SINFONI spectra of heavily obscured AGNs in COSMOS: evidence of outflows in a MIR/O target at z$\sim2.5$

TL;DR

This study uses SINFONI VLT spectroscopy to analyze four heavily obscured AGNs at z~1-2.5, revealing outflows in one and suggesting these galaxies are in a transitional evolutionary phase.

Contribution

First detailed near-infrared spectroscopic analysis of obscured AGNs in COSMOS, identifying outflows and providing insights into their evolutionary stage.

Findings

Detected a fast, extended outflow in one AGN via [OIII] emission.

Confirmed all four sources host obscured AGNs.

Suggested these galaxies are in a transitional phase between starburst and QSO.

Abstract

We present new data for four candidate obscured Compton-Thick (CT) quasars at z $\sim$1-2.5 observed with SINFONI VLT spectrograph in AO mode. These sources were selected from a 24$\mu$m Spitzer MIPS survey of the COSMOS field, on the basis of red mid-infrared-to-optical and optical-to-near-infrared colours, with the intention of identifying active galactic nuclei (AGNs) in dust enshrouded environments, where most of the black hole mass is assembled in dust enshrouded environments. Near infrared spectra were analyzed in order to check for emission line features and to search for broad components in the [OIII]-H$\beta$ and H$\alpha$-[NII] regions. X-ray spectral analysis, radio and MIR diagnostics, and SED fitting have also been employed to study the nature of the sources. We successfully identified three objects for which we had only a photometric redshift estimate. Based on their emission line diagnostics and on ancillary multi-wavelength constraints, we find that all four targets harbor obscured AGNs. Broad profiles that could be attributed to the effects of outflows are revealed in only one target, MIRO20581. In particular, we clearly resolved a fast ($\sim$1600 km/s) and extended ($\sim$5 kpc) outflow in the [OIII]5007 emission line. This feature, the commonly used indicator for ionised outflowing gas, was sampled and detected only for this target; hence, we can not exclude the presence of outflows in the other sources. Overall, the constraints we obtain from our targets and from other comparative samples from the literature suggest that these optically faint luminous infrared galaxies, hosting obscured AGNs, may represent a brief evolutionary phase between the post-merger starburst and the unobscured QSO phases.