Abstract
ABSTRACTQuasar outflows might either quench (negative) or enhance (positive feedback) star formation in galaxies located in the quasar environment. The possible outcome depend on 4 parameters: The quasar (σ) and satellite (σ*) halo velocity dispersion, their relative distance, d, and satellite disc radius, rd. We find that: (i) small satellites with $\sigma _* \lt 164\ \sigma _{200}^{2/3}\, \rm km\ s^{-1}$ have their star formation quenched; (ii) in larger satellites, star formation, and hence UV/far-infrared (FIR) luminosity, is instead boosted by >80 per cent in a burst with typical duration of 5–10 Myr, if the following positive feedback criterion is met: d/rd < 15(Q/η)1/2σ200, where Q ≈ 1 is the satellite disc Toomre parameter; the disruption parameter (see equation 17) must be η > 1 to prevent complete satellite gas removal. We compare our predictions with ALMA data finding that observed satellites of z ≃ 6 QSOs on average form stars at a 3 × higher rate with respect to field galaxies at the same redshift. Further tests of the model are suggested.
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