According to the newest cosmological fashions, massive spiral galaxies such because the Milky Way grew by absorbing smaller galaxies, by a form of galactic cannibalism. Evidence for that is given by very massive constructions, the tidal stellar streams, that are noticed round them, that are the stays of those satellite tv for pc galaxies. But the total histories of nearly all of these instances are onerous to check, as a result of these flows of stars are very faint, and solely the stays of the newest mergers have been detected.
A research led by the Instituto de Astrofísica de Andalucía (IAA-CSIC), with the participation of the Instituto de Astrofísica de Canarias (IAC), has made detailed observations of a big tidal circulate across the Sombrero galaxy, whose unusual morphology has nonetheless not been definitively defined. The outcomes are revealed at this time within the journal Monthly Notices of the Royal Astronomical Society (MNRAS).
The Sombrero galaxy (Messier 104) is a galaxy some thirty million gentle years away, which is a part of the Local Supercluster (a gaggle of galaxies which incorporates the Virgo cluster and the Local Group containing the Milky Way). It has roughly one third of the diameter of the Milky Way, and exhibits traits of each of the dominant forms of galaxies within the Universe, the spirals and the ellipticals. It has spiral arms, and a really massive vibrant central bulge, which makes it appear to be a hybrid of the 2 varieties.
“Our motive for acquiring these very deep photographs of the Sombrero galaxy (Messier 104) was to search for the stays of its merger with a really huge galaxy. This potential collision was not too long ago prompt on the premise of research of the stellar inhabitants of its unusual halo obtained with the Hubble Space Telescope,” says David Martínez-Delgado, a researcher on the IAA-CSIC and first creator of the paper reporting the work.
The observations with the Hubble, in 2020, confirmed that the halo, an intensive and faint area surrounding the Sombrero galaxy, exhibits many stars wealthy in metals, components heavier than hydrogen and helium. This is a characteristic to typical of latest generations of stars, that are usually discovered within the discs of galaxies, and are fairly uncommon in galactic halos, that are populated by previous stars. To clarify their presence astronomers prompt what is named “a moist merger,” a situation through which a big elliptical galaxy is rejuvenated by massive portions of fuel and dirt from one other huge galaxy, which went into the formation of the disc which we now observe.
“In our photographs we’ve got not discovered any proof to help this speculation, though we can not rule out that it may have occurred a number of thousand million years in the past, and the particles is totally dissipated by now -explains David Martínez-Delgado-. In our search we’ve got in reality been capable of hint for the primary time the whole tidal stream which surrounds the disc of this galaxy, and our theoretical simulations have allow us to reconstruct its formation within the final three thousand million years, by cannibalism of a satellite tv for pc dwarf galaxy.”
“Observational strategies in current day Astrophysics want superior picture processing. Our modelling of the intense stars across the Sombrero galaxy, and on the similar time of the halo gentle of the galaxy itself has enabled us to unveil the character of this tidal stream. It is exceptional that thanks to those superior photometric strategies we’ve got been capable of do entrance line science with a Messier object utilizing solely an 18 cm (diameter) telescope,” explains Javier Román, a postdoctoral researcher on the IAC and a co-author of the research.
The analysis group rejects the concept that the big stellar tidal stream, recognized for greater than three many years, may very well be associated to the occasion which produced the unusual morphology of the Sombrero galaxy which, if it was attributable to a moist merger, would wish the interplay of two galaxies with massive lots.
The work has been potential due to the collaboration between skilled and novice astronomers. “We have collaborated with the Spanish astrophotographer Manuel Jiménez, who took the pictures with a robotic telescope of 18 centimetre diameter, and the well-known australian astrophotographer David Malin, who found this tidal stream on photographic plates taken within the 90’s of the final century. This collaboration exhibits the potential of novice telescopes to take deep photographs of close by galaxies which give vital clues concerning the strategy of their meeting which is continuous till the current epoch,” concludes Martínez-Delgado.