论文标题
使用逼真的宿主星系金属率来改善GRB X射线等效总氢柱密度并限制白平时间的中等密度
Using realistic host galaxy metallicities to improve the GRB X-ray equivalent total hydrogen column density and constrain the intergalactic medium density
论文作者
论文摘要
众所周知，GRB等效氢柱密度（NHX）随红移而变化，并且通常，NHX大于GRB宿主中性氢柱密度。我们已经编制了大量的GRB NHX和金属性数据样本[X/H]。本文的主要目的是通过使用实际的金属度，可用于检测的情况下校正粉尘，以及剩余的GRB来生成改进的NHX，并使用太阳能的标准调整来实现更现实的平均内在金属性。然后，通过使用针对电离分数调整的测量中性柱（NHI，IC）近似GRB宿主固有氢柱密度，我们将对层次间介质（IgM）贡献进行更准确的估计值。 GRB样品平均金属度为= -1.17 +/- 0.09 RMS（或0.07 +/- 0.05 Z/ZSOL），来自36 GRB样品，带有红移1.76 <Z <5.91，大大低于用于许多拟合NHX标准的太阳能金属性的假设。下GRB宿主的平均金属度导致估计的NHX增加，而校正缩放为log（NHX CM-2）=（0.59 +/- 0.04）log（1+Z）+0.18 +/- 0.02。在我们样本中的NHX和NHI数据的128 GRB中，只有6个具有NHI，IC> nhx时，当假定太阳金属性时，进行了NHI，IC> NHx。通过log（nhx -nhi，ic cm -2）拟合对红移绘制的修订后的nhx -nhi，ic的下部信封= 20.3 + 2.4 log（1 + z）。这是对红移的最大IgM氢柱密度的估计值。使用这种方法，我们估计红移零（N0）处的氢密度的上限与N0 = 0.17 x 10-7cm-3一致。
It is known that the GRB equivalent hydrogen column density (NHX) changes with redshift and that, typically, NHX is greater than the GRB host neutral hydrogen column density. We have compiled a large sample of data for GRB NHX and metallicity [X/H]. The main aims of this paper are to generate improved NHX for our sample by using actual metallicities, dust corrected where available for detections, and for the remaining GRB, a more realistic average intrinsic metallicity using a standard adjustment from solar. Then, by approximating the GRB host intrinsic hydrogen column density using the measured neutral column (NHI,IC) adjusted for the ionisation fraction, we isolate a more accurate estimate for the intergalactic medium (IGM) contribution. The GRB sample mean metallicity is = -1.17+/-0.09 rms (or 0.07+/-0.05 Z/Zsol) from a sample of 36 GRB with a redshift 1.76 < z < 5.91, substantially lower than the assumption of solar metallicity used as standard for many fitted NHX . Lower GRB host mean metallicity results in increased estimated NHX with the correction scaling with redshift as log (NHX cm-2) = (0.59+/-0.04)log(1+z) + 0.18+/-0.02. Of the 128 GRB with data for both NHX and NHI,IC in our sample, only 6 have NHI,IC > NHX when revised for realistic metallicity, compared to 32 when solar metallicity is assumed. The lower envelope of the revised NHX - NHI,IC, plotted against redshift can be fit by log(NHX - NHI,IC cm-2) =20.3 + 2.4 log(1+z). This is taken to be an estimate for the maximum IGM hydrogen column density as a function of redshift. Using this approach, we estimate an upper limit to the hydrogen density at redshift zero (n0) to be consistent with n0 = 0.17 x 10-7cm-3.
