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تسجيل مستخدم جديدConsistent Calibration of the Tip of the Red Giant Branch in the Large Magellanic Cloud on the Hubble Space Telescope Photometric System and a Re-determination of the Hubble Constant
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We present a calibration of the Tip of the Red Giant Branch (TRGB) in the Large Magellanic Cloud (LMC) on the HST/ACS F814W system. We use archival HST observations to derive blending corrections and photometric transformations for two ground-based wide-area imaging surveys of the Magellanic Clouds. We show that these surveys are biased bright by up to ~0.1 mag in the optical due to blending, and that the bias is a function of local stellar density. We correct the LMC TRGB magnitudes from Jang & Lee (2017) and use the geometric distance from Pietrzynski et al. (2019) to obtain an absolute TRGB magnitude of M_F814W=-3.97+/-0.046 mag. Applying this calibration to the TRGB magnitudes from Freedman et al. (2019) in SN Ia hosts yields a value for the Hubble constant of H_0=72.4+/-2.0 km/s/Mpc for their TRGB+SNe Ia distance ladder. The difference in the TRGB calibration and the value of H_0 derived here and by Freedman et al. (2019) primarily results from their overestimate of the LMC extinction, caused by inconsistencies in their different sources of TRGB photometry for the Magellanic Clouds. Using the same source of photometry (OGLE) for both Clouds and applying the aforementioned corrections yields a value for the LMC I-band TRGB extinction that is lower by 0.06 mag, consistent with independent OGLE reddening maps used by us and by Jang & Lee (2017) to calibrate TRGB and determine H_0.
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We present a new empirical (JHK) absolute calibration of the tip of the red giant branch (TRGB) in the Large Magellanic Cloud (LMC). We use published data from the extensive emph{Near-Infrared Synoptic Survey} containing 3.5 million stars, of which 6
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A zero point calibration of the Red Giant Branch Tip (TRGB) in the $I$-band is determined from OGLE photometry of the Magellanic Clouds (MCs). It is shown that TRGB measurements made in star-forming regions, with concomitantly high quantities of gas
and dust, are less precise and biased to fainter magnitudes, as compared to the same measurements made in quiescent regions. Once these low accuracy fields are excluded from consideration, the TRGB can be used for the first time to constrain the three-dimensional plane geometry of the LMC. Composite CMDs are constructed for the SMC and LMC from only those fields with well-defined TRGB features, and the highest accuracy TRGB zero point calibration to date is presented. The $I$-band TRGB magnitude is measured to be flat over the color range $ 1.45 < (V-I)_0 < 1.95$ mag, with a modest slope introduced when including metal-rich (up to $(V-I)_0 = 2.2$ mag) Tip stars into the fit. Both the flat, blue zero point and the shallow slope calibration are consistent with the canonical value of $-4.05$ mag for the old, metal-poor TRGB, and would appear to resolve a recent debate in the literature over the methods absolute calibration.
We present a new and independent determination of the local value of the Hubble constant based on a calibration of the Tip of the Red Giant Branch (TRGB) applied to Type Ia supernovae (SNeIa). We find a value of Ho = 69.8 +/- 0.8 (+/-1.1% stat) +/- 1
.7 (+/-2.4% sys) km/sec/Mpc. The TRGB method is both precise and accurate, and is parallel to, but independent of the Cepheid distance scale. Our value sits midway in the range defined by the current Hubble tension. It agrees at the 1.2-sigma level with that of the Planck 2018 estimate, and at the 1.7-sigma level with the SHoES measurement of Ho based on the Cepheid distance scale. The TRGB distances have been measured using deep Hubble Space Telescope (HST) Advanced Camera for Surveys (ACS) imaging of galaxy halos. The zero point of the TRGB calibration is set with a distance modulus to the Large Magellanic Cloud of 18.477 +/- 0.004 (stat) +/-0.020 (sys) mag, based on measurement of 20 late-type detached eclipsing binary (DEB) stars, combined with an HST parallax calibration of a 3.6 micron Cepheid Leavitt law based on Spitzer observations. We anchor the TRGB distances to galaxies that extend our measurement into the Hubble flow using the recently completed Carnegie Supernova Project I sample containing about 100 well-observed SNeIa. There are several advantages of halo TRGB distance measurements relative to Cepheid variables: these include low halo reddening, minimal effects of crowding or blending of the photometry, only a shallow (calibrated) sensitivity to metallicity in the I-band, and no need for multiple epochs of observations or concerns of different slopes with period. In addition, the host masses of our TRGB host-galaxy sample are higher on average than the Cepheid sample, better matching the range of host-galaxy masses in the CSP distant sample, and reducing potential systematic effects in the SNeIa measurements.
We present a precise optical and near-infrared determination of the Tip of the Red Giant Branch (TRGB) brightness in the Large and Small Magellanic Clouds (respectively LMC and SMC). The commonly used calibrations of the absolute magnitude of the TRG
B lead to an overestimation of the distance to the LMC and SMC in the K band, and an underestimation of the distance in the optical I band for both galaxies. Reported discrepancies are at the level of 0.2 mag, with respect to the very accurate distance determinations to both Clouds based on late-type eclipsing binaries. The differential distances between the LMC and SMC obtained in the J and K bands, and for the bolometric brightness are consistent with each other, and with the results obtained from eclipsing binaries and other distance indicators.
The Carnegie-Chicago Hubble Program (CCHP) is re-calibrating the extragalactic SN Ia distance scale using exclusively Population II stars. This effort focuses on the Tip of the Red Giant Branch (TRGB) method, whose systematics are entirely independen
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