Far-infrared observations of a luminous dust-shrouded source in the nucleus of NGC 4945

Journal Article · Wed Jun 01 00:00:00 EDT 1988 · Astrophys. J.; (United States)

DOI:https://doi.org/10.1086/166370· OSTI ID:7137711

Brock, D; Joy, M; Lester, D F; Harvey, P M; Ellis, Jr, H B

High-resolution far-infrared observations of the galaxy NGC 4945 have been obtained from the Kuiper Airborne Observatory. Using new observational techniques and nonlinear deconvolution routines, it is found that virtually all of the far-infrared luminosity originates from a nuclear source no larger than 12 arcsec x 9 arcsec (225 pc x 170 pc) in extent. This size constraint, coupled with the far-infrared dust temperature, indicates that the source is deeply embedded in dust: the lower limit for the 100 micron optical depth is 0.35, which is by far the largest yet measured in an external galaxy. Published optical spectra of NGC 4945 reveal a heavily obscured nonthermal source which exhibits broad line profiles typical of a Seyfert 2 active nucleus; it is concluded that the far-infrared emission is probably due to thermal radiation from dust grains surrounding the nonthermal nuclear source. A compact cluster of massive young stars may also contribute to the infrared luminosity, but the evidence for such star-forming activity is weak. 26 references.

• Research Organization: McDonald Observatory, Austin, TX (USA)
• OSTI ID: 7137711
• Journal Information: Astrophys. J.; (United States), Vol. 329
• Country of Publication: United States
• Language: English

Related Subjects

71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
GALAXY NUCLEI
FAR INFRARED RADIATION
COSMIC DUST
LUMINOSITY
SPIRAL CONFIGURATION
STAR CLUSTERS
STAR EVOLUTION
VISIBLE SPECTRA
CONFIGURATION
DUSTS
ELECTROMAGNETIC RADIATION
INFRARED RADIATION
OPTICAL PROPERTIES
PHYSICAL PROPERTIES
RADIATIONS
SPECTRA
640105* - Astrophysics & Cosmology- Galaxies