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Register a new userProperties of the Obscuring Torus in NGC 1052 from Multi-epoch Broadband X-ray Spectroscopy
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Added by
Mislav Balokovi\\'c
Publication date
2021
fields
Physics
and research's language is
English
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Obscuration of the innermost parts of active galactic nuclei (AGN) is observed in the majority of the population both in the nearby universe and at high redshift. However, the nature of the structures causing obscuration, especially in low-luminosity AGN, is poorly understood at present. We present a novel approach to multi-epoch broadband X-ray spectroscopy, anchored in the long-term average spectrum in the hard X-ray band, applied to the nearby, X-ray bright AGN in the galaxy NGC 1052. From spectral features due to X-ray reprocessing in the circumnuclear material, based on a simple, uniform-density torus X-ray reprocessing model, we find a covering factor of 80-100% and a globally averaged column density in the range (1-2) x 10^23 cm^-2. This closely matches the independently measured variable line-of-sight column density range, leading to a straightforward and self-consistent picture of the obscuring torus in NGC 1052, similar to several other AGN in recent literature. Comparing this X-ray-constrained torus model with measurements of spatially resolved sub-parsec absorption from radio observations, we find that it may be possible to account for both X-ray and radio data with a torus model featuring a steep density gradient along the axis of the relativistic jets. This provides a valuable direction for the development of improved physical models for the circumnuclear environment in NGC 1052 and potentially in a wider class of AGN.
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We present multi-frequency simultaneous VLBA observations at 15, 22 and 43 GHz towards the nucleus of the nearby radio galaxy NGC 1052. These three continuum images reveal a double-sided jet structure, whose relative intensity ratios imply that the jet axis is oriented close to the sky plane. The steeply rising spectra at 15-43 GHz at the inner edges of the jets strongly suggest that synchrotron emission is absorbed by foreground thermal plasma. We detected H_2O maser emission in the velocity range of 1550-1850 km/s, which is redshifted by 50-350 km/s with respect to the systemic velocity of NGC 1052. The redshifted maser gas appears projected against both sides of the jet, similar to the HI seen in absorption. The H_2O maser gas is located where the free-free absorption opacity is large. This probably implies that the masers in NGC 1052 are associated with a circumnuclear torus or disk as in the nucleus of NGC 4258. Such circumnuclear structure can be the sense of accreting onto the central engine.
We present multi-frequency simultaneous VLBA observations at 15, 22 and 43 GHz towards the nucleus of the nearby radio galaxy NGC 1052. These three continuum images reveal a double-sided jet structure, whose relative intensity ratios imply that the jet axis is oriented close to the sky plane. The steeply rising spectra at 15-43 GHz at the inner edges of the jets strongly suggest that synchrotron emission is absorbed by foreground thermal plasma. We detected H2O maser emission in the velocity range of 1550-1850 km/s, which is redshifted by 50-350 km/s with respect to the systemic velocity of NGC 1052. The redshifted maser gas appears projected against both sides of the jet, in the same manner as the HI seen in absorption. The H2O maser gas are located where the free-free absorption opacity is large. This probably imply that the masers in NGC 1052 are associated with a circumnuclear torus or disk as in the nucleus of NGC 4258. Such circumnuclear structure can be the sence of accreting onto the central engine.
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