283 research outputs found

    Uniform color space analysis of LACIE image products

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    The author has identified the following significant results. Analysis and comparison of image products generated by different algorithms show that the scaling and biasing of data channels for control of PFC primaries lead to loss of information (in a probability-of misclassification sense) by two major processes. In order of importance they are: neglecting the input of one channel of data in any one image, and failing to provide sufficient color resolution of the data. The scaling and biasing approach tends to distort distance relationships in data space and provides less than desirable resolution when the data variation is typical of a developed, nonhazy agricultural scene

    Investigation of techniques for inventorying forested regions. Volume 2: Forestry information system requirements and joint use of remotely sensed and ancillary data

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    The author has identified the following significant results. Effects of terrain topography in mountainous forested regions on LANDSAT signals and classifier training were found to be significant. The aspect of sloping terrain relative to the sun's azimuth was the major cause of variability. A relative insolation factor could be defined which, in a single variable, represents the joint effects of slope and aspect and solar geometry on irradiance. Forest canopy reflectances were bound, both through simulation, and empirically, to have nondiffuse reflectance characteristics. Training procedures could be improved by stratifying in the space of ancillary variables and training in each stratum. Application of the Tasselled-Cap transformation for LANDSAT data acquired over forested terrain could provide a viable technique for data compression and convenient physical interpretations

    Investigation of spatial misregistration effects in multispectral scanner data

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    The author has identified the following significant results. A model for estimating the expected proportion of multiclass pixels in a scene was generalized and extended to include misregistration effects. Another substantial effort was the development of a simulation model to generate signatures to represent the distributions of signals from misregistered multiclass pixels, based on single class signatures. Spatial misregistration causes an increase in the proportion of multiclass pixels in a scene and a decorrelation between signals in misregistered data channels. The multiclass pixel proportion estimation model indicated that this proportion is strongly dependent on the pixel perimeter and on the ratio of the total perimeter of the fields in the scene to the area of the scene. Test results indicated that expected values computed with this model were similar to empirical measurements made of this proportion in four LACIE data segments

    An evaluation of the signature extension approach to large area crop inventories utilizing space image data

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    The author has identified the following significant results. Two examples of haze correction algorithms were tested: CROP-A and XSTAR. The CROP-A was tested in a unitemporal mode on data collected in 1973-74 over ten sample segments in Kansas. Because of the uniformly low level of haze present in these segments, no conclusion could be reached about CROP-A's ability to compensate for haze. It was noted, however, that in some cases CROP-A made serious errors which actually degraded classification performance. The haze correction algorithm XSTAR was tested in a multitemporal mode on 1975-76 LACIE sample segment data over 23 blind sites in Kansas and 18 sample segments in North Dakota, providing wide range of haze levels and other conditions for algorithm evaluation. It was found that this algorithm substantially improved signature extension classification accuracy when a sum-of-likelihoods classifier was used with an alien rejection threshold

    Wheat signature modeling and analysis for improved training statistics

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    The author has identified the following significant results. The spectral, spatial, and temporal characteristics of wheat and other signatures in LANDSAT multispectral scanner data were examined through empirical analysis and simulation. Irrigation patterns varied widely within Kansas; 88 percent of wheat acreage in Finney was irrigated and 24 percent in Morton, as opposed to less than 3 percent for western 2/3's of the State. The irrigation practice was definitely correlated with the observed spectral response; wheat variety differences produced observable spectral differences due to leaf coloration and different dates of maturation. Between-field differences were generally greater than within-field differences, and boundary pixels produced spectral features distinct from those within field centers. Multiclass boundary pixels contributed much of the observed bias in proportion estimates. The variability between signatures obtained by different draws of training data decreased as the sample size became larger; also, the resulting signatures became more robust and the particular decision threshold value became less important

    Very extended cold gas, star formation and outflows in the halo of a bright QSO at z>6

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    Past observations of QSO host galaxies at z >6 have found cold gas and star formation on compact scales of a few kiloparsecs. We present new high sensitivity IRAM PdBI follow-up observations of the [CII] 158micron emission line and FIR continuum in the host galaxy of SDSS J1148+5152, a luminous QSO at redshift 6.4189. We find that a large fraction of the gas traced by [CII] is at high velocities, up to ~1400 km/s relative to the systemic velocity, confirming the presence of a major quasar-driven outflow indicated by previous observations. The outflow has a complex morphology and reaches a maximum projected radius of ~30 kpc. The extreme spatial extent of the outflow allows us, for the first time in an external galaxy, to estimate mass-loss rate, kinetic power and momentum rate of the outflow as a function of the projected distance from the nucleus and the dynamical time-scale. These trends reveal multiple outflow events during the past 100 Myr, although the bulk of the mass, energy and momentum appear to have been released more recently, within the past ~20 Myr. Surprisingly, we discover that also the quiescent gas at systemic velocity is extremely extended. More specifically, we find that, while 30% of the [CII] within v\in(-200, 200) km/s traces a compact component that is not resolved by our observations, 70% of the [CII] emission in this velocity range is extended, with a projected FWHM size of 17.4+-1.4 kpc. We detect FIR continuum emission associated with both the compact and the extended [CII] components, although the extended FIR emission has a FWHM of 11+-3 kpc, thus smaller than the extended [CII] source. Overall, our results indicate that the cold gas traced by [CII] is distributed up to r~30 kpc. A large fraction of extended [CII] is likely associated with star formation on large scales, but the [CII] source extends well beyond the FIR continuum.Comment: Accepted for publication in A&A, 21 pages, 18 figures, 3 tables (v2: accepted version, discussion expanded in Sect. 3, 4 and in the Appendices, minor changes elsewhere

    The rest-frame UV-to-optical spectroscopy of APM 08279+5255 - BAL classification and black hole mass estimates

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    We present the analysis of the rest-frame optical-to-UV spectrum of APM 08279+5255, a well-known lensed broad absorption line (BAL) quasar at z=3.911z = 3.911. The spectroscopic data are taken with the optical DOLoRes and near-IR NICS instruments at TNG, and include the previously unexplored range between C III] λ\lambda1910 and [O III] λλ\lambda\lambda4959,5007. We investigate the possible presence of multiple BALs by computing "balnicity" and absorption indexes (i.e. BI, BI0_0 and AI) for the transitions Si IV λ\lambda1400, C IV λ\lambda1549, Al III λ\lambda1860 and Mg II λ\lambda2800. No clear evidence for the presence of absorption features is found in addition to the already known, prominent BAL associated to C IV, which supports a high-ionization BAL classification for APM 08279+5255. We also study the properties of the [O III], Hβ\beta and Mg II emission lines. We find that [O III] is intrinsically weak (F[OIII]/FHβ0.04F_{\rm [OIII]}/F_{\rm H\beta} \lesssim 0.04), as it is typically found in luminous quasars with a strongly blueshifted C IV emission line (\sim2500 km s1^{-1} for APM 08279+5255). We compute the single-epoch black hole mass based on Mg II and Hβ\beta broad emission lines, finding MBH=(2÷3)×1010μ1M_{\rm BH} = (2 \div 3) \times 10^{10}\mu^{-1} M_\odot, with the magnification factor μ\mu that can vary between 4 and 100 according to CO and rest-frame UV-to-mid-IR imaging respectively. Using a Mg II equivalent width (EW)-to-Eddington ratio relation, the EWMgII27_{\rm MgII} \sim 27 \AA\ measured for APM 08279+5255 translates into an Eddington ratio of \sim0.4, which is more consistent with μ=4\mu=4. This magnification factor also provides a value of MBHM_{\rm BH} that is consistent with recent reverberation-mapping measurements derived from C IV and Si IV.Comment: 10 pages, 4 figures, 4 tables, accepted for publication in A&

    NGC6240: extended CO structures and their association with shocked gas

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    We present deep CO observations of NGC6240 performed with the IRAM Plateau de Bure Interferometer (PdBI). NGC6240 is the prototypical example of a major galaxy merger in progress, caught at an early stage, with an extended, strongly-disturbed butterfly-like morphology and the presence of a heavily obscured active nucleus in the core of each progenitor galaxy. The CO line shows a skewed profile with very broad and asymmetric wings detected out to velocities of -600 km/s and +800 km/s with respect to the systemic velocity. The PdBI maps reveal the existence of two prominent structures of blueshifted CO emission. One extends eastward, i.e. approximately perpendicular to the line connecting the galactic nuclei, over scales of ~7 kpc and shows velocities up to -400 km/s. The other extends southwestward out to ~7 kpc from the nuclear region, and has a velocity of -100 km/s with respect to the systemic one. Interestingly, redshifted emission with velocities 400 to 800 km/s is detected around the two nuclei, extending in the east-west direction, and partly overlapping with the eastern blue-shifted structure, although tracing a more compact region of size ~1.7 kpc. The overlap between the southwestern CO blob and the dust lanes seen in HST images, which are interpreted as tidal tails, indicates that the molecular gas is deeply affected by galaxy interactions. The eastern blueshifted CO emission is co-spatial with an Halpha filament that is associated with strong H2 and soft X-ray emission. The analysis of Chandra X-ray data provides strong evidence for shocked gas at the position of the Halpha emission. Its association with outflowing molecular gas supports a scenario where the molecular gas is compressed into a shock wave that propagates eastward from the nuclei. If this is an outflow, the AGN are likely the driving force.Comment: Accepted for publication in A&

    The multi-phase winds of Markarian 231: from the hot, nuclear, ultra-fast wind to the galaxy-scale, molecular outflow

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    We present the best sensitivity and angular resolution maps of the molecular disk and outflow of Mrk 231, as traced by CO observations obtained with IRAM/PdBI, and we analyze archival Chandra and NuSTAR observations. We constrain the physical properties of both the molecular disk and outflow, the presence of a highly-ionized ultra-fast nuclear wind, and their connection. The molecular outflow has a size of ~1 kpc, and extends in all directions around the nucleus, being more prominent along the south-west to north-east direction, suggesting a wide-angle biconical geometry. The maximum projected velocity of the outflow is nearly constant out to ~1 kpc, thus implying that the density of the outflowing material decreases from the nucleus outwards as r2r^{-2}. This suggests that either a large part of the gas leaves the flow during its expansion or that the bulk of the outflow has not yet reached out to ~1 kpc, thus implying a limit on its age of ~1 Myr. We find M˙OF=[5001000] M yr1\dot M_{OF}=[ 500-1000]~ M_{\odot}~yr^{-1} and E˙kin,OF=[710]×1043\dot E_{kin,OF}=[7-10]\times 10^{43} erg s1^{-1}. Remarkably, our analysis of the X-ray data reveals a nuclear ultra-fast outflow (UFO) with velocity -20000 km s1^{-1}, M˙UFO=[0.32.1] Myr1\dot M_{UFO}=[0.3- 2.1] ~M_\odot yr^{-1}, and momentum load P˙UFO/P˙rad=[0.21.6]\dot P_{UFO}/\dot P_{rad}=[0.2-1.6].We find E˙kin,UFOE˙kin,OF\dot E_{kin,UFO}\sim \dot E_{kin,OF} as predicted for outflows undergoing an energy conserving expansion. This suggests that most of the UFO kinetic energy is transferred to mechanical energy of the kpc-scale outflow, strongly supporting that the energy released during accretion of matter onto super-massive black holes is the ultimate driver of giant massive outflows. We estimate a momentum boost P˙OF/P˙UFO[3060]\dot P_{OF}/\dot P_{UFO}\approx [30-60]. The ratios E˙kin,UFO/Lbol,AGN=[15]%\dot E_{kin, UFO}/L_{bol,AGN} =[ 1-5]\% and E˙kin,OF/Lbol,AGN=[13]%\dot E_{kin,OF}/L_{bol,AGN} = [1-3]\% agree with the requirements of the most popular models of AGN feedback.Comment: 16 pages, 17 figures. Accepted for publication in A&
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