arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 2007.01317astro-ph.GAastro-ph.HEastro-ph.SR
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碰撞环内局部星暴条件和GRB 980425 / SN 1998 bw的形成

Local starburst conditions and formation of GRB 980425 / SN 1998bw within a collisional ring

M. Arabsalmani, F. Renaud, S. Roychowdhury, V. Arumugam, E. Le Floc'h, F. Bournaud, D. Cormier, M. A. Zwaan, L. Christensen, E. Pian, S. Madden, A. Levan

摘要:

我们提出了第一个空间分辨的研究分子气体在附近的伽马射线暴,使用CO(2-1)发射线观测与阿塔卡马大毫米阵列(ALMA)在~50 pc尺度。GRB 980425的宿主星系包含一个高柱密度的HI气体环,这可能是由于GRB宿主星系和它的伴星星系之间的碰撞而形成的。我们在星系中探测到11个分子气体团,其中7个在气环内。最接近伽玛暴位置的团簇的投影间距约为280秒差距。虽然这是合理的,伽玛射线暴的祖先是从集群中形成的,在这个丛喷射,我们认为,在原地形成的伽玛射线暴的祖先是最有可能的情况。我们测量了团块的分子气体质量,发现它们足以形成大质量的星团。团簇的分子气体耗尽时间显示出~2 dex的变化,与附近宇宙中星暴星系中发现的耗尽时间的大变化相当。这证明了在星系中局部尺度上存在恒星形成的星暴模式,即使星系作为一个整体不能根据其全球性质被归类为星暴。我们的研究结果表明,GRB 9802425的祖先起源于一个年轻的大质量星团,形成于恒星形成的星暴模式。

英文摘要:

We present the first spatially resolved study of molecular gas in the vicinity of a Gamma Ray Burst, using CO(2-1) emission line observations with the Atacama Large Millimetre Array (ALMA) at ~50 pc scales. The host galaxy of GRB 980425 contains a ring of high column density HI gas which is likely to have formed due to a collision between the GRB host and its companion galaxy, within which the GRB is located. We detect eleven molecular gas clumps in the galaxy, seven of which are within the gas ring. The clump closest to the GRB position is at a projected separation of ~280 pc. Although it is plausible that the GRB progenitor was ejected from clusters formed in this clump, we argue that the in situ formation of the GRB progenitor is the most likely scenario. We measure the molecular gas masses of the clumps and find them to be sufficient for forming massive star clusters. The molecular gas depletion times of the clumps show a variation of ~2 dex, comparable with the large variation in depletion times found in starburst galaxies in the nearby Universe. This demonstrates the presence of starburst modes of star formation on local scales in the galaxy, even while the galaxy as a whole cannot be categorised as a starburst based on its global properties. Our findings suggest that the progenitor of GRB 9802425 was originated in a young massive star cluster formed in the starburst mode of star formation.

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