arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 2006.02258astro-ph.HEastro-ph.GA
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中红外核爆发附近星系的致密射电辐射

Compact Radio Emission from Nearby Galaxies with Mid-infrared Nuclear Outbursts

B. B. Dai, X. W. Shu, N. Jiang, L. M. Dou, D. Z. Liu, C. W. Yang, F. B. Zhang, T. G. Wang

摘要:

我们提出了5.5 GHz的观测与VLA附近的星系的样本与充满活力的核爆发在中红外(MIR)波段。这些观测结果达到了一个统一的深度下降到一个中位数均方根的~10 μ Jy,代表了一个最敏感的搜索与核瞬态无线电发射。我们在16个星系中的12个星系中检测到大于5 sigma的射电辐射,对应于75%的检测率。如此高的探测率与以前在恒星潮汐破裂事件中的类似搜索有很大不同。射电辐射是紧凑的,对于大多数尺度<0.5”(在z<0.1时<0.9 kpc)的源来说是无法分辨的。我们发现恒星形成对射电辐射有贡献的可能性很低,但活动星系核的起源仍然是一个合理的方案,特别是对于在其光谱中显示活动星系核活动证据的来源。如果探测到的辐射能代表与核瞬变现象(如喷流或外流)有关的射电辐射,我们就用类似于伽玛暴余辉的爆炸波模型来描述射电光变曲线的演化。在这种情况下,观测结果与稍后在离轴30 \degree -60 \degree观测到的能量约为10^{51-52} erg的减速喷流一致,这表明强大的喷流可能在MIR爆发星系中无处不在。未来的连续监测观测对于通过探测潜在通量和频谱演变来破译无线电发射的起源至关重要。我们的研究结果突出了射电观测的重要性,以限制星系中的核MIR爆发的性质。

英文摘要:

We present 5.5 GHz observations with the VLA of a sample of nearby galaxies with energetic nuclear outbursts at mid-infrared (MIR) bands. These observations reach a uniform depth down to a median rms of ~10 uJy, representing one of most sensitive searches for radio emission associated with nuclear transients. We detect radio emission in 12 out of 16 galaxies at a level of >5sigma, corresponding to a detection rate of 75%. Such a high detection is remarkably different from previous similar searches in stellar tidal disruption events. The radio emission is compact and not resolved for the majority of sources on scales of ~<0.5" (<0.9 kpc at z<0.1). We find the possibility of the star-formation contributing to the radio emission is low, but an AGN origin remains a plausible scenario, especially for sources that show evidence of AGN activity in their optical spectra. If the detections could represent radio emission associated with nuclear transient phenomenon such as jet or outflow, we use the blast wave model by analogy with the GRB afterglows to describe the evolution of radio light curves. In this context, the observations are consistent with a decelerating jet with an energy of ~10^{51-52} erg viewed at 30\degree-60\degree off-axis at later times, suggesting that powerful jets may be ubiquitous among MIR-burst galaxies. Future continuous monitoring observations will be crucial to decipher the origin of radio emission through detections of potential flux and spectral evolution. Our results highlight the importance of radio observations to constrain the nature of nuclear MIR outbursts in galaxies.

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