Disentangling the Circumnuclear Environs of Centaurus A. II. On the Nature of the Broad Absorption Line
Journal article, 2010
We report on atomic gas (H I) and molecular gas (as traced by CO(2-1)) redshifted absorption features toward the nuclear regions of the closest powerful radio galaxy, Centaurus A (NGC 5128). Our H I observations using the Very Long Baseline Array allow us to discern with unprecedented sub-parsec resolution H I absorption profiles toward different positions along the 21 cm continuum jet in the inner 0farcs3 (or 5.4 pc). In addition, our CO(2-1) data obtained with the Submillimeter Array probe the bulk of the absorbing molecular gas with little contamination by emission, which was not possible with previous CO single-dish observations. We shed light on the physical properties of the gas in the line of sight with these data, emphasizing the still open debate about the nature of the gas that produces the broad absorption line (~55 km s–1). First, the broad H I line is more prominent toward the central and brightest 21 cm continuum component than toward a region along the jet at a distance ~20 mas (or 0.4 pc) further from the nucleus. This indicates that the broad absorption line arises from gas located close to the nucleus, rather than from diffuse and more distant gas. Second, the different velocity components detected in the CO(2-1) absorption spectrum match well with other molecular lines, such as those of HCO+(1-0), except the broad absorption line that is detected in HCO+(1-0) (and most likely related to that of the H I). Dissociation of molecular hydrogen due to the active galactic nucleus seems to be efficient at distances r lsim 10 pc, which might contribute to the depth of the broad H I and molecular lines.
galaxies: structure
galaxies: ISM
cD
quasars: absorption lines
galaxies: elliptical and lenticular
galaxies: individual (NGC 5128)
Author
D. Espada
Harvard-Smithsonian Center for Astrophysics
Institute of Astrophysics of Andalusia (IAA)
Academia Sinica
A. B. Peck
Harvard-Smithsonian Center for Astrophysics
National Radio Astronomy Observatory Socorro
Atacama Large Millimeter-submillimeter Array (ALMA)
S. Matsushita
Atacama Large Millimeter-submillimeter Array (ALMA)
Academia Sinica
K. Sakamoto
Academia Sinica
C. Henkel
Max Planck Society
D. Iono
National Astronomical Observatory of Japan
F. P. Israel
Leiden University
Sebastien Muller
Chalmers, Earth and Space Sciences, Onsala Space Observatory
G. Petitpas
Harvard-Smithsonian Center for Astrophysics
Y. Pihlstrom
University of New Mexico
National Radio Astronomy Observatory Socorro
G. Taylor
University of New Mexico
National Radio Astronomy Observatory Socorro
D.-V. Trung
Vietnam Academy of Science and Technology
Academia Sinica
Astrophysical Journal
0004-637X (ISSN) 1538-4357 (eISSN)
Vol. 720 1 666-678Subject Categories
Astronomy, Astrophysics and Cosmology
Roots
Basic sciences
DOI
10.1088/0004-637X/720/1/666