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arXiv 1306.6276astro-ph.CO
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造父变星理论模型和HST/WFC3滤波器中的观测:对哈勃常数Ho的影响

Cepheid theoretical models and observations in HST/WFC3 filters: the effect on the Hubble constant Ho

G. Fiorentino, I. Musella, M. Marconi

摘要:

我们提出了一个完整的理论方案,经典造父变星在最常用的HST/WFC3过滤器,从光学(F555W,F606W和F814W)到近红外(F160W)波段。这样一项研究的重要性是与最近发布的新的经典造父变星观察与HST/WFC3在8个遥远的星系SNIa主机。这些观测结果对目前的距离尺度提出了合理的限制,哈勃常数Ho的不确定性小于3%。我们的模型探索了大范围的金属丰度和氦含量,从而为描述这些新的和未来的HST/WFC3观测提供了一个强大而独特的理论工具。正如预期的那样,F160W滤波器的周期-亮度(PL)关系与光学波段相比是线性的,并且稍微依赖于金属丰度,因此它似乎是限制造父变星与河外星系距离的最准确工具。我们比较了我们的理论方案与HST/WFC3-IR观测到的造父变星的脉动特性,我们讨论了所有调查的星系样本,包括NGC4258的情况下,与预测的不稳定带的协议。最后,采用我们的理论F160W PL关系(Z = 0.02,logP> 1.0),我们推导出新的距离模量。特别地,对于NGC 4258,我们导出了距离模μ 0 = 29.345 +-0.004 mag,σ = 0.34 mag,这与几何脉泽值非常一致。此外,使用获得的距离模量,我们估计的哈勃常数值,Ho = 76.0 +-1.9公里s-1 Mpc-1的最新文献值非常吻合。

英文摘要:

We present a complete theoretical scenario for classical Cepheids in the most commonly used HST/WFC3 filters, going from optical (F555W, F606W and F814W) to near-infrared (F160W) bands. The importance of such a study is related to the recent release of new classical Cepheids observed with HST/WFC3 in 8 distant galaxies where SNIa are hosted. These observations have posed sound constraints to the current distance scale with uncertainties on the Hubble constant Ho smaller than 3%. Our models explore a large range of metallicity and Helium content, thus providing a robust and unique theoretical tool for describing these new and future HST/WFC3 observations. As expected, the Period-Luminosity (PL) relation in F160W filter is linear and slightly dependent on the metallicity when compared with optical bands, thus it seems the most accurate tool to constrain extragalactic distances with Cepheids. We compare the pulsation properties of Cepheids observed with HST/WFC3-IR with our theoretical scenario and we discuss the agreement with the predicted Instability Strip for all the investigated galaxy samples including the case of NGC4258. Finally, adopting our theoretical F160W PL relation for Z=0.02 and log P>1.0, we derive new distance moduli. In particular, for NGC 4258, we derive a distance modulus mu0 = 29.345 +- 0.004 mag with a sigma = 0.34 mag, which is in very good agreement with the geometrical maser value. Moreover, using the obtained distance moduli, we estimate the Hubble constant value, Ho=76.0 +- 1.9 km s-1 Mpc-1 in excellent agreement with the most recent literature values.

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