The Disk and Extraplanar Regions of NGC 2403
The Disk and Extraplanar Regions of NGC 2403
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NGC 2403 的盘面和面外区域
DOI：
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发表时间：
2007
期刊：
影响因子：
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通讯作者：
T. Davidge
中科院分区：
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作者：
T. Davidge
利用加拿大-法国-夏威夷望远镜上的WIRCam和MegaCam获得的宽视场图像被用来探测SC星系NGC2403中年轻恒星的空间分布。明亮的主序星和蓝色超巨星被探测到沿长轴测量的~14kpc(~7盘尺度长度)的银心投影距离。根据明亮的主序星的数量计算，NGC2403星盘在过去10年的恒星形成率为1M☉yr-1。每单位r波段表面亮度的径向平均红超巨星数密度在整个圆盘中是恒定的，这表明(1)红超巨星跟随积分的r波段光，以及(2)当在几千万年的时间尺度上平均时，单位质量的红超巨星数密度与半径是恒定的。RSG的平均颜色随着银心距离的变化而变化，这表明在新形成的恒星中存在金属丰度梯度。亮主序星的径向平均数密度的比较也表明，在最近的历元中，NGC2403的单位恒星质量的SFR比NGC247的高约3倍，这与根据这些星系的远红外通量预测的结果大致一致。最后，利用这些数据研究了NGC2403的面外区域。在盘面上方12到14kpc的投影距离上探测到了峰值亮度为mk=-8的M个巨星群，并确定了6个新的球状星团候选者。
Wide-field images obtained with WIRCam and MegaCam on the Canada-France-Hawaii Telescope are used to probe the spatial distribution of young stars in the Sc galaxy NGC 2403. Bright main-sequence stars and blue supergiants are detected out to projected galactocentric distances of ~14 kpc (~7 disk scale lengths), as measured along the major axis. The star formation rate (SFR) in the disk of NGC 2403 during the past 10 Myr has been 1 M☉ yr-1 based on the number of bright main-sequence stars. The radially averaged number density of red supergiants (RSGs) per unit r-band surface brightness is constant throughout the disk, indicating that (1) RSGs follow the integrated r-band light, and (2) the SFR per unit mass has been constant with radius when averaged over timescales of a few tens of millions of years. The mean color of RSGs varies with galactocentric distance, suggesting that there is a metallicity gradient among recently formed stars. A comparison of the radially averaged number density of bright main-sequence stars also indicates that the SFR per unit stellar mass in NGC 2403 has been ~3 times higher than in NGC 247 during recent epochs, and this is in rough agreement with what would be predicted from the far-infrared fluxes of these galaxies. Finally, the data are used to investigate the extraplanar regions of NGC 2403. A population of M giants with peak brightness MK = -8 is detected at projected distances between 12 and 14 kpc above the disk plane, and six new globular cluster candidates are identified.