Circumgalactic Ly<b><i>α</i></b> emission around submillimeter-bright galaxies with different quasar contributions
Vale González Lobos, Fabrizio Arrigoni Battaia, Seok-Jun Chang, Max Grönke, Guinevere Kauffmann, Chian-Chou Chen, Hai Fu, Aura Obreja, Emanuele Paolo Farina
Abstract
We present VLT/MUSE observations targeting the extended Lyman- α (Ly α ) emission of five high-redshift ( z ∼ 3-4) submillimeter galaxies (SMGs) with increasing quasi-stellar object (QSO) radiation: two SMGs; two SMGs that host a QSO; and one SMG that hosts a QSO with an SMG companion (QSO+SMG). These sources are predicted to be located in dark matter halos of comparable masses (average mass of M DM ∼ 10 12.2 M ⊙ ). We quantified the luminosity and extent of the Ly α emission, together with its kinematics, and examined four Ly α powering mechanisms: photoionization from QSOs or star formation, shocks by galactic and/or QSO outflows, gravitational cooling radiation, and Ly α photon resonant scattering. We find a variety of Ly α luminosities and extents, with the QSO+SMG system displaying the most extended and bright nebula, followed by the SMGs hosting a QSO, and finally the undetected circumgalactic medium of SMGs. This diversity implies that gravitational cooling is unlikely to be the main powering mechanism. We show that photoionization from the QSO and QSO outflows can contribute to power the emission for average densities n H > 0.5 cm −3 . Moreover, the observed Ly α luminosities scale with the QSO’s budget of Ly α photons modulo the dust content in each galaxy, highlighting a possible contribution from resonant scattering of QSO radiation in powering the nebulae. We find larger Ly α linewidths ( FWHM ≳ 1200 km s −1 ) than usually reported around radio-quiet systems, pointing to large-scale outflows. A statistical survey targeting similar high-redshift massive systems with known host properties is needed to confirm our findings.