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Title: Comparative Analysis of TRGBs (CATs) from Unsupervised, Multi-halo-field Measurements: Contrast is Key
Abstract The tip of the red giant branch (TRGB) is an apparent discontinuity of the luminosity function (LF) due to the end of the red giant evolutionary phase and is used to measure distances in the local universe. In practice, tip localization via edge detection response (EDR) relies on several methods applied on a case-by-case basis. It is hard to evaluate how individual choices affect a distance estimation using only a single host field while also avoiding confirmation bias. To devise a standardized approach, we compareunsupervised, algorithmic analyses of the TRGB inmultiplehalo fields per galaxy. We first optimize methods for the lowest field-to-field dispersion, including spatial filtering, smoothing, and weighting of LF, color band selection, and tip selection based on the number of likely RGB stars and the ratio of stars below versus above the tip (R). We findR, which we call the tipcontrast, to be themost importantindicator of the quality of EDR measurements; higherRselection can decrease field-to-field dispersion. Further, sinceRis found to correlate with the age or metallicity of the stellar population based on theoretical modeling, it might result in a displacement of the detected tip magnitude. We find atip-contrast relationwith a slope of −0.023 ± 0.0046 mag/ratio, an ∼5σresult that can be used to correct these variations in the detections. When using TRGB to establish a distance ladder, consistent TRGB standardization using tip-contrast relation across rungs is vital to make robust cosmological measurements.  more » « less
Award ID(s):
2108616
PAR ID:
10558255
Author(s) / Creator(s):
; ; ; ; ; ; ;
Publisher / Repository:
IOP
Date Published:
Journal Name:
The Astrophysical Journal
Volume:
954
Issue:
1
ISSN:
0004-637X
Page Range / eLocation ID:
87
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
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