10,713 research outputs found
A Foreground Masking Strategy for [CII] Intensity Mapping Experiments Using Galaxies Selected by Stellar Mass and Redshift
Intensity mapping provides a unique means to probe the epoch of reionization
(EoR), when the neutral intergalactic medium was ionized by the energetic
photons emitted from the first galaxies. The [CII] 158m fine-structure
line is typically one of the brightest emission lines of star-forming galaxies
and thus a promising tracer of the global EoR star-formation activity. However,
[CII] intensity maps at are contaminated by
interloping CO rotational line emission () from
lower-redshift galaxies. Here we present a strategy to remove the foreground
contamination in upcoming [CII] intensity mapping experiments, guided by a
model of CO emission from foreground galaxies. The model is based on empirical
measurements of the mean and scatter of the total infrared luminosities of
galaxies at
selected in -band from the COSMOS/UltraVISTA survey, which can be converted
to CO line strengths. For a mock field of the Tomographic Ionized-carbon
Mapping Experiment (TIME), we find that masking out the "voxels"
(spectral-spatial elements) containing foreground galaxies identified using an
optimized CO flux threshold results in a -dependent criterion (or ) at and makes a [CII]/CO power ratio of at
/Mpc achievable, at the cost of a moderate loss of total
survey volume.Comment: 14 figures, 4 tables, re-submitted to ApJ after addressing reviewer's
comments. Comments welcom
Simultaneous Dual Frequency Observations of Giant Pulses from the Crab Pulsar
Simultaneous measurements of giant pulses from the Crab pulsar were taken at
two widely spaced frequencies using the real-time detection of a giant pulse at
1.4 GHz at the Very Large Array to trigger the observation of that same pulse
at 0.6 GHz at a 25-m telescope in Green Bank, WV. Interstellar dispersion of
the signals provided the necessary time to communicate the trigger across the
country via the Internet. About 70% of the pulses are seen at both 1.4 GHz and
0.6 GHz, implying an emission mechanism bandwidth of at least 0.8 GHz at 1 GHz
for pulse structure on time scales of one to ten microseconds.
The arrival times at both frequencies display a jitter of 100 microseconds
within the window defined by the average main pulse profile and are tightly
correlated. This tight correlation places limits on both the emission mechanism
and on frequency dependent propagation within the magnetosphere.
At 1.4 GHz the giant pulses are resolved into several, closely spaced
components. Simultaneous observations at 1.4 GHz and 4.9 GHz show that the
component splitting is frequency independent. We conclude that the multiplicity
of components is intrinsic to the emission from the pulsar, and reject the
hypothesis that this is the result of multiple imaging as the signal propagates
through the perturbed thermal plasma in the surrounding nebula. At both 1.4 GHz
and 0.6 GHz the pulses are characterized by a fast rise time and an exponential
decay time which are correlated. The pulse broadening with its exponential
decay form is most likely the result of multipath propagation in intervening
ionized gas.Comment: LaTeX, 18 pages, 7 figures, accepted for publication in The
Astrophysical Journa
Broad-band spectrophotometry of the hot Jupiter HAT-P-12b from the near-UV to the near-IR
The detection of trends or gradients in the transmission spectrum of
extrasolar planets is possible with observations at very low spectral
resolution. Transit measurements of sufficient accuracy using selected
broad-band filters allow for an initial characterization of the atmosphere of
the planet. We obtained time series photometry of 20 transit events and
analyzed them homogeneously, along with eight light curves obtained from the
literature. In total, the light curves span a range from 0.35 to 1.25 microns.
During two observing seasons over four months each, we monitored the host star
to constrain the potential influence of starspots on the derived transit
parameters. We rule out the presence of a Rayleigh slope extending over the
entire optical wavelength range, a flat spectrum is favored for HAT-P-12b with
respect to a cloud-free atmosphere model spectrum. A potential cause of such
gray absorption is the presence of a cloud layer at the probed latitudes.
Furthermore, in this work we refine the transit parameters, the ephemeris and
perform a TTV analysis in which we found no indication for an unseen companion.
The host star showed a mild non-periodic variability of up to 1%. However, no
stellar rotation period could be detected to high confidence.Comment: 13 pages, 6 figures, Accepted for publication in A&
Effects of Mirror Aberrations on Laguerre-Gaussian Beams in Interferometric Gravitational-Wave Detectors
A fundamental limit to the sensitivity of optical interferometers is imposed
by Brownian thermal fluctuations of the mirrors' surfaces. This thermal noise
can be reduced by using larger beams which "average out" the random
fluctuations of the surfaces. It has been proposed previously that wider,
higher-order Laguerre-Gaussian modes can be used to exploit this effect. In
this article, we show that susceptibility to spatial imperfections of the
mirrors' surfaces limits the effectiveness of this approach in interferometers
used for gravitational-wave detection. Possible methods of reducing this
susceptibility are also discussed.Comment: 10 pages, 11 figure
Gravitational Radiation Detection with Laser Interferometry
Gravitational-wave detection has been pursued relentlessly for over 40 years.
With the imminent operation of a new generation of laser interferometers, it is
expected that detections will become a common occurrence. The research into
more ambitious detectors promises to allow the field to move beyond detection
and into the realm of precision science using gravitational radiation. In this
article, I review the state of the art for the detectors and describe an
outlook for the coming decades.Comment: 38 pages typos, references update
TASTE. III. A homogeneous study of transit time variations in WASP-3b
The TASTE project is searching for low-mass planets with the Transit Timing
Variation (TTV) technique, by gathering high-precision, short-cadence light
curves for a selected sample of transiting exoplanets. It has been claimed that
the "hot Jupiter" WASP-3b could be perturbed by a second planet. Presenting
eleven new light curves (secured at the IAC80 and UDEM telescopes) and
re-analyzing thirty-eight archival light curves in a homogeneous way, we show
that new data do not confirm the previously claimed TTV signal. However, we
bring evidence that measurements are not consistent with a constant orbital
period, though no significant periodicity can be detected. Additional dynamical
modeling and follow-up observations are planned to constrain the properties of
the perturber or to put upper limits to it. We provide a refined ephemeris for
WASP-3b and improved orbital/physical parameters. A contact eclipsing binary,
serendipitously discovered among field stars, is reported here for the first
time.Comment: 10 pages, 6 figures, 4 tables; accepted for publication in A&
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