The circumnuclear environment of the peculiar galaxy NGC3310

Abstract

Gas and star velocity dispersions have been derived for eight circumnuclear star-forming regions (CNSFRs) and the nucleus of the spiral galaxy NGC3310 using high-resolution spectroscopy in the blue and far red. Stellar velocity dispersions have been obtained from the CaII triplet in the near-IR, using cross-correlation techniques, while gas velocity dispersions have been measured by Gaussian fits to the Hβλ4861Å and [OIII]λ5007Å emission lines.

The CNSFR stellar velocity dispersions range from 31 to 73kms^-1. These values, together with the sizes measured on archival Hubble Space Telescope images, yield upper limits to the dynamical masses for the individual star clusters between 1.8 and 7.1 × 10⁶M_solar, for the whole CNSFR between 2 × 10⁷ and 1.4 × 10⁸M_solar, and 5.3 × 10⁷M_solar, for the nucleus inside the inner 14.2pc. The masses of the ionizing stellar population responsible for the HII region gaseous emission have been derived from their published Hα luminosities and are found to be between 8.7 × 10⁵ and 2.1 × 10⁶M_solar for the star-forming regions and 2.1 × 10⁵M_solar for the galaxy nucleus; they therefore constitute between 1 and 7 per cent of the total dynamical mass.

The ionized gas kinematics is complex; two different kinematical components seem to be present as evidenced by different linewidths and Doppler shifts.