Science.gov

Sample records for galactic foreground emission

  1. Five-Year Wilkinson Microwave Anisotropy Probe (WMAP1) Observations: Galactic Foreground Emission

    NASA Technical Reports Server (NTRS)

    Gold, B.; Bennett, C.L.; Larson, D.; Hill, R.S.; Odegard, N.; Weiland, J.L.; Hinshaw, G.; Kogut, A.; Wollack, E.; Page, L.; Dunkley, J.; Jarosik, N.; Spergel, N.; Halpern, M.; Komatsu, E.; Meyer, S.S.; Nolta, M.R.; Wright, E.L.

    2008-01-01

    We present a new estimate of foreground emission in the WMAP data, using a Markov chain Monte Carlo (MCMC) method. The new technique delivers maps of each foreground component for a variety of foreground models, error estimates of the uncertainty of each foreground component, and provides an overall goodness-of-fit measurement. The resulting foreground maps are in broad agreement with those from previous techniques used both within the collaboration and by other authors. We find that for WMAP data, a simple model with power-law synchrotron, free-free, and thermal dust components fits 90% of the sky with a reduced X(sup 2) (sub v) of 1.14. However, the model does not work well inside the Galactic plane. The addition of either synchrotron steepening or a modified spinning dust model improves the fit. This component may account for up to 14% of the total flux at Ka-band (33 GHz). We find no evidence for foreground contamination of the CMB temperature map in the 85% of the sky used for cosmological analysis.

  2. PIPER and Polarized Galactic Foregrounds

    NASA Technical Reports Server (NTRS)

    Chuss, David

    2009-01-01

    In addition to probing inflationary cosmology, PIPER will measure the polarized dust emission from the Galaxy. PIPER will be capable of full (I,0,U,V) measurement over four frequency bands ' These measurements will provide insight into the physics of dust grains and a probe of the Galactic magnetic field on large and intermediate scales.

  3. Statistical Diagnostics to Identify Galactic Foregrounds in B -Mode Maps

    NASA Astrophysics Data System (ADS)

    Kamionkowski, Marc; Kovetz, Ely D.

    2014-11-01

    Recent developments in the search for inflationary gravitational waves in the cosmic microwave background polarization motivate the search for new diagnostics to distinguish the Galactic foreground contribution to B modes from the cosmic signal. We show that B modes from these foregrounds should exhibit a local hexadecapolar departure in power from statistical isotropy (SI). We present a simple algorithm to search for a uniform SI violation of this sort, as may arise in a sufficiently small patch of sky. We then show how to search for these effects if the orientation of the SI violation varies across the survey region, as is more likely to occur in surveys with more sky coverage. If detected, these departures from Gaussianity would indicate some level of Galactic foreground contamination in the B -mode maps. Given uncertainties about foreground properties, though, caution should be exercised in attributing a null detection to an absence of foregrounds.

  4. COSMOG: Cosmology Oriented Sub-mm Modeling of Galactic Foregrounds

    NASA Technical Reports Server (NTRS)

    Kashlinsky, A.; Leisawitz, D.

    2004-01-01

    With upcoming missions in mid- and far-Infrared there is a need for software packages to reliably simulate the planned observations. This would help in both planning the observation and scanning strategy and in developing the concepts of the far-off missions. As this workshop demonstrated, many of the new missions are to be in the far-IR range of the electromagnetic spectrum and at the same time will map the sky with a sub-arcsec angular resolution. We present here a computer package for simulating foreground maps for the planned sub-mm and far-IR missions. such as SPECS. The package allows to study confusion limits and simulate cosmological observations for specified sky location interactively and in real time. Most of the emission at wavelengths long-ward of approximately 50 microns is dominated by Galactic cirrus and Zodiacal dust emission. Stellar emission at these wavelengths is weak and is for now neglected. Cosmological sources (distant and not-so-distant) galaxies for specified cosmologies will be added. Briefly, the steps that the algorithm goes through is described.

  5. First Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Foreground Emission

    NASA Technical Reports Server (NTRS)

    Bennett, C. L.; Hill, R. S.; Hinshaw, G.; Nolta, M. R.; Odegard, N.; Page, L.; Spergel, D. N.; Weiland, J. L.; Wright, E. L.; Halpern, M.

    2003-01-01

    The WMAP mission has mapped the full sky to determine the geometry, content, and evolution of the universe. Full sky maps are made in five microwave frequency bands to separate the temperature anisotropy of the cosmic microwave background (CMB) from foreground emission, including diffuse Galactic emission and Galactic and extragalactic point sources. We define masks that excise regions of high foreground emission, so CMB analyses can became out with minimal foreground contamination. We also present maps and spectra of the individual emission components, leading to an improved understanding of Galactic astrophysical processes. The effectiveness of template fits to remove foreground emission from the WMAP data is also examined. These efforts result in a CMB map with minimal contamination and a demonstration that the WMAP CMB power spectrum is insensitive to residual foreground emission. We use a Maximum Entropy Method to construct a model of the Galactic emission components. The observed total Galactic emission matches the model to less than 1% and the individual model components are accurate to a few percent. We find that the Milky Way resembles other normal spiral galaxies between 408 MHz and 23 GHz, with a synchrotron spectral index that is flattest (beta(sub s) approx. -2.5) near star-forming regions, especially in the plane, and steepest (beta(sub s) approx. -3) in the halo. This is consistent with a picture of relativistic cosmic ray electron generation in star-forming regions and diffusion and convection within the plane. The significant synchrotron index steepening out of the plane suggests a diffusion process in which the halo electrons are trapped in the Galactic potential long enough to suffer synchrotron and inverse Compton energy losses and hence a spectral steepening. The synchrotron index is steeper in the WMAP bands than in lower frequency radio surveys, with a spectral break near 20 GHz to beta(sub s) less than -3. The modeled thermal dust spectral

  6. Statistical diagnostics to identify galactic foregrounds in B-mode maps.

    PubMed

    Kamionkowski, Marc; Kovetz, Ely D

    2014-11-01

    Recent developments in the search for inflationary gravitational waves in the cosmic microwave background polarization motivate the search for new diagnostics to distinguish the Galactic foreground contribution to B modes from the cosmic signal. We show that B modes from these foregrounds should exhibit a local hexadecapolar departure in power from statistical isotropy (SI). We present a simple algorithm to search for a uniform SI violation of this sort, as may arise in a sufficiently small patch of sky. We then show how to search for these effects if the orientation of the SI violation varies across the survey region, as is more likely to occur in surveys with more sky coverage. If detected, these departures from Gaussianity would indicate some level of Galactic foreground contamination in the B-mode maps. Given uncertainties about foreground properties, though, caution should be exercised in attributing a null detection to an absence of foregrounds. PMID:25415897

  7. The Parkes Galactic Meridian Survey: observations and CMB polarization foreground analysis

    NASA Astrophysics Data System (ADS)

    Carretti, E.; Haverkorn, M.; McConnell, D.; Bernardi, G.; McClure-Griffiths, N. M.; Cortiglioni, S.; Poppi, S.

    2010-07-01

    We present observations and cosmic microwave background (CMB) foreground analysis of the Parkes Galactic Meridian Survey, an investigation of the Galactic latitude behaviour of the polarized synchrotron emission at 2.3GHz with the Parkes Radio Telescope. The survey consists of a 5° wide strip along the Galactic meridian l = 254° extending from the Galactic plane to the South Galactic pole. We identify three zones distinguished by polarized emission properties: the disc, the halo and a transition region connecting them. The halo section lies at latitudes |b| > 40° and has weak and smooth polarized emission mostly at large scale with steep angular power spectra of median slope βmed ~ -2.6. The disc region covers the latitudes |b| < 20° and has a brighter, more complex emission dominated by the small scales with flatter spectra of median slope βmed = -1.8. The transition region has steep spectra as in the halo, but the emission increases towards the Galactic plane from halo to disc levels. The change of slope and emission structure at b ~ -20° is sudden, indicating a sharp disc-halo transition. The whole halo section is just one environment extended over 50° with very low emission which, once scaled to 70GHz, is equivalent to the CMB B-mode emission for a tensor-to-scalar perturbation power ratio rhalo = (3.3 +/- 0.4) × 10-3. Applying a conservative cleaning procedure, we estimate an r detection limit of δr ~ 2 × 10-3 at 70GHz (3σ confidence limit) and, assuming a dust polarization fraction of <12per cent, δr ~ 1 × 10-2 at 150GHz. The 150-GHz limit matches the goals of planned sub-orbital experiments, which can therefore be conducted at this high frequency. The 70-GHz limit is close to the goal of proposed next-generation space missions, which thus might not strictly require space-based platforms.

  8. Galactic Foreground Contribution to the BEAST Cosmic Microwave Background Anisotropy Maps

    NASA Astrophysics Data System (ADS)

    Mejía, Jorge; Bersanelli, Marco; Burigana, Carlo; Childers, Jeff; Figueiredo, Newton; Kangas, Miikka; Lubin, Philip; Maino, Davide; Mandolesi, Nazzareno; Marvil, Josh; Meinhold, Peter; O'Dwyer, Ian; O'Neill, Hugh; Platania, Paola; Seiffert, Michael; Stebor, Nathan; Tello, Camilo; Villela, Thyrso; Wandelt, Benjamin; Wuensche, Carlos Alexandre

    2005-05-01

    We report limits on the Galactic foreground emission contribution to the Background Emission Anisotropy Scanning Telescope (BEAST) Ka- and Q-band CMB anisotropy maps. We estimate the contribution from the cross-correlations between these maps and the foreground emission templates of an Hα map, a destriped version of the Haslam et al. 408 MHz map, and a combined 100 μm IRAS DIRBE map. Our analysis samples the BEAST ~10° declination band into 24 one-hour (R.A.) wide sectors with ~7900 pixels each, where we calculate (1) the linear correlation coefficient between the anisotropy maps and the templates; (2) the coupling constants between the specific intensity units of the templates and the antenna temperature at the BEAST frequencies; and (3) the individual foreground contributions to the BEAST anisotropy maps. The peak sector contributions of the contaminants in the Ka-band are of 56.5% free-free with a coupling constant of 8.3+/-0.4 μK R-1, and 67.4% dust with 45.0+/-2.0 μK MJy-1 sr-1. In the Q band the corresponding values are of 64.4% free-free with 4.1+/-0.2 μK R-1 and 67.5% dust with 24.0+/-1.0 μK MJy-1 sr-1. Using a lower limit of 10% in the relative uncertainty of the coupling constants, we can constrain the sector contributions of each contaminant in both maps to <20% in 21 (free-free), 19 (dust), and 22 (synchrotron) sectors. At this level, all these sectors are found outside of the |b|=14.6d region. By performing the same correlation analysis as a function of Galactic scale height, we conclude that the region within b=+/-17.5d should be removed from the BEAST maps for CMB studies in order to keep individual Galactic contributions below ~1% of the map's rms.

  9. Galactic Diffuse Emissions

    SciTech Connect

    Digel, Seth W.; /SLAC

    2007-10-25

    Interactions of cosmic rays with interstellar nucleons and photons make the Milky Way a bright, diffuse source of high-energy {gamma}-rays. Observationally, the results from EGRET, COMPTEL, and OSSE have now been extended to higher energies by ground-based experiments, with detections of diffuse emission in the Galactic center reported by H.E.S.S. in the range above 100 GeV and of diffuse emission in Cygnus by MILAGRO in the TeV range. In the range above 100 keV, INTEGRAL SPI has found that diffuse emission remains after point sources are accounted for. I will summarize current knowledge of diffuse {gamma}-ray emission from the Milky Way and review some open issues related to the diffuse emission -- some old, like the distribution of cosmic-ray sources and the origin of the 'excess' of GeV emission observed by EGRET, and some recently recognized, like the amount and distribution of molecular hydrogen not traced by CO emission -- and anticipate some of the advances that will be possible with the Large Area Telescope on GLAST. We plan to develop an accurate physical model for the diffuse emission, which will be useful for detecting and accurately characterizing emission from Galactic point sources as well as any Galactic diffuse emission from exotic processes, and for studying the unresolved extragalactic emission.

  10. BICEP2/Keck - Planck joint analysis and prospects for Galactic foreground removal from CMB observations

    NASA Astrophysics Data System (ADS)

    Crill, Brendan

    2015-08-01

    The joint analysis of 150 GHz polarized maps from BICEP2 and Keck Array at 150 GHz with Planck data at 353 GHzallowed the removal of Galactic dust contamination from the measurement of lensed B-modes in the deep (57 nK deg)BICEP2/Keck maps as well as setting an upper limit on the primordial gravitational wave background from inflation. We present this analysis, describe prospects for polarized foreground cleaning of future suborbitalmeasurements of CMB, and additionally describe Planck's measurements of the spatial correlation of polarizedemission from synchrotron and dust at high galactic latitude, which complicates the removal of Galactic foregrounds at the foregroundminimum of 70-100 GHz.

  11. Galactic Diffuse Polarized Emission

    NASA Astrophysics Data System (ADS)

    Carretti, Ettore

    2011-12-01

    Diffuse polarized emission by synchrotron is a key tool to investigate magnetic fields in the Milky Way, particularly the ordered component of the large scale structure. Key observables are the synchrotron emission itself and the RM is by Faraday rotation. In this paper the main properties of the radio polarized diffuse emission and its use to investigate magnetic fields will be reviewed along with our current understanding of the galactic magnetic field and the data sets available. We will then focus on the future perspective discussing RM-synthesis - the new powerful instrument devised to unlock the information encoded in such an emission - and the surveys currently in progress like S-PASS and GMIMS.

  12. Observational and theoretical advances in cosmological foreground emission

    NASA Astrophysics Data System (ADS)

    Stevenson, Matthew A.

    Observational and theoretical work towards the separation of foreground emission from the cosmic microwave background is described. The bulk of this work is in the design, construction, and commissioning of the C-Band All-Sky Survey (C-BASS), an experiment to produce a template of the Milky Way Galaxy's polarized synchrotron emission. Theoretical work is the derivation of an analytical approximation to the emission spectrum of spinning dust grains. The performance of the C-BASS experiment is demonstrated through a preliminary, deep survey of the North Celestial Pole region. A comparison to multiwavelength data is performed, and the thermal and systematic noise properties of the experiment are explored. The systematic noise has been minimized through careful data processing algorithms, implemented both in the experiment's Field Programmable Gate Array (FPGA) based digital backend and in the data analysis pipeline. Detailed descriptions of these algorithms are presented. The analytical function of spinning dust emission is derived through the application of careful approximations, with each step tested against numerical calculations. This work is intended for use in the parameterized separation of cosmological foreground components and as a framework for interpreting and comparing the variety of anomalous microwave emission observations.

  13. An illustration of the foreground emission subtraction process resulting in the DIRBE detection of t

    NASA Technical Reports Server (NTRS)

    2002-01-01

    An illustration of the foreground emission subtraction process resulting in the DIRBE detection of the Cosmic Infrared Background at 240 Aum. The map at the top is a false-color image showing the observed infrared sky brightness at wavelengths of 60 (blue), 100 (green) and 240 Aum (red). The bright white-yellow horizontal band across the middle of the image corresponds to emission from interstellar dust in the plane of our Milky Way Galaxy (the center of the Galaxy lies at the center of the map). The red regions above and below this bright band are 'infrared cirrus' clouds, wispy clouds of relatively cool Galactic dust. The blue S-shaped figure follows the ecliptic plane and represents emission from interplanetary dust in the solar system. The map in the middle is a 60-100-240 Aum false-color image depicting the sky after the foreground glow of the interplanetary dust has been modeled and subtracted; this image is dominated by emission from interstellar dust in the Milky Way. After the infrared light from our solar system and Galaxy has been removed, what remains is a uniform Cosmic Infrared Background. This is illustrated in the bottom image, which shows just the residual 240 Aum brightness. The line across the center is an artifact from removal of the Galactic light. The DIRBE team reports detection of this cosmic background light also at 140 Aum, and has set limits to its brightness at eight other infrared wavelengths from 1.25 to 100 Aum (see Slide 22). Credit: STScI OPO - PRC98-01; M. Hauser and NASA.

  14. VizieR Online Data Catalog: Foreground Galactic stars properties (Kordopatis+, 2013)

    NASA Astrophysics Data System (ADS)

    Kordopatis, G.; Hill, V.; Irwin, M.; Gilmore, G.; Wyse, R. F. G.; Tolstoy, E.; de Laverny, P.; Recio-Blanco, A.; Battaglia, G.; Starkenburg, E.

    2013-05-01

    These tables contain all the parameters that have been computed, based on the LR8 spectra of targets selected as being foreground Galactic members. The atmospheric parameters were computed using the pipeline presented in Kordopatis et al. (2011A&A...535A.106K). The line-of-sight distances and the projected atmospheric parameters were computed by projecting the pipeline atmospheric parameters on the Yonsei-Yale isochrones as in Kordopatis et al. (2011A&A...535A.106K). The calibrated metallicities are obtained by applying the corrections established in Kordopatis et al. (2013b, in prep.) for the 4th data release of the RAVE survey. The radial velocities, the photometric values and the positions are taken from Battaglia et al. (2008, Cat. J/MNRAS/383/183) and Koch et al. (2006, Cat. J/AJ/131/895). (2 data files).

  15. Diffuse synchrotron emission from galactic cosmic ray electrons

    NASA Astrophysics Data System (ADS)

    Di Bernardo, G.; Grasso, D.; Evoli, C.; Gaggero, D.

    2015-09-01

    Synchrotron diffuse radiation (SDR) emission is one of the major Galactic components, in the 100 MHz up to 100 GHz frequency range. Its spectrum and sky map provide valuable measure of the galactic cosmic ray electrons (GCRE) in the relevant energy range, as well as of the strength and structure of the Galactic magnetic fields (GMF), both regular and random ones. This emission is an astrophysical sky foreground for the study of the Cosmic Microwave Background (CMB), and the extragalactic microwave measurements, and it needs to be modelled as better as possible. In this regard, in order to get an accurate description of the SDR in the Galaxy, we use - for the first time in this context - 3-dimensional GCRE models obtained by running the DRAGON code. This allows us to account for a realistic spiral arm pattern of the source distribution, demanded to get a self-consistent treatment of all relevant energy losses influencing the final synchrotron spectrum.

  16. The 21-cm emission from the reionization epoch: extended and point source foregrounds

    NASA Astrophysics Data System (ADS)

    Di Matteo, Tiziana; Ciardi, Benedetta; Miniati, Francesco

    2004-12-01

    Fluctuations in the redshifted 21-cm emission from neutral hydrogen probe the epoch of reionization. We examine the observability of this signal and the impact of extragalactic foreground radio sources (both extended and point-like). We use cosmological simulations to predict the angular correlation functions of intensity fluctuations due to unresolved radio galaxies, cluster radio haloes and relics and free-free emission from the interstellar and intergalactic medium at the frequencies and angular scales relevant for the proposed 21-cm tomography. In accord with previous findings, the brightness temperature fluctuations due to foreground sources are much larger than those from the primary 21-cm signal at all scales. In particular, diffuse cluster radio emission, which has been previously neglected, provides the most significant foreground contamination. However, we show that the contribution to the angular fluctuations at scales θ>~ 1 arcmin is dominated by the spatial clustering of bright foreground sources. This excess can be removed if sources above flux levels S>~ 0.1 mJy (out to redshifts of z~ 1 and z~ 2 for diffuse and point sources, respectively) are detected and removed. Hence, efficient source removal may be sufficient to allow the detection of angular fluctuations in the 21-cm emission free of extragalactic foregrounds at θ>~ 1 arcmin. In addition, the removal of sources above S= 0.1 mJy also reduces the foreground fluctuations to roughly the same level as the 21-cm signal at scales θ<~ 1 arcmin. This should allow the substraction of the foreground components in frequency space, making it possible to observe in detail the topology and history of reionization.

  17. ARCADE 2 Observations of Galactic Radio Emission

    NASA Technical Reports Server (NTRS)

    Kogut, A.; Fixsen, D. J.; Levin, S. M.; Limon, M.; Lubin, P. M.; Mirel, P.; Seiffert, M.; Singal, J.; Villela, T.; Wollack, E.; Wuensche, C. A.

    2010-01-01

    We use absolutely calibrated data from the Absolute Radiometer for Cosmology, Astrophysics, and Diffuse Emission (ARCADE 2) flight in July 2006 to model Galactic emission at frequencies 3, 8, and 10 GHz. The spatial structure in the data is consistent with a superposition of free-free and synchrotron emission. Emission with spatial morphology traced by the Haslam 408 MHz survey has spectral index beta_synch = -2.5 +/- 0.1, with free-free emission contributing 0.10 +/- 0.01 of the total Galactic plane emission in the lowest ARCADE 2 band at 3.15 GHz. We estimate the total Galactic emission toward the polar caps using either a simple plane-parallel model with csc|b| dependence or a model of high-latitude radio emission traced by the COBE/FIRAS map of CII emission. Both methods are consistent with a single power-law over the frequency range 22 MHz to 10 GHz, with total Galactic emission towards the north polar cap T_Gal = 0.498 +/- 0.028 K and spectral index beta = -2.55 +/- 0.03 at reference frequency 0.31 GHz. The well calibrated ARCADE 2 maps provide a new test for spinning dust emission, based on the integrated intensity of emission from the Galactic plane instead of cross-correlations with the thermal dust spatial morphology. The Galactic plane intensity measured by ARCADE 2 is fainter than predicted by models without spinning dust, and is consistent with spinning dust contributing 0.4 +/- 0.1 of the Galactic plane emission at 23 GHz.

  18. Skewness and kurtosis as indicators of non-Gaussianity in galactic foreground maps

    NASA Astrophysics Data System (ADS)

    Ben-David, Assaf; von Hausegger, Sebastian; Jackson, Andrew D.

    2015-11-01

    Observational cosmology is entering an era in which high precision will be required in both measurement and data analysis. Accuracy, however, can only be achieved with a thorough understanding of potential sources of contamination from foreground effects. Our primary focus will be on non-Gaussian effects in foregrounds. This issue will be crucial for coming experiments to determine B-mode polarization. We propose a novel method for investigating a data set in terms of skewness and kurtosis in locally defined regions that collectively cover the entire sky. The method is demonstrated on two sky maps: (i) the SMICA map of Cosmic Microwave Background fluctuations provided by the Planck Collaboration and (ii) a version of the Haslam map at 408 MHz that describes synchrotron radiation. We find that skewness and kurtosis can be evaluated in combination to reveal local physical information. In the present case, we demonstrate that the statistical properties of both maps in small local regions are predominantly Gaussian. This result was expected for the SMICA map. It is surprising that it also applies for the Haslam map given its evident large scale non-Gaussianity. The approach described here has a generality and flexibility that should make it useful in a variety of astrophysical and cosmological contexts.

  19. The Diffuse Galactic Gamma-Ray Emission Model for GLAST LAT

    SciTech Connect

    Porter, T.A.; Digel, S.W.; Grenier, I.A.; Moskalenko, I.V.; Strong, A.W.; /Garching, Max Planck Inst., MPE

    2007-06-13

    Diffuse emission from the Milky Way dominates the gamma-ray sky. About 80% of the high-energy luminosity of the Milky Way comes from processes in the interstellar medium. The Galactic diffuse emission traces interactions of energetic particles, primarily protons and electrons, with the interstellar gas and radiation field, thus delivering information about cosmic-ray spectra and interstellar mass in distant locations. Additionally, the Galactic diffuse emission is the celestial foreground for the study of gamma-ray point sources and the extragalactic diffuse gamma-ray emission. We will report on the latest developments in the modeling of the Galactic diffuse emission, which will be used for the Gamma Ray Large Area Space Telescope (GLAST) investigations.

  20. Characterization of foreground emission on degree angular scales for CMB B-mode observations . Thermal dust and synchrotron signal from Planck and WMAP data

    NASA Astrophysics Data System (ADS)

    Krachmalnicoff, N.; Baccigalupi, C.; Aumont, J.; Bersanelli, M.; Mennella, A.

    2016-04-01

    We quantify the contamination from polarized diffuse Galactic synchrotron and thermal dust emissions to the B modes of the cosmic microwave background (CMB) anisotropies on the degree angular scale, using data from the Planck and Wilkinson Microwave Anisotropy Probe (WMAP) satellites. We compute power spectra of foreground polarized emissions in 352 circular sky patches located at Galactic latitude | b | > 20°, each of which covers about 1.5% of the sky. We make use of the spectral properties derived from Planck and WMAP data to extrapolate, in frequency, the amplitude of synchrotron and thermal dust B-mode spectra in the multipole bin centered at ℓ ≃ 80. In this way we estimate the amplitude and frequency of the foreground minimum for each analyzed region. We detect both dust and synchrotron signal on degree angular scales and at a 3σ confidence level in 28 regions. Here the minimum of the foreground emission is found at frequencies between 60 and 100 GHz with an amplitude expressed in terms of the equivalent tensor-to-scalar ratio, rFG,min, between ~0.06 and ~1. Some of these regions are located at high Galactic latitudes in areas close to the ones that are being observed by suborbital experiments. In all the other sky patches where synchrotron or dust B modes are not detectable with the required confidence, we put upper limits on the minimum foreground contamination and find values of rFG,min between ~0.05 and ~1.5 in the frequency range 60-90 GHz. Our results indicate that, with the current sensitivity at low frequency, it is not possible to exclude the presence of synchrotron contamination to CMB cosmological B modes at the level requested to measure a gravitational waves signal with r ≃ 0.01 at frequency ≲100 GHz anywhere. Therefore, more accurate data are essential in order to better characterize the synchrotron polarized component and, eventually, to remove its contamination to CMB signal through foreground cleaning.

  1. Galactic dust polarized emission at high latitudes and CMB polarization

    NASA Astrophysics Data System (ADS)

    Prunet, S.; Sethi, S. K.; Bouchet, F. R.; Miville-Deschenes, M.-A.

    1998-11-01

    With recent instrumental advances, it might become possible to measure the polarization of the Cosmic Microwave Background (CMB), e.g. by future space missions like MAP and Planck Surveyor. In this paper, we estimate the dust polarized emission in our galaxy which is the major foreground to cope with for measuring the CMB polarization in the Wien part of CMB spectrum. We model the dust polarized emission in the galaxy using the three-dimensional HI maps of the Leiden/Dwingeloo survey at high galactic latitudes. We use the fact that the dust emission, for a wide range of wavelengths, has a tight correlation with the HI emission maps of this survey (Boulanger et al. 1996). Assuming the dust grains to be oblate with axis ratio =~ 2/3, which recent studies support, we determine the intrinsic dust polarized emissivity. The distribution of magnetic field with respect to the dust grain distribution is quite uncertain, we thus consider three extreme cases: (1) The magnetic field is aligned with the major axis of the dust structure, (2) the magnetic field has a random direction in the plane perpendicular to the direction of major axis of the dust structure, and (3) the magnetic field is unidirectional throughout. We further assume, as recent observations and theoretical analyses support, that the dust grains align with the magnetic field independently of its strength. The polarization reduction factor from misalignment of the direction of polarization from the plane of the sky and the differential polarization along a line of sight is calculated using these maps, to construct two-dimensional maps of dust polarized emission. We calculate the angular power spectrum of dust polarized emission from these maps and cast it in variables which allow a direct comparison with the polarized component of the CMB. Our results, at frequencies =~ 100 GHz, suggest that: (a) This foreground contamination is smaller than the scalar-induced polarization of the CMB at l ga 200 while the tensor

  2. Nonthermal galactic emission below 10 MHz

    NASA Technical Reports Server (NTRS)

    Novaco, J. C.; Brown, L. W.

    1977-01-01

    The Radio Astronomy Explorer-2 (RAE-2) satellite has provided new measurements of the nonthermal galactic radio emission at frequencies below 10 MHz. Measurements of the emission spectra are presented for the center, anticenter, north polar, and south polar directions at 22 frequencies between 0.25 and 9.18 MHz. Survey maps of the spatial distribution of the observed low frequency galactic emission at 1.31, 2.20, 3.93, 4.70, 6.55, and 9.18 MHz are presented. The observations were obtained with the 229-meter traveling-wave V-antenna on this lunar orbiting spacecraft. The improved frequency coverage offers additional insights into structure of the local galactic neighborhood.

  3. Toward an understanding of foreground emission in the BICEP2 region

    SciTech Connect

    Flauger, Raphael; Hill, J. Colin; Spergel, David N. E-mail: jch@astro.princeton.edu

    2014-08-01

    BICEP2 has reported the detection of a degree-scale B-mode polarization pattern in the Cosmic Microwave Background (CMB) and has interpreted the measurement as evidence for primordial gravitational waves. Motivated by the profound importance of the discovery of gravitational waves from the early Universe, we examine to what extent a combination of Galactic foregrounds and lensed E-modes could be responsible for the signal. We reanalyze the BICEP2 results and show that the 100 ×150 GHz and 150 ×150 GHz data are consistent with a cosmology with r=0.2 and negligible foregrounds, but also with a cosmology with r=0 and a significant dust polarization signal. We give independent estimates of the dust polarization signal in the BICEP2 region using a number of different approaches: (1) data-driven models based on Planck 353 GHz intensity, polarization fractions inferred from the same Planck data used by the BICEP2 team but corrected for CMB and CIB contributions, and polarization angles from starlight polarization data or the Planck sky model; (2) the same set of pre-Planck models used by the BICEP2 team but taking into account the higher polarization fractions observed in the CMB- and CIB-corrected map; (3) a measurement of neutral hydrogen gas column density N{sub HI} in the BICEP2 region combined with an extrapolation of a relation between HI column density and dust polarization derived by Planck; and (4) a dust polarization map based on digitized Planck data, which we only use as a final cross-check. While these approaches are consistent with each other, the expected amplitude of the dust polarization power spectrum remains uncertain by about a factor of three. The lower end of the prediction leaves room for a primordial contribution, but at the higher end the dust in combination with the standard CMB lensing signal could account for the BICEP2 observations, without requiring the existence of primordial gravitational waves. By measuring the cross-correlations between

  4. XMM-NEWTON MEASUREMENT OF THE GALACTIC HALO X-RAY EMISSION USING A COMPACT SHADOWING CLOUD

    SciTech Connect

    Henley, David B.; Shelton, Robin L.; Cumbee, Renata S.; Stancil, Phillip C.

    2015-02-01

    Observations of interstellar clouds that cast shadows in the soft X-ray background can be used to separate the background Galactic halo emission from the local emission due to solar wind charge exchange (SWCX) and/or the Local Bubble (LB). We present an XMM-Newton observation of a shadowing cloud, G225.60–66.40, that is sufficiently compact that the on- and off-shadow spectra can be extracted from a single field of view (unlike previous shadowing observations of the halo with CCD-resolution spectrometers, which consisted of separate on- and off-shadow pointings). We analyzed the spectra using a variety of foreground models: one representing LB emission, and two representing SWCX emission. We found that the resulting halo model parameters (temperature T {sub h} ≈ 2 × 10{sup 6} K, emission measure E{sub h}≈4×10{sup −3} cm{sup −6} pc) were not sensitive to the foreground model used. This is likely due to the relative faintness of the foreground emission in this observation. However, the data do favor the existence of a foreground. The halo parameters derived from this observation are in good agreement with those from previous shadowing observations, and from an XMM-Newton survey of the Galactic halo emission. This supports the conclusion that the latter results are not subject to systematic errors, and can confidently be used to test models of the halo emission.

  5. XMM-Newton Measurement of the Galactic Halo X-Ray Emission using a Compact Shadowing Cloud

    NASA Astrophysics Data System (ADS)

    Henley, David B.; Shelton, Robin L.; Cumbee, Renata S.; Stancil, Phillip C.

    2015-02-01

    Observations of interstellar clouds that cast shadows in the soft X-ray background can be used to separate the background Galactic halo emission from the local emission due to solar wind charge exchange (SWCX) and/or the Local Bubble (LB). We present an XMM-Newton observation of a shadowing cloud, G225.60-66.40, that is sufficiently compact that the on- and off-shadow spectra can be extracted from a single field of view (unlike previous shadowing observations of the halo with CCD-resolution spectrometers, which consisted of separate on- and off-shadow pointings). We analyzed the spectra using a variety of foreground models: one representing LB emission, and two representing SWCX emission. We found that the resulting halo model parameters (temperature T h ≈ 2 × 106 K, emission measure {E}h≈ 4 × 10-3 cm-6 pc) were not sensitive to the foreground model used. This is likely due to the relative faintness of the foreground emission in this observation. However, the data do favor the existence of a foreground. The halo parameters derived from this observation are in good agreement with those from previous shadowing observations, and from an XMM-Newton survey of the Galactic halo emission. This supports the conclusion that the latter results are not subject to systematic errors, and can confidently be used to test models of the halo emission.

  6. FERMI BUBBLES AND BUBBLE-LIKE EMISSION FROM THE GALACTIC PLANE

    SciTech Connect

    De Boer, Wim; Weber, Markus E-mail: markus.weber2@kit.edu

    2014-10-10

    The diffuse gamma-ray sky revealed ''bubbles'' of emission above and below the Galactic plane, symmetric around the center of the Milky Way, with a height of 10 kpc in both directions. At present, there is no convincing explanation for the origin. To understand the role of the Galactic center, one has to study the bubble spectrum inside the disk, a region that has been excluded from previous analyses because of the large foreground. From a novel template fit, which allows a simultaneous determination of the signal and foreground in any direction, we find that bubble-like emission is not only found in the halo, but in the Galactic plane as well, with a width in latitude coinciding with the molecular clouds. The longitude distribution has a width corresponding to the Galactic bar with an additional contribution from the Scutum-Centaurus arm. The energy spectrum of the bubbles coincides with the predicted contribution from CRs trapped in sources (SCRs). Also, the energetics fits well. Hence, we conclude that the bubble-like emission has a hadronic origin that arises from SCRs, and the bubbles in the halo arise from hadronic interactions in advected gas. Evidence for advection is provided by the ROSAT X-rays of hot gas in the bubble region.

  7. Foreground Bias from Parametric Models of Far-IR Dust Emission

    NASA Technical Reports Server (NTRS)

    Kogut, A.; Fixsen, D. J.

    2016-01-01

    We use simple toy models of far-IR dust emission to estimate the accuracy to which the polarization of the cosmic microwave background can be recovered using multi-frequency fits, if the parametric form chosen for the fitted dust model differs from the actual dust emission. Commonly used approximations to the far-IR dust spectrum yield CMB residuals comparable to or larger than the sensitivities expected for the next generation of CMB missions, despite fitting the combined CMB plus foreground emission to precision 0.1 percent or better. The Rayleigh-Jeans approximation to the dust spectrum biases the fitted dust spectral index by (Delta)(Beta)(sub d) = 0.2 and the inflationary B-mode amplitude by (Delta)(r) = 0.03. Fitting the dust to a modified blackbody at a single temperature biases the best-fit CMB by (Delta)(r) greater than 0.003 if the true dust spectrum contains multiple temperature components. A 13-parameter model fitting two temperature components reduces this bias by an order of magnitude if the true dust spectrum is in fact a simple superposition of emission at different temperatures, but fails at the level (Delta)(r) = 0.006 for dust whose spectral index varies with frequency. Restricting the observing frequencies to a narrow region near the foreground minimum reduces these biases for some dust spectra but can increase the bias for others. Data at THz frequencies surrounding the peak of the dust emission can mitigate these biases while providing a direct determination of the dust temperature profile.

  8. Foreground Bias from Parametric Models of Far-IR Dust Emission

    NASA Astrophysics Data System (ADS)

    Kogut, A.; Fixsen, D. J.

    2016-08-01

    We use simple toy models of far-IR dust emission to estimate the accuracy to which the polarization of the cosmic microwave background can be recovered using multi-frequency fits, if the parametric form chosen for the fitted dust model differs from the actual dust emission. Commonly used approximations to the far-IR dust spectrum yield CMB residuals comparable to or larger than the sensitivities expected for the next generation of CMB missions, despite fitting the combined CMB + foreground emission to precision 0.1% or better. The Rayleigh–Jeans approximation to the dust spectrum biases the fitted dust spectral index by {{Δ }}{β }d=0.2 and the inflationary B-mode amplitude by {{Δ }}r=0.03. Fitting the dust to a modified blackbody at a single temperature biases the best-fit CMB by {{Δ }}r\\gt 0.003 if the true dust spectrum contains multiple temperature components. A 13-parameter model fitting two temperature components reduces this bias by an order of magnitude if the true dust spectrum is in fact a simple superposition of emission at different temperatures, but fails at the level {{Δ }}r=0.006 for dust whose spectral index varies with frequency. Restricting the observing frequencies to a narrow region near the foreground minimum reduces these biases for some dust spectra but can increase the bias for others. Data at THz frequencies surrounding the peak of the dust emission can mitigate these biases while providing a direct determination of the dust temperature profile.

  9. Maps of Dust Infrared Emission for Use in Estimation of Reddening and Cosmic Microwave Background Radiation Foregrounds

    NASA Astrophysics Data System (ADS)

    Schlegel, David J.; Finkbeiner, Douglas P.; Davis, Marc

    1998-06-01

    We present a full-sky 100 μm map that is a reprocessed composite of the COBE/DIRBE and IRAS/ISSA maps, with the zodiacal foreground and confirmed point sources removed. Before using the ISSA maps, we remove the remaining artifacts from the IRAS scan pattern. Using the DIRBE 100 and 240 μm data, we have constructed a map of the dust temperature so that the 100 μm map may be converted to a map proportional to dust column density. The dust temperature varies from 17 to 21 K, which is modest but does modify the estimate of the dust column by a factor of 5. The result of these manipulations is a map with DIRBE quality calibration and IRAS resolution. A wealth of filamentary detail is apparent on many different scales at all Galactic latitudes. In high-latitude regions, the dust map correlates well with maps of H I emission, but deviations are coherent in the sky and are especially conspicuous in regions of saturation of H I emission toward denser clouds and of formation of H2 in molecular clouds. In contrast, high-velocity H I clouds are deficient in dust emission, as expected. To generate the full-sky dust maps, we must first remove zodiacal light contamination, as well as a possible cosmic infrared background (CIB). This is done via a regression analysis of the 100 μm DIRBE map against the Leiden-Dwingeloo map of H I emission, with corrections for the zodiacal light via a suitable expansion of the DIRBE 25 μm flux. This procedure removes virtually all traces of the zodiacal foreground. For the 100 μm map no significant CIB is detected. At longer wavelengths, where the zodiacal contamination is weaker, we detect the CIB at surprisingly high flux levels of 32 +/- 13 nW m-2 sr-1 at 140 μm and of 17 +/- 4 nW m-2 sr-1 at 240 μm (95% confidence). This integrated flux ~2 times that extrapolated from optical galaxies in the Hubble Deep Field. The primary use of these maps is likely to be as a new estimator of Galactic extinction. To calibrate our maps, we assume a

  10. A CMB foreground study in WMAP data: Extragalactic point sources and zodiacal light emission

    NASA Astrophysics Data System (ADS)

    Chen, Xi

    The Cosmic Microwave Background (CMB) radiation is the remnant heat from the Big Bang. It serves as a primary tool to understand the global properties, content and evolution of the universe. Since 2001, NASA's Wilkinson Microwave Anisotropy Probe (WMAP) satellite has been napping the full sky anisotropy with unprecedented accuracy, precision and reliability. The CMB angular power spectrum calculated from the WMAP full sky maps not only enables accurate testing of cosmological models, but also places significant constraints on model parameters. The CMB signal in the WMAP sky maps is contaminated by microwave emission from the Milky Way and from extragalactic sources. Therefore, in order to use the maps reliably for cosmological studies, the foreground signals must be well understood and removed from the maps. This thesis focuses on the separation of two foreground contaminants from the WMAP maps: extragalactic point sources and zodiacal light emission. Extragalactic point sources constitute the most important foreground on small angular scales. Various methods have been applied to the WMAP single frequency maps to extract sources. However, due to the limited angular resolution of WMAP, it is possible to confuse positive CMB excursions with point sources or miss sources that are embedded in negative CMB fluctuations. We present a novel CMB-free source finding technique that utilizes the spectrum difference of point sources and CMB to form internal linear combinations of multifrequency maps to suppress the CMB and better reveal sources. When applied to the WMAP 41, 64 and 94 GHz maps, this technique has not only enabled detection of sources that are previously cataloged by independent methods, but also allowed disclosure of new sources. Without the noise contribution from the CMB, this method responds rapidly with the integration time. The number of detections varies as 0( t 0.72 in the two-band search and 0( t 0.70 in the three-band search from one year to five years

  11. Planck 2013 results. XIII. Galactic CO emission

    NASA Astrophysics Data System (ADS)

    Planck Collaboration; Ade, P. A. R.; Aghanim, N.; Alves, M. I. R.; Armitage-Caplan, C.; Arnaud, M.; Ashdown, M.; Atrio-Barandela, F.; Aumont, J.; Baccigalupi, C.; Banday, A. J.; Barreiro, R. B.; Bartlett, J. G.; Battaner, E.; Benabed, K.; Benoît, A.; Benoit-Lévy, A.; Bernard, J.-P.; Bersanelli, M.; Bielewicz, P.; Bobin, J.; Bock, J. J.; Bonaldi, A.; Bond, J. R.; Borrill, J.; Bouchet, F. R.; Boulanger, F.; Bridges, M.; Bucher, M.; Burigana, C.; Butler, R. C.; Cardoso, J.-F.; Catalano, A.; Chamballu, A.; Chary, R.-R.; Chen, X.; Chiang, H. C.; Chiang, L.-Y.; Christensen, P. R.; Church, S.; Clements, D. L.; Colombi, S.; Colombo, L. P. L.; Combet, C.; Couchot, F.; Coulais, A.; Crill, B. P.; Curto, A.; Cuttaia, F.; Danese, L.; Davies, R. D.; de Bernardis, P.; de Rosa, A.; de Zotti, G.; Delabrouille, J.; Delouis, J.-M.; Dempsey, J. T.; Désert, F.-X.; Dickinson, C.; Diego, J. M.; Dole, H.; Donzelli, S.; Doré, O.; Douspis, M.; Dupac, X.; Efstathiou, G.; Enßlin, T. A.; Eriksen, H. K.; Falgarone, E.; Finelli, F.; Forni, O.; Frailis, M.; Franceschi, E.; Fukui, Y.; Galeotta, S.; Ganga, K.; Giard, M.; Giraud-Héraud, Y.; González-Nuevo, J.; Górski, K. M.; Gratton, S.; Gregorio, A.; Gruppuso, A.; Handa, T.; Hansen, F. K.; Hanson, D.; Harrison, D.; Henrot-Versillé, S.; Hernández-Monteagudo, C.; Herranz, D.; Hildebrandt, S. R.; Hily-Blant, P.; Hivon, E.; Hobson, M.; Holmes, W. A.; Hornstrup, A.; Hovest, W.; Huffenberger, K. M.; Hurier, G.; Jaffe, A. H.; Jaffe, T. R.; Jewell, J.; Jones, W. C.; Juvela, M.; Keihänen, E.; Keskitalo, R.; Kisner, T. S.; Knoche, J.; Knox, L.; Kunz, M.; Kurki-Suonio, H.; Lagache, G.; Lähteenmäki, A.; Lamarre, J.-M.; Lasenby, A.; Laureijs, R. J.; Lawrence, C. R.; Leonardi, R.; León-Tavares, J.; Lesgourgues, J.; Liguori, M.; Lilje, P. B.; Linden-Vørnle, M.; López-Caniego, M.; Lubin, P. M.; Macías-Pérez, J. F.; Maffei, B.; Mandolesi, N.; Maris, M.; Marshall, D. J.; Martin, P. G.; Martínez-González, E.; Masi, S.; Massardi, M.; Matarrese, S.; Matthai, F.; Mazzotta, P.; McGehee, P.; Melchiorri, A.; Mendes, L.; Mennella, A.; Migliaccio, M.; Mitra, S.; Miville-Deschênes, M.-A.; Moneti, A.; Montier, L.; Moore, T. J. T.; Morgante, G.; Morino, J.; Mortlock, D.; Munshi, D.; Murphy, J. A.; Nakajima, T.; Naselsky, P.; Nati, F.; Natoli, P.; Netterfield, C. B.; Nørgaard-Nielsen, H. U.; Noviello, F.; Novikov, D.; Novikov, I.; Okuda, T.; Osborne, S.; Oxborrow, C. A.; Paci, F.; Pagano, L.; Pajot, F.; Paladini, R.; Paoletti, D.; Pasian, F.; Patanchon, G.; Perdereau, O.; Perotto, L.; Perrotta, F.; Piacentini, F.; Piat, M.; Pierpaoli, E.; Pietrobon, D.; Plaszczynski, S.; Pointecouteau, E.; Polenta, G.; Ponthieu, N.; Popa, L.; Poutanen, T.; Pratt, G. W.; Prézeau, G.; Prunet, S.; Puget, J.-L.; Rachen, J. P.; Reach, W. T.; Rebolo, R.; Reinecke, M.; Remazeilles, M.; Renault, C.; Ricciardi, S.; Riller, T.; Ristorcelli, I.; Rocha, G.; Rosset, C.; Roudier, G.; Rowan-Robinson, M.; Rubiño-Martín, J. A.; Rusholme, B.; Sandri, M.; Santos, D.; Savini, G.; Scott, D.; Seiffert, M. D.; Shellard, E. P. S.; Spencer, L. D.; Starck, J.-L.; Stolyarov, V.; Stompor, R.; Sudiwala, R.; Sunyaev, R.; Sureau, F.; Sutton, D.; Suur-Uski, A.-S.; Sygnet, J.-F.; Tauber, J. A.; Tavagnacco, D.; Terenzi, L.; Thomas, H. S.; Toffolatti, L.; Tomasi, M.; Torii, K.; Tristram, M.; Tucci, M.; Tuovinen, J.; Umana, G.; Valenziano, L.; Valiviita, J.; Van Tent, B.; Vielva, P.; Villa, F.; Vittorio, N.; Wade, L. A.; Wandelt, B. D.; Wehus, I. K.; Yamamoto, H.; Yoda, T.; Yvon, D.; Zacchei, A.; Zonca, A.

    2014-11-01

    Rotational transition lines of CO play a major role in molecular radio astronomy as a mass tracer and in particular in the study of star formation and Galactic structure. Although a wealth of data exists for the Galactic plane and some well-known molecular clouds, there is no available high sensitivity all-sky survey of CO emission to date. Such all-sky surveys can be constructed using the Planck HFI data because the three lowest CO rotational transition lines at 115, 230 and 345 GHz significantly contribute to the signal of the 100, 217 and 353 GHz HFI channels, respectively. Two different component separation methods are used to extract the CO maps from Planck HFI data. The maps obtained are then compared to one another and to existing external CO surveys. From these quality checks the best CO maps, in terms of signal to noise ratio and/or residual contamination by other emission, are selected. Three different sets of velocity-integrated CO emission maps are produced with different trade-offs between signal-to-noise, angular resolution, and reliability. Maps for the CO J = 1 → 0, J = 2 → 1, and J = 3 → 2 rotational transitions are presented and described in detail. They are shown to be fully compatible with previous surveys of parts of the Galactic plane as well as with undersampled surveys of the high latitude sky. The Planck HFI velocity-integrated CO maps for the J = 1 → 0, J = 2 → 1, and J = 3 →2 rotational transitions provide an unprecedented all-sky CO view of the Galaxy. These maps are also of great interest to monitor potential CO contamination of the Planck studies of the cosmological microwave background.

  12. Cross-correlation analysis of CMB with foregrounds for residuals

    NASA Astrophysics Data System (ADS)

    Aluri, Pavan K.; Rath, Pranati K.

    2016-06-01

    In this paper, we try to probe whether a clean cosmic microwave background (CMB) map obtained from the raw satellite data using a cleaning procedure is sufficiently clean. Specifically, we study if there are any foreground residuals still present in the cleaned data using a cross-correlation statistic. Residual contamination is expected to be present, primarily, in the Galactic plane due to the high emission from our own Galaxy. A foreground mask is applied conventionally to avoid biases in the estimated quantities of interest due to foreground leakage. Here, we map foreground residuals, if present, in the unmasked region i.e. outside a CMB analysis mask. Further locally extended foreground-contaminated regions, found eventually, are studied to understand them better. The few contaminated regions thus identified may be used to slightly extend the available masks to make them more stringent.

  13. The diffuse galactic gamma ray emission

    NASA Technical Reports Server (NTRS)

    Bertsch, David L.

    1990-01-01

    The EGRET (Energetic Gamma-Ray Experiment Telescope) detector will provide a much more detailed view of the diffuse galactic gamma ray intensity in terms of higher resolution, greater statistical significance, and broader energy range than earlier missions. These observations will furnish insight into a number of very important questions related to the dynamics and structure of the Galaxy. A diffuse emission model is being developed that incorporates the latest information on matter distribution and source functions. In addition, it is tailored to the EGRET instrument response functions. The analysis code of the model maintains flexibility to accommodate the quality of the data that is anticipated. The discussion here focuses on the issues of the distributions of matter, cosmic rays, and radiation fields, and on the important source functions that enter into the model calculation of diffuse emission.

  14. Assessment of Models of Galactic Thermal Dust Emission Using COBE/FIRAS and COBE/DIRBE Observations

    NASA Astrophysics Data System (ADS)

    Odegard, N.; Kogut, A.; Chuss, D. T.; Miller, N. J.

    2016-09-01

    Accurate modeling of the spectrum of thermal dust emission at millimeter wavelengths is important for improving the accuracy of foreground subtraction for cosmic microwave background (CMB) measurements, for improving the accuracy with which the contributions of different foreground emission components can be determined, and for improving our understanding of dust composition and dust physics. We fit four models of dust emission to high Galactic latitude COBE/FIRAS and COBE/DIRBE observations from 3 mm to 100 μm and compare the quality of the fits. We consider the two-level systems (TLS) model because it provides a physically motivated explanation for the observed long wavelength flattening of the dust spectrum and the anti-correlation between emissivity index and dust temperature. We consider the model of Finkbeiner et al. because it has been widely used for CMB studies, and the generalized version of this model that was recently applied to Planck data by Meisner and Finkbeiner. For comparison we have also fit a phenomenological model consisting of the sum of two graybody components. We find that the two-graybody model gives the best fit and the FDS model gives a significantly poorer fit than the other models. The Meisner and Finkbeiner model and the TLS model remain viable for use in Galactic foreground subtraction, but the FIRAS data do not have a sufficient signal-to-noise ratio to provide a strong test of the predicted spectrum at millimeter wavelengths.

  15. DUST EMISSION FROM UNOBSCURED ACTIVE GALACTIC NUCLEI

    SciTech Connect

    Thompson, G. D.; Levenson, N. A.; Uddin, S. A.; Sirocky, M. M.

    2009-05-20

    We use mid-infrared (MIR) spectroscopy of unobscured active galactic nuclei (AGNs) to reveal their native dusty environments. We concentrate on Seyfert 1 galaxies, observing a sample of 31 with the Infrared Spectrograph aboard the Spitzer Space Telescope, and compare them with 21 higher luminosity quasar counterparts. Silicate dust reprocessing dominates the MIR spectra, and we generally measure the 10 and 18 {mu}m spectral features weakly in emission in these galaxies. The strengths of the two silicate features together are sensitive to the dust distribution. We present numerical radiative transfer calculations that distinguish between clumpy and smooth geometries, which are applicable to any central heating source, including stars as well as AGNs. In the observations, we detect the obscuring 'torus' of unified AGN schemes, modeling it as compact and clumpy. We also determine that star formation increases with AGN luminosity, although the proportion of the galaxies' bolometric luminosity attributable to stars decreases with AGN luminosity.

  16. Dust Emission from Unobscured Active Galactic Nuclei

    NASA Astrophysics Data System (ADS)

    Thompson, G. D.; Levenson, N. A.; Uddin, S. A.; Sirocky, M. M.

    2009-05-01

    We use mid-infrared (MIR) spectroscopy of unobscured active galactic nuclei (AGNs) to reveal their native dusty environments. We concentrate on Seyfert 1 galaxies, observing a sample of 31 with the Infrared Spectrograph aboard the Spitzer Space Telescope, and compare them with 21 higher luminosity quasar counterparts. Silicate dust reprocessing dominates the MIR spectra, and we generally measure the 10 and 18 μm spectral features weakly in emission in these galaxies. The strengths of the two silicate features together are sensitive to the dust distribution. We present numerical radiative transfer calculations that distinguish between clumpy and smooth geometries, which are applicable to any central heating source, including stars as well as AGNs. In the observations, we detect the obscuring "torus" of unified AGN schemes, modeling it as compact and clumpy. We also determine that star formation increases with AGN luminosity, although the proportion of the galaxies' bolometric luminosity attributable to stars decreases with AGN luminosity.

  17. An Empirical Decomposition of Near-IR Emission into Galactic and Extragalactic Components

    NASA Technical Reports Server (NTRS)

    Dwek, Eli; Arendt, Richard G.

    2002-01-01

    We decompose the COBE/DIRBE observations of the near-IR sky brightness (minus zodiacal light) into Galactic stellar and interstellar medium (ISM) components and an extragalactic background. This empirical procedure allows us to estimate the 4.9 micron cosmic infrared background (CIB) as a function of the CIB intensity at shorter wavelengths. A weak indication of a rising CIB intensity at wavelengths greater than 3.5$ microns hints at interesting astrophysics in the CIB spectrum, or warns that the foreground zodiacal emission may be incompletely subtracted. Subtraction of only the stellar component from the zodiacal-light-subtracted all--sky map reveals the clearest 3.5 micron ISM emission map, which is found to be tightly correlated with the ISM emission at far-IR wavelengths.

  18. ANALYSIS OF WMAP 7 YEAR TEMPERATURE DATA: ASTROPHYSICS OF THE GALACTIC HAZE

    SciTech Connect

    Pietrobon, Davide; Gorski, Krzysztof M.; Bartlett, James; Colombo, Loris P. L.; Jewell, Jeffrey B.; Pagano, Luca; Rocha, Graca; Lawrence, Charles R.; Banday, A. J.; Dobler, Gregory; Hildebrandt, Sergi R.; Eriksen, Hans Kristian; Saha, Rajib

    2012-08-10

    We perform a joint analysis of the cosmic microwave background (CMB) and Galactic emission from the WMAP 7 year temperature data. Using the Commander code, based on Gibbs sampling, we simultaneously derive the CMB and Galactic components on scales larger than 1 Degree-Sign with improved sensitivity over previous work. We conduct a detailed study of the low-frequency Galactic foreground, focusing on the 'microwave haze' emission around the Galactic center. We demonstrate improved performance in quantifying the diffuse Galactic emission when including Haslam 408 MHz data and when jointly modeling the spinning and thermal dust emission. We examine whether the hypothetical Galactic haze can be explained by a spatial variation of the synchrotron spectral index, and find that the excess of emission around the Galactic center is stable with respect to variations of the foreground model. Our results demonstrate that the new Galactic foreground component-the microwave haze-is indeed present.

  19. SAS-2 galactic gamma-ray results. 1: Diffuse emission

    NASA Technical Reports Server (NTRS)

    Thompson, D. J.; Fichtel, C. E.; Hartman, R. C.; Kniffen, D. A.; Bignami, G. F.; Lamb, R. C.; Oegelman, H.; Oezel, M. E.; Tuemer, T.

    1977-01-01

    Continuing analysis of the data from the SAS-2 high energy gamma ray experiment has produced an improved picture of the sky at photon energies above 35 MeV. On a large scale, the diffuse emission from the galactic plane is the dominant feature observed by SAS-2. This galactic plane emission is most intense between galactic longitudes 310 deg and 45 deg, corresponding to a region within 7 kpc of the galactic center. Within the high-intensity region, SAS-2 observes peaks around galactic longitudes 315, 330, 345, 0, and 35 deg. These peaks appear to be correlated with galactic features and components such as molecular hydrogen, atomic hydrogen, magnetic fields, cosmic-ray concentrations, and photon fields.

  20. emission from stars and dust in the Galactic plane

    NASA Technical Reports Server (NTRS)

    2002-01-01

    Annual Average Maps at 3.5, 25, 100, and 240 Aum. Galactic coordinate Mollweide projection maps of the entire sky at four wavelengths showing emission from stars and dust in the Galactic plane (horizontal feature) and light scattered and emitted by dust in the solar system (S-shape).

  1. Synchrotron Emission Model from a Hypothetical Galactic Wind

    NASA Astrophysics Data System (ADS)

    Schiller, Quintin; Everett, J.; Zwiebel, E.

    2007-12-01

    The ROSAT All Sky Survey (Snowden et al. 1993) discovered a pill-box shaped region of X-ray emission towards the galactic center. Elsewhere, we postulate that the emission is caused by a cosmic-ray and thermally driven Galactic wind (Everett et al, submitted). The objective of this project is to model synchrotron emission from a hypothetical Galactic wind to see whether the model can be tested with radio observations. The wind is launched from the Galactic disk from Galactic radii 1.5 kpc < R < 4.5 kpc to 1 Mpc in height. Observations of the corresponding cylindrical annulus geometry are simulated from Earth at z=0 height and R=8 kpc. We begin with a Galactic wind model fit by Everett et al. to the X-ray emission and integrate the equation for synchrotron intensity on lines of sight through the wind. Initially, we model simple launch geometry to validate our tools and compare the results with analytic single-ray calculations to verify accuracy. We choose to model synchrotron radiation at 1.5 GHz as all-sky surveys observe near this frequency. The result of the model currently predicts that the synchrotron flux from the Galactic wind should be observable using radio telescopes, such as the Green Bank Telescope in West Virginia, to Galactic latitude b +/- 20 degrees and Galactic longitude l +/- 35 degrees. Comparisons to all-sky surveys will test the existence of a wind-driven synchrotron spectrum. If a synchrotron spectrum comparable to the Galactic wind model is observed, it could provide evidence for the existence of a cosmic-ray and thermally driven Galactic wind.

  2. [C II] absorption and emission in the diffuse interstellar medium across the Galactic plane

    NASA Astrophysics Data System (ADS)

    Gerin, M.; Ruaud, M.; Goicoechea, J. R.; Gusdorf, A.; Godard, B.; de Luca, M.; Falgarone, E.; Goldsmith, P.; Lis, D. C.; Menten, K. M.; Neufeld, D.; Phillips, T. G.; Liszt, H.

    2015-01-01

    Aims: Ionized carbon is the main gas-phase reservoir of carbon in the neutral diffuse interstellar medium (ISM) and its 158 μm fine structure transition [C ii] is the most important cooling line of the diffuse ISM. We combine [C ii] absorption and emission spectroscopy to gain an improved understanding of physical conditions in the different phases of the ISM. Methods: We present high-resolution [C ii] spectra obtained with the Herschel/HIFI instrument towards bright dust continuum regions in the Galactic plane, probing simultaneously the diffuse gas along the line of sight and the background high-mass star forming regions. These data are complemented by single pointings in the 492 and 809 GHz fine structure lines of atomic carbon and by medium spectral resolution spectral maps of the fine structure lines of atomic oxygen at 63 and 145 μm with Herschel/PACS. Results: We show that the presence of foreground absorption may completely cancel the emission from the background source in medium spectral resolution PACS data and that high spectral resolution spectra are needed to interpret the [C ii] and [O i] emission and the [C ii]/FIR ratio. This phenomenon may explain part of the [C ii]/FIR deficit seen in external luminous infrared galaxies where the bright emission from the nuclear regions may be partially canceled by absorption from diffuse gas in the foreground. The C+ and C excitation in the diffuse gas is consistent with a median pressure of ~5900 K cm-3 for a mean kinetic temperature of ~100 K. A few higher pressure regions are detected along the lines of sight, as emission features in both fine structure lines of atomic carbon. The knowledge of the gas density allows us to determine the filling factor of the absorbing gas along the selected lines of sight. The derived median value of the filling factor is 2.4%, in good agreement with the properties of the Galactic cold neutral medium. The mean excitation temperature is used to derive the average cooling due

  3. A model of diffuse Galactic radio emission from 10 MHz to 100 GHz

    NASA Astrophysics Data System (ADS)

    de Oliveira-Costa, Angélica; Tegmark, Max; Gaensler, B. M.; Jonas, Justin; Landecker, T. L.; Reich, Patricia

    2008-07-01

    Understanding diffuse Galactic radio emission is interesting both in its own right and for minimizing foreground contamination of cosmological measurements. cosmic microwave background experiments have focused on frequencies >~10GHz, whereas 21-cm tomography of the high-redshift universe will mainly focus on <~0.2GHz, for which less is currently known about Galactic emission. Motivated by this, we present a global sky model derived from all publicly available total power large-area radio surveys, digitized with optical character recognition when necessary and compiled into a uniform format, as well as the new Villa Elisa data extending the 1.42-GHz map to the entire sky. We quantify statistical and systematic uncertainties in these surveys by comparing them with various global multifrequency model fits. We find that a principal component based model with only three components can fit the 11 most accurate data sets (at 10, 22, 45 and 408 MHz and 1.42, 2.326, 23, 33, 41, 61, 94 GHz) to an accuracy around 1-10 per cent depending on frequency and sky region. Both our data compilation and our software returning a predicted all-sky map at any frequency from 10 MHz to 100 GHz are publicly available at http://space.mit.edu/home/angelica/gsm.

  4. Diffuse Galactic low energy gamma ray continuum emission

    NASA Technical Reports Server (NTRS)

    Skibo, J. G.; Ramaty, R.

    1993-01-01

    We investigate the origin of diffuse low-energy Galactic gamma-ray continuum down to about 30 keV. We calculate gamma-ray emission via bremsstrahlung and inverse Compton scattering by propagating an unbroken electron power law injection spectrum and employing a Galactic emmissivity model derived from COSB observations. To maintain the low energy electron population capable of producing the observed continuum via bremsstrahlung, a total power input of 4 x 10 exp 41 erg/s is required. This exceeds the total power supplied to the nuclear cosmic rays by about an order of magnitude.

  5. Diffuse Gamma Rays Galactic and Extragalactic Diffuse Emission

    NASA Technical Reports Server (NTRS)

    Moskalenko, Igor V.; Strong, Andrew W.; Reimer, Olaf

    2004-01-01

    Diffuse gamma rays consist of several components: truly diffuse emission from the interstellar medium, the extragalactic background, whose origin is not firmly established yet, and the contribution from unresolved and faint Galactic point sources. One approach to unravel these components is to study the diffuse emission from the interstellar medium, which traces the interactions of high energy particles with interstellar gas and radiation fields. Because of its origin such emission is potentially able to reveal much about the sources and propagation of cosmic rays. The extragalactic background, if reliably determined, can be used in cosmological and blazar studies. Studying the derived average spectrum of faint Galactic sources may be able to give a clue to the nature of the emitting objects.

  6. Diffuse γ-ray emission from galactic pulsars

    SciTech Connect

    Calore, F.; Di Mauro, M.; Donato, F. E-mail: mattia.dimauro@to.infn.it

    2014-11-20

    Millisecond pulsars (MSPs) are old fast-spinning neutron stars that represent the second most abundant source population discovered by the Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope (Fermi). As guaranteed γ-ray emitters, they might contribute non-negligibly to the diffuse emission measured at high latitudes by Fermi-LAT (i.e., the Isotropic Diffuse γ-Ray Background (IDGRB)), which is believed to arise from the superposition of several components of galactic and extragalactic origin. Additionally, γ-ray sources also contribute to the anisotropy of the IDGRB measured on small scales by Fermi-LAT. In this manuscript we aim to assess the contribution of the unresolved counterpart of the detected MSPs population to the IDGRB and the maximal fraction of the measured anisotropy produced by this source class. To this end, we model the MSPs' spatial distribution in the Galaxy and the γ-ray emission parameters by considering observational constraints coming from the Australia Telescope National Facility pulsar catalog and the Second Fermi-LAT Catalog of γ-ray pulsars. By simulating a large number of MSP populations through a Monte Carlo simulation, we compute the average diffuse emission and the anisotropy 1σ upper limit. We find that the emission from unresolved MSPs at 2 GeV, where the peak of the spectrum is located, is at most 0.9% of the measured IDGRB above 10° in latitude. The 1σ upper limit on the angular power for unresolved MSP sources turns out to be about a factor of 60 smaller than Fermi-LAT measurements above 30°. Our results indicate that this galactic source class represents a negligible contributor to the high-latitude γ-ray sky and confirm that most of the intensity and geometrical properties of the measured diffuse emission are imputable to other extragalactic source classes (e.g., blazars, misaligned active galactic nuclei, or star-forming galaxies). Nevertheless, because MSPs are more concentrated toward the

  7. Planck intermediate results. XXX. The angular power spectrum of polarized dust emission at intermediate and high Galactic latitudes

    NASA Astrophysics Data System (ADS)

    Planck Collaboration; Adam, R.; Ade, P. A. R.; Aghanim, N.; Arnaud, M.; Aumont, J.; Baccigalupi, C.; Banday, A. J.; Barreiro, R. B.; Bartlett, J. G.; Bartolo, N.; Battaner, E.; Benabed, K.; Benoit-Lévy, A.; Bernard, J.-P.; Bersanelli, M.; Bielewicz, P.; Bonaldi, A.; Bonavera, L.; Bond, J. R.; Borrill, J.; Bouchet, F. R.; Boulanger, F.; Bracco, A.; Bucher, M.; Burigana, C.; Butler, R. C.; Calabrese, E.; Cardoso, J.-F.; Catalano, A.; Challinor, A.; Chamballu, A.; Chary, R.-R.; Chiang, H. C.; Christensen, P. R.; Clements, D. L.; Colombi, S.; Colombo, L. P. L.; Combet, C.; Couchot, F.; Coulais, A.; Crill, B. P.; Curto, A.; Cuttaia, F.; Danese, L.; Davies, R. D.; Davis, R. J.; de Bernardis, P.; de Zotti, G.; Delabrouille, J.; Delouis, J.-M.; Désert, F.-X.; Dickinson, C.; Diego, J. M.; Dolag, K.; Dole, H.; Donzelli, S.; Doré, O.; Douspis, M.; Ducout, A.; Dunkley, J.; Dupac, X.; Efstathiou, G.; Elsner, F.; Enßlin, T. A.; Eriksen, H. K.; Falgarone, E.; Finelli, F.; Forni, O.; Frailis, M.; Fraisse, A. A.; Franceschi, E.; Frejsel, A.; Galeotta, S.; Galli, S.; Ganga, K.; Ghosh, T.; Giard, M.; Giraud-Héraud, Y.; Gjerløw, E.; González-Nuevo, J.; Górski, K. M.; Gratton, S.; Gregorio, A.; Gruppuso, A.; Guillet, V.; Hansen, F. K.; Hanson, D.; Harrison, D. L.; Helou, G.; Henrot-Versillé, S.; Hernández-Monteagudo, C.; Herranz, D.; Hivon, E.; Hobson, M.; Holmes, W. A.; Huffenberger, K. M.; Hurier, G.; Jaffe, A. H.; Jaffe, T. R.; Jewell, J.; Jones, W. C.; Juvela, M.; Keihänen, E.; Keskitalo, R.; Kisner, T. S.; Kneissl, R.; Knoche, J.; Knox, L.; Krachmalnicoff, N.; Kunz, M.; Kurki-Suonio, H.; Lagache, G.; Lamarre, J.-M.; Lasenby, A.; Lattanzi, M.; Lawrence, C. R.; Leahy, J. P.; Leonardi, R.; Lesgourgues, J.; Levrier, F.; Liguori, M.; Lilje, P. B.; Linden-Vørnle, M.; López-Caniego, M.; Lubin, P. M.; Macías-Pérez, J. F.; Maffei, B.; Maino, D.; Mandolesi, N.; Mangilli, A.; Maris, M.; Martin, P. G.; Martínez-González, E.; Masi, S.; Matarrese, S.; Mazzotta, P.; Meinhold, P. R.; Melchiorri, A.; Mendes, L.; Mennella, A.; Migliaccio, M.; Mitra, S.; Miville-Deschênes, M.-A.; Moneti, A.; Montier, L.; Morgante, G.; Mortlock, D.; Moss, A.; Munshi, D.; Murphy, J. A.; Naselsky, P.; Nati, F.; Natoli, P.; Netterfield, C. B.; Nørgaard-Nielsen, H. U.; Noviello, F.; Novikov, D.; Novikov, I.; Pagano, L.; Pajot, F.; Paladini, R.; Paoletti, D.; Partridge, B.; Pasian, F.; Patanchon, G.; Pearson, T. J.; Perdereau, O.; Perotto, L.; Perrotta, F.; Pettorino, V.; Piacentini, F.; Piat, M.; Pierpaoli, E.; Pietrobon, D.; Plaszczynski, S.; Pointecouteau, E.; Polenta, G.; Ponthieu, N.; Popa, L.; Pratt, G. W.; Prunet, S.; Puget, J.-L.; Rachen, J. P.; Reach, W. T.; Rebolo, R.; Remazeilles, M.; Renault, C.; Renzi, A.; Ricciardi, S.; Ristorcelli, I.; Rocha, G.; Rosset, C.; Rossetti, M.; Roudier, G.; Rouillé d'Orfeuil, B.; Rubiño-Martín, J. A.; Rusholme, B.; Sandri, M.; Santos, D.; Savelainen, M.; Savini, G.; Scott, D.; Soler, J. D.; Spencer, L. D.; Stolyarov, V.; Stompor, R.; Sudiwala, R.; Sunyaev, R.; Sutton, D.; Suur-Uski, A.-S.; Sygnet, J.-F.; Tauber, J. A.; Terenzi, L.; Toffolatti, L.; Tomasi, M.; Tristram, M.; Tucci, M.; Tuovinen, J.; Valenziano, L.; Valiviita, J.; Van Tent, B.; Vibert, L.; Vielva, P.; Villa, F.; Wade, L. A.; Wandelt, B. D.; Watson, R.; Wehus, I. K.; White, M.; White, S. D. M.; Yvon, D.; Zacchei, A.; Zonca, A.

    2016-02-01

    The polarized thermal emission from diffuse Galactic dust is the main foreground present in measurements of the polarization of the cosmic microwave background (CMB) at frequencies above 100 GHz. In this paper we exploit the uniqueness of the Planck HFI polarization data from 100 to 353 GHz to measure the polarized dust angular power spectra CℓEE and CℓBB over the multipole range 40 <ℓ< 600 well away from the Galactic plane. These measurements will bring new insights into interstellar dust physics and allow a precise determination of the level of contamination for CMB polarization experiments. Despite the non-Gaussian and anisotropic nature of Galactic dust, we show that general statistical properties of the emission can be characterized accurately over large fractions of the sky using angular power spectra. The polarization power spectra of the dust are well described by power laws in multipole, Cℓ ∝ ℓα, with exponents αEE,BB = -2.42 ± 0.02. The amplitudes of the polarization power spectra vary with the average brightness in a way similar to the intensity power spectra. The frequency dependence of the dust polarization spectra is consistent with modified blackbody emission with βd = 1.59 and Td = 19.6 K down to the lowest Planck HFI frequencies. We find a systematic difference between the amplitudes of the Galactic B- and E-modes, CℓBB/CℓEE = 0.5. We verify that these general properties are preserved towards high Galactic latitudes with low dust column densities. We show that even in the faintest dust-emitting regions there are no "clean" windows in the sky where primordial CMB B-mode polarization measurements could be made without subtraction of foreground emission. Finally, we investigate the level of dust polarization in the specific field recently targeted by the BICEP2 experiment. Extrapolation of the Planck 353 GHz data to 150 GHz gives a dust power 𝒟ℓBB ≡ ℓ(ℓ+1)CℓBB/(2π) of 1.32 × 10-2 μKCMB2 over the multipole range

  8. X-ray emission from the galactic disk.

    NASA Technical Reports Server (NTRS)

    Bleach, R. D.; Boldt, E. A.; Holt, S. S.; Schwartz, D. A.; Serlemitsos, P. J.

    1972-01-01

    A search was made for a diffuse component of greater than 1.5 keV X rays associated with an interarm region of the Galaxy at galactic longitudes in the vicinity of 60 degrees. A statistically significant excess associated with a narrow disk component was detected. The angular extent of this component has a most probable value of 2 degrees. The best-fit spectrum yields an intensity of 2.9 photons/sq cm per sec per sterad over the 2-10 keV range. The 3-sigma upper limit to any emission in a 1.5 keV band centered at 7 keV from galactic latitudes not greater than 3.5 deg is 0.3 photons/sq cm per sec per sterad. Several possible emission models are evaluated, with the most likely choice being a population of unresolvable low-luminosity sources.

  9. THE LOCAL DUST FOREGROUNDS IN THE MICROWAVE SKY. I. THERMAL EMISSION SPECTRA

    SciTech Connect

    Dikarev, Valeri; Preuss, Oliver; Solanki, Sami; Krueger, Harald; Krivov, Alexander

    2009-11-01

    Analyses of the cosmic microwave background (CMB) radiation maps made by the Wilkinson Microwave Anisotropy Probe (WMAP) have revealed anomalies not predicted by the standard inflationary cosmology. In particular, the power of the quadrupole moment of the CMB fluctuations is remarkably low, and the quadrupole and octopole moments are aligned mutually and with the geometry of the solar system. It has been suggested in the literature that microwave sky pollution by an unidentified dust cloud in the vicinity of the solar system may be the cause for these anomalies. In this paper, we simulate the thermal emission by clouds of spherical homogeneous particles of several materials. Spectral constraints from the WMAP multi-wavelength data and earlier infrared observations on the hypothetical dust cloud are used to determine the dust cloud's physical characteristics. In order for its emissivity to demonstrate a flat, CMB-like wavelength dependence over the WMAP wavelengths (3 through 14 mm), and to be invisible in the infrared light, its particles must be macroscopic. Silicate spheres of several millimeters in size and carbonaceous particles an order of magnitude smaller will suffice. According to our estimates of the abundance of such particles in the zodiacal cloud and trans-Neptunian belt, yielding the optical depths of the order of 10{sup -7} for each cloud, the solar system dust can well contribute 10 muK (within an order of magnitude) in the microwaves. This is not only intriguingly close to the magnitude of the anomalies (about 30 muK), but also alarmingly above the presently believed magnitude of systematic biases of the WMAP results (below 5 muK) and, to an even greater degree, of the future missions with higher sensitivities, e.g., Planck.

  10. NuSTAR results from the Galactic Center - diffuse emission

    NASA Astrophysics Data System (ADS)

    Hailey, Charles

    2016-03-01

    The Nuclear Spectroscopic Telescope Array (NuSTAR) was launched in June 2012. It carried the first true, hard X-ray (>~10 keV-79 keV) focusing telescopes into orbit. Its twin telescopes provide 10 times better angular resolution and 100 times better sensitivity than previously obtainable in the hard X-ray band. Consequently NuSTAR is able to resolve faint diffuse structures whose hard X-rays offer insight into some of the most energetic processes in the Galactic Center. One of the surprising discoveries that NuSTAR made in the Galactic Center is the central hard X-ray emission (CHXE). The CHXE is a diffuse emission detected from ~10 keV to beyond 50 keV in X-ray energy, and extending spatially over a region ~8 parsecs x ~4 parsecs in and out of the plane of the galaxy respectively, and centered on the supermassive black hole Sgr A*. The CHXE was speculated to be due to a large population of unresolved black hole X-ray binaries, millisecond pulsars (MSP), a class of highly magnetized white dwarf binaries called intermediate polars, or to particle outflows from Sgr A*. The presence of an unexpectedly large population of MSP in the Galactic Center would be particularly interesting, since MSP emitting at higher energies and over a much larger region have been posited to be the origin of the gamma-ray emission that is also ascribed to dark matter annihilation in the galaxy. In addition, the connection of the CHXE to the ~9000 unidentified X-ray sources in the central the the ~100 pc detected by the Chandra Observatory, to the soft X-ray emission detected by the Chandra and XMM/Newton observatories in the Galactic Center, and to the hard X-ray emission detected by both the RXTE and INTEGRAL observatories in the Galactic Ridge, is unclear. I review these results and present recent NuSTAR observations that potentially resolve the origin of the CHXE and point to a unified origin for all these X-ray emissions. Two other noteworthy classes of diffuse structures in the

  11. XMM-Newton and Suzaku X-Ray Shadowing Measurements of the Solar Wind Charge Exchange, Local Bubble, and Galactic Halo Emission

    NASA Astrophysics Data System (ADS)

    Henley, David B.; Shelton, Robin L.

    2015-07-01

    We present results from a sample of XMM-Newton and Suzaku observations of interstellar clouds that cast shadows in the soft X-ray background (SXRB)—the first uniform analysis of such a sample from these missions. By fitting to the on- and off-shadow spectra, we separated the foreground and Galactic halo components of the SXRB. We tested different foreground models—two solar wind charge exchange (SWCX) models and a Local Bubble (LB) model. We also examined different abundance tables. We found that Anders & Grevesse abundances, commonly used in previous SXRB studies, may result in overestimated foreground brightnesses and halo temperatures. We also found that assuming a single solar wind ionization temperature for a SWCX model can lead to unreliable results. We compared our measurements of the foreground emission with predictions of the SWCX emission from a smooth solar wind, finding only partial agreement. Using available observation-specific SWCX predictions and various plausible assumptions, we placed an upper limit on the LB's O vii intensity of ˜0.8 {{photons}} {{{cm}}}-2 {{{s}}}-1 {{{sr}}}-1 (90% confidence). Comparing the halo results obtained with SWCX and LB foreground models implies that, if the foreground is dominated by SWCX and is brighter than ˜1.5× {10}-12 {{erg}} {{{cm}}}-2 {{{s}}}-1 {{{deg}}}-2 (0.4-1.0 {{keV}}), then using an LB foreground model may bias the halo temperature upward and the 0.5-2.0 {{keV}} surface brightness downward by ˜(0.2-0.3)× {10}6 {{K}} and ˜(1-2)× {10}-12 {{erg}} {{{cm}}}-2 {{{s}}}-1 {{{deg}}}-2, respectively. Similarly, comparing results from different observatories implies that there may be uncertainties in the halo temperature and surface brightness of up to ˜0.2× {10}6 {{K}} and ˜25%, respectively, in addition to the statistical uncertainties. These uncertainties or biases may limit the ability of X-ray measurements to discriminate between Galactic halo models.

  12. XMM-Newton and Suzaku X-Ray Shadowing Measurements of the Solar Wind Charge Exchange, Local Bubble, and Galactic Halo Emission

    NASA Astrophysics Data System (ADS)

    Henley, David B.; Shelton, Robin L.

    2015-07-01

    We present results from a sample of XMM-Newton and Suzaku observations of interstellar clouds that cast shadows in the soft X-ray background (SXRB)—the first uniform analysis of such a sample from these missions. By fitting to the on- and off-shadow spectra, we separated the foreground and Galactic halo components of the SXRB. We tested different foreground models—two solar wind charge exchange (SWCX) models and a Local Bubble (LB) model. We also examined different abundance tables. We found that Anders & Grevesse abundances, commonly used in previous SXRB studies, may result in overestimated foreground brightnesses and halo temperatures. We also found that assuming a single solar wind ionization temperature for a SWCX model can lead to unreliable results. We compared our measurements of the foreground emission with predictions of the SWCX emission from a smooth solar wind, finding only partial agreement. Using available observation-specific SWCX predictions and various plausible assumptions, we placed an upper limit on the LB's O vii intensity of ∼0.8 {{photons}} {{{cm}}}-2 {{{s}}}-1 {{{sr}}}-1 (90% confidence). Comparing the halo results obtained with SWCX and LB foreground models implies that, if the foreground is dominated by SWCX and is brighter than ∼1.5× {10}-12 {{erg}} {{{cm}}}-2 {{{s}}}-1 {{{deg}}}-2 (0.4–1.0 {{keV}}), then using an LB foreground model may bias the halo temperature upward and the 0.5–2.0 {{keV}} surface brightness downward by ∼(0.2-0.3)× {10}6 {{K}} and ∼(1-2)× {10}-12 {{erg}} {{{cm}}}-2 {{{s}}}-1 {{{deg}}}-2, respectively. Similarly, comparing results from different observatories implies that there may be uncertainties in the halo temperature and surface brightness of up to ∼0.2× {10}6 {{K}} and ∼25%, respectively, in addition to the statistical uncertainties. These uncertainties or biases may limit the ability of X-ray measurements to discriminate between Galactic halo models.

  13. GALACTIC CEPHEIDS WITH SPITZER. II. SEARCH FOR EXTENDED INFRARED EMISSION

    SciTech Connect

    Barmby, P.; Marengo, M.; Evans, N. R.; Huelsman, D.; Fazio, G. G.; Bono, G.; Su, K. Y. L.; Welch, D. L.

    2011-02-15

    A deep and detailed examination of 29 classical Cepheids with the Spitzer Space Telescope has revealed three stars with strong nearby extended emission detected in multiple bands which appears to be physically associated with the stars. RS Pup was already known to possess extended infrared emission, while the extended emission around the other two stars (S Mus and {delta} Cep) is newly discovered in our observations. Four other stars (GH Lup, l Car, T Mon, and X Cyg) show tentative evidence for extended infrared emission. An unusual elongated extended object next to SZ Tau appears to be a background or foreground object in a chance alignment with the Cepheid. The inferred mass-loss rate upper limits for S Mus and {delta} Cep are in the range from 10{sup -9} to 10{sup -8} M{sub sun} yr{sup -1}, with the upper limit for RS Pup as high as 10{sup -6} M{sub sun} yr{sup -1}. Mass loss during post-main-sequence evolution has been proposed as a resolution to the discrepancy between pulsational and dynamical masses of Cepheid variable stars: dust in the lost material would make itself known by the presence of an infrared bright nebula or unresolved infrared excess. The observed frequency of infrared circumstellar emission (<24%) and the mass-loss rate we estimate for our sources show that dusty mass loss can only account for part of the Cepheid mass-loss discrepancy. Nevertheless, our direct evidence that mass loss is active during the Cepheid phase is an important confirmation that these processes need to be included in evolutionary and pulsation models of these stars and should be taken into account in the calibration of the Cepheid distance scale.

  14. DARK MATTER AND SYNCHROTRON EMISSION FROM GALACTIC CENTER RADIO FILAMENTS

    SciTech Connect

    Linden, Tim; Hooper, Dan; Yusef-Zadeh, Farhad

    2011-11-10

    The inner degrees of the Galactic center contain a large population of filamentary structures observed at radio frequencies. These so-called non-thermal radio filaments (NRFs) trace magnetic field lines and have attracted significant interest due to their hard (S{sub v} {proportional_to}{nu}{sup -0.1{+-}0.4}) synchrotron emission spectra. The origin of these filaments remains poorly understood. We show that the electrons and positrons created through the annihilations of a relatively light ({approx}5-10 GeV) dark matter particle with the cross section predicted for a simple thermal relic can provide a compelling match to the intensity, spectral shape, and flux variation of the NRFs. Furthermore, the characteristics of the dark matter particle necessary to explain the synchrotron emission from the NRFs are consistent with those required to explain the excess {gamma}-ray emission observed from the Galactic center by the Fermi Large Area Telescope, as well as the direct detection signals observed by CoGeNT and DAMA/LIBRA.

  15. Dark Matter and Synchrotron Emission from Galactic Center Radio Filaments

    SciTech Connect

    Linden, Tim; Hooper, Dan; Yusef-Zadeh, Farhad

    2011-11-10

    The inner degrees of the Galactic center contain a large population of filamentary structures observed at radio frequencies. These so-called non-thermal radio filaments (NRFs) trace magnetic field lines and have attracted significant interest due to their hard (S_v ~ -0.1 +/- 0.4) synchrotron emission spectra. The origin of these filaments remains poorly understood. We show that the electrons and positrons created through the annihilations of a relatively light (~5-10 GeV) dark matter particle with the cross section predicted for a simple thermal relic can provide a compelling match to the intensity, spectral shape, and flux variation of the NRFs. Furthermore, the characteristics of the dark matter particle necessary to explain the synchrotron emission from the NRFs is consistent with those required to explain the excess gamma-ray emission observed from the Galactic center by the Fermi-LAT, as well as the direct detection signals observed by CoGeNT and DAMA/LIBRA.

  16. X-ray emission from the galactic disk

    NASA Technical Reports Server (NTRS)

    Bleach, R. D.; Boldt, E. A.; Holt, S. S.; Schwartz, D. A.; Serlemitsos, P. J.

    1972-01-01

    A search was made of a diffuse component of X-rays 1.5 keV associated with an interarm region of the galaxy at galactic longitudes in the vicinity of 60 deg. A statistically significant excess associated with a narrow disk component was detected. The angular extent of this component has a most probable value of 2 deg and may be as large as 7 deg at 90% confidence. The best fit spectrum yields an intensity of 2.9 photons 1/(cm2-sec-ster) over the 2 to 10 keV range. The 3 sigma upper limit to any emission (e.g. iron line) in a 1.5 keV band centered at 7 keV from galactic latitudes h or = 3.5 deg is .3 photons 1/(cm2-sec-ster). Several possible emission models are discussed, with the most likely candidate being a population of unresolvable low luminosity discrete sources.

  17. Emission-line objects projected upon the galactic bulge.

    PubMed

    Herbig, G H

    1969-08-01

    Low-dispersion slit spectrograms have been obtained of 34 faint objects that lie in the direction of the galactic bulge and have the Halpha line in emission upon a detectable continuum. Eleven of these are certain or probable symbiotic stars. A rough comparison with R CrB stars in the same area suggests that these brightest symbiotics in the bulge have in the mean M(v) approximately -3 to -4, which suggest Population II red giants rather than conventional Population I M-type objects. The sample also contains a number of hot stars having H and [O II] or [O III] in emission, as well as four conventional Be stars, and six certain or possible planetary nebulae. PMID:16578699

  18. Global Sky Model (GSM): A Model of Diffuse Galactic Radio Emission from 10 MHz to 100 GHz

    NASA Astrophysics Data System (ADS)

    de Oliveira-Costa, Angelica; Tegmark, Max; Gaensler, B. M.; Jonas, Justin; Landecker, T. L.; Reich, Patricia

    2010-11-01

    Understanding diffuse Galactic radio emission is interesting both in its own right and for minimizing foreground contamination of cosmological measurements. Cosmic Microwave Background experiments have focused on frequencies > 10 GHz, whereas 21 cm tomography of the high redshift universe will mainly focus on < 0.2 GHz, for which less is currently known about Galactic emission. Motivated by this, we present a global sky model derived from all publicly available total power large-area radio surveys, digitized with optical character recognition when necessary and compiled into a uniform format, as well as the new Villa Elisa data extending the 1.4 GHz map to the entire sky. We quantify statistical and systematic uncertainties in these surveys by comparing them with various global multi-frequency model fits. We find that a principal component based model with only three components can fit the 11 most accurate data sets (at 10, 22, 45 & 408 MHz and 1.4, 2.3, 23, 33, 41, 61, 94 GHz) to an accuracy around 1%-10% depending on frequency and sky region. The data compilation and software returning a predicted all-sky map at any frequency from 10 MHz to 100 GHz are publicly available at the link below.

  19. SiO Emission in the Galactic Center

    NASA Astrophysics Data System (ADS)

    Minh, Young Chol; Liu, Hauyu Baobab; Su, Yu-Nung; Hsieh, Pei-Ying; Liu, Sheng-Yuan; Kim, Sungsoo S.; Wright, Melvyn; Ho, Paul T. P.

    2015-07-01

    The gas traced by the SiO 1-0 emission appears to not have a direct connection or interaction with the circumnuclear disk (CND). In contrast, higher-resolution observations of the SiO 5-4 emission confirm the dissymmetric gas distribution of the CND, as well as a large concentration of gas in the CND’s southwest region. In particular, the SiO 5-4 emission peaks toward what is likely the “convergent” position, where the west arc of Sgt A West overlaps with the CND. We think that this is the position where several incoming and outgoing gas flows interact with each other. The high angular resolution (˜ 1\\buildrel{\\prime\\prime}\\over{.} 5) observations of the SiO 5-4 emission show several emission clumps with sizes ˜ 2\\prime\\prime . These clumps have different velocities that may have resulted from a collision with incoming clouds. We confirm that the overall fractional abundance of SiO is about 10-9 relative to the total H2, and it probably resulted from the large-scale shocks prevalent in the Galactic center region. A comparison of the SiO fractional abundance suggests that in addition to the dense ambient cloud component, which surrounds but does not interact much with the CND, there are separate gas components that have more interactions with the CND.

  20. SCATTERED EMISSION FROM z {approx} 1 GALACTIC OUTFLOWS

    SciTech Connect

    Martin, Crystal L.; Pancoast, Anna; Shapley, Alice E.; Kornei, Katherine A.; Coil, Alison L.; Murray, Norman

    2013-06-10

    Mapping Mg II resonance emission scattered by galactic winds offers a means to determine the spatial extent and density of the warm outflow. Using Keck/LRIS spectroscopy, we have resolved scattered Mg II emission to the east of 32016857, a star-forming galaxy at z = 0.9392 with an outflow. The Mg II emission from this galaxy exhibits a P-Cygni profile, extends further than both the continuum and [O II] emission along the eastern side of the slit, and has a constant Doppler shift along the slit which does not follow the velocity gradient of the nebular [O II] emission. Using the Sobolev approximation, we derive the density of Mg{sup +} ions at a radius of 12-18 kpc in the outflow. We model the ionization correction and find that much of the outflowing Mg is in Mg{sup ++}. We estimate that the total mass flux could be as large as 330-500 M{sub Sun} yr{sup -1}, with the largest uncertainties coming from the depletion of Mg onto grains and the clumpiness of the warm outflow. We show that confining the warm clouds with a hot wind reduces the estimated mass flux of the warm outflow and indicates a mass-loading factor near unity in the warm phase alone. Based on the high blue luminosities that distinguish 32016857 and TKRS 4389, described by Rubin et al., from other galaxies with P-Cygni emission, we suggest that, as sensitivity to diffuse emission improves, scattering halos may prove to be a generic property of star-forming galaxies at intermediate redshifts.

  1. Epoch of reionization window. II. Statistical methods for foreground wedge reduction

    NASA Astrophysics Data System (ADS)

    Liu, Adrian; Parsons, Aaron R.; Trott, Cathryn M.

    2014-07-01

    For there to be a successful measurement of the 21 cm epoch of reionization (EoR) power spectrum, it is crucial that strong foreground contaminants be robustly suppressed. These foregrounds come from a variety of sources (such as Galactic synchrotron emission and extragalactic point sources), but almost all share the property of being spectrally smooth and, when viewed through the chromatic response of an interferometer, occupy a signature "wedge" region in cylindrical k⊥k∥ Fourier space. The complement of the foreground wedge is termed the "EoR window" and is expected to be mostly foreground-free, allowing clean measurements of the power spectrum. This paper is a sequel to a previous paper that established a rigorous mathematical framework for describing the foreground wedge and the EoR window. Here, we use our framework to explore statistical methods by which the EoR window can be enlarged, thereby increasing the sensitivity of a power spectrum measurement. We adapt the Feldman-Kaiser-Peacock approximation (commonly used in galaxy surveys) for 21 cm cosmology and also compare the optimal quadratic estimator to simpler estimators that ignore covariances between different Fourier modes. The optimal quadratic estimator is found to suppress foregrounds by an extra factor of ˜105 in power at the peripheries of the EoR window, boosting the detection of the cosmological signal from 12σ to 50σ at the midpoint of reionization in our fiducial models. If numerical issues can be finessed, decorrelation techniques allow the EoR window to be further enlarged, enabling measurements to be made deep within the foreground wedge. These techniques do not assume that foreground is Gaussian distributed, and we additionally prove that a final round of foreground subtraction can be performed after decorrelation in a way that is guaranteed to have no cosmological signal loss.

  2. [CII] synthetic emission maps of simulated galactic disks

    NASA Astrophysics Data System (ADS)

    Franeck, A.; Walch, S.; Glover, S. C. O.; Seifried, D.; Girichidis, P.; Naab, T.; Klessen, R.; Peters, T.; Wünsch, R.; Gatto, A.; Clark, P. C.

    2016-05-01

    We carry out radiative transfer simulations for the [CII] emission of simulated galactic disks from the SILCC project.6 Here we present the integrated [CII] intensity map of a typical simulation which assumes solar neighbourhood conditions with ΣGAS = 10 M⊙/pc2 and a supernova rate of 15 SN/Myr with randomly distributed supernovae (SNe) at t = 50 Myr. We analyse the intensity profile which reveals different components. These are clearly distinguishable and trace cold, molecular as well as warm, outflowing gas. We find that [CII] is a promising tool to analyse the multi-phase structure of the ISM. SILCC: Simulating the LIfe Cycle of molecular Clouds: hera.ph1.uni-koeln.de/˜silcc/

  3. A model of the diffuse galactic gamma ray emission

    NASA Technical Reports Server (NTRS)

    Sreekumar, Parameswaran

    1990-01-01

    The galaxy was observed to be a source of high energy gamma rays as shown by the two successful satellite experiments, SAS-2 and COS-B. It is generally understood that these diffuse gamma rays result from interactions between energetic cosmic rays and interstellar gas. This work makes use of the most recent data on the distribution of atomic and molecular hydrogen in the galaxy along with new estimates of gamma ray production functions to model the diffuse galactic gamma ray emission. The model allows various spatial distributions for cosmic rays in the Galaxy including non-axisymmetric ones. In the light of the expected data from EGRET (Energetic Gamma-Ray Experiment Telescope), an improved model of cosmic ray-matter-gamma ray interaction will provide new insights into the distribution of cosmic rays and the strength of its coupling to matter.

  4. X-ray emission from active galactic nuclei

    NASA Technical Reports Server (NTRS)

    Mushotzky, R.

    1985-01-01

    It is often held that the X-ray emission from active galactic nuclei (AGN) arises from a region close to the central energy source. Thus X-ray observations may provide the best constraints on the central engine. In particular, the shape of the X-ray continuum gives information about the mechanism for photon generation, X-ray time variability data can constrain the size and mass of the continuum source, and X-ray occultation data give constraints on the relative sizes of the continuum source and the intervening absorbing material (often assumed to be the broad line clouds). In addition, since a fair fraction of the total energy of an AGN is emitted at X-ray wavelengths, direct measurement of the amount and spectral form of this radiation is important for modeling of the optically emitting clouds.

  5. Large proper motion of the Thorne-Żytkow object candidate HV 2112 reveals its likely nature as foreground Galactic S-star

    NASA Astrophysics Data System (ADS)

    Maccarone, Thomas J.; de Mink, Selma E.

    2016-05-01

    Using the Southern Proper Motion (SPM) catalogue, we show that the candidate Thorne-Żytkow object HV 2112 has a proper motion implying a space velocity of about 3000 {km} {s}^{-1}if the object is located at the distance of the Small Magellanic Cloud (SMC). The proper motion is statistically different from that of the SMC at approximately 4σ in SPM, although the result can drop to about 3σ significance by including the UCAC4 data and considering systematic uncertainties in addition to the statistical ones. Assuming the measurement is robust, this proper motion is sufficient to exclude its proposed membership of the SMC and to argue instead that it is likely to be a foreground star in the Milky Way halo. The smaller distance and therefore lower brightness argue against its proposed nature as a Thorne-Żytkow object (the hypothesized star-like object formed when a normal star and a neutron star merge) or a Asymptotic Giant Branch (AGB) star. Instead we propose a binary scenario where this star is the companion of a former massive AGB star, which polluted the object with via its stellar wind, i.e. a special case of an extrinsic S star. Our new scenario solves two additional problems with the two existing scenarios for its nature as Thorne-Żytkow object or present-day super AGB star. The puzzling high ratio of the strength of calcium to iron absorption lines is unexpected for SMC supergiants, but is fully consistent with the expectations for halo abundances. Secondly, its strong variability can now be explained naturally as a manifestation of the Mira phenomenon. We discuss further observational tests that could distinguish between the foreground and SMC scenarios in advance of the improved proper motion measurements likely to come from Gaia.

  6. The foreground wedge and 21-cm BAO surveys

    NASA Astrophysics Data System (ADS)

    Seo, Hee-Jong; Hirata, Christopher M.

    2016-03-01

    Redshifted H I 21 cm emission from unresolved low-redshift large-scale structure is a promising window for ground-based baryon acoustic oscillations (BAO) observations. A major challenge for this method is separating the cosmic signal from the foregrounds of Galactic and extra-Galactic origins that are stronger by many orders of magnitude than the former. The smooth frequency spectrum expected for the foregrounds would nominally contaminate only very small k∥ modes; however, the chromatic response of the telescope antenna pattern at this wavelength to the foreground introduces non-smooth structure, pervasively contaminating the cosmic signal over the physical scales of our interest. Such contamination defines a wedged volume in Fourier space around the transverse modes that is inaccessible for the cosmic signal. In this paper, we test the effect of this contaminated wedge on the future 21-cm BAO surveys using Fisher information matrix calculation. We include the signal improvement due to the BAO reconstruction technique that has been used for galaxy surveys and test the effect of this wedge on the BAO reconstruction as a function of signal to noises and incorporate the results in the Fisher matrix calculation. We find that the wedge effect expected at z = 1-2 is very detrimental to the angular diameter distances: the errors on angular diameter distances increased by 3-4.4 times, while the errors on H(z) increased by a factor of 1.5-1.6. We conclude that calibration techniques that clean out the foreground `wedge' would be extremely valuable for constraining angular diameter distances from intensity-mapping 21-cm surveys.

  7. SPIDER OPTIMIZATION. II. OPTICAL, MAGNETIC, AND FOREGROUND EFFECTS

    SciTech Connect

    O'Dea, D. T.; Clark, C. N.; Contaldi, C. R.; Ade, P. A. R.; Amiri, M.; Burger, B.; Davis, G.; Benton, S. J.; Bock, J. J.; Crill, B. P.; Dore, O.; Filippini, J. P.; Bond, J. R.; Farhang, M.; Bonetti, J. A.; Bryan, S.; Chiang, H. C.; Fraisse, A. A.; Fissel, L. M.; Gandilo, N. N.

    2011-09-01

    SPIDER is a balloon-borne instrument designed to map the polarization of the cosmic microwave background (CMB) with degree-scale resolution over a large fraction of the sky. SPIDER's main goal is to measure the amplitude of primordial gravitational waves through their imprint on the polarization of the CMB if the tensor-to-scalar ratio, r, is greater than 0.03. To achieve this goal, instrumental systematic errors must be controlled with unprecedented accuracy. Here, we build on previous work to use simulations of SPIDER observations to examine the impact of several systematic effects that have been characterized through testing and modeling of various instrument components. In particular, we investigate the impact of the non-ideal spectral response of the half-wave plates, coupling between focal-plane components and Earth's magnetic field, and beam mismatches and asymmetries. We also present a model of diffuse polarized foreground emission based on a three-dimensional model of the Galactic magnetic field and dust, and study the interaction of this foreground emission with our observation strategy and instrumental effects. We find that the expected level of foreground and systematic contamination is sufficiently low for SPIDER to achieve its science goals.

  8. FINGERPRINTS OF GALACTIC LOOP I ON THE COSMIC MICROWAVE BACKGROUND

    SciTech Connect

    Liu, Hao; Mertsch, Philipp

    2014-07-10

    We investigate possible imprints of galactic foreground structures such as the ''radio loops'' in the derived maps of the cosmic microwave background. Surprisingly, there is evidence for these not only at radio frequencies through their synchrotron radiation, but also at microwave frequencies where emission by dust dominates. This suggests the mechanism is magnetic dipole radiation from dust grains enriched by metallic iron or ferrimagnetic molecules. This new foreground we have identified is present at high galactic latitudes, and potentially dominates over the expected B-mode polarization signal due to primordial gravitational waves from inflation.

  9. Diffuse γ-ray emission from misaligned active galactic nuclei

    SciTech Connect

    Di Mauro, M.; Donato, F.; Calore, F.; Ajello, M.; Latronico, L.

    2014-01-10

    Active galactic nuclei (AGNs) with jets seen at small viewing angles are the most luminous and abundant objects in the γ-ray sky. AGNs with jets misaligned along the line of sight appear fainter in the sky but are more numerous than the brighter blazars. We calculate the diffuse γ-ray emission due to the population of misaligned AGNs (MAGNs) unresolved by the Large Area Telescope (LAT) on the Fermi Gamma-ray Space Telescope (Fermi). A correlation between the γ-ray luminosity and the radio-core luminosity is established and demonstrated to be physical by statistical tests, as well as compatible with upper limits based on Fermi-LAT data for a large sample of radio-loud MAGNs. We constrain the derived γ-ray luminosity function by means of the source-count distribution of the radio galaxies detected by the Fermi-LAT. We finally calculate the diffuse γ-ray flux due to the whole MAGN population. Our results demonstrate that MAGNs can contribute from 10% up to nearly the entire measured isotropic gamma-ray background. We evaluate a theoretical uncertainty on the flux of almost an order of magnitude.

  10. Galactic Diffuse Gamma Ray Emission Is Greater than 10 Gev

    NASA Technical Reports Server (NTRS)

    Hunter, Stanley D.; White, Nicholas E. (Technical Monitor)

    2000-01-01

    AGILE and Gamma-ray Large Area Telescope (GLAST) are the next high-energy gamma-ray telescopes to be flown in space. These instruments will have angular resolution about 5 times better than Energetic Gamma-Ray Experiment Telescope (EGRET) above 10 GeV and much larger field of view. The on-axis effective area of AGILE will be about half that of EGRET, whereas GLAST will have about 6 times greater effective area than EGRET. The capabilities of ground based very high-energy telescopes are also improving, e.g. Whipple, and new telescopes, e.g. Solar Tower Atmospheric Cerenkov Effect Experiment (STACEE), Cerenkov Low Energy Sampling and Timing Experiment (CELESTE), and Mars Advanced Greenhouse Integrated Complex (MAGIC) are expected to have low-energy thresholds and sensitivities that will overlap the GLAST sensitivity above approximately 10 GeV. In anticipation of the results from these new telescopes, our current understanding of the galactic diffuse gamma-ray emission, including the matter and cosmic ray distributions is reviewed. The outstanding questions are discussed and the potential of future observations with these new instruments to resolve these questions is examined.

  11. Diffuse γ-Ray Emission from Misaligned Active Galactic Nuclei

    NASA Astrophysics Data System (ADS)

    Di Mauro, M.; Calore, F.; Donato, F.; Ajello, M.; Latronico, L.

    2014-01-01

    Active galactic nuclei (AGNs) with jets seen at small viewing angles are the most luminous and abundant objects in the γ-ray sky. AGNs with jets misaligned along the line of sight appear fainter in the sky but are more numerous than the brighter blazars. We calculate the diffuse γ-ray emission due to the population of misaligned AGNs (MAGNs) unresolved by the Large Area Telescope (LAT) on the Fermi Gamma-ray Space Telescope (Fermi). A correlation between the γ-ray luminosity and the radio-core luminosity is established and demonstrated to be physical by statistical tests, as well as compatible with upper limits based on Fermi-LAT data for a large sample of radio-loud MAGNs. We constrain the derived γ-ray luminosity function by means of the source-count distribution of the radio galaxies detected by the Fermi-LAT. We finally calculate the diffuse γ-ray flux due to the whole MAGN population. Our results demonstrate that MAGNs can contribute from 10% up to nearly the entire measured isotropic gamma-ray background. We evaluate a theoretical uncertainty on the flux of almost an order of magnitude.

  12. Neutral Hydrogen Structures Trace Dust Polarization Angle: Implications for Cosmic Microwave Background Foregrounds

    NASA Astrophysics Data System (ADS)

    Clark, S. E.; Hill, J. Colin; Peek, J. E. G.; Putman, M. E.; Babler, B. L.

    2015-12-01

    Using high-resolution data from the Galactic Arecibo L-Band Feed Array HI (GALFA-Hi) survey, we show that linear structure in Galactic neutral hydrogen (Hi) correlates with the magnetic field orientation implied by Planck 353 GHz polarized dust emission. The structure of the neutral interstellar medium is more tightly coupled to the magnetic field than previously known. At high Galactic latitudes, where the Planck data are noise dominated, the Hi data provide an independent constraint on the Galactic magnetic field orientation, and hence the local dust polarization angle. We detect strong cross-correlations between template maps constructed from estimates of dust intensity combined with either Hi-derived angles, starlight polarization angles, or Planck 353 GHz angles. The Hi data thus provide a new tool in the search for inflationary gravitational wave B -mode polarization in the cosmic microwave background, which is currently limited by dust foreground contamination.

  13. Neutral Hydrogen Structures Trace Dust Polarization Angle: Implications for Cosmic Microwave Background Foregrounds.

    PubMed

    Clark, S E; Hill, J Colin; Peek, J E G; Putman, M E; Babler, B L

    2015-12-11

    Using high-resolution data from the Galactic Arecibo L-Band Feed Array HI (GALFA-Hi) survey, we show that linear structure in Galactic neutral hydrogen (Hi) correlates with the magnetic field orientation implied by Planck 353 GHz polarized dust emission. The structure of the neutral interstellar medium is more tightly coupled to the magnetic field than previously known. At high Galactic latitudes, where the Planck data are noise dominated, the Hi data provide an independent constraint on the Galactic magnetic field orientation, and hence the local dust polarization angle. We detect strong cross-correlations between template maps constructed from estimates of dust intensity combined with either Hi-derived angles, starlight polarization angles, or Planck 353 GHz angles. The Hi data thus provide a new tool in the search for inflationary gravitational wave B-mode polarization in the cosmic microwave background, which is currently limited by dust foreground contamination. PMID:26705622

  14. Spectral Diagnostics of Galactic and Stellar X-Ray Emission from Charge Exchange Recombination

    NASA Technical Reports Server (NTRS)

    Wargelin, B.

    2003-01-01

    The proposed research uses the electron beam ion trap at the Lawrence Livermore National Laboratory to study the X-ray emission from charge-exchange recombination of highly charged ions with neutral gases. The resulting data fill a void in the existing experimental and theoretical data and are needed to explain all or part of the observed X-ray emission from the Galactic Ridge, solar and stellar winds, the Galactic Center, supernova ejecta, and photoionized nebulae.

  15. A Three-coordinate System (Ecliptic, Galactic, ISMF) Spectral Analysis of Heliospheric ENA Emissions Using Cassini/INCA Measurements

    NASA Astrophysics Data System (ADS)

    Dialynas, K.; Krimigis, S. M.; Mitchell, D. G.; Roelof, E. C.; Decker, R. B.

    2013-11-01

    In the present study, we use all-sky energy-resolved energetic neutral atom (ENA) maps obtained by the Ion and Neutral CAmera (INCA) instrument on board Cassini that correspond to the time period from 2003 to 2009, in four discrete energy passbands (~5.4 to ~55 keV), to investigate the geometrical characteristics of the belt (a broad band of emission in the sky). The heliospheric ENA emissions are mapped in three different coordinate systems (ecliptic, Galactic, and interstellar magnetic field (ISMF)), and spectral analyses are performed to further examine the belt's possible energy dependence. Our conclusions are summarized as follows: (1) the high flux ENA belt identified in the energy range of 8-42 keV is moderately well organized in Galactic coordinates, as the ENA minima appear in the vicinity of the north and south Galactic poles; (2) using minimization criteria ( B · R ~ 0), the deviation of the ENA emissions from the equator is effectively minimized in a rotated frame, which we interpret as ISMF, where its north pole points toward 190° ecliptic longitude and 15° ecliptic latitude; (3) ENA spectra show a power-law form in energy that can be fitted with a single function presenting higher spectral slopes in the belt region and lower outside (3.4 < γ < 4.4); (4) the spectra are almost indistinguishable between the tail and the nose regions, i.e., no noticeable asymmetry is observed; (5) the consistency of the ENA distributions as a function of latitude among the different INCA channels indicates that the morphology of the belt (peak, width, and structure) is nearly energy independent from 8 keV to 30 keV (minor deviations start to appear at >35 keV) and (6) in the low count rate regions, the long-term ENA count rate profiles do not match the measured cosmic ray profiles, indicating that even the minimum ENA emissions detected by INCA are foreground ENAs.

  16. A three-coordinate system (ecliptic, galactic, ISMF) spectral analysis of heliospheric ENA emissions using CASSINI/INCA measurements

    SciTech Connect

    Dialynas, K.; Krimigis, S. M.; Mitchell, D. G.; Roelof, E. C.; Decker, R. B

    2013-11-20

    In the present study, we use all-sky energy-resolved energetic neutral atom (ENA) maps obtained by the Ion and Neutral CAmera (INCA) instrument on board Cassini that correspond to the time period from 2003 to 2009, in four discrete energy passbands (∼5.4 to ∼55 keV), to investigate the geometrical characteristics of the belt (a broad band of emission in the sky). The heliospheric ENA emissions are mapped in three different coordinate systems (ecliptic, Galactic, and interstellar magnetic field (ISMF)), and spectral analyses are performed to further examine the belt's possible energy dependence. Our conclusions are summarized as follows: (1) the high flux ENA belt identified in the energy range of 8-42 keV is moderately well organized in Galactic coordinates, as the ENA minima appear in the vicinity of the north and south Galactic poles; (2) using minimization criteria ( B · R ∼ 0), the deviation of the ENA emissions from the equator is effectively minimized in a rotated frame, which we interpret as ISMF, where its north pole points toward 190° ecliptic longitude and 15° ecliptic latitude; (3) ENA spectra show a power-law form in energy that can be fitted with a single function presenting higher spectral slopes in the belt region and lower outside (3.4 < γ < 4.4); (4) the spectra are almost indistinguishable between the tail and the nose regions, i.e., no noticeable asymmetry is observed; (5) the consistency of the ENA distributions as a function of latitude among the different INCA channels indicates that the morphology of the belt (peak, width, and structure) is nearly energy independent from 8 keV to 30 keV (minor deviations start to appear at >35 keV); and (6) in the low count rate regions, the long-term ENA count rate profiles do not match the measured cosmic ray profiles, indicating that even the minimum ENA emissions detected by INCA are foreground ENAs.

  17. Foreground Cleaning for Cosmic Microwave Background Polarimeters in the Presence of Instrumental Effects

    NASA Astrophysics Data System (ADS)

    Bao, Chaoyun

    The Cosmic Microwave Background (CMB) B-mode polarization signal offers a direct probe of inflation, a period of exponential expansion in the extreme early universe. The inflationary CMB B-mode polarization signal, however, is subject to the contamination of polarized galactic thermal dust foreground emission. A robust foreground cleaning method is essential for CMB polarimeters targeting the inflationary B-mode signal. In this thesis I present my work on developing foreground cleaning algorithms particularly in the presence of instrumental effects. One of the instrumental effects I focus on in this work is the frequency dependent polarization rotation effect such as the one caused by an achromatic half-wave plate (AHWP). As an example, I use the AHWP of the E and B Experiment (EBEX) in this work and study the relation between the frequency dependent rotation effect and the characteristic parameters of the AHWP. To address the effect of an AHWP while removing galactic dust foreground contamination, I developed two foreground cleaning algorithms: a simple method that assumes perfect knowledge of the AHWP and a few simplifying assumptions, and a more sophisticated algorithm based on maximum likelihood method. Based on simulation results, the maximum likelihood foreground cleaning algorithm can recover CMB B-mode signal without any bias in the presence of band shape uncertainty, frequency dependent rotation effect and instrumental noise with realistic measurement accuracy of instrumental parameters. In this thesis I also present my work on calculating the atmospheric loading in the millimeter wave regime for sub-orbital CMB experiments such as EBEX. Having a proper prediction of the atmospheric loading is an important input to detector designs for CMB experiments.

  18. Low Luminosity Cataclysmic Variables and Fe Emission Lines of Galactic Ridge X-ray Emission

    NASA Astrophysics Data System (ADS)

    Xu, Xiaojie; Wang, Q. Daniel

    2015-08-01

    Cataclysmic variables (CVs) has been proposed to be one of the main contributors of the Galactic Ridge X-ray Emission (GRXE). However, previous studies on the spectra of local CVs suggested that the I6.7keV/I7.0keV line intensity ratios of CVs are not consistent with that of GRXE. Utilizing the archival Suzaku observations on local CVs, we confirm that luminous local CVs like intermediate polars, symbiotic stars and polars have lower I6.7keV/I7.0keV values, thus are unable to explain the Fe emission line ratios of GRXE. On the other hand, dimmer CVs like dwarf novae (DNe) have I6.7keV/I7.0keV values consitent with that of GRXE. Given the potential huge population, DNe could be one of the main resources of GRXE Fe line emission.

  19. A FOREGROUND-CLEANED COSMIC MICROWAVE BACKGROUND MAP FROM NON-GAUSSIANITY MEASUREMENT

    SciTech Connect

    Saha, Rajib

    2011-10-01

    In this Letter, we present a new method to estimate a foreground-cleaned cosmic microwave background (CMB) map at a resolution of 1{sup 0} by minimizing the non-Gaussian properties of the cleaned map which arise dominantly due to diffuse foreground emission components from the Milky Way. We employ simple kurtosis statistic as the measure of non-Gaussian properties and perform a linear combination of five frequency maps provided by the Wilkinson Microwave Anisotropy Probe (WMAP) in its seven-year data release in such a way that the cleaned map has a minimum kurtosis which leads to a non-Gaussianity-minimized, foreground-cleaned CMB map. We validate the method by performing Monte Carlo simulations. To minimize any residual foreground contamination from the cleaned map we flag out the region near the galactic plane based upon results from simulations. Outside the masked region our new estimate of the CMB map matches well with the WMAP's Internal Linear Combination (ILC) map. A simple pseudo-C{sub l} -based CMB TT power spectrum derived from the non-Gaussianity minimized map reproduces the earlier results of WMAP's power spectrum. An important advantage of the method is that it does not introduce any negative bias in angular power spectrum in the low multipole regime, unlike usual ILC method. Comparing our results with the previously published results we argue that CMB results are robust with respect to specific foreground removal algorithms employed.

  20. Diffuse Galactic gamma-ray emission with H.E.S.S.

    NASA Astrophysics Data System (ADS)

    Abramowski, A.; Aharonian, F.; Ait Benkhali, F.; Akhperjanian, A. G.; Angüner, E. O.; Backes, M.; Balenderan, S.; Balzer, A.; Barnacka, A.; Becherini, Y.; Becker Tjus, J.; Berge, D.; Bernhard, S.; Bernlöhr, K.; Birsin, E.; Biteau, J.; Böttcher, M.; Boisson, C.; Bolmont, J.; Bordas, P.; Bregeon, J.; Brun, F.; Brun, P.; Bryan, M.; Bulik, T.; Carrigan, S.; Casanova, S.; Chadwick, P. M.; Chakraborty, N.; Chalme-Calvet, R.; Chaves, R. C. G.; Chrétien, M.; Colafrancesco, S.; Cologna, G.; Conrad, J.; Couturier, C.; Cui, Y.; Davids, I. D.; Degrange, B.; Deil, C.; deWilt, P.; Djannati-Ataï, A.; Domainko, W.; Donath, A.; Drury, L. O'C.; Dubus, G.; Dutson, K.; Dyks, J.; Dyrda, M.; Edwards, T.; Egberts, K.; Eger, P.; Espigat, P.; Farnier, C.; Fegan, S.; Feinstein, F.; Fernandes, M. V.; Fernandez, D.; Fiasson, A.; Fontaine, G.; Förster, A.; Füßling, M.; Gabici, S.; Gajdus, M.; Gallant, Y. A.; Garrigoux, T.; Giavitto, G.; Giebels, B.; Glicenstein, J. F.; Gottschall, D.; Grondin, M.-H.; Grudzińska, M.; Hadasch, D.; Häffner, S.; Hahn, J.; Harris, J.; Heinzelmann, G.; Henri, G.; Hermann, G.; Hervet, O.; Hillert, A.; Hinton, J. A.; Hofmann, W.; Hofverberg, P.; Holler, M.; Horns, D.; Ivascenko, A.; Jacholkowska, A.; Jahn, C.; Jamrozy, M.; Janiak, M.; Jankowsky, F.; Jung-Richardt, I.; Kastendieck, M. A.; Katarzyński, K.; Katz, U.; Kaufmann, S.; Khélifi, B.; Kieffer, M.; Klepser, S.; Klochkov, D.; Kluźniak, W.; Kolitzus, D.; Komin, Nu.; Kosack, K.; Krakau, S.; Krayzel, F.; Krüger, P. P.; Laffon, H.; Lamanna, G.; Lefaucheur, J.; Lefranc, V.; Lemière, A.; Lemoine-Goumard, M.; Lenain, J.-P.; Lohse, T.; Lopatin, A.; Lu, C.-C.; Marandon, V.; Marcowith, A.; Marx, R.; Maurin, G.; Maxted, N.; Mayer, M.; McComb, T. J. L.; Méhault, J.; Meintjes, P. J.; Menzler, U.; Meyer, M.; Mitchell, A. M. W.; Moderski, R.; Mohamed, M.; Morâ, K.; Moulin, E.; Murach, T.; de Naurois, M.; Niemiec, J.; Nolan, S. J.; Oakes, L.; Odaka, H.; Ohm, S.; Opitz, B.; Ostrowski, M.; Oya, I.; Panter, M.; Parsons, R. D.; Paz Arribas, M.; Pekeur, N. W.; Pelletier, G.; Petrucci, P.-O.; Peyaud, B.; Pita, S.; Poon, H.; Pühlhofer, G.; Punch, M.; Quirrenbach, A.; Raab, S.; Reichardt, I.; Reimer, A.; Reimer, O.; Renaud, M.; de los Reyes, R.; Rieger, F.; Romoli, C.; Rosier-Lees, S.; Rowell, G.; Rudak, B.; Rulten, C. B.; Sahakian, V.; Salek, D.; Sanchez, D. A.; Santangelo, A.; Schlickeiser, R.; Schüssler, F.; Schulz, A.; Schwanke, U.; Schwarzburg, S.; Schwemmer, S.; Sol, H.; Spanier, F.; Spengler, G.; Spies, F.; Stawarz, Ł.; Steenkamp, R.; Stegmann, C.; Stinzing, F.; Stycz, K.; Sushch, I.; Tavernet, J.-P.; Tavernier, T.; Taylor, A. M.; Terrier, R.; Tluczykont, M.; Trichard, C.; Valerius, K.; van Eldik, C.; van Soelen, B.; Vasileiadis, G.; Veh, J.; Venter, C.; Viana, A.; Vincent, P.; Vink, J.; Völk, H. J.; Volpe, F.; Vorster, M.; Vuillaume, T.; Wagner, S. J.; Wagner, P.; Wagner, R. M.; Ward, M.; Weidinger, M.; Weitzel, Q.; White, R.; Wierzcholska, A.; Willmann, P.; Wörnlein, A.; Wouters, D.; Yang, R.; Zabalza, V.; Zaborov, D.; Zacharias, M.; Zdziarski, A. A.; Zech, A.; Zechlin, H.-S.; Fukui, Y.; H. E. S. S. Collaboration

    2014-12-01

    Diffuse γ -ray emission is the most prominent observable signature of celestial cosmic-ray interactions at high energies. While already being investigated at GeV energies over several decades, assessments of diffuse γ -ray emission at TeV energies remain sparse. After completion of the systematic survey of the inner Galaxy, the H.E.S.S. experiment is in a prime position to observe large-scale diffuse emission at TeV energies. Data of the H.E.S.S. Galactic Plane Survey are investigated in regions off known γ -ray sources. Corresponding γ -ray flux measurements were made over an extensive grid of celestial locations. Longitudinal and latitudinal profiles of the observed γ -ray fluxes show characteristic excess emission not attributable to known γ -ray sources. For the first time large-scale γ -ray emission along the Galactic plane using imaging atmospheric Cherenkov telescopes has been observed. While the background subtraction technique limits the ability to recover modest variation on the scale of the H.E.S.S. field of view or larger, which is characteristic of the inverse Compton scatter-induced Galactic diffuse emission, contributions of neutral pion decay as well as emission from unresolved γ -ray sources can be recovered in the observed signal to a large fraction. Calculations show that the minimum γ -ray emission from π0 decay represents a significant contribution to the total signal. This detection is interpreted as a mix of diffuse Galactic γ -ray emission and unresolved sources.

  1. Herschel HIFI observations of the Sgr A +50 km s-1 Cloud. Deep searches for O2 in emission and foreground absorption

    NASA Astrophysics Data System (ADS)

    Sandqvist, Aa.; Larsson, B.; Hjalmarson, Å.; Encrenaz, P.; Gerin, M.; Goldsmith, P. F.; Lis, D. C.; Liseau, R.; Pagani, L.; Roueff, E.; Viti, S.

    2015-12-01

    Context. The Herschel Oxygen Project (HOP) is an open time key program, awarded 140 h of observing time to search for molecular oxygen (O2) in a number of interstellar sources. To date O2 has definitely been detected in only two sources, namely ρ Oph A and Orion, reflecting the extremely low abundance of O2 in the interstellar medium. Aims: One of the sources in the HOP program is the +50 km s-1 Cloud in the Sgr A Complex in the centre of the Milky Way. Its environment is unique in the Galaxy and this property is investigated to see if it is conducive to the presence of O2. Methods: The Herschel Heterodyne Instrument for the Far Infrared (HIFI) is used to search for the 487 and 774 GHz emission lines of O2. Results: No O2 emission is detected towards the Sgr A +50 km s-1 Cloud, but a number of strong emission lines of methanol (CH3OH) and absorption lines of chloronium (H2Cl+) are observed. Conclusions: A 3σ upper limit for the fractional abundance ratio of [O2]/[H2] in the Sgr A +50 km s-1 Cloud is found to be X(O2) ≤ 5 × 10-8. However, since we can find no other realistic molecular candidate than O2 itself, we very tentatively suggest that two weak absorption lines at 487.261 and 487.302 GHz may be caused by the 487 GHz line of O2 in two foreground spiral arm clouds. By considering that the absorption may only be apparent, the estimated upper limit to the O2 abundance of ≤ (10-20) × 10-6 in these foreground clouds is very high, as opposed to the upper limit in the Sgr A +50 km s-1 Cloud itself, but similar to what has been reached in recent chemical shock models for Orion. This abundance limit was determined also using Odin non-detection limits, and assumes that O2 fills the beam. If the absorption is due to a differential Herschel OFF-ON emission, the O2 fractional abundance may be of the order of ≈ (5-10) × 10-6. With the assumption of pure absorption by foreground clouds, the unreasonably high abundance of (1.4-2.8) × 10-4 was obtained. The

  2. Non-Gaussianity in the foreground-reduced CMB maps

    SciTech Connect

    Bernui, A.; Reboucas, M. J.

    2010-03-15

    A detection or nondetection of primordial non-Gaussianity by using the cosmic microwave background radiation (CMB) data is crucial not only to discriminate inflationary models but also to test alternative scenarios. Non-Gaussianity offers, therefore, a powerful probe of the physics of the primordial Universe. The extraction of primordial non-Gaussianity is a difficult enterprise since several effects of a nonprimordial nature can produce non-Gaussianity. Given the far-reaching consequences of such a non-Gaussianity for our understanding of the physics of the early Universe, it is important to employ a range of different statistical tools to quantify and/or constrain its amount in order to have information that may be helpful for identifying its causes. Moreover, different indicators can in principle provide information about distinct forms of non-Gaussianity that can be present in CMB data. Most of the Gaussianity analyses of CMB data have been performed by using part-sky frequency, where the mask is used to deal with the galactic diffuse foreground emission. However, full-sky map seems to be potentially more appropriate to test for Gaussianity of the CMB data. On the other hand, masks can induce bias in some non-Gaussianity analyses. Here we use two recent large-angle non-Gaussianity indicators, based on skewness and kurtosis of large-angle patches of CMB maps, to examine the question of non-Gaussianity in the available full-sky five-year and seven-year Wilkinson Microwave Anisotropy Probe (WMAP) maps. We show that these full-sky foreground-reduced maps present a significant deviation from Gaussianity of different levels, which vary with the foreground-reducing procedures. We also make a Gaussianity analysis of the foreground-reduced five-year and seven-year WMAP maps with a KQ75 mask, and compare with the similar analysis performed with the corresponding full-sky foreground-reduced maps. This comparison shows a significant reduction in the levels of non

  3. BFORE: The B-mode Foreground Experiment

    NASA Astrophysics Data System (ADS)

    Niemack, Michael D.; Ade, Peter; de Bernardis, Francesco; Boulanger, Francois; Bryan, Sean; Devlin, Mark; Dunkley, Joanna; Eales, Steve; Gomez, Haley; Groppi, Chris; Henderson, Shawn; Hillbrand, Seth; Hubmayr, Johannes; Mauskopf, Philip; McMahon, Jeff; Miville-Deschênes, Marc-Antoine; Pascale, Enzo; Pisano, Giampaolo; Novak, Giles; Scott, Douglas; Soler, Juan; Tucker, Carole

    2016-08-01

    The B-mode Foreground Experiment (BFORE) is a proposed NASA balloon project designed to make optimal use of the sub-orbital platform by concentrating on three dust foreground bands (270, 350, and 600 GHz) that complement ground-based cosmic microwave background (CMB) programs. BFORE will survey ˜ 1/4 of the sky with 1.7-3.7 arcminute resolution, enabling precise characterization of the Galactic dust that now limits constraints on inflation from CMB B-mode polarization measurements. In addition, BFORE's combination of frequency coverage, large survey area, and angular resolution enables science far beyond the critical goal of measuring foregrounds. BFORE will constrain the velocities of thousands of galaxy clusters, provide a new window on the cosmic infrared background, and probe magnetic fields in the interstellar medium. We review the BFORE science case, timeline, and instrument design, which is based on a compact off-axis telescope coupled to {>}10,000 superconducting detectors.

  4. BFORE: The B-mode Foreground Experiment

    NASA Astrophysics Data System (ADS)

    Niemack, Michael D.; Ade, Peter; de Bernardis, Francesco; Boulanger, Francois; Bryan, Sean; Devlin, Mark; Dunkley, Joanna; Eales, Steve; Gomez, Haley; Groppi, Chris; Henderson, Shawn; Hillbrand, Seth; Hubmayr, Johannes; Mauskopf, Philip; McMahon, Jeff; Miville-Deschênes, Marc-Antoine; Pascale, Enzo; Pisano, Giampaolo; Novak, Giles; Scott, Douglas; Soler, Juan; Tucker, Carole

    2015-12-01

    The B-mode Foreground Experiment (BFORE) is a proposed NASA balloon project designed to make optimal use of the sub-orbital platform by concentrating on three dust foreground bands (270, 350, and 600 GHz) that complement ground-based cosmic microwave background (CMB) programs. BFORE will survey ˜ 1/4 of the sky with 1.7-3.7 arcminute resolution, enabling precise characterization of the Galactic dust that now limits constraints on inflation from CMB B-mode polarization measurements. In addition, BFORE's combination of frequency coverage, large survey area, and angular resolution enables science far beyond the critical goal of measuring foregrounds. BFORE will constrain the velocities of thousands of galaxy clusters, provide a new window on the cosmic infrared background, and probe magnetic fields in the interstellar medium. We review the BFORE science case, timeline, and instrument design, which is based on a compact off-axis telescope coupled to {>}10,000 superconducting detectors.

  5. Polarized foreground removal at low radio frequencies using rotation measure synthesis: uncovering the signature of hydrogen reionization

    NASA Astrophysics Data System (ADS)

    Geil, Paul M.; Gaensler, B. M.; Wyithe, J. Stuart B.

    2011-11-01

    Measurement of redshifted 21-cm emission from neutral hydrogen promises to be the most effective method for studying the reionization history of hydrogen and, indirectly, the first galaxies. These studies will be limited not by raw sensitivity to the signal, but rather, by bright foreground radiation from Galactic and extragalactic radio sources and the Galactic continuum. In addition, leakage due to gain errors and non-ideal feeds conspire to further contaminate low-frequency radio observations. This leakage leads to a portion of the complex linear polarization signal finding its way into Stokes I, and inhibits the detection of the non-polarized cosmological signal from the epoch of reionization. In this work, we show that rotation measure synthesis can be used to recover the signature of cosmic hydrogen reionization in the presence of contamination by polarized foregrounds. To achieve this, we apply the rotation measure synthesis technique to the Stokes I component of a synthetic data cube containing Galactic foreground emission, the effect of instrumental polarization leakage and redshifted 21-cm emission by neutral hydrogen from the epoch of reionization. This produces an effective Stokes I Faraday dispersion function for each line of sight, from which instrumental polarization leakage can be fitted and subtracted. Our results show that it is possible to recover the signature of reionization in its late stages (z≈ 7) by way of the 21-cm power spectrum, as well as through tomographic imaging of ionized cavities in the intergalactic medium.

  6. Understanding Limitations in the Determination of the Diffuse Galactic Gamma-ray Emission

    SciTech Connect

    Moskalenko, Igor V.; Digel, S.W.; Porter, T.A.; Reimer, O.; Strong, A.W.; /Garching, Max Planck Inst., MPE

    2006-10-03

    We discuss uncertainties and possible sources of errors associated with the determination of the diffuse Galactic {gamma}-ray emission using the EGRET data. Most of the issues will be relevant also in the GLAST era. The focus here is on issues that impact evaluation of dark matter annihilation signals against the diffuse {gamma}-ray emission of the Milky Way.

  7. The origin of the diffuse galactic IR/submm emission: Revisited after IRAS

    NASA Technical Reports Server (NTRS)

    Cox, P.; Mezger, P. G.

    1987-01-01

    Balloon observations are compared with Infrared Astronomy Satellite observations. There was good agreement for the longitudinal profiles. However, the dust emission observed by IRAS, contrary to the balloon observations which show dust emission only within the absolute value of b is equal to or less than 3 degrees, extends all the way to the galactic pole. The model fits were repeated using more recent parameters for the distribution of interstellar matter in the galactic disk and central region. The IR luminosities are derived for the revised galactic distance scale of solar radius - 8.5 Kpc. A total IR luminosity of 1.2 E10 solar luminosity is obtained, which is about one third of the estimated stellar luminosity of the Galaxy. The dust emission spectrum lambdaI(sub lambda) attains it maximum at 100 microns. A secondary maximum in the dust emission spectrum occurs at 10 microns, which contains 15% of the total IR luminosity of the Galaxy. The galactic dust emission spectrum was compared with the dust emission spectra of external IRAS galaxies. The warm dust luminosity relates to the present OB star formation rate, while flux densities observed at longer submm wavelengths are dominated by cold dust emission and thus can be used to estimate gas masses.

  8. The Origin of the Hot Gas in the Galactic Halo: Testing Galactic Fountain Models' X-Ray Emission

    NASA Astrophysics Data System (ADS)

    Henley, David B.; Shelton, Robin L.; Kwak, Kyujin; Hill, Alex S.; Mac Low, Mordecai-Mark

    2015-02-01

    We test the X-ray emission predictions of galactic fountain models against XMM-Newton measurements of the emission from the Milky Way's hot halo. These measurements are from 110 sight lines, spanning the full range of Galactic longitudes. We find that a magnetohydrodynamical simulation of a supernova-driven interstellar medium, which features a flow of hot gas from the disk to the halo, reproduces the temperature but significantly underpredicts the 0.5-2.0 keV surface brightness of the halo (by two orders of magnitude, if we compare the median predicted and observed values). This is true for versions of the model with and without an interstellar magnetic field. We consider different reasons for the discrepancy between the model predictions and the observations. We find that taking into account overionization in cooled halo plasma, which could in principle boost the predicted X-ray emission, is unlikely in practice to bring the predictions in line with the observations. We also find that including thermal conduction, which would tend to increase the surface brightnesses of interfaces between hot and cold gas, would not overcome the surface brightness shortfall. However, charge exchange emission from such interfaces, not included in the current model, may be significant. The faintness of the model may also be due to the lack of cosmic ray driving, meaning that the model may underestimate the amount of material transported from the disk to the halo. In addition, an extended hot halo of accreted material may be important, by supplying hot electrons that could boost the emission of the material driven out from the disk. Additional model predictions are needed to test the relative importance of these processes in explaining the observed halo emission.

  9. Fermi large area telescope measurements of the diffuse gamma-ray emission at intermediate galactic latitudes.

    PubMed

    Abdo, A A; Ackermann, M; Ajello, M; Anderson, B; Atwood, W B; Axelsson, M; Baldini, L; Ballet, J; Barbiellini, G; Bastieri, D; Baughman, B M; Bechtol, K; Bellazzini, R; Berenji, B; Blandford, R D; Bloom, E D; Bonamente, E; Borgland, A W; Bregeon, J; Brez, A; Brigida, M; Bruel, P; Burnett, T H; Caliandro, G A; Cameron, R A; Caraveo, P A; Casandjian, J M; Cecchi, C; Charles, E; Chekhtman, A; Cheung, C C; Chiang, J; Ciprini, S; Claus, R; Cohen-Tanugi, J; Conrad, J; Dereli, H; Dermer, C D; de Angelis, A; de Palma, F; Digel, S W; Di Bernardo, G; Dormody, M; do Couto e Silva, E; Drell, P S; Dubois, R; Dumora, D; Edmonds, Y; Farnier, C; Favuzzi, C; Fegan, S J; Focke, W B; Frailis, M; Fukazawa, Y; Funk, S; Fusco, P; Gaggero, D; Gargano, F; Gehrels, N; Germani, S; Giebels, B; Giglietto, N; Giordano, F; Glanzman, T; Godfrey, G; Grenier, I A; Grondin, M-H; Grove, J E; Guillemot, L; Guiriec, S; Hanabata, Y; Harding, A K; Hayashida, M; Hays, E; Hughes, R E; Jóhannesson, G; Johnson, A S; Johnson, R P; Johnson, T J; Johnson, W N; Kamae, T; Katagiri, H; Kataoka, J; Kawai, N; Kerr, M; Knödlseder, J; Kocian, M L; Kuehn, F; Kuss, M; Lande, J; Latronico, L; Longo, F; Loparco, F; Lott, B; Lovellette, M N; Lubrano, P; Madejski, G M; Makeev, A; Mazziotta, M N; McConville, W; McEnery, J E; Meurer, C; Michelson, P F; Mitthumsiri, W; Mizuno, T; Moiseev, A A; Monte, C; Monzani, M E; Morselli, A; Moskalenko, I V; Murgia, S; Nolan, P L; Nuss, E; Ohsugi, T; Okumura, A; Omodei, N; Orlando, E; Ormes, J F; Paneque, D; Panetta, J H; Parent, D; Pelassa, V; Pepe, M; Pesce-Rollins, M; Piron, F; Porter, T A; Rainò, S; Rando, R; Razzano, M; Reimer, A; Reimer, O; Reposeur, T; Ritz, S; Rodriguez, A Y; Roth, M; Ryde, F; Sadrozinski, H F-W; Sanchez, D; Sander, A; Saz Parkinson, P M; Scargle, J D; Sellerholm, A; Sgrò, C; Smith, D A; Smith, P D; Spandre, G; Spinelli, P; Starck, J-L; Stecker, F W; Striani, E; Strickman, M S; Strong, A W; Suson, D J; Tajima, H; Takahashi, H; Tanaka, T; Thayer, J B; Thayer, J G; Thompson, D J; Tibaldo, L; Torres, D F; Tosti, G; Tramacere, A; Uchiyama, Y; Usher, T L; Vasileiou, V; Vilchez, N; Vitale, V; Waite, A P; Wang, P; Winer, B L; Wood, K S; Ylinen, T; Ziegler, M

    2009-12-18

    The diffuse galactic gamma-ray emission is produced by cosmic rays (CRs) interacting with the interstellar gas and radiation field. Measurements by the Energetic Gamma-Ray Experiment Telescope (EGRET) instrument on the Compton Gamma-Ray Observatory indicated excess gamma-ray emission greater, > or approximately equal to 1 GeV relative to diffuse galactic gamma-ray emission models consistent with directly measured CR spectra (the so-called "EGRET GeV excess"). The Large Area Telescope (LAT) instrument on the Fermi Gamma-Ray Space Telescope has measured the diffuse gamma-ray emission with improved sensitivity and resolution compared to EGRET. We report on LAT measurements for energies 100 MeV to 10 GeV and galactic latitudes 10 degrees < or = |b| < or = 20 degrees. The LAT spectrum for this region of the sky is well reproduced by a diffuse galactic gamma-ray emission model that is consistent with local CR spectra and inconsistent with the EGRET GeV excess. PMID:20366246

  10. Fermi Large Area Telescope Measurements of the Diffuse Gamma-Ray Emission at Intermediate Galactic Latitudes

    NASA Astrophysics Data System (ADS)

    Abdo, A. A.; Ackermann, M.; Ajello, M.; Anderson, B.; Atwood, W. B.; Axelsson, M.; Baldini, L.; Ballet, J.; Barbiellini, G.; Bastieri, D.; Baughman, B. M.; Bechtol, K.; Bellazzini, R.; Berenji, B.; Blandford, R. D.; Bloom, E. D.; Bonamente, E.; Borgland, A. W.; Bregeon, J.; Brez, A.; Brigida, M.; Bruel, P.; Burnett, T. H.; Caliandro, G. A.; Cameron, R. A.; Caraveo, P. A.; Casandjian, J. M.; Cecchi, C.; Charles, E.; Chekhtman, A.; Cheung, C. C.; Chiang, J.; Ciprini, S.; Claus, R.; Cohen-Tanugi, J.; Conrad, J.; Dereli, H.; Dermer, C. D.; de Angelis, A.; de Palma, F.; Digel, S. W.; di Bernardo, G.; Dormody, M.; Do Couto E Silva, E.; Drell, P. S.; Dubois, R.; Dumora, D.; Edmonds, Y.; Farnier, C.; Favuzzi, C.; Fegan, S. J.; Focke, W. B.; Frailis, M.; Fukazawa, Y.; Funk, S.; Fusco, P.; Gaggero, D.; Gargano, F.; Gehrels, N.; Germani, S.; Giebels, B.; Giglietto, N.; Giordano, F.; Glanzman, T.; Godfrey, G.; Grenier, I. A.; Grondin, M.-H.; Grove, J. E.; Guillemot, L.; Guiriec, S.; Hanabata, Y.; Harding, A. K.; Hayashida, M.; Hays, E.; Hughes, R. E.; Jóhannesson, G.; Johnson, A. S.; Johnson, R. P.; Johnson, T. J.; Johnson, W. N.; Kamae, T.; Katagiri, H.; Kataoka, J.; Kawai, N.; Kerr, M.; Knödlseder, J.; Kocian, M. L.; Kuehn, F.; Kuss, M.; Lande, J.; Latronico, L.; Longo, F.; Loparco, F.; Lott, B.; Lovellette, M. N.; Lubrano, P.; Madejski, G. M.; Makeev, A.; Mazziotta, M. N.; McConville, W.; McEnery, J. E.; Meurer, C.; Michelson, P. F.; Mitthumsiri, W.; Mizuno, T.; Moiseev, A. A.; Monte, C.; Monzani, M. E.; Morselli, A.; Moskalenko, I. V.; Murgia, S.; Nolan, P. L.; Nuss, E.; Ohsugi, T.; Okumura, A.; Omodei, N.; Orlando, E.; Ormes, J. F.; Paneque, D.; Panetta, J. H.; Parent, D.; Pelassa, V.; Pepe, M.; Pesce-Rollins, M.; Piron, F.; Porter, T. A.; Rainò, S.; Rando, R.; Razzano, M.; Reimer, A.; Reimer, O.; Reposeur, T.; Ritz, S.; Rodriguez, A. Y.; Roth, M.; Ryde, F.; Sadrozinski, H. F.-W.; Sanchez, D.; Sander, A.; Saz Parkinson, P. M.; Scargle, J. D.; Sellerholm, A.; Sgrò, C.; Smith, D. A.; Smith, P. D.; Spandre, G.; Spinelli, P.; Starck, J.-L.; Stecker, F. W.; Striani, E.; Strickman, M. S.; Strong, A. W.; Suson, D. J.; Tajima, H.; Takahashi, H.; Tanaka, T.; Thayer, J. B.; Thayer, J. G.; Thompson, D. J.; Tibaldo, L.; Torres, D. F.; Tosti, G.; Tramacere, A.; Uchiyama, Y.; Usher, T. L.; Vasileiou, V.; Vilchez, N.; Vitale, V.; Waite, A. P.; Wang, P.; Winer, B. L.; Wood, K. S.; Ylinen, T.; Ziegler, M.

    2009-12-01

    The diffuse galactic γ-ray emission is produced by cosmic rays (CRs) interacting with the interstellar gas and radiation field. Measurements by the Energetic Gamma-Ray Experiment Telescope (EGRET) instrument on the Compton Gamma-Ray Observatory indicated excess γ-ray emission ≳1GeV relative to diffuse galactic γ-ray emission models consistent with directly measured CR spectra (the so-called “EGRET GeV excess”). The Large Area Telescope (LAT) instrument on the Fermi Gamma-Ray Space Telescope has measured the diffuse γ-ray emission with improved sensitivity and resolution compared to EGRET. We report on LAT measurements for energies 100 MeV to 10 GeV and galactic latitudes 10°≤|b|≤20°. The LAT spectrum for this region of the sky is well reproduced by a diffuse galactic γ-ray emission model that is consistent with local CR spectra and inconsistent with the EGRET GeV excess.

  11. Fermi Large Area Telescope Measurements of the Diffuse Gamma-Ray Emission at Intermediate Galactic Latitudes

    SciTech Connect

    Abdo, A.A.; Ackermann, M.; Ajello, M.; Anderson, B.; Atwood, W.B.; Axelsson, M.; Baldini, L.; Ballet, J.; Barbiellini, G.; Bastieri, D.; Baughman, B.M.; Bechtol, K.; Bellazzini, R.; Berenji, B.; Blandford, R.D.; Bloom, E.D.; Bonamente, E.; Borgland, A.W.; Bregeon, J.; Brez, A.; Brigida, M.; /more authors..

    2012-04-11

    The diffuse galactic {gamma}-ray emission is produced by cosmic rays (CRs) interacting with the interstellar gas and radiation field. Measurements by the Energetic Gamma-Ray Experiment Telescope (EGRET) instrument on the Compton Gamma-Ray Observatory indicated excess {gamma}-ray emission {ge}1 GeV relative to diffuse galactic {gamma}-ray emission models consistent with directly measured CR spectra (the so-called 'EGRET GeV excess'). The Large Area Telescope (LAT) instrument on the Fermi Gamma-Ray Space Telescope has measured the diffuse {gamma}-ray emission with improved sensitivity and resolution compared to EGRET. We report on LAT measurements for energies 100 MeV to 10 GeV and galactic latitudes 10{sup o} {le} |b| {le} 20{sup o}. The LAT spectrum for this region of the sky is well reproduced by a diffuse galactic {gamma}-ray emission model that is consistent with local CR spectra and inconsistent with the EGRET GeV excess.

  12. Foreground Characterization for the Murchison Widefield Array Using the Jansky Very Large Array

    NASA Astrophysics Data System (ADS)

    Busch, Michael P.; Bowman, Judd D.; Kittiwisit, Piyanat; Jacobs, Danny

    2016-01-01

    One of the most compelling questions in astrophysics today is how the process of galaxy formation unfolded during the Epoch of Reionization (EoR). A new generation of radio telescopes, including the Murchison Widefield Array (MWA) and others, are attempting to capture the redshifted 21cm signal from neutral hydrogen during the EoR. Mapping the reionization of the intergalactic medium (IGM) is one of the core objectives of 21 cm observatories. A pressing concern of these observations is the bright foreground sources in the telescope's sidelobes outside the primary beam of the MWA. These sources, including AGN, radio galaxies and local Galactic sources, are numerous and difficult to deal with. These foreground contaminants are five orders of magnitude brighter than the redshifted 21 cm emission expected from the IGM during the EoR. The Jansky Very Large Array (JVLA) in New Mexico can provide sensitive characterization of these sources in the MWA's northern sidelobe. We observed 100 bright radio sources using the JVLA in P-band and characterized these sources by extracting the spectral fits and fluxes for each source. By creating a foreground model for these data, the MWA will be able to better subtract these sources from future EoR measurements. We report the current status of the creation of the foreground model.

  13. Limits on foreground subtraction from chromatic beam effects in global redshifted 21 cm measurements

    NASA Astrophysics Data System (ADS)

    Mozdzen, T. J.; Bowman, J. D.; Monsalve, R. A.; Rogers, A. E. E.

    2016-02-01

    Foreground subtraction in global redshifted 21 cm measurements is limited by frequency-dependent (chromatic) structure in antenna beam patterns. Chromatic beams couple angular structures in Galactic foreground emission to spectral structures that may not be removed by smooth functional forms. We report results for simulations based on two dipole antennas used by the Experiment to Detect the Global EoR Signature (EDGES). The residual levels in simulated foreground-subtracted spectra are found to differ substantially between the two antennas, suggesting that antenna design must be carefully considered. Residuals are also highly dependent on the right ascension and declination of the antenna pointing, with rms values differing by as much as a factor of 20 across pointings. For EDGES and other ground-based experiments with zenith pointing antennas, right ascension and declination correspond directly to the local sidereal time and the latitude of the deployment site, hence chromatic beam effects should be taken into account when selecting sites. We introduce the `blade' dipole antenna and show, via simulations, that it has better chromatic performance than the `fourpoint' antenna previously used for EDGES. The blade antenna yields 1-5 mK residuals across the entire sky after a 5-term polynomial is removed from simulated spectra, whereas the fourpoint antenna typically requires a 6-term polynomial for comparable residuals. For both antennas, the signal-to-noise ratio of recovered 21 cm input signals peaks for a 5-term polynomial foreground fit given realistic thermal noise levels.

  14. Asymmetric 511 keV Positron Annihilation Line Emission from the Inner Galactic Disk

    NASA Technical Reports Server (NTRS)

    Skinner, Gerry; Weidenspointner, Georg; Jean, Pierre; Knodlseder, Jurgen; Ballmoos, Perer von; Bignami, Giovanni; Diehl, Roland; Strong, Andrew; Cordier, Bertrand; Schanne, Stephane; Winkler, Christoph

    2008-01-01

    A recently reported asymmetry in the 511 keV gamma-ray line emission from the inner galactic disk is unexpected and mimics an equally unexpected one in the distribution of LMXBs seen at hard X-ray energies. A possible conclusion is that LMXBs are an important source of the positrons whose annihilation gives rise to the line. We will discuss these results, their statistical significance and that of any link between the two. The implication of any association between LMXBs and positrons for the strong annihilation radiation from the galactic bulge will be reviewed.

  15. Soft gamma-ray galactic ridge emission as unveiled by SPI aboard INTEGRAL

    SciTech Connect

    Knoedlseder, J.; Weidenspointner, G.; Jean, P.; Strong, A.; Diehl, R.; Cordier, B.; Schanne, S.

    2007-07-12

    The origin of the soft gamma-ray (200 keV - 1 MeV) galactic ridge emission is one of the long-standing mysteries in the field of high-energy astrophysics. Population studies at lower energies have shown that emission from accreting compact objects gradually recedes in this domain, leaving place to another source of gamma-ray emission that is characterised by a hard power-law spectrum extending from 100 keV up to 100 MeV The nature of this hard component has remained so far elusive, partly due to the lack of sufficiently sensitive imaging telescopes that would be able to unveil the spatial distribution of the emission. The SPI telescope aboard INTEGRAL allows now for the first time the simultaneous imaging of diffuse and point-like emission in the soft gamma-ray regime. We present here all-sky images of the soft gamma-ray continuum emission that clearly reveal the morphology of the different emission components. We discuss the implications of our results on the nature of underlying emission processes and we put our results in perspective of GLAST studies of diffuse galactic continuum emission.

  16. Emission from the Local Galactic Halo in the 1/4 keV Band

    NASA Astrophysics Data System (ADS)

    Juda, M.

    1994-12-01

    Pointed observations with the ROSAT PSPC toward clouds at high galactic latitude provide a unique opportunity to probe emission from the local galactic halo in the 1/4 keV band. I present data from five fields toward clouds at |b| > 60(deg) identified through their IRAS 100 microns emission, two in the north galactic hemisphere and three in the south. In four of the five fields significant shadows are detected (2 north, 2 south). The derivation of the brightness of the shadowed component depends strongly on the assumed location and amount of absorbing material. Scaling the IRAS 100 microns emission by 10(20) H atom cm(-2) /MJy sr(-1) and correcting for the difference from the observed average 21 cm derived column density, the implied brightness of the distant emitting component is the same for the two northern latitude fields at { ~ 1.2*E(-3) counts s(-1) arcmin(-2}) ; this brightness is lower than that seen in the direction of Draco (Burrows & Mendenhall 1991, Snowden et al. 1991) and higher than in Ursa Major (Snowden et al. 1994). The two southern fields also have the same derived distant brightness at nearly the same level as the northern fields, { ~ 1.0*E(-3) counts s(-1) arcmin(-2}) . Approximately 20% of this emission may be attributed to an extragalactic background (Hasinger et al. 1993). The remaining emission, { ~ 0.8*E(-3) counts s(-1) arcmin(-2}) , would be provided by the local galactic halo. If these x-rays arise from a collisionally excited plasma at a temperature of 10(6) K the required emission measure is { ~ 0.0033 cm(-6) pc}. Burrows & Mendenhall 1991, Nature, 351, 629. Hasinger et al. 1993, A&A, 275, 1. Snowden et al. 1991, Science, 252, 1529. Snowden et al. 1994, ApJ, 430, 601.

  17. [C ii] emission from galactic nuclei in the presence of X-rays

    NASA Astrophysics Data System (ADS)

    Langer, W. D.; Pineda, J. L.

    2015-08-01

    Context. The luminosity of [C ii] is used as a probe of the star formation rate in galaxies, but the correlation breaks down in some active galactic nuclei (AGNs). Models of the [C ii] emission from galactic nuclei do not include the influence of X-rays on the carbon ionization balance, which may be a factor in reducing the [C ii] luminosity. Aims: We aim to determine the properties of the ionized carbon and its distribution among highly ionized states in the interstellar gas in galactic nuclei under the influence of X-ray sources. We calculate the [C ii] luminosity in galactic nuclei under the influence of bright sources of soft X-rays. Methods: We solve the balance equation of the ionization states of carbon as a function of X-ray flux, electron, atomic hydrogen, and molecular hydrogen density. These are input to models of [C ii] emission from the interstellar medium (ISM) in galactic nuclei representing conditions in the Galactic central molecular zone and a higher density AGN model. The behavior of the [C ii] luminosity is calculated as a function of the X-ray luminosity. We also solve the distribution of the ionization states of oxygen and nitrogen in highly ionized regions. Results: We find that the dense warm ionized medium (WIM) and dense photon dominated regions (PDRs) dominate the [C ii] emission when no X-rays are present. The X-rays in galactic nuclei can affect strongly the C+ abundance in the WIM, converting some fraction to C2+ and higher ionization states and thus reducing its [C ii] luminosity. For an X-ray luminosity L(X-ray) ≳ 1043 erg s-1 the [C ii] luminosity can be suppressed by a factor of a few, and for very strong sources, L(X-ray) >1044 erg s-1 such as found for many AGNs, the [C ii] luminosity is significantly depressed. Comparison of the model with several extragalactic sources shows that the [C ii] to far-infrared ratio declines for L(X-ray) ≳ 1043 erg s-1, in reasonable agreement with our model. Conclusions: We conclude that X

  18. Galactic Emission in the Wilkinson Microwave Anisotropy Probe (WMAP) Maps

    NASA Technical Reports Server (NTRS)

    Bennett, Charles

    2003-01-01

    The Wilkinson Microwave Anisotropy Probe (WMAP) has mapped the full sky in five microwave frequency bands from 23 to 94 GHz with sub-degree angular resolution. While the primary goal of the mission is to measure the cosmic microwave background anisotropy, the data also provide a wealth of information about microwave emission from the Milky Way. We present full sky maps of the synchrotron, free-free, and dust emission obtained from the first-year data and comment on how these maps inform our understanding of the interstellar medium.

  19. Emission Regions in Galactic Nuclei: Photoionisation, Shocks or Starbursts?.

    NASA Astrophysics Data System (ADS)

    Dopita, M. A.; Kewley, L. J.; Sutherland, R. S.

    2000-11-01

    Since Baldwin, Phillips and Terlevich and Osterbrock and Veilleux popularise d their use, optical diagnostic plots have been used to attempt to distinguish between the various modes of excitation in nuclear emission regions of both active and normal galaxies. Recently, great progress has been made in gathering new observational data, and in building theoretical models to describe the results. We will review these results, and attempt to show what parameters of the nuclear emission regions can be unequivocally derived from optical and UV diagnostics, and point the way towards making further progress in this problem.

  20. BROADBAND SPECTRAL ANALYSIS OF THE GALACTIC RIDGE X-RAY EMISSION

    SciTech Connect

    Yuasa, Takayuki; Makishima, Kazuo; Nakazawa, Kazuhiro

    2012-07-10

    Detailed spectral analysis of the Galactic X-ray background emission, or the Galactic Ridge X-ray Emission (GRXE), is presented. To study the origin of the emission, broadband and high-quality GRXE spectra were produced from 18 pointing observations with Suzaku in the Galactic bulge region, with a total exposure of 1 Ms. The spectra were successfully fitted by a sum of two major spectral components: a spectral model of magnetic accreting white dwarfs with a mass of 0.66{sup +0.09}{sub -0.07} M{sub Sun} and a softer optically thin thermal emission with a plasma temperature of 1.2-1.5 keV that is attributable to coronal X-ray sources. When combined with previous studies that employed high spatial resolution of the Chandra satellite, the present spectroscopic result gives stronger support to the scenario that the GRXE is essentially an assembly of numerous discrete faint X-ray stars. The detected GRXE flux in the hard X-ray band was used to estimate the number density of the unresolved hard X-ray sources. When integrated over a luminosity range of {approx}10{sup 30}-10{sup 34} erg s{sup -1}, the result is consistent with a value that was reported previously by directly resolving faint point sources.

  1. CO J = 2-1 EMISSION FROM EVOLVED STARS IN THE GALACTIC BULGE

    SciTech Connect

    Sargent, Benjamin A.; Meixner, M.; Patel, N. A.; Otsuka, M.; Srinivasan, S.; Riebel, D.

    2013-03-01

    We observe a sample of eight evolved stars in the Galactic bulge in the CO J = 2-1 line using the Submillimeter Array with angular resolution of 1''-4''. These stars have been detected previously at infrared wavelengths, and several of them have OH maser emission. We detect CO J = 2-1 emission from three of the sources in the sample: OH 359.943 +0.260, [SLO2003] A12, and [SLO2003] A51. We do not detect the remaining five stars in the sample because of heavy contamination from the galactic CO emission. Combining CO data with observations at infrared wavelengths constraining dust mass loss from these stars, we determine the gas-to-dust ratios of the Galactic bulge stars for which CO emission is detected. For OH 359.943 +0.260, we determine a gas mass-loss rate of 7.9 ({+-}2.2) Multiplication-Sign 10{sup -5} M {sub Sun} yr{sup -1} and a gas-to-dust ratio of 310 ({+-}89). For [SLO2003] A12, we find a gas mass-loss rate of 5.4 ({+-}2.8) Multiplication-Sign 10{sup -5} M {sub Sun} yr{sup -1} and a gas-to-dust ratio of 220 ({+-}110). For [SLO2003] A51, we find a gas mass-loss rate of 3.4 ({+-}3.0) Multiplication-Sign 10{sup -5} M {sub Sun} yr{sup -1} and a gas-to-dust ratio of 160 ({+-}140), reflecting the low quality of our tentative detection of the CO J = 2-1 emission from A51. We find that the CO J = 2-1 detections of OH/IR stars in the Galactic bulge require lower average CO J = 2-1 backgrounds.

  2. A High Fraction of Double-peaked Narrow Emission Lines in Powerful Active Galactic Nuclei

    NASA Astrophysics Data System (ADS)

    Lyu, Yang; Liu, Xin

    2016-08-01

    One percent of redshift z ˜ 0.1 Active Galactic Nuclei (AGNs) show velocity splitting of a few hundred km s-1 in the narrow emission lines in spatially integrated spectra. Such line profiles have been found to arise from the bulk motion of ionized gas clouds associated with galactic-scale outflows, merging pairs of galaxies each harboring a supermassive black hole (SMBH), and/or galactic-scale disk rotation. It remains unclear, however, how the frequency of narrow-line velocity splitting may depend on AGN luminosity. Here we study the correlation between the fraction of Type 2 AGNs with double-peaked narrow emission lines and AGN luminosity as indicated by [O III]λ5007 emission-line luminosity L[O III]. We combine the sample of Liu et al. (2010a) at z ˜ 0.1 with a new sample of 178 Type 2 AGNs with double-peaked [O III] emission lines at z ˜ 0.5. We select the new sample from a parent sample of 2089 Type 2 AGNs from the SDSS-III/Baryon Oscillation Spectroscopic Survey. We find a statistically significant (˜4.2σ) correlation between L[O III] and the fraction of objects that exhibit double-peaked narrow emission lines among all Type 2 AGNs, corrected for selection bias and incompleteness due to [O III] line width, equivalent width, splitting velocity, and/or equivalent width ratio between the two velocity components. Our result suggests that galactic-scale outflows and/or merging pairs of SMBHs are more prevalent in more powerful AGNs, although spatially resolved follow up observations are needed to resolve the origin(s) for the narrow-line velocity splitting for individual AGNs.

  3. Phenomenology of Broad Emission Lines in Active Galactic Nuclei

    NASA Astrophysics Data System (ADS)

    Sulentic, J. W.; Marziani, P.; Dultzin-Hacyan, D.

    Broad emission lines hold fundamental clues about the kinematics and structure of the central regions in AGN. In this article we review the most robust line profile properties and correlations emerging from the best data available. We identify fundamental differences between the profiles of radio-quiet and radio-loud sources as well as differences between the high- and low-ionization lines, especially in the radio-quiet majority of AGN. An Eigenvector 1 correlation space involving FWHM Hβ, W(FeIIopt)/W(Hβ), and the soft X-ray spectral index provides optimal discrimination between all principal AGN types (from narrow-line Seyfert 1 to radio galaxies). Both optical and radio continuum luminosities appear to be uncorrelated with the E1 parameters. We identify two populations of radio-quiet AGN: Population A sources (with FWHM(Hβ) <~ 4000 km s-1, generally strong FeII emission and a soft X-ray excess) show almost no parameter space overlap with radio-loud sources. Population B shows optical properties largely indistinguishable from radio-loud sources, including usually weak FeII emission, FWHM(Hβ) >~ 4000 km s-1 and lack of a soft X-ray excess. There is growing evidence that a fundamental parameter underlying Eigenvector 1 may be the luminosity-to-mass ratio of the active nucleus (L/M), with source orientation playing a concomitant role.

  4. Characterizing foreground for redshifted 21 cm radiation: 150 MHz Giant Metrewave Radio Telescope observations

    NASA Astrophysics Data System (ADS)

    Ghosh, Abhik; Prasad, Jayanti; Bharadwaj, Somnath; Ali, Sk. Saiyad; Chengalur, Jayaram N.

    2012-11-01

    Foreground removal is a major challenge for detecting the redshifted 21 cm neutral hydrogen (H I) signal from the Epoch of Reionization. We have used 150 MHz Giant Metrewave Radio Telescope observations to characterize the statistical properties of the foregrounds in four different fields of view. The measured multifrequency angular power spectrum Cℓ(Δν) is found to have values in the range 104-2 × 104 mK2 across 700 ≤ ℓ ≤ 2 × 104 and Δν ≤ 2.5 MHz, which is consistent with model predictions where point sources are the most dominant foreground component. The measured Cℓ(Δν) does not show a smooth Δν dependence, which poses a severe difficulty for foreground removal using polynomial fitting. The observational data were used to assess point source subtraction. Considering the brightest source (˜1 Jy) in each field, we find that the residual artefacts are less than 1.5 per cent in the most sensitive field (FIELD I). Considering all the sources in the fields, we find that the bulk of the image is free of artefacts, the artefacts being localized to the vicinity of the brightest sources. We have used FIELD I, which has an rms noise of 1.3 mJy beam-1, to study the properties of the radio source population to a limiting flux of 9 mJy. The differential source count is well fitted with a single power law of slope -1.6. We find there is no evidence for flattening of the source counts towards lower flux densities which suggests that source population is dominated by the classical radio-loud active galactic nucleus. The diffuse Galactic emission is revealed after the point sources are subtracted out from FIELD I. We find Cℓ ∝ ℓ-2.34 for 253 ≤ ℓ ≤ 800 which is characteristic of the Galactic synchrotron radiation measured at higher frequencies and larger angular scales. We estimate the fluctuations in the Galactic synchrotron emission to be ℓ(ℓ+1)Cℓ/2π≃10 K at ℓ = 800 (θ > 10 arcmin). The measured Cℓ is dominated by

  5. Residual foreground contamination in the WMAP data and bias in non-Gaussianity estimation

    SciTech Connect

    Chingangbam, Pravabati; Park, Changbom E-mail: cbp@kias.re.kr

    2013-02-01

    We analyze whether there is any residual foreground contamination in the cleaned WMAP 7 years data for the differential assemblies, Q, V and W. We calculate the correlation between the foreground map, from which long wavelength correlations have been subtracted, and the foreground reduced map for each differential assembly after applying the Galaxy and point sources masks. We find positive correlations for all the differential assemblies, with high statistical significance. For Q and V, we find that a large fraction of the contamination comes from pixels where the foreground maps have positive values larger than three times the rms values. These findings imply the presence of residual contamination from Galactic emissions and unresolved point sources. We redo the analysis after masking the extended point sources cataloque of Scodeller et al. [7] and find a drop in the correlation and corresponding significance values. To quantify the effect of the residual contamination on the search for primordial non-Gaussianity in the CMB we add estimated contaminant fraction to simulated Gaussian CMB maps and calculate the characteristic non-Gaussian deviation shapes of Minkowski Functionals that arise due to the contamination. We find remarkable agreement of these deviation shapes with those measured from WMAP data, which imply that a major fraction of the observed non-Gaussian deviation comes from residual foreground contamination. We also compute non-Gaussian deviations of Minkowski Functionals after applying the point sources mask of Scodeller et al. and find a decrease in the overall amplitudes of the deviations which is consistent with a decrease in the level of contamination.

  6. 26Al Emission Structure Along the Galactic Plane

    NASA Technical Reports Server (NTRS)

    Purcell, William R.

    1996-01-01

    During the grant period (February 1995 - February 1996), the NU team members worked to analyze the available data. Results of this analysis were presented at the 24(th) international Cosmic Ray Conference held in Rome, Italy, August 28 - September 8, 1995, and at the 1996 meeting of the AAS/High Energy Astrophysics Division held in San Diego, California, April 30 - May 3, 1996. The results were also published in the conference proceedings of the Cosmic Ray Conference. As a result of this work, subsequent proposals have been submitted to continue this effort and to develop enhanced capabilities for OSSE observations of high energy emission.

  7. IFU spectroscopy of 10 early-type galactic nuclei - II. Nuclear emission line properties

    NASA Astrophysics Data System (ADS)

    Ricci, T. V.; Steiner, J. E.; Menezes, R. B.

    2014-05-01

    Although it is well known that massive galaxies have central black holes, most of them accreting at low Eddington ratios, many important questions still remain open. Among them are the nature of the ionizing source, the characteristics and frequencies of the broad-line region and of the dusty torus. We report observations of 10 early-type galactic nuclei, observed with the Gemini Multi Object Spectrograph in integral field unit mode, installed on the Gemini South telescope, analysed with standard techniques for spectral treatment and compared with results obtained with principal component analysis Tomography (Paper I). We performed spectral synthesis of each spaxel of the data cubes and subtracted the stellar component from the original cube, leaving a data cube with emission lines only. The emission lines were decomposed in multi-Gaussian components. We show here that, for eight galaxies previously known to have emission lines, the narrow-line region can be decomposed in two components with distinct line widths. In addition to this, broad Hα emission was detected in six galaxies. The two galaxies not previously known to have emission lines show weak Hα+[N II] lines. All 10 galaxies may be classified as low-ionization nuclear emission regions in diagnostic diagrams and seven of them have bona fide active galactic nuclei with luminosities between 1040 and 1043 erg s-1. Eddington ratios are always <10-3.

  8. Spectral Diagnostics of Galactic and Stellar X-Ray Emission from Charge Exchange Recombination

    NASA Technical Reports Server (NTRS)

    Wargelin, B.

    2002-01-01

    The proposed research uses the electron beam ion trap at the Lawrence Livermore National Laboratory (LLNL) to study X-ray emission from charge-exchange recombination of highly charged ions with neutral gases. The resulting data fill a void in existing experimental and theoretical understanding of this atomic physics process, and are needed to explain all or part of the observed X-ray emission from the soft X-ray background, stellar winds, the Galactic Center, supernova ejecta, and photoionized nebulae. Progress made during the first year of the grant is described, as is work planned for the second year.

  9. Evidence for TeV Gamma-Ray Emission from a Region of the Galactic Plane

    SciTech Connect

    Atkins, R.; Gonzalez, M.M.; McEnery, J.E.; Wilson, M.E.; Benbow, W.; Coyne, D.G.; Dorfan, D.E.; Kelley, L.A.; Morales, M.F.; Parkinson, P.M. Saz; Williams, D.A.; Berley, D.; Blaufuss, E.; DeYoung, T.; Goodman, J.A.; Hays, E.; Lansdell, C.P.; Noyes, D.; Smith, A.J.; Sullivan, G.W.

    2005-12-16

    Gamma-ray emission from a narrow band at the galactic equator has previously been detected up to 30 GeV. We report evidence for a TeV gamma-ray signal from a region of the galactic plane by Milagro, a large-field-of-view water Cherenkov detector for extensive air showers. An excess with a significance of 4.5 standard deviations has been observed from the region of galactic longitude l (set-membership sign) (40 deg.,100 deg.) and latitude vertical bar b vertical bar <5 deg. Under the assumption of a simple power law spectrum, with no cutoff in the EGRET-Milagro energy range, the measured integral flux is {phi}{sub {gamma}}(>3.5 TeV)=(6.4{+-}1.4{+-}2.1)x10{sup -11} cm{sup -2} s{sup -1} sr{sup -1}. This flux is consistent with an extrapolation of the EGRET spectrum between 1 and 30 GeV in this galactic region.

  10. CO Line Emission from Compact Nuclear Starburst Disks around Active Galactic Nuclei

    NASA Astrophysics Data System (ADS)

    Armour, J. N.; Ballantyne, D. R.

    2012-06-01

    There is substantial evidence for a connection between star formation in the nuclear region of a galaxy and growth of the central supermassive black hole. Furthermore, starburst activity in the region around an active galactic nucleus (AGN) may provide the obscuration required by the unified model of AGNs. Molecular line emission is one of the best observational avenues to detect and characterize dense, star-forming gas in galactic nuclei over a range of redshift. This paper presents predictions for the carbon monoxide (CO) line features from models of nuclear starburst disks around AGNs. These small-scale (lsim 100 pc), dense and hot starbursts have CO luminosities similar to scaled-down ultra-luminous infrared galaxies and quasar host galaxies. Nuclear starburst disks that exhibit a pc-scale starburst and could potentially act as the obscuring torus show more efficient CO excitation and higher brightness temperature ratios than those without such a compact starburst. In addition, the compact starburst models predict strong absorption when J Upper >~ 10, a unique observational signature of these objects. These findings allow for the possibility that CO spectral line energy distributions (SLEDs) could be used to determine if starburst disks are responsible for the obscuration in z <~ 1 AGNs. Directly isolating the nuclear CO line emission of such compact regions around AGNs from galactic-scale emission will require high-resolution imaging or selecting AGN host galaxies with weak galactic-scale star formation. Stacking individual CO SLEDs will also be useful in detecting the predicted high-J features.

  11. TRIS. III. The Diffuse Galactic Radio Emission at δ = +42°

    NASA Astrophysics Data System (ADS)

    Tartari, A.; Zannoni, M.; Gervasi, M.; Boella, G.; Sironi, G.

    2008-11-01

    We present values of temperature and spectral index of the Galactic diffuse radiation measured at 600 and 820 MHz along a 24h right ascension circle at declination δ = + 42°. They have been obtained from a subset of absolute measurements of the sky temperature made with TRIS, an experiment devoted to the measurement of the CMB temperature at decimetric wavelengths with an angular resolution of about 20°. Our analysis confirms the preexisting picture of the Galactic diffuse emission at decimetric wavelength and improves the accuracy of the measurable quantities. In particular, the signal coming from the halo has a spectral index in the range 2.9-3.1 above 600 MHz, depending on the sky position. In the disk, at TRIS angular resolution, the free-free emission accounts for the 11% of the overall signal at 600 MHz and 21% at 1420 MHz. The polarized component of the Galactic emission, evaluated from the survey by Brouw and Spoelstra, affects the observations at TRIS angular resolution by less than 3% at 820 MHz and less than 2% at 600 MHz. Within the uncertainties, our determination of the Galactic spectral index is practically unaffected by the correction for polarization. Since the overall error budget of the sky temperatures measured by TRIS at 600 MHz, that is, 66 (systematic) + 18 (statistical) mK, is definitely smaller than those reported in previous measurements at the same frequency, our data have been used to discuss the zero levels of the sky maps at 150, 408, 820, and 1420 MHz in literature. Concerning the 408 MHz survey, limiting our attention to the patch of sky corresponding to the region observed by TRIS, we suggest a correction of the base level of +3.9 +/- 0.6 K.

  12. The contribution of CHONS particles to the diffuse high-Galactic-latitude IR emission

    NASA Astrophysics Data System (ADS)

    Papoular, R.

    2014-05-01

    This work purports to model the far-infrared grey-body emission in the spectra of high-Galactic-latitude clouds. Several carbonaceous laboratory materials are tested for their fitness as carriers of this modified blackbody emission which, according to data delivered by the Planck satellite, and others before, is best fitted with temperature 17.9 K and spectral index β = 1.78. Some of these materials were discarded for insufficient emissivity, others for inadequate β. By contrast, CHONS clusters (β = 1.4, T = 19 K) combine nicely with magnesium silicate (β = 2, T = 18.7 K) to give a spectrum which falls well within the observational error bars (total emission cross-section at 250 μm: 8.6 × 10-26 cm2 per H atom). Only 15 per cent of all Galactic carbon atoms are needed for this purpose. The CHONS particles that were considered and described have a disordered (amorphous) structure but include a sizeable fraction of aromatic rings, although they are much less graphitized than a-C:H/hydrogenated amorphous carbon. They can be seen as one embodiment of `astronomical graphite' deduced earlier on from the then available astronomical observations. Grain heating by H atom capture is proposed as a contributor to the observed residual emissions that do not follow the dust/H I correlation.

  13. THE MORPHOLOGY OF HADRONIC EMISSION MODELS FOR THE GAMMA-RAY SOURCE AT THE GALACTIC CENTER

    SciTech Connect

    Linden, Tim; Profumo, Stefano; Lovegrove, Elizabeth

    2012-07-01

    Recently, detections of a high-energy {gamma}-ray source at the position of the Galactic center have been reported by multiple {gamma}-ray telescopes, spanning the energy range between 100 MeV and 100 TeV. Analysis of these signals strongly suggests the TeV emission to have a morphology consistent with a point source up to the angular resolution of the HESS telescope (approximately 3 pc), while the point-source nature of the GeV emission is currently unsettled, with indications that it may be spatially extended. In the case that the emission is hadronic and in a steady state, we show that the expected {gamma}-ray morphology is dominated by the distribution of target gas, rather than by details of cosmic-ray injection and propagation. Specifically, we expect a significant portion of hadronic emission to coincide with the position of the circumnuclear ring, which resides between 1 and 3 pc from the Galactic center. We note that the upcoming Cherenkov Telescope Array (CTA) will be able to observe conclusive correlations between the morphology of the TeV {gamma}-ray source and the observed gas density, convincingly confirming or ruling out a hadronic origin for the {gamma}-ray emission.

  14. CARMA observations of Galactic cold cores: searching for spinning dust emission

    NASA Astrophysics Data System (ADS)

    Tibbs, C. T.; Paladini, R.; Cleary, K.; Muchovej, S. J. C.; Scaife, A. M. M.; Stevenson, M. A.; Laureijs, R. J.; Ysard, N.; Grainge, K. J. B.; Perrott, Y. C.; Rumsey, C.; Villadsen, J.

    2015-11-01

    We present the first search for spinning dust emission from a sample of 34 Galactic cold cores, performed using the CARMA interferometer. For each of our cores, we use photometric data from the Herschel Space Observatory to constrain bar{N}H, bar{T}d, bar{n}H, and bar{G}0. By computing the mass of the cores and comparing it to the Bonnor-Ebert mass, we determined that 29 of the 34 cores are gravitationally unstable and undergoing collapse. In fact, we found that six cores are associated with at least one young stellar object, suggestive of their protostellar nature. By investigating the physical conditions within each core, we can shed light on the cm emission revealed (or not) by our CARMA observations. Indeed, we find that only three of our cores have any significant detectable cm emission. Using a spinning dust model, we predict the expected level of spinning dust emission in each core and find that for all 34 cores, the predicted level of emission is larger than the observed cm emission constrained by the CARMA observations. Moreover, even in the cores for which we do detect cm emission, we cannot, at this stage, discriminate between free-free emission from young stellar objects and spinning dust emission. We emphasize that although the CARMA observations described in this analysis place important constraints on the presence of spinning dust in cold, dense environments, the source sample targeted by these observations is not statistically representative of the entire population of Galactic cores.

  15. The effect of foreground mitigation strategy on EoR window recovery

    NASA Astrophysics Data System (ADS)

    Chapman, Emma; Zaroubi, Saleem; Abdalla, Filipe B.; Dulwich, Fred; Jelić, Vibor; Mort, Benjamin

    2016-05-01

    The removal of the Galactic and extragalactic foregrounds remains a major challenge for those wishing to make a detection of the Epoch of Reionization (EoR) 21 cm signal. Multiple methods of modelling these foregrounds with varying levels of assumption have been trialled and shown promising recoveries on simulated data. Recently however there has been increased discussion of using the expected shape of the foregrounds in Fourier space to define an EoR window free of foreground contamination. By carrying out analysis within this window only, one can avoid the foregrounds and any statistical bias they might introduce by instead removing these foregrounds. In this paper, we discuss the advantages and disadvantages of both foreground removal and foreground avoidance. We create a series of simulations with noise levels in line with both current and future experiments and compare the recovered statistical cosmological signal from foreground avoidance and a simplified, frequency independent foreground removal model. We find that for current generation experiments, while foreground avoidance enables a better recovery at kperp > 0.6 Mpc-1, foreground removal is able to recover significantly more signal at small klos for both current and future experiments. We also relax the assumption that the foregrounds are smooth. For line-of-sight variations only, foreground removal is able to make a good signal recovery even at 1 per cent while foreground avoidance is compromised significantly. We find that both methods perform well for foreground models with line-of-sight and spatial variations around 0.1 per cent however at levels larger than this both methods are compromised.

  16. SMA Observations of CO J=2-1 Emission from Evolved Stars in the Galactic Bulge

    NASA Astrophysics Data System (ADS)

    Sargent, Benjamin A.; Patel, N. A.; Meixner, M.; Otsuka, M.; Riebel, D.; Srinivasan, S.

    2013-01-01

    Asymptotic Giant Branch (AGB) stars are in the final stages of their lives, in which they eject mass. The dust grains formed in these mass outflows experience radiation pressure from the star and push the gas in the star's outflow away with the dust. There is much infrared data available to determine AGB dust mass loss in, e.g., the Milky Way and the Magellanic Clouds (e.g., the Surveying the Agents of a Galaxy's Evolution Spitzer Space Telescope Legacy project; PI: M. Meixner). However, the dependence of gas-to-dust ratios on metallicity for AGB stars, of use in determining total mass loss rates from optical and infrared observations constraining dust mass loss rates, is not well known. To remedy this, we present results from our 1.3 mm Submillimeter Array observations of 8 evolved stars in the inner Galactic Bulge (about 8 kpc distant). The metallicities of these OH/IR and AGB stars have been measured by others. We detect CO J=2-1 emission from OH 359.943+0.260. We possibly detect CO J=2-1 emission from [SLO2003] A12, though this detection is heavily contaminated by surrounding extended emission. We do not detect CO J=2-1 emission from the rest of our sample. Combining these CO data and analysis with observations at infrared wavelengths constraining dust mass loss, we determine the gas-to-dust ratios of Galactic Bulge stars for which CO emission is detected, determining a value of 320 for OH 359.943+0.260 and an upper limit of < 260 for [SLO2003] A12. We discuss applications of this work to studies of mass loss from evolved stars elsewhere, such as AGB stars in the Magellanic Clouds. We also discuss prospects for future CO observations of OH/IR and AGB stars in the Galactic Bulge.

  17. RELATIVISTIC BROADENING OF IRON EMISSION LINES IN A SAMPLE OF ACTIVE GALACTIC NUCLEI

    SciTech Connect

    Brenneman, Laura W.; Reynolds, Christopher S.

    2009-09-10

    We present a uniform X-ray spectral analysis of eight type-1 active galactic nuclei that have been previously observed with relativistically broadened iron emission lines. Utilizing data from the XMM-Newton European Photon Imaging Camera (EPIC-pn) we carefully model the spectral continuum, taking complex intrinsic absorption and emission into account. We then proceed to model the broad Fe K{alpha} feature in each source with two different accretion disk emission line codes, as well as a self-consistent, ionized accretion disk spectrum convolved with relativistic smearing from the inner disk. Comparing the results, we show that relativistic blurring of the disk emission is required to explain the spectrum in most sources, even when one models the full reflection spectrum from the photoionized disk.

  18. Translational anisotropy in the cosmic microwave background radiation and far-infrared emission by galactic dust clouds

    NASA Technical Reports Server (NTRS)

    Forman, M. A.

    1977-01-01

    The predicted emission spectrum of galactic dust at about 10 K is compared with the spectrum of 2.8-K universal blackbody radiation and with the spectrum of the anisotropy expected in the 2.8-K radiation due to motion of earth with respect to the coordinate system in which the radiation was last scattered. The extremely anisotropic galactic-dust emission spectrum may contribute a significant background to anisotropy measurements which scan through the galactic plane. The contamination would appear in an 8-mm scan around the celestial equator, for example, as a spurious 200 km/s velocity toward declination 0 deg, right ascension 19 hr, if predictions are correct. The predicted spectrum of dust emission in the galactic plane at longitudes not exceeding about 30 deg falls below the total 2.8-K cosmic background intensity at wavelengths of at least 1 mm.

  19. Inverse Compton Origin of the Hard X-ray and Soft gamma-ray Emission from the Galactic Ridge

    SciTech Connect

    Porter, Troy A.; Moskalenko, Igor V.; Strong, Andrew W.; Orlando, Elena; Bouchet, Laurent

    2008-09-30

    A recent re-determination of the non-thermal component of the hard X-ray to soft {gamma}-ray emission from the Galactic ridge, using the SPI instrument on the INTErnational Gamma-Ray Astrophysics Laboratory (INTEGRAL) Observatory, is shown to be well reproduced as inverse-Compton emission from the interstellar medium. Both cosmic-ray primary electrons and secondary electrons and positrons contribute to the emission. The prediction uses the GALPROP model and includes a new calculation of the interstellar radiation field. This may solve a long-standing mystery of the origin of this emission, and potentially opens a new window on Galactic cosmic rays.

  20. Spatial morphology of the secondary emission in the Galactic Center gamma-ray excess

    NASA Astrophysics Data System (ADS)

    Lacroix, Thomas; Macias, Oscar; Gordon, Chris; Panci, Paolo; BÅ`hm, Céline; Silk, Joseph

    2016-05-01

    Excess GeV gamma rays from the Galactic Center (GC) have been measured with the Fermi Large Area Telescope (LAT). The presence of the GC excess (GCE) appears to be robust with respect to changes in the diffuse galactic background modeling. The three main proposals for the GCE are an unresolved population of millisecond pulsars (MSPs), outbursts of cosmic rays from the GC region, and self-annihilating dark matter (DM). The injection of secondary electrons and positrons into the interstellar medium (ISM) by an unresolved population of MSPs or DM annihilations can lead to observable gamma-ray emission via inverse Compton scattering or bremsstrahlung. Here, we investigate how to determine whether secondaries are important in a model for the GCE. We develop a method of testing model fit which accounts for the different spatial morphologies of the secondary emission. We examine several models which give secondary emission and illustrate a case where a broadband analysis is not sufficient to determine the need for secondary emission.

  1. Radial distribution of the diffuse γ -ray emissivity in the Galactic disk

    NASA Astrophysics Data System (ADS)

    Yang, Ruizhi; Aharonian, Felix; Evoli, Carmelo

    2016-06-01

    The Fermi-LAT data accumulated over 7 years of γ -ray observations, together with the high resolution gas (CO & HI) and the dust opacity maps, are used to study the emissivity of γ -rays induced by interactions of cosmic rays (CRs) with the interstellar medium. Based on the dust opacity templates, the γ -ray emissivity was measured for 36 segments of the Galactic plane. Furthermore, the γ -ray emissivity was evaluated in six Galactocentric rings. Both the absolute emissivity and the energy spectra of γ -rays derived in the interval 0.2-100 GeV show significant variations along the galactic plane. The density of CRs, derived under the assumption that γ -rays are predominately produced in CR interactions with the interstellar gas, is characterized by a strong radial dependence. In the inner Galaxy the CR density substantially exceeds the density in the outer parts of the Galaxy: by a factor of a few at 10 GeV, and by more than an order of magnitude at 1 TeV. Remarkably, the energy distribution of CRs appears to be substantially harder than the energy spectrum obtained from direct measurements of local CRs. At the same time, the flux and the energy spectrum of multi-GeV protons derived from γ -ray data in the outskirts of the Galaxy is quite close to the measurements of local CRs.

  2. THE QUaD GALACTIC PLANE SURVEY. I. MAPS AND ANALYSIS OF DIFFUSE EMISSION

    SciTech Connect

    Culverhouse, T.; Friedman, R.; Ade, P.; Bowden, M.; Gear, W. K.; Gupta, S.; Melhuish, S. J.; Orlando, A.; Bock, J.; Leitch, E.; Brown, M. L.; Cahill, G.; Murphy, J. A.; Castro, P. G.; Memari, Y.; Church, S. E.; Hinderks, J. R.; Ganga, K.; Lange, A. E.

    2010-10-20

    We present a survey of {approx}800 deg{sup 2} of the galactic plane observed with the QUaD telescope. The primary products of the survey are maps of Stokes I, Q, and U parameters at 100 and 150 GHz, with spatial resolution of 5' and 3.'5, respectively. Two regions are covered, spanning approximately 245{sup 0}-295{sup 0} and 315{sup 0}-5{sup 0} in the galactic longitude l and -4{sup 0} < b < +4{sup 0} in the galactic latitude b. At 0.{sup 0}02 square pixel size, the median sensitivity is 74 and 107 kJy sr{sup -1} at 100 GHz and 150 GHz respectively in I, and 98 and 120 kJy sr{sup -1} for Q and U. In total intensity, we find an average spectral index of {alpha} = 2.35 {+-} 0.01(stat) {+-} 0.02(sys) for |b| {<=} 1{sup 0}, indicative of emission components other than thermal dust. A comparison to published dust, synchrotron, and free-free models implies an excess of emission in the 100 GHz QUaD band, while better agreement is found at 150 GHz. A smaller excess is observed when comparing QUaD 100 GHz data to the WMAP five-year W band; in this case, the excess is likely due to the wider bandwidth of QUaD. Combining the QUaD and WMAP data, a two-component spectral fit to the inner galactic plane (|b| {<=} 1{sup 0}) yields mean spectral indices of {alpha}{sub s} = -0.32 {+-} 0.03 and {alpha}{sub d} = 2.84 {+-} 0.03; the former is interpreted as a combination of the spectral indices of synchrotron, free-free, and dust, while the second is largely attributed to the thermal dust continuum. In the same galactic latitude range, the polarization data show a high degree of alignment perpendicular to the expected galactic magnetic field direction, and exhibit mean polarization fraction 1.38 {+-} 0.08(stat) {+-} 0.1(sys)% at 100 GHz and 1.70 {+-} 0.06(stat) {+-} 0.1(sys)% at 150 GHz. We find agreement in polarization fraction between QUaD 100 GHz and the WMAP W band, the latter giving 1.1% {+-} 0.4%.

  3. RESEARCH PAPER: Foreground removal of 21 cm fluctuation with multifrequency fitting

    NASA Astrophysics Data System (ADS)

    He, Li-Ping

    2009-06-01

    The 21 centimeter (21 cm) line emission from neutral hydrogen in the intergalactic medium (IGM) at high redshifts is strongly contaminated by foreground sources such as the diffuse Galactic synchrotron emission and free-free emission from the Galaxy, as well as emission from extragalactic radio sources, thus making its observation very complicated. However, the 21 cm signal can be recovered through its structure in frequency space, as the power spectrum of the foreground contamination is expected to be smooth over a wide band in frequency space while the 21 cm fluctuations vary significantly. We use a simple polynomial fitting to reconstruct the 21 cm signal around four frequencies 50, 100, 150 and 200MHz with an especially small channel width of 20 kHz. Our calculations show that this multifrequency fitting approach can effectively recover the 21 cm signal in the frequency range 100 ~ 200 MHz. However, this method doesn't work well around 50 MHz because of the low intensity of the 21 cm signal at this frequency. We also show that the fluctuation of detector noise can be suppressed to a very low level by taking long integration times, which means that we can reach a sensitivity of approx10 mK at 150 MHz with 40 antennas in 120 hours of observations.

  4. Spectropolarimetric test of the relativistic disk model for the broad emission lines of active galactic nuclei

    NASA Technical Reports Server (NTRS)

    Chen, Kaiyou; Halpern, Jules P.

    1990-01-01

    Previously, it was claimed that the broad emission lines of the radio galaxy Arp 102B can be fitted by the line profile from a simple relativistic Keplerian thin disk. It was argued that the lines originating from the relativistic accretion disk could be polarized due to electron scattering, which is likely to be the dominant opacity in the line-emitting region of Arp 102B. In the present work, the expected polarization properties of these broad emission lines are calculated. The percentage of polarization depends strongly on the inclination angle. For some angles, the red peak of the polarized, double-peaked line profile can be higher than the blue peak. This is in contrast to the total line profile, in which the blue peak is always higher than the red one. Spectropolarimetric observations could, therefore, provide an independent test of the relativistic disk model for the broad emission lines of Arp 102B and other active galactic nuclei.

  5. Discovery of New Faint Radio Emission on 8° to 3' Scales in the Coma Field, and Some Galactic and Extragalactic Implications

    NASA Astrophysics Data System (ADS)

    Kronberg, P. P.; Kothes, R.; Salter, C. J.; Perillat, P.

    2007-04-01

    We present a deep, 8° diameter, 0.4 GHz radio image using a first-time combination of the NAIC Arecibo 305 m telescope in Puerto Rico and the wide-angle interferometer at the Dominion Radio Astrophysical Observatory at Penticton, Canada. Our observations are centered on the Coma Cluster of galaxies in the ``Great Wall'' of galaxies near the north Galactic pole. The complementary nature of these two instruments enables us to produce a distortion-free image that is sensitive to radiation on scales from 8° down to that of an individual galaxy halo at the 100 Mpc distance of the Great Wall. Newly revealed patches of distributed radio ``glow'' are seen well above the detection limit. One prominent such area coincides with groupings of radio galaxies near the Coma Cluster and indicates intergalactic magnetic fields in the range 0.2-0.4 μG on scales of up to ~4 Mpc. Other patches of diffuse emission, not previously explored at these high latitudes on arcminute scales, probably consist of Galactic ``cirrus.'' A striking anticorrelation is found between low-level diffuse radio glow and some regions of enhanced optical galaxy surface density, suggesting that cosmological large-scale structure, normally defined by the baryonic (or dark) matter density, is not uniquely traced by faint continuum radio glow. Rather, intergalactic diffuse synchrotron radiation may be a proxy for IGM cosmic-ray and magnetic energy density, rather than matter density. The diffuse, arcminute-level structures over a large region of sky are potentially important pathfinders to CMB foreground radiation on high multipole scales.

  6. Power spectrum analysis of polarized emission from the Canadian galactic plane survey

    SciTech Connect

    Stutz, R. A.; Rosolowsky, E. W.; Kothes, R.; Landecker, T. L.

    2014-05-20

    Angular power spectra are calculated and presented for the entirety of the Canadian Galactic Plane Survey polarization data set at 1.4 GHz covering an area of 1060 deg{sup 2}. The data analyzed are a combination of data from the 100 m Effelsberg Telescope, the 26 m Telescope at the Dominion Radio Astrophysical Observatory, and the Synthesis Telescope at the Dominion Radio Astrophysical Observatory, allowing all scales to be sampled down to arcminute resolution. The resulting power spectra cover multipoles from ℓ ≈ 60 to ℓ ≈ 10{sup 4} and display both a power-law component at low multipoles and a flattening at high multipoles from point sources. We fit the power spectrum with a model that accounts for these components and instrumental effects. The resulting power-law indices are found to have a mode of 2.3, similar to previous results. However, there are significant regional variations in the index, defying attempts to characterize the emission with a single value. The power-law index is found to increase away from the Galactic plane. A transition from small-scale to large-scale structure is evident at b = 9°, associated with the disk-halo transition in a 15° region around l = 108°. Localized variations in the index are found toward H II regions and supernova remnants, but the interpretation of these variations is inconclusive. The power in the polarized emission is anticorrelated with bright thermal emission (traced by Hα emission) indicating that the thermal emission depolarizes background synchrotron emission.

  7. Power Spectrum Analysis of Polarized Emission from the Canadian Galactic Plane Survey

    NASA Astrophysics Data System (ADS)

    Stutz, R. A.; Rosolowsky, E. W.; Kothes, R.; Landecker, T. L.

    2014-05-01

    Angular power spectra are calculated and presented for the entirety of the Canadian Galactic Plane Survey polarization data set at 1.4 GHz covering an area of 1060 deg2. The data analyzed are a combination of data from the 100 m Effelsberg Telescope, the 26 m Telescope at the Dominion Radio Astrophysical Observatory, and the Synthesis Telescope at the Dominion Radio Astrophysical Observatory, allowing all scales to be sampled down to arcminute resolution. The resulting power spectra cover multipoles from l ≈ 60 to l ≈ 104 and display both a power-law component at low multipoles and a flattening at high multipoles from point sources. We fit the power spectrum with a model that accounts for these components and instrumental effects. The resulting power-law indices are found to have a mode of 2.3, similar to previous results. However, there are significant regional variations in the index, defying attempts to characterize the emission with a single value. The power-law index is found to increase away from the Galactic plane. A transition from small-scale to large-scale structure is evident at b = 9°, associated with the disk-halo transition in a 15° region around l = 108°. Localized variations in the index are found toward H II regions and supernova remnants, but the interpretation of these variations is inconclusive. The power in the polarized emission is anticorrelated with bright thermal emission (traced by Hα emission) indicating that the thermal emission depolarizes background synchrotron emission.

  8. Cosmic rays from multi-wavelength observations of the Galactic diffuse emission

    NASA Astrophysics Data System (ADS)

    Orlando, Elena

    2016-05-01

    Cosmic rays (CRs) generate diffuse emission while interacting with the Galactic magnetic field (B-field), the interstellar gas and the radiation field. This diffuse emission extends from radio, microwaves, through X-rays, to high-energy gamma rays. Diffuse emission has considerably increased the interest of the astrophysical community due to recent detailed observations by Planck, Fermi-LAT, and by very-high energy Cherenkov telescopes. Observations of this diffuse emission and comparison with detailed predictions are used to gain information on the properties of CRs, such as their density, spectra, distribution and propagation in the Galaxy. Unfortunately disentangling and characterizing this diffuse emission strongly depends on uncertainties in the knowledge of unresolved sources, gas, radiation fields, and B-fields, other than CRs throughout the Galaxy. We discuss here the diffuse emission produced by CRs and its uncertainties, and the comparison of this predicted emission with recent multi-wavelength observations. We show insights on CR spectra and intensities. Then we address the importance for forthcoming telescopes, especially for the Square Kilometre Array telescope (SKA) and the Cherencov Telescope Array (CTA), and for missions at MeV.

  9. X-RAY POINT-SOURCE POPULATIONS CONSTITUTING THE GALACTIC RIDGE X-RAY EMISSION

    SciTech Connect

    Morihana, Kumiko; Tsujimoto, Masahiro; Ebisawa, Ken; Yoshida, Tessei

    2013-03-20

    Apparently diffuse X-ray emission has been known to exist along the central quarter of the Galactic Plane since the beginning of X-ray astronomy; this is referred to as the Galactic Ridge X-ray emission (GRXE). Recent deep X-ray observations have shown that numerous X-ray point sources account for a large fraction of the GRXE in the hard band (2-8 keV). However, the nature of these sources is poorly understood. Using the deepest X-ray observations made in the Chandra bulge field, we present the result of a coherent photometric and spectroscopic analysis of individual X-ray point sources for the purpose of constraining their nature and deriving their fractional contributions to the hard-band continuum and Fe K line emission of the GRXE. Based on the X-ray color-color diagram, we divided the point sources into three groups: A (hard), B (soft and broad spectrum), and C (soft and peaked spectrum). The group A sources are further decomposed spectrally into thermal and non-thermal sources with different fractions in different flux ranges. From their X-ray properties, we speculate that the group A non-thermal sources are mostly active galactic nuclei and the thermal sources are mostly white dwarf (WD) binaries such as magnetic and non-magnetic cataclysmic variables (CVs), pre-CVs, and symbiotic stars, whereas the group B and C sources are X-ray active stars in flares and quiescence, respectively. In the log N-log S curve of the 2-8 keV band, the group A non-thermal sources are dominant above Almost-Equal-To 10{sup -14} erg cm{sup -2} s{sup -1}, which is gradually taken over by Galactic sources in the fainter flux ranges. The Fe K{alpha} emission is mostly from the group A thermal (WD binaries) and the group B (X-ray active stars) sources.

  10. THE PREVALENCE OF NARROW OPTICAL Fe II EMISSION LINES IN TYPE 1 ACTIVE GALACTIC NUCLEI

    SciTech Connect

    Dong Xiaobo; Wang Jianguo; Wang Tinggui; Wang Huiyuan; Zhou Hongyan; Ho, Luis C.; Fan Xiaohui

    2010-10-01

    From detailed spectral analysis of a large sample of low-redshift active galactic nuclei (AGNs) selected from the Sloan Digital Sky Survey, we demonstrate-statistically for the first time-that narrow optical Fe II emission lines, both permitted and forbidden, are prevalent in type 1 AGNs. Remarkably, these optical lines are completely absent in type 2 AGNs, across a wide luminosity range, from Seyfert 2 galaxies to type 2 quasars. We suggest that the narrow Fe II-emitting gas is confined to a disk-like geometry in the innermost regions of the narrow-line region on physical scales smaller than the obscuring torus.

  11. Spectrum and variation of gamma-ray emission from the galactic center region

    NASA Technical Reports Server (NTRS)

    Riegler, G. R.; Ling, J. C.; Mahoney, W. A.; Wheaton, W. A.; Jacobson, A. S.

    1982-01-01

    Continuum emission at 60-300 keV from the galactic center region was observed to decrease in intensity by 45 percent and to show a spectrum steepening between fall 1979 and spring 1980. At the same time 511 keV positron annihilation radiation decreased by a comparable fraction. No variations over shorter time scales were detected. The observations are consistent with a model where positrons and hard X-rays are produced in an electromagnetic cascade near a massive black hole.

  12. Related investigations on the physics of high energy emission from active galactic nuclei

    NASA Technical Reports Server (NTRS)

    Margon, Bruce

    1991-01-01

    The Final Technical Report on a number of related investigations on the physics of high energy emission from active galactic nuclei, such as Seyfert galaxies and quasi-stellar objects is presented. The chief conclusions of the work are briefly described, and citations to the papers supported by this grant and published in the refereed scientific literature are provided. Areas of research included: 'warm' galaxies observed in x rays; x ray/infrared correlations in galaxies; the contribution of active galaxies to the cosmic x ray background radiation; and an unusual x ray emitting starburst galaxy.

  13. IUE observations of the Henize-Carlson sample of peculiar emission line supergiants: The galactic analogs of the Magellanic Zoo

    NASA Technical Reports Server (NTRS)

    Shore, Steven N.; Brown, Douglas N.; Sanduleak, N.

    1986-01-01

    Some 15 stars from the Carlson-Henize survey of southern peculiar emission line stars were studied. From both the optical and UV spectra, they appear to be galactic counterparts of the most extreme early-type emission line supergiants of the Magellanic Clouds.

  14. WIDESPREAD METHANOL EMISSION FROM THE GALACTIC CENTER: THE ROLE OF COSMIC RAYS

    SciTech Connect

    Yusef-Zadeh, F.; Royster, M.; Cotton, W.; Viti, S.; Wardle, M.

    2013-02-20

    We report the discovery of a widespread population of collisionally excited methanol J = 4{sub -1} to 3{sub 0} E sources at 36.2 GHz from the inner 66' Multiplication-Sign 18' (160 Multiplication-Sign 43 pc) of the Galactic center. This spectral feature was imaged with a spectral resolution of 16.6 km s{sup -1} taken from 41 channels of a Very Large Array continuum survey of the Galactic center region. The revelation of 356 methanol sources, most of which are maser candidates, suggests a large abundance of methanol in the gas phase in the Galactic center region. There is also spatial and kinematic correlation between SiO (2-1) and CH{sub 3}OH emission from four Galactic center clouds: the +50 and +20 km s{sup -1} clouds and G0.13-0.13 and G0.25 + 0.01. The enhanced abundance of methanol is accounted for in terms of induced photodesorption by cosmic rays as they travel through a molecular core, collide, dissociate, ionize, and excite Lyman Werner transitions of H{sub 2}. A time-dependent chemical model in which cosmic rays drive the chemistry of the gas predicts CH{sub 3}OH abundance of 10{sup -8} to 10{sup -7} on a chemical timescale of 5 Multiplication-Sign 10{sup 4} to 5 Multiplication-Sign 10{sup 5} years. The average methanol abundance produced by the release of methanol from grain surfaces is consistent with the available data.

  15. He II EMISSION IN Lyalpha NEBULAE: ACTIVE GALACTIC NUCLEUS OR COOLING RADIATION?

    SciTech Connect

    Scarlata, C.; Colbert, J.; Teplitz, H. I.; Bridge, C.; Francis, P.; Palunas, P.; Siana, B.; Williger, G. M.; Woodgate, B.

    2009-12-01

    We present a study of an extended Lyalpha nebula located in a known overdensity at z approx 2.38. The data include multiwavelength photometry covering the rest-frame spectral range from 0.1 to 250 mum, and deep optical spectra of the sources associated with the extended emission. Two galaxies are associated with the Lyalpha nebula. One of them is a dust enshrouded active galactic nucleus (AGN), while the other is a powerful starburst, forming stars at approx>400 M{sub sun} yr{sup -1}. We detect the He II emission line at 1640 A in the spectrum of the obscured AGN, but detect no emission from other highly ionized metals (C IV or N V) as is expected from an AGN. One scenario that simultaneously reproduces the width of the detected emission lines, the lack of C IV emission, and the geometry of the emitting gas, is that the He II and the Lyalpha emission are the result of cooling gas that is being accreted on the dark matter halo of the two galaxies, Ly1 and Ly2. Given the complexity of the environment associated with our Lyalpha nebula it is possible that various mechanisms of excitation are at work simultaneously.

  16. Origin and z-distribution of Galactic diffuse [C II] emission

    NASA Astrophysics Data System (ADS)

    Velusamy, T.; Langer, W. D.

    2014-12-01

    Context. The [C ii] emission is an important probe of star formation in the Galaxy and in external galaxies. The GOT C+ survey and its follow up observations of spectrally resolved 1.9 THz [C ii] emission using Herschel HIFI provides the data needed to quantify the Galactic interstellar [C ii] gas components as tracers of star formation. Aims: We determine the source of the diffuse [C ii] emission by studying its spatial (radial and vertical) distributions by separating and evaluating the fractions of [C ii] and CO emissions in the Galactic ISM gas components. Methods: We used the HIFI [C ii] Galactic survey (GOT C+), along with ancillary H i, 12CO, 13CO, and C18O data toward 354 lines of sight, and several HIFI [C ii] and [C i] position-velocity maps. We quantified the emission in each spectral line profile by evaluating the intensities in 3 km s-1 wide velocity bins, "spaxels". Using the detection of [C ii] with CO or [C i], we separated the dense and diffuse gas components. We derived 2D Galactic disk maps using the spaxel velocities for kinematic distances. We separated the warm and cold H2 gases by comparing CO emissions with and without associated [C ii]. Results: We find evidence of widespread diffuse [C ii] emission with a z-scale distribution larger than that for the total [C ii] or CO. The diffuse [C ii] emission consists of (i) diffuse molecular (CO-faint) H2 clouds and (ii) diffuse H i clouds and/or WIM. In the inner Galaxy we find a lack of [C ii] detections in a majority (~62%) of H i spaxels and show that the diffuse component primarily comes from the WIM (~21%) and that the H i gas is not a major contributor to the diffuse component (~6%). The warm-H2 radial profile shows an excess in the range 4 to 7 kpc, consistent with enhanced star formation there. Conclusions: We derive, for the first time, the 2D [C ii] spatial distribution in the plane and the z-distributions of the individual [C ii] gas component. From the GOT C+ detections we estimate the

  17. A celestial gamma-ray foreground due to the albedo of small solar system bodies and a remote probe of the interstellar cosmic ray spectrum

    SciTech Connect

    Moskalenko, Igor V.; Porter, Troy A.; Digel, Seth W.; Michelson, Peter F.; Ormes, Jonathan F.

    2007-12-17

    We calculate the {gamma}-ray albedo flux from cosmic-ray (CR) interactions with the solid rock and ice in Main Belt asteroids and Kuiper Belt objects (KBOs) using the Moon as a template. We show that the {gamma}-ray albedo for the Main Belt and Kuiper Belt strongly depends on the small-body mass spectrum of each system and may be detectable by the forthcoming Gamma Ray Large Area Space Telescope (GLAST). The orbits of the Main Belt asteroids and KBOs are distributed near the ecliptic, which passes through the Galactic center and high Galactic latitudes. If detected, the {gamma}-ray emission by the Main Belt and Kuiper Belt has to be taken into account when analyzing weak {gamma}-ray sources close to the ecliptic, especially near the Galactic center and for signals at high Galactic latitudes, such as the extragalactic {gamma}-ray emission. Additionally, it can be used to probe the spectrum of CR nuclei at close-to-interstellar conditions, and the mass spectrum of small bodies in the Main Belt and Kuiper Belt. The asteroid albedo spectrum also exhibits a 511 keV line due to secondary positrons annihilating in the rock. This may be an important and previously unrecognized celestial foreground for the INTErnational Gamma-Ray Astrophysics Laboratory (INTEGRAL) observations of the Galactic 511 keV line emission including the direction of the Galactic center.

  18. The galactic dynamo, the helical force free field and the emissions of AGN

    SciTech Connect

    Colgate, S.; Li, Hui

    1997-05-01

    We present a theory relating the central galactic black hole (BH) formation to the galactic dynamo through an accretion disk. The associated AGN emissions and the collimated radio sources are then a result of the dynamo process. A unified theory of quasar and BL-Lac formation (hereafter AGN) starts with the collapse of damped Lyman-alpha clouds, presumably proto-galaxies, which then evolve to a central disk and black hole, (BH). An alpha - omega dynamo forms in this accretion disk where the augmentation of the poloidal field from the toroidal field depends upon star disk collisions. The winding number of the inner most orbit of the disk is so large, tilde 10 to the 11th power that the total gain of the dynamo is semi-infinite, and the original seed field of no consequence. The total magnetic flux produced is tilde 10000 times that of the galaxy, sufficient to explain the much larger flux of clusters. The semi-infinite gain of the dynamo implies that the field saturates at the dynamic stress so that most of the free energy of formation of the BH is carried off as magnetic energy in the form of a magnetic helix. The dissipation of this magnetic energy leads to the unique emission spectrum of AGN as well as the equally startling collimated radio and optical sources.

  19. Observations of medium energy gamma ray emission from the galactic center region

    NASA Technical Reports Server (NTRS)

    Kniffen, D. A.; Bertsch, D. L.; Morris, D. J.; Palmeira, R. A. R.; Rao, K. R.

    1978-01-01

    Measurements of the gamma-ray emission in the medium energy range between 15 and 100 MeV, obtained during two ballon flights from Brazil are presented. The importance of this energy region in determining whether pi deg - decay of electron bremsstrahlung is the most likely dominant source mechanism is discussed along with the implications of such observations. Specifically, the data from this experiment suggest that emission from the galactic plane is similar to theoretical spectrum calculations including both sources mechanisms, but with the bremsstrahlung component enhanced by a factor of about 2. A spectral distribution of gamma-rays produced in the residual atmosphere above the instrument is also presented and compared with other data. A rather smooth spectral variation from high to low energies is found for the atmospheric spectrum.

  20. Polarization of the far-infrared emission from the thermal filaments of the Galactic center arc

    NASA Technical Reports Server (NTRS)

    Morris, M.; Davidson, J. A.; Werner, M.; Dotson, J.; Figer, D. F.; Hildebrand, R.; Novak, G.; Platt, S.

    1992-01-01

    The polarization of the 100 micron continuum emission has been measured at 14 positions in the dense, warm molecular cloud associated with the arched filaments, or the 'bridge', of the radio arc near the Galactic center. At all positions the percent polarization is found to be quite large, ranging up to 6.5 percent. The polarization is interpreted in terms of thermal emission by magnetically aligned dust grains. The directions of the polarization vectors then indicate that the magnetic field is (1) parallel to the long dimension of the thermal radio filaments, and (2) very uniform on scales of 1-10 pc. Of several explanations for the inferred field geometry, the simplest is that it results from the unusually large dynamical shear in the emitting cloud.

  1. Modeling the Extragalactic Epoch of Reionization Foreground

    NASA Astrophysics Data System (ADS)

    Carroll, Patricia A.

    The Epoch of Reionization represents a largely unexplored yet fundamental chapter of the early universe. During this period, spanning several hundred million years, the first stars and galaxies formed and the Hydrogen-dominated intergalactic medium transitioned from a predominantly neutral to ionized state. Modern efforts to study exactly when and how reionization occurred are largely focused on the distribution of neutral Hydrogen gas and its evolution in response to the increasing abundance of luminous objects and ionizing flux. The Murchison Widefield Array is a low frequency radio interferometer designed as a first generation EoR experiment. The predominant systematic difficulty in making a detection of the primordial HI signal is the overwhelmingly bright emission from the intervening foreground galaxies and quasars. This thesis presents novel survey methods used to create a highly precise and reliable catalog of discrete extragalactic sources for the purposes of both calibration and foreground removal.

  2. Planck intermediate results. XXIII. Galactic plane emission components derived from Planck with ancillary data

    NASA Astrophysics Data System (ADS)

    Planck Collaboration; Ade, P. A. R.; Aghanim, N.; Alves, M. I. R.; Arnaud, M.; Ashdown, M.; Atrio-Barandela, F.; Aumont, J.; Baccigalupi, C.; Banday, A. J.; Barreiro, R. B.; Battaner, E.; Benabed, K.; Benoit-Lévy, A.; Bernard, J.-P.; Bersanelli, M.; Bielewicz, P.; Bobin, J.; Bonaldi, A.; Bond, J. R.; Bouchet, F. R.; Boulanger, F.; Burigana, C.; Cardoso, J.-F.; Catalano, A.; Chamballu, A.; Chiang, H. C.; Christensen, P. R.; Clements, D. L.; Colombi, S.; Colombo, L. P. L.; Combet, C.; Couchot, F.; Crill, B. P.; Cuttaia, F.; Danese, L.; Davies, R. D.; Davis, R. J.; de Bernardis, P.; de Rosa, A.; de Zotti, G.; Delabrouille, J.; Dickinson, C.; Diego, J. M.; Donzelli, S.; Doré, O.; Douspis, M.; Dupac, X.; Efstathiou, G.; Enßlin, T. A.; Eriksen, H. K.; Finelli, F.; Forni, O.; Frailis, M.; Franceschi, E.; Galeotta, S.; Ganga, K.; Génova-Santos, R. T.; Ghosh, T.; Giard, M.; Giardino, G.; Giraud-Héraud, Y.; González-Nuevo, J.; Górski, K. M.; Gregorio, A.; Gruppuso, A.; Hansen, F. K.; Harrison, D. L.; Henrot-Versillé, S.; Herranz, D.; Hildebrandt, S. R.; Hivon, E.; Hobson, M.; Hornstrup, A.; Hovest, W.; Huffenberger, K. M.; Jaffe, A. H.; Jaffe, T. R.; Jones, W. C.; Keihänen, E.; Keskitalo, R.; Kisner, T. S.; Kneissl, R.; Knoche, J.; Kunz, M.; Kurki-Suonio, H.; Lagache, G.; Lähteenmäki, A.; Lamarre, J.-M.; Lasenby, A.; Lawrence, C. R.; Leonardi, R.; Liguori, M.; Lilje, P. B.; Linden-Vørnle, M.; López-Caniego, M.; Lubin, P. M.; Macías-Pérez, J. F.; Maino, D.; Mandolesi, N.; Martin, P. G.; Martínez-González, E.; Masi, S.; Massardi, M.; Matarrese, S.; Mazzotta, P.; Meinhold, P. R.; Melchiorri, A.; Mendes, L.; Mennella, A.; Migliaccio, M.; Mitra, S.; Miville-Deschênes, M.-A.; Moneti, A.; Montier, L.; Morgante, G.; Mortlock, D.; Munshi, D.; Murphy, J. A.; Naselsky, P.; Nati, F.; Natoli, P.; Nørgaard-Nielsen, H. U.; Noviello, F.; Novikov, D.; Novikov, I.; Oxborrow, C. A.; Pagano, L.; Pajot, F.; Paladini, R.; Paoletti, D.; Pasian, F.; Pearson, T. J.; Peel, M.; Perdereau, O.; Perrotta, F.; Piacentini, F.; Piat, M.; Pierpaoli, E.; Pietrobon, D.; Plaszczynski, S.; Pointecouteau, E.; Polenta, G.; Ponthieu, N.; Popa, L.; Pratt, G. W.; Prunet, S.; Puget, J.-L.; Rachen, J. P.; Reach, W. T.; Rebolo, R.; Reich, W.; Reinecke, M.; Remazeilles, M.; Renault, C.; Ricciardi, S.; Riller, T.; Ristorcelli, I.; Rocha, G.; Rosset, C.; Roudier, G.; Rubiño-Martín, J. A.; Rusholme, B.; Sandri, M.; Savini, G.; Scott, D.; Spencer, L. D.; Stolyarov, V.; Strong, A. W.; Sutton, D.; Suur-Uski, A.-S.; Sygnet, J.-F.; Tauber, J. A.; Tavagnacco, D.; Terenzi, L.; Tibbs, C. T.; Toffolatti, L.; Tomasi, M.; Tristram, M.; Tucci, M.; Valenziano, L.; Valiviita, J.; Van Tent, B.; Varis, J.; Vielva, P.; Villa, F.; Wade, L. A.; Wandelt, B. D.; Watson, R.; Yvon, D.; Zacchei, A.; Zonca, A.

    2015-08-01

    Planck data when combined with ancillary data provide a unique opportunity to separate the diffuse emission components of the inner Galaxy. The purpose of the paper is to elucidate the morphology of the various emission components in the strong star-formation region lying inside the solar radius and to clarify the relationship between the various components. The region of the Galactic plane covered is l = 300° → 0° → 60° wherestar-formation is highest and the emission is strong enough to make meaningful component separation. The latitude widths in this longitude range lie between 1° and 2°, which correspond to FWHM z-widths of 100-200 pc at a typical distance of 6 kpc. The four emission components studied here are synchrotron, free-free, anomalous microwave emission (AME), and thermal (vibrational) dust emission. These components are identified by constructing spectral energy distributions (SEDs) at positions along the Galactic plane using the wide frequency coverage of Planck (28.4-857 GHz) in combination with low-frequency radio data at 0.408-2.3 GHz plus WMAP data at 23-94 GHz, along with far-infrared (FIR) data from COBE-DIRBE and IRAS. The free-free component is determined from radio recombination line (RRL) data. AME is found to be comparable in brightness to the free-free emission on the Galactic plane in the frequency range 20-40 GHz with a width in latitude similar to that of the thermal dust; it comprises 45 ± 1% of the total 28.4 GHz emission in the longitude range l = 300° → 0° → 60°. The free-free component is the narrowest, reflecting the fact that it is produced by current star-formation as traced by the narrow distribution of OB stars. It is the dominant emission on the plane between 60 and 100 GHz. RRLs from this ionized gas are used to assess its distance, leading to a free-free z-width of FWHM ≈ 100 pc. The narrow synchrotron component has a low-frequency brightness spectral index βsynch ≈ -2.7 that is similar to the broad

  3. GRIS observations of Al-26 gamma-ray line emission from two points in the Galactic plane

    NASA Technical Reports Server (NTRS)

    Teegarden, B. J.; Barthelmy, S. D.; Gehrels, N.; Tueller, J.; Leventhal, M.

    1991-01-01

    Both of the Gamma-Ray Imaging Spectrometer (GRIS) experiment's two observations of the Galactic center region, at l = zero and 335 deg respectively, detected Al-26 gamma-ray line emission. While these observations are consistent with the assumed high-energy gamma-ray distribution, they are consistent with other distributions as well. The data suggest that the Al-26 emission is distributed over Galactic longitude rather than being confined to a point source. The GRIS data also indicate that the 1809 keV line is broadened.

  4. Circular polarization of the CMB: Foregrounds and detection prospects

    NASA Astrophysics Data System (ADS)

    King, Soma; Lubin, Philip

    2016-07-01

    The cosmic microwave background (CMB) is one of the finest probes of cosmology. Its all-sky temperature and linear polarization fluctuations have been measured precisely at a level of δ T /TCMB˜10-6 . In contrast, circular polarization (C P ) of the CMB has not been precisely explored. The current upper limit on the C P of the CMB is at a level of δ V /TCMB˜10-4 and is limited on large scales. Some of the cosmologically important sources which can induce a C P in the CMB include early Universe symmetry breaking, a primordial magnetic field, galaxy clusters, and Pop III stars (also known as the first stars). Among these sources, Pop III stars are expected to induce the strongest signal with levels strongly dependent on the frequency of observation and on the number, Np, of the Pop III stars per halo. Optimistically, a C P signal in the CMB resulting from the Pop III stars could be at a level of δ V /TCMB˜2 ×10-7 in scales of 1° at 10 GHz, which is much smaller than the currently existing upper limits on the C P measurements. Primary foregrounds in the cosmological C P detection will come from the galactic synchrotron emission, which is naturally (intrinsically) circularly polarized. We use data-driven models of the galactic magnetic field, thermal electron density, and relativistic electron density to simulate all-sky maps of the galactic C P . This work also points out that the galactic C P levels are important below 50 GHz and is an important factor for telescopes aiming to detect primordial B modes using C P as a systematic rejection channel. In this paper, we focus on a SNR evaluation for the detectability of the Pop III induced C P signal in the CMB. We find that a SNR higher than unity is achievable, for example, with a 10 m telescope and an observation time of 20 months at 10 GHz, if Np≥100 . We also find that, if frequency of observation and resolution of the beam is appropriately chosen, a SNR higher than unity is possible with Np≥10 and

  5. ON THE FERMI LARGE AREA TELESCOPE SURPLUS OF DIFFUSE GALACTIC GAMMA-RAY EMISSION

    SciTech Connect

    Völk, H. J.; Berezhko, E. G.

    2013-11-10

    Recent observations of diffuse Galactic γ-ray emission (DGE) by the Fermi Large Area Telescope (Fermi-LAT) have shown significant deviations, above a few GeV to about 100 GeV, from DGE models that use the GALPROP code for the propagation of cosmic ray (CR) particles outside their sources in the Galaxy and their interaction with the target distributions of the interstellar gas and radiation fields. The surplus of radiation observed is most pronounced in the inner Galaxy, where the concentration of CR sources is strongest. The present study investigates this 'Fermi-LAT Galactic Plane Surplus' by estimating the γ-ray emission from the sources themselves, which is disregarded in the above DGE models. It is shown that the expected hard spectrum of CRs, still confined in their sources (source cosmic rays, SCRs), can indeed explain this surplus. The method is based on earlier studies regarding the so-called EGRET GeV excess, which by now is generally interpreted as an instrumental effect. The contribution from SCRs is also predicted to increasingly exceed the DGE models above 100 GeV, up to γ-ray energies of about 10 TeV, where the corresponding surplus exceeds the hadronic part of the DGE by about one order of magnitude. Above such energies, the emission surplus should decrease again with energy due to the finite lifetime of the assumed supernova remnant sources. Observations of the DGE in the inner Galaxy at 15 TeV with the ground-based Milagro γ-ray detector and, at TeV energies, with the ARGO-YBJ detector are interpreted to provide confirmation of a significant SCR contribution to the DGE.

  6. Modeling the thermal X-ray emission around the Galactic center from colliding stellar winds

    NASA Astrophysics Data System (ADS)

    Russell, Christopher Michael Post; Wang, Daniel; Cuadra, Jorge

    2016-04-01

    The Galactic center is a hotbed of astrophysical activity. Powering these processes is the injection of wind material from ˜30 massive Wolf-Rayet (WR) stars orbiting within 12" of the super-massive black hole (SMBH). Hydrodynamic simulations of such colliding and accreting winds produce a complex density and temperature structure of cold wind material shocking with the ambient medium, creating a large reservoir of hot, X-ray-emitting gas. A Chandra X-ray Visionary Program that observed the Galactic center for 3 Ms resolved this diffuse emission. This work computes the X-ray emission from these hydrodynamic simulations of the WR winds with the aim of reproducing the Chandra observations, amid exploring a variety of SMBH feedback mechanisms. The success of the model is the spectrum from the 2"-5" ring around the SMBH matches the shape of the observed spectrum very well. This naturally explains that the hot gas comes from colliding WR winds, and that the winds speeds of these stars are in general well constrained. The model flux in this ring and over the ±6" images of 4-9keV is ˜2.2× lower than the observations, with stronger feedback mechanisms leading to weaker X-ray emission since more hot, X-ray-emitting gas is cleared from the spherical r < 12" simulation volume. Possible improvements to rectify this flux discrepancy are increasing the mass loss rates of the WRs and/or adding more gas into the simulation, such as from the O stars and their winds, so the adiabatic WR shocks occur closer to their stars, thereby becoming brighter in X-rays.

  7. Modeling the thermal X-ray emission around the Galactic center from colliding stellar winds

    NASA Astrophysics Data System (ADS)

    Post Russell, Christopher Michael; Wang, Daniel; Cuadra, Jorge

    2016-04-01

    The Galactic center is a hotbed of astrophysical activity. Powering these processes is the injection of wind material from ˜30 massive Wolf-Rayet (WR) stars orbiting within 12” of the super-massive black hole (SMBH). Hydrodynamic simulations of such colliding and accreting winds produce a complex density and temperature structure of cold wind material shocking with the ambient medium, creating a large reservoir of hot, X-ray-emitting gas. A Chandra X-ray Visionary Program that observed the Galactic center for 3 Ms resolved this diffuse emission. This work computes the X-ray emission from these hydrodynamic simulations of the WR winds with the aim of reproducing the Chandra observations, amid exploring a variety of SMBH feedback mechanisms. The success of the model is the spectrum from the 2”-5” ring around the SMBH matches the shape of the observed spectrum very well. This naturally explains that the hot gas comes from colliding WR winds, and that the winds speeds of these stars are in general well constrained. The model flux in this ring and over the ±6” images of 4-9keV is ˜2.2× lower than the observations, with stronger feedback mechanisms leading to weaker X-ray emission since more hot, X-ray-emitting gas is cleared from the spherical r < 12” simulation volume. Possible improvements to rectify this flux discrepancy are increasing the mass loss rates of the WRs and/or adding more gas into the simulation, such as from the O stars and their winds, so the adiabatic WR shocks occur closer to their stars, thereby becoming brighter in X-rays.

  8. Grain physics and infrared dust emission in active galactic nucleus environments

    SciTech Connect

    Hensley, Brandon S.; Ostriker, Jeremiah P.; Ciotti, Luca

    2014-07-01

    We study the effects of a detailed dust treatment on the properties and evolution of early-type galaxies containing central black holes, as determined by active galactic nucleus (AGN) feedback. We find that during cooling flow episodes, radiation pressure on the dust in and interior to infalling shells of cold gas can greatly impact the amount of gas able to be accreted and therefore the frequency of AGN bursts. However, the overall hydrodynamic evolution of all models, including mass budget, is relatively robust to the assumptions on dust. We find that IR re-emission from hot dust can dominate the bolometric luminosity of the galaxy during the early stages of an AGN burst, reaching values in excess of 10{sup 46} erg s{sup –1}. The AGN-emitted UV is largely absorbed, but the optical depth in the IR does not exceed unity, so the radiation momentum input never exceeds L {sub BH}/c. We constrain the viability of our models by comparing the AGN duty cycle, broadband luminosities, dust mass, black hole mass, and other model predictions to current observations. These constraints force us towards models wherein the dust to metals ratios are ≅ 1% of the Galactic value, and only models with a dynamic dust to gas ratio are able to produce both quiescent galaxies consistent with observations and high obscured fractions during AGN 'on' phases. During AGN outbursts, we predict that a large fraction of the FIR luminosity can be attributed to warm dust emission (≅ 100 K) from dense dusty gas within ≤1 kpc reradiating the AGN UV emission.

  9. Inverse Compton Emission from Galactic Supernova Remnants: Effect of the Interstellar Radiation Field

    SciTech Connect

    Porter, Troy A.; Moskalenko, Igor V.; Strong, Andrew W.; /Garching, Max Planck Inst., MPE

    2006-08-01

    The evidence for particle acceleration in supernova shells comes from electrons whose synchrotron emission is observed in radio and X-rays. Recent observations by the HESS instrument reveal that supernova remnants also emit TeV {gamma}-rays; long awaited experimental evidence that supernova remnants can accelerate cosmic rays up to the ''knee'' energies. Still, uncertainty exists whether these {gamma}-rays are produced by electrons via inverse Compton scattering or by protons via {pi}{sup 0}-decay. The multi-wavelength spectra of supernova remnants can be fitted with both mechanisms, although a preference is often given to {pi}{sup 0}-decay due to the spectral shape at very high energies. A recent study of the interstellar radiation field indicates that its energy density, especially in the inner Galaxy, is higher than previously thought. In this paper we evaluate the effect of the interstellar radiation field on the inverse Compton emission of electrons accelerated in a supernova remnant located at different distances from the Galactic Centre. We show that contribution of optical and infra-red photons to the inverse Compton emission may exceed the contribution of cosmic microwave background and in some cases broaden the resulted {gamma}-ray spectrum. Additionally, we show that if a supernova remnant is located close to the Galactic Centre its {gamma}-ray spectrum will exhibit a ''universal'' cutoff at very high energies due to the Klein-Nishina effect and not due to the cut-off of the electron spectrum. As an example, we apply our calculations to the supernova remnants RX J1713.7-3946 and G0.9+0.1 recently observed by HESS.

  10. Testing the dark matter interpretation of the PAMELA excess through measurements of the galactic diffuse emission

    SciTech Connect

    Regis, Marco; Ullio, Piero

    2009-08-15

    We propose to test the dark matter (DM) interpretation of the positron excess observed by the PAMELA cosmic-ray (CR) detector through the identification of a Galactic diffuse gamma-ray component associated to DM-induced prompt and radiative emission. The goal is to present an analysis based on minimal sets of assumptions and extrapolations with respect to locally testable or measurable quantities. We discuss the differences between the spatial and spectral features for the DM-induced components (with an extended, possibly spherical, source function) and those for the standard CR contribution (with sources confined within the stellar disc), and propose to focus on intermediate and large latitudes. We address the dependence of the signal to background ratio on the model adopted to describe the propagation of charged CRs in the Galaxy, and find that, in general, the DM-induced signal can be detected by the Fermi Gamma-ray Space Telescope at energies above 100 GeV. An observational result in agreement with the prediction from standard CR components only, would imply very strong constraints on the DM interpretation of the PAMELA excess. On the other hand, if an excess in the diffuse emission above 100 GeV is identified, the angular profile for such emission would allow for a clean disentanglement between the DM interpretation and astrophysical explanations proposed for the PAMELA excess. We also compare to the radiative diffuse emission at lower frequencies, sketching, in particular, the detection prospects at infrared frequencies with the Planck satellite.

  11. Fermi-LAT Observations of High-Energy Gamma-Ray Emission toward the Galactic Center

    NASA Astrophysics Data System (ADS)

    Ajello, M.; Albert, A.; Atwood, W. B.; Barbiellini, G.; Bastieri, D.; Bechtol, K.; Bellazzini, R.; Bissaldi, E.; Blandford, R. D.; Bloom, E. D.; Bonino, R.; Bottacini, E.; Brandt, T. J.; Bregeon, J.; Bruel, P.; Buehler, R.; Buson, S.; Caliandro, G. A.; Cameron, R. A.; Caputo, R.; Caragiulo, M.; Caraveo, P. A.; Cecchi, C.; Chekhtman, A.; Chiang, J.; Chiaro, G.; Ciprini, S.; Cohen-Tanugi, J.; Cominsky, L. R.; Conrad, J.; Cutini, S.; D'Ammando, F.; de Angelis, A.; de Palma, F.; Desiante, R.; Di Venere, L.; Drell, P. S.; Favuzzi, C.; Ferrara, E. C.; Fusco, P.; Gargano, F.; Gasparrini, D.; Giglietto, N.; Giommi, P.; Giordano, F.; Giroletti, M.; Glanzman, T.; Godfrey, G.; Gomez-Vargas, G. A.; Grenier, I. A.; Guiriec, S.; Gustafsson, M.; Harding, A. K.; Hewitt, J. W.; Hill, A. B.; Horan, D.; Jogler, T.; Jóhannesson, G.; Johnson, A. S.; Kamae, T.; Karwin, C.; Knödlseder, J.; Kuss, M.; Larsson, S.; Latronico, L.; Li, J.; Li, L.; Longo, F.; Loparco, F.; Lovellette, M. N.; Lubrano, P.; Magill, J.; Maldera, S.; Malyshev, D.; Manfreda, A.; Mayer, M.; Mazziotta, M. N.; Michelson, P. F.; Mitthumsiri, W.; Mizuno, T.; Moiseev, A. A.; Monzani, M. E.; Morselli, A.; Moskalenko, I. V.; Murgia, S.; Nuss, E.; Ohno, M.; Ohsugi, T.; Omodei, N.; Orlando, E.; Ormes, J. F.; Paneque, D.; Pesce-Rollins, M.; Piron, F.; Pivato, G.; Porter, T. A.; Rainò, S.; Rando, R.; Razzano, M.; Reimer, A.; Reimer, O.; Ritz, S.; Sánchez-Conde, M.; Saz Parkinson, P. M.; Sgrò, C.; Siskind, E. J.; Smith, D. A.; Spada, F.; Spandre, G.; Spinelli, P.; Suson, D. J.; Tajima, H.; Takahashi, H.; Thayer, J. B.; Torres, D. F.; Tosti, G.; Troja, E.; Uchiyama, Y.; Vianello, G.; Winer, B. L.; Wood, K. S.; Zaharijas, G.; Zimmer, S.

    2016-03-01

    The Fermi Large Area Telescope (LAT) has provided the most detailed view to date of the emission toward the Galactic center (GC) in high-energy γ-rays. This paper describes the analysis of data taken during the first 62 months of the mission in the energy range 1-100 GeV from a 15° × 15° region about the direction of the GC. Specialized interstellar emission models (IEMs) are constructed to enable the separation of the γ-ray emissions produced by cosmic ray particles interacting with the interstellar gas and radiation fields in the Milky Way into that from the inner ˜1 kpc surrounding the GC, and that from the rest of the Galaxy. A catalog of point sources for the 15° × 15° region is self-consistently constructed using these IEMs: the First Fermi-LAT Inner Galaxy Point Source Catalog (1FIG). The spatial locations, fluxes, and spectral properties of the 1FIG sources are presented, and compared with γ-ray point sources over the same region taken from existing catalogs. After subtracting the interstellar emission and point-source contributions a residual is found. If templates that peak toward the GC are used to model the positive residual the agreement with the data improves, but none of the additional templates tried account for all of its spatial structure. The spectrum of the positive residual modeled with these templates has a strong dependence on the choice of IEM.

  12. Development of the Model of Galactic Interstellar Emission for Standard Point-source Analysis of Fermi Large Area Telescope Data

    NASA Astrophysics Data System (ADS)

    Acero, F.; Ackermann, M.; Ajello, M.; Albert, A.; Baldini, L.; Ballet, J.; Barbiellini, G.; Bastieri, D.; Bellazzini, R.; Bissaldi, E.; Bloom, E. D.; Bonino, R.; Bottacini, E.; Brandt, T. J.; Bregeon, J.; Bruel, P.; Buehler, R.; Buson, S.; Caliandro, G. A.; Cameron, R. A.; Caragiulo, M.; Caraveo, P. A.; Casandjian, J. M.; Cavazzuti, E.; Cecchi, C.; Charles, E.; Chekhtman, A.; Chiang, J.; Chiaro, G.; Ciprini, S.; Claus, R.; Cohen-Tanugi, J.; Conrad, J.; Cuoco, A.; Cutini, S.; D’Ammando, F.; de Angelis, A.; de Palma, F.; Desiante, R.; Digel, S. W.; Di Venere, L.; Drell, P. S.; Favuzzi, C.; Fegan, S. J.; Ferrara, E. C.; Focke, W. B.; Franckowiak, A.; Funk, S.; Fusco, P.; Gargano, F.; Gasparrini, D.; Giglietto, N.; Giordano, F.; Giroletti, M.; Glanzman, T.; Godfrey, G.; Grenier, I. A.; Guiriec, S.; Hadasch, D.; Harding, A. K.; Hayashi, K.; Hays, E.; Hewitt, J. W.; Hill, A. B.; Horan, D.; Hou, X.; Jogler, T.; Jóhannesson, G.; Kamae, T.; Kuss, M.; Landriu, D.; Larsson, S.; Latronico, L.; Li, J.; Li, L.; Longo, F.; Loparco, F.; Lovellette, M. N.; Lubrano, P.; Maldera, S.; Malyshev, D.; Manfreda, A.; Martin, P.; Mayer, M.; Mazziotta, M. N.; McEnery, J. E.; Michelson, P. F.; Mirabal, N.; Mizuno, T.; Monzani, M. E.; Morselli, A.; Nuss, E.; Ohsugi, T.; Omodei, N.; Orienti, M.; Orlando, E.; Ormes, J. F.; Paneque, D.; Pesce-Rollins, M.; Piron, F.; Pivato, G.; Rainò, S.; Rando, R.; Razzano, M.; Razzaque, S.; Reimer, A.; Reimer, O.; Remy, Q.; Renault, N.; Sánchez-Conde, M.; Schaal, M.; Schulz, A.; Sgrò, C.; Siskind, E. J.; Spada, F.; Spandre, G.; Spinelli, P.; Strong, A. W.; Suson, D. J.; Tajima, H.; Takahashi, H.; Thayer, J. B.; Thompson, D. J.; Tibaldo, L.; Tinivella, M.; Torres, D. F.; Tosti, G.; Troja, E.; Vianello, G.; Werner, M.; Wood, K. S.; Wood, M.; Zaharijas, G.; Zimmer, S.

    2016-04-01

    Most of the celestial γ rays detected by the Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope originate from the interstellar medium when energetic cosmic rays interact with interstellar nucleons and photons. Conventional point-source and extended-source studies rely on the modeling of this diffuse emission for accurate characterization. Here, we describe the development of the Galactic Interstellar Emission Model (GIEM), which is the standard adopted by the LAT Collaboration and is publicly available. This model is based on a linear combination of maps for interstellar gas column density in Galactocentric annuli and for the inverse-Compton emission produced in the Galaxy. In the GIEM, we also include large-scale structures like Loop I and the Fermi bubbles. The measured gas emissivity spectra confirm that the cosmic-ray proton density decreases with Galactocentric distance beyond 5 kpc from the Galactic Center. The measurements also suggest a softening of the proton spectrum with Galactocentric distance. We observe that the Fermi bubbles have boundaries with a shape similar to a catenary at latitudes below 20° and we observe an enhanced emission toward their base extending in the north and south Galactic directions and located within ∼4° of the Galactic Center.

  13. Neutrino-heated stars and broad-line emission from active galactic nuclei

    NASA Technical Reports Server (NTRS)

    Macdonald, James; Stanev, Todor; Biermann, Peter L.

    1991-01-01

    Nonthermal radiation from active galactic nuclei indicates the presence of highly relativistic particles. The interaction of these high-energy particles with matter and photons gives rise to a flux of high-energy neutrinos. In this paper, the influence of the expected high neutrino fluxes on the structure and evolution of single, main-sequence stars is investigated. Sequences of models of neutrino-heated stars in thermal equilibrium are presented for masses 0.25, 0.5, 0.8, and 1.0 solar mass. In addition, a set of evolutionary sequences for mass 0.5 solar mass have been computed for different assumed values for the incident neutrino energy flux. It is found that winds driven by the heating due to high-energy particles and hard electromagnetic radiation of the outer layers of neutrino-bloated stars may satisfy the requirements of the model of Kazanas (1989) for the broad-line emission clouds in active galactic nuclei.

  14. Interpreting Broad Double-Peaked Emission Lines in Active Galactic Nuclei

    NASA Technical Reports Server (NTRS)

    Halpern, Jules; Chen, Kaiyou

    1999-01-01

    The principal objectives of this project were to probe the inner regions of active galactic nuclei and to test general relativity in the strong-field limit. The approach takes advantage of broad atomic line emission observed from material deep in the potential well of an active galactic nucleus which contains key information as to the physics of the system. Line profiles in a wide range of wavebands from optical to X-ray have provided compelling evidence of the existence of a relativistic accretion disk around a supermassive black hole in a number of galaxies. The simplest model posits a geometrically thin disk in Keplerian orbit, with general relativistic effects in evidence. This model is the point of departure for the proposed work. We developed a high-performance numerical code to calculate photon trajectories in a Schwarzschild or Kerr metric and implemented it on parallel supercomputers. This code includes a general purpose ray tracer that calculates line profiles, light curves, and other observable quantities for a wide variety of emitter configurations. The versatility comes from the fact that the ray tracing algorithm does not depend on any symmetries regarding emitter locations. The speed comes from parallel implementation which enables us to sample hitherto unattainable volumes of disk model parameter space. During the period 1 March 1997 through 28 February 1998, two papers, supported in whole or in part by this grant, were published in refereed journals. They are reproduced in their entirety in the next two sections of this report.

  15. Probing B-mode foregrounds using estimators of isotropy violation

    NASA Astrophysics Data System (ADS)

    Rotti, Aditya; Huffenberger, Kevin

    2016-01-01

    We propose an isotropy-violation test as a diagnostic for foreground contamination to the Cosmic Microwave Background (CMB). Using polarized Planck 353 GHz data, we construct a map that indicates B-mode foreground dust emission, and helps to indicate the least contaminated lines-of-sight. This estimate, constructed in harmonic space via the bipolar spherical harmonic basis, has higher signal-to-noise than previous estimates of the dust B-mode power. We compare the contamination levels in several low-foreground regions of the sky, including the BICEP2 region. This information, and similar statistics, may be useful to ground-based CMB projects when planning observations to hunt for primordial B-mode signatures. Today, this tool can assess clean portions of the sky, but in the future it will allow null tests for foreground contamination in claimed detections of primordial B-modes.

  16. A multiwavelength study of the Carlson-Henize sample of early-type Galactic extreme emission-line stars

    NASA Technical Reports Server (NTRS)

    Shore, Steven N.; Brown, Douglas N.; Bopp, B. W.; Robinson, C. R.; Sanduleak, N.

    1990-01-01

    A UV, optical, and radio study of nine early spectral type extreme emission-line Galactic stars from the Carlson and Henize (1979) sample is presented. He 3-407 and He 3-1482 appear to be analogs of the massive evolved B(e) and luminous blue variable stars of the Magellanic Clouds. The sample appears to be confined to a narrow range in spectral type from about B0 to B6. Most of the observed stars do not show strong N emission, with the striking exception of He 3-1482, and these Galactic stars may not have mixed significant quantities of nitrogen into their envelopes, unlike many of the LMC supergiants, Most of the Galactic stars are considerably fainter than those in the Magellanic Clouds, although their spectral properties are quite similar.

  17. Infrared emission from tidal disruption events - probing the pc-scale dust content around galactic nuclei

    NASA Astrophysics Data System (ADS)

    Lu, Wenbin; Kumar, Pawan; Evans, Neal J.

    2016-05-01

    Recent UV-optical surveys have been successful in finding tidal disruption events (TDEs), in which a star is tidally disrupted by a supermassive black hole (BH). These TDEs release a huge amount of radiation energy Erad ˜ 1051-1052 erg into the circum-nuclear medium. If the medium is dusty, most of the radiation energy will be absorbed by dust grains within ˜1 pc from the BH and re-radiated in the infrared. We calculate the dust emission light curve from a 1D radiative transfer model, taking into account the time-dependent heating, cooling and sublimation of dust grains. We show that the dust emission peaks at 3-10 μm and has typical luminosities between 1042 and 1043 erg s-1 (with sky covering factor of dusty clouds ranging from 0.1 to 1). This is detectable by current generation of telescopes. In the near future, James Webb Space Telescope will be able to perform photometric and spectroscopic measurements, in which silicate or polycyclic aromatic hydrocarbon features may be found. Dust grains are non-spherical and may be aligned with the magnetic field, so the dust emission may be significantly polarized. Observations at rest-frame wavelength ≥ 2 μm have only been reported from two TDE candidates, SDSS J0952+2143 and SwiftJ1644+57. Although consistent with the dust emission from TDEs, the mid-infrared fluxes of the two events may be from other sources. Long-term monitoring is needed to draw a firm conclusion. We also point out two nearby TDE candidates (ASASSN-14ae and -14li) where the dust emission may be currently detectable. Detection of dust infrared emission from TDEs would provide information regarding the dust content and its distribution in the central pc of non-active galactic nuclei, which is hard to probe otherwise.

  18. Planck intermediate results. XXII. Frequency dependence of thermal emission from Galactic dust in intensity and polarization

    NASA Astrophysics Data System (ADS)

    Planck Collaboration; Ade, P. A. R.; Alves, M. I. R.; Aniano, G.; Armitage-Caplan, C.; Arnaud, M.; Atrio-Barandela, F.; Aumont, J.; Baccigalupi, C.; Banday, A. J.; Barreiro, R. B.; Battaner, E.; Benabed, K.; Benoit-Lévy, A.; Bernard, J.-P.; Bersanelli, M.; Bielewicz, P.; Bock, J. J.; Bond, J. R.; Borrill, J.; Bouchet, F. R.; Boulanger, F.; Burigana, C.; Cardoso, J.-F.; Catalano, A.; Chamballu, A.; Chiang, H. C.; Colombo, L. P. L.; Combet, C.; Couchot, F.; Coulais, A.; Crill, B. P.; Curto, A.; Cuttaia, F.; Danese, L.; Davies, R. D.; Davis, R. J.; de Bernardis, P.; de Zotti, G.; Delabrouille, J.; Désert, F.-X.; Dickinson, C.; Diego, J. M.; Donzelli, S.; Doré, O.; Douspis, M.; Dunkley, J.; Dupac, X.; Enßlin, T. A.; Eriksen, H. K.; Falgarone, E.; Finelli, F.; Forni, O.; Frailis, M.; Fraisse, A. A.; Franceschi, E.; Galeotta, S.; Ganga, K.; Ghosh, T.; Giard, M.; González-Nuevo, J.; Górski, K. M.; Gregorio, A.; Gruppuso, A.; Guillet, V.; Hansen, F. K.; Harrison, D. L.; Helou, G.; Hernández-Monteagudo, C.; Hildebrandt, S. R.; Hivon, E.; Hobson, M.; Holmes, W. A.; Hornstrup, A.; Jaffe, A. H.; Jaffe, T. R.; Jones, W. C.; Keihänen, E.; Keskitalo, R.; Kisner, T. S.; Kneissl, R.; Knoche, J.; Kunz, M.; Kurki-Suonio, H.; Lagache, G.; Lamarre, J.-M.; Lasenby, A.; Lawrence, C. R.; Leahy, J. P.; Leonardi, R.; Levrier, F.; Liguori, M.; Lilje, P. B.; Linden-Vørnle, M.; López-Caniego, M.; Lubin, P. M.; Macías-Pérez, J. F.; Maffei, B.; Magalhães, A. M.; Maino, D.; Mandolesi, N.; Maris, M.; Marshall, D. J.; Martin, P. G.; Martínez-González, E.; Masi, S.; Matarrese, S.; Mazzotta, P.; Melchiorri, A.; Mendes, L.; Mennella, A.; Migliaccio, M.; Miville-Deschênes, M.-A.; Moneti, A.; Montier, L.; Morgante, G.; Mortlock, D.; Munshi, D.; Murphy, J. A.; Naselsky, P.; Nati, F.; Natoli, P.; Netterfield, C. B.; Noviello, F.; Novikov, D.; Novikov, I.; Oppermann, N.; Oxborrow, C. A.; Pagano, L.; Pajot, F.; Paoletti, D.; Pasian, F.; Perdereau, O.; Perotto, L.; Perrotta, F.; Piacentini, F.; Pietrobon, D.; Plaszczynski, S.; Pointecouteau, E.; Polenta, G.; Popa, L.; Pratt, G. W.; Rachen, J. P.; Reach, W. T.; Reinecke, M.; Remazeilles, M.; Renault, C.; Ricciardi, S.; Riller, T.; Ristorcelli, I.; Rocha, G.; Rosset, C.; Roudier, G.; Rubiño-Martín, J. A.; Rusholme, B.; Salerno, E.; Sandri, M.; Savini, G.; Scott, D.; Spencer, L. D.; Stolyarov, V.; Stompor, R.; Sudiwala, R.; Sutton, D.; Suur-Uski, A.-S.; Sygnet, J.-F.; Tauber, J. A.; Terenzi, L.; Toffolatti, L.; Tomasi, M.; Tristram, M.; Tucci, M.; Valenziano, L.; Valiviita, J.; Van Tent, B.; Vielva, P.; Villa, F.; Wandelt, B. D.; Zacchei, A.; Zonca, A.

    2015-04-01

    Planck has mapped the intensity and polarization of the sky at microwave frequencies with unprecedented sensitivity. We use these data to characterize the frequency dependence of dust emission. We make use of the Planck 353 GHz I, Q, and U Stokes maps as dust templates, and cross-correlate them with the Planck and WMAP data at 12 frequencies from 23 to 353 GHz, over circular patches with 10° radius. The cross-correlation analysis is performed for both intensity and polarization data in a consistent manner. The results are corrected for the chance correlation between the templates and the anisotropies of the cosmic microwave background. We use a mask that focuses our analysis on the diffuse interstellar medium at intermediate Galactic latitudes. We determine the spectral indices of dust emission in intensity and polarization between 100 and 353 GHz, for each sky patch. Both indices are found to be remarkably constant over the sky. The mean values, 1.59 ± 0.02 for polarization and 1.51 ± 0.01 for intensity, for a mean dust temperature of 19.6 K, are close, but significantly different (3.6σ). We determine the mean spectral energy distribution (SED) of the microwave emission, correlated with the 353 GHz dust templates, by averaging the results of the correlation over all sky patches. We find that the mean SED increases for decreasing frequencies at ν< 60 GHz for both intensity and polarization. The rise of the polarization SED towards low frequencies may be accounted for by a synchrotron component correlated with dust, with no need for any polarization of the anomalous microwave emission. We use a spectral model to separate the synchrotron and dust polarization and to characterize the spectral dependence of the dust polarization fraction. The polarization fraction (p) of the dust emission decreases by (21 ± 6)% from 353 to 70 GHz. We discuss this result within the context of existing dust models. The decrease in p could indicate differences in polarization

  19. HCO emission toward the X-ray reflexion nebula Sgr B2 in the Galactic Center

    NASA Astrophysics Data System (ADS)

    Armijos Abendaño, Jairo

    The Galactic Center (GC) with its relative proximity (˜8.5 Kpc) is an excellent laboratory to study physical processes in a galactic nucleus with an incomparable high angular resolution. The GC hosts a supermassive black hole, Sgr A*, with a mass of ˜4×10(6) M⊙. The interstellar medium in the GC reveal a harsh environment since it is affected by large scale shocks, star formation activity and high energy phenomena. Furthermore, time-variability of X-ray emission is observed toward the molecular cloud complexes of Sgr A and Sgr B2 located in the GC. To explain this time-variability the X-ray reflection nebula scenario has been proposed. This scenario suggests that an enhanced activity of Sgr A* occurred ˜100 years ago, generating a huge X-ray flare that illuminated both cloud complexes in the GC. It is believed that HCO increases its abundance in Photo-Dominated Regions (PDRs) and X-ray Dominated Regions (XDRs). Furthermore, the Fe Kalpha line at 6.4 keV is an excellent tracer of XDRs. This line is produced by fluorescence when X-rays and/or high energy particles (>7.1 keV) interact with neutral or partially ionized iron atoms. The Sgr B2 complex hosts a large amount of regions with ionized hydrogen (HII regions) by UV radiation from nearby stars. These HII regions should illuminate a large number of PDRs in the environment of Sgr B2. Thus, the Sgr B2 complex is unique since PDRs and XDRs can clearly be resolved with the angular resolutions achieved by using actual single dish radio telescopes. HCO observations at 3 mm wavelengths were obtained with the IRAM 30 meter telescope at Pico Veleta (Spain) in 2006. The general aim of this work is to study the spatial distribution of the HCO(1-0) emission toward a 36x32 pc(2) region of the Sgr B2 complex in order to disentangle if this molecule is preferentially synthesized toward PDRs or/and XDRs. We found a good correlation between the HCO(1-0) emission and the Fe Kalpha line emission rather than the emission from

  20. GALPROP Code for Galactic Cosmic Ray Propagation and Associated Photon Emissions

    NASA Astrophysics Data System (ADS)

    Moskalenko, Igor; GALPROP Team

    2013-06-01

    Research in many areas of modern physics such as, e.g., indirect searches for dark matter and particle acceleration in supernova remnant shocks rely heavily on studies of cosmic rays (CRs) and associated diffuse emissions (radio, microwave, X-rays, gamma rays). The numerical Galactic CR propagation code GALPROP has been shown to reproduce simultaneously observational data of many kinds related to CR origin and propagation. We report on the latest updates of GALPROP, development of WebRun, a service to the scientific community enabling easy use of the GALPROP code via web browsers, and a library of evaluated isotopic production cross sections. We also report the results of a full Bayesian analysis of propagation parameters using nested sampling and Markov Chain Monte Carlo methods.

  1. X-ray absorption/emission line spectroscopy of the Galactic hot gaseous halo

    NASA Astrophysics Data System (ADS)

    Wang, Daniel

    2016-04-01

    There is an ongoing debate as to whether or not the Milky Way is surrounded by a large-scale, massive corona. Vastly different conclusions as to its extent and mass have been drawn from existing studies based on X-ray absorption and/or emission line spectroscopy. I will discuss my assessment of this issue, focusing on various uncertainties and potential problems in the present data, analyses, results, and interpretations.In particular, I will examine how different assumptions about the temperature distribution of the corona affect the inference of its physical scale. I will also discuss the external perspectives of galactic coronae obtained form observing nearby highly-inclined disk galaxies.

  2. Far-infrared forbidden O III line emission from the galactic center

    NASA Technical Reports Server (NTRS)

    Watson, D. M.; Storey, J. W. V.; Townes, C. H.; Haller, E. E.

    1980-01-01

    The forbidden O III 51.8 micron fine-structure line has been detected in Sgr A West. It appears that the emission arises from the same compact clouds within the central parsec of the Galaxy which are observed in forbidden Ne II. The line intensity is used to derive an effective temperature of 32,000-40,000 K for the radiation field that ionizes the clouds. An upper limit is also reported for the forbidden O III 88.4 micron fine-structure line in Sgr A West. From this upper limit, one can conclude that the average electron density outside the known ionized clouds and within 30 arcsec of the galactic center is less than 40 per cu cm.

  3. Searching for OH maser emission towards the MIPSGAL compact Galactic bubbles

    NASA Astrophysics Data System (ADS)

    Ingallinera, A.; Trigilio, C.; Leto, P.; Umana, G.; Buemi, C.; Cerrigone, L.; Agliozzo, C.

    2015-11-01

    We conducted radio observations searching for OH 18-cm maser emission from a sample of 169 unclassified MIPSGAL compact Galactic bubbles. These sources are thought to be the circumstellar envelopes of different kinds of evolved stars. Our observations were aimed at shedding light on the nature of MIPSGAL bubbles, since their characterization is a fundamental aid for the development of accurate physical models of stellar and Galaxy evolution. The maser emission is observationally linked to the last stages of the life of low- and intermediate-mass stars, which may constitute a significant fraction of the MIPSGAL bubbles. In particular OH masers are usually observed towards post-asymptotic giant branch (post-AGB) stars. Our observations were performed with the Green Bank Telescope and, for each source, produced spectra around the four OH 18-cm transitions. The observations were compared with archive interferometer data in order to exclude possible contamination from nearby sources. The main result is that the OH maser emission is not a common feature among the MIPSGAL bubbles, with only one certain detection. We conclude that among the MIPSGAL bubbles the post-AGB stars could be very rare.

  4. Relativistic Iron Emission and Disk Reflection in Galactic Microquasar XTE J1748-288

    NASA Technical Reports Server (NTRS)

    Miller, J. M.; Fox, D. W.; DiMatteo, T.; Wijnands, R.; Belloni, T.; Pooley, D.; Kouveliotou, C.; Lewin, W. H. G.

    2001-01-01

    We report evidence for an Fe K-alpha fluorescence line feature and disk reflection in the very high, high-, and low-state X-ray spectra of the Galactic microquasar XTE J1748 - 288 during its 1998 June outburst. Spectral analyses are made on data gathered throughout the outburst by the Rossi X-Ray Timing Explorer Proportional Counter Array. Gaussian line, relativistic disk emission line, and ionized disk reflection models are fitted to the data. In the very high state the line profile appears strongly redshifted, consistent with disk emission from the innermost stable orbits around a maximally rotating Kerr black hole. In the high state the line profile is less redshifted and increasingly prominent. The low-state line profile is very strong (approx. 0.5 keV equivalent width) and centered at 6.7 +/- 0.10 keV; disk line emission model fits indicate that the inner edge of the disk fluctuates between approx. 20R(sub g) and - approx. 100R(sub g) in this state. The disk reflection fraction is traced through the outburst; reflection from an ionized disk is preferred in the very high and high states, and reflection from a relatively neutral disk is preferred in the low state. We discuss the implications of our findings for the binary system dynamics and accretion flow geometry in XTE J1748 - 288.

  5. Relativistic Iron Emission and Disk Reflection in Galactic Microquasar XTE J1748-288

    NASA Technical Reports Server (NTRS)

    Miller, J. M.; Fox, D. W.; Matteo, T. DI; Wijnands, R.; Belloni, T.; Pooley, D.; Kouveliotou, C.; Lewin, W. H. G.

    2001-01-01

    We report evidence for an Fe K(alpha) fluorescence line feature and disk reflection in the very high, high-, and low-state X-ray spectra of the Galactic microquasar XTE J1748-288 during its 1998 June outburst. Spectral analyses are made on data gathered throughout the outburst by the Rossi X-Ray Timing Explorer Proportional Counter Array. Gaussian line, relativistic disk emission line, and ionized disk reflection models are fitted to the data. In the very high state the line profile appears strongly redshifted, consistent with disk emission from the innermost stable orbits around a maximally rotating Kerr black hole. In the high state the line profile is less redshifted and increasingly prominent. The low-state line profile is very strong (approx. 0.5 keV equivalent width) and centered at 6.7 +/- 0.10 keV; disk line emission model fits indicate that the inner edge of the disk fluctuates between approx. 20Rg and approx. 100Rg in this state. The disk reflection fraction is traced through the outburst; reflection from an ionized disk is preferred in the very high and high states, and reflection from a relatively neutral disk is preferred in the low state. We discuss the implications of our findings for the binary system dynamics and accretion flow geometry in XTE J1748-288.

  6. Evidence for Intermediate Polars as the origin of the Galactic Center hard X-ray emission

    NASA Astrophysics Data System (ADS)

    Hailey, Charles James; NuSTAR Galactic Plane Survey Working Group

    2016-01-01

    Recently, NuSTAR has discovered an unresolved hard (20-40 keV) X-ray emission within the central 10 pc of the Galaxy, possibly indicating a large population of intermediate polars (IPs). Chandra and XMM-Newton measurements of both point sources and diffuse emission in the surrounding ~50 pc imply a population of magnetic CVs with white dwarf mass ~ 0.5 M⊙. We present NuSTAR broad-band (3-79 keV) spectroscopy of two nearby IPs (TV Columbae and IGR J17303-0601) as well as our investigation of various spectral models and previous X-ray observations. We argue that the observations of both the inner 10 pc and the surrounding 50 pc can be accounted for by IPs with mean white dwarf mass ~ 0.9 M⊙. We find that the lower mass derived by Chandra and XMM-Newton is an artifact of narrow energy band fitting, and the spectral features associated with these measurements naturally arise in a heavier IP population. We also discuss implications for the X-ray emission and source population in the Galactic ridge and bulge.

  7. THE BALDWIN EFFECT IN THE NARROW EMISSION LINES OF ACTIVE GALACTIC NUCLEI

    SciTech Connect

    Zhang, Kai; Wang, Ting-Gui; Dong, Xiao-Bo; Gaskell, C. Martin E-mail: twang@ustc.edu.cn E-mail: martin.gaskell@uv.cl

    2013-01-01

    The anti-correlations between the equivalent widths of emission lines and the continuum luminosity in active galactic nuclei (AGNs), known as the Baldwin effect, are well established for broad lines, but are less well studied for narrow lines. In this paper we explore the Baldwin effect of narrow emission lines over a wide range of ionization levels and critical densities using a large sample of broad-line, radio-quiet AGNs taken from Sloan Digital Sky Survey Data Release 4. These type 1 AGNs span three orders of magnitude in continuum luminosity. We show that most narrow lines show a similar Baldwin effect slope of about -0.2, while the significant deviations of the slopes for [N II] {lambda}6583, [O II] {lambda}3727, [Ne V] {lambda}3425, and the narrow component of H{alpha} can be explained by the influence of metallicity, star formation contamination, and possibly by the difference in the shape of the UV-optical continuum. The slopes do not show any correlation with either the ionization potential or the critical density. We show that a combination of 50% variations in continuum near 5100 A and a lognormal distribution of observed luminosity can naturally reproduce a constant Baldwin effect slope of -0.2 for all narrow lines. The variations of the continuum could be due to variability, intrinsic anisotropic emission, or an inclination effect.

  8. Removing Spectral Diagnostics of Galactic and Stellar X-Ray Emission from Charged Exchange Recombination

    NASA Technical Reports Server (NTRS)

    Wargelin, Brad

    2004-01-01

    Our research uses the electron beam ion trap (EBIT) at the Lawrence Livermore National Laboratory to study X-ray emission from the charge exchange (CX) of highly charged ions with neutral gases. The resulting data help to fill a void in existing experimental and theoretical understanding of this atomic physics process, and are needed to explain all or part of the observed X-ray emission from the soft X-ray background, stellar winds, the Galactic Center and Galactic Ridge, supernova ejecta, and photoionized nebulae. Appreciation of the astrophysical relevance of our work continues to grow with the publication of roughly a dozen papers in the past four years describing Chandra and XMM observations of geocoronal and heliospheric CX emission, the temporal variation of such emission and correlation with X-ray emission enhancements observed by ROSAT, the theoretical spatial distribution of that emission, and CX emission around other stars. A similar number of papers were also published during that time describing CX emission from planets and comets. We expect that the launch of ASTRSE2, with its second-generation XRS microcalo- (with 6-eV resolution), will reveal even more clearly the contributions of CX to astrophysical emission. In our EBIT work we collected CX spectra from such ions as H-like and He-like Ne, Ar, and Fe. Our early measurements were made with a high-purity Ge detector, but during the second year we began operation of the first-generation XRS microcalorimeter (a twin of the XRS on ASTRO-E) and greatly improved the resolution of our measurements from roughly 150 eV (FWHM) with the Ge detectors to 10 eV with the XRS. We found that saturation of the XRS counting apparatus, which we described in our proposal as a potential concern, is not a problem for studying CX. During the course of our research, we expanded the number of injection gases permitted by the LLNL safety team, purchased and eventually operated an atomic H source, and clearly demonstrated the

  9. The optical emission lines of type 1 X-ray bright Active Galactic Nuclei

    NASA Astrophysics Data System (ADS)

    La Mura, G.; Berton, M.; Ciroi, S.; Cracco, V.; Di Mille, F.; Rafanelli, P.

    2014-10-01

    A strong X-ray emission is one of the defining signatures of nuclear activity in galaxies. According to the Unified Model for Active Galactic Nuclei (AGN), both the X-ray radiation and the prominent broad emission lines, characterizing the optical and UV spectra of Type 1 AGNs, are originated in the innermost regions of the sources, close to the Super Massive Black Holes (SMBH), which power the central engine. Since the emission is concentrated in a very compact region (with typical size r⩽0.1 pc) and it is not possible to obtain resolved images of the source, spectroscopic studies of this radiation represent the only valuable key to constrain the physical properties of matter and its structure in the center of active galaxies. Based on previous studies on the physics of the Broad Line Region (BLR) and on the X-ray spectra of broad (FWHMHβ ⩾ 2000 km s-1) and narrow line (1000 km s-1 ⩽FWHMHβ ⩽ 2000 km s-1) emitting objects, it has been observed that the kinematic and ionization properties of matter close to the SMBHs are related together, and, in particular, that ionization is higher in narrow line sources. Here we report on the study of the optical and X-ray spectra of a sample of Type 1 AGNs, selected from the Sloan Digital Sky Survey (SDSS) database, within an upper redshift limit of z=0.35, and detected at X-ray energies. We present analysis of the broad emission line fluxes and profiles, as well as the properties of the X-ray continuum and Fe Kα emission and we use these parameters to assess the consistency of our current AGN understanding.

  10. COLLIMATION AND SCATTERING OF THE ACTIVE GALACTIC NUCLEUS EMISSION IN THE SOMBRERO GALAXY

    SciTech Connect

    Menezes, R. B.; Steiner, J. E.; Ricci, T. V.

    2013-03-10

    We present an analysis of a data cube of the central region of M104, the Sombrero galaxy, obtained with the GMOS-IFU of the Gemini-South telescope, and report the discovery of collimation and scattering of the active galactic nucleus (AGN) emission in the circumnuclear region of this galaxy. Analysis with PCA Tomography and spectral synthesis revealed the existence of collimation and scattering of the AGN featureless continuum and also of a broad component of the H{alpha} emission line. The collimation and scattering of this broad H{alpha} component was also revealed by fitting the [N II] {lambda}{lambda}6548, 6583 and H{alpha} emission lines as a sum of Gaussian functions. The spectral synthesis, together with a V-I image obtained with the Hubble Space Telescope, showed the existence of circumnuclear dust, which may cause the light scattering. We also identify a dusty feature that may be interpreted as a torus/disk structure. The existence of two opposite regions with featureless continuum (P.A. = -18 Degree-Sign {+-} 13 Degree-Sign and P.A. = 162 Degree-Sign {+-} 13 Degree-Sign ) along a direction perpendicular to the torus/disk (P.A. = 72 Degree-Sign {+-} 14 Degree-Sign ) suggests that this structure is approximately edge-on and collimates the AGN emission. The edge-on torus/disk also hides the broad-line region. The proposed scenario is compatible with the unified model and explains why only a weak broad component of the H{alpha} emission line is visible and also why many previous studies detected no broad H{alpha}. The technique used here proved to be an efficient method not only for detecting scattered light, but also for testing the unified model in low-luminosity AGNs.

  11. Discovery of SiO Band Emission from Galactic B[e] Supergiants

    NASA Astrophysics Data System (ADS)

    Kraus, M.; Oksala, M. E.; Cidale, L. S.; Arias, M. L.; Torres, A. F.; Borges Fernandes, M.

    2015-02-01

    B[e] supergiants (B[e]SGs) are evolved massive stars in a short-lived transition phase. During this phase, these objects eject large amounts of material, which accumulate in a circumstellar disk-like structure. The expelled material is typically dense and cool, providing the cradle for molecule and dust condensation and for a rich, ongoing chemistry. Very little is known about the chemical composition of these disks, beyond the emission from dust and CO revolving around the star on Keplerian orbits. As massive stars preserve an oxygen-rich surface composition throughout their life, other oxygen-based molecules can be expected to form. As SiO is the second most stable oxygen compound, we initiated an observing campaign to search for first-overtone SiO emission bands. We obtained high-resolution near-infrared L-band spectra for a sample of Galactic B[e]SGs with reported CO band emission. We clearly detect emission from the SiO first-overtone bands in CPD-52 9243 and indications for faint emission in HD 62623, HD 327083, and CPD-57 2874. From model fits, we find that in all these stars the SiO bands are rotationally broadened with a velocity lower than observed in the CO band forming regions, suggesting that SiO forms at larger distances from the star. Hence, searching for and analyzing these bands is crucial for studying the structure and kinematics of circumstellar disks, because they trace complementary regions to the CO band formation zone. Moreover, since SiO molecules are the building blocks for silicate dust, their study might provide insight in the early stage of dust formation. Based on observations collected with the ESO VLT Paranal Observatory under program 093.D-0248(A).

  12. Origin of the Galactic Disk 6.7 kev Line Emission

    NASA Technical Reports Server (NTRS)

    Churchwell, Ed

    1997-01-01

    The goal of this program was to determine if the extended FeXXV 6.7 kev line emission might possibly be produced and confined by the hot wind-shocked bubbles to accompany UC HII regions. The main result of this study are: (1) FeXXV is detected in the W3 complex, but at a level that could only explain a small fraction of the galactic disk emission if all UC HII regions emit at about the same intensity as the W3 complex; (2) Two X-ray sources are detected in W3. W3-X 1 coincides with the radio image of this region, but W3-X2 has no radio, optical, or infrared counterpart; (3) There is no evidence for variability of W3-X1 during the period of observations (approx, 40,000 sec); (4) The X-ray spectrum of W3-X1 has no emission shortward of 1 kev, it peaks at approx. 2 kev and show significant emission out to approx. 6 kev. No individual lines are resolved. There is currently no generally accepted theory for extended hard X-ray emission in HII regions. Perhaps the most significant discovery of this program has been the detection of extended hard X-rays and the realization that some entirely new processes must be invoked to understand this; and (5)A minimum (chi)(sup 2) fit of the spectrum implies a H absorbing column of N(sub H) approx, equals to 2.1 x 10(exp 22)/ cm, a temperature of the emitting plasma of 7 x 10(exp 7) K, and a luminosity of approx. equal to 10(33)erg/s.

  13. Dynamics and X-Ray Emission of a Galactic Superwind Interacting with Disk and Halo Gas

    NASA Astrophysics Data System (ADS)

    Suchkov, A. A.; Balsara, D. S.; Heckman, T. M.; Leitherer, C.

    1993-12-01

    There is a general agreement that the conspicuous extranuclear x-ray, optical-line, and radio-continuum emission of starbursts is associated with powerful galactic superwinds blowing from their centers. However, despite the significant advances in observational studies of superwinds, there is no consensus on the nature of the emitting material and even on the emission mechanisms themselves. This is to a great extent a consequence of a poor understanding of dynamical processes in the starburst superwind regions. To address this issue, we have conducted two-dimensional hydrodynamical simulations of galactic superwinds. While previous similar studies have used a single (disk) component to represent the ISM of the starburst galaxy, we analyse the interaction of the wind with a two-component disk--halo ambient interstellar medium. This two-component representation is argued to be crucial for adequate modelling of starbursts. The emphasis of this study is on the geometry and structure of the wind region and the x-ray emission arising in the wind material and the shocked gas in the disk and the halo of the galaxy. The simulation results have shown that a clear-cut bipolar wind can easily develop under a range of very different conditions. On the other hand, a complex `filamentary' structure associated with the entrained dense disk material is found to arise within the hot bubble blown out by the wind. The flow pattern within the bubble is dominated equally by the central biconic outflow and a system of whirling motions related to the origin and development of the `filaments'. The `filament' parameters make them a good candidate for optical-emission-line filamentary gas observed in starburst halos. We find that the history of mass and energy deposition in the starburst region of the galaxy is crucial for wind dynamics. A ``mild'' early wind, which arises as a result of the cumulative effect of stellar winds from massive stars, produces a bipolar vertical cavity in the disk

  14. Diffuse gamma-ray emission modeling near the Galactic Center and the 3 GeV excess

    NASA Astrophysics Data System (ADS)

    Albert, Andrea; Maleshev, Dmitry; Franckowiak, Anna; Tibaldo, Luigi; Fermi-LAT Collaboration

    2016-03-01

    Several groups have reported excess emission in gamma rays peaking around 3 GeV relative to expectations from conventional models for the interstellar emission in the Galactic Center (GC). We study the uncertainty of the excess emission in Pass 8 Fermi-LAT data due to modeling of the various emission components in that direction. In particular, we quantify the uncertainties on the excess by refitting with several GALPROP models of Galactic diffuse emission, an alternative distribution of gas along the line of sight based on starlight extinction data, a model of the Fermi bubbles at low latitudes, and including templates for additional sources of cosmic-ray electrons near the GC. In all models that we have tested the excess emission remains significant. The origin of the excess is currently uncertain. To test the robustness of a dark-matter interpretation, we perform fits in controls regions along the Galactic Plane. The uncertainties from our fits in control regions have a similar relative size as the excess in the GC. Therefore a non-dark-matter explanation cannot be ruled out and we consequently set limits on the dark matter annihilation cross section.

  15. An XMM-Newton Survey of the Soft X-Ray Background. III. The Galactic Halo X-Ray Emission

    NASA Astrophysics Data System (ADS)

    Henley, David B.; Shelton, Robin L.

    2013-08-01

    We present measurements of the Galactic halo's X-ray emission for 110 XMM-Newton sight lines selected to minimize contamination from solar wind charge exchange emission. We detect emission from few million degree gas on ~4/5 of our sight lines. The temperature is fairly uniform (median = 2.22 × 106 K, interquartile range = 0.63 × 106 K), while the emission measure and intrinsic 0.5-2.0 keV surface brightness vary by over an order of magnitude (~(0.4-7) × 10-3 cm-6 pc and ~(0.5-7) × 10-12 erg cm-2 s-1 deg-2, respectively, with median detections of 1.9 × 10-3 cm-6 pc and 1.5 × 10-12 erg cm-2 s-1 deg-2, respectively). The high-latitude sky contains a patchy distribution of few million degree gas. This gas exhibits a general increase in emission measure toward the inner Galaxy in the southern Galactic hemisphere. However, there is no tendency for our observed emission measures to decrease with increasing Galactic latitude, contrary to what is expected for a disk-like halo morphology. The measured temperatures, brightnesses, and spatial distributions of the gas can be used to place constraints on models for the dominant heating sources of the halo. We provide some discussion of such heating sources, but defer comparisons between the observations and detailed models to a later paper.

  16. The Subarcsecond Mid-infrared View of Local Active Galactic Nuclei. III. Polar Dust Emission

    NASA Astrophysics Data System (ADS)

    Asmus, D.; Hönig, S. F.; Gandhi, P.

    2016-05-01

    Recent mid-infrared (MIR) interferometric observations have shown that in a few active galactic nuclei (AGNs) the bulk of the infrared emission originates from the polar region above the putative torus, where only a little dust should be present. Here, we investigate whether such strong polar dust emission is common in AGNs. Out of 149 Seyferts in the MIR atlas of local AGNs, 21 show extended MIR emission on single-dish images. In 18 objects, the extended MIR emission aligns with the position angle (PA) of the system axis, established by [O iii], radio, polarization, and maser-based PA measurements. The relative amount of resolved MIR emission is at least 40% and scales with the [O iv] fluxes, implying a strong connection between the extended continuum and [O iv] emitters. These results together with the radio-quiet nature of the Seyferts support the scenario that the bulk of MIR emission is emitted by dust in the polar region and not by the torus, which would demand a new paradigm for the infrared emission structure in AGNs. The current low detection rate of polar dust in the AGNs of the MIR atlas is explained by the lack of sufficient high-quality MIR data and the requirements on the orientation, strength of narrow-line region, and distance of the AGNs. The James Webb Space Telescope will enable much deeper nuclear MIR studies with comparable angular resolution, allowing us to resolve the polar emission and surroundings in most of the nearby AGNs. Based on European Southern Observatory (ESO) observing programmes 60.A-9242, 074.A-9016, 075.B-0182, 075.B-0621, 075.B-0631, 075.B-0727, 075.B-0791, 075.B-0844, 076.B-0194, 076.B-0468, 076.B-0599, 076.B-0621, 076.B-0656, 076.B-0696, 076.B-0743, 077.B-0060, 077.B-0135, 077.B-0137, 077.B-0728, 078.B-0020, 078.B-0173, 078.B-0255, 078.B-0303, 080.B-0240, 080.B-0860, 081.B-0182, 082.B-0299, 083.B-0239, 083.B-0452, 083.B-0536, 083.B-0592, 084.B-0366, 084.B-0606, 084.B-0974, 085.B-0251, 085.B-0639, 086.B-0242, 086.B-0257, 086

  17. Statistical analysis of the cosmic microwave background: Power spectra and foregrounds

    NASA Astrophysics Data System (ADS)

    O'Dwyer, Ian J.

    2005-11-01

    In this thesis I examine some of the challenges associated with analyzing Cosmic Microwave Background (CMB) data and present a novel approach to solving the problem of power spectrum estimation, which is called MAGIC (MAGIC Allows Global Inference of Covariance). In light of the computational difficulty of a brute force approach to power spectrum estimation, I review several approaches which have been applied to the problem and show an example application of such an approximate method to experimental CMB data from the Background Emission Anisotropy Scanning Telescope (BEAST). I then introduce MAGIC, a new approach to power spectrum estimation; based on a Bayesian statistical analysis of the data utilizing Gibbs Sampling. I demonstrate application of this method to the all-sky Wilkinson Microwave Anistropy Probe WMAP data. The results are in broad agreement with those obtained originally by the WMAP team. Since MAGIC generates a full description of each C l it is possible to examine several issues raised by the best-fit WMAP power spectrum, for example the perceived lack of power at low ℓ. It is found that the distribution of C ℓ's at low l are significantly non-Gaussian and, based on the exact analysis presented here, the "low quadrupole issue" can be attributed to a statistical fluctuation. Finally, I examine the effect of Galactic foreground contamination on CMB experiments and describe the principle foregrounds. I show that it is possible to include the foreground components in a self-consistent fashion within the statistical framework of MAGIC and give explicit examples of how this might be achieved. Foreground contamination will become an increasingly important issue in CMB data analysis and the ability of this new algorithm to produce an exact power spectrum in a computationally feasible time, coupled with the foreground component separation and removal is an exciting development in CMB data analysis. When considered with current algorithmic developments

  18. NO EVIDENCE FOR A SYSTEMATIC Fe II EMISSION LINE REDSHIFT IN TYPE 1 ACTIVE GALACTIC NUCLEI

    SciTech Connect

    Sulentic, Jack W.; Marziani, Paola; Zamfir, Sebastian; Meadows, Zachary A. E-mail: paola.marziani@oapd.inaf.it E-mail: Zachary.A.Meadows@uwsp.edu

    2012-06-10

    We test the recent claim by Hu et al. that Fe II emission in type 1 active galactic nuclei shows a systematic redshift relative to the local source rest frame and broad-line H{beta}. We compile high signal-to-noise median composites using Sloan Digital Sky Survey spectra from both the Hu et al. sample and our own sample of the 469 brightest DR5 spectra. Our composites are generated in bins of FWHM H{beta} and Fe II strength as defined in our 4D Eigenvector 1 formalism. We find no evidence for a systematic Fe II redshift and consistency with previous assumptions that Fe II shift and width (FWHM) follow H{beta} shift and FWHM in virtually all sources. This result is consistent with the hypothesis that Fe II emission (quasi-ubiquitous in type 1 sources) arises from a broad-line region with geometry and kinematics the same as that producing the Balmer lines.

  19. The Galactic disc distribution of planetary nebulae with warm dust emission features - II

    NASA Astrophysics Data System (ADS)

    Casassus, S.; Roche, P. F.

    2001-02-01

    We address the question of whether the distribution of warm-dust compositions in IR-bright Galactic disc PNe (Paper I, Casassus et al.) can be linked to the underlying stellar population. The PNe with warm dust emission represent a homogeneous population, which is presumably young and minimally affected by a possible dependence of PN lifetime on progenitor mass. The sample in Paper I thus allows testing of the predictions of single-star evolution, through a comparison with synthetic distributions and under the assumption that tip-of-the-AGB and PN statistics are similar. We construct a schematic model for AGB evolution (adapted from Groenewegen & de Jong), the free parameters of which are calibrated with the luminosity function (LF) of C stars in the LMC, the initial-final mass relation and the range of PN compositions. The observed metallicity gradient and distribution of star-forming regions with Galactocentric radius (Bronfman et al.) allow us to synthesize the Galactic disc PN progenitor population. We find that the fraction of O-rich PNe, f(0), is a tight constraint on AGB parameters. For our best model, a minimum PN progenitor mass Mmin=1 M⊙ predicts that about 50per cent of all young PNe should be O-rich, compared with an observed fraction of 22per cent; thus Mmin=1.2 M⊙, at a 2σ confidence level Mmin=1.3 M⊙ at 1σ). By contrast, current AGB models for single stars can account neither for the continuous range of N enrichment (Leisy & Dennefeld) nor for the observation that the majority of very C-rich PNe have Peimbert type I (Paper I). f(O) is thus an observable quantity much easier to model. The decrease in f(O) with Galactocentric radius, as reported in Paper I, is a strong property of the synthetic distribution, independent of Mmin. This trend reflects the sensitivity of the surface temperature of AGB stars and of the core mass at the first thermal pulse to the Galactic metallicity gradient.

  20. The Hubble Space Telescope Quasar Absorption Line Key Project. 10: Galactic H I 21 centimeter emission toward 143 quasars and active Galactic nuclei

    NASA Technical Reports Server (NTRS)

    Lockman, Felix J.; Savage, Blair D.

    1995-01-01

    Sensitive H I 21 cm emission line spectra have been measured for the directions to 143 quasars and active galactic nuclei (AGNs) chosen from the observing lists for the Hubble Space Telescope (HST) Quasar Absorption Line Key Project. Narrow-band and wide-band data were obtained with the National Radio Astronomy Observatory (NRAO) 43 m radio telescope for each object. The narrow-band data have a velocity resolution of 1 km/s, extend from -220 to +170 km/s, and are corrected for stray 21 cm radiation. The wide-band data have a resolution of 4 km/s and extend from -1000 to +1000 km/s. The data are important for the interpretation of ultraviolet absorption lines near zero redshift in Key Project spectra. Twenty-two percent of the quasars lie behind Galactic high-velocity H I clouds with absolute value of V(sub LSR) greater than 100 km/s whose presence can increase the equivalent width of interstellar absorption lines significantly. This paper contains the emission spectra and measures of the H I velocities and column densities along the sight line to each quasar. We discuss how the measurements can be used to estimate the visual and ultraviolet extinction toward each quasar and to predict the approximate strength of the strong ultraviolet resonance lines of neutral gas species in the HST Key Project spectra.

  1. IFU spectroscopy of 10 early-type galactic nuclei - III. Properties of the circumnuclear gas emission

    NASA Astrophysics Data System (ADS)

    Ricci, T. V.; Steiner, J. E.; Menezes, R. B.

    2015-08-01

    Many early-type galaxies have ionized gas emission in their centres that extends to scales of ˜1 kpc. The majority of such objects are classified as low-ionization nuclear emission regions (LINERs), but the nature of their ionizing source is still not clear. The kinematics associated with these gaseous structures usually shows deviations from a pure rotational motion due to non-gravitational effects (e.g. outflows) or to non-axisymmetric potentials (e.g. bars or tri-axial systems). This is the third of a series of papers that describes a sample of 10 nearby (d < 30 Mpc) and massive (σ > 200 km s-1) early-type galaxies observed with the Gemini Multi-Object Spectrograph in Integral Field mode installed on the Gemini-South telescope. In Paper II, we performed spectral synthesis to subtract the stellar components from the data cubes of the sample galaxies in order to study their nuclear spectra. In this work, we analyse the circumnuclear gas emission (scales of ˜100 pc) of the sample galaxies and we compare the results with those obtained with Principal Component Analysis Tomography in Paper I. We detected circumnuclear gas emission in seven galaxies of the sample, all of them classified as LINERs. Pure gaseous discs are found in three galaxies. In two objects, gaseous discs are probably present, but their kinematics are affected by non-Keplerian motions. In one galaxy (IC 5181), we detected a spiral structure of gas that may be caused either by a non-axisymmetric potential or by an outflow together with a gaseous disc. In NGC 3136, an ionization bicone is present in addition to five compact structures with LINER-like emission. In galaxies with a gaseous disc, we found that ionizing photons emitted by an active galactic nucleus are not enough to explain the observed Hα flux along this structure. On the other hand, the Hα flux distribution and equivalent width along the direction perpendicular the gaseous disc suggest the presence of low-velocity ionized gas

  2. XMM-Newton Study of the Fe K Emission from Molecular Clouds in the Galactic Centre

    NASA Astrophysics Data System (ADS)

    Ponti, Gabriele; Terrier, R.; Goldwurm, A.; Belanger, G.; Trap, G.

    2010-03-01

    The study of the X-ray emission from the Galactic Centre (GC) Molecular Clouds (MC), within 15 arcmin from SgrA*, will be presented. We use XMM-Newton data (about 1.2 Ms of observation time) spanning about 8 years. The MC spectra show all the features characteristic of reflection: intense FeKα, with EW of about 0.7-1 keV, and the associated Kβ line; flat power law continuum and significant FeK edge. The diffuse lowly ionised FeK emission follows the MC distribution, nevertheless not all MC are FeK emitters. The long baseline monitoring allows the characterisation of the temporal evolution of the MC emission, showing a complex pattern of significant variations. In particular, we observe an apparent super-luminal motion of a light front illuminating a Molecular nebula. This might be due to a source outside the MC (such as SgrA* or a bright and long outburst of a X-ray binary), while it can not be due to low energy cosmic rays or a source located inside the cloud. We also observe a decrease of the X-ray emission from G0.11-0.11, behaviour similar to the one of SgrB2. The line intensities, clouds dimensions, columns densities and positions with respect to SgrA*, are consistent with being produced by the same SgrA* flare. The required high luminosity (about 1.5×1039 erg s-1) can hardly be produced by an binary system, while it is in agreement with a flare of SgrA* fading about 100 years ago. The low intensity of the FeK emission coming from the 50 and the 20 km s^-1 MC places an upper limit of 3×1035 erg s^-1 to the mean luminosity of SgrA* in the last 60-90 years. The FeK emission and variations from these MC might have been produced by a single flare of SgrA*.

  3. XMM-Newton Study of the Fe K Emission from Molecular Clouds in the Galactic Centre

    NASA Astrophysics Data System (ADS)

    Ponti, Gabriele; Terrier, R.; Goldwurm, A.; Belanger, G.; Trap, G.

    2010-02-01

    The study of the X-ray emission from the Galactic Centre (GC) Molecular Clouds (MC), within 15 arcmin from SgrA*, will be presented. We use XMM-Newton data (about 1.2 Ms of observation time) spanning about 8 years. The MC spectra show all the features characteristic of reflection: intense FeKα, with EW of about 0.7-1 keV, and the associated Kβ line; flat power law continuum and significant FeK edge. The diffuse lowly ionised FeK emission follows the MC distribution, nevertheless not all MC are FeK emitters. The long baseline monitoring allows the characterisation of the temporal evolution of the MC emission, showing a complex pattern of significant variations. In particular, we observe an apparent super-luminal motion of a light front illuminating a Molecular nebula. This might be due to a source outside the MC (such as SgrA* or a bright and long outburst of a X-ray binary), while it can not be due to low energy cosmic rays or a source located inside the cloud. We also observe a decrease of the X-ray emission from G0.11-0.11, behaviour similar to the one of SgrB2. The line intensities, clouds dimensions, columns densities and positions with respect to SgrA*, are consistent with being produced by the same SgrA* flare. The required high luminosity (about 1.5×1039 erg s-1) can hardly be produced by an binary system, while it is in agreement with a flare of SgrA* fading about 100 years ago. The low intensity of the FeK emission coming from the 50 and the 20 km s^-1 MC places an upper limit of 3×1035 erg s^-1 to the mean luminosity of SgrA* in the last 60-90 years. The FeK emission and variations from these MC might have been produced by a single flare of SgrA*.

  4. Revisiting the infrared spectra of active galactic nuclei with a new torus emission model

    NASA Astrophysics Data System (ADS)

    Fritz, J.; Franceschini, A.; Hatziminaoglou, E.

    2006-03-01

    We describe improved modelling of the emission by dust in a toroidal-like structure heated by a central illuminating source within active galactic nuclei (AGNs). We have chosen a simple but realistic torus geometry, a flared disc, and a dust grain distribution function including a full range of grain sizes. The optical depth within the torus is computed in detail taking into account the different sublimation temperatures of the silicate and graphite grains, which solves previously reported inconsistencies in the silicate emission feature in type 1 AGNs. We exploit this model to study the spectral energy distributions (SEDs) of 58 extragalactic (both type 1 and type 2) sources using archival optical and infrared data. We find that both AGN and starburst contributions are often required to reproduce the observed SEDs, although in a few cases they are very well fitted by a pure AGN component. The AGN contribution to the far-infrared luminosity is found to be higher in type 1 sources, with all the type 2 requiring a substantial contribution from a circumnuclear starburst. Our results appear in agreement with the AGN unified scheme, because the distributions of key parameters of the torus models turn out to be compatible for type 1 and type 2 AGNs. Further support to the unification concept comes from comparison with medium-resolution infrared spectra of type 1 AGNs by the Spitzer observatory, showing evidence for a moderate silicate emission around 10 μm, which our code reproduces. From our analysis we infer accretion flows in the inner nucleus of local AGNs characterized by high equatorial optical depths (AV~= 100), moderate sizes (Rmax < 100 pc) and very high covering factors (f~= 80 per cent) on average.

  5. Evidence for Intermediate Polars as the Origin of the Galactic Center Hard X-ray Emission

    NASA Astrophysics Data System (ADS)

    Hailey, Charles J.; Mori, Kaya; Perez, Kerstin; Canipe, Alicia M.; Hong, Jaesub; Tomsick, John A.; Boggs, Steven E.; Christensen, Finn E.; Craig, William W.; Fornasini, Francesca; Grindlay, Jonathan E.; Harrison, Fiona A.; Nynka, Melania; Rahoui, Farid; Stern, Daniel; Zhang, Shuo; Zhang, William W.

    2016-08-01

    Recently, unresolved hard (20–40 keV) X-ray emission has been discovered within the central 10 pc of the Galaxy, possibly indicating a large population of intermediate polars (IPs). Chandra and XMM-Newton measurements in the surrounding ∼50 pc imply a much lighter population of IPs with < {M}{{WD}}> ≈ 0.5{M}ȯ . Here we use broadband NuSTAR observations of two IPs: TV Columbae, which has a fairly typical but widely varying reported mass of {M}{{WD}}≈ 0.5–1.0{M}ȯ , and IGR J17303–0601, with a heavy reported mass of {M}{{WD}}≈ 1.0–1.2{M}ȯ . We investigate how varying spectral models and observed energy ranges influences estimated white dwarf mass. Observations of the inner 10 pc can be accounted for by IPs with < {M}{{WD}}> ≈ 0.9{M}ȯ , consistent with that of the CV population in general and the X-ray observed field IPs in particular. The lower mass derived by Chandra and XMM-Newton appears to be an artifact of narrow energy-band fitting. To explain the (unresolved) central hard X-ray emission (CHXE) by IPs requires an X-ray (2–8 keV) luminosity function (XLF) extending down to at least 5 × 1031 erg s‑1. The CHXE XLF, if extended to the surrounding ∼50 pc observed by Chandra and XMM-Newton, requires that at least ∼20%–40% of the ∼9000 point sources are IPs. If the XLF extends just a factor of a few lower in luminosity, then the vast majority of these sources are IPs. This is in contrast to recent observations of the Galactic ridge, where the bulk of the 2–8 keV emission is ascribed to non-magnetic CVs.

  6. INTERACTING GALACTIC NEUTRAL HYDROGEN FILAMENTS AND ASSOCIATED HIGH-FREQUENCY CONTINUUM EMISSION

    SciTech Connect

    Verschuur, Gerrit L.

    2013-05-10

    Galactic H I emission profiles in an area where several large-scale filaments at velocities ranging from -46 km s{sup -1} to 0 km s{sup -1} overlap were decomposed into Gaussian components. Eighteen families of components defined by similarities of center velocity and line width were identified and related to small-scale structure in the high-frequency continuum emission observed by the Wilkinson Microwave Anisotropy Probe spacecraft, as evidenced in the Internal Linear Combination (ILC) map of Hinshaw et al. When the center velocities of the Gaussian families, which summarize the properties of all the H I along the lines of sight in a given area, are used to focus on H I channel maps the phenomenon of close associations between H I and ILC peaks reported in previous papers is dramatically highlighted. Of particular interest, each of two pairs of H I peaks straddles a continuum peak. The previously hypothesized model for producing the continuum radiation involving free-free emission from electrons is re-examined in light of the new data. By choosing reasonable values for the parameters required to evaluate the model, the distance for associated H I-ILC features is of order 30-100 pc. No associated H{alpha} radiation is expected because the electrons involved exist throughout the Milky Way. The mechanism for clumping and separation of neutrals and electrons needs to be explored. It is concluded that the small-scale ILC structure originates in the local interstellar medium and not at cosmological distances.

  7. Evidence for Intermediate Polars as the Origin of the Galactic Center Hard X-ray Emission

    NASA Astrophysics Data System (ADS)

    Hailey, Charles J.; Mori, Kaya; Perez, Kerstin; Canipe, Alicia M.; Hong, Jaesub; Tomsick, John A.; Boggs, Steven E.; Christensen, Finn E.; Craig, William W.; Fornasini, Francesca; Grindlay, Jonathan E.; Harrison, Fiona A.; Nynka, Melania; Rahoui, Farid; Stern, Daniel; Zhang, Shuo; Zhang, William W.

    2016-08-01

    Recently, unresolved hard (20–40 keV) X-ray emission has been discovered within the central 10 pc of the Galaxy, possibly indicating a large population of intermediate polars (IPs). Chandra and XMM-Newton measurements in the surrounding ˜50 pc imply a much lighter population of IPs with < {M}{{WD}}> ≈ 0.5{M}ȯ . Here we use broadband NuSTAR observations of two IPs: TV Columbae, which has a fairly typical but widely varying reported mass of {M}{{WD}}≈ 0.5–1.0{M}ȯ , and IGR J17303–0601, with a heavy reported mass of {M}{{WD}}≈ 1.0–1.2{M}ȯ . We investigate how varying spectral models and observed energy ranges influences estimated white dwarf mass. Observations of the inner 10 pc can be accounted for by IPs with < {M}{{WD}}> ≈ 0.9{M}ȯ , consistent with that of the CV population in general and the X-ray observed field IPs in particular. The lower mass derived by Chandra and XMM-Newton appears to be an artifact of narrow energy-band fitting. To explain the (unresolved) central hard X-ray emission (CHXE) by IPs requires an X-ray (2–8 keV) luminosity function (XLF) extending down to at least 5 × 1031 erg s‑1. The CHXE XLF, if extended to the surrounding ˜50 pc observed by Chandra and XMM-Newton, requires that at least ˜20%–40% of the ˜9000 point sources are IPs. If the XLF extends just a factor of a few lower in luminosity, then the vast majority of these sources are IPs. This is in contrast to recent observations of the Galactic ridge, where the bulk of the 2–8 keV emission is ascribed to non-magnetic CVs.

  8. Discovery of millimetre-wave excess emission in radio-quiet active galactic nuclei

    NASA Astrophysics Data System (ADS)

    Behar, Ehud; Baldi, Ranieri D.; Laor, Ari; Horesh, Assaf; Stevens, Jamie; Tzioumis, Tasso

    2015-07-01

    The physical origin of radio emission in radio-quiet active galactic nuclei (RQ AGN) remains unclear, whether it is a downscaled version of the relativistic jets typical of radio-loud (RL) AGN, or whether it originates from the accretion disc. The correlation between 5 GHz and X-ray luminosities of RQ AGN, which follows LR = 10-5LX observed also in stellar coronae, suggests an association of both X-ray and radio sources with the accretion disc corona. Observing RQ AGN at higher (mm-wave) frequencies, where synchrotron self-absorption is diminished, and smaller regions can be probed, is key to exploring this association. Eight RQ AGN, selected based on their high X-ray brightness and variability, were observed at 95 GHz with the CARMA (Combined Array for Research in Millimetre-wave Astronomy) and ATCA (the Australia Telescope Compact Array) telescopes. All targets were detected at the 1-10 mJy level. Emission excess at 95 GHz of up to ×7 is found with respect to archival low-frequency steep spectra, suggesting a compact, optically thick core superimposed on the more extended structures that dominate at low frequencies. Though unresolved, the 95 GHz fluxes imply optically thick source sizes of 10-4-10-3 pc, or ˜10-1000 gravitational radii. The present sources lie tightly along an LR (95 GHz) = 10-4LX (2-10 keV) correlation, analogous to that of stellar coronae and RQ AGN at 5 GHz, while RL AGN are shown to have higher LR/LX ratios. The present observations argue that simultaneous mm-wave and X-ray monitoring of RQ AGN features a promising method for understanding accretion disc coronal emission.

  9. A New View at the Galactic Center Region - Methanol Emission in the Sgr A* Environment

    NASA Astrophysics Data System (ADS)

    Stankovic, Marija; Seaquist, E. R.; Leurini, S.; Muehle, S.; Menten, K. M.

    2009-01-01

    Methanol possesses a rich mm spectrum allowing the reliable determination of both density and kinetic temperature from radiative transfer models. It is formed on dust grains, evaporated by UV radiation and shocks, and destroyed by gas phase chemical reactions. As the nearest galactic nuclei that can be observed in great detail, the center of the Milky Way has often been regarded as a template for understanding physical processes governing the extragalactic nuclei in general. It is a dynamic environment where existing energetic processes affect the chemistry on the grain mantles, promoting the formation of complex organic molecules. However, little is known to date about their distribution within the central 30pc. We present the results of our surveys of methanol emission in the central 10'x12'( 20pcx25pc) of our Galaxy, observed at three different frequencies with the JCMT and the IRAM 30-m telescopes. We discuss the morphology of methanol emission and its correlation to other tracers, in particular to those processed on the grain mantles (e.g. NH3, SiO). The possible scenarios that could be accounted for a rather puzzling lack of methanol emission in the inner 5pc are examined. We also present preliminary results of radiative transfer analysis using the LVG code specifically tailored to methanol. Such analysis allows us to measure the distribution of density, kinetic temperature and abundance, and thus to gain insight into the processes which form and destroy gaseous methanol in the Sgr A* region. Furthermore, the understanding of the molecular clouds structure can contribute to the resolution of the longstanding problem of star formation in the central parsec, as recent studies by Wardle & Yusef-Zadeh (2008) and Hobbs & Nayakashin (2008) indicate the importance that giant molecular clouds close to the Sgr A* have in the formation of young stellar population in this region.

  10. CMB multipole measurements in the presence of foregrounds

    NASA Astrophysics Data System (ADS)

    de Oliveira-Costa, Angélica; Tegmark, Max

    2006-07-01

    Most analysis of cosmic microwave background spherical harmonic coefficients aℓm has focused on estimating the power spectrum Cℓ=⟨|aℓm|2⟩ rather than the coefficients themselves. We present a minimum-variance method for measuring aℓm given anisotropic noise, incomplete sky coverage and foreground contamination, and apply it to the Wilkinson Microwave Anisotropy Probe (WMAP) data. Our method is shown to constitute lossless data compression in the sense that the widely used quadratic estimators of the power spectrum Cℓ can be computed directly from our aℓm-estimators. As the Galactic cut is increased, the error bars Δaℓm on low multipoles go from being dominated by foregrounds to being dominated by leakage from other multipoles, with the intervening minimum defining the optimal cut. Applying our method to the WMAP quadrupole and octopole as an illustration, we investigate the robustness of the previously reported “axis of evil” alignment to Galactic cut and foreground contamination.

  11. Modeling Diffuse X-ray Emission around the Galactic Center from Colliding Stellar Winds

    NASA Astrophysics Data System (ADS)

    Post Russell, Christopher Michael; Cuadra, Jorge; Wang, Q. Daniel; Kallman, Timothy R.

    2016-01-01

    The Galactic center is a hotbed of astrophysical phenomena. The ~30 evolved massive stars orbiting the super massive black hole (SMBH) on scales <10" inject a large fraction of the matter that accretes onto the SMBH, and their wind-wind collisions create large swaths of shocked, hot, X-ray emitting material around Sgr A*. The 3Ms Chandra X-ray Visionary Program of the Galactic center provided unprecedented detail of this region by resolving the diffuse thermal emission around the SMBH, and also revealed the presence of SMBH feedback into its immediate surroundings. With the original intent of computing the accretion onto the SMBH, smoothed particle hydrodynamics (SPH) simulations with various feedback prescriptions modeled the 30 Wolf-Rayet (WR) stars orbiting the SMBH over 1100 years while ejecting their stellar winds, thus providing various descriptions of the hot shocked gas around Sgr A*. In this work, we perform 3D X-ray radiative transfer calculations on these hydrodynamic simulations with the goal of reproducing the Chandra observations in the central ±6" around Sgr A*. The model spectral shape from the 2"-5" ring agrees very well with the observations for all feedback models, and the X-ray flux levels of the no or weak feedback models agree with the observation for r<~3". The model flux is too low beyond this radius, while the strong feedback models produce too low a flux throughout the entire simulation region. This is because the strong outflow emanating from the SMBH clears out much of the hot, X-ray emitting gas from its vicinity. These strong feedback simulations are thus excluded from describing Sgr A*. We will conclude by discussing ways to improve the no and weak feedback models, such as by including the O stars and their winds, which should cause the WR-wind X-ray emission to increase as these adiabatic shocks (whose strength is inversely proportional to the distance to the shock) will occur closer to their WR stars.

  12. Planck intermediate results. XIX. An overview of the polarized thermal emission from Galactic dust

    NASA Astrophysics Data System (ADS)

    Planck Collaboration; Ade, P. A. R.; Aghanim, N.; Alina, D.; Alves, M. I. R.; Armitage-Caplan, C.; Arnaud, M.; Arzoumanian, D.; Ashdown, M.; Atrio-Barandela, F.; Aumont, J.; Baccigalupi, C.; Banday, A. J.; Barreiro, R. B.; Battaner, E.; Benabed, K.; Benoit-Lévy, A.; Bernard, J.-P.; Bersanelli, M.; Bielewicz, P.; Bock, J. J.; Bond, J. R.; Borrill, J.; Bouchet, F. R.; Boulanger, F.; Bracco, A.; Burigana, C.; Butler, R. C.; Cardoso, J.-F.; Catalano, A.; Chamballu, A.; Chary, R.-R.; Chiang, H. C.; Christensen, P. R.; Colombi, S.; Colombo, L. P. L.; Combet, C.; Couchot, F.; Coulais, A.; Crill, B. P.; Curto, A.; Cuttaia, F.; Danese, L.; Davies, R. D.; Davis, R. J.; de Bernardis, P.; de Gouveia Dal Pino, E. M.; de Rosa, A.; de Zotti, G.; Delabrouille, J.; Désert, F.-X.; Dickinson, C.; Diego, J. M.; Donzelli, S.; Doré, O.; Douspis, M.; Dunkley, J.; Dupac, X.; Efstathiou, G.; Enßlin, T. A.; Eriksen, H. K.; Falgarone, E.; Ferrière, K.; Finelli, F.; Forni, O.; Frailis, M.; Fraisse, A. A.; Franceschi, E.; Galeotta, S.; Ganga, K.; Ghosh, T.; Giard, M.; Giraud-Héraud, Y.; González-Nuevo, J.; Górski, K. M.; Gregorio, A.; Gruppuso, A.; Guillet, V.; Hansen, F. K.; Harrison, D. L.; Helou, G.; Hernández-Monteagudo, C.; Hildebrandt, S. R.; Hivon, E.; Hobson, M.; Holmes, W. A.; Hornstrup, A.; Huffenberger, K. M.; Jaffe, A. H.; Jaffe, T. R.; Jones, W. C.; Juvela, M.; Keihänen, E.; Keskitalo, R.; Kisner, T. S.; Kneissl, R.; Knoche, J.; Kunz, M.; Kurki-Suonio, H.; Lagache, G.; Lähteenmäki, A.; Lamarre, J.-M.; Lasenby, A.; Lawrence, C. R.; Leahy, J. P.; Leonardi, R.; Levrier, F.; Liguori, M.; Lilje, P. B.; Linden-Vørnle, M.; López-Caniego, M.; Lubin, P. M.; Macías-Pérez, J. F.; Maffei, B.; Magalhães, A. M.; Maino, D.; Mandolesi, N.; Maris, M.; Marshall, D. J.; Martin, P. G.; Martínez-González, E.; Masi, S.; Matarrese, S.; Mazzotta, P.; Melchiorri, A.; Mendes, L.; Mennella, A.; Migliaccio, M.; Miville-Deschênes, M.-A.; Moneti, A.; Montier, L.; Morgante, G.; Mortlock, D.; Munshi, D.; Murphy, J. A.; Naselsky, P.; Nati, F.; Natoli, P.; Netterfield, C. B.; Noviello, F.; Novikov, D.; Novikov, I.; Oxborrow, C. A.; Pagano, L.; Pajot, F.; Paladini, R.; Paoletti, D.; Pasian, F.; Pearson, T. J.; Perdereau, O.; Perotto, L.; Perrotta, F.; Piacentini, F.; Piat, M.; Pietrobon, D.; Plaszczynski, S.; Poidevin, F.; Pointecouteau, E.; Polenta, G.; Popa, L.; Pratt, G. W.; Prunet, S.; Puget, J.-L.; Rachen, J. P.; Reach, W. T.; Rebolo, R.; Reinecke, M.; Remazeilles, M.; Renault, C.; Ricciardi, S.; Riller, T.; Ristorcelli, I.; Rocha, G.; Rosset, C.; Roudier, G.; Rubiño-Martín, J. A.; Rusholme, B.; Sandri, M.; Savini, G.; Scott, D.; Spencer, L. D.; Stolyarov, V.; Stompor, R.; Sudiwala, R.; Sutton, D.; Suur-Uski, A.-S.; Sygnet, J.-F.; Tauber, J. A.; Terenzi, L.; Toffolatti, L.; Tomasi, M.; Tristram, M.; Tucci, M.; Umana, G.; Valenziano, L.; Valiviita, J.; Van Tent, B.; Vielva, P.; Villa, F.; Wade, L. A.; Wandelt, B. D.; Zacchei, A.; Zonca, A.

    2015-04-01

    This paper presents an overview of the polarized sky as seen by Planck HFI at 353 GHz, which is the most sensitive Planck channel for dust polarization. We construct and analyse maps of dust polarization fraction and polarization angle at 1° resolution, taking into account noise bias and possible systematic effects. The sensitivity of the Planck HFI polarization measurements allows for the first time a mapping of Galactic dust polarized emission on large scales, including low column density regions. We find that the maximum observed dust polarization fraction is high (pmax = 19.8%), in particular in some regions of moderate hydrogen column density (NH < 2 × 1021 cm-2). The polarization fraction displays a large scatter at NH below a few 1021 cm-2. There is a general decrease in the dust polarization fraction with increasing column density above NH ≃ 1 × 1021 cm-2 and in particular a sharp drop above NH ≃ 1.5 × 1022 cm-2. We characterize the spatial structure of the polarization angle using the angle dispersion function. We find that the polarization angle is ordered over extended areas of several square degrees, separated by filamentary structures of high angle dispersion function. These appear as interfaces where the sky projection of the magnetic field changes abruptly without variations in the column density. The polarization fraction is found to be anti-correlated with the dispersion of polarization angles. These results suggest that, at the resolution of 1°, depolarization is due mainly to fluctuations in the magnetic field orientation along the line of sight, rather than to the loss of grain alignment in shielded regions. We also compare the polarization of thermal dust emission with that of synchrotron measured with Planck, low-frequency radio data, and Faraday rotation measurements toward extragalactic sources. These components bear resemblance along the Galactic plane and in some regions such as the Fan and North Polar Spur regions. The poor match

  13. Scale heights and equivalent widths of the iron K-shell lines in the Galactic diffuse X-ray emission

    NASA Astrophysics Data System (ADS)

    Yamauchi, Shigeo; Nobukawa, Kumiko K.; Nobukawa, Masayoshi; Uchiyama, Hideki; Koyama, Katsuji

    2016-06-01

    This paper reports the analysis of the X-ray spectra of the Galactic diffuse X-ray emission (GDXE) in the Suzaku archive. The fluxes of the Fe I Kα (6.4 keV), Fe XXV Heα (6.7 keV), and Fe XXVI Lyα (6.97 keV) lines are separately determined. From the latitude distributions, we confirm that the GDXE is decomposed into the Galactic center (GCXE), the Galactic bulge (GBXE) and the Galactic ridge (GRXE) X-ray emissions. The scale heights (SHs) of the Fe XXV Heα line of the GCXE, GBXE, and GRXE are determined to be ˜40, ˜310, and ˜140 pc, while those of the Fe I Kα line are ˜30, ˜160, and ˜70 pc, respectively. The mean equivalent widths (EWs) of the sum of the Fe XXV Heα and Fe XXVI Lyα lines are ˜750 eV, ˜600 eV, and ˜550 eV, while those of the Fe I Kα line are ˜150 eV, ˜60 eV, and ˜100 eV for the GCXE, GBXE, and GRXE, respectively. The origin of the GBXE, GRXE, and GCXE is separately discussed based on the new results of the SHs and EWs, in comparison with those of the cataclysmic variables, active binaries and coronal active stars.

  14. Scale heights and equivalent widths of the iron K-shell lines in the Galactic diffuse X-ray emission

    NASA Astrophysics Data System (ADS)

    Yamauchi, Shigeo; Nobukawa, Kumiko K.; Nobukawa, Masayoshi; Uchiyama, Hideki; Koyama, Katsuji

    2016-08-01

    This paper reports the analysis of the X-ray spectra of the Galactic diffuse X-ray emission (GDXE) in the Suzaku archive. The fluxes of the Fe I Kα (6.4 keV), Fe XXV Heα (6.7 keV), and Fe XXVI Lyα (6.97 keV) lines are separately determined. From the latitude distributions, we confirm that the GDXE is decomposed into the Galactic center (GCXE), the Galactic bulge (GBXE) and the Galactic ridge (GRXE) X-ray emissions. The scale heights (SHs) of the Fe XXV Heα line of the GCXE, GBXE, and GRXE are determined to be ˜40, ˜310, and ˜140 pc, while those of the Fe I Kα line are ˜30, ˜160, and ˜70 pc, respectively. The mean equivalent widths (EWs) of the sum of the Fe XXV Heα and Fe XXVI Lyα lines are ˜750 eV, ˜600 eV, and ˜550 eV, while those of the Fe I Kα line are ˜150 eV, ˜60 eV, and ˜100 eV for the GCXE, GBXE, and GRXE, respectively. The origin of the GBXE, GRXE, and GCXE is separately discussed based on the new results of the SHs and EWs, in comparison with those of the cataclysmic variables, active binaries and coronal active stars.

  15. Intrinsic disc emission and the soft X-ray excess in active galactic nuclei

    NASA Astrophysics Data System (ADS)

    Done, Chris; Davis, S. W.; Jin, C.; Blaes, O.; Ward, M.

    2012-03-01

    Narrow-line Seyfert 1 (NLS1) galaxies have low-mass black holes and mass accretion rates close to (or exceeding) Eddington, so a standard blackbody accretion disc should peak in the extreme ultraviolet. However, the lack of true absorption opacity in the disc means that the emission is better approximated by a colour temperature corrected blackbody, and this colour temperature correction is large enough (˜2.4) that the bare disc emission from a zero spin black hole can extend into the soft X-ray bandpass. Part of the soft X-ray excess seen in these objects must be intrinsic emission from the disc unless the vertical structure is very different to that predicted. None the less, this is not the whole story even for the extreme NLS1 as the shape of the soft excess is much broader than predicted by a bare disc spectrum, indicating some Compton upscattering by warm, optically thick material. We associate this with the disc itself, so it must ultimately be powered by mass accretion. We build an energetically self-consistent model assuming that the emission thermalizes to a (colour temperature corrected) blackbody only at large radii. At smaller radii the gravitational energy is split between powering optically thick Comptonized disc emission (forming the soft X-ray excess) and an optically thin corona above the disc (forming the tail to higher energies). We show examples of this model fit to the extreme NLS1 RE J1034+396, and to the much lower Eddington fraction broad-line Seyfert 1 PG 1048+231. We use these to guide our fits and interpretations of three template spectra made from co-adding multiple sources to track out a sequence of active galactic nucleus (AGN) spectra as a function of L/LEdd. Both the individual objects and template spectra show the surprising result that the Compton upscattered soft X-ray excess decreases in importance with increasing L/LEdd. The strongest soft excesses are associated with low mass accretion rate AGN rather than being tied to some

  16. Diffuse gamma-ray emission modeling near the Galactic Center and the 3 GeV excess

    NASA Astrophysics Data System (ADS)

    Albert, Andrea; Fermi-LAT Collaboration

    2016-01-01

    The region near the Galactic Center (GC) is one of the most complex in the gamma-ray sky. Several groups have reported excess emission in gamma rays peaking around 3 GeV relative to expectations from conventional models for the interstellar emission. We study the uncertainty of the excess emission in Pass 8 Fermi-LAT data due to modeling of the various emission components in that direction. In particular, we quantify the uncertainties on the excess by refitting with several GALPROP models of Galactic diffuse emission, an alternative distribution of gas along the line of sight based on starlight extinction data, a model of the Fermi bubbles at low latitudes, and including templates for additional sources of cosmic-ray (CR) electrons near the GC. In all models that we have tested the excess emission remains significant. The most important contributions to the uncertainties are modeling of the Fermi bubbles and including templates for additional sources of CR electrons. We also consider several models for the population and emission of millisecond pulsars (MSPs) in the inner Galaxy. Although the MSP contribution has large uncertainties, MSPs can explain the GC excess under plausible assumptions.

  17. The Fe II Emission in Active Galactic Nuclei: Excitation Mechanisms and Location of the Emitting Region

    NASA Astrophysics Data System (ADS)

    Marinello, M.; Rodríguez-Ardila, A.; Garcia-Rissmann, A.; Sigut, T. A. A.; Pradhan, A. K.

    2016-04-01

    We present a study of Fe ii emission in the near-infrared region (NIR) for 25 active galactic nuclei (AGNs) to obtain information about the excitation mechanisms that power it and the location where it is formed. We employ an NIR Fe ii template derived in the literature and find that it successfully reproduces the observed Fe ii spectrum. The Fe ii bump at 9200 Å detected in all objects studied confirms that Lyα fluorescence is always present in AGNs. The correlation found between the flux of the 9200 Å bump, the 1 μm lines, and the optical Fe ii implies that Lyα fluorescence plays an important role in Fe ii production. We determined that at least 18% of the optical Fe ii is due to this process, while collisional excitation dominates the production of the observed Fe ii. The line profiles of Fe ii λ10502, O i λ11287, Ca ii λ8664, and Paβ were compared to gather information about the most likely location where they are emitted. We found that Fe ii, O i and Ca ii have similar widths and are, on average, 30% narrower than Paβ. Assuming that the clouds emitting the lines are virialized, we show that the Fe ii is emitted in a region twice as far from the central source than Paβ. The distance, though, strongly varies: from 8.5 light-days for NGC 4051 to 198.2 light-days for Mrk 509. Our results reinforce the importance of the Fe ii in the NIR to constrain critical parameters that drive its physics and the underlying AGN kinematics, as well as more accurate models aimed at reproducing this complex emission.

  18. Effects of Shocks on Emission from Central Engines of Active Galactic Nuclei. I

    NASA Technical Reports Server (NTRS)

    Sivron, R.; Caditz, D.; Tsuruta, S.

    1996-01-01

    In this paper we show that perturbations of the accretion flow within the central engines of some active galactic nuclei (AGNS) are likely to form shock waves in the accreting plasma. Such shocks, which may be either collisional or collisionless, can contribute to the observed high-energy temporal and spectral variability. Our rationale is the following: Observations show that the continuum emission probably originates in an optically thin, hot plasma in the AGN central engine. The flux and spectrum from this hot plasma varies significantly over light crossing timescales. Several authors have suggested that macroscopic perturbations contained within this plasma are the sources of this variability. In order to produce the observed emission the perturbations must be radiatively coupled with the optically thin hot matter and must also move with high velocities. We suggest that shocks, which can be very effective in randomizing the bulk motion of the perturbations, are responsible for this coupling. Shocks should form in the central engine, because the temperatures and magnetic fields are probably reduced below their virial values by radiative dissipation. Perturbations moving at Keplerian speeds, or strong non-linear excitations, result in supersonic and super-Alfvenic velocities leading to shock waves within the hot plasma. We show that even a perturbation smaller than the emitting region can form a shock that significantly modifies the continuum emission in an AGN, and that the spectral and temporal variability from such a shock generally resembles those of radio-quiet AGNS. As an example, the shock inducing perturbation in our model is a small main-sequence star, the capturing and eventual accretion of which are known to be a plausible process. We argue that shocks in the central engine may also provide a natural triggering mechanism for the "cold" component of Guilbert & Rees two-phase medium and an efficient mecha- nism for angular momentum transfer. Current and

  19. Dynamics and X-ray emission of a galactic superwind interacting with disk and halo gas

    NASA Astrophysics Data System (ADS)

    Suchkov, Anatoly A.; Balsara, Dinshaw S.; Heckman, Timothy M.; Leitherer, Claus

    1994-08-01

    There is a general agreement that the conspicuous extranuclear X-ray, optical-line, and radio-contiuum emission of starbursts is associated with powerful galactic superwinds blowing from their centers. However, despite the significant advances in observational studies of superwinds, there is no consensus on the nature of the emitting material and even on the emission mechanisms themselves. This is to a great extent a consequence of a poor understanding of dynamical processes in the starburst superwind regions. To address this issue, we have conducted two-dimensional hydrodynamical simulations of galactic superwinds. While previous similar studies have used a single (disk) component to represent the ISM of the starburst galaxy, we analyze the interaction of the wind with a two-component disk-halo ambient interstellar medium and argue that this two-component representation is crucial for adequate modeling of starbursts. The emphasis of this study is on the geometry and structure of the wind region and the X-ray emission arising in the wind material and the shocked gas in the disk and the halo of the galaxy. The simulation results have shown that a clear-cut bipolar wind can easily develop under a range of very different conditions. On the other hand, a complex 'filamentary' structure associated with the entrained dense disk material is found to arise within the hot bubble blown out by the wind. The flow pattern within the bubble is dominated equally by the central biconic outflow and a system of whirling motions r elated to the origin and development of the 'filaments'. The filament parameters make them a good candidate for optical-emission-line filamentary gas observed in starburst halos. We find that the history of mass and energy deposition in the starburst region of the galaxy is crucial for wind dynamics. A 'mild' early wind, which arises as a result of the cumulative effect of stellar winds from massive stars, produces a bipolar vertical cavity in the disk and

  20. Dynamics and X-ray emission of a galactic superwind interacting with disk and halo gas

    NASA Technical Reports Server (NTRS)

    Suchkov, Anatoly A.; Balsara, Dinshaw S.; Heckman, Timothy M.; Leitherner, Claus

    1994-01-01

    There is a general agreement that the conspicuous extranuclear X-ray, optical-line, and radio-contiuum emission of starbursts is associated with powerful galactic superwinds blowing from their centers. However, despite the significant advances in observational studies of superwinds, there is no consensus on the nature of the emitting material and even on the emission mechanisms themselves. This is to a great extent a consequence of a poor understanding of dynamical processes in the starburst superwind regions. To address this issue, we have conducted two-dimensional hydrodynamical simulations of galactic superwinds. While previous similar studies have used a single (disk) component to represent the ISM of the starburst galaxy, we analyze the interaction of the wind with a two-component disk-halo ambient interstellar medium and argue that this two-component representation is crucial for adequate modeling of starbursts. The emphasis of this study is on the geometry and structure of the wind region and the X-ray emission arising in the wind material and the shocked gas in the disk and the halo of the galaxy. The simulation results have shown that a clear-cut bipolar wind can easily develop under a range of very different conditions. On the other hand, a complex 'filamentary' structure associated with the entrained dense disk material is found to arise within the hot bubble blown out by the wind. The flow pattern within the bubble is dominated equally by the central biconic outflow and a system of whirling motions r elated to the origin and development of the 'filaments'. The filament parameters make them a good candidate for optical-emission-line filamentary gas observed in starburst halos. We find that the history of mass and energy deposition in the starburst region of the galaxy is crucial for wind dynamics. A 'mild' early wind, which arises as a result of the cumulative effect of stellar winds from massive stars, produces a bipolar vertical cavity in the disk and

  1. Neutron star population in the Galactic center region as a potential source of polarized X-ray emission

    NASA Astrophysics Data System (ADS)

    Zajacek, Michal; Karas, Vladimir; Eckart, Andreas

    2016-06-01

    We analyse the emission properties of neutron stars that are predicted to exist in large numbers of the order of 10000 in the innermost parts of the Galactic center. A part of the population of isolated neutron stars propagates supersonically through denser ionized streams of the Minispiral (Sgr A West), forming bow shocks where particles are accelerated and are expected to produce polarized X-ray synchrotron signal. Another source of the synchrotron emission is an elongated magnetosphere and tail. We investigate whether the polarized X-ray emission from Galactic center neutron stars will be potentially detectable in the framework of future X-ray polarimeters. A special case is a detected young neutron star - magnetar SGRJ1745-2900 - that has undergone a series of outbursts with a peak X-ray luminosity of the order of 10^{35} erg s^{-1} (1-10 keV). Apart from an intrinsic X-ray emission, the X-ray emission from neutron star outbursts may be scattered by molecular clouds in the Central Molecular Zone by Thomson scattering, which is another potential source of polarized X-ray emission.

  2. Measurements of the anisotropy of the cosmic background radiation and diffuse galactic emission at millimeter and submillimeter wavelengths

    NASA Technical Reports Server (NTRS)

    Halpern, Mark; Benford, Richard; Meyer, Stephan; Muehlner, Dirk; Weiss, Rainer

    1988-01-01

    The results of a balloon-borne observing program to measure the large angular scale brightness distribution of the 2.7 K cosmic background radiation (CBR) at millimeter and submillimeter wavelengths are reported. A new determination of the dipole anisotropy of the CBR is found with 3.40 + or - 0.42 mK toward alpha = 12.1 + or - 0.24 hr, delta = - 23 + or - 5 deg in a 1.2 to 8/cm band and 4.7 + or - 1.4 mK toward alpha = 9.9 + 1.7 or - 1.1 hr, delta = - 38 + or - 21 deg between 5 and 18/cm, where the amplitudes are listed as thermodynamic temperatures. New estimates of the absolute temperature in these two bands of 2.86 + or - 0.26 K and 3.01 + or - 0.31 are obtained under the assumption that the CBR has a Planck spectrum. The diffuse Galactic emission is fitted by a secant distribution in Galactic latitude, and the resulting Galactic pole antenna temperatures are given. Maps of sky brightness, measurements of zodiacal emission, and measurements of fluctuations of the atmospheric emission which dominates the noise budget are also presented.

  3. A hadronic-leptonic model for the Fermi bubbles: Cosmic-rays in the galactic halo and radio emission

    SciTech Connect

    Fujita, Yutaka; Ohira, Yutaka; Yamazaki, Ryo

    2014-07-01

    We investigate non-thermal emission from the Fermi bubbles in a hadronic model. Cosmic-ray (CR) protons are accelerated at the forward shock of the bubbles. They interact with the background gas in the Galactic halo and create π{sup 0}-decay gamma-rays and secondary electrons through proton-proton interaction. We follow the evolution of the CR protons and electrons by calculating their distribution functions. We find that the spectrum and the intensity profiles of π{sup 0}-decay gamma-rays are consistent with observations. We predict that the shock front is located far ahead of the gamma-ray boundary of the Fermi bubbles. This naturally explains the fact that a clear temperature jump of thermal gas was not discovered at the gamma-ray boundary in recent Suzaku observations. We also consider re-acceleration of the background CRs in the Galactic halo at the shock front. We find that it can significantly affect the gamma-rays from the Fermi bubbles, unless the density of the background CRs is ≲ 10% of that in the Galactic disk. We indicate that secondary electrons alone cannot produce the observed radio emission from the Fermi bubbles. However, the radio emission from the outermost region of the bubbles can be explained if electrons are directly accelerated at the shock front with an efficiency of ∼0.1% of that of protons.

  4. AN XMM-NEWTON SURVEY OF THE SOFT X-RAY BACKGROUND. III. THE GALACTIC HALO X-RAY EMISSION

    SciTech Connect

    Henley, David B.; Shelton, Robin L.

    2013-08-20

    We present measurements of the Galactic halo's X-ray emission for 110 XMM-Newton sight lines selected to minimize contamination from solar wind charge exchange emission. We detect emission from few million degree gas on {approx}4/5 of our sight lines. The temperature is fairly uniform (median = 2.22 Multiplication-Sign 10{sup 6} K, interquartile range = 0.63 Multiplication-Sign 10{sup 6} K), while the emission measure and intrinsic 0.5-2.0 keV surface brightness vary by over an order of magnitude ({approx}(0.4-7) Multiplication-Sign 10{sup -3} cm{sup -6} pc and {approx}(0.5-7) Multiplication-Sign 10{sup -12} erg cm{sup -2} s{sup -1} deg{sup -2}, respectively, with median detections of 1.9 Multiplication-Sign 10{sup -3} cm{sup -6} pc and 1.5 Multiplication-Sign 10{sup -12} erg cm{sup -2} s{sup -1} deg{sup -2}, respectively). The high-latitude sky contains a patchy distribution of few million degree gas. This gas exhibits a general increase in emission measure toward the inner Galaxy in the southern Galactic hemisphere. However, there is no tendency for our observed emission measures to decrease with increasing Galactic latitude, contrary to what is expected for a disk-like halo morphology. The measured temperatures, brightnesses, and spatial distributions of the gas can be used to place constraints on models for the dominant heating sources of the halo. We provide some discussion of such heating sources, but defer comparisons between the observations and detailed models to a later paper.

  5. POLYCYCLIC AROMATIC HYDROCARBON AND EMISSION LINE RATIOS IN ACTIVE GALACTIC NUCLEI AND STARBURST GALAXIES

    SciTech Connect

    Sales, Dinalva A.; Pastoriza, M. G.; Riffel, R. E-mail: pastoriza@ufrgs.b

    2010-12-10

    We study the polycyclic aromatic hydrocarbon (PAH) bands, ionic emission lines, and mid-infrared continuum properties in a sample of 171 emission line galaxies taken from the literature plus 15 new active galactic nucleus (AGN) Spitzer spectra. We normalize the spectra at {lambda} = 23 {mu}m and grouped them according to the type of nuclear activity. The continuum shape steeply rises for longer wavelengths and can be fitted with a warm blackbody distribution of T {approx} 150-300 K. The brightest PAH spectral bands (6.2, 7.7, 8.6, 11.3, and 12.7 {mu}m) and the forbidden emission lines of [Si II] 34.8 {mu}m, [Ar II] 6.9 {mu}m, [S III] 18.7 and 33.4 {mu}m were detected in all the starbursts and in {approx}80% of the Seyfert 2. Taking under consideration only the PAH bands at 7.7 {mu}m, 11.3 {mu}m, and 12.7 {mu}m, we find that they are present in {approx}80% of the Seyfert 1, while only half of this type of activity show the 6.2 {mu}m and 8.6 {mu}m PAH bands. The observed intensity ratios for neutral and ionized PAHs (6.2 {mu}m/7.7 {mu}m x 11.3 {mu}m/7.7 {mu}m) were compared to theoretical intensity ratios, showing that AGNs have higher ionization fraction and larger PAH molecules ({>=}180 carbon atoms) than SB galaxies. The ratio between the ionized (7.7 {mu}m) and the neutral PAH bands (8.6 {mu}m and 11.3 {mu}m) are distributed over different ranges for AGNs and SB galaxies, suggesting that these ratios could depend on the ionization fraction, as well as on the hardness of the radiation field. The ratio between the 7.7 {mu}m and 11.3 {mu}m bands is nearly constant with the increase of [Ne III]15.5 {mu}m/[Ne II] 12.8 {mu}m, indicating that the fraction of ionized to neutral PAH bands does not depend on the hardness of the radiation field. The equivalent width of both PAH features show the same dependence (strongly decreasing) with [Ne III]/[Ne II], suggesting that the PAH molecules, emitting either ionized (7.7 {mu}m) or neutral (11.3 {mu}m) bands, may be destroyed

  6. The Discovery of X-ray Emission from Active Galactic Nuclei

    NASA Astrophysics Data System (ADS)

    Elvis, Martin

    2013-01-01

    Back in 1974 the UHURU catalog (3U) had been published with many UHGLS - unidentified high galactic latitude sources. Identifications were hampered by the square degree sized error boxes (positional uncertainties). Could these explain the cosmic X-ray background? Could UHGLS be "X-ray galaxies"? Only three active galaxies (AGNs) had been found as X-ray sources: 3C273, Cen A and NGC 4151, while others had upper limits. What was the difference between X-ray and non-X-ray AGNs? It turned out that the slightly better positioning capability and slightly deeper sensitivity of the Ariel V Sky Survey Instrument (SSI), launched in October 1974, were just enough to show that the UHGLS were Seyfert galaxies. And I was lucky enough that I'd joined the Leicester X-ray group and had taken on the UHGLS for my PhD thesis, with Ken Pounds as my supervisor. With the SSI we made a catalog of high latitude sources, the "2A" catalog, including about a dozen known Seyfert galaxies (lowish luminosity nearby AGNs) and, with Mike Penston and Martin Ward, we went on to identify many of them with both newly discovered normal broad emission line AGNs and a few new "narrow emission line galaxies", or NELGs, as we called them. We are now convinced that it is summation of many obscured NELGs that produce the flat spectrum of the X-ray background, and we are still searching for them in Chandra deep surveys and at higher energies with NuSTAR. There was an obvious connection between the X-ray obscuration and the optical reddening, which must lie outside the region emitting the broad optical spectral lines. Andy Lawrence and I, following a clue from Bill Keel, put this together into what we now call the Unified Scheme for AGN structure. This idea of a flattened torus obscuring the inner regions of the AGN was so dramatically confirmed a few years later -- by Ski Antonucci and Joe Miller's discovery of polarized broad emission lines in NGC1068 -- that the precursor papers became irrelevant. But Ariel

  7. THE NUCLEAR INFRARED EMISSION OF LOW-LUMINOSITY ACTIVE GALACTIC NUCLEI

    SciTech Connect

    Mason, R. E.; Lopez-Rodriguez, E.; Packham, C.; Alonso-Herrero, A.; Elitzur, M.; Aretxaga, I.; Roche, P. F.; Oi, N.

    2012-07-15

    We present high-resolution mid-infrared (MIR) imaging, nuclear spectral energy distributions (SEDs), and archival Spitzer spectra for 22 low-luminosity active galactic nuclei (LLAGNs; L{sub bol} {approx}< 10{sup 42} erg s{sup -1}). Infrared (IR) observations may advance our understanding of the accretion flows in LLAGNs, the fate of the obscuring torus at low accretion rates, and, perhaps, the star formation histories of these objects. However, while comprehensively studied in higher-luminosity Seyferts and quasars, the nuclear IR properties of LLAGNs have not yet been well determined. We separate the present LLAGN sample into three categories depending on their Eddington ratio and radio emission, finding different IR characteristics for each class. (1) At the low-luminosity, low-Eddington-ratio (log L{sub bol}/L{sub Edd} < -4.6) end of the sample, we identify 'host-dominated' galaxies with strong polycyclic aromatic hydrocarbon bands that may indicate active (circum-)nuclear star formation. (2) Some very radio-loud objects are also present at these low Eddington ratios. The IR emission in these nuclei is dominated by synchrotron radiation, and some are likely to be unobscured type 2 AGNs that genuinely lack a broad-line region. (3) At higher Eddington ratios, strong, compact nuclear sources are visible in the MIR images. The nuclear SEDs of these galaxies are diverse; some resemble typical Seyfert nuclei, while others lack a well-defined MIR 'dust bump'. Strong silicate emission is present in many of these objects. We speculate that this, together with high ratios of silicate strength to hydrogen column density, could suggest optically thin dust and low dust-to-gas ratios, in accordance with model predictions that LLAGNs do not host a Seyfert-like obscuring torus. We anticipate that detailed modeling of the new data and SEDs in terms of accretion disk, jet, radiatively inefficient accretion flow, and torus components will provide further insights into the nuclear

  8. Optical versus infrared studies of dusty galaxies and active galactic nuclei - I. Nebular emission lines

    NASA Astrophysics Data System (ADS)

    Wild, Vivienne; Groves, Brent; Heckman, Timothy; Sonnentrucker, Paule; Armus, Lee; Schiminovich, David; Johnson, Benjamin; Martins, Lucimara; Lamassa, Stephanie

    2011-01-01

    Optical nebular emission lines are commonly used to estimate the star formation rate of galaxies and the black hole accretion rate of their central active nuclei. The accuracy of the conversion from line strengths to physical properties depends upon the accuracy to which the lines can be corrected for dust attenuation. For studies of single galaxies with normal amounts of dust, most dust corrections result in the same derived properties within the errors. However, for statistical studies of populations of galaxies, or for studies of galaxies with higher dust contents, such as might be found in some classes of ‘transition’ galaxies, significant uncertainty arises from the dust attenuation correction. In this paper, we compare the strength of the predominantly unobscured mid-infrared [Ne II] λ15.5 μ m+[Ne III] λ12.8 μ m emission lines to the optical Hα emission lines in four samples of galaxies: (i) ordinary star-forming galaxies (80 galaxies); (ii) optically selected dusty galaxies (11); (iii) ultraluminous infrared galaxies (6); and (iv) Seyfert 2 galaxies (20). We show that a single dust attenuation curve applied to all samples can correct the Hα luminosity for dust attenuation to a factor better than 2. Similarly, we compare [O IV] and [O III] luminosities to find that [O III] can be corrected to a factor better than 3. This shows that the total dust attenuation suffered by the active galactic nucleus narrow-line region is not significantly different from that suffered by the star-forming H II regions in the galaxy. We provide explicit dust attenuation corrections, together with errors, for [O II], [O III] and Hα. The best-fitting average attenuation curve is slightly greyer than the Milky Way extinction law, indicating either that external galaxies have slightly different typical dust properties from those of the Milky Way or that there is a significant contribution from scattering. Finally, we uncover an intriguing correlation between silicate

  9. Fe Line Diagnostics of Cataclysmic Variables and Galactic Ridge X-Ray Emission

    NASA Astrophysics Data System (ADS)

    Xu, Xiao-jie; Wang, Q. Daniel; Li, Xiang-Dong

    2016-02-01

    The properties of the Galactic Ridge X-ray Emission (GRXE) observed in the 2-10 keV band place fundamental constraints on various types of X-ray sources in the Milky Way. Although the primarily discrete origin of the emission is now well established, the responsible populations of these sources remain uncertain, especially at relatively low fluxes. To provide insights into this issue, we systematically characterize the Fe emission line properties of the candidate types of the sources in the solar neighborhood and compare them with those measured for the GRXE. Our source sample includes 6 symbiotic stars, 16 intermediate polars (IPs), 3 polars, 16 quiescent dwarf novae, and 4 active binaries (ABs); they are all observed with the Suzaku X-ray Observatory. The data of about one-fourth of these sources are analyzed for the first time. We find that the mean equivalent width (EW6.7) of the 6.7 keV line and the mean 7.0/6.7 keV line ratio are 107 ± 16.0 eV and 0.71 ± 0.04 for IPs and 221 ± 135 eV and 0.44 ± 0.14 for polars, respectively, which are all substantially different from those (490 ± 15 eV and 0.2 ± 0.08) for the GRXE. Instead, the GRXE values are better agreed by the EW6.7 (438 ± 84.6 eV) and the ratio (0.27 ± 0.06) observed for the DNe. We further find that the EW6.7 is strongly correlated with the 2-10 keV luminosity of the DNe, which can be characterized by the relation {{EW}}6.7={(438+/- 95{{eV}})(L/{10}31{erg}{{{s}}}-1)}(-0.31+/- 0.15). Accounting for this correlation, the agreement can be improved further, especially when the contributions from other class sources to the GRXE are considered, which all have low EW6.7 values. We conclude that the GRXE mostly consists of typically faint but numerous DNe, plus ABs, while magnetic cataclysmic variables are probably mainly the high-flux representatives of the responsible populations and dominate the GRXE only in harder energy bands.

  10. Morphology of the Galactic dark matter synchrotron emission with self-consistent cosmic-ray diffusion models

    SciTech Connect

    Linden, Tim; Anderson, Brandon; Profumo, Stefano

    2010-09-15

    A generic prediction in the paradigm of weakly interacting dark matter is the production of relativistic particles from dark matter pair annihilation in regions of high dark matter density. Ultrarelativistic electrons and positrons produced in the center of the Galaxy by dark matter annihilation should produce a diffuse synchrotron emission. While the spectral shape of the synchrotron dark matter haze depends on the particle model (and secondarily on the Galactic magnetic fields), the morphology of the haze depends primarily on (1) the dark matter density distribution, (2) the Galactic magnetic field morphology, and (3) the diffusion model for high-energy cosmic-ray leptons. Interestingly, an unidentified excess of microwave radiation with characteristics similar to those predicted by dark matter models has been claimed to exist near the Galactic center region in the data reported by the Wilkinson Microwave Anisotropy Probe (WMAP) satellite, and is dubbed the 'WMAP haze'. In this study, we carry out a self-consistent treatment of the variables enumerated above, enforcing constraints from the available data on cosmic rays, radio surveys, and diffuse gamma rays. We outline and make predictions for the general morphology and spectral features of a 'dark matter haze' and we compare them to the WMAP haze data. We also characterize and study the spectrum and spatial distribution of the inverse-Compton emission resulting from the same population of energetic electrons and positrons. We point out that the spectrum and morphology of the radio emission at different frequencies are powerful diagnostics to test whether a Galactic synchrotron haze indeed originates from dark matter annihilation.

  11. GeV excess in the Milky Way: The role of diffuse galactic gamma-ray emission templates

    NASA Astrophysics Data System (ADS)

    Zhou, Bei; Liang, Yun-Feng; Huang, Xiaoyuan; Li, Xiang; Fan, Yi-Zhong; Feng, Lei; Chang, Jin

    2015-06-01

    Several groups have analyzed the publicly available Fermi-LAT data and have reported a spatially extended γ ray excess of around 1-3 GeV from the region surrounding the Galactic center that might originate from annihilation of dark-matter particles with a rest mass mχ˜30 -40 GeV . In this work we examine the role of the diffuse galactic gamma-ray emission templates played in suppressing the GeV excess. For such a purpose, we adopt in total 128 background templates that were generated by Ackermann et al. [Astrophys. J. 750, 3 (2012)] in the study of the Fermi-LAT observations of the diffuse gamma-ray emission considering the effects of cosmic rays and the interstellar medium. The possible GeV excess, assumed to follow the spatial distribution of the prompt gamma rays produced in the annihilation of dark-matter particles taking a generalized Navarro-Frenk-White profile with an inner slope α =1.2 , has been analyzed in some regions of interest. The introduction of such an additional component centered at the Galactic center is found to have improved the goodness of fit to the data significantly in all background template models regardless of whether the excess spectrum is fixed or not. Our results thus suggest that the presence of a statistically significant GeV excess in the inner Galaxy is robust, though its spectrum depends on the diffuse galactic gamma-ray emission model adopted in the analysis. The possible physical origin of the GeV excess component is discussed and, in the dark-matter model, the annihilation cross section of such particles is evaluated.

  12. High Galactic latitude polarized emission at 1.4 GHz and implications for cosmic microwave background observations

    NASA Astrophysics Data System (ADS)

    Carretti, E.; Bernardi, G.; Sault, R. J.; Cortiglioni, S.; Poppi, S.

    2005-03-01

    We analyse the polarized emission at 1.4 GHz in a 3°× 3° area at high Galactic latitude (b~-40°). The region, centred in (α= 5h, δ=-49°), was observed with the Australia Telescope Compact Array (ATCA) radio-interferometer, whose 3-30 arcmin angular sensitivity range allows the study of scales appropriate for cosmic microwave background polarization (CMBP) investigations. The angular behaviour of the diffuse emission is analysed through the E- and B-mode angular power spectra. These follow a power law CXl~lβX with slopes βE=-1.97 +/- 0.08 and βB=-1.98 +/- 0.07. The emission is found to be approximately a factor 25 fainter than in Galactic plane regions. The comparison of the power spectra with other surveys indicates that this area is intermediate between strong and negligible Faraday rotation effects. A similar conclusion can be reached by analysing both the frequency and Galactic latitude behaviours of the diffuse Galactic emission of the 408-1411 MHz Leiden survey data. We present an analysis of the Faraday rotation effects on the polarized power spectra and find that the observed power spectra can be enhanced by a transfer of power from large to small angular scales. The extrapolation of the spectra to 32 and 90 GHz of the cosmic microwave background (CMB) window suggests that Galactic synchrotron emission leaves the CMBP E-mode uncontaminated at 32 GHz. The level of the contamination at 90 GHz is expected to be more than 4 orders of magnitude below the CMBP spectrum. Extrapolating to the relevant angular scales, this region also appears adequate for investigation of the CMBP B-modes for models with tensor-to-scalar fluctuation power ratio T/S > 0.01. We also identify polarized point sources in the field, providing a nine object list, which is complete down to the polarized flux limit of Splim= 2 mJy.

  13. Observation of forbidden C II 158 micron emission from the diffuse interstellar medium at high Galactic latitude

    NASA Technical Reports Server (NTRS)

    Bock, J. J.; Hristov, V. V.; Kawada, M.; Matsuhara, H.; Matsumoto, T.; Matsuura, S.; Mauskopf, P. D.; Richards, P. L.; Tanaka, M.; Lange, A. E.

    1993-01-01

    We report the first detection of forbidden C II 158 micron line emission from the diffuse interstellar medium at high Galactic latitude. We have measured the integrated line intensity in a 36 arcmin field of view along a triangular scan path in a 5 x 20 deg region in Ursa Major using a rocket-borne, liquid-helium-cooled spectrophotometer. The scan included high-latitude infrared cirrus, molecular clouds, a bright external galaxy, M82, and the H I Hole, which is a region of uniquely low neutral hydrogen column density. Emission from forbidden C II is observed in all regions, and, in the absence of appreciable CO emission, it is well correlated with neutral hydrogen column density. We observe a forbidden C II gas cooling rate which varies from (1.18 +/- 0.4 to 3.25 +/- 0.8) x 10 exp -26 ergs/s/H atom. Regions with CO emission have enhanced forbidden C II line emission over that expected from the correlation with neutral hydrogen column density. We measure a line-to-continuum ratio which varies from 0.002 to 0.008 in comparison with the all-sky average of 0.0082 reported by FIRAS, which is heavily weighted toward the Galactic plane.

  14. Galactic Synchrotron Emission and the Far-infrared–Radio Correlation at High Redshift

    NASA Astrophysics Data System (ADS)

    Schober, J.; Schleicher, D. R. G.; Klessen, R. S.

    2016-08-01

    Theoretical scenarios, including the turbulent small-scale dynamo, predict that strong magnetic fields already exist in young galaxies. Based on the assumption of energy equipartition between magnetic fields and turbulence, we determine the galactic synchrotron flux as a function of redshift z. Galaxies in the early universe are different from local galaxies, in particular, the former have more intense star formation. To cover a large range of conditions, we consider two different systems: one model galaxy comparable to the Milky Way and one typical high-z starburst galaxy. We include a model of the steady-state cosmic ray spectrum and find that synchrotron emission can be detected up to cosmological redshifts with current and future radio telescopes. The turbulent dynamo theory is in agreement with the origin of the observed correlation between the far-infrared (FIR) luminosity L FIR and the radio luminosity L radio. Our model reproduces this correlation well at z = 0. We extrapolate the FIR–radio correlation to higher redshifts and predict a time evolution with a significant deviation from its present-day appearance already at z≈ 2 for a gas density that increases strongly with z. In particular, we predict a decrease of the radio luminosity with redshift which is caused by the increase of cosmic ray energy losses at high z. The result is an increase of the ratio between L FIR and L radio. Simultaneously, we predict that the slope of the FIR–radio correlation becomes shallower with redshift. This behavior of the correlation could be observed in the near future with ultra-deep radio surveys.

  15. Nuclear γ-ray line emission induced by energetic ions in solar flares and by galactic cosmic rays

    NASA Astrophysics Data System (ADS)

    Kiener, J.; Tatischeff, V.; Benhabiles-Mezhoud, H.; de Séréville, N.; Belhout, A.

    2012-05-01

    The γ-ray spectra ol the strongest solar flares often show a broad and complex structure in the 0.1-10 MeV region sitting on a bremsstrahlung continuum. This structure is composed of several outstanding narrow lines and of thousands of unresolved narrow and broad lines forming a quasi-continuum. The major part of this emission is due to prompt deexcitation lines following nuclear interactions of accelerated light and heavy ions with the atomic nuclei composing the solar atmosphere. A similar emission is expected from interactions of galactic cosmic rays with the interstellar gas and dust. Experimental nuclear reaction studies coupled with extensive calculations have been done in the last one and a half decade at Orsay for the modelisation of this γ-ray emission. After a description of the nuclear reaction studies the analysis of one solar flare spectrum and predictions for the emission from the inner Galaxy will be presented.

  16. Measurements of galactic plane gamma ray emission in the energy range from 10 - 80 MeV

    NASA Technical Reports Server (NTRS)

    Bertsch, D. L.; Kniffen, D. A.

    1982-01-01

    A spark chamber gamma ray telescope was developed and flown to observe diffuse gamma ray emission from the central region of the galaxy. The extension of observations down to 10 MeV provides important new data indicating that the galactic diffuse gamma ray spectrum continues as a power law down to about 10 MeV, an observation in good agreement with recent theoretical predictions. Data from other experiments in the range from 100 keV to 10 MeV show a significant departure from the extension of the power-law fit to the medium energy observations reported here, possibly indicating that a different mechanism may be responsible for the emissions below and above a few MeV. The intensity of the spectrum above 10 MeV implies a galactic electron spectrum which is also very intense down to about 10 MeV. Electrons in this energy range cannot be observed in the solar cavity because of solar modulation effects. The galactic gamma ray data are compared with recent theoretical predictions.

  17. Near-infrared spectroscopy of faint discrete X-ray point sources constituting the Galactic ridge X-ray emission

    NASA Astrophysics Data System (ADS)

    Morihana, Kumiko; Tsujimoto, Masahiro; Dubath, Pierre; Yoshida, Tessei; Suzuki, Kensuke; Ebisawa, Ken

    2016-05-01

    The Galactic Ridge X-ray Emission (GRXE) is an apparently extended X-ray emission along the Galactic plane. The X-ray spectrum is characterized by a hard continuum with a strong Fe K emission feature in the 6-7 keV band. A substantial fraction (˜80%) of the GRXE in the Fe band was resolved into point sources by deep Chandra imaging observations; thus GRXE is mostly composed of dim Galactic X-ray point sources, at least in this energy band. To investigate the populations of these dim X-ray point sources, we carried out near-infrared (NIR) follow-up spectroscopic observations in two deep Chandra fields located in the Galactic plane at (l, b) = (0.1°, -1.4°) and (28.5°, 0.0°) using NTT/SofI and Subaru/MOIRCS. We obtained well-exposed NIR spectra from 65 objects and found that there are three main classes of Galactic sources based on the X-ray color and NIR spectral features: those having (A) hard X-ray spectra and NIR emission features such as H I (Brγ), He I, and He II (2 objects), (B) soft X-ray spectra and NIR absorption features such as H I, Na I, Ca I, and CO (46 objects), and (C) hard X-ray spectra and NIR absorption features such as H I, Na I, Ca I, and CO (17 objects). From these features, we argue that class A sources are cataclysmic variables (CVs), and class B sources are late-type stars with enhanced coronal activity, which is in agreement with current knowledge. Class C sources possibly belong to a new group of objects, which has been poorly studied so far. We argue that the candidate sources for class C are the binary systems hosting white dwarfs and late-type companions with very low accretion rates. It is likely that this newly recognized class of sources contribute to a non-negligible fraction of the GRXE, especially in the Fe K band.

  18. Near-infrared spectroscopy of faint discrete X-ray point sources constituting the Galactic ridge X-ray emission

    NASA Astrophysics Data System (ADS)

    Morihana, Kumiko; Tsujimoto, Masahiro; Dubath, Pierre; Yoshida, Tessei; Suzuki, Kensuke; Ebisawa, Ken

    2016-08-01

    The Galactic Ridge X-ray Emission (GRXE) is an apparently extended X-ray emission along the Galactic plane. The X-ray spectrum is characterized by a hard continuum with a strong Fe K emission feature in the 6-7 keV band. A substantial fraction (˜80%) of the GRXE in the Fe band was resolved into point sources by deep Chandra imaging observations; thus GRXE is mostly composed of dim Galactic X-ray point sources, at least in this energy band. To investigate the populations of these dim X-ray point sources, we carried out near-infrared (NIR) follow-up spectroscopic observations in two deep Chandra fields located in the Galactic plane at (l, b) = (0.1°, -1.4°) and (28.5°, 0.0°) using NTT/SofI and Subaru/MOIRCS. We obtained well-exposed NIR spectra from 65 objects and found that there are three main classes of Galactic sources based on the X-ray color and NIR spectral features: those having (A) hard X-ray spectra and NIR emission features such as H I (Brγ), He I, and He II (2 objects), (B) soft X-ray spectra and NIR absorption features such as H I, Na I, Ca I, and CO (46 objects), and (C) hard X-ray spectra and NIR absorption features such as H I, Na I, Ca I, and CO (17 objects). From these features, we argue that class A sources are cataclysmic variables (CVs), and class B sources are late-type stars with enhanced coronal activity, which is in agreement with current knowledge. Class C sources possibly belong to a new group of objects, which has been poorly studied so far. We argue that the candidate sources for class C are the binary systems hosting white dwarfs and late-type companions with very low accretion rates. It is likely that this newly recognized class of sources contribute to a non-negligible fraction of the GRXE, especially in the Fe K band.

  19. Spectral and spatial resolution of the 12.8 micron Ne 2 emission from the galactic center. [astronomical spectroscopy/emission spectra, radio sources (astronomy)

    NASA Technical Reports Server (NTRS)

    Wollman, E. R.; Geballe, T. R.; Lacy, J. H.; Townes, C. H.; Rank, D. M.

    1975-01-01

    High-resolution spectra of the Ne II 12.8 micron fine-structure line in emission from the galactic center cloud Sgr A West show a line-center LSR radial velocity of + 75 + or - 20 km/sec. and a velocity dispersion of about 200 km/sec. The line has been observed with spectral resolution as high as 0.10/cm and spatial resolution as high as 8 sec. This appears to provide a direct measurement of conditions in the 45 sec. ionized region at the galactic center. The radial velocity and dispersion are more-or-less independent of position and indicate that events as recent as the last 4 million years have given the ionized gas a systematic motion with respect to the massive stellar component of material at the galactic center. An upper limit for the mass approximately equal to four million times the solar mass was obtained from the velocity distribution, with the mass located within 0.8 parsecs of the galactic center.

  20. X-RAY SEARCHES FOR EMISSION FROM THE WHIM IN THE GALACTIC HALO AND THE INTERGALACTIC MEDIUM

    SciTech Connect

    Bregman, Joel N.; Otte, Birgit; Irwin, Jimmy A.; Putman, Mary E.; Lloyd-Davies, Edward J.; Bruens, Christian E-mail: otteb@umich.edu E-mail: mputman@astro.columbia.edu E-mail: cbruens@astro.uni-bonn.de

    2009-07-10

    At least 50% of the baryons in the local universe are undetected and predicted to be in a hot dilute phase (10{sup 5}-10{sup 7} K) in low and moderate overdensity environments. We searched for the predicted diffuse faint emission through shadowing observations whereby cool foreground gas absorbs more distant diffuse emission. Observations were obtained with Chandra and XMM-Newton. Using the cold gas in two galaxies, NGC 891 and NGC 5907, shadows were not detected and a newer observation of NGC 891 fails to confirm a previously reported X-ray shadow. Our upper limits lie above model predictions. For Local Group studies, we used a cloud in the Magellanic Stream and a compact high-velocity cloud to search for a shadow. Instead of a shadow, the X-ray emission was brighter toward the Magellanic Stream cloud and there is a less significant brightness enhancement toward the other cloud also. The brightness enhancement toward the Magellanic Stream cloud is probably due to an interaction with a hot ambient medium that surrounds the Milky Way. We suggest that this interaction drives a shock into the cloud, heating the gas to X-ray emitting temperatures.

  1. Diffuse X-Ray Emission in a Deep Chandra Image of the Galactic Center

    NASA Astrophysics Data System (ADS)

    Muno, M. P.; Baganoff, F. K.; Bautz, M. W.; Feigelson, E. D.; Garmire, G. P.; Morris, M. R.; Park, S.; Ricker, G. R.; Townsley, L. K.

    2004-09-01

    We examine the spectrum of diffuse emission detected in the 17'×17' field around Sgr A* during 625 ks of Chandra observations. The spectrum exhibits He-like and H-like lines from Si, S, Ar, Ca, and Fe that are consistent with an origin in a two-temperature plasma, as well as a prominent low-ionization Fe Kα line. The cooler, kT~0.8 keV plasma differs in surface brightness across the image in the range (0.2-1.8)×10-13 ergs cm-2 s-1 arcmin-2 (observed, 2-8 keV). This soft plasma is probably heated by supernovae, along with a small contribution from the winds of massive Wolf-Rayet (W-R) and O stars. The radiative cooling rate of the soft plasma within the inner 20 pc of the Galaxy could be balanced by 1% of the kinetic energy of one supernova every 3×105 yr. The hotter, kT~8 keV component is more spatially uniform, with a surface brightness of (1.5-2.6)×10-13 ergs cm-2 s-1 arcmin-2 (observed, 2-8 keV). The intensity of the hard plasma is correlated with that of the soft, but they are probably only indirectly related, because neither supernova remnants nor W-R/O stars are observed to produce thermal plasma hotter than kT~3 keV. Moreover, a kT~8 keV plasma would be too hot to be bound to the Galactic center and therefore would form a slow wind or fountain of plasma. The energy required to sustain such a freely expanding plasma within the inner 20 pc of the Galaxy is ~1040 ergs s-1. This corresponds to the entire kinetic energy of one supernova every 3000 yr, which is unreasonably high. However, alternative explanations for the kT~8 keV diffuse emission are equally unsatisfying. The hard X-rays are unlikely to result from undetected point sources, because no known population of stellar objects is numerous enough to account for the observed surface brightness. Neither is there evidence that nonthermal mechanisms for producing the hard emission are operating, as the expected shifts in the line energies and ratios from their collisional-equilibrium values are not

  2. Cross-Correlation of Tenerife Data with Galactic Templates-Evidence for Spinning Dust?

    PubMed

    de Oliveira-Costa A; Tegmark; Gutiérrez; Jones; Davies; Lasenby; Rebolo; Watson

    1999-12-10

    The recent discovery of dust-correlated diffuse microwave emission has prompted two rival explanations: free-free emission and spinning dust grains. We present new detections of this component at 10 and 15 GHz by the switched-beam Tenerife experiment. The data show a turnover in the spectrum and thereby support the spinning dust hypothesis. We also present a significant detection of synchrotron radiation at 10 GHz, which is useful for normalizing foreground contamination of cosmic microwave background experiments at high galactic latitudes. PMID:10566987

  3. MODELING THE ANOMALY OF SURFACE NUMBER DENSITIES OF GALAXIES ON THE GALACTIC EXTINCTION MAP DUE TO THEIR FIR EMISSION CONTAMINATION

    SciTech Connect

    Kashiwagi, Toshiya; Suto, Yasushi; Taruya, Atsushi; Yahata, Kazuhiro; Kayo, Issha; Nishimichi, Takahiro

    2015-02-01

    The most widely used Galactic extinction map is constructed assuming that the observed far-infrared (FIR) fluxes come entirely from Galactic dust. According to the earlier suggestion by Yahata et al., we consider how FIR emission of galaxies affects the SFD map. We first compute the surface number density of Sloan Digital Sky Survey (SDSS) DR7 galaxies as a function of the r-band extinction, A {sub r,} {sub SFD}. We confirm that the surface densities of those galaxies positively correlate with A {sub r,} {sub SFD} for A {sub r,} {sub SFD} < 0.1, as first discovered by Yahata et al. for SDSS DR4 galaxies. Next we construct an analytical model to compute the surface density of galaxies, taking into account the contamination of their FIR emission. We adopt a log-normal probability distribution for the ratio of 100 μm and r-band luminosities of each galaxy, y ≡ (νL){sub 100} {sub μm}/(νL) {sub r}. Then we search for the mean and rms values of y that fit the observed anomaly, using the analytical model. The required values to reproduce the anomaly are roughly consistent with those measured from the stacking analysis of SDSS galaxies. Due to the limitation of our statistical modeling, we are not yet able to remove the FIR contamination of galaxies from the extinction map. Nevertheless, the agreement with the model prediction suggests that the FIR emission of galaxies is mainly responsible for the observed anomaly. Whereas the corresponding systematic error in the Galactic extinction map is 0.1-1 mmag, it is directly correlated with galaxy clustering and thus needs to be carefully examined in precision cosmology.

  4. Observational studies on the near-infrared unidentified emission bands in galactic H II regions

    SciTech Connect

    Mori, Tamami I.; Onaka, Takashi; Sakon, Itsuki; Ohsawa, Ryou; Bell, Aaron C.; Ishihara, Daisuke; Shimonishi, Takashi

    2014-03-20

    Using a large collection of near-infrared spectra (2.5-5.4 μm) of Galactic H II regions and H II region-like objects, we perform a systematic investigation of astronomical polycyclic aromatic hydrocarbon (PAH) features. Thirty-six objects were observed using the infrared camera on board the AKARI satellite as a part of a director's time program. In addition to the well known 3.3-3.6 μm features, most spectra show a relatively weak emission feature at 5.22 μm with sufficient signal-to-noise ratios, which we identify as the PAH 5.25 μm band (previously reported). By careful analysis, we find good correlations between the 5.25 μm band and both the aromatic hydrocarbon feature at 3.3 μm and the aliphatic hydrocarbon features at around 3.4-3.6 μm. The present results give us convincing evidence that the astronomical 5.25 μm band is associated with C-H vibrations, as suggested by previous studies, and show its potential to probe the PAH size distribution. The analysis also shows that the aliphatic-to-aromatic ratio of I {sub 3.4-3.6} {sub μm}/I {sub 3.3} {sub μm} decreases against the ratio of the 3.7 μm continuum intensity to the 3.3 μm band, I {sub cont,} {sub 3.7} {sub μm}/I {sub 3.3} {sub μm}, which is an indicator of the ionization fraction of PAHs. The midinfrared color of I {sub 9} {sub μm}/I {sub 18} {sub μm} also declines steeply against the ratio of the hydrogen recombination line Brα at 4.05 μm to the 3.3 μm band, I {sub Brα}/I {sub 3.3} {sub μm}. These facts indicate possible dust processing inside or at the boundary of ionized gas.

  5. Observational Studies on the Near-infrared Unidentified Emission Bands in Galactic H II Regions

    NASA Astrophysics Data System (ADS)

    Mori, Tamami I.; Onaka, Takashi; Sakon, Itsuki; Ishihara, Daisuke; Shimonishi, Takashi; Ohsawa, Ryou; Bell, Aaron C.

    2014-03-01

    Using a large collection of near-infrared spectra (2.5-5.4 μm) of Galactic H II regions and H II region-like objects, we perform a systematic investigation of astronomical polycyclic aromatic hydrocarbon (PAH) features. Thirty-six objects were observed using the infrared camera on board the AKARI satellite as a part of a director's time program. In addition to the well known 3.3-3.6 μm features, most spectra show a relatively weak emission feature at 5.22 μm with sufficient signal-to-noise ratios, which we identify as the PAH 5.25 μm band (previously reported). By careful analysis, we find good correlations between the 5.25 μm band and both the aromatic hydrocarbon feature at 3.3 μm and the aliphatic hydrocarbon features at around 3.4-3.6 μm. The present results give us convincing evidence that the astronomical 5.25 μm band is associated with C-H vibrations, as suggested by previous studies, and show its potential to probe the PAH size distribution. The analysis also shows that the aliphatic-to-aromatic ratio of I 3.4-3.6 μm/I 3.3 μm decreases against the ratio of the 3.7 μm continuum intensity to the 3.3 μm band, I cont, 3.7 μm/I 3.3 μm, which is an indicator of the ionization fraction of PAHs. The midinfrared color of I 9 μm/I 18 μm also declines steeply against the ratio of the hydrogen recombination line Brα at 4.05 μm to the 3.3 μm band, I Brα/I 3.3 μm. These facts indicate possible dust processing inside or at the boundary of ionized gas.

  6. Millisecond pulsars and the Galactic Center gamma-ray excess: the importance of luminosity function and secondary emission

    NASA Astrophysics Data System (ADS)

    Petrović, Jovana; Serpico, Pasquale D.; Zaharijas, Gabrijela

    2015-02-01

    Several groups of authors have analyzed Fermi LAT data in a region around the Galactic Center finding an unaccounted gamma-ray excess over diffuse backgrounds in the GeV energy range. It has been argued that it is difficult or even impossible to explain this diffuse emission by the leading astrophysical candidates—millisecond pulsars (MSPs). Here we provide a new estimate of the contribution to the excess by a population of yet unresolved MSP located in the bulge of the Milky Way. We simulate this population with the GALPLOT package by adopting a parametric approach, with the range of free parameters gauged on the MSP characteristics reported by the second pulsar catalogue (2PC). We find that the conclusions strongly depend on the details of the MSP luminosity function (in particular, its high luminosity end) and other explicit or tacit assumptions on the MSP statistical properties, which we discuss. Notably, for the first time we study the importance of the possible secondary emission of the MSPs in the Galactic Center, i.e. the emission via inverse Compton losses of electrons injected in the interstellar medium. Differently from a majority of other authors, we find that within current uncertainties a large if not dominant contribution of MSPs to the excess cannot be excluded. We also show that the sensitivities of future instruments or possibly already of the latest LAT data analysis (Pass 8) provide good perspectives to test this scenario by resolving a significant number of MSPs.

  7. A Measurement of the Spatial Distribution of Diffuse TeV Gamma Ray Emission from the Galactic Plane with Milagro

    SciTech Connect

    Abdo, A.A.; Allen, B.; Aune, T.; Berley, D.; Blaufuss, E.; Casanova, S.; Chen, C.; Dingus, B.L.; Ellsworth, R.W.; Fleysher, L.; Fleysher, R.; Gonzalez, M.M.; Goodman, J.A.; Hoffman, C.M.; H'untemeyer, P.H.; Kolterman, B.E.; Lansdell, C.P.; Linnemann, J.T.; McEnery, J.E.; Mincer, A.I.; Nemethy, I.V.Moskalenko P.

    2008-05-14

    Diffuse {gamma}-ray emission produced by the interaction of cosmic-ray particles with matter and radiation in the Galaxy can be used to probe the distribution of cosmic rays and their sources in different regions of the Galaxy. With its large field of view and long observation time, the Milagro Gamma Ray Observatory is an ideal instrument for surveying large regions of the Northern Hemisphere sky and for detecting diffuse {gamma}-ray emission at very high energies. Here, the spatial distribution and the flux of the diffuse {gamma}-ray emission in the TeV energy range with a median energy of 15 TeV for Galactic longitudes between 30{sup o} and 110{sup o} and between 136{sup o} and 216{sup o} and for Galactic latitudes between -10{sup o} and 10{sup o} are determined. The measured fluxes are consistent with predictions of the GALPROP model everywhere except for the Cygnus region (l {element_of} [65{sup o}, 85{sup o}]). For the Cygnus region, the flux is twice the predicted value. This excess can be explained by the presence of active cosmic ray sources accelerating hadrons which interact with the local dense interstellar medium and produce gamma rays through pion decay.

  8. Automotive headlighting: effect of foreground illumination.

    PubMed

    Olson, P L; Sivak, M

    1983-12-01

    Described are studies of the relationship between the level of foreground illumination provided by automotive headlamps and the driver's eye-fixation pattern and ability to identify objects ahead of the car. Analysis indicates that the driver's eye fixations tended to move further from the car at high levels of foreground illumination. There were no differences in distance of target identification as a function of level of foreground illumination. PMID:6664782

  9. Evidence for a Very Low-column Density Hole in the Galactic Halo in the Direction of the High Latitude Molecular Cloud MBM 16

    NASA Astrophysics Data System (ADS)

    Liu, W.; Galeazzi, M.; Ursino, E.

    2016-01-01

    Shadow observations are the only way to observe emission from the galactic halo (GH) and/or the circumgalactic medium (CGM) free of any foreground contamination from local hot bubble (LHB) and solar wind charge exchange (SWCX). We analyzed data from a shadow observation in the direction of the high latitude, neutral hydrogen cloud MBM 16 with Suzaku. We found that all emission can be accounted for by foreground emission from LHB and SWCX, plus power-law emission associated with unresolved point sources. The GH/CGM in the direction of MBM 16 is negligible or inexistent in our observation, with upper limits on the emission measure of 9× {10}-4 pc cm-6 (90% C.L.-solar metallicity), at the lowest end of current estimates.

  10. Hydrogen Emission Line n110 rarr n109: Detection at 5009 Megahertz in Galactic H II Regions.

    PubMed

    Höglund, B; Mezger, P G

    1965-10-15

    The hydrogen emission line n(1l0) --> n(109) at the frequency 5009 megahertz which was predicted by Kardashev has been detected in M 17, Orion, and nine other galactic H II regions with the 42.7-m (140-foot) telescope and a 20-channel receiver at the National Radio Astronomy Observatory. The measured product of the half-power width of the line times the ratio of line-to-continuum brightness temperature is larger than that predicted by Kardashev's theory. The radial velocity obtained for M 17 and Orion agrees well with optical measurements. The search for a similar line of excited helium was without success. PMID:17742362

  11. OPENING THE 21 cm EPOCH OF REIONIZATION WINDOW: MEASUREMENTS OF FOREGROUND ISOLATION WITH PAPER

    SciTech Connect

    Pober, Jonathan C.; Parsons, Aaron R.; Ali, Zaki; Aguirre, James E.; Moore, David F.; Bradley, Richard F.; Carilli, Chris L.; DeBoer, Dave; Dexter, Matthew; MacMahon, Dave; Gugliucci, Nicole E.; Jacobs, Daniel C.; Klima, Patricia J.; Manley, Jason; Walbrugh, William P.; Stefan, Irina I.

    2013-05-10

    We present new observations with the Precision Array for Probing the Epoch of Reionization with the aim of measuring the properties of foreground emission for 21 cm epoch of reionization (EoR) experiments at 150 MHz. We focus on the footprint of the foregrounds in cosmological Fourier space to understand which modes of the 21 cm power spectrum will most likely be compromised by foreground emission. These observations confirm predictions that foregrounds can be isolated to a {sup w}edge{sup -}like region of two-dimensional (k , k{sub Parallel-To })-space, creating a window for cosmological studies at higher k{sub Parallel-To} values. We also find that the emission extends past the nominal edge of this wedge due to spectral structure in the foregrounds, with this feature most prominent on the shortest baselines. Finally, we filter the data to retain only this ''unsmooth'' emission and image its specific k{sub Parallel-To} modes. The resultant images show an excess of power at the lowest modes, but no emission can be clearly localized to any one region of the sky. This image is highly suggestive that the most problematic foregrounds for 21 cm EoR studies will not be easily identifiable bright sources, but rather an aggregate of fainter emission.

  12. Opening the 21 cm Epoch of Reionization Window: Measurements of Foreground Isolation with PAPER

    NASA Astrophysics Data System (ADS)

    Pober, Jonathan C.; Parsons, Aaron R.; Aguirre, James E.; Ali, Zaki; Bradley, Richard F.; Carilli, Chris L.; DeBoer, Dave; Dexter, Matthew; Gugliucci, Nicole E.; Jacobs, Daniel C.; Klima, Patricia J.; MacMahon, Dave; Manley, Jason; Moore, David F.; Stefan, Irina I.; Walbrugh, William P.

    2013-05-01

    We present new observations with the Precision Array for Probing the Epoch of Reionization with the aim of measuring the properties of foreground emission for 21 cm epoch of reionization (EoR) experiments at 150 MHz. We focus on the footprint of the foregrounds in cosmological Fourier space to understand which modes of the 21 cm power spectrum will most likely be compromised by foreground emission. These observations confirm predictions that foregrounds can be isolated to a "wedge"-like region of two-dimensional (k , k ∥)-space, creating a window for cosmological studies at higher k ∥ values. We also find that the emission extends past the nominal edge of this wedge due to spectral structure in the foregrounds, with this feature most prominent on the shortest baselines. Finally, we filter the data to retain only this "unsmooth" emission and image its specific k ∥ modes. The resultant images show an excess of power at the lowest modes, but no emission can be clearly localized to any one region of the sky. This image is highly suggestive that the most problematic foregrounds for 21 cm EoR studies will not be easily identifiable bright sources, but rather an aggregate of fainter emission.

  13. Foreground-induced biases in CMB polarimeter self-calibration

    NASA Astrophysics Data System (ADS)

    Abitbol, Maximilian H.; Hill, James; Johnson, Bradley

    2016-06-01

    Precise polarization measurements of the cosmic microwave background (CMB) require accurate knowledge of the instrument orientation relative to the sky frame used to define the cosmological Stokes parameters. Suitable celestial calibration sources that could be used to measure the polarimeter orientation angle are limited, so current experiments commonly `self-calibrate.' The self-calibration method exploits the theoretical fact that the EB and TB cross-spectra of the CMB vanish in the standard cosmological model, so any detected EB and TB signals must be due to systematic errors. However, this assumption neglects the fact that polarized Galactic foregrounds in a given portion of the sky may have non-zero EB and TB cross-spectra. If these foreground signals remain in the observations, then they will bias the self-calibrated telescope polarization angle and produce a spurious B-mode signal. In this paper, we estimate the foreground-induced bias for various instrument configurations and then expand the self-calibration formalism to account for polarized foreground signals. Assuming the EB correlation signal for dust is in the range constrained by angular power spectrum measurements from Planck at 353 GHz (scaled down to 150 GHz), then the bias is negligible for high angular resolution experiments, which have access to CMB-dominated high 'ell' modes with which to self-calibrate. Low-resolution experiments observing particularly dusty sky patches can have a bias as large as 0.5°. A miscalibration of this magnitude generates a spurious BB signal corresponding to a tensor-to-scalar ratio of approximately r ~ 2 × 10-3, within the targeted range of planned experiments.

  14. Foreground-induced biases in CMB polarimeter self-calibration

    NASA Astrophysics Data System (ADS)

    Abitbol, Maximilian H.; Hill, J. Colin; Johnson, Bradley R.

    2016-04-01

    Precise polarization measurements of the cosmic microwave background (CMB) require accurate knowledge of the instrument orientation relative to the sky frame used to define the cosmological Stokes parameters. Suitable celestial calibration sources that could be used to measure the polarimeter orientation angle are limited, so current experiments commonly `self-calibrate.' The self-calibration method exploits the theoretical fact that the EB and TB cross-spectra of the CMB vanish in the standard cosmological model, so any detected EB and TB signals must be due to systematic errors. However, this assumption neglects the fact that polarized Galactic foregrounds in a given portion of the sky may have non-zero EB and TB cross-spectra. If these foreground signals remain in the observations, then they will bias the self-calibrated telescope polarization angle and produce a spurious B-mode signal. In this paper, we estimate the foreground-induced bias for various instrument configurations and then expand the self-calibration formalism to account for polarized foreground signals. Assuming the EB correlation signal for dust is in the range constrained by angular power spectrum measurements from Planck at 353 GHz (scaled down to 150 GHz), then the bias is negligible for high angular resolution experiments, which have access to CMB-dominated high ℓ modes with which to self-calibrate. Low-resolution experiments observing particularly dusty sky patches can have a bias as large as 0.5°. A miscalibration of this magnitude generates a spurious BB signal corresponding to a tensor-to-scalar ratio of approximately r ˜ 2 × 10-3, within the targeted range of planned experiments.

  15. EXTENDED SUBMILLIMETER EMISSION OF THE GALACTIC CENTER AND NEAR-INFRARED/SUBMILLIMETER VARIABILITY OF ITS SUPERMASSIVE BLACK HOLE

    SciTech Connect

    Garcia-Marin, M.; Eckart, A.; Witzel, G.; Bremer, M.; Kunneriath, D.; Sabha, N.; Straubmeier, C.; Weiss, A.; Zamaninasab, M.; Morris, M. R.; Schoedel, R.; Nishiyama, S.; Baganoff, F.; Karas, V.; Dovciak, M.; Duschl, W. J.; Moultaka, J.; Najarro, F.; Muzic, K.; Vogel, S. N.

    2011-09-10

    The innermost tens of parsecs of our Galaxy are characterized by the presence of molecular cloud complexes surrounding Sgr A*, the radiative counterpart of the supermassive black hole ({approx}4 x 10{sup 6} M{sub sun}) at the Galactic center. We seek to distinguish the different physical mechanisms that dominate the molecular clouds at the Galactic center, with special emphasis on the circumnuclear disk (CND). We also want to study the energy flow and model the variable emission of Sgr A*. Our study is based on NIR and submillimeter (sub-mm) observations. Using sub-mm maps, we describe the complex morphology of the molecular clouds and the circumnuclear disk, along with their masses (of order 10{sup 5}-10{sup 6} M{sub sun}), and derive also the temperature and spectral index maps of the regions under study. We conclude that the average temperature of the dust is 14 {+-} 4 K. The spectral index map shows that the 20 and 50 km s{sup -1} clouds are dominated by dust emission. Comparatively, in the CND and its surroundings the spectral indices decrease toward Sgr A* and range between about 1 and -0.6. These values are mostly explained with a combination of dust, synchrotron, and free-free emission in different ratios. The presence of non-thermal emission also accounts for the apparent low temperatures derived in these areas, indicating their unreliability. The Sgr A* light curves show significant flux density excursions in both the NIR and sub-mm domains. We have defined a classification system to account for the NIR variability of Sgr A*. Also, we have modeled on the NIR/sub-mm events. From our modeling results we can infer a sub-mm emission delay with respect to the NIR; we argue that the delay is due to the adiabatic expansion of the synchrotron source components.

  16. Recognizing foreground-background interaction

    NASA Astrophysics Data System (ADS)

    Jenkins, Jeffrey; Szu, Harold

    2010-04-01

    Can the background affect a foreground target in distant, low-quality imagery? If it does, it might occur in our mind, or perhaps it may represent a snapshot of our early vision. An affirmative answer, one way or another, may affect our current understanding of this phenomena and potentially for related applications. How can we be sure about this in the psycho-physical sense? We begin with the physiology of our brain's homeostasis, of which an isothermal equilibrium is characterized by the minimum of Helmholtz isothermal Free Energy: A = U - T0S >= 0, where T0 = 37°C, the Boltzmann Entropy S = KB1n(W), and U is the unknown internal energy to be computed.

  17. RADIO SYNCHROTRON EMISSION FROM A BOW SHOCK AROUND THE GAS CLOUD G2 HEADING TOWARD THE GALACTIC CENTER

    SciTech Connect

    Narayan, Ramesh; Sironi, Lorenzo; Oezel, Feryal

    2012-10-01

    A dense ionized cloud of gas has been recently discovered to be moving directly toward the supermassive black hole, Sgr A*, at the Galactic center. In 2013 June, at the pericenter of its highly eccentric orbit, the cloud will be approximately 3100 Schwarzschild radii from the black hole and will move supersonically through the ambient hot gas with a velocity of v{sub p} Almost-Equal-To 5400 km s{sup -1}. A bow shock is likely to form in front of the cloud and could accelerate electrons to relativistic energies. We estimate via particle-in-cell simulations the energy distribution of the accelerated electrons and show that the non-thermal synchrotron emission from these electrons might exceed the quiescent radio emission from Sgr A* by a factor of several. The enhanced radio emission should be detectable at GHz and higher frequencies around the time of pericentric passage and in the following months. The bow shock emission is expected to be displaced from the quiescent radio emission of Sgr A* by {approx}33 mas. Interferometric observations could resolve potential changes in the radio image of Sgr A* at wavelengths {approx}< 6 cm.

  18. Constraints on the neutrino emission from the Galactic Ridge with the ANTARES telescope

    NASA Astrophysics Data System (ADS)

    Adrián-Martínez, S.; Albert, A.; André, M.; Anghinolfi, M.; Anton, G.; Ardid, M.; Aubert, J.-J.; Avgitas, T.; Baret, B.; Barrios-Martí, J.; Basa, S.; Bertin, V.; Biagi, S.; Bormuth, R.; Bouwhuis, M. C.; Bruijn, R.; Brunner, J.; Busto, J.; Capone, A.; Caramete, L.; Carr, J.; Celli, S.; Chiarusi, T.; Circella, M.; Coleiro, A.; Coniglione, R.; Costantini, H.; Coyle, P.; Creusot, A.; Deschamps, A.; De Bonis, G.; Distefano, C.; Donzaud, C.; Dornic, D.; Drouhin, D.; Eberl, T.; El Bojaddaini, I.; Elsässer, D.; Enzenhöfer, A.; Fehn, K.; Felis, I.; Fusco, L. A.; Galatà, S.; Gay, P.; Geißelsöder, S.; Geyer, K.; Giordano, V.; Gleixner, A.; Glotin, H.; Gracia-Ruiz, R.; Graf, K.; Hallmann, S.; van Haren, H.; Heijboer, A. J.; Hello, Y.; Hernández-Rey, J. J.; Hößl, J.; Hofestädt, J.; Hugon, C.; Illuminati, G.; James, C. W.; de Jong, M.; Kadler, M.; Kalekin, O.; Katz, U.; Kießling, D.; Kouchner, A.; Kreter, M.; Kreykenbohm, I.; Kulikovskiy, V.; Lachaud, C.; Lahmann, R.; Lefèvre, D.; Leonora, E.; Loucatos, S.; Marcelin, M.; Margiotta, A.; Marinelli, A.; Martínez-Mora, J. A.; Mathieu, A.; Michael, T.; Migliozzi, P.; Moussa, A.; Mueller, C.; Nezri, E.; Păvălaş, G. E.; Pellegrino, C.; Perrina, C.; Piattelli, P.; Popa, V.; Pradier, T.; Racca, C.; Riccobene, G.; Roensch, K.; Saldaña, M.; Samtleben, D. F. E.; Sánchez-Losa, A.; Sanguineti, M.; Sapienza, P.; Schnabel, J.; Schüssler, F.; Seitz, T.; Sieger, C.; Spurio, M.; Stolarczyk, Th.; Taiuti, M.; Trovato, A.; Tselengidou, M.; Turpin, D.; Tönnis, C.; Vallage, B.; Vallée, C.; Van Elewyck, V.; Visser, E.; Vivolo, D.; Wagner, S.; Wilms, J.; Zornoza, J. D.; Zúñiga, J.

    2016-09-01

    A highly significant excess of high-energy astrophysical neutrinos has been reported by the IceCube Collaboration. Some features of the energy and declination distributions of IceCube events hint at a North/South asymmetry of the neutrino flux. This could be due to the presence of the bulk of our Galaxy in the Southern hemisphere. The ANTARES neutrino telescope, located in the Mediterranean Sea, has been taking data since 2007. It offers the best sensitivity to muon neutrinos produced by galactic cosmic ray interactions in this region of the sky. In this letter a search for an extended neutrino flux from the Galactic Ridge region is presented. Different models of neutrino production by cosmic ray propagation are tested. No excess of events is observed and upper limits for different neutrino flux spectral indices Γ are set. For Γ = 2.4 the 90% confidence level flux upper limit at 100 TeV for one neutrino flavour corresponds to Φ01 f (100 TeV) = 2.0 ṡ10-17 GeV-1cm-2s-1sr-1. Under this assumption, at most two events of the IceCube cosmic candidates can originate from the Galactic Ridge. A simple power-law extrapolation of the Fermi-LAT flux to account for IceCube High Energy Starting Events is excluded at 90% confidence level.

  19. THE ROLE OF THE ACCRETION DISK, DUST, AND JETS IN THE IR EMISSION OF LOW-LUMINOSITY ACTIVE GALACTIC NUCLEI

    SciTech Connect

    Mason, R. E.; Ramos Almeida, C.; Alonso-Herrero, A.

    2013-11-10

    We use recent high-resolution infrared (IR; 1-20 μm) photometry to examine the origin of the IR emission in low-luminosity active galactic nuclei (LLAGN). The data are compared with published model fits that describe the spectral energy distribution (SED) of LLAGN in terms of an advection-dominated accretion flow, truncated thin accretion disk, and jet. The truncated disk in these models is usually not luminous enough to explain the observed IR emission, and in all cases its spectral shape is much narrower than the broad IR peaks in the data. Synchrotron radiation from the jet appears to be important in very radio-loud nuclei, but the detection of strong silicate emission features in many objects indicates that dust must also contribute. We investigate this point by fitting the IR SED of NGC 3998 using dusty torus and optically thin (τ{sub mid-IR} ∼ 1) dust shell models. While more detailed modeling is necessary, these initial results suggest that dust may account for the nuclear mid-IR emission of many LLAGN.

  20. EFFECTS OF AN ACCRETION DISK WIND ON THE PROFILE OF THE BALMER EMISSION LINES FROM ACTIVE GALACTIC NUCLEI

    SciTech Connect

    Flohic, Helene M. L. G.; Eracleous, Michael; Bogdanovic, Tamara E-mail: mce@astro.psu.edu

    2012-07-10

    We explore the connection between active galactic nuclei (AGNs) with single- and double-peaked broad Balmer emission lines by using models dealing with radiative transfer effects through a disk wind. Our primary goal is to assess the applicability of the Murray and Chiang model by making an extensive and systematic comparison of the model predictions with data. In the process, we also verify the original derivation and evaluate the importance of general relativistic effects. As the optical depth through the emission layer increases, the peaks of a double-peaked profile move closer and eventually merge, producing a single peak. The properties of the emission line profile depend as sensitively on the geometric parameters of the line-emitting portion of the disk as they do on the disk-wind parameters. Using a parameter range that encompasses the expected characteristics of the broad-line regions in AGNs, we construct a database of model profiles and measure a set of diagnostic properties. Comparisons of the model profiles with emission lines from a subset of Sloan digital Sky Survey quasars show that observed lines are consistent with moderately large optical depth in the disk wind and a range of disk inclinations i {approx}< 45 Degree-Sign . Including relativistic effects is necessary to produce the asymmetries of observed line profiles.

  1. Mass content around Galactic VHE sources

    NASA Astrophysics Data System (ADS)

    de Ona Wilhelmi, Emma; Pedaletti, Giovanna; Torres, Diego; Natale, Giovanni

    2015-08-01

    A large number of Galactic very-high energy (VHE; E>100 GeV) gamma-ray sources have been discovered in the past years with ground-based Cherenkov telescopes, being a large fraction of them still unidentified. The association of these VHE sources with regions of the sky rich in dust and gas has been noticed in the study of individual VHE sources. These regions are usually associated with environments with high stellar activity, implying the presence of evolved objects like supernova remnants or pulsar wind nebulae. The estimation of the mass content around VHE sources is crucial to understand acceleration in such sources, specially when the emission is due to hadronic interaction of accelerated particles with the target mass. Using the recently released all-sky maps of astrophysical foregrounds of the Planck satellite, we tested the correlation level at large scale between the Galactic VHE population and mass enhancement. We also explored the possibility that the unidentified sources are located in ambients particularly rich in material content unaccounted by traditional radio (CO lines) tracers. The results of this investigation will be presented and the implications on the VHE emission discussed.

  2. Contribution of the 6.7 keV Emission line from Stellar Flares to the Galactic Ridge X-ray Emission

    NASA Astrophysics Data System (ADS)

    Nwachukwu Eze, Romanus; Eze, Ambrose; Nwafor, Jude; Esaenwi, Sudum; Okeke, Pius; Ebisawa, Ken; Smith, Randall

    2015-08-01

    Stellar flares create sudden bursts of hot plasma that contain a wide range of temperatures, and are capable of generating 6.7 keV Fe XXV emission line via electronic collisional excitation. Using the measured 6.7 keV fluxes from a collection of Suzaku-observed stellar flares as a baseline, we estimate their contribution to the 6.7 keV emission line from the Galactic Ridge X-ray emission (GRXE). We modeled the extracted stellar flares’ spectra from our sources with an absorbed Bremstrahlung. We found strong 6.7 keV emission line from the extracted stellar flares’ spectra which is similar to the observed 6.7 keV emission line from the GRXE, while the 6.4 and 7.0 keV lines appear to be faint. The present result supports the earlier result that stellar flares contribute significantly to the total luminosity of the GRXE and that the GRXE luminosity could be primarily explained via hard X-ray emitting symbiotic stars (hSSs), and magnetic cataclysmic variables (mCVs), along with other white dwarf binary systems and stellar flares.

  3. EXTENDED X-RAY EMISSION IN THE H I CAVITY OF NGC 4151: GALAXY-SCALE ACTIVE GALACTIC NUCLEUS FEEDBACK?

    SciTech Connect

    Wang Junfeng; Fabbiano, Giuseppina; Risaliti, Guido; Elvis, Martin; Zezas, Andreas; Mundell, Carole G.; Dumas, Gaelle; Schinnerer, Eva

    2010-08-20

    We present the Chandra discovery of soft diffuse X-ray emission in NGC 4151 (L{sub 0.5-2 keV} {approx} 10{sup 39} erg s{sup -1}), extending {approx}2 kpc from the active nucleus and filling in the cavity of the H I material. The best fit to the X-ray spectrum requires either a kT {approx} 0.25 keV thermal plasma or a photoionized component. In the thermal scenario, hot gas heated by the nuclear outflow would be confined by the thermal pressure of the H I gas and the dynamic pressure of inflowing neutral material in the galactic disk. In the case of photoionization, the nucleus must have experienced an Eddington limit outburst. For both scenarios, the active galactic nucleus (AGN)-host interaction in NGC 4151 must have occurred relatively recently (some 10{sup 4} yr ago). This very short timescale to the last episode of high activity phase may imply such outbursts occupy {approx_gt}1% of AGN lifetime.

  4. Very-high-energy gamma-ray emission from the direction of the Galactic globular cluster Terzan 5

    NASA Astrophysics Data System (ADS)

    H.E.S.S. Collaboration; Abramowski, A.; Acero, F.; Aharonian, F.; Akhperjanian, A. G.; Anton, G.; Balzer, A.; Barnacka, A.; Barres de Almeida, U.; Becherini, Y.; Becker, J.; Behera, B.; Bernlöhr, K.; Bochow, A.; Boisson, C.; Bolmont, J.; Bordas, P.; Brucker, J.; Brun, F.; Brun, P.; Bulik, T.; Büsching, I.; Carrigan, S.; Casanova, S.; Cerruti, M.; Chadwick, P. M.; Charbonnier, A.; Chaves, R. C. G.; Cheesebrough, A.; Chounet, L.-M.; Clapson, A. C.; Coignet, G.; Cologna, G.; Conrad, J.; Dalton, M.; Daniel, M. K.; Davids, I. D.; Degrange, B.; Deil, C.; Dickinson, H. J.; Djannati-Ataï, A.; Domainko, W.; Drury, L. O'C.; Dubois, F.; Dubus, G.; Dutson, K.; Dyks, J.; Dyrda, M.; Egberts, K.; Eger, P.; Espigat, P.; Fallon, L.; Farnier, C.; Fegan, S.; Feinstein, F.; Fernandes, M. V.; Fiasson, A.; Fontaine, G.; Förster, A.; Füßling, M.; Gallant, Y. A.; Gast, H.; Gérard, L.; Gerbig, D.; Giebels, B.; Glicenstein, J. F.; Glück, B.; Goret, P.; Göring, D.; Häffner, S.; Hague, J. D.; Hampf, D.; Hauser, M.; Heinz, S.; Heinzelmann, G.; Henri, G.; Hermann, G.; Hinton, J. A.; Hoffmann, A.; Hofmann, W.; Hofverberg, P.; Holler, M.; Horns, D.; Jacholkowska, A.; de Jager, O. C.; Jahn, C.; Jamrozy, M.; Jung, I.; Kastendieck, M. A.; Katarzyński, K.; Katz, U.; Kaufmann, S.; Keogh, D.; Khangulyan, D.; Khélifi, B.; Klochkov, D.; Kluźniak, W.; Kneiske, T.; Komin, Nu.; Kosack, K.; Kossakowski, R.; Laffon, H.; Lamanna, G.; Lennarz, D.; Lohse, T.; Lopatin, A.; Lu, C.-C.; Marandon, V.; Marcowith, A.; Masbou, J.; Maurin, D.; Maxted, N.; McComb, T. J. L.; Medina, M. C.; Méhault, J.; Moderski, R.; Moulin, E.; Naumann, C. L.; Naumann-Godo, M.; de Naurois, M.; Nedbal, D.; Nekrassov, D.; Nguyen, N.; Nicholas, B.; Niemiec, J.; Nolan, S. J.; Ohm, S.; de Oña Wilhelmi, D.; Opitz, B.; Ostrowski, M.; Oya, I.; Panter, M.; Paz Arribas, M.; Pedaletti, G.; Pelletier, G.; Petrucci, P.-O.; Pita, S.; Pühlhofer, G.; Punch, M.; Quirrenbach, A.; Raue, M.; Rayner, S. M.; Reimer, A.; Reimer, O.; Renaud, M.; de los Reyes, R.; Rieger, F.; Ripken, J.; Rob, L.; Rosier-Lees, S.; Rowell, G.; Rudak, B.; Rulten, C. B.; Ruppel, J.; Ryde, F.; Sahakian, V.; Santangelo, A.; Schlickeiser, R.; Schöck, F. M.; Schulz, A.; Schwanke, U.; Schwarzburg, S.; Schwemmer, S.; Sikora, M.; Skilton, J. L.; Sol, H.; Spengler, G.; Stawarz, Ł.; Steenkamp, R.; Stegmann, C.; Stinzing, F.; Stycz, K.; Sushch, I.; Szostek, A.; Tavernet, J.-P.; Terrier, R.; Tluczykont, M.; Valerius, K.; van Eldik, C.; Vasileiadis, G.; Venter, C.; Vialle, J. P.; Viana, A.; Vincent, P.; Völk, H. J.; Volpe, F.; Vorobiov, S.; Vorster, M.; Wagner, S. J.; Ward, M.; White, R.; Wierzcholska, A.; Zacharias, M.; Zajczyk, A.; Zdziarski, A. A.; Zech, A.; Zechlin, H.-S.

    2011-07-01

    The HESS very-high-energy (VHE, E > 0.1 TeV) gamma-ray telescope system has discovered a new source, HESS J1747-248. The measured integral flux is (1.2 ± 0.3) × 10-12 cm-2 s-1 above 440 GeV for a power-law photon spectral index of 2.5 ± 0.3stat ± 0.2sys. The VHE gamma-ray source is located in the close vicinity of the Galactic globular cluster Terzan 5 and extends beyond the HESS point spread function (0.07°). The probability of a chance coincidence with Terzan 5 and an unrelated VHE source is quite low (~10-4). With the largest population of identified millisecond pulsars (msPSRs), a very high core stellar density and the brightest GeV range flux as measured by Fermi-LAT, Terzan 5 stands out among Galactic globular clusters. The properties of the VHE source are briefly discussed in the context of potential emission mechanisms, notably in relation to msPSRs. Interpretation of the available data accommodates several possible origins for this VHE gamma-ray source, although none of them offers a satisfying explanation of its peculiar morphology.

  5. Nature of the Diffuse Near-Infrared Emission in the Innermost Arcsecond of the Galactic Center

    NASA Astrophysics Data System (ADS)

    Sabha, Nadeen; Eckart, Andreas; Merritt, David; Zamaninasab, Mohammad

    2015-01-01

    We study the diffuse NIR background light associated with the cluster of high velocity stars at the Galactic Center, known as the S-stars. We use the luminosity function of the cluster members, the distribution of the diffuse background light and the stellar number density counts to investigate the amount of stellar and dark mass associated with the cluster in the immediate vicinity of the supermassive black hole. We show that both the total mass, and the number, of objects within an S-star's orbit can be constrained using observed changes in the star's orbital elements.

  6. Possible dark matter origin of the gamma ray emission from the Galactic Center observed by HESS

    NASA Astrophysics Data System (ADS)

    Cembranos, J. A. R.; Gammaldi, V.; Maroto, A. L.

    2012-11-01

    We show that the gamma ray spectrum observed with the HESS array of Cherenkov telescopes coming from the Galactic Center region and identified with the source HESS J1745-290 is well fitted by the secondary photons coming from dark matter (DM) annihilation over a diffuse power law background. The amount of photons and morphology of the signal localized within a region of few parsecs, require compressed DM profiles as those resulting from baryonic contraction, which offer ˜103 enhancements in the signal over DM alone simulations. The fitted background from HESS data is consistent with recent Fermi-LAT observations of the same region.

  7. Extreme optical Fe II emission in luminous IRAS active galactic nuclei

    NASA Technical Reports Server (NTRS)

    Lipari, Sebastian; Terlevich, Roberto; Macchetto, F.

    1993-01-01

    Results of a program of studies and observations of strong optical Fe II emission in luminous and ultraluminous IRAS AGN are presented. New spectroscopic observations and studies of three known ultraluminous IRAS AGN with extreme optical Fe II emission, the discovery that PHL 1092 is a new ultraluminous IRAS AGN, and the detection of two new AGN with strongly variable flux in the optical Fe II emission lines are reported. These results are used to test the correlations between the Fe II emission and properties at other wavelengths such as the L(IR) and the radio emission. IR AGN with extreme Fe II emission are found to belong to a very important group of AGN, whose properties provide insight into the origin of the extreme Fe II emission and into the relation between the starburst and AGN phenomena.

  8. Galactic Center gamma-ray ''excess'' from an active past of the Galactic Centre?

    SciTech Connect

    Petrović, Jovana; Serpico, Pasquale Dario; Zaharijaš, Gabrijela E-mail: serpico@lapth.cnrs.fr

    2014-10-01

    Several groups have recently claimed evidence for an unaccounted gamma-ray excess over the diffuse backgrounds at few GeV in the Fermi-LAT data in a region around the Galactic Center, consistent with a dark matter annihilation origin. We demonstrate that the main spectral and angular features of this excess can be reproduced if they are mostly due to inverse Compton emission from high-energy electrons injected in a burst event of ∼ 10{sup 52}÷10{sup 53} erg roughly O(10{sup 6}) years ago. We consider this example as a proof of principle that time-dependent phenomena need to be understood and accounted for—together with detailed diffuse foregrounds and unaccounted ''steady state'' astrophysical sources—before any robust inference can be made about dark matter signals at the Galactic Center. In addition, we point out that the timescale suggested by our study, which controls both the energy cutoff and the angular extension of the signal, intriguingly matches (together with the energy budget) what is indirectly inferred by other evidences suggesting a very active Galactic Center in the past, for instance related to intense star formation and accretion phenomena.

  9. Galactic Center gamma-ray ``excess'' from an active past of the Galactic Centre?

    NASA Astrophysics Data System (ADS)

    Petrović, Jovana; Dario Serpico, Pasquale; Zaharijaš, Gabrijela

    2014-10-01

    Several groups have recently claimed evidence for an unaccounted gamma-ray excess over the diffuse backgrounds at few GeV in the Fermi-LAT data in a region around the Galactic Center, consistent with a dark matter annihilation origin. We demonstrate that the main spectral and angular features of this excess can be reproduced if they are mostly due to inverse Compton emission from high-energy electrons injected in a burst event of ~ 1052÷1053 erg roughly Script O(106) years ago. We consider this example as a proof of principle that time-dependent phenomena need to be understood and accounted for—together with detailed diffuse foregrounds and unaccounted ``steady state'' astrophysical sources—before any robust inference can be made about dark matter signals at the Galactic Center. In addition, we point out that the timescale suggested by our study, which controls both the energy cutoff and the angular extension of the signal, intriguingly matches (together with the energy budget) what is indirectly inferred by other evidences suggesting a very active Galactic Center in the past, for instance related to intense star formation and accretion phenomena.

  10. THE LISA GRAVITATIONAL WAVE FOREGROUND: A STUDY OF DOUBLE WHITE DWARFS

    SciTech Connect

    Ruiter, Ashley J.; Belczynski, Krzysztof; Larson, Shane L. E-mail: kbelczyn@nmsu.ed E-mail: gabriel.j.williams@gmail.co

    2010-07-10

    Double white dwarfs (WDs) are expected to be a source of confusion-limited noise for the future gravitational wave observatory LISA. In a specific frequency range, this 'foreground noise' is predicted to rise above the instrumental noise and hinder the detection of other types of signals, e.g., gravitational waves arising from stellar-mass objects inspiraling into massive black holes. In many previous studies, only detached populations of compact object binaries have been considered in estimating the LISA gravitational wave foreground signal. Here, we investigate the influence of compact object detached and Roche-Lobe overflow (RLOF) Galactic binaries on the shape and strength of the LISA signal. Since >99% of remnant binaries that have orbital periods within the LISA sensitivity range are WD binaries, we consider only these binaries when calculating the LISA signal. We find that the contribution of RLOF binaries to the foreground noise is negligible at low frequencies, but becomes significant at higher frequencies, pushing the frequency at which the foreground noise drops below the instrumental noise to >6 mHz. We find that it is important to consider the population of mass-transferring binaries in order to obtain an accurate assessment of the foreground noise on the LISA data stream. However, we estimate that there still exists a sizeable number ({approx}11,300) of Galactic double WD binaries that will have a signal-to-noise ratio >5, and thus will be potentially resolvable with LISA. We present the LISA gravitational wave signal from the Galactic population of WD binaries, show the most important formation channels contributing to the LISA disk and bulge populations, and discuss the implications of these new findings.