Faraday Rotation as a diagnostic of Galactic foreground contamination of CMB maps

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 latitudesComment: 13 pages, 22 figures, 6 table

TRIS I: Absolute Measurements of the Sky Brightness Temperature at 0.6, 0.82 and 2.5 GHz

At frequencies close to 1 GHz the sky diffuse radiation is a superposition of radiation of Galactic origin, the 3 K Relic or Cosmic Microwave Background Radiation, and the signal produced by unresolved extragalactic sources. Because of their different origin and space distribution the relative importance of the three components varies with frequency and depends on the direction of observation. With the aim of disentangling the components we built TRIS, a system of three radiometers, and studied the temperature of the sky at $\nu =0.6$, $\nu = 0.82$ and $\nu = 2.5$ GHz using geometrically scaled antennas with identical beams (HPBW = $18^{\circ} \times 23^{\circ}$). Observations included drift scans along a circle at constant declination $\delta=+42^{\circ}$ which provided the dependence of the sky signal on the Right Ascension, and absolute measurement of the sky temperature at selected points along the same scan circle. TRIS was installed at Campo Imperatore (lat. = $42^{\circ}~26'$ N, long.= $13^{\circ}~33'$, elevation = 2000 m a.s.l.) in Central Italy, close to the Gran Sasso Laboratory.Comment: Accepted for publication in The Astrophysical Journa

All-sky Galactic radiation at 45 MHz and spectral index between 45 and 408 MHz

Aims: We study the Galactic large-scale synchrotron emission by generating a reliable all-sky spectral index map and temperature map at 45 MHz. Methods: We use our observations, the published all-sky map at 408 MHz, and a bibliographical compilation to produce a map corrected for zero-level offset and extragalactic contribution. Results: We present full sky maps of the Galactic emission at 45 MHz and the Galactic spectral index between 45 and 408 MHz with an angular resolution of 5\degs. The spectral index varies between 2.1 and 2.7, reaching values below 2.5 at low latitude because of thermal free-free absorption and its maximum in the zone next to the Northern Spur.Comment: A&A accepte

Imprint of Intergalactic Shocks on the Radio Sky

Strong intergalactic shocks are a natural consequence of structure formation in the universe. They are expected to deposit large fractions of their energy in relativistic electrons (xi_e~0.05 according to SNR observations) and magnetic fields (xi_B~0.01 according to cluster halo observations). We calculate the synchrotron emission from such shocks using an analytical model, calibrated with a hydrodynamical LCDM simulation. The resulting signal composes a large fraction of the extragalactic radio background (ERB) below 500 MHz. The associated angular fluctuations dominate the sky for frequencies nu<10 GHz and angular scales arcmin-deg (after a modest removal of point sources), provided that xi_e*xi_B>3*10^-4. The fluctuating signal is most pronounced for nu<500 MHz, dominating the sky even for xi_e*xi_B=5*10^-5. The signal will be easily observable by next generation radio telescopes such as LOFAR and SKA, and is marginally observable with present telescopes. It may be identified using cross-correlations with tracers of large scale structure, possibly even in existing <10 GHz CMB anisotropy maps and high resolution ~1 GHz radio surveys. Detection of the signal will provide the first identification of intergalactic shocks and of the WHIM, and gauge the unknown intergalactic magnetic field. We show that existing observations of the diffuse <500 MHz radio background are well fit by a simple, double-disk Galactic model, precluding a direct identification of the diffuse ERB. Modelling the frequency-dependent anisotropy pattern observed at very low (1-10 MHz) frequencies can disentangle the distributions of Galactic cosmic-rays, ionized gas and magnetic fields. Space missions such as ALFA will thus provide important insight into the structure and composition of our Galaxy (abridged).Comment: Accepted for publication in ApJ. Presentation improved and references adde

Planck 2015 results: XXV. Diffuse low-frequency Galactic foregrounds

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 H\u3b1 emission with our free-free map shows residuals that correlate with dust optical depth, consistent with a fraction (\ue2\u2030 30%) of H\u3b1 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\u3bd) 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 H\u3b1 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 2\u3c3 upper limit of 1.6% in the Perseus region

Distances to the Origem and the Monoceros loops

Using the Supernova Remnants (SNR) hypothesis for the radio loops, distances of the Origem and the Monoceros loops were calculated from the surface brightness and the angular diameters at 1420 MHz. The data were taken from the northen sky radio continuum survey at 1420 MHz (Reich and Reich, 1986) while the surface brightness-diameter (Σ − D) relation for SNR was taken from Berkhuijsen (1973). The distances of two loops determined here are larger than earlier ones, have radio astronomical roots and smaller relative errors