Starburst Nucleus Galaxies Research Articles

Gradients of excitation in the nuclei of starburst galaxies

This article forms a part of a wider study of the nuclear and circum-nuclear zones of moderately active galaxies. The use of long-slit spectroscopy at high spectral and spatial resolution has enabled us to measure gradients of gaseous excitation and also velocity fields in a sample of four bright nuclear starburst galaxies selected from the sample of Balzano (1983). We find variations not only in the intensity but also in the ‘quality’ of the emission spectra (line ratios and line widths) of the interstellar gas between regions separated by relatively short distances. We stress the need for studies with at least the present degree of angular and spectral resolution if physical sense is to be made of the interstellar excitation regimes in external galaxies, as well as to investigate a possible evolutionary link between nuclei of intermediate activity.

The Interstellar Medium in Star Burst Galaxies

We report far-infrared observations of [0 I], [C II] and [O III] fine structure emission lines toward the nuclei of M82 and 7 other galaxies with a high rate of star formation. The far-infrared line emission is bright, contains about 0.5% of the bolometric luminosity in the central 60″, and is spatially concentrated toward the nuclei. In these galaxies between 10 and 30% of the interstellar gas near the nuclei is contained in a warm, atomic component. This atomic gas is probably located at the UV photodissociated surfaces of molecular clouds. The neutral gas in M82 has a temperature of ∼ 200 K, hydrogen density of ∼ 3 × 104 cm−3 and is very clumpy, indicating that the interstellar medium in this star burst galaxy is very different from that in the disk of our own galaxy. We discuss the implications of the infrared observations for the interpretation of mm molecular lines and for star formation at the nuclei of star burst galaxies.

Molecular gas in the type 1 Seyfert galaxy NGC 7469 Implications for nuclear activity

view Abstract Citations (64) References (62) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Molecular Gas in the Type 1 Seyfert Galaxy NGC 7469: Implications for Nuclear Activity Heckman, T. M. ; Beckwith, S. ; Blitz, L. ; Skrutskie, M. ; Wilson, A. S. Abstract The results of a search for 2.12-micron H2 1-0 S(1) line emission from the nuclear (not greater than 1 kpc) region in 11 active galaxies are reported. The galaxies observed included type 1 and type 2 Seyferts, LINERs, and starburst nucleus galaxies. H2 emission was detected in one galaxy, the classical type 1 Seyfert NGC 7469. Also reported is the detection of very luminous C-12O 2.6-mm emission from NGC 7469, and optical narrow-band images and long-slit spectroscopy data concerning the ionized gas in this galaxy are presented. These data imply that NGC 7469 not only contains a highly active compact nucleus but also is undergoing a luminous circumnuclear (few-kpc scale) starburst. Most of the other galaxies with known H2 emission also seem to be composite 'monster'/starburst systems and/or interacting galaxies. This result may arise because the molecular gas is associated with the starburst, while the primary form of the mechanical energy necessary to shock-excite the H2 is either outflow (possibly a wind) driven by the compact active nucleus or noncircular motions of gravitational origin. In either case, high-velocity (greater than 300 km/s) collisions between dense molecular clouds and a more ubiquitous, less dense gas phase can drive slow (10-30 km/s) shocks into the molecular clouds, exciting the observed H2 emission. Publication: The Astrophysical Journal Pub Date: June 1986 DOI: 10.1086/164236 Bibcode: 1986ApJ...305..157H Keywords: Astronomical Spectroscopy; Galactic Nuclei; Infrared Spectra; Molecular Gases; Seyfert Galaxies; Active Galaxies; Carbon Monoxide; Emission Spectra; Gas Density; Hydrogen; Interacting Galaxies; Line Spectra; Molecular Clouds; Starburst Galaxies; Astrophysics; GALAXIES: INDIVIDUAL NGC NUMBER: NGC 7469; GALAXIES: NUCLEI; GALAXIES: SEYFERT; INTERSTELLAR: MOLECULES full text sources ADS | data products SIMBAD (19) NED (16)