Probing Galactic Central Region of Normal Galaxies with

Photometric Method

August, 27 , 2002

Student Yeong-jyi Lei

Advisor Chi Yuan

Chien-Chang Yen

OutlineIntroduction of Hubble sequence

Our candidates

Photometric method :Wavelet method

Observation results

Compare our result with other photometrical method

Conclusion

Hubble Tuning-fork Diagram

Typical Early-Type galaxies

IC 4296(E0) NGC 4365(E3) NGC4564(E6)

NGC 4623(E7) NGC 4251(S0) NGC 4340(SB0)

Typical normal Spirals

NGC4736(Sb)NGC3898(Sa)

NGC4321(Sc) NGC4594(Sa/Sb)

Typical Barred Spirals

NGC 175 (SBab) NGC 1300 (SBb) NGC 2525(SBc)

candidates

• Our candidates are from the list of 183 disk galaxies, they are proposed by Luis Ho.

• We choose the well-observed data, which have two properties: they are almost face-on and their origins are nearly in the center of images. (33 normal galaxies)

Introduction to wavelet method

+ +

= Wavelet

Wavelet method provides us a multi-scale analysis. It decomposes data at some certain scale into different planes Wj , j=0,1,2,3,4,5,… . When we say wavelet planes 1 to 4, meaning

W1+W2+W3+W4. The following is a numerical example:

NGC1667(Sc)

NGC4321(Sc)

NGC5055(Sbc)

NGC5005(Sb)

NGC5806(Sb)

NGC4698(Sa)

NGC4459(S0)

NGC3412(S0)

Clear spiral Not clear No spiral

S0 1 6

Sa 1 5

Sab 1

Sb 2 4

Sbc 2 3 1

Sc 5 2

Compare our result with other photometrical method

(NGC7743 SBa)

Conclusion

• There is usually no spiral structure in the central region for Sa(S0) type and clear spiral structure for Sc type.

• The evolution of normal galactic from Sc to Sa can be suggested by our observation.