As a result of a systematic NIR H-band (1.65 mum) imaging survey of normal galaxies in the local universe that includes objects both in the Virgo cluster and in the "Great Wall" (including A1367, A1656 as well as the "isolated" population in the bridge between the two clusters), we are able to measure in a highly homogeneous way photometric and structural properties for a sample of 1143 galaxies. We base our analysis on a quantitative structural parameter, the concentration index C-31 (defined as the ratio between the radii that enclose 75% and 25% of the total luminosity), instead of relying on the galaxies' morphological classification. The C-31 parameter provides a model independent, quantitative and continuous characterization of the light distribution within galaxies, and it is thus to be preferred to either the Hubble type or a parameter like the bulge-to-disk or bulge-to-total light ratio. Low C-31 objects are typically found among disk galaxies, while high C-31 describes bulge-dominated systems. We confirm our previous claim that C-31 correlates strongly and non-linearly with the galaxy total luminosity. C-31 > 5 values are found only at L-H > 10(10) L. (giant ellipticals mixed with early-type spirals), while at L-H < 10(10) L. galaxies have C-31 < 3 (dwarf Irregulars mixed with ellipticals). At high luminosity, low C-31 are allowed (bulge-less giant Scs). Thus C-31 and the total luminosity are not sufficient to fully characterize the family of galaxies. However we find that galaxies can be completely described by three parameters, namely: a scale parameter (the H-band luminosity), a shape parameter (the concentration index C-31) and a colour parameter (e.g. the B-H colour). At low luminosity dEs and dIs, having similar C-31, are colour-discriminated, while at very high luminosity different C-31 discriminate S0s from Scs, otherwise undistinguishable on the basis of their colour. A single, monotonic relation exists between luminosity and mu(e) in the H-band, as opposed to the two separate regimes that are generally observed in the B-band. As NIR luminosity traces quite accurately the galaxy mass distribution, this relation re-enforces the indication in favour of a scale-dependent mass collapse mechanism which produces higher surface-brightness and more centrally peaked galaxies with increasing mass. However, the presence of high-luminosity low-C-31 galaxies hints at other machanisms and physical properties (such as angular momentum) playing an important role in galaxy formation.

Scodeggio, M., Gavazzi, G., Franzetti, P., Boselli, A., Zibetti, S., Pierini, D. (2002). 1.65 mu m (H-band) surface photometry of galaxies - IX. Photometric and structural properties of galaxies. ASTRONOMY & ASTROPHYSICS, 384(3), 812-825 [10.1051/0004-6361:20020110].

1.65 mu m (H-band) surface photometry of galaxies - IX. Photometric and structural properties of galaxies

GAVAZZI, GIUSEPPE;
2002

Abstract

As a result of a systematic NIR H-band (1.65 mum) imaging survey of normal galaxies in the local universe that includes objects both in the Virgo cluster and in the "Great Wall" (including A1367, A1656 as well as the "isolated" population in the bridge between the two clusters), we are able to measure in a highly homogeneous way photometric and structural properties for a sample of 1143 galaxies. We base our analysis on a quantitative structural parameter, the concentration index C-31 (defined as the ratio between the radii that enclose 75% and 25% of the total luminosity), instead of relying on the galaxies' morphological classification. The C-31 parameter provides a model independent, quantitative and continuous characterization of the light distribution within galaxies, and it is thus to be preferred to either the Hubble type or a parameter like the bulge-to-disk or bulge-to-total light ratio. Low C-31 objects are typically found among disk galaxies, while high C-31 describes bulge-dominated systems. We confirm our previous claim that C-31 correlates strongly and non-linearly with the galaxy total luminosity. C-31 > 5 values are found only at L-H > 10(10) L. (giant ellipticals mixed with early-type spirals), while at L-H < 10(10) L. galaxies have C-31 < 3 (dwarf Irregulars mixed with ellipticals). At high luminosity, low C-31 are allowed (bulge-less giant Scs). Thus C-31 and the total luminosity are not sufficient to fully characterize the family of galaxies. However we find that galaxies can be completely described by three parameters, namely: a scale parameter (the H-band luminosity), a shape parameter (the concentration index C-31) and a colour parameter (e.g. the B-H colour). At low luminosity dEs and dIs, having similar C-31, are colour-discriminated, while at very high luminosity different C-31 discriminate S0s from Scs, otherwise undistinguishable on the basis of their colour. A single, monotonic relation exists between luminosity and mu(e) in the H-band, as opposed to the two separate regimes that are generally observed in the B-band. As NIR luminosity traces quite accurately the galaxy mass distribution, this relation re-enforces the indication in favour of a scale-dependent mass collapse mechanism which produces higher surface-brightness and more centrally peaked galaxies with increasing mass. However, the presence of high-luminosity low-C-31 galaxies hints at other machanisms and physical properties (such as angular momentum) playing an important role in galaxy formation.
Articolo in rivista - Articolo scientifico
Galaxies; fundamental parameters; galaxies; photometry; infrared; galaxies
English
2002
384
3
812
825
none
Scodeggio, M., Gavazzi, G., Franzetti, P., Boselli, A., Zibetti, S., Pierini, D. (2002). 1.65 mu m (H-band) surface photometry of galaxies - IX. Photometric and structural properties of galaxies. ASTRONOMY & ASTROPHYSICS, 384(3), 812-825 [10.1051/0004-6361:20020110].
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/10281/22503
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