Astronomy and Astrophysics – Astrophysics
Scientific paper
2002-08-26
Astrophys.J. 581 (2002) 925-931
Astronomy and Astrophysics
Astrophysics
To appear in ApJ. 7 pages
Scientific paper
10.1086/344442
(Abridged) We have searched for nuclear radio emission from a statistically complete sample of 40 Sc galaxies within 30 Mpc that are optically classified as star-forming objects, in order to determine whether weak AGNs might be present. Only three nuclear radio sources were detected, in NGC 864, NGC 4123, and NGC 4535. These galaxies have peak 6-cm radio powers of 10^{20} W/Hz at arcsecond resolution, while upper limits of the non-detected galaxies typically range from 10^{18.4} to 10^{20} W/Hz. The three nuclear radio sources all are resolved and appear to have diffuse morphologies, with linear sizes of ~300 pc. This strongly indicates that circumnuclear star formation has been detected in these three H II galaxies. Comparison with previous 20-cm VLA results for the detected galaxies shows that the extended nuclear radio emission has a flat spectrum in two objects, and almost certainly is generated by thermal emission from gas ionized by young stars in the centers of those galaxies. The 6-cm radio powers are comparable to predictions for thermal emission that are based on the nuclear H-alpha luminosities, and imply nuclear star formation rates of 0.08-0.8 solar masses/yr, while the low-resolution NRAO VLA Sky Survey implies galaxy-wide star formation rates of 0.3-1.0 solar masses/yr in stars above 5 solar masses. Although the presence of active nuclei powered by massive black holes cannot be definitively ruled out, the present results suggest that they are likely to be rare in these late-type galaxies with H II spectra.
Ho Luis C.
Ulvestad James S.
No associations
LandOfFree
A Search for Active Galactic Nuclei in Sc Galaxies with H II Spectra does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with A Search for Active Galactic Nuclei in Sc Galaxies with H II Spectra, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and A Search for Active Galactic Nuclei in Sc Galaxies with H II Spectra will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-649294