A NICMOS search for obscured supernovae in starburst galaxies^*

¹ Max-Planck-Institut für Extraterrestrische Physik, Postfach 1312, 85741 Garching, Germany e-mail: gcresci@mpe.mpg.de
² INAF, Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, 50125 Firenze, Italy
³ Istituto di Radioastronomia, INAF, Largo E. Fermi 5, 50125 Firenze, Italy
⁴ Kavli Institute for Theoretical Physics University of California Santa Barbara, CA 93106, USA

Received: 5 April 2006
Accepted: 19 October 2006

Abstract

The detection of obscured supernovae (SNe) in near-infrared monitoring campaigns of starburst galaxies has shown that a significant fraction of SNe is missed by optical surveys. However, the number of SNe detected in ground-based near-IR observations is still significantly lower than the number of SNe extrapolated from the FIR luminosity of the hosts. A possibility is that most SNe occur within the nuclear regions, where the limited angular resolution of ground-based observations prevents their detection. This issue prompted us to exploit the superior angular resolution of NICMOS-HST to search for obscured SNe within the first kpc from the nucleus of strong starbursting galaxies. A total of 17 galaxies were observed in SNAPSHOT mode. Based on their FIR luminosity, we did not expect to detect fewer than ~ SNe. However, no confirmed SN event was found. From our data we derived an observed nuclear SN rate <0.5 SN/yr per galaxy. The shortage of SN detections can be explained by a combination of several effects. The most important are: i) the existence of a strong extinction, ; ii) most SNe occur within the first (which corresponds in our sample to about 500 pc) where even NICMOS is unable to detect SN events.