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Composite image of the MACSJ0717.5 + 3745 galaxy cluster, with a VLA radio image superimposed on a visible light image from the Hubble Space Telescope. The indentation is a detail of the distant galaxy VLAHFF-J071736.66 + 374506.4 – possibly the weakest radio-emitting object ever found – revealed by the magnifying effect of the gravitational lens. Credit: Heywood et al .; Sophia Dagnello, NRAO / AUI / NSF; STScI.
Radio telescopes are the most sensitive radio receivers in the world, capable of finding extremely weak strands of radio emissions from objects at the far reaches of the universe. Recently, a team of astronomers used the National Science Foundation’s Karl G. Jansky Very Large Array (VLA) to take advantage of nature’s helping hand to detect a distant galaxy that is likely the most radio transmitting object. weakest ever found.
The discovery was part of the VLA Frontier Fields Legacy Survey, led by NRAO astronomer Eric Murphy, who used clusters of distant galaxies as natural lenses to study objects even further afield. The clusters served as gravitational lenses, using the gravitational pull of galaxies within the clusters to bend and amplify light and radio waves from more distant objects.
VLA radio image superimposed on a Hubble Space Telescope image of the MACSJ0717.5 + 3745 galaxy cluster. Prominent red-orange objects are large structures called radio relics, possibly caused by shock waves within the cluster. . Credit: Heywood et al .; Sophia Dagnello, NRAO / AUI / NSF; STScI.
In this composite, a VLA radio image is superimposed on a visible light image of the The Hubble Space Telescope. The prominent red-orange objects are radio relics – large structures likely caused by shock waves – inside the prominent cluster of galaxies, known as MACSJ0717.5 + 3745, at over 5 billion light years from Earth.
Detailed observations from the VLA have shown that many galaxies in this image emit radio waves in addition to visible light. VLA data revealed that one of these galaxies, shown in the recess, is more than 8 billion light-years away. Its light and radio waves have been distorted by the gravitational lensing effect of the intervening cluster.
The radio image of this distant galaxy, called VLAHFF-J071736.66 + 374506.4, was magnified more than 6 times by the gravitational lens, astronomers said. It was this magnification that allowed the VLA to detect it.
The distant galaxy VLAHFF-J071736.66 + 374506.4, more than 8 billion light years from Earth. Credit: Heywood et al .; Sophia Dagnello, NRAO / AUI / NSF; STScI.
“This is possibly the weakest radio emitting object ever detected,” said Ian Heywood of the University of Oxford in the UK. “This is exactly why we want to use these galaxy clusters as powerful cosmic lenses to learn more about the objects behind them.”
“The magnification provided by the gravitational lens, combined with extremely sensitive VLA imaging, gave us an unprecedented look at the structure of a galaxy 300 times less massive than our Milky Way at a time when the universe was less than half of its current age. This gives us valuable information about the formation of stars in these low-mass galaxies at that time and how they eventually came together into more massive galaxies, ”said Eric Jimenez-Andrade, of NRAO.
Scientists report their work in a pair of papers in the Astrophysics Journal.
The references:
“The VLA Frontier Fields Survey: Deep, High-resolution Radio Imaging of the MACS Lensing Clusters at 3 and 6 GHz” by I. Heywood, EJ Murphy, EF Jiménez-Andrade, L. Armus, WD Cotton, C. DeCoursey, M . Dickinson, TJW Lazio, E. Momjian, K. Penner, I. Smail and OM Smirnov, accepted, Astrophysics Journal.
arXiv: 2103.07806
“The VLA Frontier Field Survey: A Radio and UV / Optical Size Comparison of 0.3≲z≲3 star-forming galaxies” by EF Jiménez-Andrade, EJ Murphy, I. Heywood, I Smail, K. Penner, E. Momjian, M. Dickinson, L. Armus and TJW Lazio, accepted, Astrophysics Journal.
arXiv: 2103.07807
The National Radio Astronomical Observatory is a facility of the National Science Foundation, operated under a cooperative agreement by Associated Universities, Inc.
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