An unusual ultrafaint dwarf galaxy has been discovered on the outskirts of the Andromeda galaxy with the help of several facilities from NSF’s NOIRLab. The galaxy, named Pegasus V, was first discovered as part of a systematic search for Andromeda dwarfs coordinated by David Martinez-Delgado of the Instituto de Astrofísica de Andalucía, Spain, when amateur astronomer Giuseppe Donatiello saw a strange “blot” in data discovered in a[{” attribute=””>DESI Legacy Imaging Surveys-Bild.” width=”777″ height=”396″ src=”https://scitechdaily.com/images/Ultra-Faint-Dwarf-Galaxy-Pegasus-V-Circled-777×396.jpg 777w,https://scitechdaily.com/images/Ultra-Faint-Dwarf-Galaxy-Pegasus-V-Circled-400×204.jpg 400w,https://scitechdaily.com/images/Ultra-Faint-Dwarf-Galaxy-Pegasus-V-Circled-768×391.jpg 768w,https://scitechdaily.com/images/Ultra-Faint-Dwarf-Galaxy-Pegasus-V-Circled-1536×783.jpg 1536w,https://scitechdaily.com/images/Ultra-Faint-Dwarf-Galaxy-Pegasus-V-Circled.jpg 1992w” sizes=”(max-width: 777px) 100vw, 777px” ezimgfmt=”rs rscb1 src ng ngcb1 srcset” data-ezsrc=”https://scitechdaily.com/images/Ultra-Faint-Dwarf-Galaxy-Pegasus-V-Circled-777×396.jpg”/>
Das Bild wurde mit der Dark Energy Camera des US-Energieministeriums am Víctor M. Blanco 4-Meter-Teleskop am Cerro Tololo Inter-American Observatory (CTIO) aufgenommen. Die Daten wurden über die Community Pipeline verarbeitet, die vom Community Science and Data Center (CSDC) von NOIRLab betrieben wird.
Faint stars in Pegasus V were discovered in subsequent deeper observations by astronomers using the larger 8.1-metre Gemini North telescope with the GMOS instrument, confirming that it is an ultrafaint dwarf galaxy on the outskirts of the Andromeda galaxy. Gemini North in Hawaii is one half of the International Gemini Observatory.
Observations with Gemini showed that the galaxy appears to be extremely deficient in heavier elements compared to similar dwarf galaxies, meaning it is very old and likely a fossil of the first galaxies in the universe.
“We have found an extremely faint galaxy whose stars formed very early in the history of the Universe,” commented Michelle Collins, an astronomer at the University of Surrey, UK, and lead author of the paper announcing the discovery. “This discovery is the first time such a faint galaxy around the Andromeda galaxy has been found using an astronomical survey not specifically designed for this task.”
A unique ultrafaint dwarf galaxy has been spotted on the outer edge of the Andromeda galaxy, thanks to the keen eyes of an amateur astronomer examining archive data from the US Department of Energy-manufactured Dark Energy Camera on the Victor M. Blanco 4-meter telescope at the Cerro Tololo Inter-American Observatory (CTIO) and processed by the Community Science and Data Center (CSDC). Follow-up studies by professional astronomers using the International Gemini Observatory found that the dwarf galaxy – Pegasus V – contains very few heavier elements and is likely a fossil of the first galaxies. All three institutions involved are programs of the NSF’s NOIRLab. Image Credits: International Gemini Observatory/NOIRLab/NSF/AURA Acknowledgments: Image Processing: TA Rector (University of Alaska Anchorage/NSF NOIRLab), M. Zamani (NSF NOIRLab) & D. de Martin (NSF NOIRLab)
The faintest galaxies are thought to be fossils of the very first galaxies to form, and these galactic relics hold clues to the formation of the earliest stars. While astronomers assume the universe is teeming with faint galaxies like Pegasus V,[2] They haven’t discovered nearly as many as their theories predict. If there really are fewer faint galaxies than predicted, it would pose a serious problem with astronomers’ understanding of cosmology and dark matter.
Discovering specimens of these faint galaxies is therefore an important endeavor, but also a difficult one. Part of the challenge is that these faint galaxies are extremely difficult to spot, appearing as just a few stars hidden in vast images of the sky.
“The problem with these extremely faint galaxies is that they have very few of the bright stars that we typically use to identify them and measure their distances,” explains Emily Charles, a PhD student at the University of Surrey who also works was involved in the study. “Gemini’s 8.1-meter mirror allowed us to find faint, old stars, allowing us to both measure the distance to Pegasus V and determine that its stellar population is extremely old.”
The heavy concentration of old stars the team found in Pegasus V suggests the object is likely a fossil of the first galaxies. Compared to the other faint galaxies around Andromeda, Pegasus V appears to be uniquely old and metal-poor, suggesting that its star formation did indeed stop very early.
“We hope that further study of the chemistry of Pegasus V will provide clues to the earliest periods of star formation in the Universe,” Collins concluded. “This small fossil galaxy from the early Universe could help us understand how galaxies form and whether our understanding of dark matter is correct.”
“The public-facing Gemini North telescope offers a number of opportunities for community astronomers,” said Martin Still, Gemini program officer at the National Science Foundation. “In this case, Gemini assisted this international team to confirm the presence of the dwarf galaxy, physically associate it with the Andromeda Galaxy, and determine the metal deficiency of its evolved stellar population.”
Upcoming astronomical facilities should shed more light on faint galaxies. Pegasus V witnessed a period in the history of the Universe known as reionization, and other objects from that period will soon be observed with NASA’s James Webb Space Telescope. Astronomers also hope to discover more such faint galaxies in the future with the Vera C. Rubin Observatory, a program of NSF’s NOIRLab. The Rubin Observatory will conduct an unprecedented, decades-long survey of the optical sky called the Legacy Survey of Space and Time (LSST).
Remarks
- The DESI Legacy Imaging Surveys were conducted to identify targets for operation of the Dark Energy Spectroscopic Instrument (DESI). These surveys comprise a unique mix of three projects that have observed one-third of the night sky: the Dark Energy Camera Legacy Survey (DECaLS), that of the DOE-built Dark Energy Camera (DECam) on the 4-meter Víctor M. Blanco was observed telescope at the Cerro Tololo Inter-American Observatory (CTIO) in Chile; the Mayall z-band Legacy Survey (MzLS) by the Mosaic3 camera on the Nicholas U. Mayall 4-meter telescope at Kitt Peak National Observatory (KPNO); and the Beijing-Arizona Sky Survey (BASS) by the 90Prime camera on the Bok 2.3-meter telescope owned and operated by the University of Arizona and located at KPNO. CTIO and KPNO are programs of the NSF’s NOIRLab.
- Pegasus V is so named because it is the fifth discovered dwarf galaxy in the constellation Pegasus. The distance in the sky between Pegasus V and the Andromeda galaxy is about 18.5 degrees.
More information
This research was presented in a paper titled “Pegasus V – a newly discovered ultrafaint dwarf galaxy on the outskirts of Andromeda”. Monthly Bulletins of the Royal Astronomical Society.
Reference: “Pegasus V – A Newly Discovered Ultrafaint Dwarf Galaxy on the Outskirts of Andromeda” by Michelle LM Collins, Emily JE Charles, David Martínez-Delgado, Matteo Monelli, Noushin Karim, Giuseppe Donatiello, Erik J. Tollerud and Walter Boschin , accepted, Monthly Bulletins of the Royal Astronomical Society.
arXiv:2204.09068
The team consists of Michelle LM Collins (Faculty of Physics, University of Surrey, UK), Emily JE Charles (Faculty of Physics, University of Surrey, UK), David Martínez-Delgado (Instituto de Astrofísica de Andalucía, Spain), Matteo Monelli (Instituto de Astrofísica de Canarias (IAC) and Universidad de La Laguna, Spain), Noushin Karim (Faculty of Physics, University of Surrey, UK), Giuseppe Donatiello (UAI – Unione Astrofili Italiani, Italy), Erik J. Tollerud (Space Telescope Science Institute, USA), Walter Boschin (Instituto de Astrofísica de Canarias (IAC), Universidad de La Laguna and Fundación G. Galilei – INAF (Telescopio Nazionale Galileo), Spain).