Optical detection of the radio supernova SN 2000ft in the circumnuclear region of the luminous infrared galaxy NGC 7469^*

¹ Instituto de Estructura de la Materia (CSIC-IEM), Serrano 121, 28006 Madrid, Spain e-mail: [colina;tanio;aalonso]@damir.iem.csic.es
² Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA
³ Istituto Nazionale di Astrofisica (INAF), Via del Parco Mellini 84, 00136 Rome, Italy
⁴ Supernova Ltd., OYV #131, Northsound Road, Virgin Gorda, British Virgin Islands e-mail: panagia@stsci.edu
⁵ Instituto de Astrofísica de Andalucia, CSIC-IAA, Apartado 3004, 18080 Granada, Spain e-mail: antxon@iaa.es
⁶ Instituto de Ciencias del Espacio (CSIC)-IEEC, Facultat de Física, Planta 7a, Universitat de Barcelona, Av. Diagonal 647, 08028 Barcelona, Spain e-mail: torrelles@ieec.fcr.es
⁷ Department of Astronomy, University of Maryland, College Park, MD 20742, USA e-mail: wilson@astro.umd.edu

Received: 29 December 2006
Accepted: 5 March 2007

Abstract

Context.(Ultra)Luminous Infrared Galaxies (ULIRGs) produce massive stars in large quantities in their central starburst regions. The expected rate of supernova explosions is, on average, about one per year. Detection of these supernovae in the expected numbers has proven elusive so far.

Aims.Illustrate the general benefits and limitations of supernova searches in (U)LIRGs in the optical using the previously detected luminous type II radio supernova SN 2000ft in NGC 7469 as a study case.

Methods.Multi-epoch Hubble Space Telescope (HST) optical imaging at different wavelengths and two dimensional PSF fitting algorithms are used to search, and characterize, the optical emission of SN 2000ft.

Results.SN 2000ft is detected in two independent Planetary Camera images (F547W and F814W) taken May 13, 2000, about two months before the predicted date of the explosion (July 19, 2000), based on the analysis of its radio light evolution by Alberdi and collaborators. The apparent optical magnitudes and red color of SN 2000ft indicate that it is observed through an extinction of at least  mag. The extinction corrected lower limit to the absolute visual magnitude (), identifies SN 2000ft as a luminous supernova in the optical, as other luminous radio supernovae before. SN 2000ft exploded in a region located at only 01 (i.e.  pc) west of a faint cluster (C24). No parent cluster is identified within the detection limits of the HST short exposures.

Conclusions.The unambiguous detection of SN 2000ft in the visual shows that multi-epoch sub-arcsecond () optical imaging is also a valid tool that should be explored further to detect supernovae in the dusty (circum)nuclear regions of (U)LIRGs.