On the derivation of dynamical masses of the stellar clusters in the circumnuclear region of NGC2903

TL;DR

This study measures stellar and gas velocity dispersions in the circumnuclear star-forming regions of NGC2903 to estimate the dynamical masses of individual clusters and the entire region, revealing complex substructures.

Contribution

It provides new dynamical mass estimates for star clusters and CNSFRs in NGC2903 using high-resolution spectroscopy and HST imaging, highlighting their complex substructure.

Findings

Stellar velocity dispersions range from 39 to 67 km/s.

Dynamical masses of clusters are between 1.8 and 8.7 million solar masses.

CNSFRs contain multiple subclusters with sizes of 3 to 8 parsecs.

Abstract

(Abridged) Gas and star velocity dispersions have been derived for four circumnuclear star-forming regions (CNSFRs) and the nucleus of the spiral galaxy NGC2903 using high resolution spectroscopy in the blue and far red. Stellar velocity dispersions have been obtained from the CaII triplet (CaT) lines at 8494, 8542, 8662A, using cross-correlation techniques while gas velocity dispersions have been measured by Gaussian fits to the Hbeta line. The CNSFRs, with sizes of about 100 to 150pc in diameter, show a complex structure at the Hubble Space Telescope resolution, with a good number of subclusters with linear diameters between 3 and 8pc. Their stellar velocity dispersions range from 39 to 67 km/s. These values, together with the sizes measured on archival HST images yield upper limits to the dynamical masses for the individual star clusters between 1.8 and 8.7 x 10$^6$ M$_\odot$ and upper limits to the masses for the whole CNSFR between 4.9 x 10$^6$ and 4.3 x 10$^7$ M$_\odot$. ...