2,833 research outputs found
Benefits of interprofessional education in health care.
This article examines some of the literature regarding the benefits of interprofessional education (IPE) in the field of health care. These benefits in relation to service users (and carers), higher education institutions, service providers and students are all explored. Barriers to IPE are being broken down by many of the various stakeholders working towards a similar agenda. However, currently there remains some doubt as to whether IPE has a direct positive impact on the health gain of service users and carers. Research is needed to demonstrate if service users and carers benefit directly from IPE and if they do not, the reason for pursuing it needs to be questioned
Spitzer IRAC confirmation of z_850-dropout galaxies in the Hubble Ultra Deep Field: stellar masses and ages at z~7
Using Spitzer IRAC mid-infrared imaging from the Great Observatories Origins
Deep Survey, we study z_850-dropout sources in the Hubble Ultra Deep Field.
After carefully removing contaminating flux from foreground sources, we clearly
detect two z_850-dropouts at 3.6 micron and 4.5 micron, while two others are
marginally detected. The mid-infrared fluxes strongly support their
interpretation as galaxies at z~7, seen when the Universe was only 750 Myr old.
The IRAC observations allow us for the first time to constrain the rest-frame
optical colors, stellar masses, and ages of the highest redshift galaxies.
Fitting stellar population models to the spectral energy distributions, we find
photometric redshifts in the range 6.7-7.4, rest-frame colors U-V=0.2-0.4,
V-band luminosities L_V=0.6-3 x 10^10 L_sun, stellar masses 1-10 x 10^9 M_sun,
stellar ages 50-200 Myr, star formation rates up to ~25 M_sun/yr, and low
reddening A_V<0.4. Overall, the z=7 galaxies appear substantially less massive
and evolved than Lyman break galaxies or Distant Red Galaxies at z=2-3, but
fairly similar to recently identified systems at z=5-6. The stellar mass
density inferred from our z=7 sample is rho* = 1.6^{+1.6}_{-0.8} x 10^6 M_sun
Mpc^-3 (to 0.3 L*(z=3)), in apparent agreement with recent cosmological
hydrodynamic simulations, but we note that incompleteness and sample variance
may introduce larger uncertainties. The ages of the two most massive galaxies
suggest they formed at z>8, during the era of cosmic reionization, but the star
formation rate density derived from their stellar masses and ages is not nearly
sufficient to reionize the universe. The simplest explanation for this
deficiency is that lower-mass galaxies beyond our detection limit reionized the
universe.Comment: 4 pages, 3 figures, emulateapj, Accepted for publication in ApJ
Letter
The Dearth of z~10 Galaxies in all HST Legacy Fields -- The Rapid Evolution of the Galaxy Population in the First 500 Myr
We present an analysis of all prime HST legacy fields spanning >800 arcmin^2
for the search of z~10 galaxy candidates and the study of their UV luminosity
function (LF). In particular, we present new z~10 candidates selected from the
full Hubble Frontier Field (HFF) dataset. Despite the addition of these new
fields, we find a low abundance of z~10 candidates with only 9 reliable sources
identified in all prime HST datasets that include the HUDF09/12, the HUDF/XDF,
all the CANDELS fields, and now the HFF survey. Based on this comprehensive
search, we find that the UV luminosity function decreases by one order of
magnitude from z~8 to z~10 at all luminosities over a four magnitude range.
This also implies a decrease of the cosmic star-formation rate density by an
order of magnitude within 170 Myr from z~8 to z~10. We show that this
accelerated evolution compared to lower redshift can entirely be explained by
the fast build-up of the dark matter halo mass function at z>8. Consequently,
the predicted UV LFs from several models of galaxy formation are in good
agreement with this observed trend, even though the measured UV LF lies at the
low end of model predictions. In particular, the number of only 9 observed
candidate galaxies is lower, by ~50%, than predicted by galaxy evolution
models. The difference is generally still consistent within the Poisson and
cosmic variance uncertainties. However, essentially all models predict larger
numbers than observed. We discuss the implications of these results in light of
the upcoming James Webb Space Telescope mission, which is poised to find much
larger samples of z~10 galaxies as well as their progenitors at less than 400
Myr after the Big Bang.Comment: 13 pages, 6 figures, minor updates to match accepted versio
Low Star Formation Rates for z=1 Early-Type Galaxies in the Very Deep GOODS-MIPS Imaging: Implications for their Optical/Near-Infrared Spectral Energy Distributions
We measure the obscured star formation in z~1 early-type galaxies. This
constrains the influence of star formation on their optical/near-IR colors,
which, we found, are redder than predicted by the model by Bruzual & Charlot
(2003). From deep ACS imaging we construct a sample of 95 morphologically
selected early-type galaxies in the HDF-N and CDF-S with spectroscopic
redshifts in the range 0.85<z<1.15. We measure their 24 micron fluxes from the
deep GOODS-MIPS imaging and derive the IR luminosities and star formation
rates. The fraction of galaxies with >2 sigma detections (~25 muJy} is
17(-4,+9)%. Of the 15 galaxies with significant detections at least six have an
AGN. Stacking the MIPS images of the galaxies without significant detections
and adding the detected galaxies without AGN we find an upper limit on the mean
star formation rate (SFR) of 5.2+/-3.0 Msol yr^-1, and on the mean specific SFR
of 4.6+/-2.2 * 10^-11 yr^-1. Under the assumption that the average SFR will
decline at the same rate as the cosmic average, the in situ growth in stellar
mass of the early-type galaxy population is less than 14+/-7% between z=1 and
the present. We show that the typically low IR luminosity and SFR imply that
the effect of obscured star formation (or AGN) on their rest-frame
optical/near-IR SEDs is negligible for ~90% of the galaxies in our sample.
Hence, their optical/near-IR colors are most likely dominated by evolved
stellar populations. This implies that the colors predicted by the Bruzual &
Charlot (2003) model for stellar populations with ages similar to those of z~1
early-type galaxies (~1-3 Gyr) are most likely too blue, and that stellar
masses of evolved, high-redshift galaxies can be overestimated by up to a
factor of ~2.Comment: Accepted for publication in ApJ, 8 pages, 4 figures, 1 tabl
Extremely Small Sizes for Faint z~2-8 Galaxies in the Hubble Frontier Fields: A Key Input For Establishing their Volume Density and UV Emissivity
We provide the first observational constraints on the sizes of the faintest
galaxies lensed by the Hubble Frontier Fields (HFF) clusters. Ionizing
radiation from faint galaxies likely drives cosmic reionization, and the HFF
initiative provides a key opportunity to find such galaxies. Yet, we cannot
really assess their ionizing emissivity without a robust measurement of their
sizes, since this is key to quantifying both their prevalence and the faint-end
slope to the UV luminosity function. Here we provide the first such size
constraints with 2 new techniques. The first utilizes the fact that the
detectability of highly-magnified galaxies as a function of shear is very
dependent on a galaxy's size. Only the most compact galaxies will remain
detectable in regions of high shear (vs. a larger detectable size range for low
shear), a phenomenon we carefully quantify using simulations. Remarkably,
however, no correlation is found between the surface density of faint galaxies
and the predicted shear, using 87 faint high-magnification mu>10 z~2-8 galaxies
seen behind the first 4 HFF clusters. This can only be the case if such faint
(~-15 mag) galaxies have significantly smaller sizes than luminous galaxies. We
constrain their half-light radii to be <~30 mas (<160-240 pc). As a 2nd size
probe, we rotate and stack 26 faint high-magnification sources along the major
shear axis. Less elongation is found than even for objects with an intrinsic
half-light radius of 10 mas. Together these results indicate that extremely
faint z~2-8 galaxies have near point-source profiles in the HFF dataset
(half-light radii conservatively <30 mas and likely 5-10 mas). These results
suggest smaller completeness corrections and hence much lower volume densities
for faint z~2-8 galaxies and shallower faint-end slopes than have been derived
in many recent studies (by factors of ~2-3 and by dalpha>~0.1-0.3).Comment: 19 pages, 15 figures, 3 tables, accepted for publication in Ap
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