ALMA Observations of the Molecular Gas in the Elliptical Galaxy NGC3557. (arXiv:1812.05385v1 [astro-ph.GA])
<a href="http://arxiv.org/find/astro-ph/1/au:+Vila_Vilaro_B/0/1/0/all/0/1">B. Vila-Vilaro</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Espada_D/0/1/0/all/0/1">D. Espada</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Cortes_P/0/1/0/all/0/1">P. Cortes</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Leon_S/0/1/0/all/0/1">S. Leon</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Pompei_E/0/1/0/all/0/1">E. Pompei</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Cepa_J/0/1/0/all/0/1">J. Cepa</a>
We present the results of CO interferometric observations of the southern
elliptical galaxy NGC3557 with ALMA. We have detected both the CO(1-0) emission
line and a relatively strong continuum at 3mm. The continuum shows a
flat-spectrum central unresolved source (at our angular resolution of
0.7arcsec) and two jets, associated with the larger scale emission observed at
lower frequencies. The molecular gas in NGC3557 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$pm$2.0)x10$^7$ M$_odot$ 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. NGC3557 shows further a high excitation peak
(i.e., CO(2-1)/CO(1-0) ~ 1.1$pm$0.3 offset 0.7 arcsec from the center, which
appears to be associated with a region of higher velocity dispersion that does
not share the overall rotation pattern of the molecular gas, but aligned with
the radio jet. The molecular gas disk in this object appears to be stable to
local gravitational instabilities.
We present the results of CO interferometric observations of the southern
elliptical galaxy NGC3557 with ALMA. We have detected both the CO(1-0) emission
line and a relatively strong continuum at 3mm. The continuum shows a
flat-spectrum central unresolved source (at our angular resolution of
0.7arcsec) and two jets, associated with the larger scale emission observed at
lower frequencies. The molecular gas in NGC3557 appears to be concentrated
within 250 pc of the center, and shows evidence of organized rotation along the
same axis as the stellar component and the symmetry axis of the nuclear dust
absorption reported in the literature. We obtained
M$_{H_2}$=(9.0$pm$2.0)x10$^7$ M$_odot$ 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. NGC3557 shows further a high excitation peak
(i.e., CO(2-1)/CO(1-0) ~ 1.1$pm$0.3 offset 0.7 arcsec 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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