Tidal bridge and tidal dwarf candidates in the interacting system Arp194

TL;DR

This study investigates the kinematics, chemical composition, and star formation in the interacting galaxy system Arp194, identifying a tidal dwarf galaxy and analyzing the properties of the tidal bridge between the galaxies.

Contribution

The paper provides detailed spectroscopic analysis of Arp194, confirming the tidal dwarf nature of region A and revealing the chemical and kinematic properties of the tidal bridge.

Findings

Region A is a gravitationally bound tidal dwarf galaxy.

The gas in the bridge shows partial chemical mixing and an O/H gradient.

Velocity dispersion varies, indicating disturbed regions in the system.

Abstract

Arp194 is a system of recently collided galaxies, where the southern galaxy (S) passed through the gaseous disc of the northern galaxy (N) which in turn consists of two close components. This system is of special interest due to the presence of regions of active star-formation in the bridge between galaxies, the brightest of which (the region A) has a size of at least 4 kpc. We obtained three spectral slices of the system for different slit positions at the 6-m telescope of SAO RAS. We estimated the radial distribution of line-of-sight velocity and velocity dispersion as well as the intensities of emission lines and oxygen abundance $12+\log(\mathrm{O/H})$. The gas in the bridge is only partially mixed chemically and spatially: we observe the O/H gradient with the galactocentric distances both from S and N galaxies and a high dispersion of O/H in the outskirts of N-galaxy. Velocity dispersion of the emission-line gas is the lowest in the star-forming sites of the bridge and exceeds 50-70 km/s in the disturbed region of N-galaxy. Based on the SDSS photometrical data and our kinematical profiles we measured the masses of stellar population and the dynamical masses of individual objects. We confirm that the region A is the gravitationally bound tidal dwarf with the age of $10^7 - 10^8 $ yr, which is falling onto the parent S- galaxy. There is no evidence of the significant amount of dark matter in this dwarf galaxy.