From Instituto de Astrofísica de Canarias – IAC via Manu Garcia: “Sextans: the smallest cannibal galaxy discovered until now”


From Manu Garcia, a friend from IAC.

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From Instituto de Astrofísica de Canarias – IAC

Oct. 11, 2018

A team at the Instituto de Astrofísica de Canarias (IAC) has discovered a new case of galactic cannibalism in the neighbourhood of the Milky Way, which has caused the merging of two galaxies on the smallest scale so far known.

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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.


NOAO/CTIO Victor M Blanco 4m Telescope which houses the DECam at Cerro Tololo, Chile, housing DECam at an altitude of 7200 feet

Carnegie 6.5 meter Magellan Baade and Clay Telescopes located at Carnegie’s Las Campanas Observatory, Chile. over 2,500 m (8,200 ft) high

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)

See the full article here.


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The Instituto de Astrofísica de Canarias(IAC) is an international research centre in Spain which comprises:

The Instituto de Astrofísica, the headquarters, which is in La Laguna (Tenerife).
The Centro de Astrofísica en La Palma (CALP)
The Observatorio del Teide (OT), in Izaña (Tenerife).


Roque de los Muchachos Observatory is an astronomical observatory located in the municipality of Garafía on the island of La Palma in the Canary Islands, at an altitude of 2,396 m (7,861 ft)

These centres, with all the facilities they bring together, make up the European Northern Observatory(ENO).

The IAC is constituted administratively as a Public Consortium, created by statute in 1982, with involvement from the Spanish Government, the Government of the Canary Islands, the University of La Laguna and Spain’s Science Research Council (CSIC).

The International Scientific Committee (CCI) manages participation in the observatories by institutions from other countries. A Time Allocation Committee (CAT) allocates the observing time reserved for Spain at the telescopes in the IAC’s observatories.

The exceptional quality of the sky over the Canaries for astronomical observations is protected by law. The IAC’s Sky Quality Protection Office (OTPC) regulates the application of the law and its Sky Quality Group continuously monitors the parameters that define observing quality at the IAC Observatories.

The IAC’s research programme includes astrophysical research and technological development projects.

The IAC is also involved in researcher training, university teaching and outreachactivities.

The IAC has devoted much energy to developing technology for the design and construction of a large 10.4 metre diameter telescope, the ( Gran Telescopio CANARIAS, GTC), which is sited at the Observatorio del Roque de los Muchachos.



Gran Telescopio Canarias at the Roque de los Muchachos Observatory on the island of La Palma, in the Canaries, SpainGran Telescopio CANARIAS, GTC