(Phys.org)—An international team of astronomers led by
Behnam Javanmardi of the University of Bonn in
Germany has recently discovered 11 low surface
brightness (LSB) systems located around nearby spiral
galaxies. The researchers used small amateur telescopes
to scan the sky around large galaxies and successfully
obtained the images of their dim companions. A paper
reporting the findings appeared last week on the ArXiv
pre-print server.
The research is a part of the Dwarf Galaxy Survey with
Amateur Telescopes (DGSAT) project. Its main goal is to
complete the census of very faint dwarf satellites around
spiral galaxies. Prior to the latest results, the project
proved its efficiency by discovering tidal stellar streams,
also around several nearby spiral galaxies.
By publishing the latest findings, Javanmardi and his
colleagues have demonstrated that a search for LSB
objects can be successfully performed with a telescope
of small diameter, from 0.1 to 1 meter, having a wide
field of view. The DGSAT observations were conducted
with a network of privately owned robotic observatories
equipped with modest-sized telescopes located in
Europe, the United States, Australia and Chile.
"We developed a semi-automatic pipeline to calibrate
the luminance images taken by amateur telescopes,
search for dwarf galaxy candidates and extract their
observed parameters. By exploring the fields of six
nearby massive galaxies NGC 2683, NGC 3628, NGC 4594
(M104), NGC 4631, NGC 5457 (M101), and NGC7814, we
discovered eleven so far unknown LSB galaxies in our
images," the paper says.
For instance, the team pointed a 0.4-meter Newton
telescope at the NGC 2683. The observations, conducted
from February to March this year at the ROSA
Observatory in France, allowed the researchers to spot
new faint LSBs around NGC 2683. However, the largest
number of new LSBs was detected in the field of the
NGC 5457 galaxy. This galaxy was also observed by the
same telescope at the ROSA Observatory, but in 2014.
LSBs are diffuse galaxies with a surface brightness at
least one magnitude lower than the ambient night sky.
Most LSBs are dwarf galaxies consisting of up to several
billion stars. Dwarf satellite galaxies are the most
common type of galaxies in the universe and are crucial
for astronomers in testing different models of galaxy
formation and evolution.
The newly discovered LSBs have similar properties to
the known dwarf galaxies of the Local Group containing
our home Milky Way galaxy. Nevertheless, the research
shows that further observations are required to be one
hundred percent sure that the discovered objects are
really dwarf satellites of their nearby galaxies.
"All of the detected objects have very low surface
brightness and cannot be detected in the available
images from large scale surveys like the Sloan Digital
Sky Survey or PanSTARRs. This also makes it very
difficult to undertake follow-up observations to obtain
their radial velocities and to confirm their association
with the spiral galaxies even for 8-meter class
telescopes," the researchers write in the paper.
They concluded that the major benefit of this study is
showing the potential of amateur telescopes in
discovering more dwarf galaxies. More findings could
help test models of galaxy formation and evolution
outside the Local Group.
Behnam Javanmardi of the University of Bonn in
Germany has recently discovered 11 low surface
brightness (LSB) systems located around nearby spiral
galaxies. The researchers used small amateur telescopes
to scan the sky around large galaxies and successfully
obtained the images of their dim companions. A paper
reporting the findings appeared last week on the ArXiv
pre-print server.
The research is a part of the Dwarf Galaxy Survey with
Amateur Telescopes (DGSAT) project. Its main goal is to
complete the census of very faint dwarf satellites around
spiral galaxies. Prior to the latest results, the project
proved its efficiency by discovering tidal stellar streams,
also around several nearby spiral galaxies.
By publishing the latest findings, Javanmardi and his
colleagues have demonstrated that a search for LSB
objects can be successfully performed with a telescope
of small diameter, from 0.1 to 1 meter, having a wide
field of view. The DGSAT observations were conducted
with a network of privately owned robotic observatories
equipped with modest-sized telescopes located in
Europe, the United States, Australia and Chile.
"We developed a semi-automatic pipeline to calibrate
the luminance images taken by amateur telescopes,
search for dwarf galaxy candidates and extract their
observed parameters. By exploring the fields of six
nearby massive galaxies NGC 2683, NGC 3628, NGC 4594
(M104), NGC 4631, NGC 5457 (M101), and NGC7814, we
discovered eleven so far unknown LSB galaxies in our
images," the paper says.
For instance, the team pointed a 0.4-meter Newton
telescope at the NGC 2683. The observations, conducted
from February to March this year at the ROSA
Observatory in France, allowed the researchers to spot
new faint LSBs around NGC 2683. However, the largest
number of new LSBs was detected in the field of the
NGC 5457 galaxy. This galaxy was also observed by the
same telescope at the ROSA Observatory, but in 2014.
LSBs are diffuse galaxies with a surface brightness at
least one magnitude lower than the ambient night sky.
Most LSBs are dwarf galaxies consisting of up to several
billion stars. Dwarf satellite galaxies are the most
common type of galaxies in the universe and are crucial
for astronomers in testing different models of galaxy
formation and evolution.
The newly discovered LSBs have similar properties to
the known dwarf galaxies of the Local Group containing
our home Milky Way galaxy. Nevertheless, the research
shows that further observations are required to be one
hundred percent sure that the discovered objects are
really dwarf satellites of their nearby galaxies.
"All of the detected objects have very low surface
brightness and cannot be detected in the available
images from large scale surveys like the Sloan Digital
Sky Survey or PanSTARRs. This also makes it very
difficult to undertake follow-up observations to obtain
their radial velocities and to confirm their association
with the spiral galaxies even for 8-meter class
telescopes," the researchers write in the paper.
They concluded that the major benefit of this study is
showing the potential of amateur telescopes in
discovering more dwarf galaxies. More findings could
help test models of galaxy formation and evolution
outside the Local Group.
