4,288 research outputs found
The Implications of Galaxy Formation Models for the TeV Observations of Current Detectors
This paper represents a step toward constraining galaxy formation models via
TeV gamm a ray observations. We use semi-analytic models of galaxy formation to
predict a spectral distribution for the intergalactic infrared photon field,
which in turn yields information about the absorption of TeV gamma rays from
extra-galactic sources. By making predictions for integral flux observations at
>200 GeV for several known EGRE T sources, we directly compare our models with
current observational upper limits obtained by Whipple. In addition, our
predictions may offer a guide to the observing programs for the current
population of TeV gamma ray observatories.Comment: 6 pages, 11 figures, to appear in the proceedings of the 6th TeV
Workshop at Snowbird, U
Reciprocal and non-reciprocal recombination between closely linked markers
Reciprocal and non-reciprocal recombination between closely linked marker
New constraints on dust emission and UV attenuation of z=6.5-7.5 galaxies from millimeter observations
We have targeted two recently discovered Lyman break galaxies (LBGs) to
search for dust continuum and [CII] 158 micron line emission. The strongly
lensed z~6.8 LBG A1703-zD1 behind the galaxy cluster Abell 1703, and the
spectroscopically confirmed z=7.508 LBG z8-GND-5296 in the GOODS-N field have
been observed with the Plateau de Bure interferometer (PdBI) at 1.2mm. These
observations have been combined with those of three z>6.5 Lya emitters (named
HCM6A, Himiko, and IOK-1), for which deep measurements were recently obtained
with the PdBI and ALMA. [CII] is undetected in both galaxies, providing a deep
upper limit for Abell1703-zD1, comparable to recent ALMA non-detections. Dust
continuum emission from Abell1703-zD1 and z8-GND-5296 is not detected with an
rms of 0.12 and 0.16 mJy/beam. From these non-detections we derive upper limits
on their IR luminosity and star formation rate, dust mass, and UV attenuation.
Thanks to strong gravitational lensing the limit for Abell1703-zD1 is probing
the sub-LIRG regime ( Lsun) and very low dust
masses ( Msun). We find that all five galaxies are
compatible with the Calzetti IRX- relation, their UV attenuation is
compatible with several indirect estimates from other methods (the UV slope,
extrapolation of the attenuation measured from the IR/UV ratio at lower
redshift, and SED fits), and the dust-to-stellar mass ratio is not incompatible
with that of galaxies from z=0 to 3. For their stellar mass the high-z galaxies
studied here have an attenuation below the one expected from the mean relation
of low redshift (z<1.5) galaxies. More and deeper (sub)-mm data are clearly
needed to directly determine the UV attenuation and dust content of the
dominant population of high-z star-forming galaxies and to establish more
firmly their dependence on stellar mass, redshift, and other properties.Comment: 10 pages, 7 figures. Minor revisions. Accepted for publication in A&
An open environment CT-US fusion for tissue segmentation during interventional guidance.
Therapeutic ultrasound (US) can be noninvasively focused to activate drugs, ablate tumors and deliver drugs beyond the blood brain barrier. However, well-controlled guidance of US therapy requires fusion with a navigational modality, such as magnetic resonance imaging (MRI) or X-ray computed tomography (CT). Here, we developed and validated tissue characterization using a fusion between US and CT. The performance of the CT/US fusion was quantified by the calibration error, target registration error and fiducial registration error. Met-1 tumors in the fat pads of 12 female FVB mice provided a model of developing breast cancer with which to evaluate CT-based tissue segmentation. Hounsfield units (HU) within the tumor and surrounding fat pad were quantified, validated with histology and segmented for parametric analysis (fat: -300 to 0 HU, protein-rich: 1 to 300 HU, and bone: HU>300). Our open source CT/US fusion system differentiated soft tissue, bone and fat with a spatial accuracy of âŒ1 mm. Region of interest (ROI) analysis of the tumor and surrounding fat pad using a 1 mm(2) ROI resulted in mean HU of 68±44 within the tumor and -97±52 within the fat pad adjacent to the tumor (p<0.005). The tumor area measured by CT and histology was correlated (r(2)â=â0.92), while the area designated as fat decreased with increasing tumor size (r(2)â=â0.51). Analysis of CT and histology images of the tumor and surrounding fat pad revealed an average percentage of fat of 65.3% vs. 75.2%, 36.5% vs. 48.4%, and 31.6% vs. 38.5% for tumors <75 mm(3), 75-150 mm(3) and >150 mm(3), respectively. Further, CT mapped bone-soft tissue interfaces near the acoustic beam during real-time imaging. Combined CT/US is a feasible method for guiding interventions by tracking the acoustic focus within a pre-acquired CT image volume and characterizing tissues proximal to and surrounding the acoustic focus
Balloon-borne radiometer measurement of Northern Hemisphere mid-latitude stratospheric HNO3 profiles spanning 12 years
Low-resolution atmospheric thermal emission spectra collected by balloon-borne radiometers over the time span of 1990â2002 are used to retrieve vertical profiles of HNO3, CFC-11 and CFC-12 volume mixing ratios between approximately 10 and 35 km altitude. All of the data analyzed have been collected from launches from a Northern Hemisphere mid-latitude site, during late summer, when stratospheric dynamic variability is at a minimum. The retrieval technique incorporates detailed forward modeling of the instrument and the radiative properties of the atmosphere, and obtains a best fit between modeled and measured spectra through a combination of onion-peeling and global optimization steps. The retrieved HNO3 profiles are consistent over the 12-year period, and are consistent with recent measurements by the Atmospheric Chemistry Experiment-Fourier transform spectrometer satellite instrument. This suggests that, to within the errors of the 1990 measurements, there has been no significant change in the HNO3 summer mid-latitude profile
Clovers Around the World: A Symposium in Memory and Honor of Dr. Norman L. Taylor
Trifolium is arguably the largest and most diverse genera of herbaceous forage legumes (Zohary and Heller, 1984). Dr. Norman L. Taylor, Professor Emeritus, Department of Plant and Soil Science, University of Kentucky, deceased, was a pioneer and champion of collection and preservation of Trifolium species throughout his 57-year career. Dr. Taylor was a native of northern Kentucky, born near where this Conference is being held
Pyrocumulonimbus Stratospheric Plume Injections Measured by the ACEâFTS
The Atmospheric Chemistry Experiment (ACE) is a satelliteâbased mission that probes Earth\u27s atmosphere via solar occultation. The primary instrument on board is a highâresolution infrared Fourier transform spectrometer (Atmospheric Chemistry Experiment Fourier Transform Spectrometer, ACEâFTS), providing altitudeâresolved volume mixing ratio measurements for numerous atmospheric constituents, including many biomass burning products. The ACE mission has observed the aftermath of three major pyrocumulonimbus events, in which extreme heat from intense fires created a pathway for directly injecting into the stratosphere plumes of gaseous and aerosol pollutants. These three events were associated with severe Australian bushfires from 2009 and 2019/2020, along with intense North American wildfires from summer 2017. The ACEâFTS measured stratospheric plumes containing aerosols, enhanced levels of gaseous fire products, and tropospheric air transported into the stratosphere. Infrared spectral features indicate strikingly similar aerosol composition for all three events, characteristic of oxygenated organic matter
ALMA detection of [CII] 158 micron emission from a strongly lensed z=2 star-forming galaxy
Our objectives are to determine the properties of the interstellar medium
(ISM) and of star-formation in typical star-forming galaxies at high redshift.
Following up on our previous multi-wavelength observations with HST, Spitzer,
Herschel, and the Plateau de Bure Interferometer (PdBI), we have studied a
strongly lensed z=2.013 galaxy, the arc behind the galaxy cluster MACS
J0451+0006, with ALMA to measure the [CII] 158 micron emission line, one of the
main coolants of the ISM. [CII] emission from the southern part of this galaxy
is detected at 10 . Taking into account strong gravitational lensing,
which provides a magnification of , the intrinsic lensing-corrected
[CII]158 micron luminosity is . The observed
ratio of [CII]-to-IR emission, , is found to be similar to that in nearby galaxies. The same also
holds for the observed ratio , which is
comparable to that of star-forming galaxies and active galaxy nuclei (AGN) at
low redshift. We utilize strong gravitational lensing to extend diagnostic
studies of the cold ISM to an order of magnitude lower luminosity () and SFR than previous work at high redshift.
While larger samples are needed, our results provide evidence that the cold ISM
of typical high redshift galaxies has physical characteristics similar to
normal star forming galaxies in the local Universe.Comment: 5 pages, 4 figures. Accepted for publication in Astronomy &
Astrophysics, Letter
EROs found behind lensing clusters: II.Empirical properties, classification, and SED modelling based on multi-wavelength observations
We study the properties and nature of extremely red galaxies (ERO, R-K>5.6)
found behind two lensing clusters and compare them with other known galaxy
populations. New HST/ACS observations, Spitzer IRAC and MIPS, and Chandra/ACIS
observations of the two lensing clusters Abell 1835 and AC114 contemplate our
earlier optical and near-IR observations and have been used to study extremely
red objects (EROs) in these deep fields. We have found 6 and 9 EROs in Abell
1835 and AC114. Several (7) of these objects are undetected up to the I and/or
z band, and are hence ``optical'' drop-out sources. The photometric redshifts
of most of our sources (80%) are z~0.7-1.5. According to simple colour-colour
diagrams the majority of our objects would be classified as hosting old stellar
populations. However, there are clear signs of dusty starbursts for several
among them. These objects correspond to the most extreme ones in R-K colour. We
estimate a surface density of (0.97+-0.31) arcmin-2 for EROs with (R-K>5.6) at
K<20.5. Among our 15 EROs 6 (40 %) also classify as distant red galaxies
(DRGs). 11 of 13 EROs with available IRAC photometry also fulfil the selection
criteria for IRAC selected EROs (IEROs) of Yan et al. (2004). SED modelling
shows that ~ 36 % of the IEROs in our sample are luminous or ultra-luminous
infrared galaxies ((U)LIRG). Some very red DRGs are found to be very dusty
starbursts, even (U)LIRGs, as also supported by their mid-IR photometry. No
indication for AGNs is found, although faint activity cannot be excluded for
all objects. From mid-IR and X-ray data 5 objects are clearly classified as
starbursts. The derived properties are quite similar to those of DRGs and
IEROs, except for 5 extreme objects in terms of colours, for which a very high
extinction (Av>3) is found.Comment: 20 pages, 10 figures, accepted for publication in A&
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