Evidence of a double – double morphology in B 0818 + 214
نویسندگان
چکیده
The so-called double–double structure in radio sources is the most conspicuous signature of their restarted activity. Observations indicate that in the majority of double–double radio sources (DDRS), the span of the radio lobes is larger than 0.7 Mpc. This lower limit is also suggested by theory. However, it seemed likely that the apparent core of B 0818+214, a radio galaxy with an overall linear size of its radio structure below that limit, could harbour a compact double well aligned with the outer lobes so that the whole object would fulfil the criteria of a DDRS. Here, we present evidence that the central component of B 0818+214, when magnified through the EVN+MERLIN 18-cm observations shows two FR II-like lobes. As the separation of the inner lobes is not greater than 5.7 kpc, they are immersed in the ISM of the host galaxy. This circumstance is the likely reason why the inner double has become visible, despite the predictions of the theory according to which B 0818+214 as a whole is too small for a new double to develop inside the cocoon inflated during the previous active phase. Moreover, we speculate that its host galaxy is not active at the moment and so the inner double may be in the coasting phase often observed in other medium-sized symmetric objects with intermittent activity. It could be, therefore, that two different mechanisms of accretion disk instabilities, ionisation and radiation-pressure driven, may be independently responsible for triggering active phases, manifesting as the outer and the inner doubles, respectively.
منابع مشابه
Investigating Tribological Characteristics of Ni-P and Double–Layered Ni-P/Ni-B Electroless Coatings Applied to the Carbon Mild Steel Ck45
In this research, tribological characteristics of Ni-P electroless coating and double-layered Ni-P/Ni-B electroless coating were studied. For this purpose, Ni-P electroless coating with 25 μm thickness was initially applied to the surface of steel Ck45 samples; then, a double-layered Ni-P/Ni-B electroless coating, including inner layer of Ni-P with 15 μm thickness and outer layer of Ni-B with 1...
متن کاملFully Fresh Air Air-conditioning System Equipped with Double Heat Pipe Based Heat Recovery Technology
The using of double heat pipe based heat exchanger (HPHX) in a conventional fully fresh air air-conditioning (AC) system was examined in the present study. The fabricated HPHXs were tested under the actual conditions and the measured data were used to study the performance of the existing AC system (System A) and AC system equipped with the double HPHX (System B) for a yearly operation through ...
متن کاملSunflower morphology and yield as affected by foliar applications of plant growth regulators
Plant height of sunflower is a major agronomic trait affecting crop performance in the field and its adaptation to mechanical harvest. Field experiments were conducted to study the effect of foliar application of paclobutrazol (PBZ) at 12.5 g ai/ha, mepiquat chloride (MPC) at 25.0 g ai/ha and chlormequat chloride (CCC) at 1,500 g ai/ha in single or double applications on sunflower plant mor...
متن کاملEvidence of the Potential Shift Mechanism in Crevice Corrosion (RESEARCH NOTES)
Previous research has indicated a qualitative resemblance between the current distribution along actively corroding crevice walls and currents measured in corresponding anodic polarization plots. Using detailed measurements of the potential gradient along the crevice, a semi-quantitative current distribution was calculated for the crevice wall using a double numerical differentiation method. Th...
متن کاملذخیره در منابع من
با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید
عنوان ژورنال:
دوره شماره
صفحات -
تاریخ انتشار 2009