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Astron. Astrophys. 339, 409-422 (1998)

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Near-infrared surface photometry of early-type spiral galaxies

II. M/L ratios and dark halos *

G. Moriondo 1, C. Giovanardi 2 and L.K. Hunt 3

1 Dipartimento di Astronomia e Scienza dello spazio, L.E. Fermi 5, I-50125 Firenze, Italy
2 Osservatorio Astrofisico di Arcetri, L.E. Fermi 5, I-50125 Firenze, Italy
3 C.A.I.S.M.I., L.E. Fermi 5, I-50125 Firenze, Italy

Received 14 July 1997 / Accepted 10 February 1998

Abstract

We present mass distributions obtained from near-infrared (NIR) surface brightness decompositions and rotation curve fitting of a sample of early-type spiral galaxies. Bulge and disk mass-to-light (M/L) ratios, dark halo parameters, and the modified Newtonian dynamics (MOND) acceleration parameter are derived. We find that the mean disk NIR M/L is higher than that of the bulge, and comparison with stellar population synthesis models implies that early-type spiral bulges are, on average, younger and more metal rich than disks. NIR disk M/L is found to depend on disk luminosity, consistently with previously reported trends in ellipticals and spirals, and with cold dark matter models for disk formation. Within the optical radius, the mean ratio of stellar to dark matter is 2 and the typical dark halo mass is 1011 [FORMULA]. The value of the MOND acceleration parameter that best accommodates the sample as a whole is [FORMULA] cm s-2.

Key words: galaxies: fundamental parameters – galaxies: kinematics and dynamics – galaxies: spiral – galaxies: stellar content – galaxies: structure

* Based on observations taken at TIRGO (Gornergrat, Switzerland). TIRGO is operated by CAISMI-CNR, Arcetri, Firenze, Italy

Send offprint requests to: G. Moriondo

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© European Southern Observatory (ESO) 1998

Online publication: October 21, 1998
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