ASKAP reveals a powerful outflow shaping a nearby galaxy

Using the Australian Square Kilometer Array Pathfinder (ASKAP), an international group of astronomers has identified an impressive bipolar outflow emerging from the disk of a nearby galaxy called ESO 130-G012. The result has been described in a study published on December 17 on the arXiv preprint server.

ESO 130-G012 is an edge-on galaxy located roughly 55 million light-years away. It is estimated to contain about 11 billion solar masses in stars. The galaxy forms new stars at a rate of about 0.2 solar masses per year and is known to host a central black hole with a mass around 50 million times that of the Sun.

Something is escaping from the disk

A team led by Bärbel S. Koribalski from Western Sydney University in Australia turned ASKAP toward ESO 130-G012 to study its bright, star-forming stellar disk as part of the Evolutionary Map of the Universe (EMU) project. In ASKAP’s 944-MHz radio continuum images, the researchers detected a striking outflow originating from the disk of the galaxy.

“While examining deep ASKAP EMU 944 MHz radio continuum data, we identified a bipolar outflow extending at least 6 arcminutes (about 30 kiloparsecs) above and below the edge-on stellar disk of ESO 130-G012,” the team wrote.

An hourglass in space

According to the paper, the outflow stretches between 100,000 and 160,000 light-years into the galaxy’s halo on each side of the star-forming disk, which acts as the narrow central “waist.” In shape, it resembles a closed hourglass whose waist measures roughly 33,000 light-years across.

The images show that ESO 130-G012’s radio continuum emission is composed of several distinct features: a central core, inner knots linked to the inner ring, a thin disk, a thicker box-shaped disk, and X-shaped radio wings emerging from the edges of this thicker region. Together, these form the broad base of a massive hourglass-shaped radio outflow.

The bipolar structure seems to rise almost straight up from the stellar disk at first, then expands sideways as it continues outward. The opening angle of the outflow relative to a direction perpendicular to the disk is estimated to be about 30 degrees on each side.

Possible origin and next steps
To explain what might be powering such an outflow, the researchers suggest it is probably being driven by processes associated with star formation, including stellar winds and cosmic rays, across the full width of the stellar disk. However, they also note that they cannot rule out possible contributions from a previously more active central black hole or a past starburst event.

The team emphasizes that the detection of this bipolar outflow makes ESO 130-G012 a compelling object for additional study.

“Our discovery of a large-scale radio continuum outflow from the disk of ESO 130-G012 makes it an excellent candidate for future observations aimed at probing the disk–halo connection and modeling how such outflows form,” they conclude.

More info: arXiv