Bibcode
Vila-Vilaro, B.; Espada, Daniel; Cortes, Paulo; Leon, Stephane; Pompei, Emanuela; Cepa, J.
Bibliographical reference
The Astrophysical Journal, Volume 870, Issue 1, article id. 39, 12 pp. (2019).
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2019
Journal
Citations
7
Refereed citations
7
Description
We present the results of CO interferometric observations of the
southern elliptical galaxy NGC 3557 with ALMA. We have detected both the
CO(1–0) emission line and a relatively strong continuum at 3 mm.
The continuum shows a flat-spectrum central unresolved source (at our
angular resolution of 0.″7) and two jets, associated with the
larger-scale emission observed at lower frequencies. The molecular gas
in NGC 3557 appears to be concentrated within 250 pc of the center, and
shows evidence of organized rotation along the same axis as the stellar
component and the symmetry axis of the nuclear dust absorption reported
in the literature. We obtained {M}{{{H}}2}=(9.0+/-
2.0)× {10}7 {M}ȯ of molecular gas,
which has an average CO(2–1) to CO(1–0) line ratio of 0.7,
which is relatively high when compared with the values reported in the
literature for bona fide ellipticals observed with single-dish
telescopes. NGC 3557 shows further a high excitation peak (i.e.,
CO(2–1)/CO(1–0) ≈ 1.1 ± 0.3) offset 0.″7
from the center, which appears to be associated with a region of higher
velocity dispersion that does not share the overall rotation pattern of
the molecular gas, but aligned with the radio jet. The molecular gas
disk in this object appears to be stable to local gravitational
instabilities.
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