We present results of Hubble Space Telescope (HST) NICMOS H-band imaging of 73 of the most luminous (i.e., log[L IR/L ☉]11.4) infrared galaxies (LIRGs) in the Great Observatories All-sky LIRG Survey. This data set combines multi-wavelength imaging and spectroscopic data from space-based (Spitzer, HST, GALEX, and Chandra) and ground-based telescopes. In this paper, we use high-resolution near-infrared data to recover nuclear structure that is obscured by dust at optical wavelengths and measure the evolution in this structure along the merger sequence. A large fraction of all galaxies in our sample possess double nuclei (~63%) or show evidence for triple nuclei (~6%). Half of these double nuclei are not visible in the HST B-band images due to dust obscuration. The majority of interacting LIRGs have remaining merger timescales of 0.3-1.3?Gyr, based on the projected nuclear separations and the mass ratio of nuclei. We find that the bulge luminosity surface density L Bulge/R 2 Bulge increases significantly along the merger sequence (primarily due to a decrease of the bulge radius), while the bulge luminosity shows a small increase toward late merger stages. No significant increase of the bulge Sérsic index is found. LIRGs that show no interaction features have on average a significantly larger bulge luminosity, suggesting that non-merging LIRGs have larger bulge masses than merging LIRGs. This may be related to the flux-limited nature of the sample and the fact that mergers can significantly boost the IR luminosity of otherwise low luminosity galaxies. We find that the projected nuclear separation is significantly smaller for ULIRGs (median value of 1.2?kpc) than for LIRGs (median value of 6.7?kpc), suggesting that the LIRG phase appears earlier in mergers than the ULIRG phase.
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机译：我们在大天文台全天空LIRG调查中介绍了73个最明亮（即log [L IR / L☉]> 11.4）红外星系（LIRGs）的哈勃太空望远镜（HST）NICMOS H波段成像结果。该数据集结合了来自天基（Spitzer，HST，GALEX和Chandra）和地基望远镜的多波长成像和光谱数据。在本文中，我们使用高分辨率的近红外数据来恢复在光波长处被灰尘遮盖的核结构，并测量该结构沿合并序列的演化。在我们的样本中，所有星系中有很大一部分拥有双核（〜63％）或显示出三核（〜6％）的证据。由于灰尘的遮盖，这些双核的一半在HST B带图像中不可见。根据预计的核分离和核的质量比，大多数相互作用的LIRGs的合并时间尺度为0.3-1.3？Gyr。我们发现，凸起的光度表面密度L Bulge / R 2 Bulge沿着合并序列显着增加（主要是由于凸起半径的减小），而凸起的光度则在合并后期逐渐增加。没有发现凸出的Sérsic指数显着增加。没有相互作用特征的LIRGs平均具有明显更大的凸起发光度，这表明非合并的LIRGs具有比合并的LIRGs更大的凸起质量。这可能与样品的通量受限特性有关，并且合并可能会显着提高其他低光度星系的IR光度。我们发现，预计的ULIRGs（中值1.2？kpc）的核分离要比LIRGs（中值6.7？kpc）的核分离显着小，这表明LIRG阶段在合并中比ULIRG阶段出现得更早。
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