The Stellar Content and the Star Formation History of the Local Group Dwarf Galaxy LGS 3
The Stellar Content and the Star Formation History of the Local Group Dwarf Galaxy LGS 3
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本星系群 LGS 3 的恒星含量和恒星形成历史
DOI：
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发表时间：
1997
期刊：
影响因子：
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通讯作者：
G. Bertelli
中科院分区：
文献类型：
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作者：
A. Aparicio;C. Gallart;G. Bertelli
利用736颗恒星的VRI光度图绘制的彩色星等（CM）图分析了矮星系LGS3的恒星形成历史（SFH）和性质。通过尖端或红巨星分支的位置来估计到星系的距离。得到了两个可接受的结果：0.77+/-0.07 Mpc和0.96+/-0.07 Mpc，尽管第一个值更受星系恒星含量的补充考虑的青睐。这两个值都表明LGS3可能是M31或M33的卫星。将观测到的CM图与不同恒星形成速率（psi(t)）和化学富集规律（Z(t)）计算的模型CM图进行比较，研究了两种采用距离下的SFH。
The star formation history (SFH) and the properties of the dwarf galaxy LGS3 are analyzed using color-magnitude (CM) diagrams plotted from VRI photometry of 736 stars. The distance to the galaxy is estimated through the position of the tip or the red giant branch. Two acceptable results have been obtained: 0.77+/-0.07 Mpc and 0.96+/-0.07 Mpc, although the first value is favored by complementary considerations on the stellar content of the galaxy. Both values make LGS3 a possible satellite of M31 or of M33. The SFH is investigated for each of the two adopted distances comparing the observed CM diagrams with model CM diagrams computed for different star formation rates (psi(t)) and chemical enrichment laws (Z(t)).
The results are compatible with LGS3 having been forming stars since an early epoch, 15-12 Gyr ago, at an almost constant rate if distance is 0.77 Mpc or at an exponentially decreasing rate if distance is 0.96 Mpc. According to our models, the current metallicity would range from Z~0.0007 to Z~0.002. Other results are the current psi(t): (0.55+/-0.04)x10^(-10) Mo yr^(-1) pc^(-2) or (0.47+/-0.07)x10^(-10) Mo yr^(-1) pc^(-2), depending of the distance, and its average for the entire life of the galaxy, =(1.4+/-0.1)x10^(-10) Mo yr^(-1) pc^(-2). At the present psi(t), the probability of LGS3 having an HII region is 0.2, which is compatible with the fact that no HII regions have been found in the galaxy. Its fraction of gas relative to the mass intervening in the chemical evolution is about 0.40 and its percentage of dark matter (that which cannot be explained as stellar remnants or by extrapolation of the used IMF to low masses) is 95%. The results for psi(t) and Z(t) for d=0.77 Mpc are compatible with a moderate outflow of well mixed material (lambda=3), but large