HII regions within a compact high velocity cloud. A nearly star-less dwarf galaxy?

TL;DR

This study reports the discovery of a nearly star-less dwarf galaxy, SECCO-1, with an exceptionally high neutral hydrogen to luminosity ratio, potentially linking normal dwarfs and dark mini halos in the Local Group.

Contribution

The paper presents the identification of a new faint dwarf galaxy with extreme properties, possibly representing a missing link in galaxy formation models.

Findings

Discovery of a candidate dwarf galaxy SECCO-1 in the Virgo cluster.

SECCO-1 has an unusually high M_{HI}/L_V ratio, indicating it is nearly star-less.

Spectroscopic data suggest a possible association with an ultra-compact high velocity cloud.

Abstract

Within the SECCO survey we identified a candidate stellar counterpart to the Ultra Compact High Velocity Cloud (UCHVC) HVC274.68+74.70-123, that was suggested by Adams et al. (2013) as a possible mini-halo within the Local Group of galaxies. The spectroscopic follow-up of the brightest sources within the candidate reveals the presence of two HII regions whose radial velocity is compatible with physical association with the UVHVC. The available data does not allow us to give a definite answer on the nature of the newly identified system. A few alternative hypotheses are discussed. However, the most likely possibility is that we have found a new faint dwarf galaxy residing in the Virgo cluster of galaxies, which we name SECCO-1. Independently of its actual distance, SECCO-1 displays a ratio of neutral hydrogen mass to V luminosity of M_{HI}/L_V>= 20, by far the largest among local dwarfs. Hence, it appears as a nearly star-less galaxy and it may be an example of the missing links between normal dwarfs and the dark mini halos that are predicted to exist in large numbers according to the currently accepted cosmological model.