Deep GALEX Imaging of the COSMOS HST Field: A First Look at the Morphology of z ~ 0.7 Star-forming Galaxies-猫眼课题宝

DOI：

10.1086/516593

发表时间：

2007-01

期刊：

The Astrophysical Journal Supplement Series

影响因子：

通讯作者：

中科院分区：

其他

文献类型：

作者：

M. Zamojski;D. Schiminovich;R. Rich;B. Mobasher;A. Koekemoer;P. Capak;Y. Taniguchi;S. Sasaki;S. Sasaki;H. McCracken;Y. Mellier;E. Bertin;H. Aussel;H. Aussel;D. Sanders;O. Fèvre;O. Ilbert;M. Salvato;D. Thompson;J. Kartaltepe;N. Scoville;N. Scoville;T. Barlow;K. Forster;P. Friedman;D. C. Martin;P. Morrissey;S. Neff;M. Seibert;T. Small;T. Wyder;L. Bianchi;J. Donas;T. Heckman;Young-Wook Lee;B. F. Madore;B. Milliard;A. Szalay;B. Welsh;Sukyoung K. Yi

我们提出了一种研究红移z~0.7恒星形成星系的形态性质的方法，它结合了HST-ACS、GALEX和地面的宇宙场图像。我们的样本由8146个星系组成，其中5777个星系在GALEX近紫外线波段(2310？或~1360？Rest Frame)下被探测到，其极限星等为25.5(AB)，所有这些星系的亮度都为F814W(HST)&23 MAG，光度红移在0.55&lt；z&lt；0.8范围内。我们利用紫外线来估计恒星形成率，使用紫外线斜率来修正尘埃的影响，并利用地面多波段数据来计算质量。对于我们的样本中的所有星系，我们根据ACF814W图像计算了它们的浓度(C)、不对称性(A)和笨重(S)，以及它们的基尼系数(G)和最亮20%的光的二阶矩(M20)。我们在不对称和笨拙的星系群中观察到了双峰现象，尽管当这两个参数中的任何一个与类似浓度的参数(C、G或M20)相结合时，这种分离最为明显。我们进一步证明了这种形态双峰性与FUV-g颜色双峰性有很强的对应关系，并得出结论：紫外光的颜色主要是与形态同时演化的。我们观察到许多最具恒星形成的星系的形态接近于早期类型的星系，我们将此解释为证据，表明强烈的星暴事件与膨胀增长有关，并构成了一个过程，通过这个过程，星系可以从蓝色序列变成红色序列，同时相应地修改它们的形态。我们得出结论，红色序列在z≲0.7时继续增长。我们还观察到z~0.7星系具有与本星系相似的物理性质，只是恒星形成率较高。由此我们推断，恒星形成星系变暗是自红移以来恒星形成速率密度演化的主要原因，尽管我们的数据也与温和的数量演化相一致。

We present a study of the morphological nature of redshift z ~ 0.7 star-forming galaxies using a combination of HST ACS, GALEX, and ground-based images of the COSMOS field. Our sample consists of 8146 galaxies, 5777 of which are detected in the GALEX near-ultraviolet band (2310 Å or ~1360 Å rest frame) down to a limiting magnitude of 25.5 (AB), and all of which have a brightness of F814W(HST) < 23 mag and photometric redshifts in the range 0.55 < z < 0.8. We make use of the UV to estimate star formation rates, correcting for the effect of dust using the UV slope, and of the ground-based multiband data to calculate masses. For all galaxies in our sample, we compute, from the ACS F814W images, their concentration (C), asymmetry (A), and clumpiness (S), as well as their Gini coefficient (G) and the second moment of the brightest 20% of their light (M20). We observe a bimodality in the galaxy population in asymmetry and in clumpiness, although the separation is most evident when either of those parameters is combined with a concentration-like parameter (C, G, or M20). We further show that this morphological bimodality has a strong correspondence with the FUV-g color bimodality and conclude that UV-optical color predominantly evolves concurrently with morphology. We observe many of the most star-forming galaxies to have morphologies approaching that of early-type galaxies, and we interpret this as evidence that strong starburst events are linked to bulge growth and constitute a process through which galaxies can be brought from the blue to the red sequence while simultaneously modifying their morphology accordingly. We conclude that the red sequence has continued growing at z ≲ 0.7. We also observe z ~ 0.7 galaxies to have physical properties similar to that of local galaxies, except for higher star formation rates. Whence we infer that the dimming of star-forming galaxies is responsible for most of the evolution in star formation rate density since that redshift, although our data are also consistent with a mild number evolution.

Deep GALEX Imaging of the COSMOS HST Field: A First Look at the Morphology of z ~ 0.7 Star-forming Galaxies

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