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首页> 外文期刊>The Astrophysical Journal. Letters >Cold dust but warm gas in the unusual elliptical galaxy NGC 4125
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Cold dust but warm gas in the unusual elliptical galaxy NGC 4125

机译：异常椭圆星系NGC 4125中的冷尘和热气体

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摘要

Data from the Herschel Space Observatory have revealed an unusual elliptical galaxy, NGC 4125, which has strong and extended submillimeter emission from cold dust but only very strict upper limits to its CO and H I emission. Depending on the dust emissivity, the total dust mass is 2-5 × 10~6 M_⊙. While the neutral gas-to-dust mass ratio is extremely low (<12-30), including the ionized gas traced by [C II] emission raises this limit to <39-100. The dust emission follows a similar r ~(1/4) profile to the stellar light and the dust to stellar mass ratio is toward the high end of what is found in nearby elliptical galaxies. We suggest that NGC 4125 is currently in an unusual phase where evolved stars produced in a merger-triggered burst of star formation are pumping large amounts of gas and dust into the interstellar medium. In this scenario, the low neutral gas-to-dust mass ratio is explained by the gas being heated to temperatures ≥10~4 K faster than the dust is evaporated. If galaxies like NGC 4125, where the far-infrared emission does not trace neutral gas in the usual manner, are common at higher redshift, this could have significant implications for our understanding of high redshift galaxies and galaxy evolution.
机译：赫歇尔太空天文台的数据显示了一个不寻常的椭圆星系NGC 4125，该星系从冷尘中发出强且扩展的亚毫米辐射，但其CO和H I辐射的上限非常严格。根据粉尘的发射率，总粉尘质量为2-5×10〜6M_⊙。尽管中性气体与粉尘的质量比非常低（<12-30），但包括通过[C II]发射追踪的离子化气体，会将这一限制提高到<39-100。尘埃的发射与恒星光具有相似的r〜（1/4）轮廓，尘埃与恒星的质量比接近于附近的椭圆星系。我们建议NGC 4125目前处于一个不寻常的阶段，在合并触发的恒星爆发中产生的恒星正在向星际介质中泵入大量的气体和尘埃。在这种情况下，中性气体与粉尘的质量比低是因为气体被加热到比粉尘蒸发快10到4 K的温度。如果像NGC 4125这样的星系在较高的红移时很常见，而远红外发射却无法以通常的方式追踪中性气体，那么这可能会对我们对高红移星系和星系演化的理解产生重大影响。

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