21 research outputs found
The Inhomogeneous Universe: Dark Matter, Gravitational Lensing, and 21cm Polarization
The Big-Bang Theory is successful in interpreting the majority of cosmological observations, while also leaving intriguing puzzles about itself. Here, my graduate work is presented in four parts, addressing some of these interesting questions from different angles.
In the first part, we focus on gravitational lensing by dark matter. We first search for lensing signatures by compact dark matter in gamma-ray bursts. We then provide a numerical approach to evaluate the diffraction integral needed in searching the lensing of gravitational waves in the wave-optics regime.
In the second part, we focus on dark matter models and inflation. We first propose a wave-dark-matter model with non-minimal coupling to gravity and derive some phenomenological implications of the model. We then discuss constraints to a class of ``WIMPflation'' models by requiring a physically reasonable era of reheating.
In the third part, we focus on the polarization of the cosmic 21cm signal. We first discuss the linear polarization and its cross-correlation with the linear polarization of the cosmic microwave background. We then calculate the circular-polarization angular power spectrum predicted by the standard cosmological model.
In the final part, we propose a new numerical scheme to solve the cosmological-perturbation equations, where the neutrino (or non-cold dark matter) perturbations are described by a small set of integral equations, evolved by an iterative scheme. We demonstrate how the integral-equation sector can be accelerated by the fast Fourier transform. We also discuss the advantages of this approach when used in conjunction with parameter-extraction code
Cross-correlation of the Polarizations of the 21-cm and Cosmic Microwave Backgrounds
The polarization of the 21-cm radiation from the epoch of reionization arises
from Thomson scattering of 21-cm photons from free electrons and provides
information that complements that from the intensity fluctuation. Previous work
showed that a direct detection of this signal will be difficult, and hinted
that the signal might be enhanced via correlation with other tracers. Here, we
discuss the cross-correlation between the cosmic microwave background (CMB)
polarization and the 21-cm polarization. We treat reionization using an
analytical model with parameters calibrated by semi-numerical simulations. We
then derive the cross-correlation angular power spectrum using the
total-angular-momentum formalism. We also provide a noise analysis to test
against two closely related, but subtly different, null hypotheses. First, we
assume no reionization as a null hypothesis, and determine how well this null
hypothesis could be ruled out by an observed 21cm-CMB polarization correlation.
Second, we determine how well the null hypothesis of no 21-cm polarization can
be ruled out by seeking the cross-correlation, assuming reionization is
established from the CMB. We find that the first question could be answered by
a synergy of ambitious next-generation 21-cm and CMB missions, whereas the
second question will still remain out of reach.Comment: 9 pages, 3 figure
Probing wave-optics effects and dark-matter subhalos with lensing of gravitational waves from massive black holes
The Laser Interferometer Space Antenna (LISA) will detect gravitational waves
(GWs) emitted by massive black hole binaries (MBHBs) in the low-frequency
(mHz) band. Low-mass lenses, such as dark-matter (DM) subhalos, have
sizes comparable to the wavelength of these GWs. Encounters with these lenses
produce wave-optics (WO) effects that alter waveform phase and amplitude. Thus,
a single event with observable WO effects can be used to probe the lens
properties. In this paper, we first compute the probability of observing WO
effects in a model-agnostic way. We perform parameter estimation over
approximately 1000 MBHBs with total mass, mass ratio, and redshift spanning the
ranges relevant to LISA. We then calculate lensing rates using three
semi-analytical models of MBHB populations. In both cases, we use a waveform
model that includes merger, ringdown, and higher-order modes. We use two lens
population models: the theory-based Press-Schechter halo mass function and an
observation-based model derived from Sloan Digital Sky Survey, called the
measured velocity function. We find that the probability of detecting WO
effects can be as large as , , and at
, , and confidence levels, respectively. The most
optimistic MBHB population model yields , , and events
at the same confidence levels, while the rates drop to in the more
pessimistic scenarios. The most likely lens masses probed by LISA are in the
range , and the most probable redshifts are in the
range . Therefore, LISA observations of WO effects can probe DM
subhalos, complementing strong lensing and other observations.Comment: 24 pages, 15 figures. Comments are welcom
DNAH17 is associated with asthenozoospermia and multiple morphological abnormalities of sperm flagella.
BACKGROUND(#br)Multiple morphological abnormalities of the sperm flagella (MMAF) is one kind of severe asthenozoospermia, which is caused by dysplastic development of sperm flagella. In our study, we sought to investigate the novel gene mutations leading to severe asthenozoospermia and MMAF.(#br)METHODS AND MATERIALS(#br)The patient’s spermatozoa were tested by Papanicolaou staining and transmission electron microscopy. Whole exome sequencing was performed on the patient with severe asthenozoospermia and MMAF. Sanger sequencing verified the mutations in the family. The expression of DNAH17 was detected by immunofluorescence and Western blot.(#br)RESULTS(#br)Spermatozoa sample from the patient showed severe asthenozoospermia and MMAF. We detected biallelic mutations (c.C4445T, p.A1482V and c.C6857T, and p.S2286L) in DNAH17 (MIM:610063). The protein expression of DNAH17 was almost undetectable in spermatozoa from the patient with the biallelic mutations.(#br)CONCLUSION(#br)These results demonstrated that DNAH17 may be involved in severe asthenozoospermia and MMAF
BUFFALO/Flashlights: Constraints on the abundance of lensed supergiant stars in the Spock galaxy at redshift 1
In this work, we present a constraint on the abundance of supergiant (SG) stars at redshift z ≈ 1, based on recent observations of astrongly lensed arc at this redshift. First we derived a free-form model of MACS J0416.1-2403 using data from the Beyond Ultradeep Frontier Fields and Legacy Observations (BUFFALO) program. The new lens model is based on 72 multiply lensed galaxies thatproduce 214 multiple images, making it the largest sample of spectroscopically confirmed lensed galaxies on this cluster. The largercoverage in BUFFALO allowed us to measure the shear up to the outskirts of the cluster, and extend the range of lensing constraintsup to ∼1 Mpc from the central region, providing a mass estimate up to this radius. As an application, we make predictions for thenumber of high-redshift multiply lensed galaxies detected in future observations with the James Webb Space Telescope (JWST).Then we focus on a previously known lensed galaxy at z = 1.0054, nicknamed Spock, which contains four previously reportedtransients. We interpret these transients as microcaustic crossings of SG stars and explain how we computed the probability of suchevents. Based on simplifications regarding the stellar evolution, we find that microlensing (by stars in the intracluster medium) ofSG stars at z = 1.0054 can fully explain these events. The inferred abundance of SG stars is consistent with either (1) a numberdensity of stars with bolometric luminosities beyond the Humphreys-Davidson (HD) limit (Lmax ≈ 6 × 105 L for red stars), whichis below ∼400 stars kpc−2, or (2) the absence of stars beyond the HD limit but with a SG number density of ∼9000 kpc−2 for starswith luminosities between 105 L and 6 × 105 L. This is equivalent to one SG star per 10 × 10 pc2. Finally, we make predictions forfuture observations with JWST’s NIRcam. We find that in observations made with the F200W filter that reach 29 mag AB, if cool red SG stars exist at z ≈ 1 beyond the HD limit, they should be easily detected in this arc
BUFFALO/Flashlights: Constraints on the abundance of lensed supergiant stars in the Spock galaxy at redshift 1
We present a constraint on the abundance of supergiant (SG) stars at redshift
z approx. 1, based on recent observations of a strongly lensed arc at this
redshift. First we derive a free-form model of MACS J0416.1-2403 using data
from the BUFFALO program. The new lens model is based on 72 multiply lensed
galaxies that produce 214 multiple images, making it the largest sample of
spectroscopically confirmed lensed galaxies on this cluster. The larger
coverage in BUFFALO allows us to measure the shear up to the outskirts of the
cluster, and extend the range of lensing constraints up to ~ 1 Mpc from the
central region, providing a mass estimate up to this radius. As an application,
we make predictions for the number of high-redshift multiply-lensed galaxies
detected in future observations with JWST. Then we focus on a previously known
lensed galaxy at z=1.0054, nicknamed Spock, which contains four previously
reported transients. We interpret these transients as microcaustic crossings of
SG stars and compute the probability of such events. Based on simplifications
regarding the stellar evolution, we find that microlensing (by stars in the
intracluster medium) of SG stars at z=1.0054 can fully explain these events.
The inferred abundance of SG stars is consistent with either (1) a number
density of stars with bolometric luminosities beyond the Humphreys-Davidson
(HD) limit (L ~ ) that is below 400 stars per sq. kpc,
or (2) the absence of stars beyond the HD limit but with a SG number density of
~ 9000 per sq. kpc for stars with luminosities between and
. This is equivalent to one SG star per 10x10 pc. We finally
make predictions for future observations with JWST's NIRcam. We find that in
observations made with the F200W filter that reach 29 mag AB, if cool red SG
stars exist at z~1 beyond the HD limit, they should be easily detected in this
arcComment: 24 pages & 18 figure