Up: Near-infrared observations of galaxies
We have presented the results of a programme of NIR
imaging of disk galaxies in the Pisces-Perseus supercluster area,
and
.This programme constitutes the first large NIR imaging survey of the
supercluster and complements previous similar surveys in the Coma and
Virgo areas.
The present paper is the first of a series and contains images
in the H passband of a composite sample of 174 galaxies.
- 1.
- The sample galaxies,
a subset of the PP supercluster galaxies, are mainly late spirals with a median
.The sample starts
lacking completeness at
,and extends up to
.
- 2.
- For each galaxy we present a grey-scale image reaching an isophote of
-mag arcsec-2. For each image we supply
the elliptically-averaged radial profile of the surface brightness, the
ellipticity, and the position angle of the isophotes.
- 3.
- We derive a total magnitude
, an isophotal magnitude
H21.5, an effective diameter
, an isophotal one D21.5,
the concentration index C31, and estimate the ellipticity
and the position angle PA of the outer disk. These data,
together with basic information regarding the sample objects and their
observation, are collected in a single table which is available in electronic
form at the CDS.
Radial profiles in tabular form and
images FITS files are also available upon request.
- 4.
- The trends of
with H21.5 and
imply that the average outer disk has an isophotal
radius
and a central surface brightness
H-mag arcsec-2.
- 5.
- The empirical relation in our sample, D21.5 = 0.89 D25, implies
that the B-H color of the outer disk is bluer, on average, than 3.5,
in agreement with de Jong (1996). The ratio D21.5/D25 depends,
although weakly, on the total galaxy B-H, and consequently on
its absolute magnitude.
- 6.
- We confirm the dependence of the (model independent)
concentration index C31 on luminosity and, to a lesser degree, on
morphological type. Large values for C31, that is values in excess
of what is expected for pure disks (
),
are preferentially observed in galaxies
brighter than
and
.
- 7.
- Even in the NIR,
objective estimates of outer ellipticities and position angles can
often be contaminated by the geometry of bars and spiral patterns;
the effect is strongest for shallow images,
and for low inclinations.
Their impact on the measurement of global
photometric properties is, in any case, not dramatic.
It virtually
affects only D21.5, with discrepancies exceeding 10%
only in the two worst cases.
Acknowledgements
G.M. warmly acknowledges the hospitality of
the Astronomy Dept. of Cornell University, where part of the data reduction
was done. We acknowledge the partial support of the Italian
Space Agency (ASI) through the grant ARS-98-116/22.
Up: Near-infrared observations of galaxies
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