Properties of the ionized gas of circumnuclear star-forming regions in early type spirals

TL;DR

This study investigates the properties of circumnuclear star-forming regions in early type spirals, focusing on their kinematics, masses, and chemical abundances using high and moderate resolution spectroscopy.

Contribution

It provides detailed measurements of stellar and gas kinematics, chemical abundances, and dynamical masses of CNSFRs, revealing their complex structure and properties.

Findings

CNSFRs are composed of several star clusters with sizes 1.5-4.9 pc.

Stellar and gas velocity dispersions differ by 20-30 km/s.

Dynamical masses of CNSFRs are around 10^7 to 10^8 solar masses.

Abstract

(Abbr.) A study of cicumnuclear star-forming regions (CNSFRs) in several early type spirals has been made in order to investigate their main properties: stellar and gas kinematics, dynamical masses, ionising stellar masses, chemical abundances and other properties of the ionised gas. Both high resolution (R$ \sim $20000) and moderate resolution (R ~ 5000) have been used. In some cases these regions, about 100 to 150 pc in size, are seen to be composed of several individual star clusters with sizes between 1.5 and 4.9 pc estimated from Hubble Space Telescope (HST) images. Stellar and gas velocity dispersions are found to differ by about 20 to 30 km/s with the H$\beta$ emission lines being narrower than both the stellar lines and the [OIII] $\lambda$ 5007 \AA lines. The twice ionized oxygen, on the other hand, shows velocity dispersions comparable to those shown by stars. We have applied the virial theorem to estimate dynamical masses of the clusters, assuming that systems are gravitationally bounded and spherically symmetric, and using previously measured sizes. The measured values of the stellar velocity dispersions yield dynamical masses of the order of 10$^7$ to 10$^8$ solar masses for the whole CNSFRs. ...