info:eu-repo/semantics/doctoralThesis
Integral spectroscopy of HII regions in spiral galaxies
Autor
JESUS LEONARDO LOPEZ HERNANDEZ
Resumen
As an observational science, astronomy is benefited from technological developments
that allow improvements in the way light is gathered and analyzed.
Integral field spectroscopy (IFS) is a modern observational technique that
allows to simultaneously obtain spectroscopic and spatial information on a
given area on the sky. In this work IFS is used to observe extragalactic Hii
regions in the nearby and face on spiral galaxies M33 and M101.
For M33 the central zone was observed together with the external region
IC 132, located ∼4.7kpc away from the galaxy center, the PMAS instrument
was used in the 3.5m telescope at the Calar Alto (CAHA) observatory.
For M101 observations where gathered with the GMOS-N instrument at the
Gemini 8m telescope in Mauna Kea. The distance to each galaxy, in combination
with the field of view of each instrument gives a similar spatial
sampling for both sets of regions. Reduction was performed with the tools
provided by the telescopes. In the case of PMAS the packages R3D and E3D
were used while for GMOS-N the reduction was based on the Gemini routines
for IRAF. Additional corrections to compensate for differential atmospheric
refraction and atmospheric telluric absorption were applied.
With the reduced and corrected data, 2D maps were produced. These
maps were in turn used to estimate the distribution of physical conditions
along the nebulae, as well as the ionic and total abundances from the direct
method, together with empirical indicators based in strong lines. Ionization
structure was studied with the ionization sensitive ratios [OIII]/Hβ, [NII]/Hα
and [SII]/Hα. The 2D maps where complemented with zones analysis where
the regions are divided in shells of equal integrated Hα surface brightness.
Given the Hα distribution this is equivalent to a radial analysis. The shells
are studied first as single entities and then adding them from the center to
the border, simulating increasing apertures.
The BPT diagnostic diagram show different locations for the regions, with
some spatial resolution elements (spaxels), crossing the stellar photoionization
boundaries. These spaxels are part of the diffuse ionized gas (DIG)
beyond the Str¨omgren sphere limits, nevertheless this indicates extra precaution
required for the use of BPT diagnostic diagram with spatially resolved data.
Materias
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