MUSEQuBES: Calibrating the redshifts of Ly α emitters using stacked circumgalactic medium absorption profiles

Sowgat Muzahid; Joop Schaye; Raffaella Anna Marino; Sebastiano Cantalupo; Jarle Brinchmann; Thierry Contini; Martin Wendt; Lutz Wisotzki; Johannes Zabl; Nicolas Bouché; Mohammad Akhlaghi; Hsiao-Wen Chen; Adélaide Claeyssens; Sean Johnson; Floriane Leclercq; Michael Maseda; Jorryt Matthee; Johan Richard; Tanya Urrutia; Anne Verhamme

doi:10.1093/mnras/staa1347

paper

MUSEQuBES: Calibrating the redshifts of Ly α emitters using stacked circumgalactic medium absorption profiles

arXiv:1910.03593 · doi:10.1093/mnras/staa1347

Abstract

Lyman $- α$ (Ly $α$ ) emission lines are typically found to be redshifted with respect to the systemic redshifts of galaxies, likely due to resonant scattering of Ly $α$ photons. Here we measure the average velocity offset for a sample of 96 $z \approx 3.3$ Ly $α$ emitters (LAEs) with a median Ly $α$ flux (luminosity) of $\approx 1 0^{- 17} erg c m^{- 2} s^{- 1}$ ( $\approx 1 0^{42} erg s^{- 1}$ ) and a median star formation rate (SFR) of $\approx 1.3 M_{⊙} y r^{- 1}$ (not corrected for possible dust extinction), detected by the Multi-Unit Spectroscopic Explorer as part of our MUSEQuBES circumgalactic medium (CGM) survey. By postulating that the stacked CGM absorption profiles of these LAEs, probed by 8 background quasars, must be centered on the systemic redshift, we measure an average velocity offset, V $_{offset} = 171 \pm 8$ $km s^{- 1}$ , between the Ly $α$ emission peak and the systemic redshift. The observed V $_{offset}$ is lower by factors of $\approx 1.4$ and $\approx 2.6$ compared to the velocity offsets measured for narrow-band selected LAEs and Lyman break galaxies, respectively, which probe galaxies with higher masses and SFRs. Consistent with earlier studies based on direct measurements for individual objects, we find that the V $_{offset}$ is correlated with the full width at half-maximum of the red peak of the Ly $α$ line, and anti-correlated with the rest-frame equivalent width. Moreover, we find that $V_{offset}$ is correlated with SFR with a sub-linear scaling relation, V $_{offset} \propto SF R^{0.16 \pm 0.03}$ . Adopting the mass scaling for main sequence galaxies, such a relation suggests that V $_{offset}$ scales with the circular velocity of the dark matter halos hosting the LAEs.

arXiv commentPublished on 15 May, 2020 along with an erratum (Ref: MNRAS 498, 4424, 2020, doi:10.1093/mnras/staa2668), since Fig. 2 has not been updated in the published version. There are other typos in the published version, introduced by the typesetter, which cannot be revised in the erratum. We feel that the astrp-ph version is more accurate than the published one

MUSEQuBES: Calibrating the redshifts of Ly α emitters using stacked circumgalactic medium absorption profiles

Abstract

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