2,719 research outputs found
Foreword by guest editors for the Special Issue on the 2013 ICUFN Conferencs
Jeong, S.; Rodrigues, JJPC.; Cano Escribá, JC. (2014). Foreword by guest editors for the Special Issue on the 2013 ICUFN Conferencs. Wireless Personal Communications. 78(4):1827-1831. doi:10.1007/s11277-014-2046-yS1827183178
Infrared galaxies detected by the Atacama Cosmology Telescope
We report on 167 infrared (IR) galaxies selected by AKARI and IRAS and
detected in the Atacama Cosmology Telescope (ACT) Data Release 5 (DR5) sky maps
at the 98, 150 and 220 GHz frequency bands. Of these detections, 134 (80%) of
the millimeter counterparts are first-time identifications with ACT. We expand
the previous ACT extragalactic source catalogs, by including new 98 GHz
detections and measurements from ACT DR5. We also report flux density
measurements at the 98, 150, and 220 GHz frequency bands. We compute
, , and millimeter-wave
spectral indices and far-IR to millimeter-wave spectral indices between 90
micron and 98, 150, and 220 GHz. We specify the galaxy type, based on
. We combine publicly available multiwavelength
data-including ultraviolet, optical, near-IR, mid-IR, far-IR, and the
millimeter measurements obtained in this work-and perform spectral energy
distribution (SED) fitting with CIGALE. With the radio emission decomposition
advantage of CIGALE V2022.0, we identify the origins of the millimeter
emissions for 69 galaxies in our sample. Our analysis also shows that
millimeter data alone indicates the need for a radio synchrotron component in
the SEDs that are produced by active galactic nuclei (AGNs) and/or star
formation. We present SEDs and measured physical properties of these galaxies,
such as the dust luminosity, AGN luminosity, the total IR luminosity, and the
ratio of the IR and radio luminosity. We quantify the relationships between the
total IR luminosity and the millimeter-band luminosities, which can be used in
the absence of SED analysis.Comment: 29 pages, 6 tables, 11 figures, 1 appendix with 1 further figure.
Accepted for publication in ApJ
Future Constraints on Dark Matter with Gravitationally Lensed Fast Radio Bursts Detected by BURSTT
Understanding dark matter is one of the most urgent questions in modern
physics. A very interesting candidate is primordial black holes (PBHs;
Carr2016). For the mass ranges of ,
PBHs have been ruled out. However, they are still poorly constrained in the
mass ranges of (Belotsky et al. 2019). Fast radio
bursts (FRBs) are millisecond flashes of radio light of unknown origin mostly
from outside the Milky Way. Due to their short timescales, gravitationally
lensed FRBs, which are yet to be detected, have been proposed as a useful probe
for constraining the presence of PBHs in the mass window of
(Mu\~noz et al. 2016). Up to now, the most successful project in finding FRBs
has been CHIME. Due to its large field of view (FoV), CHIME is detecting at
least 600 FRBs since 2018. However, none of them is confirmed to be
gravitationally lensed (Leung et al. 2022). Taiwan plans to build a new
telescope, BURSTT dedicated to detecting FRBs. Its survey area will be 25 times
greater than CHIME. BURSTT can localize all of these FRBs through
very-long-baseline interferometry (VLBI). We estimate the probability to find
gravitationally lensed FRBs, based on the scaled redshift distribution from the
latest CHIME catalog and the lensing probability function from Mu\~noz et al.
(2016). BURSTT-2048 can detect ~ 24 lensed FRBs out of ~ 1,700 FRBs per annum.
With BURSTT's ability to detect nanosecond FRBs, we can constrain PBHs to form
a part of dark matter down to .Comment: Accepted for publication in ApJ. A summary video is available at this
https://youtu.be/yivrtvuMDH
Photometric Redshifts in the North Ecliptic Pole Wide Field based on a Deep Optical Survey with Hyper Suprime-Cam
The space infrared telescope has performed near- to mid-infrared
(MIR) observations on the North Ecliptic Pole Wide (NEPW) field (5.4 deg)
for about one year. took advantage of its continuous nine photometric
bands, compared with NASA's and WISE space telescopes, which had only
four filters with a wide gap in the MIR. The NEPW field lacked deep and
homogeneous optical data, limiting the use of nearly half of the IR sources for
extra-galactic studies owing to the absence of photometric redshifts
(photo-zs). To remedy this, we have recently obtained deep optical imaging over
the NEPW field with 5 bands (, , , , and ) of the Hyper
Suprime-Camera (HSC) on the Subaru 8m telescope. We optically identify AKARI-IR
sources along with supplementary and WISE data as well as
pre-existing optical data. In this work, we derive new photo-zs using a
template-fitting method code ( ) and reliable photometry
from 26 selected filters including HSC, , CFHT, Maidanak, KPNO,
and WISE data. We take 2026 spectroscopic redshifts (spec-z) from all
available spectroscopic surveys over the NEPW to calibrate and assess the
accuracy of the photo-zs. At z < 1.5, we achieve a weighted photo-z dispersion
of = 0.053 with = 11.3% catastrophic errors.Comment: 20 pages, 13 figures, accepted for publication in MNRAS. For summary
video, please see http://youtu.be/hjNJRCoBIg
On the relation between duration and energy of non-repeating fast radio bursts: census with the CHIME data
A correlation between the intrinsic energy and the burst duration of
non-repeating fast radio bursts (FRBs) has been reported. If it exists, the
correlation can be used to estimate intrinsic energy from the duration, and
thus can provide us with a new distance measure for cosmology. However, the
correlation suffered from small number statistics (68 FRBs) and was not free
from contamination by latent repeating populations, which might not have such a
correlation. How to separate/exclude the repeating bursts from the mixture of
all different types of FRBs is essential to see this property. Using a much
larger sample from the new FRB catalogue (containing 536 FRBs) recently
released by the CHIME/FRB project, combined with a new classification method
developed based on unsupervised machine learning, we carried out further
scrutiny of the relation. We found that there is a weak correlation between the
intrinsic energy and duration for non-repeating FRBs at z < 0.3 with Kendall's
tau correlation coefficient of 0.239 and significance of 0.001 (statistically
significant), whose slope looks similar to that of gamma-ray bursts. This
correlation becomes weaker and insignificant at higher redshifts (z > 0.3),
possibly due to the lack of the faint FRBs at high-z and/or the redshift
evolution of the correlation. The scattering time in the CHIME/FRB catalogue
shows an intriguing trend: it varies along the line obtained from linear fit on
the energy versus duration plane between these two parameters. A possible
cosmological application of the relation must wait for faint FRBs at high-z.Comment: 9 pages, 7 figures, accepted for publication in MNRA
Machine Learning Classification of Repeating FRBs from FRB121102
Fast Radio Bursts (FRBs) are mysterious bursts in the millisecond timescale
at radio wavelengths. Currently, there is little understanding about the
classification of repeating FRBs, based on difference in physics, which is of
great importance in understanding their origin. Recent works from the
literature focus on using specific parameters to classify FRBs to draw
inferences on the possible physical mechanisms or properties of these FRB
subtypes. In this study, we use publicly available 1652 repeating FRBs from
FRB121102 detected with the Five-hundred-meter Aperture Spherical Telescope
(FAST), and studied them with an unsupervised machine learning model. By
fine-tuning the hyperparameters of the model, we found that there is an
indication for four clusters from the bursts of FRB121102 instead of the two
clusters ("Classical" and "Atypical") suggested in the literature. Wherein, the
"Atypical" cluster can be further classified into three sub-clusters with
distinct characteristics. Our findings show that the clustering result we
obtained is more comprehensive not only because our study produced results
which are consistent with those in the literature but also because our work
uses more physical parameters to create these clusters. Overall, our methods
and analyses produced a more holistic approach in clustering the repeating FRBs
of FRB121102.Comment: 24 pages, 14 figure
Wide-Field Survey of Globular Clusters in M31. I. A Catalog of New Clusters
We present the result of a wide-field survey of globular clusters (GCs) in
M31 covering a 3deg x 3deg field c. We have searched for GCs on CCD images
taken with Washington CMT1 filters at the KPNO 0.9 m telescope using steps: (1)
inspection of morphological parameters given by the SExtractor package such as
stellarity, full maximum, and ellipticity; (2) consulting the spectral types
and radial velocities obtained from spectra takena spectrograph at the WIYN 3.5
m telescope; and (3) visual inspection of the images of each object. We have
and GC candidates, of which 605 are newly found GCs and GC candidates and 559
are previously known GCs. Amoects there are 113 genuine GCs, 258 probable GCs,
and 234 possible GCs, according to our classification critee known objects
there are 383 genuine GCs, 109 probable GCs, and 67 possible GCs. In total
there are 496 genprobable GCs and 301 possible GCs. Most of these newly found
GCs have T1 magnitudes of 17.5 - 19.5 mag, [17.9 < V < 19.9 mag assuming (C-T1)
~ 1.5], and (C-T1) colors in the range 1 - 2.Comment: accepted by AJ, using emulateapj.cl
Can luminous Lyman alpha emitters at 5.7 and 6.6 suppress star formation?
Addressing how strong UV radiation affects galaxy formation is central to
understanding their evolution. The quenching of star formation via strong UV
radiation (from starbursts or AGN) has been proposed in various scenes to solve
certain astrophysical problems. Around luminous sources, some evidence of
decreased star formation has been found but is limited to a handful of
individual cases. No direct, conclusive evidence on the actual role of strong
UV radiation in quenching star formation has been found. Here we present
statistical evidence of decreased number density of faint (AB magnitude
24.75 mag) Ly\alpha emitters (LAEs) around bright (AB magnitude < 24.75 mag)
LAEs even when the radius goes up to 10 pMpc for 5.7 LAEs. A
similar trend is found for z 6.6 LAEs but only within 1 pMpc radius
from the bright LAEs. We use a large sample of 1077 (962) LAEs at
5.7 ( 6.6) selected in total areas of 14 (21) deg with
Subaru/Hyper Suprime-Cam narrow-band data, and thus, the result is of
statistical significance for the first time at these high redshift ranges. A
simple analytical calculation indicates that the radiation from the central LAE
is not enough to suppress LAEs with AB mag 24.75 mag around them,
suggesting additional physical mechanisms we are unaware of are at work. Our
results clearly show that the environment is at work for the galaxy formation
at 6 in the Universe.Comment: Accepted for publication at MNRA
Galaxy Orbits for Galaxy Clusters in Sloan Digital Sky Survey and 2dF Galaxy Redshift Survey
We present the results of a study for galaxy orbits in galaxy clusters using
a spectroscopic sample of galaxies in Sloan Digital Sky Survey (SDSS) and 2dF
Galaxy Redshift Survey (2dFGRS). We have determined the member galaxies of
Abell clusters covered by these surveys using the galaxies' redshift and
positional data. We have selected 10 clusters using three criteria: the number
of member galaxies is greater than or equal to 40, the spatial coverage is
complete, and X-ray mass profile is available in the literature. We derive the
radial profile of the galaxy number density and velocity dispersion using all,
early-type, and late-type galaxies for each cluster. We have investigated the
galaxy orbits for our sample clusters with constant and variable velocity
anisotropies over the clustercentric distance using Jeans equation. Using all
member galaxies, the galaxy orbits are found to be isotropic within the
uncertainty for most of sample clusters, although it is difficult to conclude
strongly for some clusters due the large errors and the variation as a function
of the clustercentric distance in the calculated velocity anisotropies. We
investigated the orbital difference between early-type and late-type galaxies
for four sample clusters, and found no significant difference between them.Comment: 59 pages, 21 figures. To appear in ApJ. Paper with high resolution
figures are available at http://astro.kias.re.kr/~hshwang/papers/orbit.pd
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