http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
Beaton, Rachael L.,Freedman, Wendy L.,Madore, Barry F.,Bono, Giuseppe,Carlson, Erika K.,Clementini, Gisella,Durbin, Meredith J.,Garofalo, Alessia,Hatt, Dylan,Jang, In Sung,Kollmeier, Juna A.,Lee, Myun American Astronomical Society 2016 The Astrophysical journal Vol.832 No.2
<P>We present an overview of the Carnegie-Chicago Hubble Program, an ongoing program to obtain a 3% measurement of the Hubble constant (H-0) using alternative methods to the traditional Cepheid distance scale. We aim to establish a completely independent route to H-0 using RR Lyrae variables, the tip of the red giant branch (TRGB), and Type Ia supernovae (SNe Ia). This alternative distance ladder can be applied to galaxies of any Hubble type, of any inclination, and, using old stars in low-density environments, is robust to the degenerate effects of metallicity and interstellar extinction. Given the relatively small number of SNe. Ia host galaxies with independently measured distances, these properties provide a great systematic advantage in the measurement of H-0 via the distance ladder. Initially, the accuracy of our value of H-0 will be set by the five Galactic RR Lyrae calibrators with Hubble Space Telescope Fine-Guidance Sensor parallaxes. With Gaia, both the RR Lyrae zero-point and TRGB method will be independently calibrated, the former with at least an order of magnitude more calibrators and the latter directly through parallax measurement of tip red giants. As the first end-to-end 'distance ladder' completely independent of both Cepheid variables and the Large Magellanic Cloud, this path to H-0 will allow for the high-precision comparison at each rung of the traditional distance ladder that is necessary to understand tensions between this and other routes to H-0.</P>
GAIA PARALLAX ZERO POINT FROM RR LYRAE STARS
Andrew Gould,Juna A. Kollmeier 한국천문학회 2017 Journal of The Korean Astronomical Society Vol.50 No.1
Like Hipparcos, Gaia is designed to give absolute parallaxes, independent of any astrophysical reference system. And indeed, Gaia's internal zero-point error for parallaxes is likely to be smaller than any individual parallax error. Nevertheless, due in part to mechanical issues of unknown origin, there are many astrophysical questions for which the parallax zero-point error $\sigma(\pi_0)$ will be the fundamentally limiting constraint. These include the distance to the Large Magellanic Cloud and the Galactic Center. We show that by using the photometric parallax estimates for RR Lyrae stars (RRL) within 8kpc, via the ultra-precise infrared period-luminosity relation, one can independently determine a hyper-precise value for $\pi_{0}$. Despite their paucity relative to bright quasars, we show that RRL are competitive due to their order-of-magnitude improved parallax precision for each individual object relative to bright quasars. We show that this method is mathematically robust and well-approximated by analytic formulae over a wide range of relevant distances.