The Development of a Detailed Abundance Analysis Method Intended for theIntegrated Light Spectra of Extragalactic Globular Clusters.

[摘要] Globular
 clusters
 are
 stellar
 systems
 that
 possess
 an
 astrophysically
 rare
 combination
 of
 theoretical
 and
 observational
 simplicity,
 which
 make
 them
 ideal
 diagnostic
 tracers 
of
 astrophysical
 processes 
in 
both
 space
 and
 time.

 Capitalizing 
on
 this
 simplicity,
 this
 dissertation
 develops
 and
 demonstrates
 a
 detailed
 abundance
 analysis 
method
 that 
is
 capable 
of
 computing 
all
 observable
 line
 abundances
 (i.e. 
Fe‐ peak
 elements,
 alpha‐elements,
 neutron‐capture
 elements,
 and
 light‐elements) 
from
 the
 integrated
 light
 spectra
 of
 extragalactic
 globular
 clusters
 (GCs).
 
 The
 premise
 behind
 the
 method
 is
 that
 the
 precise
 and
 accurate
 techniques
 used
 for
 single
 star
 abundance
 analysis
 can
 be
 combined
 with
 theoretical
 simple
 stellar
 population
 (SSP)
 models
 to
 synthesize
 light‐weighted
 absorption
 line
 equivalent
 widths
 (EWs).
 By
 iterating 
on
 the
 assumed
 abundance
 for
 a
 line 
until 
its 
synthesized 
EW
 equals
 its
 observed
 EW
 allows
 its
 line
 abundance
 to
 be
 determined.
 
 The
 development

 and demonstration of
 this
 method
 is
 carried
 out
 using
 a
 training
 set
 of
 seven
 Milky
 Way
 GCs
 (NGC
104,
 NGC
362,
 NGC
2808,
 NGC
6093,
 NGC
6388,
 NGC
6397,
 NGC
6752),
 which
 were
 observed
 using
 a
 spectrograph
 scanning
 technique
that
 produces
 integrated
 light
 spectra
 that
 mimic
 extragalactic
 GC
 spectra.
 
 The
 role
 of
 the
 training
 set
 is
 two
 fold.
 
 First,
 because
 the
 training
 set
 clusters
 are
 spatially
 resolved,
 their
 stellar 
populations
 are
 known
 a
 priori 
in
 the
 form
 of 
color‐magnitude
 diagrams.
 
 The
 use
 of
 these
 known
 stellar
 populations
 in
 the
 analysis
 method
 serve
 to
 initially
 test
 the
 feasibility
 of
 the
 method
 without
 encountering
 any
 of
 the
 potential 
complications
 that 
may
 stem
 from
 using
 theoretical
 SSPs.

 Second,
 because
 the
 clusters
 are
 spatially
 resolved,
 their
 stellar
 abundances
 are
 known
 a
 priori from
 single
 star
 abundance
 analysis.
 These
 stellar
 abundances
 critically
 serve
 as
 fiducial
 abundances
 against
 which
 the
 dissertation;;s
 abundance
 results
 are
 tested.
 
 The
 major
 conclusion
 from
 this
 dissertation
 is
 that
 its
 abundance
 analysis
 method
 using
 theoretical
 SSPs
 is
 capable
 of
 deriving
 the
 detailed
 abundances
 of
 extragalactic
 GCs
 with
 an
 accuracy
 and
 precision
 that
 are
 competitive
 with
 standard
 stellar
 abundance 
analysis. 


The 
method 
produces
 abundances 
that
 are
 on
 average
 only

 <
 0.1
 dex larger
 than
 the
 abundances
 from
 stellar
 analysis,
 and
 their
 statistical
 uncertainties
 are 
on
 average
 ~
0.2
 dex.


[发布机构] University of Michigan

[效力级别] Extragalactic

[关键词] Globular Clusters;Extragalactic;Abundances;Integrated Light Spectra;Galactic;Milky Way;Astronomy;Science;Astronomy and Astrophysics