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arXiv 0905.1756astro-ph.GA
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用HI功率谱分析研究矮星系的ISM

A Study of ISM of Dwarf Galaxies Using HI Power Spectrum Analysis

Prasun Dutta, Ayesha Begum, Somnath Bharadwaj, Jayaram N. Chengalur

摘要:

我们估计了8个星系(7个矮星系和一个螺旋星系)的HI强度波动的功率谱。其中6个星系的功率谱可以拟合为幂律P_HI(U)= A U^α,表明湍流是可操作的。斜率的估计最佳拟合值范围为~ -1.5(AND IV、NGC 628、UGC 4459和GR 8)至~ -2.6(DDO 210和NGC 3741)。我们解释这种双模态是由于有效的二维湍流的长度尺度远大于规模的星系盘和3D的高度,否则。这使我们能够使用估计的斜率来设定样本中正面星系的尺度高度的界限。我们还发现,幂律斜率保持不变,因为我们增加了所有这些星系的通道厚度,这表明在HI强度的波动是由于密度波动,而不是速度波动,或速度结构函数的斜率是~ 0。最后,对于四个具有“二维湍流”的星系,我们发现斜率α与单位面积的恒星形成率相关,恒星形成率越大,幂律越陡。鉴于我们的样本量较小,这一结果需要用更大的样本来证实。

英文摘要:

We estimate the power spectrum of HI intensity fluctuations for a sample of 8 galaxies (7 dwarf and one spiral). The power spectrum can be fitted to a power law P_HI(U) = A U^αfor 6 of these galaxies, indicating turbulence is operational. The estimated best fit value for the slope ranges from ~ -1.5 (AND IV, NGC 628, UGC 4459 and GR 8) to ~ -2.6 (DDO 210 and NGC 3741). We interpret this bi-modality as being due to having effectively 2D turbulence on length scales much larger than the scale height of the galaxy disk and 3D otherwise. This allows us to use the estimated slope to set bounds on the scale heights of the face-on galaxies in our sample. We also find that the power law slope remains constant as we increase the channel thickness for all these galaxies, suggesting that the fluctuations in HI intensity are due to density fluctuations and not velocity fluctuations, or that the slope of the velocity structure function is ~ 0. Finally, for the four galaxies with "2D turbulence" we find that the slope αcorrelates with the star formation rate per unit area, with larger star formation rates leading to steeper power laws. Given our small sample size this result needs to be confirmed with a larger sample.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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