预先存在的矮星系、潮汐结和潮汐矮星系：对富含气体的相互作用星系群NGC 3166/9的无偏HI研究
Pre-existing dwarfs, tidal knots and a tidal dwarf galaxy: an unbiased HI study of the gas-rich interacting galaxy group NGC 3166/9
摘要：
我们提出了阿雷西博遗产快速ALFA（ALCAFA）和后续的巨型米波射电望远镜（GMRT）HI观测的气体丰富的相互作用组NGC 3166/9。敏感的ALOKFA数据提供了一个完整的人口普查的HI轴承系统的组，而高分辨率的GMRT数据阐明了它们的起源，使第一个公正的物理研究之一的富含气体的矮同伴和随后的识别第二代，潮汐矮星系在附近的一个群体。ALGOFA图揭示了NGC 3166/9群核心周围的扩展HI包络，我们使用跨越~1平方度的6个GMRT点以更高的分辨率拼接。对GMRT数据立方体的彻底搜索揭示了8个低质量天体，其气体质量从4x10^7到3x10^8 M_sol不等，总动力学质量高达1.4x10^9 M_sol。从GMRT数据中测量的HI通量的比较，在ALCAFA数据中测量的那些表明，一个显着的分数（约60%）的HI是平滑分布的尺度大于弧分（约7千秒差距，在NGC 3166/9的距离）。我们计算恒星质量和恒星形成率的八个低质量GMRT检测，使用辅助SDSS和GALEX数据，并使用这些值来约束它们的起源。大多数探测到的可能是预先存在的矮不规则星系，或者是短暂的潮汐形成的星系结;然而，一个候选者，AGC 208457，显然与延伸到NGC 3166下方的潮汐尾有关，表现出一个动力学气体质量比接近统一，并有恒星的内容和恒星形成率，这是大致一致的模拟以及候选潮汐矮星银河系从文学。因此，我们的观测结果强烈表明AGC 208457是一个潮汐矮星系。
英文摘要：
We present Arecibo Legacy Fast ALFA (ALFALFA) and follow-up Giant Metrewave Radio Telescope (GMRT) HI observations of the gas-rich interacting group NGC 3166/9. The sensitive ALFALFA data provide a complete census of HI-bearing systems in the group while the high-resolution GMRT data elucidate their origin, enabling one of the first unbiased physical studies of gas-rich dwarf companions and the subsequent identification of second generation, tidal dwarf galaxies in a nearby group. The ALFALFA maps reveal an extended HI envelope around the NGC 3166/9 group core, which we mosaic at higher resolution using six GMRT pointings spanning ~1 square degree. A thorough search of the GMRT datacube reveals eight low-mass objects with gas masses ranging from 4x10^7 to 3x10^8 M_sol and total dynamical masses up to 1.4x10^9 M_sol. A comparison of the HI fluxes measured from the GMRT data to those measured in the ALFALFA data suggests that a significant fraction (~60%) of the HI is smoothly distributed on scales greater than an arcminute (~7 kpc at the NGC 3166/9 distance). We compute stellar masses and star formation rates for the eight low-mass GMRT detections, using ancillary SDSS and GALEX data, and use these values to constrain their origin. Most of the detections are likely to be either pre-existing dwarf irregular galaxies or short-lived, tidally formed knots; however, one candidate, AGC 208457, is clearly associated with a tidal tail extending below NGC 3166, exhibits a dynamical to gas mass ratio close to unity and has a stellar content and star formation rate that are broadly consistent with both simulated as well as candidate tidal dwarf galaxies from the literature. Our observations therefore strongly suggest that AGC 208457 is a tidal dwarf galaxy.
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