualness scores provided by multiple human annotators. We
also propose a fine-tuning strategy that adapts large vision-language models
like CLIP by modifying the model's contrastive learning objective to map text
identified as non-visual to a common NULL image while matching visual text to
their corresponding images in the document. We evaluate the proposed approach
on its ability to (i) classify visual and non-visual text accurately, and (ii)
attend over words that are identified as visual in psycholinguistic studies.
Empirical evaluation indicates that our approach performs better than several
heuristics and baseline models for the proposed task. Furthermore, to highlight
the importance of modeling the visualness of text, we conduct qualitative
analyses of text-to-image generation systems like DALL-E. Project webpage:
https://gaurav22verma.github.io/text-visualness/Comment: Accepted at EMNLP 2023 (Main, long); 9 pages, 5 figure
AGN Dusty Tori: II. Observational Implications of Clumpiness
From extensive radiative transfer calculations we find that clumpy torus
models with \No \about 5--15 dusty clouds along radial equatorial rays
successfully explain AGN infrared observations. The dust has standard Galactic
composition, with individual cloud optical depth \tV \about 30--100 at visual.
The models naturally explain the observed behavior of the 10\mic silicate
feature, in particular the lack of deep absorption features in AGN of any type.
The weak 10\mic emission feature tentatively detected in type 2 QSO can be
reproduced if in these sources \No drops to \about 2 or \tV exceeds \about 100.
The clouds angular distribution must have a soft-edge, e.g., Gaussian profile,
the radial distribution should decrease as or . Compact tori can
explain all observations, in agreement with the recent interferometric evidence
that the ratio of the torus outer to inner radius is perhaps as small as \about
5--10. Clumpy torus models can produce nearly isotropic IR emission together
with highly anisotropic obscuration, as required by observations. In contrast
with strict variants of unification schemes where the viewing-angle uniquely
determines the classification of an AGN into type 1 or 2, clumpiness implies
that it is only a probabilistic effect; a source can display type 1 properties
even from directions close to the equatorial plane. The fraction of obscured
sources depends not only on the torus angular thickness but also on the cloud
number \No. The observed decrease of this fraction at increasing luminosity can
be explained with a decrease of either torus angular thickness or cloud number,
but only the latter option explains also the possible emergence of a 10\mic
emission feature in QSO2.Comment: To appear in ApJ September 20, 200
Detectability of low energy X-ray spectral components in type 1 AGN
In this paper we examine the percentage of type 1 AGN which require the
inclusion of a soft excess component and/or significant cold absorption in the
modelling of their X-ray spectra obtained by XMM-Newton. We do this by
simulating spectra which mimic typical spectral shapes in order to find the
maximum detectability expected at different count levels. We then apply a
correction to the observed percentages found for the Scott et al. (2011) sample
of 761 sources. We estimate the true percentage of AGN with a soft excess
component to be 75+/-23%, suggesting that soft excesses are ubiquitous in the
X-ray spectra of type 1 AGN. By carrying out joint fits on groups of low count
spectra in narrow z bins in which additional spectral components were not
originally detected, we show that the soft excess feature is recovered with a
mean temperature kT and blackbody to power-law normalisation ratio consistent
with those of components detected in individual high count spectra. Cold
absorption with nH values broadly consistent with those reported in individual
spectra are also recovered. We suggest such intrinsic cold absorption is found
in a minimum of ~5% of type 1 AGN and may be present in up to ~10%.Comment: 10 pages, 6 figures, 4 tables. Accepted for publication in MNRA
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