论文标题

Taffy星系中的CO排放(UGC 12914/5)在60pc决议-I:动荡的塔夫桥中的恒星形成之战

The CO emission in the Taffy Galaxies (UGC 12914/5) at 60pc resolution-I: The battle for star formation in the turbulent Taffy Bridge

论文作者

Appleton, P. N., Emonts, B., Lisenfeld, U., Falgarone, E., Guillard, P., Boulanger, F., Braine, J., Ogle, P., Struck, C., Vollmer, B., Yeager, T.

论文摘要

我们以0.2 ArcSec(60 pc)的CO发射(UGC 12914/5)的空间分辨率提出了ALMA观察结果。将观察结果与窄带PA $α$,MID-IR,无线电连续体和X射线成像以及光谱法进行了比较。星系已经发生了最近的正面碰撞,形成了一座巨大的气态桥梁,该桥梁已知是高度动荡的。该桥包含一个复杂的狭窄分子细丝和团块的网络。大多数细丝没有恒星形成,并且明显低于正常星系的Kennicutt-Schmidt关系,尤其是对于在PA $α$发射中未被发现的众多地区。在松散连接的丝和气体团块中,我们发现高速散布的区域,这些区域在$ x _ {\ rm co} $的广泛可能值中似乎在重力上似乎是不绑定的。就像天线系统中的“鞭炮”区域一样,它们需要极高的外部动力压力或热压力,以阻止它们在2-5〜myrs的短时间尺度上迅速消散。我们建议云可能是高度湍流的多相培养基中的瞬态结构,该介质强烈抑制了恒星的形成。尽管系统中的总体湍流,但恒星似乎已经在KPC大小的HII区域内的紧凑型热点中形成,其中分子气体的速度分散体比其他地方较低,并显示出与电离气体云发生碰撞的证据。就像斯蒂芬五重奏组中令人震惊的气体一样,塔夫桥的条件表明,在湍流,多相,气体中形成恒星有多困难。

We present ALMA observations at a spatial resolution of 0.2 arcsec (60 pc) of CO emission from the Taffy galaxies (UGC 12914/5). The observations are compared with narrow-band Pa$α$, mid-IR, radio continuum and X-ray imaging, plus optical spectroscopy. The galaxies have undergone a recent head-on collision, creating a massive gaseous bridge which is known to be highly turbulent. The bridge contains a complex web of narrow molecular filaments and clumps. The majority of the filaments are devoid of star formation, and fall significantly below the Kennicutt-Schmidt relationship for normal galaxies, especially for the numerous regions undetected in Pa$α$ emission. Within the loosely connected filaments and clumps of gas we find regions of high velocity dispersion which appear gravitationally unbound for a wide range of likely values of $X_{\rm CO}$. Like the "Firecracker" region in the Antennae system, they would require extremely high external dynamical or thermal pressure to stop them dissipating rapidly on short crossing timescales of 2-5~Myrs. We suggest that the clouds may be transient structures within a highly turbulent multi-phase medium which is strongly suppressing star formation. Despite the overall turbulence in the system, stars seem to have formed in compact hotspots within a kpc-sized extragalactic HII region, where the molecular gas has a lower velocity dispersion than elsewhere, and shows evidence for a collision with an ionized gas cloud. Like the shocked gas in the Stephan's Quintet group, the conditions in the Taffy bridge shows how difficult it is to form stars within a turbulent, multi-phase, gas.

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