ALMA Observations of the Molecular Gas in the Elliptical Galaxy NGC 3557
ALMA Observations of the Molecular Gas in the Elliptical Galaxy NGC 3557
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DOI：
10.3847/1538-4357/aaef7f
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发表时间：
2018-12
期刊：
影响因子：
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通讯作者：
B. Vila-Vilaro;D. Espada;P. Cortés;S. Léon;E. Pompei;J. Cepa
中科院分区：
文献类型：
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作者：
B. Vila-Vilaro;D. Espada;P. Cortés;S. Léon;E. Pompei;J. Cepa
我们展示了使用 ALMA 对南椭圆星系 NGC 3557 进行 CO 干涉观测的结果。我们检测到了 CO(1–0) 发射线和 3 mm 处相对较强的连续谱。连续谱显示了一个平谱中心未解析源（角分辨率为 0.''7）和两个喷流，与在较低频率下观察到的大规模发射相关。 NGC 3557 中的分子气体似乎集中在中心的 250 pc 范围内，并显示出沿着与恒星成分相同的轴和文献中报道的核尘埃吸收的对称轴有组织旋转的证据。我们获得了分子气体，其平均CO（2-1）与CO（1-0）线比为0.7，与文献中报道的用单口径望远镜观测到的真正椭圆形的值相比相对较高。 NGC 3557 还显示出一个距中心偏移 0.″7 的高激发峰（即 CO(2–1)/CO(1–0) ≈ 1.1 ± 0.3），这似乎与高速色散区域相关，该区域不共享分子气体的整体旋转模式，但与射电射流对齐。该物体中的分子气盘似乎对局部重力不稳定性是稳定的。
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 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.