论文标题
处女座集群中的中间质量早期型磁盘星系。 ii。近红外光谱和进化差异的证据
Intermediate-mass Early-type Disk Galaxies in the Virgo Cluster. II. Near-Infrared Spectra and Evidence for Differences in Evolution
论文作者
论文摘要
我们讨论处女座群集中六个早期型磁盘星系的近红外（NIR）狭缝光谱。虽然CO（2,0）频带的深度与具有太阳或略微下极度发光度的金属的这些星系中心一致，但在NAI 2.21UM Doublet的深度中，星系到半脉冲的变化是在三个Galaxies中（NAI2.21UM）（NGC 44491，NGC 45444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444 eash and ngc and ngc 454444 eash and nai2.21）预测用于太阳能化学混合物和太阳邻化质量功能。考虑到Davidge（2018a）发现的NAD线的深度，深度NAI2.21UM线暂时归因于底部较重的质量功能。这与观察到的质量斜率和速度分散体之间观察到的趋势相反。具有深NAI2.21UM（NGC 4584和NGC 4620）的三个星系中的两个具有与经典凸起一致的刻度指数。至于NGC 4491，其中央NIR光谱包含突出的发射线。 Brgamma和H_2S（1）的相对强度，[FEII]发射的存在以及中红外光谱 - 能源分布都与该星系中心附近的近期恒星形成一致。在1.76UM中包含Ballick-Ramsey C_2带的波长与中等金属贫困的E-Miles模型光谱匹配，年龄为2 Gyr。可以得出结论，这些星系至少在群集环境中发展了至少几个回旋。
We discuss near-infrared (NIR) slit spectra of six early-type disk galaxies in the Virgo Cluster. While the depth of the CO(2,0) band is consistent with the centers of these galaxies having solar or slightly sub-solar luminosity-weighted metallicities, galaxy-to-galaxy variations in the depth of the NaI 2.21um doublet are found, with NaI2.21um lines in three galaxies (NGC 4491, NGC 4584, and NGC 4620) that are deeper than those predicted for a solar chemical mixture and a solar-neighborhood mass function. Considering the depth of the NaD lines found by Davidge (2018a), the deep NaI2.21um lines are tentatively attributed to a bottom-heavy mass function. This is counter to observed trends between mass function slope and velocity dispersion. Two of the three galaxies with deep NaI2.21um (NGC 4584 and NGC 4620) have Sersic exponents that are consistent with a classical bulge. As for NGC 4491, its central NIR spectrum contains prominent emission lines. The relative strengths of Brgamma and H_2S(1), the presence of [FeII] emission, and the mid-infrared spectral-energy distribution are all consistent with intense recent star formation near the center of that galaxy. Wavelengths that contain the Ballick-Ramsey C_2 band at 1.76um are matched by moderately metal-poor E-MILES model spectra with an age of 2 Gyr. It is concluded that these galaxies have evolved in a cluster environment for at least several Gyr.
