UGC 7639: a Dwarf Galaxy in the Canes Venatici I Cloud

TL;DR

This study combines multi-wavelength observations and SPH simulations to analyze the formation, evolution, and future of the dwarf galaxy UGC 7639 in the Canes Venatici I Cloud, revealing its recent star formation and predicted transition to a red dwarf.

Contribution

It presents a novel integrated approach using archival data and simulations to understand the evolution of blue dwarf galaxies like UGC 7639.

Findings

UGC 7639's properties match a past encounter with a more massive system.

Current star formation rate is about 0.03 M_sun/yr, consistent with UV estimates.

The galaxy is estimated to be 8.6 Gyr old and will become a red dwarf in 1.6 Gyr.

Abstract

We want to get insight into the nature, i.e. the formation mechanism and the evolution, of UGC 7639, a dwarf galaxy in the Canes Venatici I Cloud (CVnIC). We used archival GALEX (FUV and NUV) and SDSS images, as well as Hyperleda and NED databases, to constrain its global properties. GALEX FUV/NUV images show that UGC 7639 inner regions are composed mostly by young stellar populations. In addition, we used smoothed particle hydrodynamics (SPH) simulations with chemo-photometric implementation to account for its formation and evolution. UGC 7639 is an example of blue dwarf galaxy whose global properties are well matched by our multi-wavelength and multi-technique approach, that is also a suitable approach to highlight the evolution of these galaxies as a class. We found that the global properties of UGC 7639, namely its total absolute B-band magnitude, its whole spectral energy distribution (SED), and its morphology are well-matched by an encounter with a system four times more massive than our target. Moreover, the current star formation rate (SFR) of the simulated dwarf, ~0.03 M_sun yr-1, is in good agreement with our UV-based estimate. For UGC 7639, we estimated a galaxy age of 8.6 Gyr. Following our simulation, the ongoing star formation will extinguish within 1.6 Gyr, thus leaving a red dwarf galaxy.