Reconnaissance with JWST of the J-region Asymptotic Giant Branch in Distance Ladder Galaxies: From Irregular Luminosity Functions to Approximation of the Hubble Constant (2401.04777v2)

Abstract: We study stars in the J-regions of the asymptotic giant branch (JAGB) of near-infrared color magnitude diagrams in the maser host NGC 4258 and 4 hosts of 6 Type Ia supernovae (SN Ia): NGC 1448, NGC 1559, NGC 5584, and NGC 5643. These clumps of stars are readily apparent near $1.0<F150W-F277W<1.5$ and $m_{F150W}$=22-25 mag with James Webb Space Telescope NIRCam photometry. Various methods have been proposed to assign an apparent reference magnitude for this recently proposed standard candle, including the mode, median, sigma-clipped mean or a modeled luminosity function parameter. We test the consistency of these by measuring intra-host variations, finding differences of up to $\sim$0.2 mag that significantly exceed statistical uncertainties. Brightness differences appear intrinsic, and are further amplified by the non-uniform shape of the JAGB luminosity function, also apparent in the LMC and SMC. We follow a 'many methods' approach to consistently measure JAGB magnitudes and distances to the SN Ia host sample calibrated by NGC 4258. We find broad agreement with distances measured from Cepheids, tip of the red giant branch (TRGB), and Miras. However, the SN host mean distance estimated via the JAGB method necessary to estimate $H_0$ differs by $\sim$0.19 mag amongst the above definitions, a result of different levels of luminosity function asymmetry. The methods yield a full range of $71-78$ km s$^{-1}$ Mpc$^{-1}$, i.e., a fiducial result of $H_0=74.7\pm2.1$ (stat) $\pm$2.3 (sys) ($\pm$3.1 if combined in quadrature) km s$^{-1}$ Mpc$^{-1}$, with systematic errors limited by the differences in methods. Future work may seek to further standardize and refine this promising tool, making it more competitive with established distance indicators.

• The paper demonstrates that JWST observations reveal 0.2-mag variations in JAGB stars across galaxies.
• It applies multiple statistical methodologies on near-infrared color-magnitude diagrams to assess standard candle reliability.
• The study estimates H0 values between 71–78 km s⁻¹ Mpc⁻¹, emphasizing the need for standardization in JAGB measurement.

Analysis of the JAGB Standard Candle via JWST Observations

The paper "Reconnaissance with JWST of the J-region Asymptotic Giant Branch in Distance Ladder Galaxies: From Irregular Luminosity Functions to Approximation of the Hubble Constant" presents a paper of the J-region Asymptotic Giant Branch (JAGB) as a potential standard candle using observations from the James Webb Space Telescope (JWST). The JAGB is considered for its potential to provide precise extragalactic distance measurements, which are essential for calculating the Hubble constant, $H_0$.

Study Overview

The researchers analyzed stars in the J-region of the asymptotic giant branch (JAGB) within the near-infrared color-magnitude diagrams corresponding to five galaxies: NGC 4258, NGC 1448, NGC 1559, NGC 5584, and NGC 5643. The paper utilized JWST’s NIRCam to obtain photometric data across different host galaxies. The goal is to test the reliability of JAGB stars as distance indicators by evaluating the consistency of reference magnitudes derived using various methodologies such as mode, median, sigma-clipped mean, and modeled luminosity function parameter.

Key Findings and Methodological Implications

The paper revealed significant intra-host variations in the JAGB reference magnitudes, exceeding statistical uncertainties. These variations suggest intrinsic differences in stellar populations or observational challenges associated with asymmetric and irregularly-shaped JAGB luminosity functions. The variations ranged up to about 0.2 magnitudes. This highlights the potential for systematic biases in using JAGB stars as standard candles unless standardized methodologies are implemented across different environments.

The paper compares JAGB-based distances to those obtained through other luminous indicators like Cepheids, Tip of the Red Giant Branch (TRGB), and Miras, finding reasonable agreement across different galaxies. Despite this, the variation in methods yields a range of 71-78 km s$^{-1}$ Mpc$^{-1}$ for the Hubble constant, denoting methodological uncertainties. A fiducial value of $H_0=74.7$ km s$^{-1}$ Mpc$^{-1}$ is proposed, but with highlighted systematic limitations due to methodological variations in JAGB standardization.

Practical and Theoretical Implications

The paper underscores the necessity for a standardized approach to utilizing JAGB stars as reliable cosmological tools. The paper affirms that while JAGB stars show potential in extending the cosmic distance ladder, a comprehensive understanding and adjustment for intrinsic variations and asymmetries in their luminosity functions are imperative for reducing systematic errors in distance measurements.

Additionally, the findings encourage further research into the physical properties influencing JAGB stars' luminosities, potentially tied to metallicity, age distributions, and intrinsic astrophysical dynamics. These insights could enhance the precision of JAGB-related distance measures, making them competitive with established methods.

Future Directions

Future investigations may focus on delineating the causes behind the observed asymmetries and irregularities in the JAGB luminosity functions. Such research could involve detailed spectral analysis to differentiate between possible stellar populations within the JAGB. Furthermore, expanding the sample of galaxies studied with JWST and contrasting data from other infrared observatories could offer insight into the universality of the JAGB and help calibrate a standardized method to mitigate the variation seen with current measurement techniques.

In conclusion, the paper presents meaningful advancements in the utility of JAGB stars in cosmology while also presenting challenges that require concerted effort to resolve for these stars to become a mainstay in distance measurement and Hubble constant estimation.