186 research outputs found
Ancient Urban Ecology Reconstructed from Archaeozoological Remains of Small Mammals in the Near East
Acknowledgments We especially thank the many archaeologists who collaborated closely with our project and invested pioneering efforts in intensive fine-scale retrieval of the archaeozoological samples that provided the basis for this study: Shai Bar, Amnon Ben-Tor, Amit Dagan, Yosef Garfinkel, Ayelet Gilboa, Zvi Greenhut, Amihai Mazar, Stefan Munger, Ronny Reich, Itzhaq Shai, Ilan Sharon, Joe Uziel, Sharon Zuckerman, and additional key excavation personnel who were instrumental in collection of the samples or in assisting the work including: Shimrit Bechar, Jacob Dunn, Norma Franklin, Egon Lass and Yiftah Shalev. Funding:The research was funded by a post-doctoral grant awarded to L.W. from the European Research Council under the European Communityâs Seventh Framework Program (FP7/2007e2013)/ERC grant agreement number 229418. The laboratory work was also supported by funding by the Israel Science Foundation (Grant 52/10). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.Peer reviewedPublisher PD
The Rest Frame UV to Optical Colors and SEDs of z~4-7 Galaxies
We use the ultra-deep HUDF09 and the deep ERS data from the HST WFC3/IR
camera, along with the wide area Spitzer/IRAC data from GOODS-S to derive SEDs
of star-forming galaxies from the rest-frame UV to the optical over a wide
luminosity range (M_1500 ~ -21 to M_1500 ~ -18) from z ~ 7 to z ~ 4. The sample
contains ~ 400 z ~ 4, ~ 120 z ~ 5, ~ 60 z ~ 6, and 36 prior z ~ 7 galaxies.
Median stacking enables the first comprehensive study of very faint high-z
galaxies at multiple redshifts (e.g., [3.6] = 27.4 +/- 0.1 AB mag for the
M_1500 ~ -18 sources at z ~ 4). At z ~ 4 our faint median-stacked SEDs reach to
~ 0.06 L*(z=4) and are combined with recently published results at high
luminosity L > L* that extend to M_1500 ~ -23. We use the observed SEDs and
template fits to derive rest frame UV-to-optical colors (U - V) at all
redshifts and luminosities. We find that this color does not vary significantly
with redshift at a fixed luminosity. The UV-to-optical color does show a weak
trend with luminosity, becoming redder at higher luminosities. This is most
likely due to dust. At z >~ 5 we find blue colors [3.6]-[4.5] ~ -0.3 mag that
are most likely due to rest-frame optical emission lines contributing to the
flux in the IRAC filter bandpasses. The scatter across our derived SEDs remains
substantial, but the results are most consistent with a lack of any evolution
in the SEDs with redshift at a given luminosity. The similarity of the SEDs
suggests a self-similar mode of evolution over a timespan from 0.7 Gyr to 1.5
Gyr that encompasses very substantial growth in the stellar mass density in the
universe (from ~ 4x10^6 to ~ 2x10^7 Msun Mpc^-3).Comment: 15 pages, 11 figures, 3 tables, submitted to Ap
Slow Evolution of the Specific Star Formation Rate at z>2: The Impact of Dust, Emission Lines, and A Rising Star Formation History
We measure the evolution of the specific star formation rate (sSFR = SFR /
Mstellar) between redshift 4 and 6 to investigate the previous reports of
"constant" sSFR at z>2. We obtain photometry on a large sample of galaxies at
z~4-6 located in the GOODS-S field that have high quality imaging from HST and
Spitzer. We have derived stellar masses and star formation rates (SFRs) through
stellar population modeling of their spectral energy distributions (SEDs). We
estimate the dust extinction from the observed UV colors. In the SED fitting
process we have studied the effects of assuming a star formation history (SFH)
both with constant SFR and one where the SFR rises exponentially with time. The
latter SFH is chosen to match the observed evolution of the UV luminosity
function. We find that neither the mean SFRs nor the mean stellar masses change
significantly when the rising SFR (RSF) model is assumed instead of the
constant SFR model. When focusing on galaxies with Mstar ~ 5x10^9 Msun, we find
that the sSFR evolves weakly with redshift (sSFR(z) \propto (1+z)^(0.6+/-0.1)
Gyr^-1), consistent with previous results and with recent estimates of the sSFR
at z~2-3 using similar assumptions. We have also investigated the impact of
optical emission lines on our results. We estimate that the contribution of
emission lines to the rest-frame optical fluxes is only modest at z~4 and 5 but
it could reach ~50% at z~6. When emission lines of this strength are taken into
account, the sSFR shows somewhat higher values at high redshifts, according to
the relation sSFR(z) \propto (1+z)^(1.0+/-0.1) Gyr^-1, i.e., ~2.3x higher at
z~6 than at z~2. However, the observed evolution is substantially weaker than
that found at z<2 or that expected from current models (which corresponds to
sSFR(z) \propto (1+z)^(2.5) Gyr^-1). -abridged-Comment: 15 pages, 10 figures, 2 tables. Update from v1: after second referee
report, improved (larger) sample at z~
Light-Induced Pupillary Responses in Alzheimer's Disease
The impact of Alzheimer's disease (AD) on the pupillary light response (PLR) is controversial, being dependent on the stage of the disease and on the experimental pupillometric protocols. The main hypothesis driving pupillometry research in AD is based on the concept that the AD-related neurodegeneration affects both the parasympathetic and the sympathetic arms of the PLR (cholinergic and noradrenergic theory), combined with additional alterations of the afferent limb, involving the melanopsin expressing retinal ganglion cells (mRGCs), subserving the PLR. Only a few studies have evaluated the value of pupillometry as a potential biomarker in AD, providing various results compatible with parasympathetic dysfunction, displaying increased latency of pupillary constriction to light, decreased constriction amplitude, faster redilation after light offset, decreased maximum velocity of constriction (MCV) and maximum constriction acceleration (MCA) compared to controls. Decreased MCV and MCA appeared to be the most accurate of all PLR parameters allowing differentiation between AD and healthy controls while increased post-illumination pupillary response was the most consistent feature, however, these results could not be replicated by more recent studies, focusing on early and pre-clinical stages of the disease. Whether static or dynamic pupillometry yields useful biomarkers for AD screening or diagnosis remains unclear. In this review, we synopsize the current knowledge on pupillometric features in AD and other neurodegenerative diseases, and discuss potential roles of pupillometry in AD detection, diagnosis and monitoring, alone or in combination with additional biomarkers
Understanding Galaxy Formation via Near-Infrared Surveys in the 2020s
A discussion of science cases in extragalactic astrophysics and galaxy formation that wide-area space-based infrared surveys will address in the 2020s. <p/
UVUDF: Ultraviolet Imaging of the Hubble Ultradeep Field with Wide-field Camera 3
We present an overview of a 90-orbit Hubble Space Telescope treasury program
to obtain near ultraviolet imaging of the Hubble Ultra Deep Field using the
Wide Field Camera 3 UVIS detector with the F225W, F275W, and F336W filters.
This survey is designed to: (i) Investigate the episode of peak star formation
activity in galaxies at 1<z<2.5; (ii) Probe the evolution of massive galaxies
by resolving sub-galactic units (clumps); (iii) Examine the escape fraction of
ionizing radiation from galaxies at z~2-3; (iv) Greatly improve the reliability
of photometric redshift estimates; and (v) Measure the star formation rate
efficiency of neutral atomic-dominated hydrogen gas at z~1-3. In this overview
paper, we describe the survey details and data reduction challenges, including
both the necessity of specialized calibrations and the effects of charge
transfer inefficiency. We provide a stark demonstration of the effects of
charge transfer inefficiency on resultant data products, which when
uncorrected, result in uncertain photometry, elongation of morphology in the
readout direction, and loss of faint sources far from the readout. We agree
with the STScI recommendation that future UVIS observations that require very
sensitive measurements use the instrument's capability to add background light
through a "post-flash". Preliminary results on number counts of UV-selected
galaxies and morphology of galaxies at z~1 are presented. We find that the
number density of UV dropouts at redshifts 1.7, 2.1, and 2.7 is largely
consistent with the number predicted by published luminosity functions. We also
confirm that the image mosaics have sufficient sensitivity and resolution to
support the analysis of the evolution of star-forming clumps, reaching 28-29th
magnitude depth at 5 sigma in a 0.2 arcsecond radius aperture depending on
filter and observing epoch.Comment: Accepted A
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