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Date and Time of the Query: 2019-08-18 T02:49:35 PDT
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For refcode 2001MNRAS.326.1517D:
Retrieve 73 NED objects in this reference.
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NED Abstract

Copyright by Royal Astronomical Society. 2001MNRAS.326.1517D 2D modelling of the light distribution of early-type galaxies in a volume-limited sample - II. Results for real galaxies M. D'Onofrio Accepted 2001 May 23. Received 2001 April 18; in original form 2001 February 21 ABSTRACT In this paper we analyse the results of the two-dimensional (2D) fit of the light distribution of 73 early-type galaxies belonging to the Virgo and Fornax clusters, a sample volume- and magnitude-limited down to M_B_ = -17.3, and highly homogeneous. In our previous paper (Paper I) we have presented the adopted 2D models of the surface-brightness distribution - namely the r^1/n^ and (r^1/n^ + exp) models - we have discussed the main sources of error affecting the structural parameters, and we have tested the ability of the chosen minimization algorithm (MINUIT) in determining the fitting parameters using a sample of artificial galaxies. We show that, with the exception of 11 low-luminosity E galaxies, the best fit of the real galaxy sample is always achieved with the two-component (r^1/n^ + exp) model. The improvement in the {chi}^2^ due to the addition of the exponential component is found to be statistically significant. The best fit is obtained with the exponent n of the generalized r^1/n^ Sersic law different from the classical de Vaucouleurs value of 4. Nearly 42 per cent of the sample have n < 2, suggesting the presence of exponential 'bulges' also in early-type galaxies. 20 luminous E galaxies are fitted by the two-component model, with a small central exponential structure ('disc') and an outer big spheroid with n > 4. We believe that this is probably due to their resolved core. The resulting scalelengths R_h_ and R_e_ of each component peak approximately at ~1 and ~2 kpc, respectively, although with different variances in their distributions. The ratio R_e_/R_h_ peaks at ~0.5, a value typical for normal lenticular galaxies. The first component, represented by the r^1/n^ law, is probably made of two distinct families, 'ordinary' and 'bright', on the basis of their distribution in the {mu}_e_-log(R_e_) plane, a result already suggested by Capaccioli, Caon and D'Onofrio. The bulges of spirals and S0 galaxies belong to the 'ordinary' family, while the large spheroids of luminous E galaxies form the 'bright' family. The second component, represented by the exponential law, also shows a wide distribution in the {mu}_0_^c^-log(R_h_) plane. Small discs (or cores) have short scalelengths and high central surface brightness, while normal lenticulars and spiral galaxies generally have scalelengths higher than 0.5 kpc and central surface brightness brighter than 20 mag arcsec^-2^ (in the B band). The scalelengths R_e_ and R_h_ of the 'bulge' and 'disc' components are probably correlated, indicating that a self-regulating mechanism of galaxy formation may be at work. Alternatively, two regions of the R_e_-R_h_ plane are avoided by galaxies due to dynamical instability effects. The bulge-to-disc (B/D) ratio seems to vary uniformly along the Hubble sequence, going from late-type spirals to E galaxies. At the end of the sequence the ratio between the large spheroidal component and the small inner core can reach B/D ~ 100. Keywords: galaxies: elliptical and lenticular, cD - galaxies: fundamental parameters - galaxies: photometry - galaxies: structure.
Retrieve 73 NED objects in this reference.
Please click here for ADS abstract

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