Spectrophotometric study explores an early-type dwarf galaxy

Using the Gemini Observatory, Argentinian astronomers have conducted comprehensive photometric and spectroscopic observations of an early-type dwarf galaxy known as CGCG014-074. Results of the observational campaign, published September 3 in the Monthly Notices of the Royal Astronomical Society, shed more light on the properties and evolution of this galaxy.

In general, dwarf galaxies are low-luminosity and low-mass stellar systems, usually containing a few billion stars. From this group, early-type dwarf galaxies stand out as the dominant galaxy type within the local universe.

CGCG014-074 is an early-type dwarf lenticular galaxy, located in the vicinity of NGC 4546—a massive lenticular galaxy at a distance of about 46 million light years away. Besides heliocentric velocity at a level of 998 km/s, not much is known about the properties of CGCG014-074 as the galaxy remains completely unexplored.

That is why a team of astronomers led by Natalia Guevara of the National University of La Plata in Argentina has employed Gemini Multi-Object Spectrographs (GMOS) at the Gemini South telescope in Chile, in order to perform a comprehensive spectrophotometric study of CGCG014-074.

"This paper presents the photometric and spectroscopic analysis of the early-type dwarf galaxy CGCG014-074. The observations were obtained with the GMOS South instrument of the Gemini Observatory. The photometric data were obtained using the broadband filters 𝑔′, 𝑟′, 𝑖′ and 𝑧′, while the spectroscopic observations were made in the long-slit mode of the same instrument," the researchers wrote.

The observations found that CGCG014-074 exhibits distinct features, including a rotating inner disk, an extended stellar formation with the cessation of activity about two billion years ago, and boxy isophotes towards its outer regions. The study detected no evidence of a kinematically decoupled core, nor any traces of a major merger.

According to the paper, CGCG014-074 has a total stellar mass of 330 million solar masses and total dynamical mass of 800 million solar masses. These results are in good agreement with values obtained for other early-type dwarf galaxies.

The collected data indicate that CGCG014-074 has an old and metal-poor nucleus—with an age of about 9.3 billion years and metallicity of −0.84 dex. In contrast, its stellar disk is younger (about 4.4 billion years old) and has a higher metallicity (approximately -0.40 dex).

The authors of the paper conclude that CGCG014-074 underwent a prolonged period of stellar formation from its beginning until about two billion years ago when its star formation ceased and it reached 100% of its stellar mass. Therefore, based on the new study, they perceive CGCG014-074 as a probable building block galaxy that has evolved passively throughout its history.