Polarized Infrared Emission by Polycyclic Aromatic Hydrocarbons resulting from Anisotropic Illumination

We study the polarized infrared emission by Polycyclic Aromatic Hydrocarbons (PAHs), when anisotropically illuminated by UV photons. PAH molecules are modeled as planar disks with in-plane and out-of-plane vibrational dipoles. As first pointed out by Leger (1988), infrared emission features resulting from in-plane and out-of-plane modes should have orthogonal polarization directions. We show analytically how the degree of polarization depends on the viewing geometry and the molecule's internal alignment between principal axis of inertia and angular momentum, which gets worse after photon absorption. Longer wavelength features, emitted after better internal alignment is recovered, should be more strongly polarized. The degree of polarization for uni-directional illumination (e.g., by a star) is larger than for diffuse illumination (e.g., by a disk galaxy), all else being equal. For PAHs in the Cold Neutral Medium, the predicted polarization is probably too small to distinguish from the contribution of linear dichroism by aligned foreground dust. The level of polarization predicted for PAH emission from the Orion Bar is only ~0.06% at 3.3 microns; Sellgren et al. (1988) report a much larger value, 0.86+-0.28%, which suggests that the smallest PAHs may have moderately suprathermal rotation rates. Future observations of (or upper limits on) the degree of polarization for the Orion Bar or for dust above edge-on galaxies (e.g., NGC 891 or M82) may constrain the internal alignment of emitting PAHs, thus providing clues to their rotational dynamics.Comment: 9 pages, 4 figures, 1 table, submitted to Ap

Constraining Spinning Dust Parameters with the WMAP Five-Year Data

We characterize spinning dust emission in the warm ionized medium by comparing templates of Galactic dust and Halpha with the 5-year maps from the Wilkinson Microwave Anisotropy Probe. The Halpha-correlated microwave emission deviates from the thermal bremsstrahlung (free-free) spectrum expected for ionized gas, exhibiting an additional broad bump peaked at ~40 GHz which provides ~20% of the peak intensity. We confirm that the bump is consistent with a modified Draine & Lazarian (1998) spinning dust model, though the peak frequency of the emission is somewhat lower than the 50 GHz previously claimed. This frequency shift results from systematic errors in the large-scale modes of the 3-year WMAP data which have been corrected in the 5-year data release. We show that the bump is not the result of errors in the Halpha template by analyzing regions of high free-free intensity, where the WMAP K-band map may be used as the free-free template. We rule out a pure free-free spectrum for the Halpha-correlated emission at high confidence: ~27sigma for the nearly full-sky fit, even after marginalizing over the CMB cross-correlation bias. We also extend the previous analysis by searching the parameter space of the Draine & Lazarian model but letting the amplitude float. The best fit for reasonable values of the characteristic electric dipole moment and density requires an amplitude factor of ~0.3. This suggests that small PAHs in the warm ionized medium are depleted by a factor of ~3.Comment: 17 pages, 13 figures; submitted to Ap

CMBPol Mission Concept Study: Foreground Science Knowledge and Prospects

We report on our knowledge of Galactic foregrounds, as well as on how a CMB satellite mission aiming at detecting a primordial B-mode signal (CMBPol) will contribute to improving it. We review the observational and analysis techniques used to constrain the structure of the Galactic magnetic field, whose presence is responsible for the polarization of Galactic emissions. Although our current understanding of the magnetized interstellar medium is somewhat limited, dramatic improvements in our knowledge of its properties are expected by the time CMBPol flies. Thanks to high resolution and high sensitivity instruments observing the whole sky at frequencies between 30 GHz and 850 GHz, CMBPol will not only improve this picture by observing the synchrotron emission from our galaxy, but also help constrain dust models. Polarized emission from interstellar dust indeed dominates over any other signal in CMBPol's highest frequency channels. Observations at these wavelengths, combined with ground-based studies of starlight polarization, will therefore enable us to improve our understanding of dust properties and of the mechanism(s) responsible for the alignment of dust grains with the Galactic magnetic field. CMBPol will also shed new light on observations that are presently not well understood. Morphological studies of anomalous dust and synchrotron emissions will indeed constrain their natures and properties, while searching for fluctuations in the emission from heliospheric dust will test our understanding of the circumheliospheric interstellar medium. Finally, acquiring more information on the properties of extra-Galactic sources will be necessary in order to maximize the cosmological constraints extracted from CMBPol's observations of CMB lensing. (abridged)Comment: 43 pages, 7 figures, 2 table

Foreground Science Knowledge and Prospects

Detecting “B‐mode” (i.e., divergence free) polarization in the Cosmic Microwave Background (CMB) would open a new window on the very early Universe. However, the polarized microwave sky is dominated by polarized Galactic dust and synchrotron emissions, which may hinder our ability to test inflationary predictions. In this paper, we report on our knowledge of these “Galactic foregrounds,” as well as on how a CMB satellite mission aiming at detecting a primordial B‐mode signal (“CMBPol”) will contribute to improving it. We review the observational and analysis techniques used to constrain the structure of the Galactic magnetic field, whose presence is responsible for the polarization of Galactic emissions. Although our current understanding of the magnetized interstellar medium is somewhat limited, dramatic improvements in our knowledge of its properties are expected by the time CMBPol flies. Thanks to high resolution and high sensitivity instruments observing the whole sky at frequencies between 30 GHz and 850 GHz, CMBPol will not only improve this picture by observing the synchrotron emission from our galaxy, but also help constrain dust models. Polarized emission form interstellar dust indeed dominates over any other signal in CMBol’s highest frequency channels. Observations at these wavelengths, combined with ground‐based studies of starlight polarization, will therefore enable us to improve our understanding of dust properties and of the mechanism(s) responsible for the alignment of dust grains with the Galactic magnetic field. CMBPol will also shed new light on observations that are presently not well understood. Morphological studies of anomalous dust and synchrotron emissions will indeed constrain their natures and properties, while searching for fluctuations in the emission from heliospheric dust will test our understanding of the circumheliospheric interstellar medium. Finally, acquiring more information on the properties of extra‐Galactic sources will be necessary in order to maximaize the cosmological constrainsts extracted from CMBPol’s observations of CMB lensing

recommendations from the CVBD World Forum

The human-animal bond has been a fundamental feature of mankind's history for millennia. The first, and strongest of these, man's relationship with the dog, is believed to pre-date even agriculture, going back as far as 30,000 years. It remains at least as powerful today. Fed by the changing nature of the interactions between people and their dogs worldwide and the increasing tendency towards close domesticity, the health of dogs has never played a more important role in family life. Thanks to developments in scientific understanding and diagnostic techniques, as well as changing priorities of pet owners, veterinarians are now able, and indeed expected, to play a fundamental role in the prevention and treatment of canine disease, including canine vector-borne diseases (CVBDs).The CVBDs represent a varied and complex group of diseases, including anaplasmosis, babesiosis, bartonellosis, borreliosis, dirofilariosis, ehrlichiosis, leishmaniosis, rickettsiosis and thelaziosis, with new syndromes being uncovered every year. Many of these diseases can cause serious, even life-threatening clinical conditions in dogs, with a number having zoonotic potential, affecting the human population.Today, CVBDs pose a growing global threat as they continue their spread far from their traditional geographical and temporal restraints as a result of changes in both climatic conditions and pet dog travel patterns, exposing new populations to previously unknown infectious agents and posing unprecedented challenges to veterinarians.In response to this growing threat, the CVBD World Forum, a multidisciplinary group of experts in CVBDs from around the world which meets on an annual basis, gathered in Nice (France) in 2011 to share the latest research on CVBDs and discuss the best approaches to managing these diseases around the world.As a result of these discussions, we, the members of the CVBD Forum have developed the following recommendations to veterinarians for the management of CVBDs

Vector-Borne Diseases - constant challenge for practicing veterinarians: recommendations from the CVBD World Forum

The human-animal bond has been a fundamental feature of mankind's history for millennia. The first, and strongest of these, man's relationship with the dog, is believed to pre-date even agriculture, going back as far as 30,000 years. It remains at least as powerful today. Fed by the changing nature of the interactions between people and their dogs worldwide and the increasing tendency towards close domesticity, the health of dogs has never played a more important role in family life. Thanks to developments in scientific understanding and diagnostic techniques, as well as changing priorities of pet owners, veterinarians are now able, and indeed expected, to play a fundamental role in the prevention and treatment of canine disease, including canine vector-borne diseases (CVBDs)

Constraining Spinning Dust Parameters With the WMAP Five-Year Data

We characterize spinning dust emission in the warm ionized medium (WIM) by comparing templates of Galactic dust and Hα with the five-year maps from the Wilkinson Microwave Anisotropy Probe (WMAP). The Hα-correlated microwave emission deviates from the thermal bremsstrahlung (free-free) spectrum expected for ionized gas, exhibiting an additional broad bump peaked at ~40 GHz which provides ~20% of the peak intensity. We confirm that the bump is consistent with a modified Draine and Lazarian spinning dust model, though the peak frequency of the emission is somewhat lower than the 50 GHz previously claimed. This frequency shift results from systematic errors in the large-scale modes of the three-year WMAP data which have been corrected in the five-year data release. We show that the bump is not the result of errors in the Hα template by analyzing regions of high free-free intensity, where the WMAP K-band map may be used as the free-free template. We rule out a pure free-free spectrum for the Hα-correlated emission at high confidence: ~27σ for the nearly full-sky fit, even after marginalizing over the cosmic microwave background cross-correlation bias. We also extend the previous analysis by searching the parameter space of the Draine and Lazarian model but letting the amplitude float. The best fit for reasonable values of the characteristic electric dipole moment and density requires an amplitude factor of ~0.3. This suggests that small polycyclic aromatic hydrocarbons in the WIM are depleted by a factor of ~3.Astronom