Sextans: the smallest cannibal galaxy discovered until now

Several examples of massive galaxies merging. Credits: NASA, ESA, the Hubble Heritage and Collaboration, and A. Evans.
Several examples of massive galaxies merging. Credits: NASA, ESA, the Hubble Heritage and Collaboration, and A. Evans.
Advertised on

The researchers at the IAC Luis Cicuéndez and Giuseppina Battaglia have found a case of galactic cannibalism on the smallest known scale until now. This is the Sextans galaxy, which has a mass some 100,000 times less than that of the Milky Way but has swallowed an even smaller companion.

Using data form the Victor M. Blanco Telescope (4m diameter) at the Cerro Tololo Interamerican Observatory and the Landon Clay 6 m telescope, also known as Magellan 2, at the Las Campanas Observatory, both in Chile, they observed clear signs that Sextans had absorbed a smaller stellar system.

When they analyzed the dwarf galaxy they observed that the spatial distribution of the blue, metal-poor stars was round and regular, while that of the red, metal-rich stars was much more elliptical and irregular, with an overdensity of stars on the north-eastern side. “The most reasonable explanation of this phenomenon is that two galaxies merged, and had different metallicities” explains Luis Cicuéndez, a researcher at the IAC and at the University of La Laguna.

The analysis of the velocities and of indicators of the chemical composition of the stars reveal the presence of a spatial sub-structure in the shape of a ring. This substructure shows a much higher velocity and a different chemical composition than the rest of the stars in the galaxy.

 “This finding appears to show that the hierarchical theory of galaxy formation, in which small galaxies merge to form larger ones, can explain the formation of even the smallest known galaxies, the dwarf galaxies” explains the IAC researcher and co-author of the study Giuseppina Battaglia.

The details of this new discovery are published in the latest volume of the journal Monthly Notices of the Royal Astronomical Society (MNRAS)

Article: Cicuéndez, L. y Battaglia, G. Appearances can be deceiving: clear signs of accretion in the seemingly ordinary Sextans dSph. Monthly Notices of the Royal Astronomical Society, Volume 480, Issue 1, 11 October 2018, Pages 251–260. DOI: 10.1093/mnras/sty1748

News type
Press release
Scope
Observatorios de Canarias
SO Research
General public
Communications media
The Milky Way and the Local Group (MWLG)
SEVERO OCHOA

It may interest you

  • Artist’s impression of TIC 241249530 b
    Press release
    Eccentric exoplanet reveals how hot jupiters form
    An international scientific team, in which the Instituto de Astrofísica de Canarias (IAC) participates, has discovered the extremely eccentric orbit of a gas giant exoplanet. This world, called TIC 241249530 b, not only follows one of the most drastically stretched-out orbits of all known transiting exoplanets, but also is also orbiting its star backwards, lending insight into the mystery of how these high-mass gas giants evolve into hot Jupiters , with very close and circular trajectories. The study is published in Nature. Within the population of known exoplanets, there are those that
    Advertised on
  • An artist’s concept of the exoplanet SPECULOOS-3 b orbiting its red dwarf star. The planet is as big around as Earth, while its star is slightly bigger than Jupiter – but much more massive. Credit: NASA/JPL-Caltech
    Press release
    Astronomers discover Earth-sized exoplanet orbiting ultra-cool star
    An international scientific team, with the participation of researchers from the Instituto de Astrofísica de Canarias (IAC), has found a new world similar in size to our planet orbiting an ultra-cold red dwarf located about 55 light-years away. Observations from the SPECULOOS telescope network, which includes the ARTEMIS telescope at the Teide Observatory in Tenerife, have made this discovery possible. The Gran Telescopio Canarias (GTC), at the Roque de los Muchachos Observatory on La Palma, has also played a key role in confirming the discovery, providing some of the most accurate ground
    Advertised on
  • Jornada de puertas abiertas en el Observatorio del Teide
    Press release
    Cientos de personas acuden a las jornadas de puertas abiertas del Observatorio del Teide
    Cientos de personas se han acercado este fin de semana al Observatorio del Teide para participar en las tradicionales jornadas de puertas abiertas que organiza el Instituto de Astrofísica de Canarias coincidiendo con la semana del solsticio de verano. Esta actividad, organizada de forma conjunta por el Observatorio del Teide y por la Unidad de Comunicación y Cultura Científica (UC3) del IAC, forma parte de las tareas de divulgación que realiza el Instituto para que la ciudadanía pueda conocer de primera mano uno de los mejores observatorios del mundo, sus infraestructuras, el trabajo de su
    Advertised on