343 research outputs found
The effect of distraction on change detection in crowded acoustic scenes
In this series of behavioural experiments we investigated the effect of distraction on the maintenance of acoustic scene information in short-term memory. Stimuli are artificial acoustic âscenesâ composed of several (up to twelve) concurrent tone-pip streams (âsourcesâ). A gap (1000 ms) is inserted partway through the âsceneâ; Changes in the form of an appearance of a new source or disappearance of an existing source, occur after the gap in 50% of the trials. Listeners were instructed to monitor the unfolding âsoundscapesâ for these events. Distraction was measured by presenting distractor stimuli during the gap. Experiments 1 and 2 used a dual task design where listeners were required to perform a task with varying attentional demands (âHigh Demandâ vs. âLow Demandâ) on brief auditory (Experiment 1a) or visual (Experiment 1b) signals presented during the gap. Experiments 2 and 3 required participants to ignore distractor sounds and focus on the change detection task. Our results demonstrate that the maintenance of scene information in short-term memory is influenced by the availability of attentional and/or processing resources during the gap, and that this dependence appears to be modality specific. We also show that these processes are susceptible to bottom up driven distraction even in situations when the distractors are not novel, but occur on each trial. Change detection performance is systematically linked with the, independently determined, perceptual salience of the distractor sound. The findings also demonstrate that the present task may be a useful objective means for determining relative perceptual salience
Detection of appearing and disappearing objects in complex acoustic scenes.
The ability to detect sudden changes in the environment is critical for survival. Hearing is hypothesized to play a major role in this process by serving as an "early warning device," rapidly directing attention to new events. Here, we investigate listeners' sensitivity to changes in complex acoustic scenes-what makes certain events "pop-out" and grab attention while others remain unnoticed? We use artificial "scenes" populated by multiple pure-tone components, each with a unique frequency and amplitude modulation rate. Importantly, these scenes lack semantic attributes, which may have confounded previous studies, thus allowing us to probe low-level processes involved in auditory change perception. Our results reveal a striking difference between "appear" and "disappear" events. Listeners are remarkably tuned to object appearance: change detection and identification performance are at ceiling; response times are short, with little effect of scene-size, suggesting a pop-out process. In contrast, listeners have difficulty detecting disappearing objects, even in small scenes: performance rapidly deteriorates with growing scene-size; response times are slow, and even when change is detected, the changed component is rarely successfully identified. We also measured change detection performance when a noise or silent gap was inserted at the time of change or when the scene was interrupted by a distractor that occurred at the time of change but did not mask any scene elements. Gaps adversely affected the processing of item appearance but not disappearance. However, distractors reduced both appearance and disappearance detection. Together, our results suggest a role for neural adaptation and sensitivity to transients in the process of auditory change detection, similar to what has been demonstrated for visual change detection. Importantly, listeners consistently performed better for item addition (relative to deletion) across all scene interruptions used, suggesting a robust perceptual representation of item appearance
The FMOS-COSMOS survey of star-forming galaxies at z ~ 1.6. I. H\alpha -based star formation rates and dust extinction
We present the first results from a near-IR spectroscopic survey of the
COSMOS field, using the Fiber Multi-Object Spectrograph on the Subaru
telescope, designed to characterize the star-forming galaxy population at
. The high-resolution mode is implemented to detect H in
emission between with erg cm s. Here, we specifically
focus on 271 sBzK-selected galaxies that yield a H detection thus
providing a redshift and emission line luminosity to establish the relation
between star formation rate and stellar mass. With further -band
spectroscopy for 89 of these, the level of dust extinction is assessed by
measuring the Balmer decrement using co-added spectra. We find that the
extinction () rises with stellar
mass and is elevated at high masses compared to low-redshift galaxies. Using
this subset of the spectroscopic sample, we further find that the differential
extinction between stellar and nebular emission
\hbox{} is 0.7--0.8, dissimilar to
that typically seen at low redshift. After correcting for extinction, we derive
an H-based main sequence with a slope () and normalization
similar to previous studies at these redshifts.Comment: 6 pages, 4 figures, and 1 table. Published in ApJ Letter
Fabrication of field-effect transistor device with higher fullerene, C<sub>88</sub>
A fullerene field-effect transistor (FET) device has been fabricated with thin films of C88, and n-channel normally-on depletion-type FET properties have been found in this FET device. The C88 FET exhibited a high mobility, μ, of 2.5 x 10-3 cm2 V-1 s-1 at 300 K, in fullerene FETs. The carrier transport showed a thermally-activated hopping transport. The n-channel normally-on FET properties and the hopping transport reflect the small mobility gap and low carrier concentration in the channel region of C88 thin-films.</p
Identifying Ly{\alpha} emitter candidates with Random Forest: learning from galaxies in CANDELS survey
The physical processes which make a galaxy a Lyman Alpha Emitter have been
extensively studied for the past 25 years. However, the correlations between
physical and morphological properties of galaxies and the strength of the
Ly emission line are still highly debated. Therefore, we investigate
the correlations between the rest-frame Ly equivalent width and stellar
mass, star formation rate, dust reddening, metallicity, age, half-light
semi-major axis, S\'ersic index and projected axis ratio in a sample of 1578
galaxies in the redshift range from the GOODS-S, UDS and
COSMOS fields. From the large sample of Ly emitters (LAEs) in the
dataset we find that LAEs are typically common main sequence star forming
galaxies which show stellar mass , star formation
rate , and
half-light semi-major axis . Building on these findings we
develop a new method based on Random Forest (i.e. a Machine Learning
classifier) in order to select galaxies which have the highest probability of
being Ly emitters. When applied to a population in the redshift range
, our classifier holds a accuracy and precision. At higher redshifts (), we obtain a
accuracy and a precision. These results highlight it is possible to
overcome the current limitations in assembling large samples of LAEs by making
informed predictions that can be used for planning future large scale
spectroscopic surveys.Comment: Accepted for publication in the 4. Extragalactic astronomy section of
Astronomy & Astrophysics, 13 pages, 13 figure
The FMOS-COSMOS survey of star-forming galaxies at z~1.6 III. Survey design, performance, and sample characteristics
We present a spectroscopic survey of galaxies in the COSMOS field using the
Fiber Multi-Object Spectrograph (FMOS), a near-infrared instrument on the
Subaru Telescope. Our survey is specifically designed to detect the Halpha
emission line that falls within the H-band (1.6-1.8 um) spectroscopic window
from star-forming galaxies with 1.4 ~10^10 Msolar. With
the high multiplex capability of FMOS, it is now feasible to construct samples
of over one thousand galaxies having spectroscopic redshifts at epochs that
were previously challenging. The high-resolution mode (R~2600) effectively
separates Halpha and [NII]6585 thus enabling studies of the gas-phase
metallicity and photoionization state of the interstellar medium. The primary
aim of our program is to establish how star formation depends on stellar mass
and environment, both recognized as drivers of galaxy evolution at lower
redshifts. In addition to the main galaxy sample, our target selection places
priority on those detected in the far-infrared by Herschel/PACS to assess the
level of obscured star formation and investigate, in detail, outliers from the
star formation rate - stellar mass relation. Galaxies with Halpha detections
are followed up with FMOS observations at shorter wavelengths using the J-long
(1.11-1.35 um) grating to detect Hbeta and [OIII]5008 that provides an
assessment of extinction required to measure star formation rates not hampered
by dust, and an indication of embedded Active Galactic Nuclei. With 460
redshifts measured from 1153 spectra, we assess the performance of the
instrument with respect to achieving our goals, discuss inherent biases in the
sample, and detail the emission-line properties. Our higher-level data
products, including catalogs and spectra, are available to the community.Comment: 26 pages, Updated version resubmitted to ApJSS; Data products and
catalogs are now available at http://member.ipmu.jp/fmos-cosmos
The FMOS-COSMOS survey of star-forming galaxies at z~1.6. IV: Excitation state and chemical enrichment of the interstellar medium
We investigate the physical conditions of ionized gas in high-z star-forming
galaxies using diagnostic diagrams based on the rest-frame optical emission
lines. The sample consists of 701 galaxies with an Ha detection at , from the FMOS-COSMOS survey, that represent the normal
star-forming population over the stellar mass range with those at being
well sampled. We confirm an offset of the average location of star-forming
galaxies in the BPT diagram ([OIII]/Hb vs. [NII]/Ha), primarily towards higher
[OIII]/Hb, compared with local galaxies. Based on the [SII] ratio, we measure
an electron density (), that is higher
than that of local galaxies. Based on comparisons to theoretical models, we
argue that changes in emission-line ratios, including the offset in the BPT
diagram, are caused by a higher ionization parameter both at fixed stellar mass
and at fixed metallicity with additional contributions from a higher gas
density and possibly a hardening of the ionizing radiation field. Ionization
due to AGNs is ruled out as assessed with Chandra. As a consequence, we revisit
the mass-metallicity relation using [NII]/Ha and a new calibration including
[NII]/[SII] as recently introduced by Dopita et al. Consistent with our
previous results, the most massive galaxies ()
are fully enriched, while those at lower masses have metallicities lower than
local galaxies. Finally, we demonstrate that the stellar masses, metallicities
and star formation rates of the FMOS sample are well fit with a
physically-motivated model for the chemical evolution of star-forming galaxies.Comment: 38 pages; Accepted for publication in Ap
Predicting emission line fluxes and number counts of distant galaxies for cosmological surveys
open12siWe estimate the number counts of line emitters at high redshift and their evolution with cosmic time based on a combination of photometry and spectroscopy. We predict the H α, H ÎČ, [O II], and [O III] line fluxes for more than 35 000 galaxies down to stellar masses of âŒ109 Mâ in the COSMOS and GOODS-S fields, applying standard conversions and exploiting the spectroscopic coverage of the FMOS-COSMOS survey at z ⌠1.55 to calibrate the predictions. We calculate the number counts of H α, [O II], and [O III] emitters down to fluxes of 1 Ă 10-17 erg cm-2 s-1 in the range 1.4 < z < 1.8 covered by the FMOS-COSMOS survey. We model the time evolution of the differential and cumulative H α counts, steeply declining at the brightest fluxes. We expect âŒ9300-9700 and âŒ2300-2900 galaxies deg-2 for fluxes â„1 Ă 10-16 and â„2 Ă 10-16 erg cm-2 s-1 over the range of 0.9 < z < 1.8. We show that the observed evolution of the main sequence of galaxies with redshift is enough to reproduce the observed counts variation at 0.2 < z < 2.5. We characterize the physical properties of the H α emitters with fluxes â„2 Ă 10-16 erg cm-2 s-1 including their stellar masses, UV sizes, [N II]/H α ratios and H α equivalent widths. An aperture of R ⌠Re ⌠0.5 arcsec maximizes the signal-to-noise ratio for a detection, whilst causing a factor of âŒ2 Ă flux losses, influencing the recoverable number counts, if neglected. Our approach, based on deep and large photometric data sets, reduces the uncertainties on the number counts due to the selection and spectroscopic samplings whilst exploring low fluxes. We publicly release the line flux predictions for the explored photometric samples.mixedopenValentino, F.; Daddi, E.; Silverman, J. D.; Puglisi, A.; Kashino, D.; Renzini, A.; Cimatti, A.; Pozzetti, L.; Rodighiero, G.; Pannella, M.; Gobat, R.; Zamorani, G.Valentino, F.; Daddi, E.; Silverman, J. D.; Puglisi, A.; Kashino, D.; Renzini, A.; Cimatti, A.; Pozzetti, L.; Rodighiero, G.; Pannella, M.; Gobat, R.; Zamorani, G
Spatial Periodicity of Galaxy Number Counts, CMB Anisotropy, and SNIa Hubble Diagram Based on the Universe Accompanied by a Non-Minimally Coupled Scalar Field
We have succeeded in establishing a cosmological model with a non-minimally
coupled scalar field that can account not only for the spatial
periodicity or the {\it picket-fence structure} exhibited by the galaxy -
relation of the 2dF survey but also for the spatial power spectrum of the
cosmic microwave background radiation (CMB) temperature anisotropy observed by
the WMAP satellite. The Hubble diagram of our model also compares well with the
observation of Type Ia supernovae. The scalar field of our model universe
starts from an extremely small value at around the nucleosynthesis epoch,
remains in that state for sufficiently long periods, allowing sufficient time
for the CMB temperature anisotropy to form, and then starts to grow in
magnitude at the redshift of , followed by a damping oscillation
which is required to reproduce the observed picket-fence structure of the
- relation. To realize such behavior of the scalar field, we have found
it necessary to introduce a new form of potential , with being a constant. Through this parameter ,
we can control the epoch at which the scalar field starts growing.Comment: 19 pages, 18 figures, Accepted for publication in Astrophysics &
Space Scienc
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