Supernova rates from the SUDARE VST-OmegaCAM search

I. Rates per unit volume^⋆,⋆⋆

¹ INAF, Osservatorio Astronomico di Padova, vicolo dell’Osservatorio 5, 35122 Padova, Italy
e-mail: enrico.cappellaro@oapd.inaf.it
² INAF, Osservatorio Astronomico di Capodimonte, Salita Moiariello 16, 80131 Napoli, Italy
³ Departemento de Ciencias Fisicas, Universidad Andres Bello, 037-0134 Santiago, Chile
⁴ Millennium Institute of Astrophysics, Santiago, Chile
⁵ Astrophysics Group, Physics Department, University of the Western Cape, Private Bag X17, 7535 Bellville, Cape Town, South Africa
⁶ INAF–Istituto di Radioastronomia, via Gobetti 101, 40129 Bologna, Italy
⁷ INAF, Osservatorio Astronomico di Catania, via S. Sofia 78, 95123 Catania, Italy
⁸ Dipartimento di Fisica, Universitá Federico II, 80126 Napoli, Italy
⁹ Astrophysics, University of Oxford, Denys Wilkinson Building, Keble Road, Oxford OX1 3RH, UK
¹⁰ Department of Physical Sciences, The Open University, Milton Keynes, MK7 6AA, UK
¹¹ ASI Science Data Center, via del Politecnico snc, 00133 Roma, Italy

Received: 9 June 2015
Accepted: 14 September 2015

Abstract

Aims. We describe the observing strategy, data reduction tools, and early results of a supernova (SN) search project, named SUDARE, conducted with the ESO VST telescope, which is aimed at measuring the rate of the different types of SNe in the redshift range 0.2 < z < 0.8.

Methods. The search was performed in two of the best studied extragalactic fields, CDFS and COSMOS, for which a wealth of ancillary data are available in the literature or in public archives. We developed a pipeline for the data reduction and rapid identification of transients. As a result of the frequent monitoring of the two selected fields, we obtained light curve and colour information for the transients sources that were used to select and classify SNe by means of an especially developed tool. To accurately characterise the surveyed stellar population, we exploit public data and our own observations to measure the galaxy photometric redshifts and rest frame colours.

Results. We obtained a final sample of 117 SNe, most of which are SN Ia (57%) with the remaining ones being core collapse events, of which 44% are type II, 22% type IIn and 34% type Ib/c. To link the transients, we built a catalogue of ~1.3 × 10⁵ galaxies in the redshift range 0 < z ≤ 1, with a limiting magnitude K_AB = 23.5 mag. We measured the SN rate per unit volume for SN Ia and core collapse SNe in different bins of redshifts. The values are consistent with other measurements from the literature.

Conclusions. The dispersion of the rate measurements for SNe-Ia is comparable to the scatter of the theoretical tracks for single degenerate (SD) and double degenerate (DD) binary systems models, therefore it is not possible to disentangle among the two different progenitor scenarios. However, among the three tested models (SD and the two flavours of DD that either have a steep DDC or a wide DDW delay time distribution), the SD appears to give a better fit across the whole redshift range, whereas the DDC better matches the steep rise up to redshift ~1.2. The DDW instead appears to be less favoured. Unlike recent claims, the core collapse SN rate is fully consistent with the prediction that is based on recent estimates of star formation history and standard progenitor mass range.