“Vampire” Galaxy Sucks Star-Forming Gas from its Neighbors

What happens when a galaxy doesn’t have enough hydrogen to support its stellar production process? Why, it sucks it from its hapless neighbors like some sort of cosmic vampire, that’s what. And evidence of this predatory process is what’s recently been observed with the National Science Foundation’s Robert C. Byrd Green Bank Telescope (GBT) in West Virginia, in the form of faint “cold flows” bridging intergalactic space between the galaxy NGC 6946 and its smaller companions.

“We knew that the fuel for star formation had to come from somewhere,” said astronomer D.J. Pisano from West Virginia University, author of the study. “So far, however, we’ve detected only about 10 percent of what would be necessary to explain what we observe in many galaxies. A leading theory is that rivers of hydrogen – known as cold flows – may be ferrying hydrogen through intergalactic space, clandestinely fueling star formation. But this tenuous hydrogen has been simply too diffuse to detect, until now.”

NGC 6946 also goes by the festive moniker of “the Fireworks Galaxy,” due to the large amount of supernovae that have been observed within its arms — eight within the past century alone. Located 22 million light-years away between the constellations Cepheus and Cygnus, NGC 6946’s high rate of star formation has made astronomers curious as to how it (and other starburst galaxies like it) gets its stellar fuel.

One long-standing hypothesis is that large galaxies like NGC 6946 receive a constant supply of hydrogen gas by drawing it off their less-massive companions.

Chandra and Gemini image of NGC 6946 (X-ray: NASA/CXC/MSSL/R.Soria et al, Optical: AURA/Gemini OBs)
Chandra and Gemini image of NGC 6946 (X-ray: NASA/CXC/MSSL/R.Soria et al, Optical: AURA/Gemini OBs)

Now, thanks to the GBT’s unique capabilities — such as its immense single dish, unblocked aperture, and location in the National Radio Quiet Zone — direct observations have been made of the extremely faint radio emissions coming from neutral hydrogen flows connecting NGC 6946 with its smaller satellite galaxies.

According to a press release from the National Radio Astronomy Observatory:

Earlier studies of the galactic neighborhood around NGC 6946 with the Westerbork Synthesis Radio Telescope (WSRT) in the Netherlands have revealed an extended halo of hydrogen (a feature commonly seen in spiral galaxies, which may be formed by hydrogen ejected from the disk of the galaxy by intense star formation and supernova explosions). A cold flow, however, would be hydrogen from a completely different source: gas from intergalactic space that has never been heated to extreme temperatures by a galaxy’s star birth or supernova processes.

Another possible source of the cold flow is a previous collision with another galaxy, possibly even one of its own satellites, which would have left strands of atomic hydrogen in its wake. But if that were the case stars would likely have since formed within the filaments themselves, which has not yet been observed.

Pisano’s findings have been published in the Astronomical Journal.

Source: NRAO press release. Learn more about the Green Bank Telescope here.

Image credit: D.J. Pisano (WVU); B. Saxton (NRAO/AUI/NSF); Palomar Observatory – Space Telescope Science Institute 2nd Digital Sky Survey (Caltech); Westerbork Synthesis Radio Telescope

Fluorescent and Starry: New Zinger Space Images From Chandra’s X-Ray Archives

You know that moment when you’re flipping through old digital pictures (on your computer or phone or whatever) and you realize there are some pretty awesome ones in there that you should share on social media? The Chandra X-Ray Observatory team also decided to plumb THEIR archive of astrophysical image magic, and came up with several beauties. Such as the one above this text.

Chandra has been in space since July 23, 1999 — yes, that’s well over 14 years ago — and is considered one of NASA’s telescopes under the “Great Observatories” programs. The other telescopes, by the way, are the Hubble Space Telescope, the Compton Gamma-Ray Observatory and the Spitzer Space Telescope. Hubble and Spitzer are also still active today.

Check out more from the new set of images below. There are eight all told, representing a tiny fraction of the unprocessed thousands of images available to the public in the Chandra Source Catalog.

The Elephant Trunk Nebula (IC 1396A) in X-ray, optical and infrared light. Astronomers believe they are seeing winds from large, young stars hitting cooler gas around it, possibly triggering new starbirth. X-ray data from Chandra is in purple, with optical data (red, green and blue) and infrared (orange and cyan). Credit: X-ray: NASA/CXC/PSU/Getman et al, Optical: DSS, Infrared: NASA/JPL-Caltech
The Elephant Trunk Nebula (IC 1396A) in X-ray, optical and infrared light. Astronomers believe they are seeing winds from large, young stars hitting cooler gas around it, possibly triggering new starbirth. X-ray data from Chandra is in purple, with optical data (red, green and blue) and infrared (orange and cyan). Credit: X-ray: NASA/CXC/PSU/Getman et al, Optical: DSS, Infrared: NASA/JPL-Caltech
3C353 looks a bit like a tadpole. In the center of this image is a galaxy powered by a supermassive black hole, which is transmitting energy across the expanse. Radiation is visible in X-rays from Chandra (purple) and radio from the Very Large Array (orange.) Credit: X-ray: NASA/CXC/Tokyo Institute of Technology/J.Kataoka et al, Radio: NRAO/VLA
3C353 looks a bit like a tadpole. In the center of this image is a galaxy powered by a supermassive black hole, which is transmitting energy across the expanse. Radiation is visible in X-rays from Chandra (purple) and radio from the Very Large Array (orange.) Credit: X-ray: NASA/CXC/Tokyo Institute of Technology/J.Kataoka et al, Radio: NRAO/VLA
SNR B0049-73.6 in X-ray and infrared light.  Chandra's observations (purple) revealed that the explosion seen here was likely from a star's central core collapse. Infrared data from the 2MASS survey is also visible in red, green and blue. Credit: X-ray: NASA/CXC/Drew Univ/S.Hendrick et al, Infrared: 2MASS/UMass/IPAC-Caltech/NASA/NSF
SNR B0049-73.6 in X-ray and infrared light. Chandra’s observations (purple) revealed that the explosion seen here was likely from a star’s central core collapse. Infrared data from the 2MASS survey is also visible in red, green and blue. Credit: X-ray: NASA/CXC/Drew Univ/S.Hendrick et al, Infrared: 2MASS/UMass/IPAC-Caltech/NASA/NSF
NGC 4945, a galaxy 13 million light years from Earth. This galaxy is similar to the Milky Way, but has a more active supermassive black hole in the center (visible in white). Chandra X-ray data is in blue, overlaid on European Space Observatory optical information. Credit: X-ray: NASA/CXC/Univ degli Studi Roma Tre/A.Marinucci et al, Optical: ESO/VLT & NASA/STScI
NGC 4945, a galaxy 13 million light years from Earth. This galaxy is similar to the Milky Way, but has a more active supermassive black hole in the center (visible in white). Chandra X-ray data is in blue, overlaid on European Space Observatory optical information. Credit: X-ray: NASA/CXC/Univ degli Studi Roma Tre/A.Marinucci et al, Optical: ESO/VLT & NASA/STScI
3C 397, sometimes called G41.1-0.3, is a supernova leftover that looks a little funny. It's possible that the shape comes from heated remains of the star's shell bump into cooler gas surrounding it. X-ray data from Chandra is purple, infrared data from the Spitzer Space Telescope is yellow, and optical data from the Digitized Sky Survey is in red, green and blue. Credit: X-ray: NASA/CXC/Univ of Manitoba/S.Safi-Harb et al, Optical: DSS, Infrared: NASA/JPL-Caltech
3C 397, sometimes called G41.1-0.3, is a supernova leftover that looks a little funny. It’s possible that the shape comes from heated remains of the star’s shell bump into cooler gas surrounding it. X-ray data from Chandra is purple, infrared data from the Spitzer Space Telescope is yellow, and optical data from the Digitized Sky Survey is in red, green and blue. Credit: X-ray: NASA/CXC/Univ of Manitoba/S.Safi-Harb et al, Optical: DSS, Infrared: NASA/JPL-Caltech
NGC 3576, a nebula 9,000 light-years from Earth, in X-ray (blue) and optical data. Chandra spotted evidence of strong winds coming from young stars in the nebula. Optical data from the European Space Observatory is shown in orange and yellow. Credit: X-ray: NASA/CXC/Penn State/L.Townsley et al, Optical: ESO/2.2m telescope
NGC 3576, a nebula 9,000 light-years from Earth, in X-ray (blue) and optical data. Chandra spotted evidence of strong winds coming from young stars in the nebula. Optical data from the European Space Observatory is shown in orange and yellow. Credit: X-ray: NASA/CXC/Penn State/L.Townsley et al, Optical: ESO/2.2m telescope
G266.2-1.2 in X-ray (purple) and optical light. Chandra spotted high-energy particles shooting out from this supernova leftover. The optical data comes from the Digitized Sky Survey and is available in red, green, and blue. Credit: X-ray: NASA/CXC/Morehead State Univ/T.Pannuti et al, Optical: DSS
G266.2-1.2 in X-ray (purple) and optical light. Chandra spotted high-energy particles shooting out from this supernova leftover. The optical data comes from the Digitized Sky Survey and is available in red, green, and blue. Credit: X-ray: NASA/CXC/Morehead State Univ/T.Pannuti et al, Optical: DSS