Jellyfish-shaped galaxy found in Abell 2670 cluster

April 24, 2017 by Tomasz Nowakowski, report
(a) and (b) Zoom-in images of some of the starforming blobs, Hα flux map is superimposed over deep r'-band image, (c) a schematic view of the blobs. Credit: Sheen et al., 2017.

(—Using the Multi Unit Spectroscopic Explorer (MUSE), astronomers have identified a new elliptical jellyfish-like galaxy in the Abell 2670 cluster. The newly detected galaxy showcases spectacular one-sided tails of gas and young stars, which indicates intense ram-pressure stripping. The findings were presented Apr. 18 in a paper published on the arXiv pre-print server.

The so-called "jellyfish" galaxies are extreme examples of stripped galaxies exhibiting tentacles of debris material with a characteristic jellyfish-like morphology. When a galaxy infalls into a massive cluster halo, it experiences ram pressure as it moves through the intracluster medium. The ram pressure is responsible for gas stripping processes and for creating star-forming tails and blobs.

Although elliptical galaxies experience ram pressure when they move through intracluster medium, they are unlikely to be significantly affected by such force due to their gas-poor nature and low levels of star formation. Notably, jellyfish-like features have not been reported in elliptical galaxies yet, so the new discovery is invaluable for researchers studying the morphology of such galaxies.

In the recently published paper, a team of astronomers led by Yun-Kyeong Sheen of the Korea Astronomy and Space Science Institute in Daejeon, South Korea, presents the results of observation of Abell 2670 cluster using the MUSE instrument mounted on ESO's Very Large Telescope (VLT) in Chile. The deep optical images obtained by MUSE allowed the researchers to discover a new elliptical galaxy showing disturbed halo features and surrounded by several blue blobs.

"In this paper, we present MUSE observations of an elliptical galaxy in Abell 2670 with long tails of material visible in the optical spectra, as well as blobs with tadpole-like morphology," the authors wrote in the paper.

In particular, the team found an extended H-alpha disk at the galaxy center, with bright concentrated emission at the centre, and long ionized gas tails emanating from the disk. They also detected several blue star forming blobs, with a tadpole-like morphology, surrounding the galaxy. Moreover, they found H-alpha blobs located at the positions corresponding to the blue blobs found in deep optical images.

The researchers noted that the observed gas tails point away from the cluster center, which could be an indicator of a ram-pressure stripping currently taking place. Furthermore, the tails of star forming blobs point upstream, towards the cluster center, which also supports this assumption.

The authors concluded that the newly found galaxy is a post-merger elliptical galaxy currently undergoing ram pressure stripping. They assume that the gas and the star-forming blobs were most likely acquired during a past wet merger.

"Where does the gas come from? A likely scenario is that a wet merger occurred. Many merger features are apparent, as indicated by disturbed halo features and stellar streams in our deep optical imaging. (…) Another possibility is that these star-forming blobs are, in fact, tidal dwarf (TDGs) formed during the wet merger. This could explain their large masses, and lack of a spatial correlation with the ionized gas stream," the paper reads.

Explore further: New extended ionized gas clouds detected in Abell 1367 cluster

More information: Discovery of ram pressure stripped gas around an elliptical galaxy in Abell 2670,

Studies of cluster galaxies are increasingly finding galaxies with spectacular one-sided tails of gas and young stars, suggestive of intense ram-pressure stripping. These so-called "jellyfish" galaxies typically have late-type morphology. In this paper, we present MUSE observations of an elliptical galaxy in Abell 2670 with long tails of material visible in the optical spectra, as well as blobs with tadpole-like morphology. The spectra in the central part of the galaxy reveals a stellar component as well as ionized gas. The stellar component does not have significant rotation, while the ionized gas defines a clear star-forming gas disk. We argue, based on deep optical images of the galaxy, that the gas was most likely acquired during a past wet merger. It is possible that the star-forming blobs are also remnants of the merger. In addition, the direction and kinematics of the one-sided ionized tails, combined with the tadpole morphology of the star-forming blobs, strongly suggests that the system is undergoing ram pressure from the intracluster medium. In summary, this paper presents the discovery of a post-merger elliptical galaxy undergoing ram pressure stripping.

Related Stories

Hubbles spies the beautiful galaxy IC 335

December 24, 2014

This new NASA/ESA Hubble Space Telescope image shows the galaxy IC 335 in front of a backdrop of distant galaxies. IC 335 is part of a galaxy group containing three other galaxies, and located in the Fornax Galaxy Cluster ...

Galactic fireworks illuminate monster hydrogen blob

September 21, 2016

An international team of researchers using the Atacama Large Millimeter/submillimeter Array (ALMA) and other telescopes has discovered the power source illuminating a so-called Lyman-alpha Blob – a rare, brightly glowing, ...

First ultra-compact dwarf galaxy in the group NGC 5044 found

February 27, 2017

(—A team of astronomers led by Favio Faifer of the National University of La Plata, Argentina, has discovered the first ultra-compact dwarf (UCD) galaxy in an X-ray bright galaxy group designated NGC 5044. The ...

Recommended for you

Japan space robots start asteroid survey

September 22, 2018

A pair of robot rovers have landed on an asteroid and begun a survey, Japan's space agency said Saturday, as it conducts a mission aiming to shed light on the origins of the solar system.

First to red planet will become Martians: Canada astronaut

September 22, 2018

Astronauts traveling through space on the long trip to Mars will not have the usual backup from mission control on Earth and will need to think of themselves as Martians to survive, Canada's most famous spaceman half-jokingly ...

Three NASA missions return first-light data

September 21, 2018

NASA's continued quest to explore our solar system and beyond received a boost of new information this week with three key missions proving not only that they are up and running, but that their science potential is exceptional. ...

1 comment

Adjust slider to filter visible comments by rank

Display comments: newest first

1 / 5 (5) Apr 24, 2017
Furthermore, the tails of star forming blobs point upstream, towards the cluster center, which also supports this assumption.

That is the clue that the galaxy is actually moving apart from the cluster, not toward it as assumed by the common merger maniac with limited conceptual bandwidth. The blobs are likely formed from leading ejected massive cores preceding the diverging main galaxy. The leading cores themselves are a secondary source for the gas within the blobs. And the tail is formed from trailing gas ejected or not fully captured from the preceding blobs, by the diverging main galaxy itself.

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.