SIMBAD references

2002MNRAS.335.1091B - Mon. Not. R. Astron. Soc., 335, 1091-1099 (2002/October-1)

Sub-arcsecond atomic hydrogen absorption in the Seyfert galaxies NGC 7674 and NGC 7469.


Abstract (from CDS):

Neutral hydrogen has been studied on sub-arcsecond scales in two Seyfert galaxies, NGC 7469 and NGC 7674. The 1.4-GHz continuum emission from these sources agree with higher frequency measurements and shows linear, triple source in NGC 7674 and a compact source surrounded by a weak ring of radio emission in NGC 7469. In both of these sources we detect deep localized H i absorption in front of a single continuum component.

In the case of NGC 7674 the H i absorption is only seen against the central component and has a peak optical depth of 0.21±0.03, a linewidth of 114±7 km.s–1 and a heliocentric velocity of 8623±5 km.s–1. The integrated H i absorption against the central component corresponds to a column density of 5.0±0.7 x1021 atom cm –2. We interpret the lack of H i absorption against the east and west components ( τ < 0.07 and 0.06) as evidence that the H i is localized within the central few hundred pc, similar to the H i observed against the nucleus of NGC 4151, and has an upper mass limit of ∼4x105 M. We speculate that this H i may be associated with a dusty torus. Giant Meterwavelength Radio Telescope (GMRT) results show extended emission and give a rest velocity of 8699±20 km.s–1.

The H i absorption against NGC 7469 shows a single deep feature against the strong central component. The line has a peak optical depth 0.25, a linewidth of 65±6 km.s–1 and a heliocentric velocity of 4843±5 km.s–1. The integrated column density is 3.6±0.4x1021 atom cm –2. Unfortunately the other components in NGC 7469 are too weak to set significant limits to the H i optical depth, and hence, unlike NGC 7674, it is not possible to constrain the size of the absorbing gas.

Abstract Copyright: RAS

Journal keyword(s): galaxies: active - galaxies: individual: NGC 7469 - galaxies: individual: NGC 7674 - galaxies: Seyfert - radio lines: galaxies

Nomenclature: Fig.4, Table 2: [BPM2002] NGC 7469 A (Nos A-C), [BPM2002] NGC 7469 nucleus N=1.

CDS comments: Table 1: radio components of NGC 7674 = [UPA88] NGC 7674 C, E, W. p.1098: PKS 1545-79 is a misprint for PKS 1549-79

Simbad objects: 21

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