VLA Images Research Articles

Current star formation as the origin of kiloparsec-scale radio sources in nearby E/S0 galaxies

view Abstract Citations (77) References (39) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Current Star Formation as the Origin of Kiloparsec-Scale Radio Sources in Nearby E/S0 Galaxies Wrobel, J. M. ; Heeschen, D. S. Abstract VLA images at 6 cm of eight nearby galaxies show extended emission on kpc scales. Existing optical data reveal that six of the host galaxies are likely to be genuine ellipticals or lenticulars, and two are possibly ellipticals or lenticulars. All eight galaxies have diffuse or linear radio morphologies, and modest powers P_6 cm_ ~ 10^20-21^ W Hz^-1^. One galaxy, a Seyfert 1 and the most powerful in the radio, has a jet-like structure adjacent to a compact core. In five other galaxies the kpc-scale radio sources are associated either with known star-forming regions, or with regions that can reasonably be expected to be star-formation sites. Supernova remnants produced at rates of less than or the order of 1 per year could account for the observed powers. All eight galaxies have substantial far-infrared luminosities, L_FIR_. All except the Seyfert galaxy conform to the P_6 cm_ versus L_FIR_ relation of Wunderlich et al. defined mainly by galaxies known to be forming stars. Six galaxies are known to be H I rich, possibly due to gas capture during a recent encounter with a gas-rich companion galaxy (Knapp et al.). One or more gas-rich companions are identified for each of seven galaxies. If the captured gas also includes a cold molecular component which is able to settle to the nuclear region, then it could fuel current star formation on kpc scales. Publication: The Astrophysical Journal Pub Date: December 1988 DOI: 10.1086/166958 Bibcode: 1988ApJ...335..677W Keywords: Extragalactic Radio Sources; Galactic Structure; Infrared Sources (Astronomy); Star Formation; Very Large Array (Vla); Far Infrared Radiation; Seyfert Galaxies; Supernova Remnants; Astrophysics; GALAXIES: STELLAR CONTENT; GALAXIES: STRUCTURE; INFRARED: SOURCES; RADIO SOURCES: GALAXIES; STARS: FORMATION full text sources ADS | data products NED (21) SIMBAD (20)

High Dynamic Range VLBI Observations of the 3C120 Radio Jet

3C 120 is a nearby radio galaxy (z = 0.033) that shows superluminal motions in its radio jet within one parsec of the nucleus. The apparent velocities of the moving features are approximately 1.5 mas/yr. This object is of particular interest because it is clearly identified with an N-type galaxy, unlike all other superluminal radio sources which are only seen in quasars and BL Lac objects. Because of the close proximity of 3C 120, we have been able to make a series of VLBI and VLA images at stepped resolutions, and thereby map the radio jet continuously from the radio nucleus (0.5 h−1 parsec) into the diffuse 400 h−1 kpc structure.

The linear filaments of the radio arc near the Galactic center

High-resolution radio continuum VLA images of a segment of the Galactic center arc centered at G0.16-0.15 at wavelengths of both 6 and 20 cm are presented. In this segment, the highest multiplicity of filaments, the largest degree of linear polarization, and a maximum rotation measure of -5500 rad/sq m between wavelengths 6.166 and 6.363 cm are found. The large 'helical segments' which surround the filamentary system are also shown and discussed. Based on a number of intriguing characteristics of the filamentary system, including the helical component and possible twisting of some of the filaments, a picture is considered in which the geometry of the magnetic structure is that of a cylindrically symmetric, force-free field anchored to the halo of the Galaxy. An analogy with solar flare filaments is used to discuss some aspects of the Galactic center filaments.

Radio images of the bipolar H II region S106

The authors report evidence for the presence of a circumstellar disk surrounding the exciting star of the bipolar H II region S106. The presence of this disk is inferred from the diminished column density of ionized gas in a roughly 3arcmin×20arcsec strip centered on the nebula in high-resolution VLA images. This feature suggests the presence of a circumstellar disk with a mass of ≡0.01 M_sun; and a mean thickness of 10<SUP>16</SUP> cm that is seen nearly edge-on. The optically obscured exciting star of the H II region, S106 IR, lies at the center of the shadowed area. The radio emission from the star is unresolved in the data. Its radio and infrared properties indicate that it is probably a B0 star possessing a massive stellar wind with a mass loss rate of ≡10<SUP>-6</SUP> M_sun; yr<SUP>-1</SUP> and a velocity of ≡100 km s<SUP>-1</SUP>.