Galactic Astronomy 銀河物理学特論 I Lecture 1-3: Morphological properties of galaxies Seminar: Strateva et al. 2001, AJ, 122, 1861 Lecture: 2011/10/31

Morphological Classification SDSS galaxies Buta, 2011, arXiv:1102.0550

Morphological Classification Sequence of elliptical galaxies Ellipticity increases along the sequence, and goes up to E7. Morphological Classification Buta, 2011, arXiv:1102.0550 Effect of inclination angle, viewing angle Barred structure becomes difficult to be identified, ex. Milkey way galaxy. Edge-on galaxies Disk structure becomes thinner along the Hubble sequence.

Morphological Classification Barred vs. non-Barred galaxies Early-type barred galaxies sometimes show ring-like structure due to the orbital resonance (共鳴). Morphological Classification Buta, 2011, arXiv:1102.0550

Physical parameter along Hubble sequence Roberts & Haynes 1994, ARAA, 32, 115

Physical parameter along Hubble sequence Roberts & Haynes 1994, ARAA, 32, 115

Sersic profile fitting I(R)=Ie exp(-bn((R/Re)^(1/n)-1) With n=1 then I(R)=I’ exp(-bn(R/Re)) : exponential profile With n=4 then I(R)=Ie exp(-bn((R/Re)^1/4-1)) : r1/4 profile Exponential and r1/4 profiles are handled with one parameter n. Graham & Driver 2005

Luminosity Function of Each Morphological Type The dependence of the galaxy luminosity function is examined with ~1,500 galaxies from SDSS. Bright-end of the LF is dominated by E/S0 galaxies. Irr galaxies only appear in faint-end of the LF. Classification is also done with concentration parameter C=r50/r90. Nakamura et al. 2003, ApJ, 125, 1682

Bulge vs. Pseudo-bulge Bulge-like structures of late-type disk galaxies can be fitted with low Sersic index profile ~1, i.e. exponential-law. Such bulges are called psuedo-bulge. Buta, 2011, arXiv:1102.0550 Kormendy 2004, ARAA, 42, 603

Bulge vs. Pseudo-bulge Dynamics of pseudo-bulge can be dominated by rotation. Kormendy 2004, ARAA, 42, 603 Laurikainen et al. 2007, MNRAS, 381, 401

Fraction of Barred galaxies among disk galaxies Nair & Abraham 2010, ApJL, 714, L260

Fraction of Barred galaxies among S/Irr galaxies Lee et al. 2011, arXiv:1110.1933

Bar-structure and nuclear activity: Bar-structure can induce transportation of gas to the nuclear region (Noguchi 1988, A&A, 203, 259). Optical images of Narrow-Line Seyfert 1s (NLSy1) show that bar-structure is common among NLSy1. Ohta et al. 2007, ApJS, 169, 1