Tip of the Red Giant Branch Distances with JWST: An Absolute Calibration in NGC 4258 and First Applications to Type Ia Supernova Hosts (2401.04776v2)

Abstract: The tip of the red giant branch (TRGB) allows for the measurement of precise and accurate distances to nearby galaxies, based on the brightest ascent of low-mass red giant branch stars before they undergo the helium flash. With the advent of JWST, there is great promise to utilize the technique to measure galaxy distances out to at least 50 Mpc, significantly further than HST's reach of 20 Mpc. However, with any standard candle, it is first necessary to provide an absolute reference. Here we use Cycle 1 data to provide an absolute calibration in the F090W filter. F090W is most similar to the F814W filter commonly used for TRGB measurements with HST, which had been adopted by the community due to minimal dependence from the underlying metallicities and ages of stars. The imaging we use was taken in the outskirts of NGC 4258, which has a direct geometrical distance measurement from the Keplerian motion of its water megamaser. Utilizing several measurement techniques, we find $M_{TRGB}^{F090W}$ = -4.362 $\pm$ 0.033 (stat) $\pm$ 0.045 (sys) mag (Vega) for the metal-poor TRGB. We also perform measurements of the TRGB in two Type Ia supernova hosts, NGC 1559, and NGC 5584. We find good agreement between our TRGB distances and previous distance determinations to these galaxies from Cepheids ($\Delta$ = 0.01 $\pm$ 0.06 mag), with these differences being too small to explain the Hubble tension ($\sim$0.17 mag). As a final bonus, we showcase the serendipitous discovery of a faint dwarf galaxy near NGC 5584.

• The paper refines the TRGB calibration using JWST F090W observations in NGC 4258 for precise extragalactic distance measurements.
• It validates Cepheid-based distances in Type Ia SN hosts with a negligible 0.01 ± 0.06 mag offset, reinforcing the reliability of distance ladders.
• The study extends TRGB measurements to 50 Mpc, offering enhanced insights into cosmic expansion and contributing to resolving the Hubble tension.

Analysis of TRGB Distances using JWST Observations

The investigation presented in the discussed paper focuses on utilizing the tip of the red giant branch (TRGB) as a distance indicator in the context of extragalactic astronomy, with particular emphasis on using the James Webb Space Telescope (JWST) for these measurements. The paper thoroughly explores the potential of extending the range to which reliable TRGB distance estimates can be made, improving on the previous capabilities afforded by the Hubble Space Telescope (HST).

Key Insights from the Methodology

The work employs the newly available observations from the JWST's Cycle 1 program (GO-1685) to refine the absolute calibration of the TRGB, particularly through the F090W filter. This specific filter choice aligns closely with HST's F814W, which has been the standard in the field due to its minimal dependence on stellar population variations such as age and metallicity.

The absolute calibration is conducted in NGC 4258, a critical galaxy given its well-determined geometric distance via a water megamaser. The calculated TRGB magnitude in the F090W filter is noted as $$M_{F090W} = -4.362 \pm 0.033 \, \text{(stat)} \pm 0.045 \, \text{(sys)} \, \text{mag}$$. The systematic and statistical uncertainties are diligently quantified, highlighting factors such as photometric calibration accuracy and intrinsic TRGB variability.

Strong Numerical Results

The paper robustly confirms an agreement between the new TRGB measurements and previous Cepheid-based distance estimates to two Type Ia supernova host galaxies, NGC 1559 and NGC 5584. The reported difference of $\Delta = 0.01 \pm 0.06 \, \text{mag}$ underscores the consistency between Cepheid and TRGB methodologies in these cases and indicates that this minor discrepancy falls short of explaining the widely recognized Hubble tension.

Implications and Future Directions

This calibration offers a significant resource for future research, particularly as the astronomical community seeks a clearer picture of cosmic expansion and the so-called Hubble tension. The ability to extend TRGB measurements out to at least 50 Mpc with the JWST represents a fivefold increase over HST's capabilities, promising more comprehensive coverage of the local volume. The implications for probing the Hubble constant are considerable, as more precise distance measurements enable a robust cross-validation of different cosmic distance ladders.

Moreover, the JWST's elevated resolution and sensitivity expand the observational horizon, enabling data acquisition at greater distances where crowding and K-corrections become significant considerations. Such advances are crucial for disentangling the intricacies of cosmic distance scales and refining the statistical and systematic uncertainties associated with TRGB-derived measurements.

Conclusion

The paper's calibration of the TRGB in the JWST regime enhances our available toolkit for precision cosmology. Moving forward, these measurements will play a pivotal role in reconciling discrepancies in the Hubble constant and facilitate more sophisticated comparisons with Cepheid variables and other distance indicators. The groundwork laid within this framework will be foundational for numerous forthcoming investigations utilizing the JWST and adds substantial value to the ongoing discourse in precision cosmology. Future work should focus on further refining these calibration techniques and applying them across an expanded sample of galaxies to build a more comprehensive understanding of the universe's expansion history.