AGN-enhanced outflows of low-ionization gas in star-forming galaxies at 1.7<z<4.6
| Main Authors: | Talia, Margherita, Brusa, Marcella, Cimatti, Andrea, VUDS team |
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| Format: | info Proceeding Journal |
| Terbitan: |
, 2017
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| Subjects: | |
| Online Access: |
https://zenodo.org/record/838854 |
Daftar Isi:
- To reproduce the properties of galaxies in the local Universe, as well as the scaling relations between host galaxies and black holes properties, many galaxy formation models invoke the presence of fast and energetic winds extending over galaxy scales. These massive gas outflows can be powered either by star-formation (SF) or AGN activity, though the relative dominance and efficiency of the different mechanisms is not yet fully understood. In the last decade much effort has been put in the search for observational evidence of such phenomena, especially at the peak of both SF and AGN activity through cosmic time (1<z<3), in an attempt to explain the rapid quenching of SF and the link between the evolution of AGNs and their host galaxies. Spectroscopy at different wavelengths is the most powerful tool to find and investigate outflows. Blue-shifted inter-stellar medium (ISM) absorption lines in the UV regime, as well as broad, blue-shifted and asymmetric profiles in ionised permitted and forbidden optical emission lines (e.g. [OIII]5007, Hα) have been observed in galaxies at all redshifts and are usually interpreted as evidence of fast material moving towards our line of sight. More recently, especially thanks to new facilities like ALMA, outflows are being observed also in neutral and molecular gas. We collected a large sample of AGNs and SFGs at z>1 from large optical spectroscopic surveys (zCOSMOS, VUDS, ESO public surveys), complemented with HST imaging, X-ray (Chandra) and IR data, and we concentrated our analysis on the ISM absorption lines in the rest-frame UV wavelength range. The analysis of the ISM absorption lines in stacked spectra confirmed that galaxies hosting an AGN show outflows moving at speeds (~600-800 km/s) much faster than in the case of pure SFGs. However, though the AGN might be responsible of an enhanced gas outflow activity with respect to SF alone, the analysis of the sample also shows that there is no correlation between the power of the AGN, as traced by its X-ray luminosity, and the velocity of the warm phase of the outflow traced by the ISM UV absorption lines. This result is at odds with previous findings reported for the highly ionized phase in local AGN, suggesting that the two phases of the outflow are mixed only in relatively low-velocity outflows.