相关论文: Local Distance Indicators
Over the last few years, low- and high-redshift observations set off a tension in the measurement of the present-day expansion rate, $H_0$. Adding to the riddle, observational data from the Planck mission point to a $3.4\sigma$ evidence for…
Cepheids are fundamental objects astrophysically in that they hold the key to a CMB independent estimate of Hubble's constant. A number of researchers have pointed out the possibilities of breaking degeneracies between Omega_Matter and H0…
We present an absolute parallax and relative proper motion for the fundamental distance scale calibrator, delta Cep. We obtain these with astrometric data from FGS 3, a white-light interferometer on HST. Utilizing spectrophotometric…
We present initial results from a time-series BVI survey of two fields in NGC 4258 using the Advanced Camera for Surveys onboard the Hubble Space Telescope. This galaxy was selected because of its accurate maser-based distance, which is…
The impact of metallicity on the Cepheid Leavitt law (LL) and, in turn, the Hubble constant, has been the subject of much recent debate. Here, we present a comprehensive analysis of metallicity effects on Cepheid LLs based on synthetic…
Cepheid stars are crucial objects for a variety of topics that range from stellar pulsation and the evolution of intermediate-mass stars to the understanding the structure of the Galaxy and the Universe through the distance measurements…
By comparing Cepheid brightnesses with geometric distance measures including Gaia EDR3 parallaxes, most recent analyses conclude metal-rich Cepheids are brighter, quantified as $\gamma \sim -0.2$ mag/dex. While the value of $\gamma$ has…
Recent developments in the determination of H0 are reviewed in the context of the 3 following questions: 1) What is required to measure an accurate value of H0? Given the wide range of H0 values quoted in the current literature, is there…
The Levenshtein distance is an important tool for the comparison of symbolic sequences, with many appearances in genome research, linguistics and other areas. For efficient applications, an approximation by a distance of smaller…
Classical Cepheids were the first stellar standard candles and have played a crucial role for astronomical distance measurements ever since the discovery of the Leavitt law (period-luminosity relation). Enormous improvements in distance…
We present preliminary results of an observational campaign devoted at establishing the influence of chemical composition on the Cepheid Period-Luminosity relation. The data are in good agreement with theoretical predictions based on…
We investigate the influence of blending on the Cepheid distance scale. Blending leads to systematically low distances to galaxies observed with HST, and therefore to systematically high estimates of the Hubble constant H_0. We select a…
We present an expanded sample of 75 Milky Way Cepheids with Hubble Space Telescope (HST) photometry and Gaia EDR3 parallaxes which we use to recalibrate the extragalactic distance ladder and refine the determination of the Hubble constant.…
In this paper we discuss and confront recent results on metallicity variations in the local interstellar medium, obtained from observations of HII regions and neutral clouds of the Galactic thin disk, and compare them with recent…
We have obtained deep images in the near-infrared J and K filters for several fields in the Local Group galaxy WLM. We report intensity mean magnitudes for 31 Cepheids located in these fields which we previously discovered in a wide-field…
The form and metallicity-dependence of Spitzer mid-infrared Cepheid relations are a source of debate. Consequently, Spitzer 3.6 and 4.5 um period-magnitude and period-color diagrams were re-examined via robust routines, thus providing the…
We report on the discovery of Cepheids in the field spiral galaxy NGC 3621, based on observations made with the Wide Field and Planetary Camera 2 on board the Hubble Space Telescope (HST). NGC 3621 is one of 18 galaxies observed as a part…
Log-Euclidean distances are commonly used to quantify the similarity between positive definite matrices using geometric considerations. This paper analyzes the behavior of this distance when it is used to measure closeness between…
Large-amplitude asymptotic giant branch variables potentially rival Cepheid variables as fundamental calibrators of the distance scale, particularly if observations are made in the infrared, or where there is substantial interstellar…
Classical Cepheid and RR Lyrae variables are radially pulsating stars that trace young and old-age stellar populations, respectively. These classical pulsating stars are the most sensitive probes for the precision stellar astrophysics and…