EXAMINING THE RADIO-LOUD/RADIO-QUIET DICHOTOMY WITH NEW CHANDRA AND VLA OBSERVATIONS OF 13 UGC GALAXIES

Journal Article · Sun Apr 15 04:00:00 EDT 2012 · Astronomical Journal (New York, N.Y. Online)

DOI:https://doi.org/10.1088/0004-6256/143/4/78· OSTI ID:22034677

Kharb, P; Axon, D J; Robinson, A ^[1]; Capetti, A; Balmaverde, B ^[2]; Chiaberge, M; Macchetto, D ^[3]; Grandi, P ^[4]; Giovannini, G ^[5]; Montez, R ^[6]

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1. Physics Department, Rochester Institute of Technology, Rochester, NY 14623 (United States)
2. INAF, Osservatorio Astronomico di Torino, Strada Osservatorio 20, 10025 Pino Torinese (Italy)
3. Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States)
4. INAF, Istituto di Astrofisica Spaziale e Fisica Cosmica, Bologna (Italy)
5. INAF, Istituto di Radioastronomia di Bologna, via Gobetti 101, 40129 Bologna (Italy)
6. Center for Imaging Science, Rochester Institute of Technology, Rochester, NY 14623 (United States)

We present the results from new {approx}15 ks Chandra-ACIS and 4.9 GHz Very Large Array (VLA) observations of 13 galaxies hosting low-luminosity active galactic nuclei (AGNs). This completes the multiwavelength study of a sample of 51 nearby early-type galaxies described in Capetti and Balmaverde and Balmaverde and Capetti. The aim of the three previous papers was to explore the connection between the host galaxies and AGN activity in a radio-selected sample. We detect nuclear X-ray emission in eight sources and radio emission in all but one (viz., UGC 6985). The new VLA observations improve the spatial resolution by a factor of 10: the presence of nuclear radio sources in 12 of the 13 galaxies confirms their AGN nature. As previously indicated, the behavior of the X-ray and radio emission in these sources depends strongly on the form of their optical surface brightness profiles derived from Hubble Space Telescope imaging, i.e., on their classification as 'core', 'power-law', or 'intermediate' galaxies. With more than twice the number of 'power-law' and 'intermediate' galaxies compared to previous work, we confirm with a much higher statistical significance that these galaxies lie well above the radio-X-ray correlation established in Fanaroff-Riley type I radio galaxies and the low-luminosity 'core' galaxies. This result highlights the fact that the 'radio-loud/radio-quiet' dichotomy is a function of the host galaxy's optical surface brightness profile. We present radio-optical-X-ray spectral indices for all 51 sample galaxies. Survival statistics point to significant differences in the radio-to-optical and radio-to-X-ray spectral indices between the 'core' and 'power-law galaxies (Gehan's Generalized Wilcoxon test probability p for the two classes being statistically similar is <10{sup -5}), but not in the optical-to-X-ray spectral indices (p = 0.25). Therefore, the primary difference between the 'core' and 'power-law' galaxies is in their ability to launch powerful radio outflows. This result is consistent with the hypothesis of different formation processes and evolution histories in 'core' and 'power-law' galaxies: major mergers are likely to have created 'core' galaxies, while minor mergers were instrumental in the creation of 'power-law' galaxies.

• OSTI ID: 22034677
• Journal Information: Astronomical Journal (New York, N.Y. Online), Journal Name: Astronomical Journal (New York, N.Y. Online) Journal Issue: 4 Vol. 143; ISSN 1538-3881
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
ASTRONOMY
ASTROPHYSICS
BRIGHTNESS
CLASSIFICATION
CORRELATIONS
GALACTIC EVOLUTION
GALAXY NUCLEI
GHZ RANGE
INDEXES
LUMINOSITY
PHOTON EMISSION
RADIO GALAXIES
SPATIAL RESOLUTION
STATISTICS
X RADIATION
X-RAY GALAXIES