Astron. Astrophys. Suppl. Ser. 134, 437-451

Structure and kinematics of the peculiar galaxy NGC 128

M. D'Onofrio ¹ - M. Capaccioli ^2,3 - P. Merluzzi ² - S. Zaggia ² - J. Boulesteix ⁴

Send offprint request: M. D'Onofrio

1 - Dipartimento di Astronomia, Università di Padova, vicolo dell'Osservatorio 5, I-35122 Padova, Italy
2 - Osservatorio Astronomico di Capodimonte, via Moiariello 16, I-80131 Napoli, Italy
3 - Dipartimento di Scienze Fisiche, Università di Napoli, Mostra d'Oltremare, Padiglione 19, I-80125 Napoli, Italy
4 - Observatoire de Marseille, 2 place Le Verrier, F-13248 Marseille Cedex 04, France

Received February 13; accepted August 31, 1998

Abstract:

This is a multiband photometric and spectroscopic study of the peculiar S0 galaxy NGC 128. We present results from broad (B and R) and narrow (H$\alpha$) band optical CCD photometry, near (NIR) and far (FIR) infrared observations, long slit spectroscopy, and Fabry-Perot interferometry (CIGALE).

The peculiar peanut shape morphology of the galaxy is observed both at optical and near-infrared wavelengths. The stellar disk is thick and distorted (arc-bended), with a color asymmetry along the major axis due to the presence of a large amount of dust, estimated through NIR and FIR data of $\sim 6\ 10^6\ M_{\hbox{$\odot$}}$,in the region of interaction with the companion galaxy NGC 127.

The color maps are nearly uniform over the whole galaxy, but for the major axis asymmetry, and a small gradient toward the center indicating the presence of a redder disk-like component. The H$\alpha$ image indeed reveals the existence of a tilted gaseous "disk'' around the center, oriented with the major axis toward the companion galaxy NGC 127.

Long slit and CIGALE data confirm the presence of gas in a disk-like component counter-rotating and inclined approximately of $50^\circ$ to the line of sight. The mass of the gas disk in the inner region is $\sim 2.7\ 10^4 \ M_{\hbox{$\odot$}}$.

The stellar velocity field is cylindrical up to the last measured points of the derived rotation curves, while the velocity dispersion profiles are typical for an S0 galaxy, but for an extended constant behaviour along the minor axis.

Key words: galaxies: individual: NGC 128 -- galaxies: elliptical and lenticular, cD -- galaxies: photometry -- galaxies: kinematics and dynamics -- galaxies: structure