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EVIDENCE OF A HIGH CARBON ABUNDANCE IN THE LOCAL INTERSTELLAR CLOUD

机译:局部星际云中高碳丰度的证据

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The nature of the local interstellar cloud (LIC) is highly constrained by the combination of in situ heliospheric and line-of-sight data toward nearby stars. We present a new interpretation of the LIC components of the absorption-line data toward ε CMa, based on recent atomic data that include new rates for the Mg~+ to Mg~0 dielectronic recombination rate, and using in situ measurements of the temperature and density of neutral helium inside of the heliosphere. With these data we are able to place interesting limits on the gas-phase abundance of carbon in the LIC. If the C/S abundance ratio is solar, ~20, then no simultaneous solution exists for the N(Mg I), N(Mg II), N(C II), and N(C II~*) data. The combined column density and in situ data favor an abundance ratio A_C/A_s = 47_(-26)~(+22). We find that the most probable gas-phase C abundance is in the range 400-800 ppm with a lower limit of ~330. We speculate that such a supersolar abundance could have come to be present in the LIC via destruction of decoupled dust grains. Similar enhanced C/H ratios are seen in very low column density material, N(H) < 10~(19) cm~(-2), toward several nearby stars.
机译:本地星际云(LIC)的性质受到对附近恒星的原位日光层数据和视线数据的高度限制。基于最近的原子数据,包括对Mg〜+到Mg〜0双电子复合率的新速率,以及使用温度和温度的原位测量,我们对εCMa的吸收线数据的LIC成分提出了新的解释。太阳圈内部中性氦的密度。利用这些数据,我们可以对LIC中碳的气相丰度进行有趣的限制。如果C / S丰度比是太阳光,约为20,则对N(Mg I),N(Mg II),N(C II)和N(C II〜*)数据不存在同时求解。组合的柱密度和原位数据有利于丰度比A_C / A_s = 47 _(-26)〜(+22)。我们发现最可能的气相C丰度在400-800 ppm范围内,下限为〜330。我们推测这样的超太阳丰度可能通过破坏解耦的尘埃颗粒而出现在LIC中。在极低的柱密度材料中,N(H)<10〜(19)cm〜(-2)朝向附近的几颗恒星,C / H比也有所提高。

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