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arXiv 1302.3464astro-ph.GA
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高分辨率电离气体动力学。II:在II Zw 40中发现双红外星团

Ionized Gas Kinematics at High Resolution. II: Discovery of a Double Infrared Cluster in II Zw 40

Sara Beck, Jean Turner, John Lacy, Thomas Greathouse, Ohr Lahad

摘要:

附近的矮星系II Zw 40是一个强烈的星暴。在星暴的中心是一个明亮的致密射电和红外源,被认为是一个巨大的密集HII区域,包含约14,000颗O星。射电连续谱图像表明,致密源实际上是几个较小发射区的集合。因此,我们使用的电离气体的运动学探测的无线电红外发射区的结构。利用NASA-IRTF上的TEXES,我们测量了10.5 μ m [SIV]发射线,有效光谱分辨率为~25和~3 km/s,空间分辨率为~1 "。线轮廓显示两个不同的,空间共延,发射功能。较强的特征是在银河系速度,并有47公里/秒的半高宽。第二个特征是约44km/s的第一个红向,具有32 km/s的FWHM。我们认为这是两个巨大的嵌入星系团,并估计它们的质量为~3x10^5 Mo和~1.5x10^5 Mo。对于如此小的空间偏移,速度偏移出乎意料地大。我们认为,它可能出现在一个以前未被发现的运动学特征剩余的暴力合并,形成了星系。

英文摘要:

The nearby dwarf galaxy II Zw 40 hosts an intense starburst. At the center of the starburst is a bright compact radio and infrared source, thought to be a giant dense HII region containing ~14,000 O stars. Radio continuum images suggest that the compact source is actually a collection of several smaller emission regions. We accordingly use the kinematics of the ionized gas to probe the structure of the radio-infrared emission region. With TEXES on the NASA-IRTF we measured the 10.5um [SIV] emission line with effective spectral resolutions, including thermal broadening, of ~25 and ~3 km/s and spatial resolution ~1". The line profile shows two distinct, spatially coextensive, emission features. The stronger feature is at galactic velocity and has FWHM 47 km/s. The second feature is ~44km/s redward of the first and has FWHM 32 km/s. We argue that these are two giant embedded clusters, and estimate their masses to be ~3x10^5Mo and ~1.5x10^5 Mo. The velocity shift is unexpectedly large for such a small spatial offset. We suggest that it may arise in a previously undetected kinematic feature remaining from the violent merger that formed the galaxy.

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