Extinction studies
9/?/05
Point-to-point comparison between
Av
derived from JHK colors
(Tracy) and SED fitting (Shih-Ping) Plot
- Using JHK only, Av from two methods are consistent with
each other
- Av derived from 2MASS + Spizer data with SED fitting
differ from Av derived from 2MASS data only, which indicating the
change of extinction law in Spitzer bands
10/13/05
Experiments for spectral type fitting
Sample : 100 stars with 10% random
Gaussian
noise to stellar SED models for 14 main sequnce types
Using my SED fitting program to compare the input
and output spectral types and Av
- Distribution of output spectral
types spec_histo.ps
- Av vs. Output Spectral typpes spec_Av.ps
- Histogram of output Av for each input spectral types spec_Av_histo.ps
The output Av distribution centered at the input Av value, and the distribution is gaussian-like.
- Histogram of output Av for each input spectral
types, but
using only specific spectral type for the SED fitting spec_Av_histo2.ps
This show you fitting a single spectral or the average SED introduce a systematic error.
It is not obvious that the systematics will be canceled out by adding more stars.
- Histogram of output Av for sample with output
spectral types of
K5,M0, and M2 output_K5-M2.ps
Note: the input sample contains the same number of stars for each spectral types.
In reality the input K5-M2 component should be much bigger than the input B0-K0 component
What we learn:
- KM stars can be separated from everything else
- Fitting spectral types does NOT give you
reliable spectral type
information for O-G stars
- Av from fitting spectral types show normal
distribution centered
at the input Av value
- Av from fitting specific spectral type or the
average spectral
type introduce systematic shift
Conclusion(?) :
- Fitting spectral types reduce systematic errors
- Since KM stars can be more reliably determined, we can use
them
to caculate extinction laws and intrinsic standard deviataion of
Av