Time variations of the neutral hydrogen absorption spectrum of NGC 1275 (3C 84)

Journal Article · Mon Nov 01 04:00:00 EST 1982 · Astrophys. J.; (United States)

DOI:https://doi.org/10.1086/160398· OSTI ID:6371073

Haschick, A D; Crane, P C; Hulst, J M.V.D.

The neutral hydrogen absorption spectrum and total radio continuum flux density of NGC 1275 (3C 84) have been monitored for temporal changes over a 6-year period. The strengths of two (at 8114 and 8120 km s/sup -1/) of the three dominant features in the spectrum have increased as the total flux density of NGC 1275 increased, although not by the same proportion. The third feature at 8106 km s/sup -1/ has not varied. Assuming a constant optical depth, we can calculate the flux density of the variable component which is being absorbed by the hydrogen at 8114 and 8120 km s/sup -1/. We find a flux density of 4.1 +- 0.6 Jy for epoch 1974.4, in reasonable agreement with VLBI results for the very compact component of the radio source in NGC 1275. The hydrogen at 8106 km s/sup -1/ must be absorbing another, more extended component of the radio source that does not vary. High-resolution spectral-line observations with the Very Large Array (VLA) indicate that >92% of the absorption at 8106 km s/sup -1/ occurs in a region <1'' in size. This implies that the hydrogen at 8106 km s/sup -1/ absorbs radio continuum with a scale size between 0--01 and 1--0. This result is in agreement with findings by Romney.

• Research Organization: Research Laboratory of Electronics and Haystack Observatory, Massachusetts Institute of Technology, and Harvard-Smithsonian Center for Astrophysics
• OSTI ID: 6371073
• Journal Information: Astrophys. J.; (United States), Journal Name: Astrophys. J.; (United States) Vol. 262:1; ISSN ASJOA
• Country of Publication: United States
• Language: English

Related Subjects

640105* -- Astrophysics &amp; Cosmology-- Galaxies
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ABSORPTION SPECTRA
COSMIC RADIO SOURCES
ELECTROMAGNETIC RADIATION
FLUX DENSITY
GALAXIES
GALAXY NUCLEI
H1 REGIONS
RADIATION FLUX
RADIATIONS
RADIOWAVE RADIATION
SEYFERT GALAXIES
SPECTRA
VARIATIONS