Morphological Classification of Galaxies: Properties and Structure Analysis
This seminar focuses on the morphological properties of galaxies, intricately exploring their classifications using the Hubble sequence. We discuss key features such as ellipticity, the transition from early-type to late-type galaxies, and the implications of inclination and viewing angles on barred and non-barred structures. The lecture references significant works including Buta (2011) and Roberts & Haynes (1994), examining profiles like the Sersic and luminosity functions across different galaxy types. The understanding of bulge structures and their dynamics is also highlighted, emphasizing the difference between classical bulges and pseudo-bulges.
Morphological Classification of Galaxies: Properties and Structure Analysis
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Presentation Transcript
Galactic Astronomy銀河物理学特論 ILecture 1-3: Morphological properties of galaxiesSeminar: Strateva et al. 2001, AJ, 122, 1861 Lecture: 2011/10/31
Morphological Classification SDSS galaxies Buta, 2011, arXiv:1102.0550
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.
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 Sersic 1963, 1968 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
