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EI2GYB > ASTRO 22.02.23 17:20l 102 Lines 5312 Bytes #999 (0) @ WW
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Subj: Italian Amateur Astronomer Discovers Dwarf Galaxies
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Sent: 230222/1427Z @:EI2GYB.DGL.IRL.EURO #:10822 LinBPQ6.0.23
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Italian Amateur Astronomer Discovers Dwarf Galaxies
By: Kit Gilchrist February 20, 2023
Three dwarf galaxies around the Sculptor Galaxy have come to light thanks to
the work of an amateur astronomer.
Between January and June 2020, as COVID-19 was sweeping the world, an amateur
astronomer living in the province of Brindisi in southern Italy made a series
of exhilarating discoveries.
Giuseppe Donatiello was poring over images made public by the Dark Energy
Survey (DES), which had scanned the southern sky from the Cerro Tololo
Inter-American Observatory in Chile. Amid the smattering of stars, gas, and
dust, he noticed first one, then two, then three new satellites of the Sculptor
Galaxy (NGC 253). Dwarf-size and spheroidal in shape, they had been overlooked
by the algorithm set up to spot them.
It isn't hard to see why. The starlight emitted from them is feeble, faint and
shrouded in a haze of interference from objects in the foreground and
background. Even the brightest regions are ultra-dim, as is common with dwarf
galaxies. Yet they were most assuredly there, and they appeared to be
affiliated with NGC 253.
The dwarfs were dubbed Donatiello II, III and IV. A previous quest to
photograph the major satellites of Andromeda (M31) had already led Giuseppe to
unearth Donatiello I, another far-off dwarf. Including two others in the Local
Group, his total count is now six.
A paper detailing the newest discoveries was published in collaboration with
David Martinez-Delgado (Institute of Astrophysics of Andalucˇa, Spain) and
others in 2021. David is "unique in the professional scenario" in terms of the
working relationships he maintains with amateur astronomers, remarks Giuseppe.
The study draws on the discoveries as well as additional data from the Dark
Energy Spectroscopic Instrument (DESI) Legacy Surveys, which combine DES data
with that from two other cameras located at Kitt Peak in Arizona. These data
aided the analysis by reducing the amount of noise obstructing the signal.
More recently, a different team headed up by Bur‡in Mutlu-Pakdil (Dartmouth
College), also in search of satellites of NGC 253, used the Hubble Space
Telescope to obtain images of a number of them. Among them was Donatiello II,
which they named Scl-MM-dw3. They thus independently corroborated Giuseppe's
discovery. Hubble, with its more precise measurements, was moreover able to
conclusively demonstrate Donatiello II's association with NGC 253 and rule out
the possibility that it was a background projection.
Studying the satellite dwarf galaxies arrayed around NGC 253 helps us build a
clearer understanding of how such systems function. The more complete the
census, the more accurate our conclusions will be.
The case is emblematic of the way in which dedicated amateurs, in synergy with
professionals, continue to push the boundaries of astronomical knowledge. Since
the dawn of the internet, institutions have placed large volumes of archived
data online, enabling anybody with a computer to comb through and participate
in what was previously an exclusive pursuit. Humans are natural image
processors and complement the scrutinizing capabilities of automatic detection
software.
Giuseppe has been looking skyward since being inspired at a young age, like so
many others, by the Apollo missions. Now he has many years of experience under
his belt.
Knowing what to look for is key, as imposter artifacts abound. "Before
venturing into a search, it is necessary to thoroughly study the morphology [of
dwarf galaxies] and their appearance," notes Giuseppe. "What make the
difference between an artifact and a promising source," he adds, "are
cross-checks and mental associations."
The work is at times arduous and requires "preparation, creativity, and an
acceptance that you will spend a lot of time potentially without any results,"
says Giuseppe. The rewards, however, are immense.
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