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
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.