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.

Whitmore et al. 1979

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,

Gerhard et al. 2001

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.

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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

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NGC6925HSB Sbc

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ESO206-G14LSB Sc

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

warped

rising

asymmetric

not extended

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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

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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

ellipticalsHI ellipticalsHSB spirals

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

ellipticalsHI ellipticalsHSB spirals

ellipticalsHI ellipticalsHSB spiralsLSB spirals

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.

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ellipticalsHI ellipticalsHSB spirals

ellipticalsHI ellipticalsHSB spiralsLSB spirals