Bibcode
Cisternas, M.; Gadotti, Dimitri A.; Knapen, J. H.; Kim, Taehyun; Díaz-García, Simón; Laurikainen, Eija; Salo, Heikki; González-Martín, O.; Ho, Luis C.; Elmegreen, Bruce G.; Zaritsky, Dennis; Sheth, Kartik; Athanassoula, E.; Bosma, Albert; Comerón, Sébastien; Erroz-Ferrer, S.; Gil de Paz, Armando; Hinz, Joannah L.; Holwerda, Benne W.; Laine, Jarkko; Meidt, Sharon; Menéndez-Delmestre, Karín; Mizusawa, Trisha; Muñoz-Mateos, Juan Carlos; Regan, Michael W.; Seibert, Mark
Bibliographical reference
The Astrophysical Journal, Volume 776, Issue 1, article id. 50, 15 pp. (2013).
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10
2013
Journal
Citations
51
Refereed citations
51
Description
Stellar bars can lead to gas inflow toward the center of a galaxy and
stimulate nuclear star formation. However, there is no compelling
evidence on whether they also feed a central supermassive black hole: by
measuring the fractions of barred active and inactive galaxies, previous
studies have yielded conflicting results. In this paper, we aim to
understand the lack of observational evidence for bar-driven active
galactic nucleus (AGN) activity by studying a sample of 41 nearby (d
< 35 Mpc) barred galaxies from the Spitzer Survey for Stellar
Structure in Galaxies. We use Chandra observations to measure nuclear
2-10 keV X-ray luminosities and estimate Eddington ratios, together with
Spitzer 3.6 μm imaging to quantify the strength of the stellar bar in
two independent ways: (1) from its structure, as traced by its
ellipticity and boxiness, and (2) from its gravitational torque
Qb , taken as the maximum ratio of the tangential force to
the mean background radial force. In this way, rather than discretizing
the presence of both stellar bars and nuclear activity, we are able to
account for the continuum of bar strengths and degrees of AGN activity.
We find nuclear X-ray sources in 31 out of 41 galaxies with median X-ray
luminosity and Eddington ratio of L X = 4.3 ×
1038 erg s–1 and L bol/L
Edd = 6.9 × 10–6, respectively,
consistent with low-luminosity AGN activity. Including upper limits for
those galaxies without nuclear detections, we find no significant
correlation between any of the bar strength indicators and the degree of
nuclear activity, irrespective of galaxy luminosity, stellar mass,
Hubble type, or bulge size. Strong bars do not favor brighter or more
efficient nuclear activity, implying that at least for the
low-luminosity regime, supermassive black hole fueling is not closely
connected to large-scale features.
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