Central Star Formation Activity Research Articles

Triggering optical AGN: the need for cold gas, and the indirect roles of galaxy environment and interactions

We present a study of the prevalence and luminosity of active galactic nuclei (AGN; traced by optical spectra) as a function of both environment and galaxy interactions. For this study, we used a sample of more than 250 000 galaxies drawn from the Sloan Digital Sky Survey and, crucially, we controlled for the effect of both stellar mass and central star formation activity. Once these two factors are taken into account, the effect of the local density of galaxies and of one-on-one interactions is minimal in both the prevalence of AGN activity and AGN luminosity. This suggests that the level of nuclear activity depends primarily on the availability of cold gas in the nuclear regions of galaxies and that secular processes can drive the AGN activity in the majority of cases. Large-scale environment and galaxy interactions only affect AGN activity in an indirect manner, by influencing the central gas supply.

More extragalactic carbon monoxide

view Abstract Citations (19) References (89) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS More extragalactic carbon monoxide. Rickard, L. J. ; Turner, B. E. ; Palmer, P. Abstract The authors have detected CO emission toward the centers of six spiral galaxies - NGC 660, 3504, 3628, 4303, 4631, and 4826 - which had been predicted to have molecular sources similar to that in the center of our own galaxy on the basis of OH and IR studies. Analysis of the entire sample of galaxies with strong central CO peaks supports the interpretation of the central peaks as components distinct from the disk molecular clouds. The authors suggest a new method for estimating the mass of associated H2 that emphasizes the different kinds of clouds in these different regions. There appears to be no correlation of CO and H I linewidths, However, there are good correlations between CO emission, far-infrared emission, and nonthermal radio continuum emission. The correlation with infrared emission shows that more molecular gas implies more star formation in galactic centers. The correlation with nonthermal emission suggests the need for a connection between central star-formation activity and the global structural properties of spiral galaxies. Publication: The Astronomical Journal Pub Date: July 1985 DOI: 10.1086/113823 Bibcode: 1985AJ.....90.1175R Keywords: Carbon Monoxide; Intergalactic Media; Interstellar Gas; Spiral Galaxies; Far Infrared Radiation; Galactic Nuclei; Hydrogen; Molecular Clouds; Nonthermal Radiation; Radio Emission; Astrophysics full text sources ADS | data products SIMBAD (6) NED (6)