94 research outputs found
Testing quantised inertia on galactic scales
Galaxies and galaxy clusters have rotational velocities apparently too fast
to allow them to be gravitationally bound by their visible matter. This has
been attributed to the presence of invisible (dark) matter, but so far this has
not been directly detected. Here, it is shown that a new model that modifies
inertial mass by assuming it is caused by Unruh radiation, which is subject to
a Hubble-scale (Theta) Casimir effect predicts the rotational velocity (v) to
be: v^4=2GMc^2/Theta (the Tully-Fisher relation) where G is the gravitational
constant, M is the baryonic mass and c is the speed of light. The model
predicts the outer rotational velocity of dwarf and disk galaxies, and galaxy
clusters, within error bars, without dark matter or adjustable parameters, and
makes a prediction that local accelerations should remain above 2c^2/Theta at a
galaxy's edge.Comment: 7 pages, 1 figure. Accepted for publication in Astrophysics and Space
Science on 27/7/201
Gas Accretion via Lyman Limit Systems
In cosmological simulations, a large fraction of the partial Lyman limit
systems (pLLSs; 16<log N(HI)<17.2) and LLSs (17.2log N(HI)<19) probes
large-scale flows in and out of galaxies through their circumgalactic medium
(CGM). The overall low metallicity of the cold gaseous streams feeding galaxies
seen in these simulations is the key to differentiating them from metal rich
gas that is either outflowing or being recycled. In recent years, several
groups have empirically determined an entirely new wealth of information on the
pLLSs and LLSs over a wide range of redshifts. A major focus of the recent
research has been to empirically determine the metallicity distribution of the
gas probed by pLLSs and LLSs in sizable and representative samples at both low
(z2) redshifts. Here I discuss unambiguous evidence for
metal-poor gas at all z probed by the pLLSs and LLSs. At z<1, all the pLLSs and
LLSs so far studied are located in the CGM of galaxies with projected distances
<100-200 kpc. Regardless of the exact origin of the low-metallicity pLLSs/LLSs,
there is a significant mass of cool, dense, low-metallicity gas in the CGM that
may be available as fuel for continuing star formation in galaxies over cosmic
time. As such, the metal-poor pLLSs and LLSs are currently among the best
observational evidence of cold, metal-poor gas accretion onto galaxies.Comment: Invited review to appear in Gas Accretion onto Galaxies, Astrophysics
and Space Science Library, eds. A. J. Fox & R. Dav\'e, to be published by
Springe
Hydrogen and Metal Line Absorption Around Low-Redshift Galaxies in Cosmological Hydrodynamic Simulations
We study the physical conditions of the circum-galactic medium (CGM) around
z=0.25 galaxies as traced by HI and metal line absorption, using cosmological
hydrodynamic simulations that include galactic outflows. Using lines of sight
targeted at impact parameters from 10 kpc to 1 Mpc around galaxies with halo
masses from 10^11-10^13 M_solar, we study the physical conditions and their
variation with impact parameter b and line-of-sight velocity delta v in the CGM
as traced by HI, MgII, SiIV, CIV, OVI, and NeVIII absorbers. All ions show a
strong excess of absorption near galaxies compared to random lines of sight.
The excess continues beyond 1 Mpc, reflecting the correlation of metal
absorption with large-scale structure. Absorption is particularly enhanced
within about v<300 km/sec and roughly 300 kpc of galaxies (with distances
somewhat larger for the highest ion), approximately delineating the CGM; this
range contains the majority of global metal absorption. Low ions like MgII and
SiIV predominantly arise in denser gas closer to galaxies and drop more rapidly
with b, while high ions OVI and NeVIII trace more diffusely distributed gas
with a comparatively flat radial profile; CIV is intermediate. All ions
predominantly trace T~10^4-4.5 K photo-ionised gas at all b, but when hot CGM
gas is present (mostly in larger halos), we see strong collisionally-ionised
OVI and NeVIII at b <= 100 kpc. Larger halo masses generally produce more
absorption, though overall the trends are not as strong as that with impact
parameter. These findings arise using our favoured outflow scalings as expected
for momentum-driven winds; with no winds, the CGM gas remains mostly
unenriched, while our outflow model with a constant velocity and mass loading
factor produce hotter, more widely dispersed metals.Comment: 26 pages, 15 figures, published in MNRAS. Updates to citations from
previous versio
Spectra and Light Curves of Six Type Ia Supernovae at 0.511 < z < 1.12 and the Union2 Compilation
We report on work to increase the number of well-measured Type Ia supernovae
(SNe Ia) at high redshifts. Light curves, including high signal-to-noise HST
data, and spectra of six SNe Ia that were discovered during 2001 are presented.
Additionally, for the two SNe with z>1, we present ground-based J-band
photometry from Gemini and the VLT. These are among the most distant SNe Ia for
which ground based near-IR observations have been obtained. We add these six
SNe Ia together with other data sets that have recently become available in the
literature to the Union compilation (Kowalski et al. 2008). We have made a
number of refinements to the Union analysis chain, the most important ones
being the refitting of all light curves with the SALT2 fitter and an improved
handling of systematic errors. We call this new compilation, consisting of 557
supernovae, the Union2 compilation. The flat concordance LambdaCDM model
remains an excellent fit to the Union2 data with the best fit constant equation
of state parameter w=-0.997^{+0.050}_{-0.054} (stat) ^{+0.077}_{-0.082}
(stat+sys\ together) for a flat universe, or w=-1.035^{+0.055}_{-0.059}
(stat)^{+0.093}_{-0.097} (stat+sys together) with curvature. We also present
improved constraints on w(z). While no significant change in w with redshift is
detected, there is still considerable room for evolution in w. The strength of
the constraints depend strongly on redshift. In particular, at z > 1, the
existence and nature of dark energy are only weakly constrained by the data.Comment: 33 pages, 18 figures; accepted for publication in Astrophysical
Journal. For data tables, code for cosmological analysis and full-resolution
figures, see http://supernova.lbl.gov/Union
Hereditary cataract in the Bengal cat in Poland
Background: This paper reports the significant prevalence of a presumed hereditary cataract in the Bengal cat breed in Poland. The nuclear part of the lens is affected and previous reports from Sweden and France for this type of feline cataract suggest that a recessive mode of inheritance is probably involved.
Results: Presumed congenital or neonatal cataract involving the posterior nuclear part of each lens was initially diagnosed in a 12 month old male Bengal cat. As both parents and a sibling were also affected with cataract, a group of 18 related and 11 non-related cats was then subsequently examined. Eight related cats and one non- related cat were found to be similarly affected. A breed survey was then completed using an additional five centres across Poland and a further 190 related cats were examined. A total of 223 cats have been involved in this study, with 75 (33%) being affected with several types of cataract and 67 (30%) being specifically affected with the same or similar nuclear lesions. Eight cats (3.6%) presented with other cataract types and a prominence of the posterior lens suture lines was recorded in 65 cats unaffected with cataract (29%). There were no demonstrable vision problems. Neither age nor coat colour was significantly associated with the nuclear cataract, but the nuclear cataract group had a higher proportion of females than the unaffected group. Pedigree analysis has indicated probable inheritance as a recessive trait.
Conclusions: These findings suggest that a presumably inherited nuclear cataract is present in the Bengal cat breed in Poland. It is considered to be either congenital or of very early onset, probably being inherited as a recessive trait. Although the lesion has no noticeable effect on vision, breeders in Poland and worldwide should be aware of the disease and clinical examination of young breeding stock prior to reproduction is advisable
A spatially resolved study of photoelectric heating and [CII] cooling in the LMC
(abridged) We study photoelectric heating throughout the Large Magellanic
Cloud. We quantify the importance of the [CII] cooling line and the
photoelectric heating process of various environments in the LMC and
investigate which parameters control the extent of photoelectric heating. We
use the BICE [CII] map and the Spitzer/SAGE infrared maps. We examine the
spatial variations in the efficiency of photoelectric heating: photoelectric
heating rate over power absorbed by grains. We correlate the photoelectric
heating efficiency and the emission from various dust constituents and study
the variations as a function of H\alpha emission, dust temperatures, and the
total infrared luminosity. From this we estimate radiation field, gas
temperature, and electron density. We find systematic variations in
photoelectric efficiency. The highest efficiencies are found in the diffuse
medium, while the lowest coincide with bright star-forming regions (~1.4 times
lower). The [CII] line emission constitutes 1.32% of the far infrared
luminosity across the whole of the LMC. We find correlations between the [CII]
emission and ratios of the mid infrared and far infrared bands, which comprise
various dust constituents. The correlations are interpreted in light of the
spatial variations of the dust abundance and by the local environmental
conditions that affect the dust emission properties. As a function of the total
infrared surface brightness, S_{TIR}, the [CII] surface brightness can be
described as: S_{[CII]}=1.25 S_{TIR}^{0.69} [10^{-3} erg s^{-1} cm^{-2}
sr^{-1}]. The [CII] emission is well-correlation with the 8 micrometer
emission, suggesting that the polycyclic aromatic hydrocarbons play a dominant
role in the photoelectric heating process.Comment: Accepted for publication in A&A, 16 pages, 17 figure
Functional Copy-Number Alterations in Cancer
Understanding the molecular basis of cancer requires characterization of its genetic defects. DNA microarray technologies can provide detailed raw data about chromosomal aberrations in tumor samples. Computational analysis is needed (1) to deduce from raw array data actual amplification or deletion events for chromosomal fragments and (2) to distinguish causal chromosomal alterations from functionally neutral ones. We present a comprehensive computational approach, RAE, designed to robustly map chromosomal alterations in tumor samples and assess their functional importance in cancer. To demonstrate the methodology, we experimentally profile copy number changes in a clinically aggressive subtype of soft-tissue sarcoma, pleomorphic liposarcoma, and computationally derive a portrait of candidate oncogenic alterations and their target genes. Many affected genes are known to be involved in sarcomagenesis; others are novel, including mediators of adipocyte differentiation, and may include valuable therapeutic targets. Taken together, we present a statistically robust methodology applicable to high-resolution genomic data to assess the extent and function of copy-number alterations in cancer
The 16th Data Release of the Sloan Digital Sky Surveys: First Release from the APOGEE-2 Southern Survey and Full Release of eBOSS Spectra
This paper documents the 16th data release (DR16) from the Sloan Digital Sky Surveys (SDSS), the fourth and penultimate from the fourth phase (SDSS-IV). This is the first release of data from the Southern Hemisphere survey of the Apache Point Observatory Galactic Evolution Experiment 2 (APOGEE-2); new data from APOGEE-2 North are also included. DR16 is also notable as the final data release for the main cosmological program of the Extended Baryon Oscillation Spectroscopic Survey (eBOSS), and all raw and reduced spectra from that project are released here. DR16 also includes all the data from the Time Domain Spectroscopic Survey and new data from the SPectroscopic IDentification of ERosita Survey programs, both of which were co-observed on eBOSS plates. DR16 has no new data from the Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) survey (or the MaNGA Stellar Library "MaStar"). We also preview future SDSS-V operations (due to start in 2020), and summarize plans for the final SDSS-IV data release (DR17)
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Cause of Death and Predictors of All-Cause Mortality in Anticoagulated Patients With Nonvalvular Atrial Fibrillation : Data From ROCKET AF
M. Kaste on työryhmän ROCKET AF Steering Comm jäsen.Background-Atrial fibrillation is associated with higher mortality. Identification of causes of death and contemporary risk factors for all-cause mortality may guide interventions. Methods and Results-In the Rivaroxaban Once Daily Oral Direct Factor Xa Inhibition Compared with Vitamin K Antagonism for Prevention of Stroke and Embolism Trial in Atrial Fibrillation (ROCKET AF) study, patients with nonvalvular atrial fibrillation were randomized to rivaroxaban or dose-adjusted warfarin. Cox proportional hazards regression with backward elimination identified factors at randomization that were independently associated with all-cause mortality in the 14 171 participants in the intention-to-treat population. The median age was 73 years, and the mean CHADS(2) score was 3.5. Over 1.9 years of median follow-up, 1214 (8.6%) patients died. Kaplan-Meier mortality rates were 4.2% at 1 year and 8.9% at 2 years. The majority of classified deaths (1081) were cardiovascular (72%), whereas only 6% were nonhemorrhagic stroke or systemic embolism. No significant difference in all-cause mortality was observed between the rivaroxaban and warfarin arms (P=0.15). Heart failure (hazard ratio 1.51, 95% CI 1.33-1.70, P= 75 years (hazard ratio 1.69, 95% CI 1.51-1.90, P Conclusions-In a large population of patients anticoagulated for nonvalvular atrial fibrillation, approximate to 7 in 10 deaths were cardiovascular, whereasPeer reviewe
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