Searching for chameleon-like scalar fields with the ammonia method. II. Mapping of cold molecular cores in NH3 and HC3N lines

TL;DR

This study investigates potential variations in the electron-to-proton mass ratio in interstellar environments by mapping molecular cores and analyzing velocity offsets between NH3 and HC3N lines, suggesting a possible increase in mu under low-density conditions.

Contribution

It provides the first detailed mapping of molecular cores to assess systematic effects on velocity offsets related to fundamental constant variations.

Findings

Detected consistent velocity offsets of ~27 m/s in two cores.

Estimated a potential increase in mu of about 26 x 10^{-9} in interstellar conditions.

Mapped molecular cores to evaluate systematic effects on velocity measurements.

Abstract

(Abridged) In our previous work we found a statistically significant offset Delta V = 27 m/s between the radial velocities of the HC3N(2-1) and NH3(1,1) transitions observed in molecular cores from the Milky Way. This may indicate that the electron-to-proton mass ratio, mu = m_e/m_p, increases by 3x10^{-8} when measured under interstellar conditions with matter densities of more than 10 orders of magnitude lower as compared with laboratory (terrestrial) environments. We now map four molecular cores L1498, L1512, L1517, and L1400K selected from our previous sample in order to estimate systematic effects in Delta V due to possible velocity gradients. We find that in two cores L1498 and L1512 the NH3(1,1) and HC3N(2-1) transitions closely trace the same material and show an offset of Delta V = 26.9 +/- 1.2_stat +/- 3.0_sys m/s throughout the entire clouds. The measured velocity offset, being expressed in terms of Delta mu = (mu_obs - mu_lab)/mu_lab, gives Delta mu = (26 +/- 1_stat +/- 3_sys)x10^{-9}.