1. The Nuclear Regions of Nearby Galaxies
Kyungpook National University
Yun Hee Lee and Myeong-Gu Park

2. CONTENTS INTRODUCTION SAMPLE & DATA REDUCTION ANALYSIS CONCLUSIONS
INDIVIDUAL GALAXIES
CONCLUSIONS

3. 1. INTRODUCTION Importance of the systematic study on nuclear region
Galactic center influences on the current nature, the formation and fate of the Milky Way (Lee 2005)
Strong connections in extragalaxies:
Central black holes - Velocity dispersion
- Halo circular velocity
- Dark matter halo mass
- Light concentration
(Ferrarese & Merritt 2000; Bullock et al. 2001;
Ferrarese 2002; Graham et al. 2001)

4. 1. INTRODUCTION - offset Nieto et al. 1986 Lauer et al. 1993
0.4 arcsec offset
2.4 arcsec offset
Nieto et al. 1986
Lauer et al. 1993

5. 2. SAMPLE & DATA REDUCTION
Bright & Nearby galaxies
: Messier’s Galaxies(40)
HST/WFPC2 – PC : 0.045”/pixel
V & I images – color gradient
1. Type (25/40)
Elliptical : 8
Spiral : 16
Lenticular : 1
2. Distance : 0.8 ~ 22.4 Mpc

6. 2. SAMPLE & DATA REDUCTION
1. Combine
: to remove bad pixels & cosmic rays
(STSDAS/wfpc/combine)
2. Normalize (Dolphin 2000)
3. Correct the geometric distortion
(IRAF/digiphot/daofind)
: 0.02 ~ 1.41 pixels

7. 3. ANALYSIS Morphology Centroid Surface photometry Color Map
Kent(1983)/Jedrzejewsk(1987)
Stsdas/isophote/ellipse
Color Map
IRAF/imutil/imarith,imfunction
Surface Brightness Profile
γ≡ - dlogI/dlogr
γ < 0.3 : core galaxy
γ > 0.5 : power-law galaxy
0.3 < γ < 0.5 : intermediate
(Lauer et al. 2005)
Centroids (within r~1’’)
No offset galaxy < 1 pixel
Offset galaxy > 1 pixel

8. 3. ANALYSIS Core: 18 / Intermediate: 4 / power-law: 5
Offset: 17 / No offset: 8

9. 4. INDIVIDUAL GALAXIES (1)M32
cE2
No offset
Slight blue
Core size (0.3pc)
~106Mo BH at 0.3pc
(van der Marel et al. 1997)
Rapid up in P.A /ε
A dim red ring

10. 4. INDIVIDUAL GALAXIES (2)M33Sc
Asymmetric properties
: Centroids/ Velocity fields
(Colin & Athanassoula 1981)
Power-law galaxy
No offset
Blue
Supposed, ~10Mo BH binary (Knox et al. 2002)
Rapid Slope

11. 4. INDIVIDUAL GALAXIES (3)M51
LINER/ Sc
X-shape dust lane
(Maran & Kiney 1993)
Low-level emission of Hα/radio (Grillmair et al. 1997)
Suggested, molecular gas by a jet of ten pc scale and a warped disk of two rings (Matsushita et al. 2007)
Core galaxy (7pc)
Like M31
1) offset-opposite direction
2) P1 < P2

12. 4. INDIVIDUAL GALAXIES (4)M58
LINER/ Sy1.9/ SAB
Symmetric rotation curve
(Palacios et al. 1997)
Power-law galaxy
Offset
Blue
Dim spiral-like dust feature
Small ups and downs

13. 4. INDIVIDUAL GALAXIES (5)M59
108Mo BH
(Merrit & Ferrarese 2001)
Two-component structure
(Bender 1988)
Asymmetry: velocity dispersion
(Bender 1990)
60pc KDC (Wernli et al. 2002)
Intermediate galaxy
No offset
Rapid up / transition
Red region near core

14. 4. INDIVIDUAL GALAXIES (6)M85SA
Resemble M31 : double nuclei
Central minimum
Asymmetry
Twisted (Lauer et al. 2005)
Recent merger candidates
(Schweizer & Seitzer 1992)
Boxy structure/ KDC
(McDermid et al. 2006)
A bit central minimum
Core galaxy (20pc)
Offset
Slightly blue
Small ups and downs
Polar colors

15. 4. INDIVIDUAL GALAXIES (7)M86
S0/E3
Gravitational interaction with neighboring galaxies
Asymmetry : X-ray, FIR, Optical
(Manfred Stickel 2003)
KDC (Bender 1988)
Central minimum : 0.07mag
(Lauer et al. 2002)
Core galaxy (80pc)
Nearly no offset

16. 4. INDIVIDUAL GALAXIES (8)M89
LINER/Sy2/ E
Ram pressure stripping by galaxy gas (Machacek et al. 2006)
MAS core radio source
Pc-scale extension structures
(Nagar et al. 2002)
~108Mo BH (Filho et al. 2004)
Core galaxy (30pc)
Offset
Spiked peak
Rapid up
Red region

17. 4. INDIVIDUAL GALAXIES (9)M98
Sy/ SAB
Double peaks : 0’’.25 (20pc)
Core galaxy (20pc)
Offset
Red
Rapid up/ small up
Line connecting the peaks // Major axis of the whole galaxy

18. 4. INDIVIDUAL GALAXIES (10)M104
LINER/Sy1.9/SA
Sombrero/ multi-component structure
Pointlike source (Crane et al. 1993)
~109Mo BH (Kormendy et al. 1996)
Core galaxy (50pc)/ not flat
Offset/ A lopsided peak
Slightly red
Extended red region

19. 5. CONCLUSIONS The central regions are tangled with various phenomena.
Most galaxies are offset in the most central regions.
Central offset phenomena are not coincident with the asymmetry properties of the whole galaxy.
The Hubble type seems to influence on the central offset as well as the offset of the whole galaxy.
AGN or LINER seem to be associated with the central offset.
Multiple nuclei can produce the central offset.

20. 5. CONCLUSIONS
3. Multiple peaks of M51 and M98 seem to be significant physically.
4. All surface photometry results seem to be meaningful.
Existence of SMBH : rapid peak in P.A and ε
Multiple peaks : ups and downs in P.A and ε
The border line of KDC : transition in P.A and ε
5. Observations of the center of nearby galaxies with high resolution are needed.