211 research outputs found
Ly alpha emitting galaxies as early stages in galaxy formation
We present optical spectroscopy of two samples of GALEX grism selected Ly
alpha emitters (LAEs): one at z=0.195-0.44 and the other at z=0.65-1.25. We
have also observed a comparison sample of galaxies in the same redshift
intervals with the same UV magnitude distributions but with no detected Ly
alpha. We use the optical spectroscopy to eliminate active galactic nuclei
(AGNs) and to obtain the optical emission-line properties of the samples. We
compare the luminosities of the LAEs in the two redshift intervals and show
that there is dramatic evolution in the maximum Ly alpha luminosity over z=0-1.
Focusing on the z=0.195-0.44 samples alone, we show that there are tightly
defined relations between all of the galaxy parameters and the rest-frame
equivalent width (EW) of H alpha. The higher EW(H alpha) sources all have lower
metallicities, bluer colors, smaller sizes, and less extinction, consistent
with their being in the early stages of the galaxy formation process. We find
that 75 +- 12% of the LAEs have EW(H alpha)>100 Angstrom, and, conversely, that
31 +/- 3% of galaxies with EW(H alpha)>100 Angstrom are LAEs. We correct the
broadband magnitudes for the emission-line contributions and use spectral
synthesis fits to estimate the ages of the galaxies. We find a median age of
1.1x10^{8} yr for the LAE sample and 1.4x10^{9} yr for the UV-continuum sample
without detected Ly alpha. The median metallicity of the LAE sample is
12+log(O/H)=8.24, or about 0.4 dex lower than the UV-continuum sample.Comment: to be published in the Astrophysical Journa
CRP 463: Active Transportation Plan for the City of Paso Robles
As a part of CRP 463 led by Dr. William Riggs, this report provided an analysis of the bicycle, pedestrian and transit travel in the City of Paso Robles and produced a draft Active Transportation Plan for the City
The ACUTE (Ambulance CPAP: Use, Treatment effect and economics) feasibility study: a pilot randomised controlled trial of prehospital CPAP for acute respiratory failure
Background: Acute respiratory failure (ARF) is a common and life-threatening medical emergency. Standard prehospital
management involves controlled oxygen therapy and disease-specific ancillary treatments. Continuous positive airway
pressure (CPAP) is a potentially beneficial alternative treatment that could be delivered by emergency medical services.
However, it is uncertain whether this treatment could work effectively in United Kingdom National Health Service (NHS)
ambulance services and if it represents value for money.
Methods: An individual patient randomised controlled external pilot trial will be conducted comparing prehospital CPAP
to standard oxygen therapy for ARF. Adults presenting to ambulance service clinicians will be eligible if they have
respiratory distress with peripheral oxygen saturation below British Thoracic Society (BTS) target levels, despite titrated
supplemental oxygen. Enrolled patients will be allocated (1:1 simple randomisation) to prehospital CPAP (O_two system)
or standard oxygen therapy using identical sealed boxes. Feasibility outcomes will include incidence of recruited eligible
patients, number of erroneously recruited patients and proportion of cases adhering to allocation schedule and
treatment, followed up at 30 days and with complete data collection. Effectiveness outcomes will comprise survival at
30 days (definitive trial primary end point), endotracheal intubation, admission to critical care, length of hospital stay,
visual analogue scale (VAS) dyspnoea score, EQ-5D-5L and health care resource use at 30 days. The cost-effectiveness
of CPAP, and of conducting a definitive trial, will be evaluated by updating an existing economic model. The trial aims
to recruit 120 patients over 12 months from four regional ambulance hubs within the West Midlands Ambulance
Service (WMAS). This sample size will allow estimation of feasibility outcomes with a precision of < 5%. Feasibility and
effectiveness outcomes will be reported descriptively for the whole trial population, and each trial arm, together with
their 95% confidence intervals.
Discussion: This study will determine if it is feasible, acceptable and cost-effective to undertake a full-scale trial
comparing CPAP and standard oxygen treatment, delivered by ambulance service clinicians for ARF. This will inform
NHS practice and prevent inappropriate prehospital CPAP adoption on the basis of limited evidence and at a
potentially substantial cost.
Trial registration: ISRCTN12048261. Registered on 30 August 2017. http://www.isrctn.com/ISRCTN1204826
The antiangiogenic activity of naturally occurring and synthetic homoisoflavonoids from the Hyacinthaceae (sensu APGII)
Excessive blood vessel formation in the eye is implicated in wet age-related macular degeneration, proliferative diabetic retinopathy, neovascular glaucoma, and retinopathy of prematurity, which are major causes of blindness. Small molecule antiangiogenic drugs are strongly needed to supplement existing biologics. Homoisoflavonoids have been previously shown to have potent antiproliferative activities in endothelial cells over other cell types. Moreover, they demonstrated a strong antiangiogenic potential in vitro and in vivo in animal models of ocular neovascularization. Here, we tested the antiangiogenic activity of a group of naturally occurring homoisoflavonoids isolated from the family Hyacinthaceae and related synthetic compounds, chosen for synthesis based on structureâactivity relationship observations. Several compounds showed interesting antiproliferative and antiangiogenic activities in vitro on retinal microvascular endothelial cells, a disease-relevant cell type, with the synthetic chromane, 46, showing the best activity (GI50 of 2.3 Ă 10â4 ÎŒM)
An Empirical Calibration of Star Formation Rate Estimators
(Abridged) The observational determination of the behaviour of the star
formation rate (SFR) with look-back time or redshift has two main weaknesses:
1- the large uncertainty of the dust/extinction corrections, and 2- that
systematic errors may be introduced by the fact that the SFR is estimated using
different methods at different redshifts. To assess the possible systematic
differences among the different SFR estimators and the role of dust, we have
compared SFR estimates using H, SFR(H), [OII]3727\AA,
SFR(OII), UV, SFR(UV) and FIR, SFR(FIR) luminosities of a sample comprising the
31 nearby star forming galaxies having high quality photometric data in the UV,
optical and FIR.
We review the different "standard" methods for the estimation of the SFR and
find that while the standard method provides good agreement between
SFR(H) and SFR(FIR), both SFR(OII) and SFR(UV) are systematically
higher than SFR(FIR), irrespective of the extinction law.
We show that the excess in the SFR(OII) and SFR(UV) is mainly due to an
overestimate of the extinction resulting from the effect of underlying stellar
Balmer absorptions in the measured emission line fluxes. Taking this effect
into consideration in the determination of the extinction brings the SFR(OII)
and SFR(UV) in line with the SFR(FIR) and simultaneously reduces the internal
scatter of the SFR estimations. Based on these results we have derived
"unbiased" SFR expressions for the SFR(UV), SFR(OII) and SFR(H). We
have used these estimators to recompute the SFR history of the Universe using
the results of published surveys.Comment: Accepted for publication in MNRA
Evolutive Unification in Composite Active Galactic Nuclei
In this paper we explore an evolutionary Unified scenario involving super
massive black hole and starburst with outflow, that seems capable of explaining
most of the observational properties of at least part of AGNs. Our suggestion
is explored inside the expectations of the Starburst model close associated
with the AGN where the NLR, BLR and BAL region are produced in part by the
outflow process with shells and in compact supernova remnants. The outflow
process in BAL QSOs with extreme IR and Fe II emission is studied. In addition,
the Fe II poblem regarding the BLR of AGN is analysed. Neither the correlations
between the BAL, IR emission, FeII intensity and the intrinsic properties of
the AGN are clearly understood. We suggest here that the behaviour of the BAL,
IR and FeII emission in AGNs can be understood inside an evolutionary and
composite model for AGNs. In our model, strong BAL systems and Fe II emission
are present (and intense) in young IR objects. Orientation/ obscuration effects
take the role of a second parameter providing the segregation between Sy1/Sy2
and BLRG/NLRG.Comment: 14 pages, 6 figures (submitted MNRAS
Worries about being judged versus being harmed: Disentangling the association of social anxiety and paranoia with schizotypy
Paranoia is a dimension of clinical and subclinical experiences in which others are believed to have harmful intentions. Mild paranoid concerns are relatively common in the general population, and more clinically severe paranoia shares features with social anxiety and is a key characteristic of schizotypy. Given that subclinical manifestations of schizotypy and paranoia may predict the occurrence of more severe symptoms, disentangling the associations of these related constructs may advance our understanding of their etiology; however no known studies to date have comprehensively evaluated how paranoia relates to social anxiety and schizotypy. The current research sought to examine the association of paranoia, assessed across a broad continuum of severity, with 1) the positive and negative schizotypy dimensions and 2) social anxiety. Specifically, the study tested a series of six competing, a priori models using confirmatory factor analysis in a sample of 862 young adults. As hypothesized, the data supported a four-factor model including positive schizotypy, negative schizotypy, social anxiety, and paranoia factors, suggesting that these are distinct constructs with differing patterns of interrelationships. Paranoia had a strong association with positive schizotypy, a moderate association with social anxiety, and a minimal association with negative schizotypy. The results are consistent with paranoia being part of a multidimensional model of schizotypy and schizophrenia. Prior studies treating schizotypy and schizophrenia as homogenous constructs often produce equivocal or non-replicable results because these dimensions are associated with distinct etiologies, presentations, and treatment responses; thus, the present conceptualization of paranoia within a multidimensional schizotypy framework should advance our understanding of these constructs. © 2014 Horton et al
Global characteristics of GRBs observed with INTEGRAL and the inferred large population of low-luminosity GRBs
INTEGRAL has two sensitive gamma-ray instruments that have detected 46
gamma-ray bursts (GRBs) up to July 2007. We present the spectral, spatial, and
temporal properties of the bursts in the INTEGRAL GRB catalogue using data from
the imager, IBIS, and spectrometer, SPI. Spectral properties of the GRBs are
determined using power-law, Band model and quasithermal model fits to the
prompt emission. Spectral lags, i.e. the time delay in the arrival of
low-energy gamma-rays with respect to high-energy gamma-rays, are measured for
31 of the GRBs. The photon index distribution of power-law fits to the prompt
emission spectra is consistent with that obtained by Swift. The peak flux
distribution shows that INTEGRAL detects proportionally more weak GRBs than
Swift because of its higher sensitivity in a smaller field of view. The all-sky
rate of GRBs above ~0.15 ph cm^-2 s^-1 is ~1400 yr^-1 in the fully coded field
of view of IBIS. Two groups are identified in the spectral lag distribution,
one with short lags <0.75 s (between 25-50 keV and 50-300 keV) and one with
long lags >0.75 s. Most of the long-lag GRBs are inferred to have low redshifts
because of their long spectral lags, their tendency to have low peak energies
and their faint optical and X-ray afterglows. They are mainly observed in the
direction of the supergalactic plane with a quadrupole moment of
Q=-0.225+/-0.090 and hence reflect the local large-scale structure of the
Universe. The rate of long-lag GRBs with inferred low luminosity is ~25% of
Type Ib/c supernovae. Some of these bursts could be produced by the collapse of
a massive star without a supernova or by a different progenitor, such as the
merger of two white dwarfs or a white dwarf with a neutron star or black hole,
possibly in the cluster environment without a host galaxy.Comment: 22 pages, 13 figures and appendix, accepted for publication in A&A,
added and updated reference
GRB 090426: The Environment of a Rest-Frame 0.35-second Gamma-Ray Burst at Redshift z=2.609
We present the discovery of an absorption-line redshift of z = 2.609 for GRB
090426, establishing the first firm lower limit to a redshift for a gamma-ray
burst with an observed duration of <2 s. With a rest-frame burst duration of
T_90z = 0.35 s and a detailed examination of the peak energy of the event, we
suggest that this is likely (at >90% confidence) a member of the short/hard
phenomenological class of GRBs. From analysis of the optical-afterglow spectrum
we find that the burst originated along a very low HI column density sightline,
with N_HI < 3.2 x 10^19 cm^-2. Our GRB 090426 afterglow spectrum also appears
to have weaker low-ionisation absorption (Si II, C II) than ~95% of previous
afterglow spectra. Finally, we also report the discovery of a blue, very
luminous, star-forming putative host galaxy (~2 L*) at a small angular offset
from the location of the optical afterglow. We consider the implications of
this unique GRB in the context of burst duration classification and our
understanding of GRB progenitor scenarios.Comment: Submitted to MNRA
Lyman Break Galaxies at z~1.8-2.8: GALEX/NUV Imaging of the Subaru Deep Field
Abridged: A photometric sample of ~7100 V<25.3 Lyman break galaxies (LBGs)
has been selected by combining Subaru/Suprime-Cam BVRci'z' data with deep
GALEX/NUV imaging of the Subaru Deep Field. Follow-up spectroscopy confirmed 24
LBGs at 1.5<z<2.7. Among the optical spectra, 12 have Ly-alpha emission with
rest-frame equivalent widths of ~5-60AA. The success rate for identifying LBGs
as NUV-dropouts at 1.5<z<2.7 is 86%. The rest-frame UV (1700AA) luminosity
function (LF) is constructed from the photometric sample with corrections for
stellar contamination and z<1.5 interlopers. The LF is 1.7+/-0.1 times higher
than those of z~2 BXs and z~3 LBGs. Three explanations were considered, and it
is argued that significantly underestimating low-z contamination or effective
comoving volume is unlikely: the former would be inconsistent with the
spectroscopic sample at 93% confidence, and the second explanation would not
resolve the discrepancy. The third scenario is that different photometric
selection of the samples yields non-identical galaxy populations, such that
some BX galaxies are LBGs and vice versa. This argument is supported by a
higher surface density of LBGs at all magnitudes while the redshift
distribution of the two populations is nearly identical. This study, when
combined with other star-formation rate (SFR) density UV measurements from LBG
surveys, indicates that there is a rise in the SFR density: a factor of 3-6
(3-10) increase from z~5 (z~6) to z~2, followed by a decrease to z~0. This
result, along with past sub-mm studies that find a peak at z~2 in their
redshift distribution, suggest that z~2 is the epoch of peak star-formation.
Additional spectroscopy is required to characterize the complete shape of the
z~2 LBG UV LF via measurements of contamination and accurate distances.Comment: 24 pages, 24 figures (color figures are included), 4 tables. Accepted
for publication in the Astrophysical Journal. Latest version contains minor
changes to Tables 1 and 2, and Figure 4 and 10. Conclusions remain unchange
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