The NGC 672 and NGC 784 Galaxy Groups: Evidence for Galaxy Formation and Growth Along a Nearby Dark Matter Filament

TL;DR

This study investigates 14 dwarf irregular galaxies within 10 Mpc, revealing synchronized star formation likely triggered by cold gas accretion along a dark matter filament, providing insights into galaxy formation and growth.

Contribution

It presents detailed multi-band photometry and star formation analysis of nearby dwarf galaxies, proposing cold gas accretion along a filament as a key driver of their synchronized star formation.

Findings

Most galaxies contain both old and young stellar populations.

Recent star formation bursts occurred within the last few tens of Myr.

Star formation appears synchronized across the galaxy group.

Abstract

(Abridged): We present U, B, V, R, I, H-alpha and NUV photometry of 14 galaxies in the very local Universe (within 10 Mpc that are dwarf irregular galaxies (dIrr), are at low redshift (51<v<610 km/s), and appear as a six degree long linear filament.. We examine the star formation (SF) properties of individual objects with the current SF rate (SFR) derived directly from the H-alpha line flux and compare the multi-band photometry with results of galaxy evolution assuming short SF bursts separated by long quiescence periods. Most objects contain at least one "old" stellar population (>1-10 Gyr) and one "young" population (<30 Myr) with the recent SF bursts occurring a few to a few 10s of Myr ago, arguing for synchronicity in star formation in these objects. We propose that the ~synchronous star formation in all objects is caused by the accretion of cold gas from intergalactic space onto dark matter haloes arranged along a filament threading the void where these dwarf galaxies reside and point out this galaxy sample as an ideal target to study hierarchical clustering and galaxy formation among very nearby objects.