1,685 research outputs found
Obscured Binary Quasar Cores in SDSS J104807.74+005543.5?
We report the discovery of a possible close binary system of quasars in SDSS
J1048+0055. The [OIII]4959,5007 emission lines are clearly double-peaked, and
two discrete radio sources with a projected physical separation of ~20 pc are
found in the VLBA milliarcsec resolution image at 8.4 GHz. Each of the [O
III]4959,5007 doublets and Hbeta can be well modelled by two Gaussians and the
line ratio, [O III]5007/Hbeta ~7, is typical of Seyfert 2 galaxies. No broad
component of Hbeta was detected and its [O III]5007 luminosity, L_[OIII] ~ 9.2
times 10^42 erg s^-1, is comparable to luminous quasars and is a few ten times
more luminous than typical Seyfert galaxies. One natural interpretation is that
SDSS J1048+0055 contains two close quasar-like nuclei and the BLR around them
are obscured. Other possible models are also discussed. We suggest that
double-peaked narrow emission line profile may be an effective way of selecting
candidates of binary black holes with intermediate separation
Effectiveness of variable-width buffer design for sediment reduction
Vegetative buffer strips are vegetated areas (usually strips) between fields and waterbodies that can mitigate the effects of agricultural activities by acting as a physical barrier to sediment and nutrients being carried to streams, and thereby have been widely used as a best management practice (BMP). Buffers can slow surface water flow and allow greater water infiltration, trapping the sediment entering from cultivated areas. In addition, research has documented the ability of buffers to removing pollutants from surface runoff and/or shallow groundwater (Lin et al., 2007; Ryder and Fares, 2008). For example, nitrogen can be removed by plant uptake or by microorganism denitrification within buffers (Lowrance and Hubbard, 2001)
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