标题： 近距旋涡星系中年轻星团的近红外观测 显示英文标题

标题： NIR view on young stellar clusters in nearby spirals

摘要： 近红外（NIR）观测允许对旋涡星系中的年轻恒星团进行详细研究，这些星系在可见光波段通常由于臂上的尘埃带而高度被遮挡。 使用HAWK-I/VLT获得了10个螺旋星系的深JHK图。 这里展示了NGC 2997的数据，以说明样本的一般结果。 (H-K)-(J-H)图表明，比7 Myr年轻的大多数恒星团受到尘埃显著消光，视觉消光可达7星等。 在(J-K)-Mk图中，较年轻和较老的星团复合体之间存在一个间隙，这表明在约7 Myr时消光迅速减少，可能是超新星爆发后尘埃和气体被驱散所致。 星团光度函数与指数为alpha ~ 2的幂律一致。 Mk = -15星等的星团光度达到，对应的质量接近10^6 Mo，没有截止的迹象。 它们相对于主旋臂的方位角显示，最 massive 的星团是在旋臂区域形成的，而较暗的星团也出现在旋臂之间。 较老的星团分布更均匀，相对于旋臂的调制较弱。 显示英文摘要

摘要： Observations in the near-infrared (NIR) allow a detailed study of young stellar clusters in grand-design spiral galaxies which in visual bands often are highly obscured by dust lanes along the arms. Deep JHK-maps of 10 spirals were obtained with HAWK-I/VLT. Data for NGC 2997 are presented here to illustrate the general results for the sample. The (H-K)-(J-H) diagrams suggest that most stellar clusters younger than 7 Myr are significantly attenuated by dust with visual extinctions reaching 7 mag. A gap between younger and older cluster complexes in the (J-K)-Mk diagram indicates a rapid reduction of extinction around 7 Myr possibly due to expulsion of dust and gas after supernovae explosions. The cluster luminosity function is consistent with a power law with an exponent alpha ~ 2. Cluster luminosities of Mk = -15 mag are reached, corresponding to masses close to 10^6 Mo, with no indication of a cut-off. Their azimuthal angles relative to the main spiral arms show that the most massive clusters are formed in the arm regions while fainter ones also are seen between the arms. Older clusters are more uniformly distribution with a weaker modulation relative to the arms.