Toward a detailed view on the kinematics of intermediate luminosity early-type galaxies no

a r X i v :a s t r o -p h /0311607v 1 27 N o v 2003

Astron.Nachr./AN 32X (200X)X,XXX–XXX

Correspondence to :giovanni.covone@oamp.fr

tween the structural parameters and the radial trend in the mass-to-light ratios (M/L)using archive kinematic data up to ～6R e for an heterogeneous sample of ellipticals:faint/disky galaxies show small or null M/L radial gradients,i.e.,almost constant M/L,while bright/boxy objects have larger gradi-ents in agreement with a substantial amount of dark matter in the outskirts of those systems.In particular the evidence of a dearth of dark matter in the intermediate luminosity galaxies has been con?rmed by Romanowsky et al.(2003)using plan-etary nebulae (PNe)kinematics out to 4R e .Con?rmation of these preliminary results by new observations with larger PNe samples or new techniques is very important,since a possibly tight connection between structural properties and density environment (i.e.,the dark matter halo)where the galaxies have grown would deeply affect our understanding of galaxy formation and evolution.

The formation and evolution of these intermediate lumi-nosity galaxies with almost null M/L gradients is still not clear.As a class,disky galaxies can be considered close to the bulge dominated S0galaxies since disky isophotes could re?ect the presence of an embedded faint stellar disk (Capac-cioli 1987;Bender et al.1988).Scorza &Bender (1995)have shown that the information on both photometry and line pro-?le of a sample of disky galaxies is compatible with simple disk+bulge models where the two subcomponents have par-allel angular momenta.This latter evidence could be an hint of a contemporary evolution for these galaxies rather than a late accretion or merger events.

A.N.Covone and Napolitano:Kinematics of intermediate luminosity early-type galaxies1

1https://www.sodocs.net/doc/17495344.html,/instrument/vimos

2In the near future,it is planned that SAURON will operate also

in the range4500-7000?A,in order to cover also the Hαemission

line,but for the same set of z<0.01galaxies.

2Astron.Nachr./AN XXX(200X)X

3For NGC4697,Napolitano(2001)obtained a constant M/L in-tegrating the Jeans equations up to in?nity.

4In this respect,it is interesting to note that the MOND theory appears to be in agreement with the?ndings of Romanowsky et al. (Milgrom&Sanders2003).PNe with the integral?eld data.In Fig.1a smoothed version of the PNe radial velocity?elds Romanowsky et al.(2003) is shown:this is the kind of data which we expect to com-plement with the VIMOS-IFU observations.In particular we expect to obtain:

–a description of the?ne structure of the stellar kinemat-ics with a spatial resolution of0′′.67,mapping the line-of-sight rotation velocity V,velocity dispersionσv,and higher Gauss-Hermite coef?cients h3,h4.These maps can be quanti?ed via Fourier methods.

–the possibility to reveal the presence of subcomponents along the line-of-sight both from h3and h4distribution and possibly using the double-Gaussian?t as performed in Scorza&Bender(1995)5.

–the association between kinematical and photometrical structures(using reconstructed continuum image from IFU data)as well as better constraints on the intrinsic in-clination(see,e.g.,Verolme et al.2002).

For instance,with6VIMOS-IFU pointings it is possible to cover an area of81′′×54′′around NGC3379center,cor-responding to1.2R e×0.8R e with an average S/N of30in a total of14hours integration.In this area a sample of at least 60PNe is present,which is expected to be suf?cient for any check of consistency between kinematical estimates(Napoli-tano et al.2001).

Using such a full2D kinematical map,we expect to def-initely disclose the presence of any substructure that could affect the projected kinematics like faint disks seen at high in-clination,by means of the azimuthal modulation of the veloc-ity moments on the sky plane(for instance,a non-cylindrical rotation velocity in proximity of the main kinematical axis).

For the galaxies in Table1,Romanowsky et al.(2003) have applied a full spherical Schwarzshild orbit library method(Romanowsky&Kochanek2001)for modeling the PNe kinematics with different degree of anisotropy.Such a

A.N.Covone and Napolitano:Kinematics of intermediate luminosity early-type galaxies3

galaxy Type V sys R e M B a4γΓB5reference

km s?1(ΓB⊙)

NGC821E2173550′′-20.5 2.50.6413-17R+03

NGC3779E1/S0?87735′′-20.00.20.185-8R+03

NGC4494E0123249′′-20.60.30.65-7R+03

NGC4697E3131090′′-20.5 1.40.7412±1Np01

4Astron.Nachr./AN XXX(200X)X