20 research outputs found
Observations of field and cluster RR Lyræ with Spitzer. Towards high precision distances with Population II stellar tracers
Indexación: Scopus.We present our project to calibrate the RR Lyræ period-luminosity-metallicity
relation using a sample of Galactic calibrators in the halo and globular clusters.https://www.epj-conferences.org/articles/epjconf/pdf/2017/21/epjconf_puls2017_07004.pd
Standard Galactic Field RR Lyrae II: A Gaia DR2 calibration of the period-Wesenheit-metallicity relation
RR Lyrae stars have long been popular standard candles, but significant
advances in methodology and technology have been made in recent years to
increase their precision as distance indicators. We present multi-wavelength
(optical and Gaia ; near-infrared ; mid-infrared
) period-luminosity-metallicity (PLZ),
period-Wesenheit-metallicity (PWZ) relations, calibrated using photometry
obtained from The Carnegie RR Lyrae Program and parallaxes from the Gaia second
data release for 55 Galactic field RR Lyrae stars. The metallicity slope, which
has long been predicted by theoretical relations, can now be measured in all
passbands. The scatter in the PLZ relations is on the order of 0.2 mag, and is
still dominated by uncertainties in the parallaxes. As a consistency check of
our PLZ relations, we also measure the distance modulus to the globular cluster
M4, the Large Magellanic Cloud (LMC) and the Small Magellanic Cloud (SMC), and
our results are in excellent agreement with estimates from previous studies.Comment: Accepted for publication in MNRAS, 15 pages, 14 figure
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The Carnegie-Chicago Hubble Program. VIII. An Independent Determination of the Hubble Constant Based on the Tip of the Red Giant Branch
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 (SNe Ia). We find a value of H0 = 69.8 ± 0.8 (±1.1% stat) ± 1.7 (±2.4% sys) km s−1 Mpc−1. 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 1.2σ level with that of the Planck Collaboration et al. estimate and at the 1.7σ level with the Hubble Space Telescope (HST) SHoES measurement of H0 based on the Cepheid distance scale. The TRGB distances have been measured using deep HST Advanced Camera for Surveys 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 stars, combined with an HST parallax calibration of a 3.6 μm 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 ( CSP-I ) sample containing about 100 well-observed SNe Ia . 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 those of the Cepheid sample, better matching the range of host-galaxy masses in the CSP-I distant sample and reducing potential systematic effects in the SNe Ia measurements
The Carnegie-Chicago Hubble Program. VIII. An Independent Determination of the Hubble Constant Based on the Tip of the Red Giant Branch
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.Comment: 60 pages, 20 figures, accepted for publication in the Astrophysical
Journa
The Carnegie-Chicago Hubble Program. VII. The Distance to M101 via the Optical Tip of the Red Giant Branch Method
The Carnegie-Chicago Hubble Program (CCHP) is building a direct path to the
Hubble constant (H0) using Population II stars as the calibrator of the SN
Ia-based distance scale. This path to calibrate the SN Ia is independent of the
systematics in the traditional Cepheid-based technique. In this paper, we
present the distance to M101, the host to SN2011fe, using the I-band tip of the
red giant branch (TRGB) based on observations from the ACS/WFC instrument on
the Hubble Space Telescope. The CCHP targets the halo of M101 where there is
little to no host-galaxy dust, the red giant branch is isolated from nearly all
other stellar populations, and there is virtually no source confusion or
crowding at the magnitude of the tip. Applying the standard procedure for the
TRGB method from the other works in the CCHP series, we find a
foreground-extinction-corrected M101 distance modulus of
{\mu_0}=29.07+/-0.04(stat)+/-0.05(sys) mag, which corresponds to a distance of
D=6.52+/-0.12(stat)+/-0.15(sys) Mpc. This result is consistent with several
recent Cepheid-based determinations, suggesting agreement between Population I
and II distance scales for this nearby SN Ia-host galaxy. We further analyze
four archival datasets for M101 that have targeted its outer disk to argue that
targeting in the stellar halo provides much more reliable distance measurements
from the TRGB method due to the combination of multiple structural components
and heavily population contamination. Application of the TRGB in complex
regions will have sources of uncertainty not accounted for in commonly used
uncertainty measurement techniques.Comment: 30 Pages, 12 Figures, 4 Tables; Figure quality degraded for ArXiv
posting; Accepted to ApJ. Note this version corrects an error regarding a
previous study, which is indicated in the tex
SMHASH:A new mid-infrared RR Lyrae distance determination for the Local Group dwarf spheroidal galaxy Sculptor
We present a new distance estimation for the Milky Way dwarf spheroidal
satellite Sculptor obtained from multi-epoch mid-infrared observations of RR
Lyrae stars. The 3.6 {\mu}m observations have been acquired with the Infrared
Array Camera on board the Spitzer Space Telescope as part of the SMHASH
Program. Mid-infrared light curves for 42 RRL were obtained, from which we
measured Sculptor's distance modulus to be {\mu} = 19.60 0.02
(statistical) 0.04 (photometric) mag (with = 0.09 mag),
using the 3.6 {\mu}m empirical period-luminosity relations derived from the
Galactic globular cluster M4, or {\mu} = 19.57 0.02 (statistical)
0.04 (photometric) mag (with = 0.11 mag) using empirical
relations in the same passband recently derived from the Large Magellanic Cloud
globular cluster Reticulum. Both these measurements are in good agreement with
values presented in previous works with Sculptor RR Lyrae stars in optical
bands, and are also consistent with recent near-infrared RR Lyrae results. Best
agreement with the literature is found for the latter modulus which is
equivalent to a distance of d = 82 1 (statistical) 2 (photometric)
kpc (with = 4 kpc). Finally, using a subsample of RR Lyrae
stars with spectroscopic metallicities, we demonstrate that these distance
estimates are not affected by metallicity effects.Comment: 24 pages, 11 figures. Accepted for publication in MNRA