查看“︁多普勒参数”︁的源代码

'''多普勒参数'''（{{lang-en|Doppler parameter}}），或'''多普勒致宽参数'''（{{lang-en|Doppler broadening parameter}}）是[[天体物理]]中常用来标示天体[[谱线]]宽度的物理量，通常用字母<math>b</math>表示。其定义为
:<math> b = \sqrt{2} \sigma, </math>
其中<math>\sigma</math>是一维[[速度弥散]]{{harv|Draine|2011|p=58}}。通过这一参数，产生该谱线的粒子的[[高斯分布|高斯速度分布]]可被表示为
:<math> p = \frac{1}{\sqrt{2\pi}}\frac{1}{\sigma}e^{-(v-v_0)^2/2\sigma^2} = \frac{1}{\sqrt{\pi}}\frac{1}{b}e^{-(v-v_0)^2/b^2},</math>
其中<math>p\mathrm{d}v</math>表示粒子的[[视向速度]]处于<math>[v, v + \mathrm{d}v]</math>区间内的概率。

谱线的宽度也经常用[[半峰全宽]]（FWHM）来表示，其与多普勒参数的转换关系为
:<math> \mathrm{FWHM} = 2\sqrt{2\ln 2}\sigma = 2\sqrt{\ln 2} b \approx 1.665b </math>.

== 分布 ==
[[莱曼α森林]]中的吸收线的多普勒参数通常分布在 10–100 km s<sup>−1</sup>，其中位数约为<math>b_m = 36\ \mathrm{km\ s}^{-1}</math>，且随[[红移]]递减{{harv|Kim|Hu|Cowie|Songaila|1997}}。通过分析[[哈勃空间望远镜]]上的[[宇宙起源頻譜儀]]观测的一批低红移[[类星体]]的数据得到多普勒参数的中位数约为<math>33\ \mathrm{km\ s}^{-1}</math>（{{harvnb|Danforth|Keeney|Tilton|Shull|2016}}，{{harvnb|Gaikwad|Srianand|Choudhury|Khaire|2017}}）。

== 参见 ==
* [[多普勒致宽]]
* [[都卜勒光譜學]]

== 参考文献 ==
{{Refbegin}}
* {{cite journal | last1 = Danforth | first1 = Charles W. | last2 = Keeney | first2 = Brian A. | last3 = Tilton | first3 = Evan M. | last4 = Shull | first4= Michael | title = An HST/COS Survey of the Low-redshift Intergalactic Medium. I. Survey, Methodology, and Overall Results | journal = {{ApJ}} | year = 2016 | volume = 817 | number = 2 | pages = 111 | arxiv = 1402.2655 | doi = 10.3847/0004-637X/817/2/111 | bibcode = 2016ApJ...817..111D | ref = harv}}

* {{cite book|first= Bruce|last= Draine|title=Physics of the Interstellar and Intergalactic Medium|publisher=Princeton University Press|year=2011|isbn= 9780691122144|bibcode=2011piim.book.....D|ref = harv}}

* {{cite journal | last1 = Gaikwad | first1 = Prakash | last2 = Srianand | first2 = Raghunathan | last3 = Choudhury | first3 = Tirthankar Roy | last4 = Khaire|first4=Vikram | title = VoIgt profile Parameter Estimation Routine (viper): H I photoionization rate at z \&lt; 0.5 | journal = {{MNRAS}} | year = 2017 | volume = 467 | number = 3 | pages = 3172–3187 | arxiv = 1610.06572 | doi = 10.1093/mnras/stx248 | bibcode = 2017MNRAS.467.3172G | ref = harv}}

* {{cite journal | last1 = Kim | first1 = Tae-Sun | last2 = Hu | first2 = Esther M. | last3 = Cowie | first3 = Lennox L. | last4 = Songaila | first4=Antoinette| title = The Redshift Evolution of the Ly alpha Forest | journal = {{AJ}} | year = 1997 | volume = 114 | pages = 1–13 | arxiv = astro-ph/9704184 | doi = 10.1086/118446 | bibcode = 1997AJ....114....1K | ref = harv}}
{{Refend}}

[[Category:多普勒效应]]
[[Category:天文光譜學]]