Quasar main sequence in the UV plane. (arXiv:1810.09363v2 [astro-ph.HE] UPDATED)
<a href="http://arxiv.org/find/astro-ph/1/au:+Sniegowska_M/0/1/0/all/0/1">Marzena Śniegowska</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kozlowski_S/0/1/0/all/0/1">Szymon Kozłowski</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Czerny_B/0/1/0/all/0/1">Bożena Czerny</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Panda_S/0/1/0/all/0/1">Swayamtrupta Panda</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Hryniewicz_K/0/1/0/all/0/1">Krzysztof Hryniewicz</a>
Active galaxies form a clear pattern in the optical plane showing the
correlation between the Full Width Half Maximum (FWHM) of the H$beta$ line and
the ratio of the Equivalent Width (EW) of the optical FeII emission and the
EW(H$beta$). This pattern is frequently refereed to as the quasar main
sequence. In this paper we study the UV plane showing FWHM of the MgII line
against the ratio of EW of UV FeII emission to EW(MgII). We show that the UV
plane trends are different, with the underlying strong correlation between
FWHM(MgII) and EW(MgII). This correlation is entirely driven by the choice of
the continuum used to measure EW(MgII). If we correct for the strong curvature
in the UV continuum related to the character of emission expected from
accretion disk, the behavior of the FWHM vs. EW for MgII becomes similar to the
behaviour of H$beta$. Such a similarity is expected since both lines belong to
the Low Ionization group of emission lines and come from a similar region. Such
a similarity and weak coupling between FWHM and EW of the corresponding line is
then also consistent with the Broad Line Region model based on the presence of
dust in the accretion disk atmosphere.
Active galaxies form a clear pattern in the optical plane showing the
correlation between the Full Width Half Maximum (FWHM) of the H$beta$ line and
the ratio of the Equivalent Width (EW) of the optical FeII emission and the
EW(H$beta$). This pattern is frequently refereed to as the quasar main
sequence. In this paper we study the UV plane showing FWHM of the MgII line
against the ratio of EW of UV FeII emission to EW(MgII). We show that the UV
plane trends are different, with the underlying strong correlation between
FWHM(MgII) and EW(MgII). This correlation is entirely driven by the choice of
the continuum used to measure EW(MgII). If we correct for the strong curvature
in the UV continuum related to the character of emission expected from
accretion disk, the behavior of the FWHM vs. EW for MgII becomes similar to the
behaviour of H$beta$. Such a similarity is expected since both lines belong to
the Low Ionization group of emission lines and come from a similar region. Such
a similarity and weak coupling between FWHM and EW of the corresponding line is
then also consistent with the Broad Line Region model based on the presence of
dust in the accretion disk atmosphere.
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