A Study of Two Diffuse Dwarf Galaxies in the Field
A Study of Two Diffuse Dwarf Galaxies in the Field
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DOI：
10.3847/1538-4357/aae0f4
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发表时间：
2018-05
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影响因子：
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通讯作者：
J. Greco;A. Goulding;J. Greene;M. Strauss;Song Huang;J. H. Kim;Y. Komiyama
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作者：
J. Greco;A. Goulding;J. Greene;M. Strauss;Song Huang;J. H. Kim;Y. Komiyama
本文对最近由超级超级-卡姆斯巴鲁战略计划（HSC-SSP）发现的两个漫射矮星系LSBG-285和LSBG-750进行了光学长缝光谱和远紫外-中红外光谱能量分布拟合。我们使用Hα线发射测量红移，并发现这些星系在校正本地速度场后分别处于≈25和≈41 Mpc的共同距离。它们的有效半径分别为1.2和1.8 kpc，质量为M -百科≈(2-3)× 107 M⊙。在距离LSBG-285至少1.5 Mpc和距离LSBG-750至少2 Mpc的移动距离内，没有大质量星系（）。这些源在大小和表面亮度上与超漫射星系相似，除了它们是孤立的，恒星形成的物体，是在环境盲调查中光学选择的。这两个星系可能具有较低的恒星金属丰度[Z -百科/Z⊙]< - 1.0，并且与矮星系的恒星质量-金属丰度关系一致。我们设定了LSBG-750旋转速度的上限为~ 50 km s - 1，这与具有类似恒星质量的矮星系相当，估计晕质量<1011 M⊙。我们发现初步证据表明，这两个弥漫性系统中的气相金属丰度相对于它们的恒星质量来说都很高，尽管有必要在非常低的表面亮度下进行统计完整的光学选择星系样本，以便将这些结果与更高表面亮度的星系群联系起来。
We present optical long-slit spectroscopy and far-ultraviolet to mid-infrared spectral energy distribution fitting of two diffuse dwarf galaxies, LSBG-285 and LSBG-750, which were recently discovered by the Hyper Suprime-Cam Subaru Strategic Program (HSC-SSP). We measure redshifts using Hα line emission and find that these galaxies are at comoving distances of ≈25 and ≈41 Mpc, respectively, after correcting for the local velocity field. They have effective radii of reff = 1.2 and 1.8 kpc and stellar masses of M⋆ ≈ (2–3) × 107 M⊙. There are no massive galaxies ( ) within a comoving separation of at least 1.5 Mpc from LSBG-285 and 2 Mpc from LSBG-750. These sources are similar in size and surface brightness to ultradiffuse galaxies, except they are isolated, star-forming objects that were optically selected in an environmentally blind survey. Both galaxies likely have low stellar metallicities [Z⋆/Z⊙] < −1.0 and are consistent with the stellar mass–metallicity relation for dwarf galaxies. We set an upper limit on LSBG-750's rotational velocity of ∼50 km s−1, which is comparable to dwarf galaxies of similar stellar mass with estimated halo masses <1011 M⊙. We find tentative evidence that the gas-phase metallicities in both of these diffuse systems are high for their stellar mass, though a statistically complete, optically selected galaxy sample at very low surface brightness will be necessary to place these results into context with the higher surface brightness galaxy population.