Evidence of nuclear disks in starburst galaxies from their radial
  distribution of supernovae
  Galaxy-galaxy interactions are expected to be responsible for triggering
massive star formation and possibly accretion onto a supermassive black hole,
by providing large amounts of dense molecular gas down to the central
kiloparsec region. Several scenarios to drive the gas further down to the
central ~100 pc, have been proposed, including the formation of a nuclear disk
around the black hole, where massive stars would produce supernovae. Here, we
probe the radial distribution of supernovae and supernova remnants in the
nuclear regions of the starburst galaxies M82, Arp 299-A, and Arp 220, by using
high-angular resolution (< 0."1) radio observations published in the literature
(for M82 and Arp 220), or obtained by ourselves from the European VLBI Network
(Arp 299-A). Our main goal was to characterize the nuclear starbursts in those
galaxies and thus test scenarios that propose that nuclear disks of sizes ~100
pc form in the central regions of starburst galaxies. We obtained the radial
distribution of supernovae (SNe) in the nuclear starbursts of M82, Arp 299-A,
and Arp 220, and derived scale-length values for the putative nuclear disks
powering the bursts in those central regions. The scale lengths for the
(exponential) disks range from ~20-30 pc for Arp 299-A and Arp 220, up to ~140
pc for M82. The radial distribution of SNe for the nuclear disks in Arp 299-A
and Arp 220 is also consistent with a power-law surface density profile of
exponent gamma=1, as expected from detailed hydrodynamical simulations of
nuclear disks. Our results support scenarios where a nuclear disk of size ~100
pc is formed in (U)LIRGs, and sustained by gas pressure, in which case the
accretion onto the black hole could be lowered by supernova feedback.
