Updated 24 $\mu\mathrm{m}$ Period-Luminosity Relation Derived from Galactic Cepheids

TL;DR

This study updates the 24-micron period-luminosity relation for Galactic Cepheids using new photometry data, resulting in a refined relation with implications for distance measurements in astronomy.

Contribution

The paper provides the first updated 24-micron P-L relation for Galactic Cepheids incorporating new data and multiple distance sources, improving the accuracy of cosmic distance scaling.

Findings

The new P-L relation has a slope of -3.18 with an intrinsic dispersion of 0.20 mag.

Cepheids with trigonometric parallaxes yield steeper P-L slopes.

Statistical tests indicate differences in P-L relations based on distance measurement methods.

Abstract

In this work, we updated the catalog of Galactic Cepheids with $24\mu\mathrm{m}$ photometry by cross-matching the positions of known Galactic Cepheids to the recently released MIPSGAL point source catalog. We have added 36 new sources featuring MIPSGAL photometry in our analysis, thus increasing the existing sample to 65. Six different sources of compiled Cepheid distances were used to establish a $24\mu\mathrm{m}$ period-luminosity (P-L) relation. Our recommended $24\mu\mathrm{m}$ P-L relation is $M_{24\mu\mathrm{m}}=-3.18(\pm0.10)\log P - 2.46(\pm0.10)$, with an estimated intrinsic dispersion of 0.20 mag, and is derived from 58 Cepheids exhibiting distances based on a calibrated Wesenheit function. The slopes of the P-L relations were steepest when tied solely to the 10 Cepheids exhibiting trigonometric parallaxes from the Hubble Space Telescope and Hipparcos. Statistical tests suggest that these P-L relations are significantly different from those associated with other methods of distance determination, and simulations indicate that difference may arise from the small sample size.