Our sample of early-type galaxies has been extracted from the second release of the WFPC2-HDF frames, in the V606 band. Due to the efficiency curve of the WFPC2, this filter usually ensures a better S/N ratio with respect to the other available filters (U300, B450 and I814) even in the case of high redshift galaxies, as we verified by comparing the V606 and I814 images.
The sample selection is based on the compilation provided by the
ESO-STECF-HDF Group, obtained through the automated SExtractor
algorithm (Bertin & Arnouts 1996). Among the other things, the
catalog includes, for each object in the field, the total V606
magnitude in the STMAG system, the number of pixels ()
detected above the background using a threshold of
of the
noise, and a star/galaxy (s/g) classifier, ranging from 0 to 1, which
gives the probability that the object is stellar (s/g=1 means
"star''). After a preliminar inspection of the frames, supplemented by
several fast average-tracing luminosity profiles of faint and/or
small objects, we decided to set the following limits for inclusion in
our preliminar sample:
(1)
26.5;
(2)
200;
(3)
0.6.
As for the first two limits, they concern essentially the technical "feasibility'' of the morphological analysis. Although at this stage we preferred not to be too much severe in the selection, these limits provide completeness criteria to our sample. The choice of the third limit turned out not to be critical, probably due to the very shape of the star profiles. Nevertheless, in this case we preferred to be more conservative, in order to prevent the inclusion of stars in our sample.
We found 372 objects of the SExtractor catalog matching the above
limits in the three chips of the WFC (the catalog does not include the
PC). 29 objects from the chip (PC) were added later to
this list by simple visual inspection, so that the total preliminar
sample turned out to be of 401 objects.
We used the "imexam'' IRAF's tool, together with the " Saoimage'' display facility, to estimate the morphological type of each object, thus producing a first screening of the galaxies in the sample. Apart from some cases, the angular resolution did not allow us to give precise Hubble types. Moreover, many faint galaxies appear heavily disturbed by the presence of close (often multiple) companions or peculiar structures, which obviously make even more difficult the classification. Nevertheless, most of the "early-type'' candidates turned out to be easily recognizable on the basis of the light concentration. The doubious cases (mainly S0s and Sa galaxies) were retained at this stage and were examined later in a quantitative way (see next section).
After this selection we were left with 134 galaxies. In order to check
the reliability of our
classifications, we compared them with those given by
Van den Bergh et al. (1996) and by Statler (1996, private communication). Due to
the different selection criteria, the three samples do not overlap
exactly each other. Nevertheless, for the common objects the agreement
was fairly good ( with Van den Bergh et al. and
with Statler).
To be more
accurate, we decided to provisionally include in our sample all galaxies
matching our selection criteria which, contrary to our estimates, were
classified as "early-type'' by Van den Bergh et al. (1996)
and/or
by Statler (1996). In this way 28 more galaxies enriched our sample, which
become of 162 objects.
We performed the detailed surface photometry of this sample, producing luminosity and geometrical profiles of each object. The next Section outlines the techniques we used to extract the morphological information from this very peculiar observational material. From the analysis of the luminosity and geometrical profiles, 34 objects of the sample have been recognized to be " disk-dominated'' objects (likely Sa galaxies), whereas 28 more objects showed peculiar or unclassifiable profiles. These galaxies were excluded from the final sample of "bona fide'' early-type galaxies.
The final sample of 99 galaxies is reported
in Table 1 (click here), where Col. (1) gives the FOCAS list identification
(Williams et al. 1996), Cols. (2) and (3) the J2000 coordinates
and
, Col. (4) our morphological classification,
Cols. (5) the morphological type (if available) given by
van den Bergh et al. (1996).
FOCAS-ID | Coordinates (2000) | Morphology | Lum.Prof. | ![]() | ![]() | ![]() | ![]() | ![]() | ||
![]() | ![]() | Our | V.d.Bergh | class | (STMAG) | (![]() | (![]() | |||
ID_4_942_0 | ![]() | ![]() | E | E | 1 | 24.75(.33) | 0.54 | 0.18 | 0.25 | 15 |
ID_4_926_2 | ![]() | ![]() | m | p | 3 | 25.36(.17) | 0.19 | 0.04 | 0.17 | 60 |
ID_4_928_1 | ![]() | ![]() | S0 | E | 1 | 23.61(.15) | 0.36 | 0.10 | 0.19 | 50 |
ID_4_878_2 | ![]() | ![]() | E | E | 2 | 25.79(.19) | 0.22 | 0.35 | 0.35 | 8 |
ID_4_878_11 | ![]() | ![]() | E | Sap | 2 | 23.66(.14) | 0.22 | 0.12 | 0.14 | 30 |
ID_4_822_0 | ![]() | ![]() | E | E | 1 | 25.42(.27) | 0.33 | 0.08 | 0.10 | 5 |
ID_4_858_13 | ![]() | ![]() | E | E | 1 | 25.18(.23) | 0.15 | 0.14 | 0.19 | 11 |
ID_4_767_0 | ![]() | ![]() | S0 | E | 2 | 25.16(.15) | 0.19 | 0.36 | 0.39 | 6 |
ID_4_661_1 | ![]() | ![]() | E | E | 2 | 24.96(.17) | 0.22 | 0.18 | 0.23 | 20 |
ID_4_639_1 | ![]() | ![]() | E | Et? | 1 | 25.12(.14) | 0.17 | 0.08 | 0.16 | 47 |
ID_4_937_0 | ![]() | ![]() | E | E | 1 | 25.50(.19) | 0.18 | 0.19 | 0.22 | 30 |
ID_1_95_0 | ![]() | ![]() | E | - | 1 | 25.03(.13) | 0.13 | 0.28 | 0.30 | 12 |
ID_4_602_0 | ![]() | ![]() | E | E | 1 | 25.30(.18) | 0.16 | 0.24 | 0.28 | 15 |
ID_4_804_0 | ![]() | ![]() | E | Ep? | 1 | 25.40(.16) | 0.20 | 0.23 | 0.27 | 8 |
ID_4_774_3 | ![]() | ![]() | E | - | 1 | 25.95(.18) | 0.14 | 0.20 | 0.21 | 26 |
ID_4_581_11 | ![]() | ![]() | E/S0 | - | 1 | 25.77(.15) | 0.14 | 0.19 | 0.25 | 40 |
ID_4_845_0 | ![]() | ![]() | E | Sa | 2 | 25.08(.16) | 0.20 | 0.37 | 0.37 | 3 |
ID_4_554_1 | ![]() | ![]() | Ep | Ep | 2 | 25.58(.20) | 0.17 | 0.29 | 0.33 | 38 |
ID_4_493_0 | ![]() | ![]() | S0 | E | 1 | 23.26(.24) | 0.44 | 0.33 | 0.33 | 7 |
ID_4_727_0 | ![]() | ![]() | E | Ep? | 2 | 23.43(.10) | 0.21 | 0.49 | 0.48 | 3 |
ID_4_565_0 | ![]() | ![]() | m | Sap | 3 | 23.46(.12) | 0.31 | 0.18 | 0.28 | 65 |
ID_4_744_0 | ![]() | ![]() | E | - | 1 | 22.33(.18) | 0.63 | 0.12 | 0.16 | 50 |
ID_2_82_1 | ![]() | ![]() | E | E/m | 2 | 24.92(.15) | 0.18 | 0.27 | 0.28 | 19 |
ID_4_752_1 | ![]() | ![]() | E | - | 1 | 22.97(.22) | 0.90 | 0.18 | 0.18 | 3 |
ID_1_56_0 | ![]() | ![]() | E | - | 1 | 26.38(.19) | 0.13 | 0.15 | 0.21 | 7 |
ID_4_579_0 | ![]() | ![]() | E | E/* | 1 | 25.53(.14) | 0.13 | 0.06 | 0.09 | 93 |
ID_1_37_1 | ![]() | ![]() | m | - | 3 | 25.75(.18) | 0.13 | 0.50 | 0.46 | 28 |
ID_2_163_0 | ![]() | ![]() | E | - | 1 | 25.94(.19) | 0.18 | 0.25 | 0.26 | 15 |
ID_4_555_2 | ![]() | ![]() | E/S0 | E | 1 | 24.79(.21) | 0.32 | 0.17 | 0.24 | 20 |
ID_4_368_0 | ![]() | ![]() | E/S0 | - | 1 | 26.07(.22) | 0.24 | 0.26 | 0.25 | 25 |
ID_2_80_0 | ![]() | ![]() | E | - | 2 | 25.64(.18) | 0.18 | 0.26 | 0.28 | 8 |
ID_1_100_0 | ![]() | ![]() | E | - | 1 | 26.37(.14) | 0.13 | 0.12 | 0.29 | 22 |
ID_1_35_0 | ![]() | ![]() | E | - | 1 | 24.35(.16) | 0.21 | 0.24 | 0.26 | 14 |
ID_4_516_0 | ![]() | ![]() | E | Et | 1 | 25.30(.15) | 0.18 | 0.13 | 0.20 | 40 |
ID_4_497_0 | ![]() | ![]() | E | - | 1 | 26.05(.17) | 0.13 | 0.12 | 0.14 | 20 |
ID_4_520_0 | ![]() | ![]() | E/S0 | - | 1 | 26.07(.19) | 0.14 | 0.11 | 0.18 | 15 |
ID_2_61_0 | ![]() | ![]() | E | E | 2 | 25.91(.15) | 0.15 | 0.26 | 0.31 | 10 |
ID_4_254_0 | ![]() | ![]() | E | E/* | 1 | 23.64(.19) | 0.55 | 0.27 | 0.17 | 45 |
ID_1_47_0 | ![]() | ![]() | E | - | 2 | 25.17(.13) | 0.15 | 0.38 | 0.37 | 16 |
ID_4_322_2 | ![]() | ![]() | E | Et | 2 | 25.59(.16) | 0.16 | 0.23 | 0.28 | 5 |
ID_2_251_0 | ![]() | ![]() | E/S0 | - | 1 | 22.96(.17) | 0.52 | 0.05 | 0.14 | 110 |
ID_4_471_0 | ![]() | ![]() | E | E | 1 | 23.11(.07) | 0.22 | 0.08 | 0.12 | 45 |
ID_4_289_0 | ![]() | ![]() | E | E | 1 | 25.73(.14) | 0.16 | 0.11 | 0.20 | 49 |
ID_2_201_0 | ![]() | ![]() | E | Et | 1 | 24.45(.16) | 0.14 | 0.15 | 0.24 | 15 |
ID_2_272_0 | ![]() | ![]() | E | - | 2 | 25.98(.16) | 0.17 | 0.26 | 0.28 | 34 |
ID_2_363_0 | ![]() | ![]() | E | - | 2 | 25.94(.15) | 0.15 | 0.25 | 0.33 | 17 |
ID_2_121_111 | ![]() | ![]() | S0 | - | 1 | 21.48(.11) | 0.60 | 0.04 | 0.23 | 30 |
ID_2_412_11 | ![]() | ![]() | E/S0 | Sap | 1 | 25.42(.22) | 0.17 | 0.27 | 0.42 | 7 |
ID_4_260_112 | ![]() | ![]() | E | E | 2 | 25.08(.13) | 0.18 | 0.30 | 0.28 | 13 |
ID_2_449_1 | ![]() | ![]() | E | E | 2 | 24.11(.22) | 0.22 | 0.24 | 0.30 | 15 |
ID_2_173_0 | ![]() | ![]() | E | E | 2 | 23.74(.29) | 0.72 | 0.18 | 0.35 | 8 |
ID_2_537_12 | ![]() | ![]() | E | Et | 2 | 25.60(.15) | 0.20 | 0.32 | 0.35 | 12 |
ID_3_51_0 | ![]() | ![]() | E | E/* | 1 | 25.93(.17) | 0.17 | 0.08 | 0.14 | 5 |
ID_2_236_2 | ![]() | ![]() | E | Et | 1 | 24.81(.10) | 0.16 | 0.03 | 0.13 | 65 |
ID_2_180_0 | ![]() | ![]() | E | Sa | 2 | 24.65(.15) | 0.20 | 0.50 | 0.47 | 4 |
ID_4_274_0 | ![]() | ![]() | S0 | - | 2 | 26.02(.25) | 0.17 | 0.23 | 0.24 | 10 |
ID_2_264_2 | ![]() | ![]() | E | E | 1 | 22.80(.11) | 0.21 | 0.24 | 0.26 | 30 |
ID_2_456_1111 | ![]() | ![]() | S0 | - | 1 | 18.93(.05) | 0.52 | 0.37 | 0.39 | 7 |
ID_3_229_0 | ![]() | ![]() | E | E/* | 2 | 24.96(.24) | 0.24 | 0.10 | 0.12 | 15 |
ID_2_590_1 | ![]() | ![]() | E | - | 2 | 25.89(.21) | 0.16 | 0.18 | 0.16 | 55 |
ID_4_109_0 | ![]() | ![]() | E | p | 2 | 25.29(.12) | 0.16 | 0.38 | 0.40 | 10 |
ID_3_143_0 | ![]() | ![]() | m | Sap | 3 | 22.85(.15) | 0.32 | 0.55 | 0.65 | 4 |
FOCAS-ID | Coordinates (2000) | Morphology | Lum.Prof. | ![]() | ![]() | ![]() | ![]() | ![]() | ||
![]() | ![]() | Our | V.d.Bergh | class | (STMAG) | (![]() | (![]() | |||
ID_3_243_0 | ![]() | ![]() | E/S0p | Ep | 1 | 25.52(.21) | 0.21 | 0.32 | 0.34 | 14 |
ID_2_456_22 | ![]() | ![]() | S0 | Ep | 1 | 25.15(.12) | 0.17 | 0.36 | 0.50 | 6 |
ID_3_321_1 | ![]() | ![]() | S0 | - | 1 | 23.05(.13) | 0.43 | 0.34 | 0.36 | 5 |
ID_2_373_0 | ![]() | ![]() | E | E | 1 | 25.58(.18) | 0.16 | 0.27 | 0.33 | 9 |
ID_2_725_0 | ![]() | ![]() | E | E | 2 | 25.50(.15) | 0.17 | 0.52 | 0.44 | 12 |
ID_2_693_1 | ![]() | ![]() | E | E | 2 | 25.22(.15) | 0.18 | 0.18 | 0.25 | 22 |
ID_3_659_2 | ![]() | ![]() | Ep | E/S0 | 1 | 25.69(.15) | 0.13 | 0.18 | 0.17 | 23 |
ID_3_902_1 | ![]() | ![]() | E/Sa | - | 2 | 26.25(.22) | 0.16 | 0.18 | 0.20 | 42 |
ID_2_531_0 | ![]() | ![]() | E | E | 3 | 24.06(.15) | 0.29 | 0.10 | 0.07 | 15 |
ID_3_586_0 | ![]() | ![]() | E | E/Sa | 1 | 25.77(.36) | 0.36 | 0.14 | 0.19 | 20 |
ID_2_646_0 | ![]() | ![]() | E | E | 2 | 25.14(.21) | 0.20 | 0.42 | 0.38 | 5 |
ID_2_849_0 | ![]() | ![]() | E | Ep | 2 | 25.60(.26) | 0.19 | 0.32 | 0.30 | 15 |
ID_3_625_0 | ![]() | ![]() | m | p | 3 | 25.39(.13) | 0.15 | 0.50 | 0.49 | 3 |
ID_3_696_0 | ![]() | ![]() | E | E | 2 | 23.77(.09) | 0.19 | 0.46 | 0.45 | 10 |
ID_2_637_0 | ![]() | ![]() | E | E/* | 1 | 25.18(.15) | 0.18 | 0.11 | 0.14 | 80 |
ID_3_886_0 | ![]() | ![]() | E | E | 2 | 25.21(.18) | 0.14 | 0.16 | 0.21 | 8 |
ID_2_726_1 | ![]() | ![]() | E | - | 1 | 26.75(.19) | 0.11 | 0.23 | 0.18 | 35 |
ID_2_635_0 | ![]() | ![]() | E | - | 1 | 25.99(.15) | 0.17 | 0.24 | 0.24 | 29 |
ID_2_591_2 | ![]() | ![]() | E | - | 2 | 25.05(.15) | 0.18 | 0.31 | 0.30 | 10 |
ID_3_670_1 | ![]() | ![]() | E | E | 2 | 25.73(.21) | 0.14 | 0.28 | 0.26 | 20 |
ID_2_643_0 | ![]() | ![]() | m | E+E | 3 | 25.03(.17) | 0.22 | 0.65 | 0.62 | 5 |
ID_2_973_2 | ![]() | ![]() | E | - | 2 | 25.88(.18) | 0.18 | 0.23 | 0.19 | 10 |
ID_3_118_1 | ![]() | ![]() | E | E/* | 1 | 24.59(.17) | 0.14 | 0.08 | 0.09 | 10 |
ID_2_898_0 | ![]() | ![]() | m | Sa | 3 | 25.14(.20) | 0.27 | 0.49 | 0.50 | 3 |
ID_3_743_0 | ![]() | ![]() | E | - | 2 | 25.61(.20) | 0.19 | 0.11 | 0.14 | 93 |
ID_3_266_0 | ![]() | ![]() | E | E | 1 | 25.19(.19) | 0.22 | 0.30 | 0.31 | 3 |
ID_3_180_1 | ![]() | ![]() | E/S0 | E | 1 | 23.94(.21) | 0.51 | 0.18 | 0.19 | 70 |
ID_2_966_0 | ![]() | ![]() | E | E | 2 | 25.83(.19) | 0.18 | 0.24 | 0.24 | 40 |
ID_3_904_0 | ![]() | ![]() | E | E | 1 | 25.11(.13) | 0.17 | 0.08 | 0.14 | 70 |
ID_3_815_1 | ![]() | ![]() | E/S0 | E | 1 | 24.29(.20) | 0.41 | 0.21 | 0.22 | 11 |
ID_3_355_0 | ![]() | ![]() | E | E | 1 | 24.16(.20) | 0.39 | 0.04 | 0.08 | 5 |
ID_3_726_0 | ![]() | ![]() | E | - | 2 | 26.15(.18) | 0.18 | 0.29 | 0.28 | 12 |
ID_3_363_1 | ![]() | ![]() | E | - | 1 | 26.23(.20) | 0.11 | 0.05 | 0.04 | 5 |
ID_3_813_0 | ![]() | ![]() | E | - | 1 | 26.02(.18) | 0.17 | 0.04 | 0.08 | 135 |
ID_3_748_0 | ![]() | ![]() | E | - | 1 | 26.23(.17) | 0.15 | 0.23 | 0.20 | 16 |
ID_3_888_1 | ![]() | ![]() | E | Sap | 1 | 25.57(.18) | 0.17 | 0.12 | 0.18 | 42 |
ID_3_790_1 | ![]() | ![]() | E | - | 1 | 22.60(.14) | 0.40 | 0.10 | 0.13 | 20 |
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