m (H -band) surface photometry of galaxies - VII. Dwarf galaxies in the Virgo Cluster

Free access article

Issue		A&A Volume 372, Number 1, June II 2001


Page(s)		29 - 49
Section		Extragalactic astronomy
DOI		http://dx.doi.org/10.1051/0004-6361:20010439

A&A 372, 29-49 (2001)
DOI: 10.1051/0004-6361:20010439

$\mathsf{1.65 \mu}$ m (H -band) surface photometry of galaxies

VII. Dwarf galaxies in the Virgo Cluster

G. Gavazzi¹, S. Zibetti¹, A. Boselli², P. Franzetti¹, M. Scodeggio³ and S. Martocchi¹

¹ Università degli Studi di Milano-Bicocca, P.zza dell'Ateneo Nuovo 1, 20126 Milano, Italy
² Institut d'Astrophysique de Marseille, Traverse du Siphon, 13376 Marseille Cedex 12, France
³ Istituto di Fisica Cosmica "G. Occhialini", CNR, via Bassini 15, 20133 Milano, Italy

(Received 21 December 2000 / Accepted 21 March 2001)

Abstract
We present near-infrared H-band (1.65 $\mu$ m ) observations and surface brightness profile decompositions for 75 faint ( $13.5 \lesssim m_{\rm p} \lesssim 18.5$ ) galaxies, primarily taken among dwarf Ellipticals members of the Virgo cluster, with some Centaurus Cluster members, a BCD and two peculiar galaxies taken as fillers. We model their surface brightness profiles with a de Vaucouleurs (D), exponential (E), mixed (bulge+disk or M) or truncated (T) law, and we derive for each galaxy the H band effective surface brightness ( $\mu_{\rm e}$ ) and effective radius ( $r_{\rm e}$ ), the asymptotic total magnitude $H_{\rm T}$ and the light concentration index C₃₁, defined as the ratio between the radii that enclose 75% and 25% of the total light $H_{\rm T}$ . For a subsample we compare the NIR surface photometry with similar data taken in the B and V bands, and we give the B-H and B-V color profiles. Combining the present data with those previously obtained by our group (1157 objects) we analyze the NIR properties of a nearly complete sample, representative of galaxies of all morphological types, spanning 4 decades in luminosity. We confirm our earlier claim that the presence of cusps and extended haloes in the light profiles ( C₃₁> 5) is a strong, non-linear function of the total luminosity. We also find that: i) among dE and dS0 galaxies D profiles are absent; 50% of the decompositions are of type M, the remaining being of type E or T. ii) Less than 50% of the giant elliptical galaxies have pure D profiles, the majority being represented by M profiles. iii) Most giant galaxies (from elliptical to Sb) have M profiles. iv) Most of late type spirals (Scd to BCD) have either E or T profiles. v) The type of decomposition is a strong function of the total H band luminosity, independent of the Hubble classification: the fraction of type E decompositions decreases with increasing luminosity, while those of type M increase with luminosity. Pure D profiles are absent in the low luminosity range $L_{\rm H}< 10^{10}$ $L_\odot$ and become dominant above 10¹¹ $L_\odot$ , while T profiles are present only among low luminosity galaxies. vi) We find that dE-peculiar galaxies have structural parameters indistinguishable from those of late-type dwarfs, thus they might represent the missing link between dEs and dIs.

Key words: galaxies: fundamental parameters -- galaxies: photometry -- infrared: galaxies

Offprint request: G. Gavazzi, Giuseppe.Gavazzi@mib.infn.it

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