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arXiv 1612.04401astro-ph.GA
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ULIRG IRAS 13120-5453中的稠密分子气体和核活度

The Dense Molecular Gas and Nuclear Activity in the ULIRG IRAS 13120-5453

G. C. Privon, S. Aalto, N. Falstad, S. Muller, E. González-Alfonso, K. Sliwa, E. Treister, F. Costagliola, L. Armus, A. S. Evans, S. Garcia-Burillo, T. Izumi, K… 展开作者

G. C. Privon, S. Aalto, N. Falstad, S. Muller, E. González-Alfonso, K. Sliwa, E. Treister, F. Costagliola, L. Armus, A. S. Evans, S. Garcia-Burillo, T. Izumi, K. Sakamoto, P. van der Werf, J. K. Chu

摘要:

我们提出了新的ALMA波段7($\sim340$ GHz)的致密气体示踪剂HCN,HCO $^+$,和CS的本地,单核,超亮红外星系IRAS 13120-5453的观测。我们发现相对于HCO $^+$(4 - 3),HCN(4 - 3)的发射集中增强,但没有发现HCN的辐射泵浦的证据。考虑到星暴的大小(0.5千秒差距)和估计的$\sim1.2$年$^{-1}$的超新星速率,高HCN/HCO $^+$比率可以解释为超新星的机械加热导致HCN丰度增加,尽管活动星系核和风也可能贡献额外的机械加热。星爆的大小意味着一个高的$Σ_{IR}$,为$4.7\times10^{12}$ $L_{\odot}$千秒差距$^{-2}$,略低于辐射压限制星爆的预测。HCN的线轮廓有低级别的翅膀,我们初步解释为外流致密分子气体的证据。然而,在HCN线翼中看到的密集分子流出不太可能逃离星系,并且注定要返回到核心并为未来的恒星形成提供燃料。我们还提出了H-$_2$ O线的赫歇尔观测模型,并发现了$\sim40$ K的核尘埃温度。IRAS 13120-5453的尘埃温度和$Σ_{IR}$比被称为“致密暗核”的系统(如Arp 220和Mrk 231)的尘埃温度和$Σ_{IR}$低。如果IRAS 13120-5453经历了一个致密的暗核阶段,我们很可能在反馈已经膨胀了核ISM并稀释了星暴/活动星系核核心中的恒星形成的时候看到它。

英文摘要:

We present new ALMA Band 7 ($\sim340$ GHz) observations of the dense gas tracers HCN, HCO$^+$, and CS in the local, single-nucleus, ultraluminous infrared galaxy IRAS 13120-5453. We find centrally enhanced HCN (4-3) emission, relative to HCO$^+$ (4-3), but do not find evidence for radiative pumping of HCN. Considering the size of the starburst (0.5 kpc) and the estimated supernovae rate of $\sim1.2$ yr$^{-1}$, the high HCN/HCO$^+$ ratio can be explained by an enhanced HCN abundance as a result of mechanical heating by the supernovae, though the active galactic nucleus and winds may also contribute additional mechanical heating. The starburst size implies a high $Σ_{IR}$ of $4.7\times10^{12}$ $L_{\odot}$ kpc$^{-2}$, slightly below predictions of radiation-pressure limited starbursts. The HCN line profile has low-level wings, which we tentatively interpret as evidence for outflowing dense molecular gas. However, the dense molecular outflow seen in the HCN line wings is unlikely to escape the galaxy and is destined to return to the nucleus and fuel future star formation. We also present modeling of Herschel observations of the H$_2$O lines and find a nuclear dust temperature of $\sim40$ K. IRAS 13120-5453 has a lower dust temperature and $Σ_{IR}$ than is inferred for the systems termed "compact obscured nuclei" (such as Arp 220 and Mrk 231). If IRAS 13120-5453 has undergone a compact obscured nucleus phase, we are likely witnessing it at a time when the feedback has already inflated the nuclear ISM and diluted star formation in the starburst/AGN core.

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