MUSE Analysis of Gas around Galaxies (MAGG)

We present a novel dataset that extends our view of the cosmic gas around z ≈ 3 − 4 Lyα emitters (LAEs) in the Muse Analysis of Gas around Galaxies (MAGG) survey by tracing a cool and enriched gas phase through 47 Mg <ns0:sc>II</ns0:sc> absorbers identified in newly obtained VLT/X-shooter near-infrared quasar spectra. Jointly with the more ionized gas traced by C <ns0:sc>IV</ns0:sc> systems and the neutral H <ns0:sc>I</ns0:sc> from previous work, we find that LAEs are distributed inside cosmic structures that contain multiphase gas in composition and temperature. All gas phases are a strong function of the large-scale galaxy environment: the Mg <ns0:sc>II</ns0:sc> and the C <ns0:sc>IV</ns0:sc> strength and kinematics positively correlate with the number of associated galaxies, and it is ≈3 − 4 times more likely to detect metal absorbers around groups of LAEs than isolated ones. Exploring the redshift evolution, the covering factor of Mg <ns0:sc>II</ns0:sc> around groups of LAEs and isolated ones remains approximately constant from z ≈ 3 − 4 to z ≲ 2, but the one of C <ns0:sc>IV</ns0:sc> around group galaxies drops by z ≲ 2. Adding the cool enriched gas traced by the Mg <ns0:sc>II</ns0:sc> absorbers to the results that we obtained for the H <ns0:sc>I</ns0:sc> and C <ns0:sc>IV</ns0:sc> gas, we put forward a picture in which LAEs lie along gas filaments that contain high column-density H <ns0:sc>I</ns0:sc> systems and are enriched by strong C <ns0:sc>IV</ns0:sc> and Mg <ns0:sc>II</ns0:sc> absorbers. While the Mg <ns0:sc>II</ns0:sc> gas appears to be more centrally concentrated near LAEs, weaker C <ns0:sc>IV</ns0:sc> systems instead trace a more diffuse gas phase extended up to larger distances around the galaxies.