Collaborative Project: Star Formation Processes in Irregular Galaxies

不规则星系是宇宙中最常见的星系类型。因为随着时间的推移，它们的进化相对缓慢，所以它们的化学性质类似于现在的螺旋星系和年轻星系的外部部分。然而，与螺旋不同的是，不规则星系在其星际介质中没有密度波，也没有切变。然而，大多数不规则星系都在持续形成恒星。因此，非相互作用的不规则星系使我们有机会在没有螺旋密度波和外部扰动的情况下研究恒星形成的过程。这些过程可能在螺旋星系中也起着重要的作用，但在那里它们被密度波的结果所掩盖。亨特博士正在与埃尔迈格林博士合作，以回答这个问题：在全球和局部尺度上，是什么调节了不规则星系的恒星形成活动？他们正在进行(1)量化恒星形成活动的性质和分布，(2)描述云和恒星形成的星际介质的特征，(3)将观测结果与模型结合起来，为这些系统中恒星形成的开始提供一幅真实的画面。观测在三个时间尺度上探测恒星形成：H a图像追踪最近的恒星形成，UBV图像整合了过去Gyr的恒星形成，而JHK图像整合了星系生命周期内的恒星形成。为了描述星际介质的特征，研究小组使用无线电干涉仪绘制HI线发射和吸收图。＊＊＊

AST-9802193 Hunter Irregular galaxies are the most common type of galaxy in the Universe. Because they have evolved relatively slowly over time, they chemically resemble the outer parts of present day spirals and young galaxies seen at large look-back times. Unlike spirals, however, irregulars have no density waves and less shear in their interstellar media. Yet, most irregulars have on-going star formation. Therefore, non-interacting irregular galaxies give us the opportunity to examine processes of star formation in the absence of spiral density waves and external perturbations. These processes may play an important role in spiral galaxies too, but there they are masked by the consequences of the density wave. Dr. Hunter is collaborating with Dr. Elmegreen to answer the question: What regulates the star formation activity in irregular galaxies on global and local scales? They are proceeding (1) to quantify the nature and distribution of the star formation activity, (2) to characterize the interstellar medium out of which clouds and stars form, and (3) to combine the observations with models to develop a realistic picture for the onset of star formation in these systems. The observations probe star formation on three timescales: H a images trace the most recent star formation, UBV images integrate the star formation over the past Gyr, and JHK images integrate the star formation over the lifetime of the galaxy. To characterize the interstellar medium, the team is using radio interferometer maps of HI line emission and absorption. ***