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ON THE RELATION BETWEEN CIRCULAR VELOCITY AND CENTRAL VELOCITY
DISPERSION IN HSB AND LSB GALAXIES
E.M. Corsini, A. Pizzella, E. Dalla Bontà, F.BertolaDipartimento di Astronomia, Università di Padova, Italy
L. Coccato Kapteyn Astronomical Institute, Groningen, The Netherlands
M. SarziPhysics Department, University of Oxford, UK
Introduction
A possible relation between bulge c and disk Vc was found by Whitmore et al. (1979) studying a sample of spiral galaxies. They inferred from Vc / c 1.7 that halo and bulge are dynamically separate components.
Introduction
A possible relation between bulge c and disk Vc was found by Whitmore et al. (1979) studying a sample of spiral galaxies. They inferred from Vc / c 1.7 that halo and bulge are dynamically separate components.
Gerhard et al. (2001) derived the Vc- c relation for a sample of giant, nearly round and almost non-rotating ellipticals. It was explained as an indication of near dynamical homology of these galaxies,
Introduction
A possible relation between bulge c and disk Vc was found by Whitmore et al. (1979) studying a sample of spiral galaxies. They inferred from Vc / c 1.7 that halo and bulge are dynamically separate components.
Gerhard et al. (2001) derived the Vc- c relation for a sample of giant, nearly round and almost non-rotating ellipticals. It was explained as an indication of near dynamical homology of these galaxies.
Ferrarese (2002) and Baes et al. (2003) found that ellipticals and spirals define a common Vc- c relation. It was interpreted as a relation between the mass of the DM halo and SMBH.
Sample selection
We enlarged the sample so far studied, namely
38 Sa-Scd = Ferrarese 2002; optical/HI RC’s from literature
12 Sb-Sc = Baes et al. 2003; optical RC’s
20 E0-E2 = Kronawitter et al. 2000; stellar dynamics
by including
17 S0/a-Sab = Corsini et al. 1999, 2003; optical RC’s
33 Sb-Sbc = Vega et al. 2001; Pizzella et al. 2004; optical RC’s
11 LSB Sa-Sc = Pizzella et al. 2005; optical RC’s
5 E’s = Bertola et al. 1993; HI RC’s from literature
Measuring Vc
E’s: from either the flat part of HI RC or dynamical modeling
to test against model-depend biases
HSB/LSB’s: from the flat part of gas RC
V(R) = A R + B with |A| 2 km s-1 kpc-1 for R 0.35 R25
instead of Vc = V(Rlast) with Rlast R25
Measuring c
E’s: from aperture measurements of the stellar velocity
dispersion corrected to re/8
HSB/LSB’s: from stellar velocity dispersion profile with no
aperture correction
The Vc-c relation for HSB’s and E’s
The sample consists of
40 HSB spirals (Rlast 0.8 R25 )
24 ellipticals 19 = Vc from stellar dynamics (Rlast 0.5 R25 )
5 = Vc from HI kinematics (Rlast 3 R25 )
We fitted a straight line to the data of HSB’s and E’s taking into
account the errors on Vc and c
The MBH - MDM relation
c is related to MBH
according to the MBH - c relation (Ferrarese & Ford 2004)
Vc is related to MDM
since Vc correlates with Vvir (e.g., Vc / Vvir = 1.8, Seljak 2002)
and Vvir determines MDM (e.g., Bullock et al. 2001)
the Vc- c relation translates into a MBH - MDM relation
with some caveats
MBH- c for spirals
MBH- c extrapolation to c 50 km/s
uncertainties in the MDM - Vc conversion
The Vc-c relation for LSB’s
The sample consists of
8 LSB spirals (Rlast 1.2 R25 )
According to KS test the distribution of normalized scatter of
LSB’s is different from that of HSB’s and E’s.
We fitted a straight line to the data of LSB’s taking into account
the errors on Vc and c
Conclusions
Vc - c relation for 40 HSB’s, 24 E’s, and 8 LSB’s with flat RC’s.
Vc - c relation for HSB’s is linear out to c 50 km/s.
E’s with Vc based on dynamical models or directly derived from
from HI RC’s follow the same relation as HSB’s.
LSB’s follow a different Vc- c relation. This suggests that DM
halos of LSB’s host smaller SMBH’s and were less affected by baryon collapse with respect to their HSB counterparts.