Issue |
Astron. Astrophys. Suppl. Ser.
Volume 129, Number 3, May I 1998
|
|
---|---|---|
Page(s) | 583 - 591 | |
DOI | https://doi.org/10.1051/aas:1998206 | |
Published online | 15 May 1998 |
Surface photometry of early–type galaxies in the Hubble deep field *
1
Astronomical Observatory of Padova, Vicolo dell' Osservatorio 5, 35122 Padova, Italy
2
Department of Astronomy of the Padova University, Vicolo dell' Osservatorio 5, 35122 Padova, Italy e-mail: gfasano@leda.pd.astro.it
Send offprint request to: G. Fasano
Received:
16
September
1997
Accepted:
5
November
1997
The detailed surface photometry of a sample of early–type galaxies in
the Hubble Deep Field is presented as part of a long–term project
aimed to settle strong observational constraints to the theories
modelling the evolution of elliptical galaxies from the early stages.
The sample has been extracted, in the V606 band, from the
database provided by the ESO-STECF-HDF Group (Couch 1996). The selection criteria involve the total magnitude, the number
of pixels detected above the background level and an automatic
star/galaxy classifier. Moreover, form visual inspection of the
frames, we excluded the galaxies showing unambiguous late–type
morphology. The analysis of the luminosity and geometrical profiles,
carried out on the 162 candidates obeying our selection criteria,
resulted in a list of 99 "bona fide” early–type galaxies, for
which accurate total magnitudes and effective radii were computed on
the basis of the equivalent luminosity profiles. The comparison with
the magnitudes given by Williams et al. (1996) indicates that the
automated photometry tends to underestimate the total luminosity of the
ellipticals.
The luminosity profiles of most of galaxies in our sample follow
fairly well the de Vaucouleurs law ("Normal” profiles). However,
a relevant fraction of galaxies, even following the law in
the main body light distribution, exhibit in the inner region a
flattening of the luminosity profile not attributable to the PSF
("Flat” profiles) or, in some cases, a complex (multi–nucleus)
structure ("Merger” profiles). A statistically significant
correlation is found between the shapes of the luminosity profiles and
the ellipticity distribution. In particular, the average ellipticity
of galaxies belonging to the "Flat” and "Merger” classes
is significantly higher than that of the "Normal” galaxies.
Finally, even taken into account the relevant uncertainty of the outer
position angle profiles, the amount of isophotal twisting of HDF
ellipticals turns out to be significantly larger with respect to that
of the local samples.
Key words: galaxies: elliptical and lenticular / galaxies: fundamental parameters / galaxies: photometry
© European Southern Observatory (ESO), 1998