Andromeda IV Is A Solitary Gas-Rich Dwarf Galaxy

Andromeda IV is often referred to as an irregular satellite of the Andromeda galaxy, which is also known as also known as Messier 31. However, a team of international researchers found that Andromeda IV is actually a gas-abundant solitary irregular dwarf galaxy, according to a study. The researchers made their observations using the Advanced Camera for Surveys (ACS) on the Hubble Space Telescope.

The researchers were able to measure the galaxy's distance and its surface brightness based on the information that was gathered in their observations. They found that Andromeda IV is located at a distance of 22 to 24 million light years away and the galaxy has total blue absolute magnitude of -12.81 mag.

"To measure total galaxy magnitude in each band, the galaxy image was first fitted with concentric ellipses," the researchers wrote in a report. "Then integrated photometry was performed in these ellipses with parameters defined from the center to the faint outskirts. The total magnitude was then estimated as the asymptotic value of the radial growth curve."

They claimed that the galaxy was modeled as consisting of three components, a gas disk, a stellar disk  and dark matter halo. The team detected a large amount of neutral hydrogen, which is a moderate activity that is associated with star formation and a low metallicity at Andromeda IV. The researchers claimed that these are features isolated dwarf irregular galaxies and these types of gas dominated objects must be in their initial stages of their evolution.

"The galaxies with high gas-to-stellar mass ratio are usually isolated objects, with a low optical surface brightness and low metallicity," the researchers wrote.

The findings of this study were published in ArXiv.

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