Peering deep into the stellar nursery of the Orion Nebula: U of T astronomers part of team

ullahnor — Thu, 15 Jun 2017 21:01:27 +0000

ullahnor Thu, 06/15/2017 - 17:01

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In this composite image, the filament of ammonia molecules appears red and Orion Nebula gas appears blue (image courtesy of R. Friesen, Dunlap Institute; J. Pineda, MPE; GBO/AUI/NSF)

Chris Sasaki

Author legacy

Chris Sasaki

Topic

Breaking Research

Dunlap

Astronomy

Astrophysics

Space

Astronomers have released an image of a vast filament of star-forming gas, 1,200 light-years away, in the stellar nursery of the Orion Nebula.

The image shows ammonia molecules within a 50-light-year long filament detected through radio observations made with the Robert C. Byrd Green Bank Telescope in West Virginia. It accompanies the first release of results from a research collaboration published in the Astrophysical Journal Supplement.

A team of researchers are collaborating on a survey of all the major, nearby star-forming regions in the northern half of the Gould Belt – a ring of young stars and gas clouds that circles the entire sky and runs through the constellation Orion. The researchers hope the survey will eventually provide a clearer picture over a larger portion of the sky of the temperatures and motions of gas within these dynamic stellar nurseries.

“We still don’t understand in detail how large clouds of gas in our galaxy collapse to form new stars,” says Rachel Friesen, one of the collaboration’s co-principal researchers who until recently was a fellow at U of T's Dunlap Institute for Astronomy & Astrophysics.

“But ammonia is an excellent tracer of dense, star-forming gas, and these large ammonia maps will allow us to track the motions and temperature of the densest gas. This is critical to assessing whether gas clouds and filaments are stable, or are undergoing collapse on their way to forming new stars.”

The image is combined with an image of the Orion Nebula – an object familiar to amateur and professional astronomers alike – taken with NASA’s wide-field infrared survey explore (WISE) telescope.

The collaboration’s other co-principal investigator is Jaime Pineda, from the Max Planck Institute for Extraterrestrial Physics. The team also includes Associate Professor Chris Matzner and graduate student Ayushi Singh from the ��Ƶ’s department of astronomy & astrophysics, and the Canadian Institute for Theoretical Astrophysics Professor Peter Martin, who helped found the Dunlap Institute.

‘Peter Pan’ radio galaxies that never grow old: U of T astronomer part of discovery of 1,500 young galaxies

ullahnor — Mon, 13 Mar 2017 18:47:55 +0000

‘Peter Pan’ radio galaxies that never grow old: U of T astronomer part of discovery of 1,500 young galaxies

ullahnor Mon, 03/13/2017 - 14:47

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An artist’s impression illustrates high-speed jets from supermassive black holes. The jets have very strong emissions at radio wavelengths (photo image by ESA/Hubble, L. Calçada/ESO)

Chris Sasaki

Author legacy

Chris Sasaki

Topic

Breaking Research

Dunlap

Faculty of Arts & Science

Galaxy

Space

Planets

A team of astronomers has doubled the number of known young, compact radio galaxies – galaxies powered by newly energized black holes. The newly found 1,500 galaxies will help astronomers understand the relationship between the size of these radio sources and their age, as well as the nature of the galaxy itself.

In particular, it will help astronomers understand why there are so many more young radio galaxies than old.

“These compact galaxies used to be as rare as hen’s teeth,” says Professor Bryan Gaensler, a co-author on the paper and director of the Dunlap Institute for Astronomy & Astrophysics at the ��Ƶ. “But now we’ve been able to discover a huge number of new cases. This breakthrough will let us begin to study the overall properties of these unusual and important objects.”

A radio galaxy is a galaxy that shines brightly at radio wavelengths. A super-massive black hole – typically with the mass of millions of suns – powers this outpouring of energy.

Gas and dust fall into the black hole, releasing vast amounts of energy. The energy is focused into two jets of particles, travelling in opposite directions at nearly the speed of light. As the jets blast through the galaxy, each generates its own lobe or hot-spot of radiation as it interacts with the gas in the galaxy.

In a survey of ninety thousand radio galaxies, the astronomers identified the radio compact galaxies among them. The results are described in a paper published Feb. 20 in the Astrophysical Journal.

“We do not understand how radio galaxies evolve,” says Joseph Callingham, a postdoctoral researcher from the Netherlands Institute for Radio Astronomy (ASTRON) and lead author on the paper describing the result.

“For a long time, we thought all small galaxies evolved into massive galaxies. However, we have now found far too many small galaxies relative to the large ones. This suggests some never make it to the ‘adult phase’.”

According to one model, compact radio sources are young because the jets have not had time to reach far beyond the central black hole. The hot-spots are relatively close together and look like compact sources. Over time, the jets reach farther out into the galaxy and even beyond its confines; the hot-spots are farther from each other, and they are seen as a more extended, double-lobed source.

In this simple model, the overabundance of young, compact radio galaxies raises the question: why don’t young, compact radio galaxies mature into old, extended radio galaxies?

However, another model argues that the relationship between the age and observed size of a radio galaxy is not so straightforward. That’s because a compact source may be compact not because it’s young, but because gas within the galaxy is dense enough to prevent the jets from extending far from the central black hole, meaning it remains compact despite its age.

“This study shows that it is possible a dense environment near the heart of the galaxy hinders and stops galaxy growth,” says Callingham, who did much of the research as a PhD student with the Australian Centre for All-shy Astrophysics (CAASTRO).

The astronomers made the discovery using data gathered with the Murchison Wide-field Array (MWA), an interferometric radio telescope in the Western Australian outback. The discovery was possible because, unlike conventional radio telescopes that observe tiny patches of the sky at a time, the MWA sweeps large areas of the sky and is capable of observing across a broader range of wavelengths.