116 research outputs found
A Slight Excess of Large Scale Power from Moments of the Peculiar Velocity Field
The peculiar motions of galaxies can be used to infer the distribution of
matter in the Universe. It has recently been shown that measurements of the
peculiar velocity field indicates an anomalously high bulk flow of galaxies in
our local volume. In this paper we find the implications of the high bulk flow
for the power spectrum of density fluctuations. We find that analyzing only the
dipole moment of the velocity field yields an average power spectrum amplitude
which is indeed much higher than the LCDM value. However, by also including
shear and octupole moments of the velocity field, and marginalizing over
possible values for the growth rate, an average power spectrum amplitude which
is consistent with LCDM is recovered. We attempt to infer the shape of the
matter power spectrum from moments of the velocity field, and find a slight
excess of power on scales ~ h-1 Gpc.Comment: 6 pages,6 figures, updated to match accepted versio
The effects of velocities and lensing on moments of the Hubble diagram
We consider the dispersion on the supernova distance-redshift relation due to
peculiar velocities and gravitational lensing, and the sensitivity of these
effects to the amplitude of the matter power spectrum. We use the MeMo lensing
likelihood developed by Quartin, Marra & Amendola (2014), which accounts for
the characteristic non-Gaussian distribution caused by lensing magnification
with measurements of the first four central moments of the distribution of
magnitudes. We build on the MeMo likelihood by including the effects of
peculiar velocities directly into the model for the moments. In order to
measure the moments from sparse numbers of supernovae, we take a new approach
using Kernel Density Estimation to estimate the underlying probability density
function of the magnitude residuals. We also describe a bootstrap re-sampling
approach to estimate the data covariance matrix. We then apply the method to
the Joint Light-curve Analysis (JLA) supernova catalogue. When we impose only
that the intrinsic dispersion in magnitudes is independent of redshift, we find
at the one standard deviation level, although
we note that in tests on simulations, this model tends to overestimate the
magnitude of the intrinsic dispersion, and underestimate . We note
that the degeneracy between intrinsic dispersion and the effects of
is more pronounced when lensing and velocity effects are considered
simultaneously, due to a cancellation of redshift dependence when both effects
are included. Keeping the model of the intrinsic dispersion fixed as a Gaussian
distribution of width 0.14 mag, we find .Comment: 16 pages, updated to match version accepted in MNRA
Ultra-light Axions: Degeneracies with Massive Neutrinos and Forecasts for Future Cosmological Observations
A generic prediction of string theory is the existence of many axion fields.
It has recently been argued that many of these fields should be light and, like
the well known QCD axion, lead to observable cosmological consequences. In this
paper we study in detail the effect of the so-called string axiverse on large
scale structure, focusing on the morphology and evolution of density
perturbations, anisotropies in the cosmic microwave background and weak
gravitational lensing of distant galaxies. We quantify specific effects that
will arise from the presence of the axionic fields and highlight possible
degeneracies that may arise in the presence of massive neutrinos. We take
particular care understanding the different physical effects and scales that
come into play. We then forecast how the string axiverse may be constrained and
show that with a combination of different observations, it should be possible
to detect a fraction of ultralight axions to dark matter of a few percent.Comment: 24 pages, 16 figures, this version: corrected typos, some comments
added, matches published versio
NIR Spectroscopy of Star-Forming Galaxies at z~1.4 with Subaru/FMOS: The Mass-Metallicity Relation
We present near-infrared spectroscopic observations of star-forming galaxies
at z~1.4 with FMOS on the Subaru Telescope. We observed K-band selected
galaxies in the SXDS/UDS fields with K10^{9.5}
Msun, and expected F(Halpha)>10^{-16} erg s^{-1} cm^{-2}. 71 objects in the
sample have significant detections of Halpha. For these objects, excluding
possible AGNs identified from the BPT diagram, gas-phase metallicities are
obtained from [NII]/Halpha line ratio. The sample is split into three stellar
mass bins, and the spectra are stacked in each stellar mass bin. The
mass-metallicity relation obtained at z~1.4 is located between those at z~0.8
and z~2.2. We constrain an intrinsic scatter to be ~0.1 dex or larger in the
mass-metallicity relation at z~1.4; the scatter may be larger at higher
redshifts. We found trends that the deviation from the mass-metallicity
relation depends on the SFR and the half light radius: Galaxies with higher SFR
and larger half light radii show lower metallicities at a given stellar mass.
One possible scenario for the trends is the infall of pristine gas accreted
from IGM or through merger events. Our data points show larger scatter than the
fundamental metallicity relation (FMR) at z~0.1 and the average metallicities
slightly deviate from the FMR. The compilation of the mass-metallicity
relations at z~3 to z~0.1 shows that they evolve smoothly from z~3 to z~0
without changing the shape so much except for the massive part at z~0.Comment: 20 pages, 18 figures, accepted for publication in PAS
The Subaru-XMM-Newton Deep Survey (SXDS) VIII.: Multi-wavelength Identification, Optical/NIR Spectroscopic Properties, and Photometric Redshifts of X-ray Sources
We report the multi-wavelength identification of the X-ray sources found in
the Subaru-XMM-Newton Deep Survey (SXDS) using deep imaging data covering the
wavelength range between the far-UV to the mid-IR. We select a primary
counterpart of each X-ray source by applying the likelihood ratio method to
R-band, 3.6micron, near-UV, and 24micron source catalogs as well as matching
catalogs of AGN candidates selected in 1.4GHz radio and i'-band variability
surveys. Once candidates of Galactic stars, ultra-luminous X-ray sources in a
nearby galaxy, and clusters of galaxies are removed there are 896 AGN
candidates in the sample. We conduct spectroscopic observations of the primary
counterparts with multi-object spectrographs in the optical and NIR; 65\% of
the X-ray AGN candidates are spectroscopically-identified. For the remaining
X-ray AGN candidates, we evaluate their photometric redshift with photometric
data in 15 bands. Utilising the multi-wavelength photometric data of the large
sample of X-ray selected AGNs, we evaluate the stellar masses, M*, of the host
galaxies of the narrow-line AGNs. The distribution of the stellar mass is
remarkably constant from z=0.1 to 4.0. The relation between M* and 2--10 keV
luminosity can be explained with strong cosmological evolution of the
relationship between the black hole mass and M*. We also evaluate the scatter
of the UV-MIR spectral energy distribution (SED) of the X-ray AGNs as a
function of X-ray luminosity and absorption to the nucleus. The scatter is
compared with galaxies which have redshift and stellar mass distribution
matched with the X-ray AGN. The UV-NIR SEDs of obscured X-ray AGNs are similar
to those of the galaxies in the matched sample. In the NIR-MIR range, the
median SEDs of X-ray AGNs are redder, but the scatter of the SEDs of the X-ray
AGN broadly overlaps that of the galaxies in the matched sample.Comment: Accepted for publication in PASJ Subaru special issue. 42 pages, 22
figures. Entire contents of Tables 3, 8, 9, 10, and 11, and ASCII format
tables are available from
http://www.astr.tohoku.ac.jp/~akiyama/SXDS/index.htm
Ancestry of the Iban Is Predominantly Southeast Asian: Genetic Evidence from Autosomal, Mitochondrial, and Y Chromosomes
Humans reached present-day Island Southeast Asia (ISEA) in one of the first major human migrations out of Africa. Population movements in the millennia following this initial settlement are thought to have greatly influenced the genetic makeup of current inhabitants, yet the extent attributed to different events is not clear. Recent studies suggest that south-to-north gene flow largely influenced present-day patterns of genetic variation in Southeast Asian populations and that late Pleistocene and early Holocene migrations from Southeast Asia are responsible for a substantial proportion of ISEA ancestry. Archaeological and linguistic evidence suggests that the ancestors of present-day inhabitants came mainly from north-to-south migrations from Taiwan and throughout ISEA approximately 4,000 years ago. We report a large-scale genetic analysis of human variation in the Iban population from the Malaysian state of Sarawak in northwestern Borneo, located in the center of ISEA. Genome-wide single-nucleotide polymorphism (SNP) markers analyzed here suggest that the Iban exhibit greatest genetic similarity to Indonesian and mainland Southeast Asian populations. The most common non-recombining Y (NRY) and mitochondrial (mt) DNA haplogroups present in the Iban are associated with populations of Southeast Asia. We conclude that migrations from Southeast Asia made a large contribution to Iban ancestry, although evidence of potential gene flow from Taiwan is also seen in uniparentally inherited marker data
Discovery of a z = 0.65 post-starburst BAL quasar in the DES supernova fields
We present the discovery of a z = 0.65 low-ionization broad absorption line (LoBAL) quasar in a post-starburst galaxy in data from the Dark Energy Survey (DES) and spectroscopy from the Australian Dark Energy Survey (OzDES). LoBAL quasars are a minority of all BALs, and rarer still is that this object also exhibits broad Fe II (an FeLoBAL) and Balmer absorption. This is the first BAL quasar that has signatures of recently truncated star formation, which we estimate ended about 40 Myr ago. The characteristic signatures of an FeLoBAL require high column densities, which could be explained by the emergence of a young quasar from an early, dust-enshrouded phase, or by clouds compressed by a blast wave. The age of the starburst component is comparable to estimates of the lifetime of quasars, so if we assume the quasar activity is related to the truncation of the star formation, this object is better explained by the blast wave scenario
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