The VIMOS Public Extragalactic Redshift Survey (VIPERS)

AGN feedback in [NeV] emitters^⋆

¹ INAF – Osservatorio di Astrofisica e Scienza dello Spazio, Via P. Gobetti 93/3, 40129 Bologna, Italy
e-mail: daniela.vergani@inaf.it
² INAF – Istituto di Astrofisica Spaziale e Fisica Cosmica Milano, Via E. Bassini 15, 20133 Milano, Italy
³ Aix-Marseille Université, Jardin du Pharo, 58 bd Charles Livon, 13284 Marseille Cedex 7, France
⁴ IRAP, 9 av. du colonel Roche, BP 44346, 31028 Toulouse Cedex 4, France
⁵ INAF – Osservatorio Astronomico di Brera, Via Brera 28, 20122 Milano – via E. Bianchi 46, 23807 Merate, Italy
⁶ Università degli Studi di Milano, Via G. Celoria 16, 20133 Milano, Italy
⁷ Aix–Marseille Univ., CNRS, LAM, Laboratoire d’Astrophysique de Marseille, Marseille, France
⁸ INAF – Osservatorio Astrofisico di Torino, 10025 Pino Torinese, Italy
⁹ Laboratoire Lagrange, UMR7293, Université de Nice Sophia Antipolis, CNRS, Observatoire de la Côte d’Azur, 06300 Nice, France
¹⁰ Dipartimento di Fisica e Astronomia – Alma Mater Studiorum Università di Bologna, Via P. Gobetti 93/2, 40129 Bologna, Italy
¹¹ INAF – Osservatorio Astronomico di Trieste, Via G. B. Tiepolo 11, 34143 Trieste, Italy
¹² Institute of Physics, Jan Kochanowski University, ul. Swietokrzyska 15, 25-406 Kielce, Poland
¹³ National Centre for Nuclear Research, ul. Hoza 69, 00-681 Warszawa, Poland
¹⁴ INFN, Sezione di Bologna, Viale Berti Pichat 6/2, 40127 Bologna, Italy
¹⁵ Astronomical Observatory of the Jagiellonian University, Orla 171, 30-001 Cracow, Poland
¹⁶ School of Physics and Astronomy, University of St Andrews, St Andrews KY16 9SS UK
¹⁷ INAF – Istituto di Radioastronomia, Via P. Gobetti 101, 40129 Bologna, Italy
¹⁸ Aix–Marseille Univ., Univ. Toulon, CNRS, CPT, Marseille, France
¹⁹ Dipartimento di Matematica e Fisica, Università degli Studi Roma Tre, Via della Vasca Navale 84, 00146 Roma, Italy
²⁰ INFN, Sezione di Roma Tre, Via della Vasca Navale 84, 00146 Roma, Italy
²¹ INAF – Osservatorio Astronomico di Roma, Via Frascati 33, 00040 Monte Porzio Catone, RM, Italy
²² Department of Astronomy, University of Geneva, ch. d’Ecogia 16, 1290 Versoix, Switzerland
²³ Department of Astronomy & Physics, Saint Mary’s University, 923 Robie Street, Halifax, Nova Scotia B3H 3C3, Canada

Received: 19 December 2017
Accepted: 18 October 2018

Abstract

Aims. We analyse the properties of the host galaxies of a [NeV]-selected sample to investigate whether and how they are affected by the AGN.

Methods. We have selected a sample of galaxies at 0.62 <  z <  1.2 from the VIMOS Public Extragalactic Redshift Survey (VIPERS) and divided it in blue cloud galaxies, red passive galaxies and green valley galaxies using the NUVrK diagram. Within each category, galaxies with AGN activity were identified based on the detection of the high-ionisation [NeV]λ3426 emission line. For each galaxy we derived several properties (stellar age and mass, the (r−K) colour, the [OII] luminosity) and compared them between active and inactive galaxies matched in stellar mass and redshift.

Results. We find statistically significant differences in the properties between active and inactive galaxies. These differences imply that the AGN is more often found in galaxies with younger stellar populations and more recent star-forming activity than their parent samples. Interestingly, the AGN identified through the [NeV]λ3426 emission line is not commonly found by traditional AGN-selection techniques based on shallow X-ray data, mid-IR colours, and classical line diagnostic diagrams, and might thus reveal a specific evolutionary phase. The spectral analysis reveals a sub-set of AGN within the blue cloud that has spectral signatures implying a sudden suppression of star formation activity similar to post-starburst galaxies.

Conclusion. Using the rich dataset of the large VIPERS sample we identify a novel class of active post-starburst galaxies that would be missed by traditional selection techniques. These galaxies belong to the blue cloud, but their star-formation activity has been recently suppressed, possibly by the AGN identified through the presence of the [NeV]λ3426 emission line in their spectra. Our results support the idea that AGN feedback may be responsible for halting star-formation in active blue galaxies and for their transition into the red sequence, at least in the 0.6–1.2 redshift range and for stellar masses greater than 5 × 10¹⁰ ℳ_⊙. Our results are based on a complete spectroscopic sample and limited by the [NeV] observability, and the AGN can be variable and with a relatively short duty cycle. Considering this, AGN feedback that makes blue galaxies quickly transition to the red sequence may be even more common than previously believed.