The triply-ionized carbon forest from eBOSS: cosmological correlations with quasars in SDSS-IV DR14

Michael Blomqvist, Matthew M. Pieri, Hélion Du Mas Des Bourboux, Nicolás G. Busca, Anže Slosar, Julian E. Bautista, Jonathan Brinkmann, Joel R. Brownstein, Kyle Dawson, Victoria De Sainte Agathe, Julien Guy, Will J. Percival, Ignasi Pérez-ràfols, James Rich, Donald P. Schneider

Research output: Contribution to journalArticlepeer-review

75 Downloads (Pure)


We present measurements of the cross-correlation of the triply-ionized carbon (CIV) forest with quasars using Sloan Digital Sky Survey Data Release 14. The study exploits a large sample of new quasars from the first two years of observations by the Extended Baryon Oscillation Spectroscopic Survey (eBOSS). The CIV forest is a weaker tracer of large-scale structure than the Lyα forest, but benefits from being accessible at redshifts z<2 where the quasar number density from eBOSS is high. Our data sample consists of 287,651 CIV forest quasars in the redshift range 1.4<z<3.5 and 387,315 tracer quasars with 1.2<z<3.5. We measure large-scale correlations from CIV absorption occuring in three distinct quasar rest-frame wavelength bands of the spectra referred to as the CIV forest, the SiIV forest and the Lyα forest. From the combined fit to the quasar-CIV cross-correlations for the CIV forest and the SiIV forest, the CIV redshift-space distortion parameter is βCIV=0.27 −0.14 −0.26 +0.16 +0.34 and its combination with the CIV linear transmission bias parameter is bCIV(1+βCIV)=−0.0183 −0.0014 −0.0029 +0.0013 +0.0025 (1σ and 2σ statistical errors) at the mean redshift z=2.00. Splitting the sample at z=2.2 to constrain the bias evolution with redshift yields the power-law exponent γ=0.60±0.63, indicating a significantly weaker redshift-evolution than for the Lyα forest linear transmission bias. Additionally, we demonstrate that CIV absorption has the potential to be used as a probe of baryon acoustic oscillations (BAO). While the current data set is insufficient for a detection of the BAO peak feature, the final quasar samples for redshifts 1.4<z<2.2 from eBOSS and the Dark Energy Spectroscopic Instrument (DESI) are expected to provide measurements of the isotropic BAO scale to ~7% and ~3% precision, respectively, at zsime1.6.
Original languageEnglish
Article number029
JournalJournal of Cosmology and Astroparticle Physics
Issue number05
Publication statusPublished - 8 May 2018


Dive into the research topics of 'The triply-ionized carbon forest from eBOSS: cosmological correlations with quasars in SDSS-IV DR14'. Together they form a unique fingerprint.

Cite this