J/A+A/708/L8 Magellanic Cloud tip of the red giant branch (Cruz Reyes+, 2026)
Calibrating the tip of the red giant branch and measuring Magellanic Cloud
distances to ∼2% exclusively with Gaia.
Cruz Reyes M., Anderson R.I., Lengen B.
<Astron. Astrophys. 708, L8 (2026)>
=2026A&A...708L...8C 2026A&A...708L...8C (SIMBAD/NED BibCode)
ADC_Keywords: Magellanic Clouds ; Clusters, globular ; Optical
Keywords: stars: distances - stars: Population II - globular clusters: general -
Magellanic Clouds
Abstract:
We have calibrated the tip of the red giant branch (TRGB) using our
recent catalogue of homogeneous globular cluster (GC) distances. The
GC distances were determined via a global joint fit to optical
period-Wesenheit relations of their member RR Lyrae stars and
type-II Cepheids, anchored by trigonometric parallaxes; all data were
taken from the ESA Gaia mission's (early) third data release (GDR3).
Using I-band measurements of 48 GCs from P. Stetson's database, we
determined MI,0=-3.948+0.037-0.034mag (1.6% in distance).
Calibrating the TRGB using Gaia's homogeneous, space-based RP
photometry of 53 GCs, we found MRP,0=-3.807+0.041-0.035mag
(1.8%). The stated uncertainties include statistical and systematic
effects, including the correlated nature of the GC distances. The
robustness of our calibrations was evaluated via tests against
small-number statistics and analysis choices. Within the (small)
uncertainties, no significant metallicity effect is detected in our
sample of old, low-metallicity GCs. We measured approximately 2%
distances to the Large and Small Magellanic Clouds,
18.447+0.036-0.042mag (48.9±0.9kpc) and
18.898+0.049-0.054mag (60.2±1.4kpc), respectively, using a
single photometric system: RP (spectro-)photometry from GDR3. Our new
TRGB distances, whose absolute scale derives from Gaia parallaxes, are
fully independent of the well-known detached eclipsing binary (DEB)
distances and agree with them to within the uncertainties. Combining
our new TRGB and existing DEB distances, we illustrate how additional
constraints can be incorporated into the Local Distance Network and
obtain H0=73.52±0.80km/s/Mpc. Expected improvement thanks to the
upcoming fourth Gaia data release are discussed.
Description:
Clusters used for the TRGB calibration in each band.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablec2.dat 19 53 Clusters used for the TRGB calibration in each band
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Byte-by-byte Description of file: tablec2.dat
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Bytes Format Units Label Explanations
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1- 13 A13 --- Cluster Cluster name
15 I1 --- IStetson [0/1] Boolean flag indicating whether the cluster
was used in the TRGB calibration in the I band
17 I1 --- IGDR3 [0/1] Boolean flag indicating whether the cluster
was used in the I-band TRGB calibration
(based on photometric transformations)
19 I1 --- RP [0/1] Boolean flag indicating whether the cluster
was used in the RP-band TRGB calibration
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Acknowledgements:
Mauricio Cruz Reyes, mauricio.cruzre(at)gmail.com
License: CC-BY-4.0 [see https://spdx.org/licenses/]
(End) Patricia Vannier [CDS] 24-Mar-2026