88 research outputs found
Determination of Neutrino Mass Hierarchy and Theta_13 with a Remote Detector of Reactor Antineutrinos
We describe a method for determining the hierarchy of the neutrino mass
spectrum and theta_13 through remote detection of antineutrinos from a nuclear
reactor. This method utilizing a single, 10-kt scintillating liquid detector at
a distance of 50-64 kilometers from the reactor complex measures mass-squared
differences involving nu_3 with a one (ten) year exposure provided
sin2(2theta_13)>0.05 (0.02). Our technique applies the Fourier transform to the
event rate as a function of neutrino flight distance over energy. Sweeping over
a relevant range of delta-m2 resolves separate spectral peaks for delta-m2_31
and delta-m2_32. For normal (inverted) hierarchy the absolute value of
delta-m2_31 is greater (lesser) than the absolute value of delta-m2_32. This
robust method requires a detector energy resolution of 3.5% divided by the
square root of the scintillation energy.Comment: 6 pages, 7 figures, note added to original paper submitted 12
December 200
Evolution of the star formation histories of BLAST galaxies
We have measured star formation histories (SFHs) and stellar masses of
galaxies detected by the Balloon-borne Large Aperture Sub-millimetre Telescope
(BLAST) over approximately 9 square degrees centred on the Chandra Deep Field
South. We have applied the recently developed SFH reconstruction method of Dye
et al. to optical, near-infrared and mid-infrared photometry of 92 BLAST
galaxies. We find significant differences between the SFHs of low mass (<10^11
M_sol) and high mass (>10^11 M_sol) galaxies. On average, low mass galaxies
exhibit a dominant late burst of star formation which creates a large fraction
of their stellar mass. Conversely, high mass systems tend to have a significant
amount of stellar mass that formed much earlier. We also find that the high
mass SFHs evolve more strongly than the low mass SFHs. These findings are
consistent with the phenomenon of downsizing observed in optically selected
samples of galaxies.Comment: Accepted by MNRAS Letters. 5 pages. 4 figure
Constraints on dark and visible mass in galaxies from strong gravitational lensing
We give a non-exhaustive review of the use of strong gravitational lensing in
placing constraints on the quantity of dark and visible mass in galaxies. We
discuss development of the methodology and summarise some recent results.Comment: To appear in proceedings of IAU Symposium 244, 'Dark Galaxies and
Lost Baryons', 25th - 29th June 2007. Nine pages, five figures. Version 2
updates bibliograph
Physics Potential of a Few Kiloton Scale Neutrino Detector at a Deep Underground Lab in Korea
The demand for underground labs for neutrino and rare event search
experiments has been increasing over the last few decades. Yemilab, constructed
in October 2022, is the first deep (1~km) underground lab dedicated to
science in Korea, where a large cylindrical cavern (D: 20~m, H: 20~m) was
excavated in addition to the main caverns and halls. The large cavern could be
utilized for a low background neutrino experiment by a liquid
scintillator-based detector (LSC) where a 2.26 kiloton LS target would be
filled. It's timely to have such a large but ultra-pure LS detector after the
shutdown of the Borexino experiment so that solar neutrinos can be measured
much more precisely. Interesting BSM physics searches can be also pursued with
this detector when it's combined with an electron linac, a proton cyclotron
(IsoDAR source), or a radioactive source. This article discusses the concept of
a candidate detector and the physics potential of a large liquid scintillator
detector.Comment: 63 pages, 36 figures, 8 table
The Infrared Properties of Sources Matched in the WISE All-Sky and Herschel Atlas Surveys
We describe the infrared properties of sources detected over approx. 36 deg2 of sky in the GAMA 15-hr equatorial field, using data from both the Herschel Astrophysical Terahertz Large-Area Survey (H-ATLAS) and Wide-field Infrared Survey (WISE). With 5(sigma) point-source depths of 34 and 0.048 mJy at 250 microns and 3.4 microns, respectively, we are able to identify 50.6% of the H-ATLAS sources in the WISE survey, corresponding to a surface density of approx. 630 deg-2. Approximately two-thirds of these sources have measured spectroscopic or optical/near-IR photometric redshifts of z or approx. 20.5) have 250-350 microns flux density ratios that suggest either high-redshift galaxies (z > or approx. 1.5) or optically faint low-redshift galaxies with unusually low temperatures (T < or approx. 20). Their small 3.4-250 microns flux ratios favor a high-redshift galaxy population, as only the most actively star-forming galaxies at low redshift (e.g., Arp 220) exhibit comparable flux density ratios. Furthermore, we find a relatively large AGN fraction (approx. 30%) in a 12 microns flux-limited subsample of H-ATLAS sources, also consistent with there being a significant population of high-redshift sources in the no-redshift sample
H-ATLAS/GAMA: quantifying the morphological evolution of the galaxy population using cosmic calorimetry
Using results from the Herschel Astrophysical Terrahertz Large-Area Survey (H-ATLAS) and the Galaxy and Mass Assembly (GAMA) project, we show that, for galaxy masses above ≃ 108 M⊙, 51 per cent of the stellar mass-density in the local Universe is in early-type galaxies (ETGs; Sérsic n > 2.5) while 89 per cent of the rate of production of stellar mass-density is occurring in late-type galaxies (LTGs; Sérsic n < 2.5). From this zero-redshift benchmark, we have used a calorimetric technique to quantify the importance of the morphological transformation of galaxies over the history of the Universe. The extragalactic background radiation contains all the energy generated by nuclear fusion in stars since the big bang. By resolving this background radiation into individual galaxies using the deepest far-infrared survey with the Herschel Space Observatory and a deep near-infrared/optical survey with the Hubble Space Telescope (HST), and using measurements of the Sérsic index of these galaxies derived from the HST images, we estimate that ≃83 per cent of the stellar mass-density formed over the history of the Universe occurred in LTGs. The difference between this value and the fraction of the stellar mass-density that is in LTGs today implies there must have been a major transformation of LTGs into ETGs after the formation of most of the stars
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