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Spillover and diffraction sidelobe contamination in a double-shielded experiment for mapping Galactic synchrotron emission  [PDF]
C. Tello,T. Villela,G. F. Smoot,M. Bersanelli,N. Figueiredo,G. De Amici,M. Bensadoun,C. A. Wuensche,S. Torres
Physics , 2000, DOI: 10.1051/aas:2000256
Abstract: We have analyzed observations from a radioastronomical experiment to survey the sky at decimetric wavelengths along with feed pattern measurements in order to account for the level of ground contamination entering the sidelobes. A major asset of the experiment is the use of a wire mesh fence around the rim-halo shielded antenna with the purpose of levelling out and reducing this source of stray radiation for zenith-centered 1-rpm circular scans. We investigate the shielding performance of the experiment by means of a geometric diffraction model in order to predict the level of the spillover and diffraction sidelobes in the direction of the ground. Using 408 MHz and 1465 MHz feed measurements, the model shows how a weakly-diffracting and unshielded antenna configuration becomes strongly-diffracting and double-shielded as far-field diffraction effects give way to near-field ones. Due to the asymmetric response of the feeds, the orientation of their radiation fields with respect to the secondary must be known a priori before comparing model predictions with observational data. By adjusting the attenuation coefficient of the wire mesh the model is able to reproduce the amount of differential ground pick-up observed during test measurements at 1465 MHz.
Mapping the Galactic Free-Free Foreground via Interstellar H-Alpha Emission  [PDF]
R. J. Reynolds,L. M. Haffner
Physics , 2000,
Abstract: Recently completed H-Alpha surveys of large portions of the sky can be used to create maps of the free-free intensity distribution at high Galactic latitude that are independent of the spectral fits to the CMB data. This provides an opportunity to test the accuracy of the spectral fitting procedures and to search for other sources of Galactic forground contamination that could be confused spectrally with the free-free, such as spinning dust grains. The Wisconsin H-Alpha Mapper (WHAM) survey has sampled the sky north of declination -30 deg at about one degree angular resolution and has revealed that, except for a few isolated regions of enhanced emission, \Delta T_{ff} (30 GHz) < 30 micro-K at Galactic latitudes near 15 deg, decreasing to \Delta T_{ff} (30 GHz) < 4 mircro-K at latitudes above 50 deg. Also in progress are H-Alpha surveys that sample the sky at higher angular resolution.
The COBE Diffuse Infrared Background Experiment Search for the Cosmic Infrared Background: III. Separation of Galactic Emission from the Infrared Sky Brightness  [PDF]
R. G. Arendt,N. Odegard,J. L. Weiland,T. J. Sodroski,M. G. Hauser,E. Dwek,T. Kelsall,S. H. Moseley,R. F. Silverberg,D. Leisawitz,K. Mitchell,W. T. Reach,E. L. Wright
Physics , 1998, DOI: 10.1086/306381
Abstract: The Cosmic Infrared Background (CIB) is hidden behind veils of foreground emission from our own solar system and Galaxy. This paper describes procedures for removing the Galactic IR emission from the 1.25 - 240 micron COBE DIRBE maps as steps toward the ultimate goal of detecting the CIB. The Galactic emission models are carefully chosen and constructed so that the isotropic CIB is completely retained in the residual sky maps. We start with DIRBE data from which the scattered light and thermal emission of the interplanetary dust (IPD) cloud have already been removed. Locations affected by the emission from bright compact and stellar sources are excluded from the analysis. The unresolved emission of faint stars at near- and mid-IR wavelengths is represented by a model based on Galactic source counts. The 100 micron DIRBE observations are used as the spatial template for the interstellar medium (ISM) emission at high latitudes. Correlation of the 100 micron data with H I column density allows us to isolate the component of the observed emission that is associated with the ISM. Limits are established on the far-IR emissivity of the diffuse ionized medium, which indicate a lower emissivity per H nucleus than in the neutral medium. At 240 micron, we find that adding a second spatial template to the ISM model can greatly improve the accuracy of the model at low latitudes. The crucial product of this analysis is a set of all-sky IR maps from which the Galactic (and IPD) emission has been removed. We discuss systematic uncertainties and potential errors in the foreground subtraction process that may have an impact on studies seeking to detect the CIB in the residual maps.
Mapping the CMB I: the first flight of the QMAP experiment  [PDF]
Mark Devlin,Angelica de Oliveira-Costa,Tom Herbig,Amber Miller,Barth Netterfield,Lyman Page,Max Tegmark
Physics , 1998, DOI: 10.1086/311769
Abstract: We report on the first flight of the balloon-borne QMAP experiment. The experiment is designed to make a map of the cosmic microwave background anisotropy on angular scales from 0.7 to several degrees. Using the map we determine the angular power spectrum of the anisotropy in multipole bands from l~40 to l~140. The results are consistent with the Saskatoon (SK) measurements. The frequency spectral index (measured at low l) is consistent with that of CMB and inconsistent with either Galactic synchrotron or free-free emission. The instrument, measurement, analysis of the angular power spectrum, and possible systematic errors are discussed.
SiO emission from the Galactic Center Molecular Clouds  [PDF]
J. Martin-Pintado,P. de Vicente,A. Fuente,P. Planesas
Physics , 1997, DOI: 10.1086/310691
Abstract: We have mapped the J=1-0 line of SiO in a 1 degree x 12 arcmin. (lxb) region around the Galactic center (GC) with an angular resolution of 2 arcmin. (approx. 4 pc). In contrast to the spatial distribution of other high dipole moment molecules like CS, whose emission is nearly uniform, the SiO emission is very fragmented and it is only associated with some molecular clouds. In particular, it is remarkable that the SiO emission closely follows the non-thermal radio arc in the GC. The SiO clouds are more extended than the beam with typical sizes between 4 and 20 pc. High angular resolution (26 arcsec.) mapping in the J=1-0 line of SiO toward the molecular clouds in Sgr B2 and Sgr A shows that the SiO emission is relatively smooth with structures of typically 2 pc. From the line intensities of the J=1-0, J=3-2 and J=5-4 transitions of SiO we derive H2 densities for these clouds of a few 1e4 cm-3. The SiO fractional abundances are approx. 1e-9 for the SiO clouds and 1e-10 for the other molecular clouds in the GC. The characteristics (size and H2 densities) of the SiO emission in the GC are completely different from those observed in the Galactic disk, where the SiO emission arises from much smaller regions with larger H2 densities. We briefly discuss the implications of the SiO emission in the molecular clouds of the GC. We conclude that the particular chemistry in these clouds is probably related to large scale fast shocks occurring in the Galactic center region.
The Arizona Radio Observatory CO Mapping Survey of Galactic Molecular Clouds: III. The Serpens Cloud in CO J=2-1 and 13CO J=2-1 Emission  [PDF]
K. J. Burleigh,J. H. Bieging,A. Chromey,C. Kulesa,W. L. Peters
Physics , 2013, DOI: 10.1088/0067-0049/209/2/39
Abstract: We mapped 12CO and 13CO J = 2-1 emission over 1.04 square deg of the Serpens molecular cloud with 38 arcsec spatial and 0.3 km/s spectral resolution using the Arizona Radio Observatory Heinrich Hertz Submillimeter telescope. Our maps resolve kinematic properties for the entire Serpens cloud. We also compare our velocity moment maps with known positions of Young Stellar Objects (YSOs) and 1.1 mm continuum emission. We find that 12CO is self-absorbed and 13CO is optically thick in the Serpens core. Outside of the Serpens core, gas appears in filamentary structures having LSR velocities which are blue-shifted by up to 2 km/s relative to the 8 km/s systemic velocity of the Serpens cloud. We show that the known Class I, Flat, and Class II YSOs in the Serpens core most likely formed at the same spatial location and have since drifted apart. The spatial and velocity structure of the 12CO line ratios implies that a detailed 3-dimensional radiative transfer model of the cloud will be necessary for full interpretation of our spectral data. The starless cores region of the cloud is likely to be the next site of star formation in Serpens.
Galactic Free-free Emission and H$α$  [PDF]
J. G. Bartlett,P. Amram
Physics , 1998,
Abstract: We review present understanding of Galactic free-free emission and its possible importance to CMB fluctuation measurements. Current results, from both ``direct'' observations in the microwave band and from H$\alpha$ studies, suggest that this foreground does not represent a serious obstacle to mapping the CMB; however, this is based on limited information and we emphasize the need for more exhaustive studies. We also present some preliminary results based on our recent H$\alpha$ observations near the South Pole CMB data sets. The fluctuation amplitude seen in H$\alpha$ indicates that the detected CMB fluctuations are not significantly contaminated by free-free emission, at least if the diffuse gas is at a temperature of $T\sim 10^4$ K.
High latitude Galactic dust emission in the BOOMERanG maps  [PDF]
S. Masi,P. A. R. Ade,J. J Bock,A. Boscaleri,B. P. Crill,P. de Bernardis,M. Giacometti,E. Hivon,V. V. Hristov,A. E. Lange,P. D. Mauskopf,T. Montroy,C. B. Netterfield,E. Pascale,F. Piacentini,S. Prunet,J. Ruhl
Physics , 2001, DOI: 10.1086/320679
Abstract: We present mm-wave observations obtained by the BOOMERanG experiment of Galactic emission at intermediate and high (b < -20 deg) Galactic latitudes. We find that this emission is well correlated with extrapolation of the IRAS-DIRBE maps, and is spectrally consistent with thermal emission from interstellar dust (ISD). The ISD brightness in the 410 GHz map has an angular power spectrum c_l = A l^{-beta} with 2 < beta < 3. At 150 GHz and at multipoles ell \sim 200 the angular power spectrum of the IRAS-correlated dust signal is estimated to be l(l+1)c_l/2 pi = (3.7 \pm 2.9) uK^2. This is negligible with respect to the CMB signal measured by the same experiment l(l+1)c_l/2 pi = (4700 \pm 540) uK^2. For the uncorrelated dust signal we set an upper limit to the contribution to the CMB power at 150GHz and l \sim 200 of l(l+1)c_l/2 pi < 3 uK^2 at 95% C.L. .
Galactic contamination in the QMAP experiment  [PDF]
Angelica de Oliveira-Costa,Max Tegmark,Mark J. Devlin,L. M. Haffner,Tom Herbig,Amber D. Miller,Lyman A. Page,Ron J. Reynolds,S. L. Tufte
Physics , 2000, DOI: 10.1086/312909
Abstract: We quantify the level of foreground contamination in the QMAP Cosmic Microwave Background (CMB) data with two objectives: (a) measuring the level to which the QMAP power spectrum measurements need to be corrected for foregrounds and (b) using this data set to further refine current foreground models. We cross-correlate the QMAP data with a variety of foreground templates. The 30 GHz Ka-band data is found to be significantly correlated with the Haslam 408 MHz and Reich and Reich 1420 MHz synchrotron maps, but not with the Diffuse Infrared Background Experiment (DIRBE) 240, 140 and 100 micron maps or the Wisconsin H-Alpha Mapper (WHAM) survey. The 40 GHz Q-band has no significant template correlations. We discuss the constraints that this places on synchrotron, free-free and dust emission. We also reanalyze the foreground-cleaned Ka-band data and find that the two band power measurements are lowered by 2.3% and 1.3%, respectively.
Microwave Emission at High Galactic Latitudes  [PDF]
A. Kogut,G. Hinshaw,A. J. Banday,C. L. Bennett,K. Gorski,G. F. Smoot,E. L. Wright
Physics , 1996, DOI: 10.1086/310072
Abstract: We use the COBE Differential Microwave Radiometers (DMR) 4-year sky maps to model Galactic microwave emission at high latitudes (|b| > 20 deg). Cross-correlation of the DMR maps with Galactic template maps detects fluctuations in the high-latitude microwave sky brightness with the angular variation of the DIRBE far-infrared dust maps and a frequency dependence consistent with a superposition of dust and free-free emission. We find no significant correlations between the DMR maps and various synchrotron templates. On the largest angular scales (e.g., quadrupole), Galactic emission is comparable in amplitude to the anisotropy in the cosmic microwave background (CMB). The CMB quadrupole amplitude, after correction for Galactic emission, has amplitude $Q_{rms}$ = 10.7 uK with random uncertainty 3.6 uK and systematic uncertainty 7.1 uK from uncertainty in our knowledge of Galactic microwave emission.
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