A Three-Dimensional Analytical Model of the Interstellar Extinction within the Nearest Kiloparsec

We examine the effect of Galactic diffractive interstellar scintillation as a means of explaining the reported deficit of fast radio burst (FRB) detections at low Galactic latitude. We model the unknown underlying FRBflux density distribution as a power lawwith a rate scaling as S−5/2+δ ν and account for the fact that the FRBs are detected at unknown positions within the telescope beam. We find that the event rate of FRBs located off the Galactic plane may be enhanced by a factor of ∼30–300 per cent relative to objects near the Galactic plane without necessarily affecting the slope of the distribution. For FRBs whose flux densities are subject to relatively weak diffractive scintillation, as is typical for events detected at high Galactic latitudes, we demonstrate that an effect associated with Eddington bias is responsible for the enhancement. The magnitude of the enhancement increases with the steepness of the underlying flux density distribution, so that existing limits on the disparity in event rates between high and lowGalactic latitudes suggest that the FRB population has a steep differential flux density distribution, scaling as S−3.5 ν or steeper. Existing estimates of the event rate in the flux density range probed by the High Time Resolution Universe survey overestimate the true rate by a factor of ∼3.

The contribution from the residuals of the foreground can have a significant impact on the temperature maps of the Cosmic Microwave Background (CMB). Mostly, the focus has been on the galactic plane, when foreground cleaning has taken place. However, in this paper, we will investigate the possible foreground contamination, from sources outside the galactic plane in the CMB maps. We will analyze the correlation between the Faraday rotation map and the CMB temperature map. The Faraday rotation map is dependent on the galactic magnetic field, as well as the thermal electron density, and both may contribute to the CMB temperature. We find that the standard deviation for the mean cross correlation deviate from that of simulations at the 99.9% level. Additionally, a comparison between the CMB temperature extrema and the extremum points of the Faraday rotation is also performed, showing a general overlap between the two. Also we find that the CMB Cold Spot is located at an area of strong negative cross correlation, meaning that it may be explained by a galactic origin. Further, we investigate nearby supernova remnants in the galaxy, traced by the galactic radio loops. These super nova remnants are located at high and low galactic latitude, and thus well outside the galactic plane. We find some correlation between the Faraday Rotation and the CMB temperature, at select radio loops. This indicate, that the galactic foregrounds may affect the CMB, at high galactic latitudes

A signal of high-energy extraterrestrial neutrinos from unknown source(s) was\nrecently discovered by the IceCube experiment. Neutrinos are always produced\ntogether with gamma-rays, but the gamma-ray flux from extragalactic sources is\nsuppressed due to attenuation in the intergalactic medium. We report the\ndiscovery of a gamma-ray excess at high Galactic latitudes starting at energies\n300 GeV in the data of the Fermi telescope. We show that the multi-TeV\ngamma-ray diffuse emission has spectral characteristics at both low and high\nGalactic latitudes compatible with those of the IceCube high neutrino signal in\nthe same sky regions. This suggests that these gamma-rays are the counterpart\nof the IceCube neutrino signal, implying that a sizable part of the IceCube\nneutrino flux originates from the Milky Way. We argue that the diffuse neutrino\nand gamma-ray signal at high Galactic latitudes originates either from\npreviously unknown nearby cosmic ray "PeVatron" source(s), an extended Galactic\nCR halo or from decays of heavy dark matter particles.\n

We constrain the spectral index of polarized synchrotron emission, βs, by correlating the recently released 2.3 GHz S-Band Polarization All Sky Survey (S-PASS) data with the 23 GHz 9-year Wilkinson Microwave Anisotropy Probe (WMAP) sky maps. We subdivide the S-PASS field, which covers the southern ecliptic hemisphere, into 95 15° ×15° regions and estimate the spectral index of polarized synchrotron emission within each region using a simple but robust T–T plot technique. Three different versions of the S-PASS data are considered, corresponding to: no correction for Faraday rotation; Faraday correction based on the rotation measure model presented by the S-PASS team; or Faraday correction based on a rotation measure model presented by Hutschenreuter and Enßlin. We find that the correlation between S-PASS and WMAP is strongest when applying the S-PASS model. Adopting this correction model, we find that the mean spectral index of polarized synchrotron emission gradually steepens from βs ≈ −2.8 at low Galactic latitudes to βs ≈ −3.3 at high Galactic latitudes, in good agreement with previously published results. The flat spectral index at the low Galactic latitudes is likely partly due to depolarization effects. Finally, we consider two special cases defined by the BICEP2 and SPIDER fields and obtain mean estimates of βBICEP2 = −3.22 ± 0.06 and βSPIDER = −3.21 ± 0.03, respectively. Adopting the bandpass filtered WMAP 23 GHz sky map to only include angular scales between 2° and 10° as a spatial template, we constrain the root-mean-square synchrotron polarization amplitude to be less than 0.03 μK (0.009 μK) at 90 GHz (150 GHz) for the BICEP2 field, corresponding roughly to a tensor-to-scalar ratio of r ≲ 0.02 (r ≲ 0.005). Very similar constraints are obtained for the SPIDER field. A comparison with a similar analysis performed in the 23–33 GHz range suggests a flattening of about Δβs ∼ 0.1 ± 0.2 from low to higher frequencies, but with no statistical significance due to high uncertainties.

\nIn this contribution we present results from the QUEST RR Lyrae Survey of the thick disk. The survey spans ~480 sq. deg. at low latitude |b| < 30°, with multi-epoch VRI observations, obtained with the QUEST-I camera at the 1m Jürgen Stock Schmidt telescope located at the National Astronomical Observatory of Venezuela. This constitutes the first deep RR Lyrae survey of the Galactic thick disk conducted at low galactic latitudes, covering simultaneously a large range in radial (8<R(kpc)<60) and perpendicular (0<|z|(kpc)<20) distance from the Galactic Plane. The spatial coverage of the survey together with the multi-band multi-epoch photometry allowed for the derivation of the thick disk structural parameters from in situ RR Lyrae stars having accurate distances (errors <7%) and individual reddenings derived from each star’s color curve at minimum light. Moreover, the use of RR Lyrae stars as tracers ensures negligible contamination from the Galactic thin disk. We find a thick disk mean scale height hZ = 0.94 ± 0.11kpc and scale length hR = 3.2 ± 0.4kpc, derived from the vertical and radial mean density profiles of RR Lyrae stars. We also find evidence of thick disk flaring and results that may suggest the thick disk radial density profile shows signs of antitruncation. We discuss our findings in the context of recent thick disk formation models.\n

Interstellar dust at high Galactic latitudes can influence astronomical foreground subtraction, produce diffuse scattered light, and soften the UV spectra of quasars. In a sample of 94 sight lines toward quasars at high latitude and low extinction, we evaluate the interstellar “gas-to-dust ratio” N H/E(B − V), using hydrogen column densities (H i and H2) and far-IR (FIR) estimates of dust reddening. In the Galactic plane, this ratio is 6.0 ± 0.2 (in units of 1021 cm−2 mag−1). On average, recent Planck estimates of E(B − V) in low-reddening sight lines are 12% higher than those from Schlafly & Finkbeiner, and N H I exhibits significant variations when measured at different radio telescopes. In a sample of 51 quasars with measurements of both H i and H2 and 0.01 ≤ E(B − V) ≲ 0.1, we find mean ratios 10.3 ± 0.4 (gas at all velocities) and 9.2 ± 0.3 (low-velocity only) using Planck E(B − V) data. High-latitude H2 fractions are generally small (2%–3% on average), although nine of 39 sight lines at ∣b∣ ≥ 40° have f H2 of 1%–17%. Because FIR-inferred E(B − V) is sensitive to modeled dust temperature T d and emissivity index β, gas-to-dust ratios have large, asymmetric errors at low E(B − V). The ratios are elevated in sight lines with high-velocity clouds, which contribute N H but little reddening. In Complex C, the ratio decreases by 40% when high-velocity gas is excluded. Decreases in dust content are expected in low-metallicity gas above the Galactic plane, resulting from grain destruction in shocks, settling to the disk, and thermal sputtering in hot halo gas.

There is evidence that job strain increases the risk of a first coronary heart disease (CHD) event. However, little is known about its association with the risk of recurrent CHD events after a first myocardial infarction (MI). To determine whether job strain increases the risk of recurrent CHD events. Prospective cohort study of 972 men and women aged 35 to 59 years who returned to work after a first MI and were then followed up between February 10, 1996, and June 22, 2005. Patients were interviewed at baseline (on average, 6 weeks after their return to work), then after 2 and 6 years subsequently. Job strain, a combination of high psychological demands and low decision latitude, was evaluated in 4 quadrants: high strain (high demands and low latitude), active (high demands and high latitude), passive (low demands and low latitude), and low strain. A chronic job strain variable was constructed based on the first 2 interviews, and patients were divided into those exposed to high strain at both interviews and those unexposed to high strain at 1 or both interviews. The survival analyses were presented separately for 2 periods: before 2.2 years and at 2.2 years and beyond. The outcome was a composite of fatal CHD, nonfatal MI, and unstable angina. The outcome was documented in 206 patients. In the unadjusted analysis, chronic job strain was associated with recurrent CHD in the second period after 2.2 years of follow-up (hazard ratio [HR], 2.20; 95% CI, 1.32-3.66; respective event rates for patients exposed and unexposed to chronic job strain, 6.18 and 2.81 per 100 person-years). Chronic job strain remained an independent predictor of recurrent CHD in a multivariate model adjusted for 26 potentially confounding factors (HR, 2.00; 95% CI, 1.08-3.72). Chronic job strain after a first MI was associated with an increased risk of recurrent CHD.

view Abstract Citations (36) References (55) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Mean secular parallax at low galactic latitude. Stone, R. C. Abstract Very accurate relative proper motions are determined for 1332 stars in 62 regions at very low galactic latitude (less than 10 deg in absolute value). These data are supplemented with 27 additional regions of proper motions of faint stars in the directions of open clusters, and a statistical analysis of all these motions is performed to determine the position of the solar apex for faint stars and to calibrate the mean secular parallax at low galactic latitude. It is found that the apex for faint stars is near the basic solar apex and that the parallax calibration confirms the smaller values previously obtained on the basis of a much smaller sample of proper-motion regions. This calibration is used to determine the peculiar space motions of O stars in the solar neighborhood, from which motions are computed the semimajor axes and vertex direction of the O-star velocity ellipsoid. The results show that the vertex direction is into the fourth velocity quadrant, that 20% of the O stars are runaways, and that most O stars were probably born near the galactic plane. Publication: The Astronomical Journal Pub Date: April 1978 DOI: 10.1086/112215 Bibcode: 1978AJ.....83..393S Keywords: Astrometry; Parallax; Star Clusters; Star Distribution; Stellar Motions; Least Squares Method; O Stars; Open Clusters; Photoelectric Emission; Radial Velocity; Stellar Luminosity; Astronomy; Faint Stars:Proper Motions; O Stars:Runaway Stars; Solar Apex full text sources ADS | data products SIMBAD (64)

In a recent much-quoted paper, Valentijn has used the ESO-Uppsala galaxy catalogue to carry out the classical surface brightness against inclination test to try to measure the opacity of spiral galaxies. From his results he infers, contrary to previous work, that galaxies are optically thick out to large radii. In this paper we show that the methods and selection criteria used by Valentijn will constrain his galaxies to have a constant surface brightness independent of their inclination, whatever their actual optical depth. We demonstrate, first, the practical efficacy of such selection biases by showing that the observed ranges of surface brightness for ESO galaxies at high and low Galactic latitude are the same, despite the obvious foreground extinction of each individual galaxy in the latter group. We then show, from simulations, that galaxies of a particular preferred observed surface brightness are always more likely to be included in the sample regardless of their inclination; if a wide range of intrinsic surface brightnesses actually exists then a sample of inclined galaxies will select the same observed range of surface brightness as a sample of face-on galaxies. Because of these strong selection biases, the original question addressed by Valentijn and also by Burstein, Haynes & Faber, of whether spiral galaxies are opaque or not, and if so out to what radii, cannot be answered using the classical techniques.

We analyse observational correlations for three elements entering into the composition of interstellar silicate and oxide grains. Using current solar abundances (Asplund et al. 2009), we convert the gas-phase abundances into dust-phase abundances for 196 sightlines. We deduce a sharp difference in abundances for sightlines located at low ($|b|<30\degr$) and high ($|b|>30\degr$) galactic latitudes. For high-latitude stars the ratios Mg/Si and Fe/Si in dust are close to 1.5. For disk stars they are reduced to ${\rm Mg/Si} \sim 1.2$ and ${\rm Fe/Si} \sim 1.05$. The derived numbers indicate that 1) the dust grains cannot be the mixture of silicates with olivine and pyroxene composition only and some amount of magnesium or iron (or both) should be in another population and 2) the destruction of Mg-rich grains in the warm medium is more effective than of Fe-rich grains. We reveal a decrease of dust-phase abundances and correspondingly an increase of gas-phase abundances with distance $D$ for stars with $D\ga 400$\,pc. We attribute this fact to an observational selection effect: a systematic trend toward smaller observed hydrogen column density for distant stars. We find differences in abundances for disk stars with low ($E({\rm B-V}) \la 0.2$) and high ($E({\rm B-V}) \ga 0.2$) reddenings which reflect the distinction between the sightlines passing through diffuse and translucent interstellar clouds. For Scorpius-Ophiuchus we detect an uniform increase of dust-phase abundances of Mg and Si with an increase of the ratio of total to selective extinction $R_{\rm V}$ and a decrease of the strength of the far-UV extinction. This is the first evidence for a growth of Mg-Si grains due to accretion in the interstellar medium.

We discuss the Galactic foreground emission between 20 and 100 GHz based on observations by Planck and WMAP. The total intensity in this part of the spectrum is dominated by free-free and spinning dust emission, whereas the polarized intensity is dominated by synchrotron emission. The Commander component-separation tool has been used to separate the various astrophysical processes in total intensity. Comparison with radio recombination line templates verifies the recovery of the free-free emission along the Galactic plane. Comparison of the high-latitude Hα emission with our free-free map shows residuals that correlate with dust optical depth, consistent with a fraction (≈30%) of Hα having been scattered by high-latitude dust. We highlight a number of diffuse spinning dust morphological features at high latitude. There is substantial spatial variation in the spinning dust spectrum, with the emission peak (in I_ν) ranging from below 20 GHz to more than 50 GHz. There is a strong tendency for the spinning dust component near many prominent H II regions to have a higher peak frequency, suggesting that this increase in peak frequency is associated with dust in the photo-dissociation regions around the nebulae. The emissivity of spinning dust in these diffuse regions is of the same order as previous detections in the literature. Over the entire sky, the Commander solution finds more anomalous microwave emission (AME) than the WMAP component maps, at the expense of synchrotron and free-free emission. This can be explained by the difficulty in separating multiple broadband components with a limited number of frequency maps. Future surveys, particularly at 5–20 GHz, will greatly improve the separation by constraining the synchrotron spectrum. We combine Planck and WMAP data to make the highest signal-to-noise ratio maps yet of the intensity of the all-sky polarized synchrotron emission at frequencies above a few GHz. Most of the high-latitude polarized emission is associated with distinct large-scale loops and spurs, and we re-discuss their structure. We argue that nearly all the emission at 40deg &gt; l &gt; −90deg is part of the Loop I structure, and show that the emission extends much further in to the southern Galactic hemisphere than previously recognised, giving Loop I an ovoid rather than circular outline. However, it does not continue as far as the “Fermi bubble/microwave haze”, making it less probable that these are part of the same structure. We identify a number of new faint features in the polarized sky, including a dearth of polarized synchrotron emission directly correlated with a narrow, roughly 20deg long filament seen in Hα at high Galactic latitude. Finally, we look for evidence of polarized AME, however many AME regions are significantly contaminated by polarized synchrotron emission, and we find a 2σ upper limit of 1.6% in the Perseus region.

Pattern of variation of TEC, hmF2 and foF2, and their correlation during the geomagnetic storm time conditions

Gravity waves (GW) transport momentum flux (MF) and energy across the lower, middle and upper atmosphere. Global Navigation Satellite System (GNSS) radio occultation (RO) is one of the measuring techniques used onboard satellites to provide vertical temperature profiles with global and permanent coverage. These retrievals may be applied in the study of GW. Most of the analysis methods provide absolute GWMF but are missing its net direction. This happens because the procedures can deduce the orientation but not the propagation sign of GW and hence the full direction of MF. We apply here a method that allows the net calculation with four close in space and time RO soundings (quartets). We use about 10,000 daily retrievals from 1 March 2022 to 28 February 2023 to study the seasonal and latitudinal characteristics of net GWMF in the height interval from 20 to 35 km. About 600 quartets were found. The calculated zonal MF and drag exhibited negative minima at middle and high latitudes during winter in the Southern Hemisphere. This well‐known characteristic is usually mainly assigned to orographic sources. A similar intensity in zonal MF and drag is found during the same season at low latitudes. Meridional components are generally less significant. Besides finding the correct sign of the GWMF and the corresponding forcing on the mean flow, the quartets method also allows the determination of the horizontal and vertical wavelengths, the amplitude and sign of the vertical wave phase velocity and the intrinsic frequencies. The global statistics of these parameters are shown and each one exhibits a similar distribution shape across latitude bands. Large differences in the frequency of cases in vertical phase velocity sign appear only at low and high positive latitudes. The most even distribution of GW intrinsic frequency is found at low latitudes. We estimate that absolute MF calculations by methods assuming only upward GW propagation may produce a bias not larger than 40%. The increase of satellite measuring devices achieved in the last years due to the release of new missions led to a high spatial and temporal density of profiles that may allow the attainment of net GWMF climatologies over a seasonal time scale and about 4,000 km latitude bands but this performance may be even improved if the amount of retrievals continues to rise.

We construct a simple cloud model for a Venus general circulation model (GCM), which includes condensable gases of H2O and H2SO4 vapors, and condensation, evaporation, and sedimentation of sulfuric acid cloud particles. The zonally averaged mass loading of the cloud reproduced in the model takes its maximum and minimum in high and middle latitudes, respectively. This latitudinal distribution is consistent with the infrared measurements. The thick cloud is formed in high latitudes at 43–55 km altitudes by vertical winds associated with disturbances enhanced in the low static stability layer. The moderately thick cloud in low latitudes is attributed mainly to the transport of H2SO4 vapor by the mean meridional circulation. The horizontal cloud distribution in low latitudes has zonal wave numbers 1 and 2 structures, which change in time significantly. These characteristics of the low‐latitude cloud would be associated with atmospheric waves in the cloud layer. The mixing ratio of H2O vapor increases with latitude in the cloud layer due to the vertical wind disturbances in the low static stability layer in high latitudes. This latitudinal trend is qualitatively consistent with the infrared measurements. The mixing ratio of H2SO4 vapor increases with latitude in the subcloud layer because a large amount of the cloud is evaporated there due to the sedimentation of cloud particles in the thick lower cloud in the polar region. The present results suggest that the Venus cloud distribution in the lower cloud layer is strongly affected by waves and/or disturbances as well as the mean meridional circulation.

Seasonal variations of the ionospheric effects of geomagnetic storms at different latitudes of East Asia