Emissivity measurements of reflective surfaces at near-millimeter wavelengths

We have developed an instrument for directly measuring the emissivity of reflective surfaces at near-millimeter wavelengths. The thermal emission of a test sample is compared with that of a reference surface, allowing the emissivity of the sample to be determined without heating. The emissivity of the reference surface is determined by one’s heating the reference surface and measuring the increase in emission. The instrument has an absolute accuracy of Δe = 5 x 10^-4 and can reproducibly measure a difference in emissivity as small as Δe = 10^-4 between flat reflective samples. We have used the instrument to measure the emissivity of metal films evaporated on glass and carbon fiber-reinforced plastic composite surfaces. We measure an emissivity of (2.15 ± 0.4) x 10^-3 for gold evaporated on glass and (2.65 ± 0.5) x 10^-3 for aluminum evaporated on carbon fiber-reinforced plastic composite

How light can the Higgs be?

It is widely believed that, for a given Top mass, the Higgs mass has a lower bound: if m_Higgs is too small, the Higgs vacuum is unstable due to Top dynamics. From vacuum instability, the state-of-the-art calculation of the lower bound is close to the current experimental limit. Using non-perturbative simulations and large N calculations, we show that the vacuum is in fact never unstable. Instead, we investigate the existence of a new lower bound, based on the intrinsic cut-off of this trivial theory.Comment: 3 pages, 4 figures, uses espcrc2.sty, Lattice2003(higgs

Is Rhiver Ghaggar, Saraswati? Geochemical constraints

The identity of the river along which the famous Harappan Civilization developed and the causes of the demise of this culture are topics of considerable debate. Many of the Harappan sites are located along the ephemeral Ghaggar river within the Thar Desert in the northwestern India and adjacent Pakistan. The Ghaggar was also thought to be the mythical river Saraswati, which was described as glacial-fed river. Sr and Nd isotopic composition of the Ghaggar alluvium as well as Thar Desert sediments suggests a Sub-Himalayan sediment source, with no contribution from the glaciated regions. The development of extensive Harappan Civilization all along the Ghaggar suggests a catchment with high monsoon rainfall. It is likely that with the changes in the monsoon scenario after 3500 BC could have gradually dried up the Ghaggar river and resulted in the migration and/or extinction of the Harappan Civilization on this rive

Is river Ghaggar, Saraswati? Geochemical constraints

The identity of the river along which the famous Harappan Civilization developed and the causes of the demise of this culture are topics of considerable debate. Many of the Harappan sites are located along the ephemeral Ghaggar river within the Thar Desert in the northwestern India and adjacent Pakistan. The Ghaggar was also thought to be the mythical river Saraswati, which was described as glacial-fed river. Sr and Nd isotopic composition of the Ghaggar alluvium as well as Thar Desert sediments suggests a Sub-Himalayan sediment source, with no contribution from the glaciated regions. The development of extensive Harappan Civilization all along the Ghaggar suggests a catchment with high monsoon rainfall. It is likely that with the changes in the monsoon scenario after 3500 BC could have gradually dried up the Ghaggar river and resulted in the migration and/or extinction of the Harappan Civilization on this river

The Water Vapor Spectrum of APM 08279+5255: X-Ray Heating and Infrared Pumping over Hundreds of Parsecs

We present the rest-frame 200--320 \mm\ spectrum of the z=3.91 quasar \apm, obtained with Z-Spec at the Caltech Submillimeter Observatory. In addition to the \jeight\ to \jthirteen\ CO rotational transitions which dominate the CO cooling, we find six transitions of water originating at energy levels ranging up to 643 K. Most are first detections at high redshift, and we have confirmed one transition with CARMA. The CO cooling is well-described by our XDR model, assuming L$_{\rm 1-100\,keV}\sim1\times10^{46}\rm\,erg\,s^{-1}$, and that the gas is distributed over a 550-pc sizescale, per the now-favored $\mu$=4 lensing model. The total observed cooling in water corresponds to 6.5$\times10^{9}$ \ls, comparable to that of CO. We compare the water spectrum with that of Mrk 231, finding that the intensity ratios among the high-lying lines are similar, but with a total luminosity scaled up by a factor of $\sim$50. Using this scaling, we estimate an average water abundance relative to \hh\ of 1.4$\times10^{-7}$, a good match to the prediction of the chemical network in the XDR model. As with Mrk 231, the high-lying water transitions are excited radiatively via absorption in the rest-frame far-infrared, and we show that the powerful dust continuum in \apm\ is more than sufficient to pump this massive reservoir of warm water vapor.Comment: Astrophysical Journal, Letters, Accepte

Impact of anthropogenic ocean acidification on thermal tolerance of the spider crab <i>Hyas araneus</i>

Future scenarios for the oceans project combined developments of CO₂ accumulation and global warming and their impact on marine ecosystems. The synergistic impact of both factors was addressed by studying the effect of elevated CO₂ concentrations on thermal tolerance of the cold-eurythermal spider crab <i>Hyas araneus</i> from the population around Helgoland. Here ambient temperatures characterize the southernmost distribution limit of this species. Animals were exposed to present day normocapnia (380 ppm CO₂), CO₂ levels expected towards 2100 (710 ppm) and beyond (3000 ppm). Heart rate and haemolymph PO₂ (P_eO₂) were measured during progressive short term cooling from 10 to 0&deg;C and during warming from 10 to 25&deg;C. An increase of P_eO₂ occurred during cooling, the highest values being reached at 0&deg;C under all three CO₂ levels. Heart rate increased during warming until a critical temperature (<i>T_c</i>) was reached. The putative <i>T_c</i> under normocapnia was presumably &gt;25&deg;C, from where it fell to 23.5&deg;C under 710 ppm and then 21.1&deg;C under 3000 ppm. At the same time, thermal sensitivity, as seen in the <i>Q₁₀</i> values of heart rate, rose with increasing CO₂ concentration in the warmth. Our results suggest a narrowing of the thermal window of <i>Hyas araneus</i> under moderate increases in CO₂ levels by exacerbation of the heat or cold induced oxygen and capacity limitation of thermal tolerance

Non-detection of a pulsar-powered nebula in Puppis A, and implications for the nature of the radio-quiet neutron star RX J0822-4300

We report on a deep radio search for a pulsar wind nebula associated with the radio-quiet neutron star RX J0822-4300 in the supernova remnant Puppis A. The well-determined properties of Puppis A allow us to constrain the size of any nebula to less than 30 arcsec; however we find no evidence for such a source on any spatial scale up to 30 arcmin. These non-detections result in an upper limit on the radio luminosity of any pulsar-powered nebula which is three orders of magnitude below what would be expected if RX J0822-4300 was an energetic young radio pulsar beaming away from us, and cast doubt on a recent claim of X-ray pulsations from this source. The lack of a radio nebula leads us to conclude that RX J0822-4300 has properties very different from most young radio pulsars, and that it represents a distinct population which may be as numerous, or even more so, than radio pulsars.Comment: 5 pages, including 2 embedded EPS figures, uses emulateapj.sty. Accepted to ApJ Letters (minor changes made following referee's report

HerMES: deep number counts at 250 μm, 350 μm and 500 μm in the COSMOS and GOODS-N fields and the build-up of the cosmic infrared background

Aims. The Spectral and Photometric Imaging REceiver (SPIRE) onboard the Herschel space telescope has provided confusion limited maps of deep fields at 250 μm, 350 μm, and 500 μm, as part of the Herschel Multi-tiered Extragalactic Survey (HerMES). Unfortunately, due to confusion, only a small fraction of the cosmic infrared background (CIB) can be resolved into individually-detected sources. Our goal is to produce deep galaxy number counts and redshift distributions below the confusion limit at SPIRE wavelengths (~20 mJy), which we then use to place strong constraints on the origins of the cosmic infrared background and on models of galaxy evolution. Methods. We individually extracted the bright SPIRE sources (>20 mJy) in the COSMOS field with a method using the positions, the flux densities, and the redshifts of the 24 μm sources as a prior, and derived the number counts and redshift distributions of the bright SPIRE sources. For fainter SPIRE sources (<20 mJy), we reconstructed the number counts and the redshift distribution below the confusion limit using the deep 24 μm catalogs associated with photometric redshift and information provided by the stacking of these sources into the deep SPIRE maps of the GOODS-N and COSMOS fields. Finally, by integrating all these counts, we studied the contribution of the galaxies to the CIB as a function of their flux density and redshift. Results. Through stacking, we managed to reconstruct the source counts per redshift slice down to ~2 mJy in the three SPIRE bands, which lies about a factor 10 below the 5σ confusion limit. Our measurements place tight constraints on source population models. None of the pre-existing models are able to reproduce our results at better than 3-σ. Finally, we extrapolate our counts to zero flux density in order to derive an estimate of the total contribution of galaxies to the CIB, finding 10.1_(-2.3)^(+2.6) nW m^(-2) sr^(-1), 6.5_(-1.6)^(+1.7) nW m^(-2) sr^(-1), and 2.8_(-0.8)^(+0.9) nW m^(-2) sr^(-1) at 250 μm, 350 μm, and 500 μm, respectively. These values agree well with FIRAS absolute measurements, suggesting our number counts and their extrapolation are sufficient to explain the CIB. We find that half of the CIB is emitted at z = 1.04, 1.20, and 1.25, respectively. Finally, combining our results with other works, we estimate the energy budget contained in the CIB between 8 μm and 1000 μm: 26_(-3)^(+7) nW m^(-2) sr^(-1)