Fundamental physics with ESPRESSO: Precise limit on variations in the fine-structure constant towards the bright quasar HE 0515−4414

Murphy, Michael T.; Molaro, Paolo; Leite, Ana C. O.; Cupani, Guido; Cristiani, Stefano; D'Odorico, Valentina; Génova Santos, Ricardo; Martins, Carlos J. A. P.; Milaković, Dinko; Nunes, Nelson J.; Schmidt, Tobias M.; Pepe, Francesco A.; Rebolo, Rafael; Santos, Nuno C.; Sousa, Sérgio G.; Zapatero Osorio, Maria-Rosa; Amate, Manuel; Adibekyan, Vardan; Alibert, Yann; Allende Prieto, Carlos; Baldini, Veronica; Benz, Willy; Bouchy, François; Cabral, Alexandre; Dekker, Hans; Di Marcantonio, Paolo; Ehrenreich, David; Figueira, Pedro; González Hernández, Jonay I.; Landoni, Marco; Lovis, Christophe; Lo Curto, Gaspare; Manescau, Antonio; Mégevand, Denis; Mehner, Andrea; Micela, Giuseppina; Pasquini, Luca; Poretti, Ennio; Riva, Marco; Sozzetti, Alessandro; Suarez Mascareño, Alejandro; Udry, Stéphane; Zerbi, Filippo
Bibliographical reference

Astronomy and Astrophysics

Advertised on:
2
2022
Number of authors
43
IAC number of authors
6
Citations
33
Refereed citations
25
Description
The strong intervening absorption system at redshift 1.15 towards the very bright quasar HE 0515−4414 is the most studied absorber for measuring possible cosmological variations in the fine-structure constant, α. We observed HE 0515−4414 for 16.1 h with the Very Large Telescope and present here the first constraint on relative variations in α with parts-per-million (ppm) precision from the new ESPRESSO spectrograph: Δα/α = 1.3 ± 1.3stat ± 0.4sys ppm. The statistical uncertainty (1σ) is similar to the ensemble precision of previous large samples of absorbers and derives from the high signal-to-noise ratio achieved (≈105 per 0.4 km s−1 pixel). ESPRESSO's design, and the calibration of our observations with its laser frequency comb, effectively removed wavelength calibration errors from our measurement. The high resolving power of our ESPRESSO spectrum (R = 145 000) enabled the identification of very narrow components within the absorption profile, allowing a more robust analysis of Δα/α. The evidence for the narrow components is corroborated by their correspondence with previously detected molecular hydrogen and neutral carbon. The main remaining systematic errors arise from ambiguities in the absorption profile modelling, effects from redispersing the individual quasar exposures, and convergence of the parameter estimation algorithm. All analyses of the spectrum, including systematic error estimates, were initially blinded to avoid human biases. We make our reduced ESPRESSO spectrum of HE 0515−4414 publicly available for further analysis. Combining our ESPRESSO result with 28 measurements, from other spectrographs, in which wavelength calibration errors have been mitigated yields a weighted mean Δα/α = −0.5 ± 0.5stat ± 0.4sys ppm at redshifts 0.6−2.4.

Based on Guaranteed Time Observations collected at the European Southern Observatory under ESO programme 1102.A-0852 by the ESPRESSO Consortium.

Based on Guaranteed Time Observations collected at the European Southern Observatory under ESO programme 1102.A-0852 by the ESPRESSO Consortium.

The data and analysis products from this work are publicly available at https://doi.org/10.5281/zenodo.5512490 (<xref ref-type="bibr" rid="R57">Murphy et al. 2021</xref>).
Related projects
Full-sky map showing the spatial distribution of the primary anisotropies of the Cosmic Microwave Background (generated 380,000 years after the Big Bang) derived from observations of the Planck satellite
Anisotropy of the Cosmic Microwave Background

The general goal of this project is to determine and characterize the spatial and spectral variations in the temperature and polarisation of the Cosmic Microwave Background in angular scales from several arcminutes to several degrees. The primordial matter density fluctuations which originated the structure in the matter distribution of the present

Rafael
Rebolo López
spectrum of mercury lamp
Chemical Abundances in Stars

Stellar spectroscopy allows us to determine the properties and chemical compositions of stars. From this information for stars of different ages in the Milky Way, it is possible to reconstruct the chemical evolution of the Galaxy, as well as the origin of the elements heavier than boron, created mainly in stellar interiors. It is also possible to

Carlos
Allende Prieto