Gravitational Couplings of Higher Spins from String Theory

We calculate the interaction 3-vertex of two massless spin 3 particles with a graviton using vertex operators for spin 3 fields in open string theory, constructed in our previous work. The massless spin 3 fields are shown to interact with the graviton through the linearized Weyl tensor, reproducing the result by Boulanger, Leclercq and Sundell. This is consistent with the general structure of the non-Abelian $2-s-s$ couplings, implying that the minimal number of space-time derivatives in the interaction vertices of two spin s and one spin 2 particle is equal to $2s-2$.Comment: 19 page

Mixed aliphatic and aromatic composition of evaporating very small grains in NGC 7023 revealed by the 3.4/3.3 μ\mum ratio

In photon-dominated regions (PDRs), UV photons from nearby stars lead to the evaporation of very small grains (VSGs) and the production of gas-phase polycyclic aromatic hydrocarbons (PAHs). Our goal is to achieve better insight into the composition and evolution of evaporating very small grains (eVSGs) and PAHs through analyzing the infrared (IR) aliphatic and aromatic emission bands. We combined spectro-imagery in the near- and mid-IR to study the spatial evolution of the emission bands in the prototypical PDR NGC 7023. We used near-IR spectra obtained with AKARI to trace the evolution of the 3.3$\mu$m and 3.4$\mu$m bands, which are associated with aromatic and aliphatic C-H bonds on PAHs. The spectral fitting involves an additional broad feature centred at 3.45$\mu$m. Mid-IR observations obtained with Spitzer are used to discriminate the signatures of eVSGs, neutral and cationic PAHs. We correlated the spatial evolution of all these bands with the intensity of the UV field to explore the processing of their carriers. The intensity of the 3.45$\mu$m plateau shows an excellent correlation with that of the 3.3$\mu$m aromatic band (correlation coefficient R = 0.95), indicating that the plateau is dominated by the emission from aromatic bonds. The ratio of the 3.4$\mu$m and 3.3$\mu$m band intensity ($I_{3.4}/I_{3.3}$) decreases by a factor of 4 at the PDR interface from the more UV-shielded to the more exposed layers. The transition region between the aliphatic and aromatic material is found to correspond spatially with the transition zone between neutral PAHs and eVSGs. We conclude that the photo-processing of eVSGs leads to the production of PAHs with attached aliphatic sidegroups that are revealed by the 3.4$\mu$m emission band. Our analysis provides evidence for the presence of very small grains of mixed aromatic and aliphatic composition in PDRs.Comment: Accepted for publication in A&A. Abstract abridged, language editing applied in v

The Mid-Infrared Spectrum of the Zodiacal and Exozodiacal Light

The zodiacal light is the dominant source of the mid-infrared sky brightness seen from Earth, and exozodiacal light is the dominant emission from planetary and debris systems around other stars. We observed the zodiacal light spectrum with ISOCAM over 5-16 over a wide range of orientations relative to the Sun and the ecliptic. We present theoretical models for a wide range of particle size distributions and compositions. The observed temperature is as expected for large (>10 um radius), low-albedo (< 0.08), rapidly-rotating, grey particles 1 AU from the Sun. In addition to the continuum, we detect a weak excess in the 9-11 um range, with an amplitude of 6% of the continuum. The shape of the feature can be matched by a mixture of silicates: amorphous forsterite/olivine, dirty crystalline olivine, and a hydrous silicate (montmorillonite). The presence of hydrous silicate suggests the parent bodies of those particles were formed in the inner solar nebula. Large particles dominate the size distribution, but at least some small particles (radii ~1 um) are required to produce the silicate emission feature. To compare the properties of zodiacal dust to dust around other main sequence stars, we reanalyzed the exozodiacal light spectrum for Beta Pic. The exozodiacal spectra are dominated by cold dust, with emission peaking in the far-infrared, while the zodiacal spectrum peaks around 20 um. The shape of the silicate feature from Beta Pic is nearly identical to that derived from the ISO spectrum of 51 Oph; both exozodiacal features are very different from that of the zodiacal light. The exozodiacal features are roughly triangular, peaking at 10.3 um while the zodiacal feature is more boxy.Comment: accepted to Icaru

Spitzer Infrared Spectrograph Detection of Molecular Hydrogen Rotational Emission towards Translucent Clouds

Using the Infrared Spectrograph on board the Spitzer Space Telescope, we have detected emission in the S(0), S(1), and S(2) pure-rotational (v = 0-0) transitions of molecular hydrogen (H_2) toward six positions in two translucent high Galactic latitude clouds, DCld 300.2–16.9 and LDN 1780. The detection of these lines raises important questions regarding the physical conditions inside low-extinction clouds that are far from ultraviolet radiation sources. The ratio between the S(2) flux and the flux from polycyclic aromatic hydrocarbons (PAHs) at 7.9 μm averages 0.007 for these six positions. This is a factor of about four higher than the same ratio measured toward the central regions of non-active Galaxies in the Spitzer Infrared Nearby Galaxies Survey. Thus, the environment of these translucent clouds is more efficient at producing rotationally excited H_2 per PAH-exciting photon than the disks of entire galaxies. Excitation analysis finds that the S(1) and S(2) emitting regions are warm (T ≳ 300 K), but comprise no more than 2% of the gas mass. We find that UV photons cannot be the sole source of excitation in these regions and suggest mechanical heating via shocks or turbulent dissipation as the dominant cause of the emission. The clouds are located on the outskirts of the Scorpius-Centaurus OB association and may be dissipating recent bursts of mechanical energy input from supernova explosions. We suggest that pockets of warm gas in diffuse or translucent clouds, integrated over the disks of galaxies, may represent a major source of all non-active galaxy H_2 emission

Exploring approximations to the GW self-energy ionic gradients

The accuracy of the many-body perturbation theory GW formalism to calculate electron-phonon coupling matrix elements has been recently demonstrated in the case of a few important systems. However, the related computational costs are high and thus represent strong limitations to its widespread application. In the present study, we explore two less demanding alternatives for the calculation of electron-phonon coupling matrix elements on the many-body perturbation theory level. Namely, we test the accuracy of the static Coulomb-hole plus screened-exchange (COHSEX) approximation and further of the constant screening approach, where variations of the screened Coulomb potential W upon small changes of the atomic positions along the vibrational eigenmodes are neglected. We find this latter approximation to be the most reliable, whereas the static COHSEX ansatz leads to substantial errors. Our conclusions are validated in a few paradigmatic cases: diamond, graphene and the C60 fullerene. These findings open the way for combining the present many-body perturbation approach with efficient linear-response theories

The Energetics of Molecular Gas in NGC 891 from H_2 and Far-infrared Spectroscopy

We have studied the molecular hydrogen energetics of the edge-on spiral galaxy NGC 891, using a 34 position map in the lowest three pure rotational H_2 lines observed with the Spitzer Infrared Spectrograph. The S(0), S(1), and S(2) lines are bright with an extinction-corrected total luminosity of ~2.8 × 10^7 L_☉, or 0.09% of the total-infrared luminosity of NGC 891. The H_2 line ratios are nearly constant along the plane of the galaxy—we do not observe the previously reported strong drop-off in the S(1)/S(0) line intensity ratio in the outer regions of the galaxy, so we find no evidence for the very massive cold CO-free molecular clouds invoked to explain the past observations. The H_2 level excitation temperatures increase monotonically indicating that there is more than one component to the emitting gas. More than 99% of the mass is in the lowest excitation (T_(ex) ~ 125 K) "warm" component. In the inner galaxy, the warm H_2 emitting gas is ~16% of the CO(1-0)-traced cool molecular gas, while in the outer regions the fraction is twice as high. This large mass of warm gas is heated by a combination of the far-UV photons from stars in photodissociation regions (PDRs) and the dissipation of turbulent kinetic energy. Including the observed far-infrared [O I] and [C II] fine-structure line emission and far-infrared continuum emission in a self-consistent manner to constrain the PDR models, we find essentially all of the S(0) and most (70%) of the S(1) line arise from low excitation PDRs, while most (80%) of the S(2) and the remainder of the S(1) line emission arise from low-velocity microturbulent dissipation

Massage Therapy for People with HIV

Massage therapists celebrated along with other complementary and alternative medicine (CAM) practitioners at the release of Eisenberg et al.\u27s follow-up of a national survey on the trends in the use of CAM in the United States from 1990-1997. Not only did the use of CAM increase from 33.8 percent to 42.1 percent, massage was one of the therapies that increased the most (Eisenberg et al., 1998). In addition, although 71.5 percent of the visits were not covered by any insurance, massage therapy was the second most popular CAM therapy used, accounting for 18.1 percent of the 628.8 million total visits (Eisenberg et al., 1998

Line-of-Sight Reddening Predictions: Zero Points, Accuracies, the Interstellar Medium, and the Stellar Populations of Elliptical Galaxies

Revised (B-V)_0-Mg_2 data for 402 elliptical galaxies are given to test reddening predictions which can also tell us both what the intrinsic errors are in this relationship among gE galaxy stellar populations, as well as details of nearby structure in the interstellar medium (ISM) of our Galaxy and of the intrinsic errors in reddening predictions. Using least-squares fits, the explicit 1-sigma errors in the Burstein-Heiles (BH) and the Schlegel et al. (IR) predicted reddenings are calculated, as well as the 1-sigma observational error in the (B-V)_0-Mg_2 for gE galaxies. It is found that, in directions with E(B-V)<0.100 mag (where most of these galaxies lie), 1-sigma errors in the IR reddening predictions are 0.006 to 0.009 in E(B-V) mag, those for BH reddening prediction are 0.011 mag, and the 1-sigma agreement between the two reddening predictions is 0.007 mag. IR predictions have an accuracy of 0.010-0.011 mag in directions with E(B-V)>= 0.100 mag, significantly better than those of the BH predictions (0.024-0.025). Gas-to-dust variations that vary by a factor of 3, both high and low, exist along many lines-of-sight in our Galaxy. The approx 0.02 higher reddening zero point in E(B-V) previously determined by Schlegel et al. is confirmed, primarily at the Galactic poles. Despite this, both methods also predict many directions with E(B-V)<0.015 mag. Independent evidence of reddening at the North Galactic pole is reviewed, with the conclusion that there still exists directions at the NGP that have E(B-V)<<0.01. Two lines of evidence suggest that IR reddenings are overpredicted in directions with high gas-to-dust ratios. As high gas-to-dust directions in the ISM also include the Galactic poles, this overprediction is the likely cause of the E(B-V) = 0.02 mag larger IR reddening zero point.Comment: 5 figure

Aromatic emission from the ionised mane of the Horsehead nebula

We study the evolution of the Aromatic Infrared Bands (AIBs) emitters across the illuminated edge of the Horsehead nebula and especially their survival and properties in the HII region. We present spectral mapping observations taken with the Infrared Spectrograph (IRS) at wavelengths 5.2-38 microns. A strong AIB at 11.3 microns is detected in the HII region, relative to the other AIBs at 6.2, 7.7 and 8.6 microns. The intensity of this band appears to be correlated with the intensity of the [NeII] at 12.8 microns and of Halpha, which shows that the emitters of the 11.3 microns band are located in the ionised gas. The survival of PAHs in the HII region could be due to the moderate intensity of the radiation field (G0 about 100) and the lack of photons with energy above about 25eV. The enhancement of the intensity of the 11.3 microns band in the HII region, relative to the other AIBs can be explained by the presence of neutral PAHs. Our observations highlight a transition region between ionised and neutral PAHs observed with ideal conditions in our Galaxy. A scenario where PAHs can survive in HII regions and be significantly neutral could explain the detection of a prominent 11.3 microns band in other Spitzer observations.Comment: 9 pages, 9 figures, accepted for publication in A&