9,425 research outputs found
Inhomogenized sudden future singularities
We find that sudden future singularities may also appear in spatially
inhomogeneous Stephani models of the universe. They are temporal pressure
singularities and may appear independently of the spatial finite density
singularities already known to exist in these models. It is shown that the main
advantage of the homogeneous sudden future singularities which is the
fulfillment of the strong and weak energy conditions may not be the case for
inhomogeneous models.Comment: REVTEX 4, 5 pages, no figures, a discussion of the most general case
include
Meandering periods and asymmetries in light curves of Miras: Observational evidence for low mass-loss rates
Some Miras -- long-period variables in late evolutionary stages -- have
meandering pulsation periods and light curve asymmetries, the causes of which
are still unclear. We aim to understand better the origin of these phenomena by
investigating a sample of solar-neighbourhood Miras. We characterised this
group of stars and related their variability characteristics to other stellar
parameters. We analysed observations from several databases to obtain light
curves with maximum time span and temporal coverage for a sample of 548 Miras.
We determined their pulsation period evolution over a time span of many
decades, searched for changes in the periods, and determined the amplitude of
the period change. We also analysed the Fourier spectra with respect to
possible secondary frequency maxima. The sample was divided into two groups
with respect to the presence of light curve bumps. IR colours and indicators of
the third dredge-up were collected to study the sample stars' mass-loss and
deep mixing properties. Our analysis revealed one new star, T~Lyn, with a
continuously changing period. The group of Miras with meandering period changes
is exclusively made up of M-type stars. The Fourier spectra of the meandering
period Miras have no prominent additional peaks, suggesting that additional
pulsation modes are not the cause of the meandering periods. We confirm that
bumps are more common among S and C Miras and show, for the first time, that
Miras with bumps have lower mass-loss rates than those with regular, symmetric
light curves. Also Miras with meandering period changes have relatively little
mass loss. We conclude that Miras with strongly changing periods or asymmetries
in their light curves have relatively low dust mass-loss rates. Meandering
period changes and light curve asymmetries could be connected to He-shell
flashes and third dredge-up episodes.Comment: 13 pages (plus 13 pages Appendix), 14 Figures, accepted for
publication in A&
Weak Lensing Analysis of the z~0.8 cluster CL 0152-1357 with the Advanced Camera for Surveys
We present a weak lensing analysis of the X-ray luminous cluster CL 0152-1357
at z~0.84 using HST/ACS observations. The unparalleled resolution and
sensitivity of ACS enable us to measure weakly distorted, faint background
galaxies to the extent that the number density reaches ~175 arcmin^-2. The PSF
of ACS has a complicated shape that also varies across the field. We construct
a PSF model for ACS from an extensive investigation of 47 Tuc stars in a
modestly crowded region. We show that this model PSF excellently describes the
PSF variation pattern in the cluster observation when a slight adjustment of
ellipticity is applied. The high number density of source galaxies and the
accurate removal of the PSF effect through moment-based deconvolution allow us
to restore the dark matter distribution of the cluster in great detail. The
direct comparison of the mass map with the X-ray morphology from Chandra
observations shows that the two peaks of intracluster medium traced by X-ray
emission are lagging behind the corresponding dark matter clumps, indicative of
an on-going merger. The overall mass profile of the cluster can be well
described by an NFW profile with a scale radius of r_s =309+-45 kpc and a
concentration parameter of c=3.7+-0.5. The mass estimates from the lensing
analysis are consistent with those from X-ray and Sunyaev-Zeldovich analyses.
The predicted velocity dispersion is also in good agreement with the
spectroscopic measurement from VLT observations. In the adopted WMAP cosmology,
the total projected mass and the mass-to-light ratio within 1 Mpc are estimated
to be 4.92+-0.44 10^14 solar mass and 95+-8 solar mass/solar luminosity,
respectively.Comment: Accepted for publication in Astrophysical Journal. 58 pages, 26
figures. Figures have been degraded to meet size limit; a higher resolution
version available at http://acs.pha.jhu.edu/~mkjee/ms_cl0152.pd
A Gamified Approach Towards Identifying Key Opportunities and Potential Sponsors for the Future of F1 Racing in a Declining Car Ownership Environment
This research work aims to propose new approaches towards identifying key opportunities and potential sponsors for the future of F1 racing in an environment with declining car ownership, without resorting to endless licensing agreements. The paper presents a gamification approach on which an innovative and disruptive operations framework can be developed to help, without operational complexity and commitment, F1 teams gain new customers (fans) and recapture essential markets and targets groups. The paper also contributes on establishing a base for effective strategy development based on the userâs/playerâs engagement and behavior. Furthermore, this work extends towards the analysis of the gameâs operations and the marketing initiatives needed to succeed. The proposed approach varies from OHH (out of home advertising), interactive marketing, celebrities, F1 driversâ endorsements, and other related supportive initiatives such as search engine optimization on online research platforms and other promotion and marketing dissemination initiatives
NICMOS Snapshot Survey of Damped Lyman Alpha Quasars
We image 19 quasars with 22 damped Lyman alpha (DLA) systems using the F160W
filter and the Near-Infrared Camera and Multiobject Spectrograph aboard the
Hubble Space Telescope, in both direct and coronagraphic modes. We reach 5
sigma detection limits of ~H=22 in the majority of our images. We compare our
observations to the observed Lyman-break population of high-redshift galaxies,
as well as Bruzual & Charlot evolutionary models of present-day galaxies
redshifted to the distances of the absorption systems. We predict H magnitudes
for our DLAs, assuming they are producing stars like an L* Lyman-break galaxy
(LBG) at their redshift. Comparing these predictions to our sensitivity, we
find that we should be able to detect a galaxy around 0.5-1.0 L* (LBG) for most
of our observations. We find only one new possible candidate, that near
LBQS0010-0012. This scarcity of candidates leads us to the conclusion that most
DLA systems are not drawn from a normal LBG luminosity function nor a local
galaxy luminosity function placed at these high redshifts.Comment: 31 pages, 8 figures, Accepted for Feb. 10 issue of Ap
Wearable Internet of Things - from Human Activity Tracking to Clinical Integration
Wearable devices for human activity tracking have been rapidly emerging. Most of them are capable of sending health statistics to smartphones, smartwatches or smart bands. However, they only provide the data for individual analysis and their data is not integrated into clinical practice. Leveraging on the Internet of Things (IoT), edge and cloud computing technologies, we propose an architecture which is capable of providing cloud based clinical services using human activity data. Such services could supplement the shortage of staff in primary healthcare centers thereby reducing the burden on healthcare service providers. The enormous amount of data created from such services could also be utilized for planning future therapies by studying recovery cycles of existing patients. We provide a prototype based on our architecture and discuss its salient features. We also provide use cases of our system in personalized and home based healthcare services. We propose an International Telecommunication Union based standardization (ITU-T) for our design and discuss future directions in wearable IoT
HST/ACS weak lensing analysis of the galaxy cluster RDCS 1252.9-2927 at z=1.24
We present a weak lensing analysis of one of the most distant massive galaxy
cluster known, RDCS 1252.9-2927 at z=1.24, using deep images from the Advanced
Camera for Survey (ACS) on board the Hubble Space Telescope (HST). By taking
advantage of the depth and of the angular resolution of the ACS images, we
detect for the first time at z>1 a clear weak lensing signal in both the i
(F775W) and z (F850LP) filters. We measure a 5-\sigma signal in the i band and
a 3-\sigma signal in the shallower z band image. The two radial mass profiles
are found to be in very good agreement with each other, and provide a
measurement of the total mass of the cluster inside a 1Mpc radius of M(<1Mpc) =
(8.0 +/- 1.3) x 10^14 M_\odot in the current cosmological concordance model h
=0.70, \Omega_m=0.3, \Omega_\Lambda=0.7, assuming a redshift distribution of
background galaxies as inferred from the Hubble Deep Fields surveys. A weak
lensing signal is detected out to the boundary of our field (3' radius,
corresponding to 1.5Mpc at the cluster redshift). We detect a small offset
between the centroid of the weak lensing mass map and the brightest cluster
galaxy, and we discuss the possible origin of this discrepancy. The cumulative
weak lensing radial mass profile is found to be in good agreement with the
X-ray mass estimate based on Chandr and XMM-Newton observations, at least out
to R_500=0.5Mpc.Comment: 38 pages, ApJ in press. Full resolution images available at
http://www.eso.org/~prosati/RDCS1252/Lombardi_etal_accepted.pd
ACS Observations of a Strongly Lensed Arc in a Field Elliptical
We report the discovery of a strongly lensed arc system around a field
elliptical galaxy in Hubble Space Telescope (HST) Advanced Camera for Surveys
(ACS) images of a parallel field observed during NICMOS observations of the HST
Ultra-Deep Field. The ACS parallel data comprise deep imaging in the F435W,
F606W, F775W, and F850LP bandpasses. The main arc is at a radius of 1.6 arcsec
from the galaxy center and subtends about 120 deg. Spectroscopic follow-up at
Magellan Observatory yields a redshift z=0.6174 for the lensing galaxy, and we
photometrically estimate z_phot = 2.4\pm0.3 for the arc. We also identify a
likely counter-arc at a radius of 0.6 arcsec, which shows structure similar to
that seen in the main arc. We model this system and find a good fit to an
elliptical isothermal potential of velocity dispersion
\kms, the value expected from the fundamental plane, and some external shear.
Several other galaxies in the field have colors similar to the lensing galaxy
and likely make up a small group.Comment: Accepted for publication in ApJ Letters. 10 pages, 3 figures. Figures
have been degraded to meet size limit; a higher resolution version and
addtional pictures available at http://acs.pha.jhu.edu/~jpb/UDFparc
- âŠ