Spectroscopic Studies of Fermi LAT Blazars
Saario, Joonas (2016-06-15)
Spectroscopic Studies of Fermi LAT Blazars
Saario, Joonas
(15.06.2016)
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Turun yliopisto
Kuvaus
Siirretty Doriasta
Tiivistelmä
Blazar research offers a view to one of the most energetic physical processes known
to man. The high-energy end of blazar emission has been probed by the Fermi
satellite mission since 2008, and it has catalogued more than a thousand gamma-
ray bright blazars. However, a large fraction of these sources have no spectroscopic
classification at lower energies.
In this thesis, optical spectra for sixteen Fermi blazar candidates are published. The
optical spectroscopic data have been observed with the Nordic Optical Telescope on
the island of La Palma, Spain, during the summer of 2015. The ALFOSC instrument
was used, with exposure times from 800 to 3000 seconds per target, yielding signal-
to-noise ratios from 10 to 38.
All of the sixteen targets show a flat, featureless optical spectrum, characteristic to
BL Lacertae objects. The spectra of two targets contain faint emission features, and
faint absorption features are seen in three targets. However, none of the features
could be reliably identified.
Therefore all of the targets are classified as BL Lacertae objects. This classification
is supported by the statistical distribution of Fermi -selected active galactic nuclei;
more than half of the identified Fermi AGN are BL Lacs. However, the classification
of this sample could be improved further with a new observing campaign. This is
especially true for the objects with uncertain spectral features.
to man. The high-energy end of blazar emission has been probed by the Fermi
satellite mission since 2008, and it has catalogued more than a thousand gamma-
ray bright blazars. However, a large fraction of these sources have no spectroscopic
classification at lower energies.
In this thesis, optical spectra for sixteen Fermi blazar candidates are published. The
optical spectroscopic data have been observed with the Nordic Optical Telescope on
the island of La Palma, Spain, during the summer of 2015. The ALFOSC instrument
was used, with exposure times from 800 to 3000 seconds per target, yielding signal-
to-noise ratios from 10 to 38.
All of the sixteen targets show a flat, featureless optical spectrum, characteristic to
BL Lacertae objects. The spectra of two targets contain faint emission features, and
faint absorption features are seen in three targets. However, none of the features
could be reliably identified.
Therefore all of the targets are classified as BL Lacertae objects. This classification
is supported by the statistical distribution of Fermi -selected active galactic nuclei;
more than half of the identified Fermi AGN are BL Lacs. However, the classification
of this sample could be improved further with a new observing campaign. This is
especially true for the objects with uncertain spectral features.