Galaxies that feed on other galaxies

February 1, 2018, Instituto de Astrofísica de Canarias (IAC)
Distant Milky Way halo giants marked on a Pan-STARRS1 map. Location of our targets overlaid on a RGB rendering of the distribution of Milky Way halo stars. Credit: Giuseppina Battaglia

An international team of astronomers led by Giuseppina Battaglia, researcher at the Instituto de Astrofísica de Canarias (IAC), finds signs that the outer halo of the Milky Way contains stellar remains of massive dwarf galaxies that were devoured by our own.

Most of the information we have about the Milky Way comes from its inner region, which we can observe close to the solar neighbourhood. However, for the first time, the chemical properties of the external regions of the of our galaxy were explored with high-resolution spectroscopy in the optical of a sample of 28 red giant stars at large distances from the sun. Spectroscopic analysis consists of separating the light of the stars into its individual frequencies in order to obtain information on the star's chemical composition. The analysis of the of the stars can provide information on the characteristics of the environment in which they were born.

Giuseppina Battaglia, astrophysicist at the IAC and first author of the article, says, "The abundance of some chemical elements in the stars in the external regions of the Milky Way halo was surprisingly different from the information we had concerning the inner regions of the halo." On the other hand, several similarities were discovered in the chemical compositions observed for stars in nearby massive dwarf , such as Sagittarius and the Large Magellanic Cloud. These signatures tells us that the external regions of the stellar halo might contain the remains of one, or more, massive dwarf galaxies devoured by the Milky Way.

Stellar haloes are a common component of galaxies like the Milky Way. "The theory explaining the formation of structure and galaxies predicts that stellar halos, and in particular their outer regions, consist mainly of the stellar component of destroyed, smaller galaxies." G.Battaglia says, "Qualitatively, this is in agreement with the observational findings of this study, where we found remnants of cannibalized dwarf galaxies around the Milky Way."

For this study, data from about 100 hours of telescope observing time were used, obtained on facilities in both the Northern and Southern hemisphere. Specifically, the team used the Very Large Telescope "Kueyen" (UT2) of the European Southern Observatory in Paranal and the Magellan telescope Clay in Las Campanas, both in Chile, as well as the Hobby Eberly Telescope, in Texas.

Explore further: Astronomers conduct detailed chemical analysis of eleven globular clusters

More information: G. Battaglia et al, What is the Milky Way outer halo made of?, Astronomy & Astrophysics (2017). DOI: 10.1051/0004-6361/201731879

Related Stories

Uncovering the origins of galaxies' halos

November 21, 2017

Using the Subaru Telescope atop Maunakea, researchers have identified 11 dwarf galaxies and two star-containing halos in the outer region of a large spiral galaxy 25 million light-years away from Earth. The findings, published ...

New stellar stream discovered by astronomers

December 5, 2017

(—An international team of astronomers has detected a new thin stellar stream in the halo of the Milky Way galaxy. The newly discovered feature, named "jet stream," could help researchers answer fundamental questions ...

Stars in the halo of the Milky Way often travel in groups

January 31, 2017

Many stars in the halo that surrounds the Milky Way travel in groups. This is the outcome of a recent analysis of data for millions of stars from the Gaia space mission. Astronomers report their discovery today in the international ...

A shy galactic neighbor

September 16, 2015

The Sculptor Dwarf Galaxy, pictured in this new image from the Wide Field Imager camera, installed on the 2.2-metre MPG/ESO telescope at ESO's La Silla Observatory, is a close neighbour of our galaxy, the Milky Way. Despite ...

Image: Hubble's compact galaxy with big-time star formation

October 16, 2017

As far as galaxies are concerned, size can be deceptive. Some of the largest galaxies in the Universe are dormant, while some dwarf galaxies, such as ESO 553-46 imaged here by the NASA/ESA Hubble Space Telescope, can produce ...

Recommended for you

Magnetized inflow accreting to center of Milky Way galaxy

August 17, 2018

Are magnetic fields an important guiding force for gas accreting to a supermassive black hole (SMBH) like the one that our Milky Way galaxy hosts? The role of magnetic fields in gas accretion is little understood, and trying ...

Another way for stellar-mass black holes to grow larger

August 17, 2018

A trio of researchers with The University of Hong Kong, Academia Sinica Institute of Astronomy and Astrophysics in Taiwan and Northwestern University in the U.S., has come up with an alternative theory to explain how some ...

First science with ALMA's highest-frequency capabilities

August 17, 2018

The ALMA telescope in Chile has transformed how we see the universe, showing us otherwise invisible parts of the cosmos. This array of incredibly precise antennas studies a comparatively high-frequency sliver of radio light: ...

Six things about Opportunity's recovery efforts

August 17, 2018

NASA's Opportunity rover has been silent since June 10, when a planet-encircling dust storm cut off solar power for the nearly-15-year-old rover. Now that scientists think the global dust storm is "decaying"—meaning more ...

Sprawling galaxy cluster found hiding in plain sight

August 16, 2018

MIT scientists have uncovered a sprawling new galaxy cluster hiding in plain sight. The cluster, which sits a mere 2.4 billion light years from Earth, is made up of hundreds of individual galaxies and surrounds an extremely ...

Hubble paints picture of the evolving universe

August 16, 2018

Astronomers using the ultraviolet vision of NASA's Hubble Space Telescope have captured one of the largest panoramic views of the fire and fury of star birth in the distant universe. The field features approximately 15,000 ...


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.